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XXI Симпозиум по геохимии изотопов имени А.П.Виноградова

Журнальные статьи

Albalat E., Telouk P., Albarede F. Er and Yb isotope fractionation in planetary materials // Earth Planet. Sci. Lett. 2012. Vol. 355. P. 39–50.

Terrestrial planets are depleted in volatile elements relative to solar abundances. Little is known, however, about volatility at the high temperatures relevant to asteroidal collisions and to the giant lunar impact. Although refractory rare-earth elements have overall similar crystallochemical properties, some differ in their temperatures of condensation from the nebular gas. This is the case for Yb, which condenses at similar to 1490 K and in the vapor is mostly in elemental form. By contrast, Er, largely present as ErO, condenses at similar to 1660 K. We analyzed the Er and Yb isotopic compositions in 33 terrestrial basalts, garnets, different classes of chondrites and achondrites, and lunar samples by MC-ICP-MS. The range of mass-dependent isotope fractionation is larger for Yb (0.43 parts per thousand per amu) than Er (0.23 parts per thousand) isotopes. For terrestrial rocks, a positive correlation between (delta Yb and La/Yb suggests that the isotopic differences between Er and Yb can be accounted for by the presence of small fractions of Yb2+. Yb is isotopically heavy in kimberlite and light in garnets. Ytterbium behaves similarly to Fe, with Yb3+ being more incompatible than the much less abundant Yb2+. In addition, the coexistence of divalent and trivalent sites in the garnet structure and the preference of heavy isotopes for stable bonds makes Yb in garnet isotopically light. The deficit of heavy Yb isotopes in lunar basaltic samples relative to the Earth, chondrites, and eucrites provides new evidence that the Moon formed by the condensation of silicate vapor in the aftermath of the giant lunar impact. Separation of vapor from melt and of heavy from light isotopes is first expected during the adiabatic expansion of the initial vapor plume. Subsequently, friction between melt and gas tends to further enrich the Moon feeding zone in silicate vapor to compensate the inward migration of melt out of the pre-lunar disk. A major consequence of interpreting the present lunar data by vapor/melt segregation is that the relative abundances of refractory elements in the Moon are unlikely to be chondrite-like or even Earth-like. Erbium isotope ratios in lunar samples reflect the capture of neutrons produced by galactic cosmic rays. The first resonance of Er-167 for neutron capture will help cover an energy range poorly covered by other nuclides.

Aldanmaz E. et al. Source components and magmatic processes in the genesis of Miocene to Quaternary lavas in western Turkey: constraints from HSE distribution and Hf-Pb-Os isotopes // Contrib. Mineral. Petrol. 2015. Vol. 170, № 2. P. 23.

Hf-Pb-Os isotope compositions and highly siderophile element (HSE) abundance variations are used to evaluate the mantle source characteristics and possible effects of differentiation processes in lavas from western Turkey, where the eruption of Late Miocene to Quaternary OIB-type intraplate mafic alkaline lavas followed pre-Middle Miocene convergent margin-type volcanism. Concentrations of Os, Ir, and Ru (IPGE) in the OIB-type intraplate lavas decrease with fractionation for primitive melts (MgO > 10 wt%), suggesting that these elements reside predominantly in olivine and associated HSE retaining trace phases and behave compatibly during olivine-dominated fractionation. Fractional crystallization trends indicate distinctly lower bulk partition coefficients for IPGE in more evolved lavas, possibly reflecting a change in the fractionating assemblages. Pd and Re in the primitive melts display negative correlations with MgO, demonstrating moderately incompatible behavior of these elements during fractionation, while the significantly scattered variation in Pt against MgO may indicate the effects of micronuggets of a Pt-rich alloy. Os-rich alkaline primary lavas (> 50 ppt Os) exhibit a limited range of Os-187/Os-188 (0.1361-0.1404), with some xenolith-bearing lavas displaying depletions in Os-187/Os-188 (0.1131-0.1232), suggesting slight compositional modification of primitive melts through contamination with highly depleted, Os-rich mantle lithosphere. More radiogenic Os isotope ratios (Os-187/Os-188 > 0.1954) in the evolved lavas reflect contamination of the magmas by high(187)Os/Os-188 crustal material during shallow differentiation. The OIB-type lavas show limited variations in Hf and Pb isotopes with Hf-176/Hf-177 = 0.282941-0.283051, Pb-206/Pb-204 = 18.683-19.091, Pb-207/Pb-204 = 15.57915.646, Pb-208/Pb-204 = 38.550-38.993; Hf-176/Hf-177 ratios correlate negatively with Pb-208*/Pb-206*, suggesting the effects of similar mantle processes on the evolution of time-integrated Th/U and Lu/Hf. These lavas have distinctly higher Hf-176/Hf-177 and lower Pb-208*/Pb-206* than the Early-Middle Miocene lavas of the region, which are interpreted as melts of enriched mantle with an overprint by sediment-derived subduction component. The source region for the OIB-type alkaline melts is interpreted to be a sub-lithospheric reservoir enriched in Hf and Pb isotopes with respect to depleted MORB mantle. Combined evaluation of Hf, Pb, and Os isotopes suggests that the relative enrichment in this domain is related to mixing of ancient oceanic crust with the ambient mantle through long-term plate recycling processes.

Amidon W.H., Farley K.A. Cosmogenic He-3 and Ne-21 dating of biotite and hornblende // Earth Planet. Sci. Lett. 2012. Vol. 313. P. 86–94.

Stable cosmogenic isotopes such as He-3 and Ne-21 are useful for dating of diverse lithologies, quantifying erosion rates and ages of ancient surfaces and sediments, and for assessing complex burial histories. Although many minerals are potentially suitable targets for He-3 and Ne-21 dating, complex production systematics require calibration of each mineral-isotope pair. We present new results from a drill core in a high-elevation ignimbrite surface, which demonstrates that cosmogenic He-3 and Ne-21 can be readily measured in biotite and hornblende. Ne-21 production rates in hornblende and biotite are similar, and are higher than that in quartz due to production from light elements such as Mg and Al. We measure Ne-21(hbl)/Ne-21(qtz) = 1.35 +/- 0.03 and Ne-21(bio),/Ne-21(qtz) = 1.3 +/- 0.02, which yield production rates of 25.6 +/- 3.0 and 24.7 +/- 2.9 at g(-1) yr(-1) relative to a Ne-21(qtz) production rate of 19.0 +/- 1.8 at g(-1) yr(-1). We show that nucleogenic Ne-21 concentrations produced via the reaction O-18(alpha,n)Ne-21 are manageably small in this setting, and we present a new approach to deconvolve nucleogenic Ne-21 by comparison to nucleogenic Ne-22 produced from the reaction F-19(alpha,n)Ne-22 in F-rich phases such as biotite. Our results show that hornblende is a suitable target phase for cosmogenic He-3 dating, but that He-3 is lost from biotite at Earth surface temperatures. Comparison of He-3 concentrations in hornblende with previously measured mineral phases such as apatite and zircon provides unambiguous evidence for He-3 production via the reaction Li-6(n,alpha)H-3 -> He-3. Due to the atypically high Li content in the hornblende (similar to 160 ppm) we estimate that Li-produced He-3 represents similar to 40% of total He-3 production in our samples, and must be considered on a sample-specific basis if He-3 dating in hornblende is to be widely implemented.

Bast R. et al. Boron isotopes in tourmaline as a tracer of metasomatic processes in the Bamble sector of Southern Norway // Contrib. Mineral. Petrol. 2014. Vol. 168, № 4. P. 1069.

The Bamble sector of southern Norway comprises metagabbros and metasediments that were metasomatically altered to various extents during a late stage of the Sveconorwegian orogeny (similar to 1.06 Ga). The infiltration of highly saline brines along veins led to penetrative scapolitization and albitization on a regional scale and the local deposition of Fe-Ti oxides. Typical secondary mineral assemblages include either scapolite + apatite + amphibole + phlogopite + tourmaline, or albite + epidote + calcite + chlorite + white mica, indicating that the fluids introduced large amounts of Na, Cl, Mg, Ca, K, P, and B to the system. Metasomatic tourmalines associated with different alteration stages as identified by variations in major-element composition and initial Sr-87/Sr-86 were analyzed for B isotopic compositions to constrain possible sources and the evolution of the hydrothermal fluid(s). Measured delta B-11 values range from -5 to +27 % relative to SRM-951, suggesting marine evaporites interlayered with various amounts of continental detritus and pelagic clay as a possible B source reservoir. The influence of a seawater-derived component is clearly indicated by the heavy B isotope signature of tourmaline related to Al-Mg-rich metapelites. In contrast, negative delta B-11 values can be explained by the influence of pneumatolytic fluids associated with granitic pegmatites. On a regional scale (i.e., several km), delta B-11 values in tourmaline vary widely, whereas variations within a single outcrop (tens of m) are typically small and can be ascribed to different generations of tourmaline related to several fluid pulses.

Berkenbosch H.A. et al. Characteristics of Cu isotopes from chalcopyrite-rich black smoker chimneys at Brothers volcano, Kermadec arc, and Niuatahi volcano, Lau basin // Miner. Depos. 2015. Vol. 50, № 7. P. 811–824.

We analysed primary chalcopyrite from modern seafloor 'black smoker' chimneys to investigate high-temperature hydrothermal Cu isotope fractionation unaffected by metamorphism. Samples came from nine chimneys collected from Brothers volcano, Kermadec arc, and Niuatahi volcano, Lau backarc basin. This is the first known study of Cu isotopes from submarine intraoceanic arc/backarc volcanoes, with both volcanoes discharging significant amounts of magmatic volatiles. Our results (n = 22) range from delta Cu-65 = -0.03 to 1.44 +/- 0.18 aEuro degrees (2 sd), with the majority of samples between similar to 0.00 and 0.50 aEuro degrees. We interpret this cluster (n = 17) of lower delta Cu-65 values as representing a mantle source for the chimney Cu, in agreement with delta Cu-65 values for mantle rocks. The few higher delta Cu-65 values (> 0.90 aEuro degrees) occur (1) within the same chimneys as lower values, (2) randomly distributed within the chimneys (i.e. near the top and bottom, interior and exterior), and (3) within chalcopyrite of approximately the same age (< 1 year). This suggests the higher delta Cu-65 values are not related to oxidation by mixing with ambient seawater, but to isotopic variation within the vent fluids over a relatively short time. Theoretical studies demonstrate significant isotopic fractionation can occur between aqueous and vapourous complexing species. When combined with evidence for periodic release of magmatic volatiles at Brothers, we believe vapour transport of Cu is responsible for the observed isotopic fractionation. When compared to global delta Cu-65 data for primary chalcopyrite, volcanic arc chimneys are most similar to porphyry copper deposits that also form from magmatic-hydrothermal processes in convergent tectonic settings.

Bird M.I., Ascough P.L. Isotopes in pyrogenic carbon: A review // Org. Geochem. 2012. Vol. 42, № 12. P. 1529–1539.

Pyrogenic carbon (PC; also known as biochar, charcoal, black carbon and soot) derived from natural and anthropogenic burning plays a major, but poorly quantified, role in the global carbon cycle. Isotopes provide a fundamental fingerprint of the source of PC and a powerful tracer of interactions between PC and the environment. Radiocarbon and stable carbon isotope techniques have been widely applied to studies of PC in aerosols, soils, sediments and archaeological sequences, with the use of other isotopes currently less developed. This paper reviews the current state of knowledge regarding (i) techniques for isolating PC for isotope analysis and (ii) processes controlling the carbon (C-13 and C-14), nitrogen, oxygen, hydrogen and sulfur isotope composition of PC during formation and after deposition. It also reviews the current and potential future applications of isotope based studies to better understand the role of PC in the modern environment and to the development of records of past environmental change.

Blaser M.B., Dreisbach L.K., Conrad R. Carbon isotope fractionation of Thermoanaerobacter kivui in different growth media and at different total inorganic carbon concentration // Org. Geochem. 2015. Vol. 81. P. 45–52.

Chemolithotrophic homoacetogenic bacteria apparently express a characteristic stable carbon isotope fractionation and may contribute significantly to acetate production in anoxic environments. However, fractionation factors (epsilon) in bacterial cultures have rarely been determined and the effect of substrate availability has not been assessed. We therefore studied the kinetic carbon isotope effect in cultures of Thermoanaerobacter kivui grown at 55 degrees C. The fractionation factor in HCO3- buffered medium was ca. 15% more negative than that in PO43- buffered medium. To test whether the difference was caused by the initial substrate ratio of H-2 and total inorganic carbon (TIC; 0.5 in HCO3- vs. 4.0 in PO43- buffered medium), Thermoanaerobacter kivui was grown in either [3-(N-morpholino) propanesulfonic acid, MOPS] buffered or PO43- buffered media with different HCO3- concentration. Indeed, the fractionation factor became more negative with increasing HCO3- concentration and decreasing H-2/TIC ratio. While pH had only a small effect, the fractionation was generally more negative in MOPS buffered than in phosphate buffered media, indicating that the buffer system also affected fractionation. Collectively, the results show that substrate availability and other environmental factors affect the magnitude of isotope fractionation during acetate production by chemolithotrophic homoacetogenesis.

Blichert-Toft J. et al. Hf and Nd isotope systematics of early Archean komatiites from surface sampling and ICDP drilling in the Barberton Greenstone Belt, South Africa // Am. Miner. 2015. Vol. 100, № 11–12. P. 2396–2411.

To constrain the origin of komatiites from the Barberton Green-stone Belt, South Africa, we measured Sm-147-Nd-143 and Lu-176-Hf-176 compositions for 18 komatiites from core obtained during the International Continental Drilling Program in the Komati Formation of the Barberton Belt, as well as 33 komatiites from surface outcrops of the Komati, Hooggenoeg, and Weltevreden Formations, these latter for purposes of comparison between core and surface samples. Magmatic clinopyroxene from surface samples near the drill site was also analyzed. For the Lu-Hf isotope system, the Komati Formation core and surface samples including the clinopyroxene define a linear array whose slope corresponds to an age of 3426 +/- 16 Ma (MSWD = 118; epsilon(Hf(T)) = +2.2), which is slightly younger than the accepted age of the rocks (3.48 Ga). The Sm-Nd isotope data for the same set of samples likewise fall along a linear array also yielding a younger age of 3339 12 Ma (MSWD = 42; epsilon(Nd(T)) = +2.8). The high MSWD for both isotope systems indicate substantial scatter at variance with normal magmatic processes, likely implying element mobility disturbing even these relatively robust isotopic systems shortly after eruption of the lavas. The average initial epsilon(Nd) and epsilon(Hf) of the core samples at 3.48 Ga are +0.45 and +1.4, respectively, in overall accordance with the positive errorchron intercepts and a depleted mantle source at 3.5 Ga. In contrast, the clinopyroxene and their host rocks have strongly positive epsilon(Hf(T)) of about +5 and negative epsilon(Nd(T)) of about -2. Given the overall scatter of the whole-rock data, the most robust constraint on the composition of the komatiite source comes from the clinopyroxene. Their positive slug) is in line with, though somewhat higher than other results from komatiites from the Komati Formation, but their negative epsilon(Nd(T)) is unexpected in that it indicates a source with long-term low Sm/Nd, which is at odds with its long-term high Lu/Hf. This signature is also found in the trace element compositions of some of the komatiites, such as moderately enriched LREE, negative Hf anomalies, and low Hf/Sm ratios. The origin of these features is uncertain but one possibility is that the discordance between the Hf and Nd isotope systems reflects the presence of deep-sea sediments in the source of some of the Barberton komatiites. The possible presence of a surface component in an ancient deep mantle source has wide-ranging implications for mantle-crust interaction and dynamics in the early Earth and for constraining a minimum age for the onset of plate tectonics.

Bobocioiu E., Caracas R. Stability and spectroscopy of Mg sulfate minerals: Role of hydration on sulfur isotope partitioning // Am. Miner. 2014. Vol. 99, № 7. P. 1216–1220.

We study hydrated magnesium sulfate minerals from first-principles calculations based on density-functional theory. We determine the heat of hydration for MgSO4 center dot nH(2)O, compute the Raman and infrared spectra for several phases and calculate the S isotope partitioning as a function of hydration. We find that epsomite and meridianiite with, respectively, n = 7 and n = 11 water molecules per MgSO4 unit are particularly stable with respect to other individual or combinations of hydration states. The Raman spectra of all phases present clear SO4 features that are easily identifiable. We use this to show one can use the vibrational spectroscopic information as an identification tool in a remote environment, like the martian surface. We discuss the character and atomic displacement pattern of all vibration modes and compute the S-34/S-32 partitioning; this work shows that hydration favors enrichment in the lighter S isotope S-32 with respect to the heavier S-34, which is accumulated in the less hydrous structures. We show for the first time that the signature of S-34/S-32 partitioning could be observed by in situ spectroscopy on the surface of Mars. Moreover this can be related to the diurnal cycle of hydration and dehydration and hence it can improve the modeling of the water circulation on Mars.

Bot A. et al. Miocene detachment faulting predating EPR propagation: Southern Baja California // Tectonics. 2016. Vol. 35, № 5. P. 1153–1176.

At the southern tip of the Baja California peninsula, we characterize the onshore structures and kinematics associated with crustal necking leading up to the Pliocene breakup and early East Pacific Rise seafloor spreading. From a combination of tectonic field investigations, K-Ar and cosmogenic isotope dating and geomorphology, we propose that the Los Cabos block represents the exhumed footwall of a major detachment fault. This north trending detachment fault is marked by a conspicuous low-dipping brittle-ductile shear zone showing a finite displacement with top to the SE ending to the ESE. This major feature is associated with fluid circulations which led to rejuvenation of the deformed Cretaceous magmatic rocks at a maximum of 17.5Ma. The detachment footwall displays kilometer-scale corrugations controlling the present-day drainage pattern. This major detachment is synchronous with the development of the San Jose del Cabo Basin where syntectonic sedimentation took place from the middle Miocene to probably the early Pliocene. We propose that this seaward dipping detachment fault accommodates the proximal crustal necking of the Baja California passive margin, which predates the onset of formation of the East Pacific Rise spreading axis in the Cabo-Puerto Vallarta segment. Our data illustrate an apparent anticlockwise rotation of the stretching direction in Baja California Sur from similar to 17 Ma to the Pliocene.

Campuzano S.A., Pavon-Carrasco F.J., Osete M.L. Non-Dipole and Regional Effects on the Geomagnetic Dipole Moment Estimation // Pure Appl. Geophys. 2015. Vol. 172, № 1. P. 91–107.

The study of the temporal evolution of the dipole moment variations is a forefront research topic in Earth sciences. It constrains geodynamo simulations and is used to correct cosmogenic isotope production, which is evidence of past solar activity, and it is used to study possible correlations between the geomagnetic field and the climate. In this work, we have analysed the main error sources in the geomagnetic dipole moment computation from palaeomagnetic data: the influence of the non-dipole terms in the average approach, the inhomogeneous distribution of the current palaeomagnetic database, and the averaging procedure used to obtain the evolution of the dipole moment. To evaluate and quantify these effects, we have used synthetic data from a global model based on instrumental and satellite data, the International Geomagnetic Reference Field: 11th generation. Results indicate that the non-dipole terms contribute on a global scale of < 6 % in the averaged dipole moment, whereas the regional non-dipole contribution can show deviations of up to 35 % in some regions such as Oceania, and different temporal trends with respect to the global dipole moment evolution in other ones, such as Europe and Asia. A regional weighting scheme seems the best option to mitigate these effects in the dipole moment average approach. But when directional and intensity palaeomagnetic information is available on a global scale, and in spite of the inhomogeneity of the database, global modelling presents more reliable values of the geomagnetic dipole moment.

Carucci V., Petitta M., Aravena R. Interaction between shallow and deep aquifers in the Tivoli Plain (Central Italy) enhanced by groundwater extraction: A multi-isotope approach and geochemical modeling // Appl. Geochem. 2012. Vol. 27, № 1. P. 266–280.

In the Tivoli Plain (Rome, Central Italy) the interaction between shallow and deep groundwater flow systems enhanced by groundwater extraction has been investigated using isotopic and chemical tracers. A conceptual model of the groundwater flowpaths has been developed and verified by geochemical modeling. A combined hydrogeochemical and isotopic investigation using ion relationships such as DIC/Cl , Ca/(Ca + Mg)/SO4/(SO4 + HCO3), and environmental isotopes (delta O-18, delta H-2, Sr-87/Sr-86, delta S-34 and delta C-13) was carried out in order to determine the sources of recharge of the aquifer, the origin of solutes and the mixing processes in groundwater of Tivoli Plain. Multivariate statistical methods such as principal component analysis and Cluster analyses have confirmed the existence of different geochemical facies and the role of mixing in the chemical composition of the groundwater. Results indicate that the hydrochemistry of groundwater is characterized by mixing between end-members coming directly from carbonate recharge areas and to groundwater circulating in a deeply buried Meso-Cenozoic carbonate sequence. The travertine aquifer is fed by both flow systems, but a local contribution by direct input in the Plain has also been recognized. The stable isotope data (O-18, H-2, C-13 and S-34) supports the flow system conceptual model inferred from the geochemical data and represents key data to quantify the geochemical mixing in the different groundwaters of the Plain. The results of numerical modeling (PHREEQC) are consistent with the flowpaths derived from the hydrogeochemical conceptual model. The inverse models performed generated the main geochemical processes occurring in the groundwater flow system, which also included mixing. Geochemical and isotope modeling demonstrate an increasing influence of groundwater from the deeply buried aquifer in the travertine aquifer, enhanced by lowering of the travertine aquifer water table due to quarry pumping.

Chakoumakos B.C., Horita J., Garlea V.O. H/D isotope effects in brucite at low temperatures // Am. Miner. 2013. Vol. 98, № 1. P. 1–6.

Joint refinement of powder neutron diffraction data of hydrogenated and deuterated brucite over the temperature range of 10-295 K clearly shows significant isotope effects in the structural parameters. Mg(OH)(2) has a 0.31% larger volume than that of Mg(OD)(2) at room temperature, which is mostly due to the c-axis expansion of Mg(OH)(2) as compared to Mg(OD)(2). The isotope effect in the a-axis has the opposite, but smaller, behavior as compared to the c-axis. These differences are slightly enhanced with reduction of the cell volume upon cooling. The temperature dependence of the isotropic atomic displacement parameters (ADPs) with the single site model show that the ADP of the H atom is approximately larger than that of the D atom by the amount expected from the reduced-mass difference, but this difference is not evident with the split site model. Despite the shorter c-axis of the deuterated form, nearest-neighbor D center dot center dot center dot D distances are longer than the H center dot center dot center dot H distances, because the O-H distances are longer than the O-D distances, which necessarily places the H atoms closer together by 0.03 angstrom or more within the interlayer space. This study showcases an example of when a joint Rietveld refinement is ideally suited, by combining data for the deuterated and hydrogenated forms of brucite. The approach reduces the number of least-squares variables, and reduces the systematic errors. It can be a general method to analyze isotope effects in materials studied by neutron diffraction.

Chakrabarti R. et al. Si isotope variability in Proterozoic cherts // Geochim. Cosmochim. Acta. 2012. Vol. 91. P. 187–201.

We report Si-isotopic compositions of 75 sedimentologically and petrographically characterized chert samples with ages ranging from similar to 2600 to 750 Ma using multi-collector inductively coupled plasma mass spectrometry. delta Si-30 values of the cherts analyzed in this study show a similar to 7 parts per thousand range, from -4.29 to +2.85. This variability can be explained in part by (1) simple mixing of silica derived from continental (higher delta Si-30) and hydrothermal (lower delta Si-30) sources, (2) multiple mechanisms of silica precipitation and (3) Rayleigh-type fractionations within pore waters of individual basins. We observe similar to 3 parts per thousand variation in peritidal cherts from a single Neoproterozoic sedimentary basin (Spitsbergen). This variation can be explained by Rayleigh-type fractionation during precipitation from silica-saturated porewaters. In some samples, post-dissolution and reprecipitation of silica could have added to this effect. Our data also indicate that peritidal cherts are enriched in the heavier isotopes of Si whereas basinal cherts associated with banded iron formations (BIF) show lower delta Si-30. This difference could partly be due to Si being derived from hydrothermal sources in BIFs. We postulate that the difference in delta Si-30 between non-BIF and BIF cherts is consistent with the contrasting genesis of these deposits. Low delta Si-30 in BIF is consistent with laboratory experiments showing that silica adsorbed onto Fe-hydroxide particles preferentially incorporates lighter Si isotopes. Despite large intrabasinal variation and environmental differences, the data show a clear pattern of secular variation. Low delta Si-30 in Archean cherts is consistent with a dominantly hydrothermal source of silica to the oceans at that time. The monotonically increasing delta Si-30 from 3.8 to 1.5 Ga appears to reflect a general increase in continental versus hydrothermal sources of Si in seawater, as well as the preferential removal of lighter Si isotopes during silica precipitation in iron-associated cherts from silica-saturated seawater. The highest delta Si-30 values are observed in 1.5 Ga peritidal cherts; in part, these enriched values could reflect increasing sequestration of light silica during soil-forming processes, thus, delivering relatively heavy dissolved silica to the oceans from continental sources. The causes behind the reversal in trend towards lower delta Si-30 in cherts younger than 1.5 Ga old are less clear. Cherts deposited 1800-1900 Ma are especially low delta Si-30, a possible indication of transiently strong hydrothermal input at this time.

Chela-Flores J. et al. Biogeochemical fingerprints of life: earlier analogies with polar ecosystems suggest feasible instrumentation for probing the Galilean moons // Int. J. Astrobiol. 2015. Vol. 14, № 3. P. 427–434.

We base our search for the right instrumentation for detecting biosignatures on Europa on the analogy suggested by the recent work on polar ecosystems in the Canadian Arctic at Ellesmere Island. In that location sulphur patches (analogous to the Europan patches) are accumulating on glacial ice lying over saline springs rich in sulphate and sulphide. Their work reinforces earlier analogies in Antarctic ecosystems that are appropriate models for possible habitats that will be explored by the European Space Agency JUpiter ICy Moons Explorer (JUICE) mission to the Jovian System. Its Jupiter Ganymede Orbiter (JGO) will include orbits around Europa and Ganymede. The Galileo orbital mission discovered surficial patches of non-ice elements on Europa that were widespread and, in some cases possibly endogenous. This suggests the possibility that the observed chemical elements in the exoatmosphere may be from the subsurface ocean. Spatial resolution calculations of Cassidy and co-workers are available, suggesting that the atmospheric S content can be mapped by a neutral mass spectrometer, now included among the selected JUICE instruments. In some cases, large S-fractionations are due to microbial reduction and disproportionation (although sometimes providing a test for ecosystem fingerprints, even though with Sim-Bosak-Ono we maintain that microbial sulphate reduction large sulphur isotope fractionation does not require disproportionation. We address the question of the possible role of oxygen in the Europan ocean. Instrument issues are discussed for measuring stable S-isotope fractionations up to the known limits in natural populations of (34)approximate to-70 parts per thousand. We state the hypothesis of a Europa anaerobic oceanic population of sulphate reducers and disproportionators that would have the effect of fractionating the sulphate that reaches the low-albedo surficial regions. This hypothesis is compatible with the time-honoured expectation of Kaplan and co-workers (going back to the 1960s) that the distribution range of S-32/S-34 in analysed extra-terrestrial material appears to be narrower than the isotopic ratio of H, C or N and may be the most reliable for estimating biological effects. In addition, we discuss the necessary instruments that can test our biogenic hypothesis. First of all we hasten to clarify that the last-generation miniaturized mass spectrometer we discuss in the present paper are capable of reaching the required accuracy of parts per thousand for the all-important measurements with JGO of the thin atmospheres of the icy satellites. To implement the measurements, we single out miniature laser ablation time-of-flight mass spectrometers that are ideal for the forthcoming JUICE probing of the exoatmospheres, ionospheres and, indirectly, surficial low-albedo regions. Ganymede's surface, besides having ancient dark terrains covering about one-third of the total surface, has bright terrains of more recent origin, possibly due to some internal processes, not excluding biological ones. The geochemical test could identify bioindicators on Europa and exclude them on its large neighbour by probing relatively recent bright terrains on Ganymede's Polar Regions.

Darling J.R. et al. Variable microstructural response of baddeleyite to shock metamorphism in young basaltic shergottite NWA 5298 and improved U-Pb dating of Solar System events // Earth Planet. Sci. Lett. 2016. Vol. 444. P. 1–12.

The accurate dating of igneous and impact events is vital for the understanding of Solar System evolution, but has been hampered by limited knowledge of how shock metamorphism affects mineral and whole rock isotopic systems used for geochronology. Baddeleyite (monoclinic ZrO2) is a refractory mineral chronometer of great potential to date these processes due to its widespread occurrence in achondrites and robust U-Pb isotopic systematics, but there is little understanding of shock-effects on this phase. Here we present new nano-structural measurements of baddeleyite grains in a thin-section of the highly shocked basaltic shergottite Northwest Africa (NWA) 5298, using high-resolution electron backscattered diffraction (EBSD) and scanning transmission electron microscopy (STEM) techniques, to investigate shock-effects and their linkage with U-Pb isotopic disturbance that has previously been documented by in-situ U-Pb isotopic analyses. The shock-altered state of originally igneous baddeleyite grains is highly variable across the thin-section and often within single grains. Analyzed grains range from those that preserve primary (magmatic) twinning and trace-element zonation (baddeleyite shock Group 1), to quasi-amorphous ZrO2 (Group 2) and to recrystallized micro-granular domains of baddeleyite (Group 3). These groups correlate closely with measured U-Pb isotope compositions. Primary igneous features. in Group 1 baddeleyites (n = 5) are retained in high shock impedance grain environments, and an average of these grains yields a revised late-Amazonian magmatic crystallization age of 175 +/- 30 Ma for this shergottite. The youngest U-Pb dates occur from Group 3 recrystallized nano- to micro-granular baddeleyite grains, indicating that it is post-shock heating and new mineral growth that drives much of the isotopic disturbance, rather than just shock deformation and phase transitions. Our data demonstrate that a systematic multi-stage microstructural evolution in baddeleyite results from a single cycle of shock-loading, heating and cooling during transit to space, and that this leads to variable disturbance of the U-Pb isotope system. Furthermore, by linking in-situ U-Pb isotopic measurements with detailed micro- to nano-structural analyses, it is possible to resolve the timing of both endogenic crustal processes and impact events in highly-shocked planetary materials using baddeleyite. This opens up new opportunities to refine the timing of major events across the Solar System.

du Bray E.A. et al. Geochemistry, petrologic evolution, and ore deposits of the Miocene Bodie Hills Volcanic Field, California and Nevada // Am. Miner. 2016. Vol. 101, № 3–4. P. 644–677.

The southern segment of the ancestral Cascades magmatic arc includes numerous volcanic fields; among these, the Bodie Hills volcanic field (BHVF), astride the California-Nevada border north of Mono Lake, is one of the largest (>700 km(2)) and most well studied. Episodic magmatism in the BHVF spanned about 9 million years between about 15 and 6 Ma; magmatic output was greatest between ca. 15.0 to 12.6 Ma and ca. 9.9 to 8.0 Ma. About two dozen contiguous and coalescing eruptive centers above middle- to shallow-crustal-level reservoirs generated several trachyandesite stratovolcanoes and numerous silicic trachyandesite to rhyolite flow dome complexes whose compositional variations are consistent with fractionation of observed phenocryst phases. BHVF rocks have high-potassium calc-alkaline compositions consistent with generation of subduction-related continental margin arc magmas beneath thick continental crust. Radiogenic isotope ratios in BHVF rocks vary considerably but suggest somewhat enriched, crustal sources; isotopic ratios for some of the more primitive units are consistent with more depleted, mantle sources. Neither age nor whole-rock compositions of BHVF rocks are well correlated with isotopic variations. Textures and compositions of phenocrysts in BHVF rocks are in accord with the associated magma reservoirs evolving via open-system behavior. Reservoir recharge and subsequent incomplete homogenization are evidenced by the broad compositional diversity characteristic of many BHVF eruptive units. Significant compositional diversity among the products of coeval eruptive centers further suggests that centers responsible for BHVF magmatism were underlain by small, discrete, compositionally distinct, and closely spaced reservoirs. Volcanic rocks of the BHVF host quartz-adularia and quartz-alunite epithermal gold-silver deposits, from which about 3.4 Moz. of gold and 28 Moz. of silver have been produced. The volcanic rocks and contained deposits are broadly coeval, which suggests that the associated magmas are the sources of heat, fluids, and metals involved in deposit genesis. Characteristics of the quartz-adularia deposits are consistent with derivation from near-neutral pH fluids at <= 250 degrees C, whereas those of the quartz-alunite systems require more acidic, oxidized, and sulfur-rich fluids at temperatures <250 degrees C. Economically viable precious metal accumulations are in fault-hosted vein deposits in the Bodie and Aurora districts. Circulation of hydrothermal fluids through permeable pyroclastic deposits but lacking prominent structural conduits resulted in large areas of altered but unmineralized rock.

El-Taher A., Alharbi A. Elemental analysis of natural quartz from Um Higlig, Red Sea Aea, Egypt by instrumental neutron activation analysis // Applied Radiation and Isotopes. 2013. Vol. 82. P. 67–71.

A scheme for INAA of 25 elements: As, Ba, Ca, Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Mg, Mn, Na, Nd, Rb, Sc, Sm, Th, U, Yb, Zn and Zr in quartz collected from the eastern desert along the Egyptian Red Sea coast is proposed. The samples were prepared together with standard reference material and irradiated in a neutron flux of 7?1011 n/cm2 s in the TRIGA Mainz research reactor facilities. The gamma spectra were collected by a HPGe detector and the analysis was done by a computerized multichannel analyzer.The accuracy of the procedure is evaluated by the analysis of two geo-standard reference materials (Dolerite WSE and Microgabro PMS). The choice of the nuclear reaction, irradiation and decay times and of the proper gamma radiation in counting are presented and discussed. The data presented here are our contribution to understanding the elemental composition of the quartz rock. Because there are no existing databases for the elemental analysis of quartz, our results are a start to establishing a database for the Egyptian quartz. It is hoped that the data presented here will be useful to those dealing with geochemistry, quartz chemistry and related fields.

Facorellis Y. et al. Interpreting Radiocarbon Dates from the Paleolithic Layers of Theopetra Cave in Thessaly, Greece // Radiocarbon. 2013. Vol. 55, № 2–3. P. 1432–1442.

Theopetra Cave is a unique prehistoric site for Greece, as the Middle and Upper Paleolithic, Mesolithic, and Neolithic periods are present here, bridging the Pleistocene with the Holocene. During the more than 20 yr of excavation campaigns, charcoal samples from hearths suitable for C-14 dating were collected from all anthropogenic layers, including the Paleolithic ones. Most of the samples were initially dated using the ABA chemical pretreatment protocol in the Laboratory of Archaeometry of NCSR Demokritos, Greece, and the Radiocarbon Dating and Cosmogenic Isotopes Laboratory of the Weizmann Institute of Science, Israel. The C-14 results, which were not always consistent versus depth, showed that the earliest limit of human presence is similar to 50,000 yr BP, thus reaching the age limits of the C-14 dating method. However, 10 TL-dated burnt flint specimens unearthed from the lower part of the Middle Paleolithic sequence of the cave gave ages ranging between similar to 110 and 135 kyr ago. These results are in disagreement with the C-14 dates, as they support a much later date for these layers. In order to clarify the situation further, charcoal samples originating from hearths were conventionally dated in the Laboratory of Archaeometry of NCSR Demokritos using the ABA pretreatment. Additionally, hand-picked charcoal fragments also underwent C-14 dating by AMS in the Oxford Radiocarbon Accelerator Unit using the acid-base wet oxidation (ABOX-SC) pretreatment protocol. The C-14 dates from the cave's Paleolithic layers obtained by both pretreatment protocols suggest a probable charcoal diagenesis affecting the C-14 results of these very old samples. However, the dates obtained with ABOX-SC pretreatment are considered more reliable and in the younger stratigraphic part produced consistent results with the TL dating.

Fairen A.G. et al. Tracking the weathering of basalts on Mars using lithium isotope fractionation models // Geochem. Geophys. Geosyst. 2015. Vol. 16, № 4. P. 1172–1197.

Lithium (Li), the lightest of the alkali elements, has geochemical properties that include high aqueous solubility (Li is the most fluid mobile element) and high relative abundance in basalt-forming minerals (values ranking between 0.2 and 12 ppm). Li isotopes are particularly subject to fractionation because the two stable isotopes of lithium(7)Li and (6)Lihave a large relative mass difference (approximate to 15%) that results in significant fractionation between water and solid phases. The extent of Li isotope fractionation during aqueous alteration of basalt depends on the dissolution rate of primary mineralsthe source of Liand on the precipitation kinetics, leading to formation of secondary phases. Consequently, a detailed analysis of Li isotopic ratios in both solution and secondary mineral lattices could provide clues about past Martian weathering conditions, including weathering extent, temperature, pH, supersaturation, and evaporation rate of the initial solutions in contact with basalt rocks. In this paper, we discuss ways in which Martian aqueous processes could have lead to Li isotope fractionation. We show that Li isotopic data obtained by future exploration of Mars could be relevant to highlighting different processes of Li isotopic fractionation in the past, and therefore to understanding basalt weathering and environmental conditions early in the planet's history.

Feng W. et al. Oxygen isotope variations in rainfall, drip-water and speleothem calcite from a well-ventilated cave in Texas, USA: Assessing a new speleothem temperature proxy // Geochim. Cosmochim. Acta. 2014. Vol. 127. P. 233–250.

Measurements of the oxygen isotopic composition (delta O-18 value) of rainfall, drip-water and associated calcite (grown on artificial substrates and in a natural speleothem) at multiple drip sites in a well-ventilated cave in central Texas were conducted to investigate the potential use of speleothem delta O-18 for quantitative temperature reconstructions. From 2009 to 2011, rainfall delta O-18 varied by 11.5 parts per thousand (-10.5 parts per thousand to 1.0 parts per thousand, V-SMOW), whereas drip-waters had a much narrower range of 0.3 parts per thousand (-4.7 parts per thousand to -4.4 parts per thousand, V-SMOW). This contrast indicates that mixing processes along flow paths in the vadose zone above the cave produce a well-homogenized water reservoir that supplies drip-water to the cave. The delta O-18 values for calcite grown on substrates over the same time period show seasonal variations (summer: similar to-6 parts per thousand; winter: similar to-3 parts per thousand) that are strongly correlated with surface air temperatures (t(a)) at all three monitored sites (r(2) = 0.88-0.96; p < 0.001). These results indicate that the dominant control on calcite delta O-18 is temperature. An empirical relationship was established for one monitored site: t(a) = -9.1 (+0.9) x delta O-18 X 10(-3) - 20.6 (+/- 4.1); r(2) = 0.88, and applied to a delta O-18 time series of the top 6.7 mmof a stalagmite that grew at this drip site. This yields a temperature record that appears to reflect seasonal variations for the period 2005-2009. This speleothem-derived temperature record is offset to lower values (by 0-8 degrees C) compared to the instrumental temperature record. This offset may be a result of differences between substrate and speleothem calcite in terms growth mechanism, extent of non-equilibrium isotopic effects, or temporal shifts in drip-water delta O-18 values. Despite this offset, the speleothem-derived record reconstructs the amplitudes of seasonal variations and changes in inter-annual summer peak temperatures in the instrumental record. Results of this study have implications for reconstructing past temperatures, and for establishing a speleothem chronology with seasonal resolution, using speleothem calcite delta O-18. The results also suggest that relatively seldom-studied speleothem samples near the entrances of caves, where environmental conditions may be similar to surface conditions, could prove valuable as paleo-temperature archives.

Foden J., Sossi P.A., Wawryk C.M. Fe isotopes and the contrasting petrogenesis of A-, I- and S-type granite // Lithos. 2015. Vol. 212. P. 32–44.

We present new Fe isotope data of 42 S-, I- and A-type (ferroan) granites from the Cambrian Delamerian orogen in South Australia, the Palaeozoic Lachlan Fold Belt and Western USA. Interpretation of these data, together with modelling suggests that magmatic processes do result in quite complex Fe-isotopic differentiation trends and can lead to granites with isotopically heavy iron with delta Fe-57 > 0.35 parts per thousand. By comparison Mid-Ocean Ridge Basalts (MORBs) have delta Fe-57 = 0.15 parts per thousand (Teng et al., 2013). These variations are similar to those previously reported (Poitrasson and Freydier, 2005; Heimann et al., 2008; Telus et al., 2012), but, contrary to some interpretations (Beard and Johnson, 2006; Heimann et al., 2008), heavy values are not necessarily the product of late-stage hydrothermal fluid loss, though this process is undoubtedly also an important factor in some circumstances. A-type (ferroan) granites reach very heavy delta Fe-57 values (0.4-0.5 parts per thousand) whereas I-types are systematically lighter (delta Fe-57 = 0.2 parts per thousand). S-type granites show a range of intermediate values, but also tend to be isotopically heavy (delta Fe-57 approximate to 0.2-0.4 parts per thousand). Our results show that the iron isotopic values and trends are signatures that reflect granite generation processes. A modelling using the Rhyolite-MELTS software suggests that contrasting trajectories and end-points in Fe isotope evolution towards granite depend on: oxidation state of the evolving magma and, whether or not the system is oxygen-buffered. Iron isotopic evolution supports an origin of ferroan A-type granite from protracted, closed magma chamber fractionation of moderately reduced mafic magmas. In these systems magnetite saturation is delayed and the ferric iron budget is finite. I-type systems originate with the supply of relatively oxidised, hydrous, subduction-related magmas from the mantle wedge to the upper plate crust. These then experience oxygen-buffered open-system AFC processes in lower crustal hot-zones. S-type magmas are crustal melts that crystallise under reduced conditions initially imposed at source by sulphidic or graphitic sedimentary protoliths. The composition of the resulting melts reflects the domination of partial melting where conditions are hence buffered (open system) followed by subsequent late-stage, closed system fractionation of these extracted, reduced magmas.

Foustoukos D.I., Mysen B.O. H/D methane isotopologues dissolved in magmatic fluids: Stable hydrogen isotope fractionations in the Earth’s interior // Am. Miner. 2013. Vol. 98, № 5–6. P. 946–954.

A series of hydrothermal diamond-anvil cell experiments have been conducted to evaluate the role of supercritical water on the isotopic equilibrium between H/D methane isotopologues at 600-800 degrees C and 409-1622 MPa. Raman spectroscopy was deployed to investigate the distribution of HID isotopic molecules formed during hydrothermal decomposition of Si5C12H36 in H2O-D2O aqueous solutions. To this end, the intensities of the fundamental vibrational C-H and C-D modes of deuteromethanes were employed to determine the thermodynamic properties of isotope exchange reactions between HID isotopologues and to constrain the methane D/H molar ratios. By adjusting the initial volume ratios of silane/H2O-D2O, reactions in the CH4-D2O-H2O system were monitored for gaseous and supercritical-water phases. Discreet differences between the equilibrium constants, describing the relationship between the CH3D-CH2D2-CHD3-CH4 species dissolved in supercritical water or present as a homogeneous gas phase, are revealed. The bulk D/H methane composition in the liquid-system is also twice that of the D/H molar ratios recorded in the gas-bearing system. Accordingly, condensed-phase isotope effects are inferred to play a key role on the evolution of H/D isotopologues, likely induced by differences in the solubility of the isotopic molecules driven by the excess energy/entropy developed during mixing of non-polar species in the H2O-D2O structure. Our experiments show that isotope fractionation effects need to account for the presence of condensed matter (e.g., melts, magmatic fluids), even at conditions at which theoretical models suggest minimal (or nonexistent) isotope exchange, but comparable to those within the Earth's interior.

Garcin Y. et al. Hydrogen isotope ratios of lacustrine sedimentary n-alkanes as proxies of tropical African hydrology: Insights from a calibration transect across Cameroon // Geochim. Cosmochim. Acta. 2012. Vol. 79. P. 106–126.

Hydrogen isotope values (delta D) of sedimentary aquatic and terrestrial lipid biomarkers, originating from algae, bacteria, and leaf wax, have been used to record isotopic properties of ancient source water (i.e., precipitation and/or lake water) in several mid-and high-latitude lacustrine environments. In the tropics, however, where both processes associated with isotope fractionation in the hydrologic system and vegetation strongly differ from those at higher latitudes, calibration studies for this proxy are not yet available. To close this gap of knowledge, we sampled surface sediments from 11 lakes in Cameroon to identify those hydro-climatological processes and physiological factors that determine the hydrogen isotopic composition of aquatic and terrestrial lipid biomarkers. Here we present a robust framework for the application of compound-specific hydrogen isotopes in tropical Africa. Our results show that the delta D values of the aquatic lipid biomarker n-C(17) alkane were not correlated with the delta D values of lake water. Carbon isotope measurements indicate that the n-C(17) alkane was derived from multiple source organisms that used different hydrogen pools for biosynthesis. We demonstrate that the delta D values of the n-C(29) alkane were correlated with the delta D values of surface water (i.e., river water and groundwater), which, on large spatial scales, reflect the isotopic composition of mean annual precipitation. Such a relationship has been observed at higher latitudes, supporting the robustness of the leaf-wax lipid delta D proxy on a hemispheric spatial scale. In contrast, the delta D values of the n-C(31) alkane did not show such a relationship but instead were correlated with the evaporative lake water delta D values. This result suggests distinct water sources for both leaf-wax lipids, most likely originating from two different groups of plants. These new findings have important implications for the interpretation of long-chain n-alkane delta D records from ancient lake sediments. In particular, a robust interpretation of palaeohydrological data requires knowledge of the vegetation in the catchment area as different plants may utilise different water sources. Our results also suggest that the combination of carbon and hydrogen isotopes does help to differentiate between the metabolic pathway and/or growth form of organisms and therefore, the source of hydrogen used during lipid biosynthesis.

Giesting P.A. et al. Igneous and shock processes affecting chassignite amphibole evaluated using chlorine/water partitioning and hydrogen isotopes // Meteorit. Planet. Sci. 2015. Vol. 50, № 3. P. 433–460.

Amphibole in chassignite melt inclusions provides valuable information about the volatile content of the original interstitial magma, but also shock and postshock processes. We have analyzed amphibole and other phases from NWA 2737 melt inclusions, and we evaluate these data along with published values to constrain the crystallization Cl and H2O content of phases in chassignite melt inclusions and the effects of shock on these amphibole grains. Using a model for the Cl/OH exchange between amphibole and melt, we estimate primary crystallization OH contents of chassignite amphiboles. SIMS analysis shows that amphibole from NWA 2737 currently has 0.15wt% H2O. It has lost similar to 0.6wt% H2O from an initial 0.7-0.8wt% H2O due to intense shock. Chassigny amphibole had on average 0.3-0.4wt% H2O and suffered little net loss of H2O due to shock. NWA 2737 amphibole has D approximate to+3700 parts per thousand; it absorbed Martian atmosphere-derived heavy H in the aftermath of shock. Chassigny amphibole, with D+1900 parts per thousand, incorporated less heavy H. Low H2O/Cl ratios are inferred for the primitive chassignite magma, which had significant effects on melting and crystallization. Volatiles released by the degassing of Martian magma were more Cl-rich than on Earth, resulting in the high Cl content of Martian surface materials.

Giuliani A. et al. Stable isotope (C, O, S) compositions of volatile-rich minerals in kimberlites: A review // Chem. Geol. 2014. Vol. 374. P. 61–83.

The composition of primary kimberlite melts and, in particular, the absolute and relative abundances of volatile components (mainly CO2 and H2O) are controversial issues, because kimberlite melts entrain and interact with abundant mantle and crustal xenoliths during ascent, react with wall rocks during emplacement, and lose some of their volatile inventory during pre-and syn-emplacement degassing. Compositional constraints are further complicated by the common alteration of kimberlitic rocks by post-emplacement fluids of various origin (e. g., deuteric, meteoric, hydrothermal). Consequently, the compositions of kimberlitic rocks may not be entirely representative of their parental melts. In kimberlitic rocks, CO2 is concentrated in carbonate minerals, whereas H2O is mainly stored in the secondary minerals serpentine and, to a lesser extent, chlorite and brucite, with minor contribution by primary magmatic phlogopite. This review focuses on utility of carbon, oxygen and sulphur stable isotopes to constrain the source of volatiles (i.e. magmatic vs non-magmatic) for carbonate, serpentine, sulphide and sulphate formation and the origin of fluids altering kimberlitic rocks. A global compilation of kimberlite carbonate data (delta C-13=-11.9 to + 0.2%, median delta C-13=-5.0%, relative to VPDB; delta O-18=1.2-26.6%, median delta O-18=13.2%, relative to VSMOW) reveals that the majority of results (86%) plot within a range of delta C-13 similar to-2 to -8%, which is considered representative of mantle carbon, but only 15% of analyses are in the field of oxygen isotopic values for mantle carbonates (delta O-18 similar to 6-9%). Variations in kimberlite carbon isotopic compositions occur on regional scales, implying widespread mantle heterogeneity, possibly related to input of carbon from recycled crustal material and/or partial overprinting by secondary processes at the local scale. Carbonates in southern African Group I (or archetype) and Group II kimberlites (or orangeites) show different delta C-13 distributions (median values of -5.3% and -6.5%, respectively). This is consistent with distinct mantle sources, as demonstrated previously by radiogenic isotope studies. Kimberlite breccia carbonates commonly have higher d18O values than carbonates in massive and hypabyssal kimberlites, which suggests more extensive interaction of kimberlite rocks with hydrous fluids in the brecciated parts of kimberlite pipes. Modelling of the stable isotope compositions of carbonates from the Kimberley, Lac de Gras and Udachnaya-East kimberlites reveals that several processes are capable of modifying these compositions, including interaction with H2O-rich deuteric (i.e. late-stage magmatic) fluids, meteoric waters and/or hydrothermal fluids, and incorporation of sedimentary material. However, these processes can produce similar variations of the carbonate C-O isotopic compositions, which means that carbonate isotopes alone cannot provide tight constraints on the alteration of kimberlite rocks. Only few carbonates in hypabyssal kimberlites show isotopic compositions consistent with abundant CO2 degassing (i.e. increasing d18O with decreasing delta C-13 values), thus implying that kimberlite magmas that are not emplaced explosively retain most of their CO2 concentrations prior to carbonate crystallisation. In kimberlitic rocks early-formed serpentine exhibits higher delta O-18 values (similar to+4-+6%) than later serpentine rims and segregations (delta O-18 values as low as similar to-2%). These variations are consistent with serpentine crystallisation from hydrous fluids derived from mixing between deuteric fluids and meteoric/hydrothermal fluids, with progressive enrichment in the latter component. Serpentine is considered to have formed under hydrothermal conditions when externally derived hydrous fluids infiltrated the cooling kimberlite volcanic system. Only limited sulphur isotopic data are available for kimberlitic bulk rocks and sulphide and sul

Glein C.R. Noble gases, nitrogen, and methane from the deep interior to the atmosphere of Titan // Icarus. 2015. Vol. 250. P. 570–586.

Titan's thick N-2-CH4 atmosphere is unlike any in the Solar System, and its origin has been shrouded in mystery for over half a century. Here, I perform a detailed analysis of chemical and isotopic data from the Cassini-Huygens mission to develop the hypothesis that Titan's (non-photochemical) atmospheric gases came from deep within. It is suggested that Titan's CH4, N-2, and noble gases originated in a rocky core buried inside the giant satellite, and hydrothermal and cryovolcanic processes were critical to the creation of Titan's atmosphere. Mass balance and chemical equilibrium calculations demonstrate that all aspects of this hypothesis can be considered geochemically plausible with respect to contemporary observational, experimental, and theoretical knowledge. Specifically, I show that a rocky core with a bulk noble gas content similar to that in CI carbonaceous meteorites would contain sufficient Ar-36 and Ne-22 to explain their reported abundances. I also show that Henry's law constants for noble gases in relevant condensed phases can be correlated with the size of their atoms, which leads to expected mixing ratios for 84Ki. (-0.2 ppbv) and 132Xe (-0.01 ppbv) that can explain why these species have yet to be detected (Huygens upper limit <10 ppbv). The outgassing of volatiles into Titan's atmosphere may be restricted by the stability of clathrate hydrates in Titan's interior. The noble gas geochemistry also provides significant new insights into the origin of Ny and CH4 on Titan, as I find that Ar and Ny, and Kr and CH4 should exhibit similar phase partitioning behavior on Titan. One implication is that over 95% of Titan's Ny may still reside in the interior. Another key result is that the upper limit from the Huygens GC-MS on the Kr/CH4 ratio in Titan's atmosphere is far too low to be consistent with accretion of primordial CH4 clathrate, which motivates me to consider endogenic production of CH4 from CO2 as a result of geochemical reactions between liquid water and anhydrous rock (i.e., serpentinization). I show that sufficient CH4 can be produced to replenish Titan's atmosphere many times over in the face of irreversible photolysis and escape of CH4, which is consistent with the favored model of episodic cryovolcanic outgassing. There should also have been enough NH3 inside Titan so that its thermal decomposition in a hot rocky core can generate the observed atmospheric Ny, and if correct this model would imply that Titan's interior has experienced vigorous hydrothermal processing. The similarity in N-14/N-16 between cometary NH3 and Titan's Ny is consistent with this picture. As for the isotopes in CH4, I show that their observed relative abundances can be explained by low-temperature (similar to 20 degrees C) equilibria with liquid water (D/H) and the expected aqueous alteration mineral calcite (C-12/C-13), provided that nickel was present to catalyze isotopic exchange over geologic timescales. The present hypothesis is chemically and isotopically consistent with the Cassini-Huygens data, and it implies that the formation of Titan's atmosphere would have been an unavoidable consequence of volatile processing that was driven by the geophysical evolution of the interior. If all of the atmospheric N-2 and CH4 have an endogenic origin, then no more than 1. 6 times the present amount of N-2 can be lost by photochemistry and escape over the history of the atmosphere; and the D/H ratio in Titan's water should be much lower than that in Enceladus' plume. Given its important implications to the origin and evolution of volatiles in the outer Solar System, we must go back to Titan to acquire additional isotopic data that will allow more rigorous tests of models of the origin of its atmosphere. I predict the following isotopic ratios: Ne-26/Ne-22 8.9 approximate to Ar-36/Ar-38 as 5.3, (N-14/N-15)NH3 as 130-170, (C-12/C-13)(CO2) 84, (D/H)H(2)o approximate to 1.7 x 10(-4); and recommend that future in situ instrumentation have t

Harris C. et al. The oxygen isotope composition of Karoo and Etendeka picrites: High delta O-18 mantle or crustal contamination? // Contrib. Mineral. Petrol. 2015. Vol. 170, № 1. P. 8.

Oxygen isotope compositions of Karoo and Etendeka large igneous province (LIP) picrites and picrite basalts are presented to constrain the effects of crustal contamination versus mantle source variation. Olivine and orthopyroxene phenocrysts from lavas and dykes (Mg# 64-80) from the Tuli and Mwenezi (Nuanetsi) regions of the ca 180 Ma Karoo LIP have delta O-18 values that range from 6.0 to 6.7 %. They appear to have crystallized from magmas having delta O-18 values about 1-1.5 % higher than expected in an entirely mantle-derived magma. Olivines from picrite and picrite basalt dykes from the ca 135 Ma Etendeka LIP of Namibia and Karoo-age picrite dykes from Dronning Maud Land, Antarctica, do not have such elevated delta O-18 values. A range of delta O-18 values from 4.9 to 6.0 %, and good correlations between delta O-18 value and Sr, Nd and Pb isotope ratios for the Etendeka picrites are consistent with previously proposed models of crustal contamination.Explanations for the high delta O-18 values in Tuli/Mwenezi picrites are limited to (1) alteration, (2) crustal contamination, and (3) derivation from mantle with an abnormally high delta O-18. Previously, a variety of models that range from crustal contamination to derivation from the 'enriched' mantle lithosphere have been suggested to explain high concentrations of incompatible elements such as K, and average epsilon Nd and epsilon Sr values of -8 and +16 in Mwenezi (Nuanetsi) picrites. However, the primitive character of the magmas (Mg# 73), combined with the lack of correlation between delta O-18 values and radiogenic isotopic compositions, MgO content, or Mg# is inconsistent with crustal contamination. Thus, an O-18-enriched mantle source having high incompatible trace element concentration and enriched radiogenic isotope composition is indicated. High delta O-18 values are accompanied by negative Nb and Ta anomalies, consistent with the involvement of the mantle lithosphere, whereas the high delta O-18 themselves are consistent with an eclogitic source. Magma delta O-18 values about 1 % higher than expected for mantle-derived magma are also a feature of the Bushveld mafic and ultra-mafic magmas, and the possibility exists that a long-lived O-18-enriched mantle source has existed beneath southern Africa. A mixed eclogite peridotite source could have developed by emplacement of oceanic lithosphere into the cratonic keel during Archaean subduction.

Hettmann K. et al. Thallium geochemistry in the metamorphic Lengenbach sulfide deposit, Switzerland: Thallium-isotope fractionation in a sulfide melt // Am. Miner. 2014. Vol. 99, № 4. P. 793–803.

The Lengenbach (Switzerland) Pb-As-Tl-Zn deposit was formed from a sulfide melt at about 500 degrees C during Alpine metamorphism, but details on its formation and especially the source of the metals are still under debate. In this study we present two sample sets to address these questions: (1) MC-ICP-MS analyses of thallium isotopes in sulfides, sulfosalts, and melt inclusions from the Alpine metamorphic Lengenbach deposit in the Binn Valley of Switzerland, the non-metamorphic Wiesloch Mississippi Valley-type deposit in Southern Germany, and the Cu- and As-rich mineralization at Pizzo Cervandone about 2 km SW of the Lengenbach deposit, which has been discussed as potential source of the Lengenbach metals. (2) LA-ICP-MS analyses of micas from the Lengenbach deposit and surrounding country rocks between the deposit and the Pizzo Cervandone to trace potential metal-bearing fluid pathways. We found that Tl isotope compositions expressed as epsilon Tl-205 values in all investigated samples range from -4.1 +/- 0.5 to + 1.9 +/- 0.5. The whole variation can be seen in the Lengenbach deposit alone, which hence records considerable fractionation even during high-temperature processes involving a sulfide melt. This large range of epsilon Tl-205 is thought to be caused by nuclear volume-dependent fractionation. Interestingly, the common fahlores at Lengenbach behave differently, from all other investigated sulfosalts: based on their heavy isotopic composition together with a low As/S-ratio, they do not seem to be crystallized from the sulfide melt, but are interpreted to have formed from hydrothermal fluids enriched in the heavy Tl isotopes. Although As mobilization in the gneisses and dolomites surrounding the Lengenbach deposit is evident based on secondary arsenites. no traces of such a country rock fluid could be found in fissure micas at Lengenbach. Hence, considerations involving K/Rb, Rb/Tl, As/S, and Pb/Tl ratios in the sulfides and micas imply that the element enrichment in the Lengenbach deposit is either pre-Alpine or related to peak metamorphism, but occurred definitely before mica growth at Lengenbach.

Hezel D.C. et al. Fe and O isotope composition of meteorite fusion crusts: Possible natural analogues to chondrule formation? // Meteorit. Planet. Sci. 2015. Vol. 50, № 2. P. 229–242.

Meteorite fusion crust formation is a brief event in a high-temperature (2000-12,000K) and high-pressure (2-5MPa) regime. We studied fusion crusts and bulk samples of 10 ordinary chondrite falls and 10 ordinary chondrite finds. The fusion crusts show a typical layering and most contain vesicles. All fusion crusts are enriched in heavy Fe isotopes, with Fe-56 values up to +0.35 parts per thousand relative to the solar system mean. On average, the Fe-56 of fusion crusts from finds is +0.23 parts per thousand, which is 0.08 parts per thousand higher than the average from falls (+0.15 parts per thousand). Higher Fe-56 in fusion crusts of finds correlate with bulk chondrite enrichments in mobile elements such as Ba and Sr. The Fe-56 signature of meteorite fusion crusts was produced by two processes (1) evaporation during atmospheric entry and (2) terrestrial weathering. Fusion crusts have either the same or higher O-18 (0.9-1.5 parts per thousand) than their host chondrites, and the same is true for O-17. The differences in bulk chondrite and fusion crust oxygen isotope composition are explained by exchange of oxygen between the molten surface of the meteorites with the atmosphere and weathering. Meteorite fusion crust formation is qualitatively similar to conditions of chondrule formation. Therefore, fusion crusts may, at least to some extent, serve as a natural analogue to chondrule formation processes. Meteorite fusion crust and chondrules exhibit a similar extent of Fe isotope fractionation, supporting the idea that the Fe isotope signature of chondrules was established in a high-pressure environment that prevented large isotope fractionations. The exchange of O between a chondrule melt and an O-16-poor nebula as the cause for theobserved nonmass dependent O isotope compositions in chondrules is supported by the same process, although to a much lower extent, in meteorite fusion crusts.

Hissler C. et al. Elucidating the formation of terra fuscas using Sr-Nd-Pb isotopes and rare earth elements // Appl. Geochem. 2015. Vol. 54. P. 85–99.

Carbonate weathering mantles, like terra fusca, are common in Europe but their formation and evolution is still badly understood. We propose to combine geological, mineralogical and pedological knowledge with trace element and isotope data of a weathering mantle as a novel approach to understand the evolution of terra fuscas. Sr-Nd-Pb isotopes and rare earth element (REE) contents were analyzed in a cambisol developing on a typical terra fusca on top of a condensed Bajocian limestone-marl succession from the eastern side of the Paris Basin. The isotope data, REE distribution patterns and mass balance calculations suggest that the cambisol mirrors the trace element enrichments present in this carbonate lithology, which are exceptionally high compared to global average carbonate. The deeper soil horizons are strongly enriched not only in REE (Sigma REE: 2640 ppm) but also in redox-sensitive elements such as Fe (44 wt.%), V (1000 ppm), Cr (700 ppm), Zn (550 ppm), As (260 ppm), Co (45 ppm) and Cd (2.4 ppm). The trace element distribution patterns of the carbonate bedrock are similar to those of the soil suggesting their close genetic relationships. Sr-Nd-Pb isotope data allow to identify four principal components in the soil: a silicate-rich pool close to the surface, a leachable REE enriched pool at the bottom of the soil profile, the limestone on which the weathering profile developed and an anthropogenic, atmosphere-derived component detected in the soil leachates of the uppermost soil horizon. The leachable phases are mainly secondary carbonate-bearing REE phases such as bastnaesite ((X) Ca(CO3)(2)F) (for X: Ce, La and Nd). The isotope data and trace element distribution patterns indicate that at least four geological and environmental events impacted the chemical and isotopical compositions of the soil system: 1. An oxygen-deficient diagenetic or hydrothermal event caused trace metal enrichments in the Bajocian lime-stone- marls. 2. Carbonate dissolution caused the enrichment of detrital silicate phases and authigenic REE-bearing residual phases - e.g. marine authigenic fluorapatites and bastnaesite - in the newly formed condensed horizons. 3. Dissolution/precipitation of metastable bastnaesite phases and downward migration of the REE during soil formation. 4. Overprinting of the chemical and isotopical compositions of the uppermost soil horizon by recent atmospheric depositions.

Holst J.C. et al. Tungsten isotopes in bulk meteorites and their inclusions-Implications for processing of presolar components in the solar protoplanetary disk // Meteorit. Planet. Sci. 2015. Vol. 50, № 9. P. 1643–1660.

We present high precision, low-and high-resolution tungsten isotope measurements of iron meteorites Cape York (IIIAB), Rhine Villa (IIIE), Bendego (IC), and the IVB iron meteorites Tlacotepec, Skookum, and Weaver Mountains, as well as CI chondrite Ivuna, a CV3 chondrite refractory inclusion (CAI BE), and terrestrial standards. Our high precision tungsten isotope data show that the distribution of the rare p-process nuclide W-180 is homogeneous among chondrites, iron meteorites, and the refractory inclusion. One exception to this pattern is the IVB iron meteorite group, which displays variable excesses relative to the terrestrial standard, possibly related to decay of rare Os-184. Such anomalies are not the result of analytical artifacts and cannot be caused by sampling of a protoplanetary disk characterized by p-process isotope heterogeneity. In contrast, we find that W-183 is variable due to a nucleosynthetic s-process deficit/r-process excess among chondrites and iron meteorites. This variability supports the widespread nucleosynthetic s/r-process heterogeneity in the protoplanetary disk inferred from other isotope systems and we show that W and Ni isotope variability is correlated. Correlated isotope heterogeneity for elements of distinct nucleosynthetic origin (W-183 and Ni-58) is best explained by thermal processing in the protoplanetary disk during which thermally labile carrier phases are unmixed by vaporization thereby imparting isotope anomalies on the residual processed reservoir.

Horton T.W., Oze C. Are two elements better than one? Dual isotope-ratio detrending of evaporative effects on lake carbonate paleoelevation proxies // Geochem. Geophys. Geosyst. 2012. Vol. 13, №6. P. Q0AK05 (№ статьи).

Stable isotope-based proxy methods enhance our ability to interpret geodynamical histories for tectonic provinces via paleoelevational reconstructions. These methods require that the unmodified isotopic composition of meteoric water is recorded by authigenic minerals, a critical assumption that has not been tested across wide-ranging environmental and topographical contexts. Here, we show that Quaternary lake carbonate delta O-18 values are not strongly, nor significantly, correlated with regional elevation due to the isotopic modification of in-flow waters following entry into the lake environment. These modifications are largely caused by surface water evaporation, and can result in >3 km errors in paleoelevation estimates if not accounted for. However, our analysis suggests that positive shifts in surface water delta O-18 are accompanied by similar magnitude shifts in delta C-13-DIC. This positive co-variation in delta O-18 and delta C-13 may be used to detrend lake carbonate compositions for the effects of surface water evaporation using a parameter we define here as the 'C-13-excess'. When Tibetan lakes are excluded from the data set, C-13-excess values are significantly correlated with mean up-slope hypsometric altitude with an error of +/- 500 m. Application of the C-13-excess approach to Cenozoic lake carbonate records from the western U. S. Cordillera both challenges and reinforces previous paleoelevational interpretations based on delta O-18 alone.

Howell D. et al. A spectroscopic and carbon-isotope study of mixed-habit diamonds: Impurity characteristics and growth environment // Am. Miner. 2013. Vol. 98, № 1. P. 66–77.

Mixed-habit diamonds have experienced periods of growth where they were bounded by two surface forms at the same time. Such diamonds are relatively rare and therefore under-investigated. Under certain physical and chemical conditions, smooth octahedral faces grow concurrently with rough, hummocky cuboid faces. However, the specific conditions that cause this type of growth are unknown. Here we present a large array of spectroscopic data in an attempt to investigate the impurity and carbon-isotope characteristics, as well as growth conditions, of 13 large (>6 mm diameter) plates cut from mixed-habit diamonds. The diamonds all generally have high nitrogen concentrations (>1400 ppm), with the octahedral sectors enriched by 127-143% compared to their contemporary cuboid sectors. Levels of nitrogen aggregation are generally low (2-23% IaB) with no significant difference between sectors. IR-active hydrogen features are predominantly found in the cuboid sectors with only very small bands in the octahedral sectors. Platelet characteristics are variable; only one sample shows a large B' band intensity in the octahedral sector, with no platelets occurring in the cuboid sector. Other samples either show a small B' band in both sectors, or just in the cuboid sector, or none at all. These data support a model that shows the concentration-adjusted aggregation rate of nitrogen to be the same in both sectors, whereas the subsequent platelet development is reduced in the cuboid sectors. This is because the interstitial carbon atoms have interacted with disk-crack-like defects only found in cuboid sectors, which in turn reduces their chances of aggregating to form platelets. These disk-crack-like defects are also thought to be the most likely site for the IR-active hydrogen features and they maybe intrinsic to cuboid growth in mixed-habit diamonds. When they are graphitized, as they are in all of the diamonds in this study, this may reflect a heating event prior to volcanic exhumation. Spectroscopic analysis of the green cathodoluminescence exhibited by all of the diamonds shows nickel centers to be present in only the cuboid sectors. Carbon isotope data, obtained by secondary ion mass spectrometry, show very little variation in seven of the diamonds. The total range of 217 analyses is -7.94 to -9.61 (+/- 0.15)parts per thousand, and the largest variation in a single stone is 0.98 parts per thousand. No fractionation in carbon isotopes is seen between octahedral and cuboid sectors at the same growth horizon. These data suggest that the source fluid chemistry, as well as pressure, temperature, and oxygen fugacity were very stable over time, allowing such large volumes of mixed-habit growth to occur. The high concentration of impurities, namely nitrogen and hydrogen, is probably the critical factor required to cause mixed-habit growth. The impurity and isotopic data fall in line with previous modeling based on diamond growth from reduced carbonates with the loss of a C-13-enriched CO2 component.

Huy N.Q. et al. Self-absorption correction in determining the 238U activity of soil samples via 63.3 keV gamma ray using MCNP5 code // Applied Radiation and Isotopes. 2013. Vol. 71, № 1. P. 11–20.

The essential issue in analyzing the activity of 238U in an HPGe detector based gamma spectrometer via 63.3 keV line is relating to the strong self-absorption of this weak gamma ray in sample material. The present work suggests a method of the self-absorption corrections for 63.3 keV gamma rays by a combination of experimental measurements and Monte Carlo MCNP5 calculations. The effects of sample chemical composition, density and geometry were calculated in terms of self-attenuation factors. The method, developed for a cylindrical sample geometry, accounted for variable sample heights and densities. The analysis of 238U activity was applied for three main soil types in Vietnam, which are grey, alluvial and red soils. The results obtained with the above outlined method were in good agreement with those derived by other methods.

Ilina S.M. et al. Extreme iron isotope fractionation between colloids and particles of boreal and temperate organic-rich waters // Geochim. Cosmochim. Acta. 2013. Vol. 101. P. 96–111.

Significant and systematic variations of iron isotopic composition in surface water sample fractions obtained by frontal cascade filtration and ultrafiltration have been recorded in (1) subarctic organic-rich boreal river and stream, mire, lake and soil solutions in northern taiga zone (Karelia, NW Russia) and (2) temperate river and lake waters of the southern boreal zone (Central Russia). Water samples were filtered in the field employing progressively decreasing pore size from 100 mu m to 1 kDa followed by iron isotope analysis. In all river samples, there was a gradual increase of delta Fe-57 relative to IRMM-14 with decreasing pore size, from +0.4 +/- 0.1 parts per thousand at 100 mu m up to +4.2 +/- 0.1 parts per thousand at 10 kDa fraction in the subarctic zone and from -0.024 +/- 0.2 parts per thousand at 100 mu m up to +1.2 +/- 0.2 parts per thousand at 10 kDa in the temperate zone. In the series of filtrates/ultrafiltrates of subarctic and temperate streams and rivers, the delta Fe-57 value decreases with increasing molar Fe/C-org ratio. Therefore, small-size, Fe-poor, C-rich colloids (1-10 kDa) and Low Molecular Weight (LMW) fractions of oxygenated water exhibit strong enrichment in heavy isotope whereas High Molecular Weight Fe-rich colloids (100 kDa-0.22 mu m) and particles (1-100 mu m) are isotopically lighter and closer to the continental crust Fe isotope composition. The relative enrichment of 1-10 kDa ultrafiltrates in heavy isotopes suggests that low molecular weight ligands bind Fe more strongly (Fe-O-C bonds) than Fe(III)oxy(hydr)oxides (Fe-O-Fe bonds), in accord with quantum mechanics principles. Highly positive delta Fe-57 of the LMW fraction of labile and potentially bioavailable Fe in small subarctic rivers may turn out to be a very important source of isotopically heavy Fe in the Arctic Ocean. The mechanisms involved in the production of this isotopically heavy Fe may lead this tracer to become a new indicator of environmental changes occurring in the boreal zone.

Ji Y.-Y. et al. Analytical evaluation of natural radionuclides and their radioactive equilibrium in raw materials and by-products // Applied Radiation and Isotopes. 2015. Vol. 97. P. 1–7. 1.Ji Y.-Y. et al. Analytical evaluation of natural radionuclides and their radioactive equilibrium in raw materials and by-products // Applied Radiation and Isotopes. 2015. Vol. 97. P. 1–7.

An investigation into the distribution of natural radionuclides and radioactive secular equilibrium in raw materials and by-products in a domestic distribution was conducted to deduce the optimum conditions for the analytical evaluation of natural radionuclides for 238U, 226Ra, and 232Th using a gamma-ray spectrometer and inductively coupled plasma mass spectrometer (ICP-MS). The range of the specific activities of natural radionuclides was first evaluated by analyzing 228Ac and 214Bi, which are 232Th and 226Ra indicators, respectively, in about 100 samples of raw materials and by-products through a gamma-ray spectrometer. From further experiments using several samples selected based on the results of the distribution of natural radionuclides, the validation of their analytical evaluations for the indirect measurements using a gamma-ray spectrometer and direct measurements using ICP-MS was assured by comparing their results. Chemically processed products from the raw materials, such as Zr sand and ceramic balls, were generally shown for the type of bead and particularly analyzed showing a definite disequilibrium with above a 50% difference between 238U and 226Ra in the uranium series and 232Th and 228Ra in the thorium series.

Keith M. et al. Systematic variations of trace element and sulfur isotope compositions in pyrite with stratigraphic depth in the Skouriotissa volcanic-hosted massive sulfide deposit, Troodos ophiolite, Cyprus // Chem. Geol. 2016. Vol. 423. P. 7–18.

The Troodos ophiolite represents one of the best-preserved fossil analogs of modern oceanic crust and includes numerous volcanic-hosted massive sulfide deposits. The Skouriotissa deposit can be separated into a stockwork ore zone and an overlying massive sulfide lens that is covered by metalliferous sediments representing the former sulfide-seawater interface. Pyrite is the dominant sulfide mineral within these ores. The trace element composition of pyrite varies systematically with stratigraphic depth (down to similar to 150 mbsf) probably reflecting fluid temperature variations and effects of phase separation (Co, Ni, Se, Te, Bi and Cu). Metal remobilization due to hydrothermal zone refining (Zn, Sb and Pb) and fluid-seawater mixing at the seafloor (Mo) represent further important processes controlling the pyrite chemistry. Massive sulfide-hosted sphalerite and euhedral pyrite probably formed from hot fluids (similar to 400 degrees C), while the occurrence of colloform pyrite indicates lower precipitation temperatures (<400 degrees C). Similar delta O-18 quartz-fluid equilibration temperatures (similar to 400 degrees C) in the stockwork zone suggest that the Skouriotissa fluids did not cool significantly during the final 150mof fluid ascent to the seafloor. The delta S-34 composition of deep stockwork pyrite (-1.4 parts per thousand) suggests that an isotopically light magmatic volatile phase (<0 parts per thousand) was added to the hydrothermal system of Skouriotissa. During further fluid ascent about 38% of Cretaceous seawater (delta S-34 = 18-19 parts per thousand) was added leading to the precipitation of stockwork pyrite with positive delta S-34 values (6.1 parts per thousand). In addition, the chemical and textural similarities between Skouriotissa and modern seafloor vent systems and massive sulfide deposits suggest that the Skouriotissa hydrothermal system has a modern analog.

Khanchuk A.I., Plyusnina L.P., Berdnikov N.V. Noble metal and graphite formation in metamorphic rocks of the Khanka terrane, Far East Russia // J. Asian Earth Sci. 2015. Vol. 99. P. 30–40.

Noble metal-graphite mineralization has been identified in the Riphean-Cambrian metamorphic complexes of the northern Khanka terrane, Russia. The graphite mineralization is hosted in magmatic and sedimentary rocks metamorphosed under greenschist to granulite facies conditions. This paper provides the results of our study of the Turgenevo-Tamga graphite deposits. This study analyzes the geochemistry of the noble metals with the aim of determining the spatial relationships between noble metals and graphite. The graphitized rocks, analyzed by various geochemical methods, show a wide range of noble metal concentrations (ppm): Pt (0.02-62.13), Au (0.02-26), Ag (0.56-4.41), Pd (0.003-5.67), Ru (0.007-0.2), Rh (0.001-0.74), Ir (0.002-0.55), and Os (0.011-0.09). Crystallization from gas-condensates is indicated by the relationships between the noble metal mineralization and the graphite, and in particular the inhomogeneous distribution of graphite in the rocks, the inhomogeneous distribution of metals in the graphite, the microglobular graphite structures, and the carbon isotopic compositions. Thermal analysis and Raman spectroscopy indicate that some of the graphite formed from the metamorphism of sedimentary biogenic carbonaceous matter. The uneven distribution of noble metals in the rocks, and the compositional variability of the mineralization, implies that the origin of the metals was largely related to endogenic processes involving reduced fluids derived from depth. Our conclusion is that the noble metals and graphite mainly originated from magmatic fluids, but that some material was derived from exogenic and metamorphic sources.

Kotarba M.J., Nagao K., Karnkowski P.H. Origin of gaseous hydrocarbons, noble gases, carbon dioxide and nitrogen in Carboniferous and Permian strata of the distal part of the Polish Basin: Geological and isotopic approach // Chem. Geol. 2014. Vol. 383. P. 164–179.

Sixteen natural gas samples collected from Pennsylvanian and Permian (Rotliegend and Zechstein Limestone) strata of the distal part of the Polish Basin in Wielkopolska and Lower Silesia were analysed for molecular composition and stable carbon isotope composition of hydrocarbons (CH4, C2H6, C3H8, n-C4H10 and i-C4H10) and CO2, stable hydrogen isotope composition of methane, stable nitrogen isotope composition of N-2, and stable isotope composition of noble gases (He, Ne, Ar, Kr, and Xe). Thirteen of analysed hydrocarbon gases reveal complete [delta C-13(CH4) > delta C-13(C2H6) > delta C-13(C3H8)] and partial inversed isotopic trends from methane to propane thus they have a very complicated generation, migration and accumulation history and range of their source rock horizons. Two source rock horizons occur NE from Wolsztyn Ridge. They contain mixed types III/II and II/III kerogens of Pennsylvanian age and Mississippian and/or Devonian age, respectively. One source rock horizon occurs SW from Wolsztyn Ridge. It contains type III and mixed type III/II kerogens of Pennsylvanian age. The kerogens in all source rock horizons generated gaseous hydrocarbons at two separate maturity stages: about 0.5 to 0.8% in vitrinite reflectance scale at the first maturity stage, and over 1.3% in vitrinite reflectance scale at the second maturity stage. High concentrations of He in analysed gases are mostly a product of a-decay of U and Th enriched in crustal materials. A small contribution of He and Ne of mantle origin to the gas reservoirs was inferred. Radiogenic He-4/Ar-40 ratios are higher than the average production rate ratio of about 5 for crustal materials, which might have been caused by a selective supply of lighter He through crustal rocks surrounding the gas reservoirs, or higher (U + Th)/K ratio than the crustal average. CO2 from analysed gases was mainly generated during thermogenic processes of transformation of organic matter, although some gases can contain components from endogenic processes and from thermal destruction of Zechstein Limestone and probably Precambrian carbonates. N-2 was mainly generated during thermal transformation of organic matter and had a large component released from NH4-rich illites. Very high N-2/Ar-40 for the gases might be caused by accelerated thermogenic production of N-2 under the condition of high heat flux from volcanic activity at late Pennsylvanian and early Permian age. Deep-seated faults, mainly framing the Wolsztyn Ridge, perform important role in migration and mixed in different proportions of noble gases originated from upper mantle and from mineralisation by radioactive minerals their fault surfaces and occurrence of Pennsylvanian-Lower Permian volcanites in crust as well as hydrocarbon gases, CO2 and N-2, also from thermal destruction of NH4-rich illites, from "gas generation kitchens" of source rock horizons to the traps.

Kovaltsov G.A., Mishev A., Usoskin I.G. A new model of cosmogenic production of radiocarbon C-14 in the atmosphere // Earth Planet. Sci. Lett. 2012. Vol. 337. P. 114–120.

We present the results of full new calculation of radiocarbon C-14 production in the Earth atmosphere, using a numerical Monte-Carlo model. We provide, for the first time, a tabulated C-14 yield function for the energy of primary cosmic ray particles ranging from 0.1 to 1000 GeV/nucleon. We have calculated the global production rate of C-14, which is 1.64 and 1.88 atoms/cm(2)/s for the modern time and for the pre-industrial epoch, respectively. This is close to the values obtained from the carbon cycle reservoir inventory. We argue that earlier models overestimated the global C-14 production rate because of outdated spectra of cosmic ray heavier nuclei. The mean contribution of solar energetic particles to the global C-14 is calculated as about 0.25% for the modern epoch. Our model provides a new tool to calculate the C-14 production in the Earth's atmosphere, which can be applied, e.g., to reconstructions of solar activity in the past.

Kozlik M., Gerdes A., Raith J.G. Strontium isotope systematics of scheelite and apatite from the Felbertal tungsten deposit, Austria - results of in-situ LA-MC-ICP-MS analysis // Mineral. Petrol. 2016. Vol. 110, № 1. P. 11–27.

The in-situ Sr isotopic systematics of scheelite and apatite from the Felbertal W deposit and a few regional Variscan orthogneisses ("Zentralgneise") have been determined by LA-MC-ICP-MS. The Sr-87/Sr-86 ratios of scheelite and apatite from the deposit are highly radiogenic and remarkably scattering. In the early magmatic-hydrothermal scheelite generations (Scheelite 1 and 2) the Sr-87/Sr-86 ratios range from 0.72078 to 0.76417 and from 0.70724 to 0.76832, respectively. Metamorphic Scheelite 3, formed by recrystallisation and local mobilisation of older scheelite, is characterised by even higher Sr-87/Sr-86 values between 0.74331 and 0.80689. Statistics allows discriminating the three scheelite generations although there is considerable overlap between Scheelite 1 and 2; they could be mixtures of the same isotopic reservoirs. The heterogeneous and scattering Sr-87/Sr-86 ratios of the two primary scheelite generations suggest modification of the Sr isotope system due to fluid-rock interaction and isotopic disequilibrium. Incongruent release of Sr-87 from micas in the Early Palaeozoic host rocks of the Habach Complex contributed to the solute budget of the hydrothermal fluids and may explain the radiogenic Sr isotope signature of scheelite. Spatially resolved analyses revealed isotopic disequilibrium even on a sub-mm scale within zoned Scheelite 2 crystals indicating scheelite growth in an isotopic dynamical hydrothermal system. Zoned apatite from the W mineralised Early Carboniferous K1-K3 orthogneiss in the western ore field yielded Sr-87/Sr-86 of 0.72044-0.74514 for the cores and 0.74535-0.77937 for the rims. Values of magmatic apatite cores from the K1-K3 orthogneiss are comparable to those of primary Scheelite 1; they are too radiogenic to be magmatic. The Sr isotopic composition of apatite cores was therefore equally modified during the hydrothermal mineralisation processes, therefore supporting the single-stage genetic model in which W mineralisation is associated with the intrusion of the K1-K3 metagranitoid at Felbertal. The subsequent regional metamorphic overprint of the deposit caused redistribution of Sr-87 as a consequence of metamorphic reactions involving Rb and Sr-bearing minerals. Metamorphic Scheelite 3 and apatite rims (e.g., in the K1-K3 orthogneiss) generally became more radiogenic during this process. However, local recrystallisation of primary scheelite under closed conditions (without addition of Sr-87 by the metamorphic fluid) is also documented. The latter process resulted in a homogenisation of the isotope composition of Scheelite 3. Further increase in Sr-87/Sr-86 ratios in Scheelite 3 and apatite rims is attributed to Late Alpine (?) metamorphic recrystallisation and redistribution of Sr-87 by metamorphic fluids.

Kuleshova A.I. et al. Possible influence of climate factors on the reconstruction of the cosmogenic isotope C-14 production rate in the earth’s atmosphere and solar activity in past epochs // Geomagn. Aeron. 2015. Vol. 55, № 8. P. 1071–1075.

The paper considers the probable influence of variations of the global temperature and carbon dioxide concentration in the Earth's atmosphere on the results of reconstruction of the production rate of the cosmogenic isotope C-14 in the terrestrial atmosphere for the period from the early 15th to the mid 19th century. This time interval covers the Sporer, Maunder, and Dalton minima of solar activity, as well as the Little Ice Age. It was shown that the climate changes that occurred during the Little Ice Age should be taken into account. In the Maunder and Sporer minima of solar activity, the C-14 generation rate may be comparable to the values for the Dalton minimum, while exclusion of the climate effect yields extremely large values of the C-14 production rate for these grand minima. In the solar activity reconstruction for past epochs, this circumstance should be taken into consideration via measurements of the C-14 concentration on a long time scale.

Leppanen A.-P. et al. Cosmogenic Be-7 and Na-22 in Finland: Production, observed periodicities and the connection to climatic phenomena // J. Atmos. Sol.-Terr. Phys. 2012. Vol. 74. P. 164–180.

This study presents theoretical production calculations and time series analyses of two cosmogenic isotopes, Be-7 and Na-22, from the four high-latitude stations of Kotka, Kajaani, Rovaniemi and Ivalo located in Finland. We used published results for Be-7 but performed full simulations of the Na-22 production in atmosphere. For the first time, lookup tables of Na-22 production by cosmic rays in the atmosphere are presented. In conjunction with calculations using the new model of Na-22 production, the Be-7/Na-22 ratios in the atmosphere were also calculated. The wavelet transform of the Be-7 and Na-22 time series revealed sets of periodicities in the 2.5-8 year range. The wavelet coherence method was used to study coherences between Be-7 and Na-22 and Be-7/Na-22 data and AO, NAO, AMO, QBO and SO teleconnection indices representing different climatic variations in Northern Europe. In the wavelet coherence analyses, the Be-7 activities were found to be mainly modulated by NAO and AMO at an interannual scale, while Na-22 activity was found to be less effected by climatic phenomena. The Be-7 coherence with other indices was intermittent where the coherence with SO was limited to Ivalo data and in the case of QBO, to Kotka data. The Na-22 data was not found to be in coherence with any of the studied indices. In the Be-7/Na-22 ratio a clear seasonal pattern was observed where low Be-7/Na-22 ratios were observed during summer and high ratios during winter. This was speculated to be caused by the height of atmospheric vertical mixing. During 2006-2011, the Be-7/Na-22 ratios from Kotka, Kajaani and Rovaniemi showed variance at synoptic time scales but were nearly identical at the seasonal scale. The Be-7/Na-22 ratio was proposed to be a radiochronometer to estimate residence times of aerosols carrying Be-7 and Na-22.

Leybourne M.I. et al. Stable isotopic composition of soil calcite (O, C) and gypsum (S) overlying Cu deposits in the Atacama Desert, Chile: Implications for mineral exploration, salt sources, and paleoenvironmental reconstruction // Applied Geochemistry. 2013. Vol. 29. P. 55–72.

Soils overlying two porphyry Cu deposits (Spence, Gaby Sur) and the Pampa del Tamarugal, Atacama Desert, Northern Chile were collected in order to investigate the extent to which saline groundwaters influence “soil” chemistry in regions with thick Miocene and younger sediment cover. Soil carbonate (calcite) was analyzed for C and O isotopes and pedogenic gypsum for S isotopes. Soil calcite is present in all soils at the Spence deposit, but increases volumetrically above two fracture zones that cut the Miocene gravels, including gravels that overlie the deposit. The C isotope composition of carbonate from the soils overlying fracture zones is indistinguishable from pedogenic carbonate elsewhere at the Spence deposit; all ?13CVPDB values fall within a narrow range (1.40–4.23‰), consistent with the carbonate having formed in equilibrium with atmospheric CO2. However, ?18OVPDB for carbonate over both fracture zones is statistically different from carbonate elsewhere (average ?18OVPDB = 0.82‰ vs. ?2.23‰, respectively), suggesting involvement of groundwater in their formation. The composition of soils at the Tamarugal anomaly has been most strongly affected by earthquake-related surface flooding and evaporation of groundwater; ?13CVPDB values (?4.28‰ to ?2.04‰) are interpreted to be a mixture of dissolved inorganic C (DIC) from groundwater and atmospheric CO2. At the Spence deposit, soils only rarely contain sufficient SO4 for S isotope analysis; the SO4-bearing soils occur only above the fracture zones in the gravel. Results are uniform (3.7–4.9‰ ?34SCDT), which is near the middle of the range for SO4 in groundwater (0.9–7.3‰). Sulfur in soils at the Gaby Sur deposit (3.8–6.1‰ ?34SCDT) is dominated by gypsum, which primarily occurs on the flanks and tops of hills, suggesting deposition from SO4-rich fogs. Sulfate in Gaby Sur deposit gypsum is possibly derived by condensation of airborne SO4 from volcanic SO2 from the nearby Andes. At the Gaby Sur deposit and Tamarugal anomaly, pedogenic stable isotopes cannot distinguish between S from porphyry or redeposited SO4 from interior salars. The three sites studied have had different histories of salt accumulation and display variable influence of groundwater, which is interpreted to have been forced to the surface during earthquakes. The clear accumulation of salts associated with fractures at the Spence deposit, and shifts in the isotopic composition of carbonate and sulfate in the fractures despite clear evidence of relatively recent removal of salts indicates that transfer from groundwater is an ongoing process. The interpretation that groundwaters can influence the isotopic composition of pedogenic calcrete and gypsum has important implications for previous studies that have not considered this mechanism.

Liu S. et al. First-principles study of sulfur isotope fractionation in pyrite-type disulfides // Am. Miner. 2015. Vol. 100, № 1. P. 203–208.

The sulfides are an important group of minerals. As a geochemical tracer, the sulfur isotope fractionation in sulfides can be used to analyze the ore-forming process and the ore-forming material source. Fe, Co, Ni, and Mn are the first row transition metals, and pyrite (FeS2), cattierite (CoS2), vaesite (NiS2), and hauerite (MnS2) crystallize in the pyrite-type structure. However, there are few studies on the sulfur isotope fractionation in these disulfides. So studying the isotope fractionation between them provides the opportunity to examine the various members of a structural group in which only the metal atom is changed, thereby providing information that permits a systematic development of concepts regarding sulfur isotope fractionation in transition-metal disulfides. In the present paper, the sulfur isotope fractionation parameters for pyrite, cattierite, vaesite, and hauerite with the pyrite-type structure have been calculated using first-principles methods based on density functional theory in the temperature range of 0-1000 degrees C. The structure parameters of these four minerals and the vibration frequencies of pyrite are in good agreement with previous experimental values. The metal-sulfur distance increases in the order FeS2, CoS2, NiS2, and MnS2, the sulfur-sulfur distance decreases in the order FeS2, CoS2, MnS2, and NiS2, these two sequences agree with the experimental results. Our calculations show that the order of heavy isotope enrichment is pyrite > cattierite > vaesite > hauerite. It seems that the sulfur isotope fractionation in disulfides depends mainly on the metal-sulfur bonds.

Liu W. et al. Carbon isotope composition of long chain leaf wax n-alkanes in lake sediments: A dual indicator of paleoenvironment in the Qinghai-Tibet Plateau // Org. Geochem. 2015. Vol. 83–84. P. 190–201.

The carbon isotope composition (delta C-13 values) of long chain n-alkanes in lake sediments has been considered a reliable means of tracking changes in the terrigenous contribution of plants with C-3 and C-4 photosynthetic pathways. A key premise is that long chain leaf wax components used for isotope analysis are derived primarily from terrigenous higher plants. The role of aquatic plants in affecting delta C-13 values of long chain n-alkanes in lacustrine sediments may, however, have long been underestimated. In this study, we found that a large portion of long chain n-alkanes (C-27 and C-29) in nearshore sediments of the Lake Qinghai catchment was contributed by submerged aquatic plants, which displayed a relatively positive carbon isotope composition (e.g. -26.7% to -15.7% for C-29) similar to that of terrestrial C-4 plants. Thus, the use of delta C-13 values of sedimentary C-27 and C-29 n-alkanes for tracing terrigenous vegetation composition may create a bias toward significant overestimation/underestimation of the proportion of terrestrial C-4 plants. For sedimentary C-31, however, the contribution from submerged plants was minor, so that the delta C-13 values for C-31 n-alkane in surface sediments were in accord with those of the modern terrestrial vegetation in the Lake Qinghai region. Moreover, we found that changes in the delta C-13 values of sedimentary C-27 and C-29 n-alkanes were closely related to water depth variation. Downcore analysis further demonstrated the significant influence of endogenous lipids in lake sediments for the interpretation of terrestrial C-4 vegetation and associated environment/climate reconstruction. In conclusion, our results suggest that the delta C-13 values of sedimentary long chain n-alkanes (C-27, C-29 and C-31) may carry different environmental signals. While the delta C-13 values of C-31 were a reliable proxy for C-4/C-3 terrestrial vegetation composition, the delta C-13 values of C-27 and C-29 n-alkanes may have recorded lake ecological conditions and sources of organic carbon, which might be affected by lake water depth.

Loewen M.W., Bindeman I.N. Oxygen isotope and trace element evidence for three-stage petrogenesis of the youngest episode (260-79 ka) of Yellowstone rhyolitic volcanism // Contrib. Mineral. Petrol. 2015. Vol. 170, № 4. P. 39.

We report the first high-precision delta O-18 analyses of glass, delta O-18 of minerals, and trace element concentrations in glass and minerals for the 260-79 ka Central Plateau Member (CPM) rhyolites of Yellowstone, a > 350 km(3) cumulative volume of lavas erupted inside of 630 ka Lava Creek Tuff (LCT) caldera. The glass analyses of these crystal-poor rhyolites provide direct characterization of the melt and its evolution through time. The delta O-18(glass) values are low and mostly homogeneous (4.5 +/- 0.14 %) within and in between lavas that erupted in four different temporal episodes during 200 ka of CPM volcanism with a slight shift to lower delta O-18 in the youngest episode (Pitchstone Plateau). These values are lower than Yellowstone basalts (5.7-6 %), LCT (5.5 %), pre-, and extracaldera rhyolites (similar to 7-8 %), but higher than the earliest 550-450 ka post-LCT rhyolites (1-2 %). The glass delta O-18 value is coupled with new clinopyroxene analyses and previously reported zircon analyses to calculate oxygen isotope equilibration temperatures. Clinopyroxene records > 900 degrees C near-liquidus temperatures, while zircon records temperatures < 850 degrees C similar to zircon saturation temperature estimates. Trace element concentrations in the same glass analyzed for oxygen isotopes show evidence for temporal decreases in Ti, Sr, Ba, and Eu-related to Fe-Ti oxide and sanidine (similar to quartz) crystallization control, while other trace elements remain similar or are enriched through time. The slight temporal increase in glass Zr concentrations may reflect similar or higher temperature magmas (via zircon saturation) through time, while previosuly reported temperature decreases (e. g., Ti-in-quartz) might reflect changing Ti concentrations with progressive melt evolution. Multiple analyses of glass across single samples and in profiles across lava flow surfaces document trace element heterogeneity with compatible behavior of all analyzed elements except Rb, Nb, and U. These new data provide evidence for a three-stage geochemical evolution of these most recent Yellowstone rhyolites: (1) repeated batch melting events at the base of a homogenized low-delta O-18 intracaldera fill resulting in liquidus rhyolite melt and a refractory residue that sequesters feldspar-compatible elements over time. This melting may be triggered by conductive "hot plate" heating by basaltic magma intruding beneath the Yellowstone caldera resulting in contact rhyolitic melt that crystallizes early clinopyroxene and/or sanidine at high temperature. (2) Heterogeneity within individual samples and across flows reflects crystallization of these melts during preeruptive storage of magma at at lower, zircon-saturated temperatures. Compatible behavior and variations of most trace elements within individual lava flows are the result of sanidine, quartz, Fe-Ti oxide, zircon, and chevkinite crystallization at this stage. (3) Internal mixing immediately prior to and/or during eruption disrupts, these compositional gradients in each parental magma body that are preserved as melt domains distributed throughout the lava flows. These results based on the most recent and best-preserved volcanic products from the Yellowstone volcanic system provide new insight into the multiple stages required to generate highly fractionated hot spot and rift-related rhyolites. Our proposed model differs from previous interpretations that extreme Sr and Ba depletion result from long-term crystallization of a single magma body-instead we suggest that punctuated batch melting events generated a sanidine-rich refractory residue and a melt source region progressively depleted in Sr and Ba

Loewen M.W., Bindeman I.N. Oxygen isotope thermometry reveals high magmatic temperatures and short residence times in Yellowstone and other hot-dry rhyolites compared to cold-wet systems // Am. Miner. 2016. Vol. 101, № 5–6. P. 1222–1227.

The eruption and storage temperatures of rhyolitic magmas are critical factors for understanding the mechanisms of their eruption and petrogenesis. Temperatures are particularly important when comparing the magmatic histories of hot-dry rhyolites from the Yellowstone-Snake River Plain (YSRP) and Iceland to cold-wet rhyolites such as the Bishop Tuff. Here we employ mineral pair oxygen isotope fractionations for estimating rhyolite temperatures independent of pressure and other compositional factors. We report high precision oxygen isotope analyses of quartz, pyroxene, magnetite, and zircon that we use to estimate crystallization and storage temperatures. Temperatures for YSRP and Icelandic rhyolites are highest for quartz-magnetite and quartz-clinopyroxene (similar to 950 degrees C), with lower quartz-zircon (850 degrees C) temperatures that are similar to estimates of zircon saturation. The magnitude and pattern of these temperatures is consistent with crystallization from near-liquidus rhyolites. In contrast, oxygen isotope temperatures calculated for the Bishop and other "cold-wet" type tuffs define low similar to 760 degrees C temperatures for all three mineral pairs consistent with prolonged mineral residence at near-solidus conditions. Preservation of a down-temperature crystallization sequence of hot magnetite and clinopyroxene with colder zircon in hot-dry YSRP and Icelandic rhyolites suggest <1000 yr magma residence, where magnetite does not have sufficient time to diffusively equilibrate oxygen in a lower temperature melt. This is consistent with recently determined high precision U-Pb crystallization ages zircons from the same units indicating magma generation shortly before eruption.

McFarlane C.R.M., McKeough M. Petrogenesis of the Kulyk Lake monazite-apatite-Fe(Ti)-oxide occurrence revealed using in-situ LA-(MC)-ICP-MS trace element mapping, U-Pb dating, and Sm-Nd isotope systematics on monazite // Am. Miner. 2013. Vol. 98, № 10. P. 1644–1659.

The high-grade metamorphic metasedimentary rocks that comprise the Wollaston Domain, northern Saskatchewan, are host to numerous REE-mineralized pegmatite bodies, including the Kulyk Lake monazite-apatite-Fe(Ti)-oxide occurrence. This occurrence, which is defined by a 3-5 cm wide sinouous zone of granoblastic monazite, apatite, and titanomagnetite, is enclosed within aplitic monzonite and granitic pegmatite dikes. Monazite in this dike was studied in detail using in situ laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and LA-multi-collector (MC)-ICP-MS. A combination of in situ LA-ICP-MS trace element mapping, trace-element quantification, and U-Pb dating were used to identify a significant volume of partial resorbed xenocyrstic monazite and zircon cores within the monazite-apatite-Fe(Ti)-oxide zone. This xenocrystic monazite is locally characterized by anomalously high As, V, Mo, and Eu concentrations and high (LaNb)(CN) (i.e., >1000) consistent with their derivation from metalliferous black shales. The U-Pb age distribution of the inherited monazite and zircon populations matches that of the middle- to upper-Wollaston Group sedimentary succession. The latter was confirmed by in situ Sm-Nd isotope systematics measured by LA-MC-ICP-MS that yielded epsilon Nd-(1830Ma) between -5.0 and -5.7 consistent with derivation from Wollaston Group metasediment. The crystallization of similar to 1830 Ma anatectic overgrowths on xenocrystic cores is indistinguishable from monazite crystallization in the aplitic monzonite dike hosting the monazite-apatite-Fe(Ti)-oxide bodies. This study reveals the potential importance of metalliferous monazite-rich lithologies in the anatectic zone to these pegmatite-hosted REE occurrences and suggests that entrainment and magmatic segregation mechanisms may have helped to concentrate monazite, apatite, and Fe(Ti)-oxide prior to final emplacement of the aplite-pegmatite dikes. Similar processes may have occurred regionally and in other high-grade metamorphic terrains worldwide that are endowed with metalliferous metasedimentary protoliths.

Mikhail S., Howell D. A petrological assessment of diamond as a recorder of the mantle nitrogen cycle // Am. Miner. 2016. Vol. 101, № 3–4. P. 780–787.

Nitrogen is fundamental to the evolution of Earth and the life it supports, but for reasons poorly understood, it is cosmochemically the most depleted of the volatile elements. The largest reservoir in the bulk silicate Earth is the mantle, and knowledge of its nitrogen geochemistry is biased, because >= 90% of the mantle nitrogen database comes from diamonds. However, it is not clear to what extent diamonds record the nitrogen characteristics of the fluids/melts from which they precipitate. There is ongoing debate regarding the fundamental concept of nitrogen compatibility in diamond, and empirical global data sets reveal trends indicative of nitrogen being both compatible (fibrous diamonds) and incompatible (non-fibrous monocrystalline diamonds). A more significant and widely overlooked aspect of this assessment is that nitrogen is initially incorporated into the diamond lattice as single nitrogen atoms. However, this form of nitrogen is highly unstable in the mantle, where nitrogen occurs as molecular forms like N-2 or NH4+ both of which are incompatible in the diamond lattice. A review of the available data shows that in classic terms, nitrogen is the most common substitutional impurity found in natural diamonds because it is of very similar atomic size and charge to carbon. However, the speciation of nitrogen, and how these different species disassociate during diamond formation to create transient monatomic nitrogen, are the factors governing nitrogen abundance in diamonds. This suggests the counter-intuitive notion that a nitrogen-free (Type II) diamond could grow from a N-rich media that is simply not undergoing reactions that liberate monatomic N. In contrast, a nitrogen-bearing (Type I) diamond could grow from a fluid with a lower N abundance, in which reactions are occurring to generate (unstable) N atoms during diamond formation. This implies that diamond's relevance to nitrogen abundance in the mantle is far more complicated than currently understood. Therefore, further petrological investigations are required to enable accurate interpretations of what nitrogen data from mantle diamonds can tell us about the deep nitrogen budget and cycle.

Mikhail S., Howell D., McCubbin F.M. Evidence for multiple diamondite-forming events in the mantle // Am. Miner. 2014. Vol. 99, № 8–9. P. 1537–1543.

A collection of 35 diamondite samples (polycrystalline diamond aggregates, sometimes referred to as framesites), assumed to be from southern Africa, have been studied to investigate their infrared (IR) spectroscopic characteristics. Due to the abundance of sub-micrometer, interlocking diamonds (polycrystalline) with mineral and fluid inclusions within the diamond material affecting their transparency, only fragments from 10 of the samples provided high-quality data. The IR spectra showed a wide range of generally high-nitrogen concentrations (386-2677 ppm), with a full range of nitrogen aggregation states, from pure IaA to pure IaB. Platelet characteristics were interpreted as being regular (i.e., not having been affected by deformation and/or heating events), meaning the nitrogen aggregation data could be interpreted with confidence. Surprisingly, the platelet data showed a positive correlation between their intensity (integrated area) and peak position. The primary hydrogen band (at 3107 cm(-1)) and secondary band (at 1405 cm(-1)) are both often present in the samples' spectra, but show no correlation with any other characteristic. There is also no correlation between the samples' paragenesis (as defined by their garnet chemistry) and any of the IR characteristics. While we have no independent determination of the samples mantle residence age, nor the temperature they resided at, we infer that diamondite formation has occurred episodically over a large time frame in single and distinct growth events (as opposed to over a short time frame but over a large depth/temperature range). This idea is more in keeping with the theory that C-O-H diamond-(and diamondite-) forming fluids are the result of localized small volume processes. Interestingly, one sample contained fluid inclusions that exhibited a water:carbonate molar ratio (similar to 0.8), similar to the saline and silicic end-members of the monocrystalline diamond-forming fluid chemical spectrum.

Miller J.R. Forensic Assessment of Metal Contaminated Rivers in the 21st Century Using Geochemical and Isotopic Tracers // Minerals. 2013. Vol. 3, № 2. P. 192–246.

Documentation of contaminant source and dispersal pathways in riverine environments is essential to mitigate the potentially harmful effects of contaminants on human and ecosystem health, and is required from a legal perspective (particularly where the polluter pays principle is in effect) in assessing site liability. Where multiple natural and/or anthropogenic sources exist, identification of contaminant provenance has proven problematic, and estimated contributions from a specific source are often the subject of judicial debate. The past, current, and future use of geochemical and isotopic tracers in environmental forensic investigations of contaminant provenance, transport, and fate are analyzed herein for sediment-associated trace metals in riverine environments, particularly trace metals derived from mining and refining operations. The utilized methods have evolved significantly over the past four decades. Of primary significance has been the growing integration of geomorphic and stratigraphic techniques with the use of an increasing number of geochemical tracers including stable isotopes. The isotopes of Pb have been particularly well studied, and have been applied to a wide range of environmental media. Advances in analytical chemistry since the early 1990s have allowed for the precise characterization of other non-traditional stable isotopic systems within geological materials. The potential for using these non-traditional isotopes as tracers in river systems has yet to be adequately explored, but a number of these isotopes (e. g., Cd, Cu, Cr, Hg, Sb, and Zn) show considerable promise. Moreover, some of these isotopes (e. g., those of Cu, Cr, and Hg) may provide important insights into biogeochemical cycling processes within aquatic environments. This review suggests that future environmental forensic investigations will be characterized by an interdisciplinary approach that combines the use of multiple geochemical tracers with detailed stratigraphic, geomorphic, and hydrologic data, thereby yielding results that are likely to withstand the scrutiny of judicial review.

Mishra P.K. et al. Carbonate isotopes from high altitude Tso Moriri Lake (NW Himalayas) provide clues to late glacial and Holocene moisture source and atmospheric circulation changes // Paleogeogr. Paleoclimatol. Paleoecol. 2015. Vol. 425. P. 76–83.

High resolution isotopic (delta O-18 and delta C-13) investigations on endogenic carbonates (calcite/aragonite) from Tso Moriri Lake, NW Himalaya show dramatic fluctuations during the late glacial and the early Holocene, and a persistent enrichment trend during the late Holocene. Changes in this lake are largely governed by the [input (meltwater + monsoon precipitation)/evaporationj (WE) ratio, also reflected in changes in the carbonate mineralogy with aragonite being formed during periods of lowest I/E. Using new isotopic data on endogenic carbonates in combination with the available data on geochemistry, mineralogy, and reconstructed mean annual precipitation, we demonstrate that the late glacial and early Holocene carbonate delta O-18 variability resulted from fluctuating Indian summer monsoon (ISM) precipitation in NW Himalaya. This region experienced increasing ISM precipitation between ca. 13.1 and 11.7 cal ka and highest ISM precipitation during the early Holocene (11.2-8.5 cal ka). However, during the late Holocene, evaporation was the dominant control on the carbonate delta O-18. Regional comparison of reconstructed hydrological changes from Tso Moriri Lake with other archives from the Asian summer monsoon and westerlies domain shows that the intensified westerly influence that resulted in higher lake levels (after 8 cal ka) in central Asia was not strongly felt in NW Himalaya.

Mullen E.K., Weis D. Sr-Nd-Hf-Pb isotope and trace element evidence for the origin of alkalic basalts in the Garibaldi Belt, northern Cascade arc // Geochem. Geophys. Geosyst. 2013. Vol. 14, № 8. P. 3126–3155.

In the Garibaldi Belt, the northern segment of the Cascade arc, basalts at Bridge River Cones, Salal Glacier, and Mt. Meager (BSM volcanic centers) are alkalic, atypical for an arc setting. Subduction signatures are negligible or absent from primitive alkalic basalts from Salal Glacier and Bridge River, while altered oceanic crust may have contributed a minimal amount of fluid at Mt. Meager. More evolved BSM basalts display trace element signatures considered typical of arc lavas, but this is a consequence of deep crustal assimilation rather than primary input from the subducted slab. Primary BSM basalts represent 3-8% melts that segregated from enriched garnet lherzolite at significantly higher temperatures and pressures (70-105 km) than calc-alkaline Cascade arc basalts. The BSM mantle source is significantly more incompatible element-enriched than the depleted mantle tapped by calc-alkaline Cascade arc basalts. The BSM basalts are also isotopically distinct from calc-alkaline Cascade arc basalts, more similar to MORB and intraplate basalts of the NE Pacific and NW North America. The relatively deep, hot, and geochemically distinct mantle source for BSM basalts is consistent with upwelling asthenosphere. The BSM volcanic centers are close to the projected trace of the Nootka fault, which forms the boundary between the subducting Juan de Fuca plate and the near-stagnant Explorer plate. A gap or attenuated zone between the plates may promote upwelling of enriched asthenosphere that undergoes low-degree decompression melting to generate alkalic basalts that are essentially free of slab input yet occur in an arc setting.

Mysen B. Hydrogen isotope fractionation between coexisting hydrous melt and silicate-saturated aqueous fluid: An experimental study in situ at high pressure and temperature // Am. Miner. 2013. Vol. 98, № 2–3. P. 376–386.

Hydrogen isotope fractionation between water-saturated silicate melt and silicate-saturated aqueous fluid has been determined experimentally by using vibrational spectroscopy as the analytical tool. The measurements were conducted in situ with samples at the high temperature and pressure of interest in an externally heated diamond cell in the 450-800 degrees C and 101-1567 MPa temperature and pressure range, respectively. The starting materials were glass of Na-silicate with Na/Si = 0.5 (NS4), an aluminosilicate composition with 10 mol% Al2O3 and Na/(Al+Si) = 0.5 (NA10), and a 50:50 (by volume) H2O:D2O fluid mixture. Platinum metal was used to enhance equilibration rate. Isotopic equilibrium was ascertained by using variable experimental duration at given temperature and pressure. In the Al-free NS4 system, the enthalpy of the D/H equilibrium of fluid is 3.1 +/- 0.7 kJ/mol, whereas that of coexisting melt equals 0 within error. For NA10 fluids the Delta H = 5.2 +/- 0.9 kJ/mol, whereas for coexisting NA10 melt, Delta H is near 0 within error. For the exchange equilibrium between melt and coexisting fluid, H2O(melt)+D2O(fluid) = H2O(fluid)+D2O(melt) the Delta H = 4.6 +/- 0.7 and 6.5 +/- 0.7 kJ/mol for NS4 and NA10 compositions, respectively. The D/H fractionation between melt and fluid is affected significantly by the positive temperature- and pressure-dependence of silicate solubility and silicate structure in silicate-saturated aqueous fluids. Water in melts is much less important than silicate in aqueous fluid because even at the lowest temperature and pressure conditions studied (450 degrees C/101 MPa), the water content in the melt is so high (>4 wt%) that further increase in total water by increasing temperature and pressure does not affect the silicate melt structure significantly. This is because most of the water in this concentration range is dissolved in molecular form.

Mysen B.O. et al. Speciation of and D/H partitioning between fluids and melts in silicate-D-O-H-C-N systems determined in-situ at upper mantle temperatures, pressures, and redox conditions // American Mineralogist. 2014. Vol. 99, № 4. P. 578–588.

Speciation of D-O-H-C-N volatiles in alkali aluminosilicate melts and of silicate in D-O-H-C-N fluid has been determined in situ to 800 degrees C and >2 GPa under reducing and oxidizing conditions by using an externally heated hydrothermal diamond-anvil cell with Raman spectroscopy as the structural probe. Reducing conditions were near those of the IW oxygen buffer, whereas oxidizing conditions were obtained by conducting the experiments with oxidized components only and with Pt as a catalyst. Raman bands assigned to C-H stretching in CHxDy isotopologues and CH4 groups (including CH3) were employed to determine the CH4/CHxDy ratio in fluids and melts. This ratio decreases from 1.5-2 at 500 degrees C to between 1.2 and 1 with 800 degrees C with Delta H-values of 13.6 +/- 2.1 and 5.5 +/- 1.1 kJ/mol for melt and fluid, respectively. The CHx/CHxDy fluid/melt partition coefficient ranges between similar to 16 and similar to 3 with Delta H= 33 +/- 6 kJ/mol assuming no pressure effect. This behavior of deuterated and protonated complexes is ascribed to speciation of volatile and silicate components in fluids and melts in a manner that is conceptually similar to D/H partitioning among complexes and phases in brines and hydrous silicate systems. Molecular N-2 is the N-bearing species in fluids and melts under oxidizing conditions. Under reducing conditions, the dominant species are molecular NH3 and ammine groups, NH2-. The NH3/NH2 ratio varies between 0.15 and 0.75 in the 425-800 degrees C temperature range. The enthalpy change of the ammonia/ammine equilibrium, Delta H, derived from the temperature and assuming no pressure effect on the equilibrium, is

Parsons I., Gerald J.D.F., Lee M.R. Routine characterization and interpretation of complex alkali feldspar intergrowths // Am. Miner. 2015. Vol. 100, № 5–6. P. 1277–1303.

Almost all alkali feldspar crystals contain a rich inventory of exsolution, twin, and domain microtextures that form subsequent to crystal growth and provide a record of the thermal history of the crystal and often of its involvement in replacement reactions, sometimes multiple. Microtextures strongly influence the subsequent behavior of feldspars at low temperatures during diagenesis and weathering. They are central to the retention or exchange of trace elements and of radiogenic and stable isotopes. This review is aimed at petrologists and geochemists who wish to use alkali feldspar microtextures to solve geological problems or who need to understand how microtextures influence a particular process. We suggest a systematic approach that employs methods available in most well founded laboratories. The crystallographic relationships of complex feldspar intergrowths were established by the 1970s, mainly using single-crystal X-ray diffraction, but such methods give limited information on the spatial relationships of the different elements of the microtexture, or of the mode and chronology of their formation, which require the use of microscopy. We suggest a combination of techniques with a range of spatial resolution and strongly recommend the use of orientated sections. Sections cut parallel to the perfect (001) and (010) cleavages are the easiest to locate and most informative. Techniques described are light microscopy; scanning electron microscopy using both backscattered and secondary electrons, including the use of surfaces etched in the laboratory; electron-probe microanalysis and analysis by energy-dispersive spectrometry in a scanning electron microscope; transmission electron microscopy. We discuss the use of cathodoluminescence as an auxiliary technique, but do not recommend electron-backscattered diffraction for feldspar work. We review recent publications that provide examples of the need for great care and attention to pre-existing work in microtextural studies, and suggest several topics for future work.

Petraki E. et al. Self-organised critical features in soil radon and MHz electromagnetic disturbances: Results from environmental monitoring in Greece // Applied Radiation and Isotopes. 2013. Vol. 72. P. 39–53.

This paper addresses the issues of self-organised critical behaviour of soil-radon and MHz-electromagnetic disorders during intense seismic activity in SW Greece. A significant radon signal is re-analysed for environmental influences with Fast Fourier Transform and multivariate statistics. Self-organisation of signals is investigated via fractal evolving techniques and detrended fluctuation analysis. New lengthy radon data are presented and analysed accordingly. The data did not show self-similarities. Similar analysis applied to new important concurrent MHz-electromagnetic signals revealed analogous behaviour to radon. The signals precursory value is discussed.

Rao Z. et al. Variation and paleoclimatic significance of organic carbon isotopes of Ili loess in arid Central Asia // Org. Geochem. 2013. Vol. 63. P. 56–63.

As an indicator for terrestrial paleovegetation, the stable isotopic composition of total organic matter (delta C-13(org)) in loess sediments has been widely used for paleoclimatic reconstruction in western Europe, the Great Plains of North America and the Chinese Loess Plateau (CLP). However, little is known about the variation and paleoclimatic significance of the loess delta C-13(org) in arid Central Asia (ACA). We report delta C-13(org) data from an Axike (AXK) loess/paleosol profile from the eastern Ili Basin, eastern Central Asia. Along the profile, the delta C-13(org) values were more negative in the paleosol layers observed in the field and were confirmed by environmental magnetic proxies and a higher concentration of total organic carbon (TOC), consistent with results for western Europe and the northwestern CLP. Our results demonstrate that the loess delta C-13(org) in this region documents mainly the response of delta C-13 of locally predominant C-3 plants to paleoclimatic variation, especially paleoprecipitation. Our results also suggest that the loess delta C-13(org) values in the area have the potential for quantitative paleoprecipitation reconstruction on the basis of detailed delta C-13(org) results from modern plants and surface soils in the future.

Reutsky V. et al. Carbon isotope fractionation during experimental crystallisation of diamond from carbonate fluid at mantle conditions // Contrib. Mineral. Petrol. 2015. Vol. 170, № 5–6. P. 41.

We report first results of a systematic study of carbon isotope fractionation in a carbonate fluid system under mantle PT conditions. The system models a diamond-forming alkaline carbonate fluid using pure sodium oxalate (Na2C2O4) as the starting material, which decomposes to carbonate, CO2 and elementary carbon (graphite and diamond) involving a single source of carbon following the reaction 2Na(2)C(2)O(4) -> 2Na(2)CO(3) + CO2 + C. Near-liquidus behaviour of carbonate was observed at 1300 degrees C and 6.3 GPa. The experimentally determined isotope fractionation between the components of the system in the temperature range from 1300 to 1700 degrees C at 6.3 and 7.5 GPa fit the theoretical expectations well. Carbon isotope fractionation associated with diamond crystallisation from the carbonate fluid at 7.5 GPa decreases with an increase in temperature from 2.7 to 1.6 parts per thousand. This trend corresponds to the function Delta(Carbonate fluid-Diamond) = 7.38 x 10(6) T-2.

Saintilan N.J. et al. A refined genetic model for the Laisvall and Vassbo Mississippi Valley-type sandstone-hosted deposits, Sweden: constraints from paragenetic studies, organic geochemistry, and S, C, N, and Sr isotope data // Miner. Depos. 2016. Vol. 51, № 5. P. 639–664.

The current study has aimed to refine the previously proposed two-fluid mixing model for the Laisvall (sphalerite Rb-Sr age of 467 +/- 5 Ma) and Vassbo Mississippi Valley-type deposits hosted in Ediacaran to Cambrian sandstone, Sweden. Premineralization cements include authigenic monazite, fluorapatite, and anatase in the Upper Sandstone at Laisvall, reflecting anoxic conditions during sandstone burial influenced by the euxinic character of the overlying carbonaceous middle Cambrian to Lower Ordovician Alum Shale Formation (delta C-13(org) = -33.0 to -29.5 aEuro degrees, delta N-15(org) = 1.5 to 3.3 aEuro degrees, 0.33 to 3.03 wt% C, 0.02 to 0.08 wt% N). The available porosity for epigenetic mineralization, including that produced by subsequent partial dissolution of pre-Pb-Zn sulfide calcite and barite cements, was much higher in calcite- and barite-cemented sandstone paleoaquifers (29 % by QEMSCAN mapping) than in those mainly cemented by quartz (8 %). A major change in the Laisvall plumbing system is recognized by the transition from barite cementation to Pb-Zn sulfide precipitation in sandstone. Ba-bearing, reduced, and neutral fluids had a long premineralization residence time (highly radiogenic S-87/Sr-86 ratios of 0.718 to 0.723) in basement structures. As a result of an early Caledonian arc-continent collision and the development of a foreland basin, fluids migrated toward the craton and expelled Ba-bearing fluids from their host structures into overlying sandstone where they deposited barite upon mixing with a sulfate pool (delta S-34(barite) = 14 to 33 aEuro degrees). Subsequently, slightly acidic brines initially residing in pre-Ediacaran rift sediments in the foredeep of the early Caledonian foreland basin migrated through the same plumbing system and acquired metals on the way. The bulk of Pb-Zn mineralization formed at temperatures between 120 and 180 A degrees C by mixing of these brines with a pool of H2S (delta S-34 = 24 to 29 aEuro degrees) produced via thermochemical sulfate reduction (TSR) with oxidation of hydrocarbons in sandstone. Other minor H2S sources are identified. Upward migration and fluctuation of the hydrocarbon-water interface in sandstone below shale aquicludes and the formation of H2S along this interface explain the shape of the orebodies that splay out like smoke from a chimney and the conspicuous alternating layers of galena and sphalerite. Intimate intergrowth of bitumen with sphalerite suggests that subordinate amounts of H2S might have been produced by TSR during Pb-Zn mineralization. Gas chromatograms of the saturated hydrocarbon fraction from organic-rich shale and from both mineralized and barren sandstone samples indicate that hydrocarbons migrated from source rocks in the overlying Alum Shale Formation buried in the foredeep into sandstone, where they accumulated in favorable traps in the forebulge setting.

Savage P.S. et al. High temperature silicon isotope geochemistry // Lithos. 2014. Vol. 190. P. 500–519.

Silicon (Si) is the defining element of silicate reservoirs yet, despite its dominance in major Earth processes, there is still no clear understanding of how much is hosted in Earth's core, how the enriched continental crust forms or even if the crust is isotopically different from the mantle because of a long history of weathering, erosion and subduction. With the advent of multiple collector inductively coupled plasma mass spectrometry it has become relatively straightforward to explore small (100 ppm level) mass dependent variations in Si isotopic composition resulting from high temperature fractionation and to develop new isotopic fingerprints of magmatic processes and source regions. This paper reviews the technique developments, the new data and the veracity of current interpretations. Only a small Si isotopic effect is associated with basalt formation via mantle melting. However, there now is compelling evidence, based on a considerable number of samples (> 100), that the silicate Earth is isotopically fractionated by 100-200 ppm per amu to a heavy composition relative to that of chondrites and also all differentiated stony meteorites. This could reflect variability in the circumstellar disc, but this is not well supported by data for enstatite chondrites which are isotopically light. The most plausible current explanation is that Si is a light element in Earth's core and that differences in the bond stiffness between silicate- and metal-hosted Si resulted in substantial fractionation. Interestingly, the Moon has the same Si isotope composition as Earth's mantle, which is hard to explain unless the Moon's atoms were mainly derived from Earth. Differentiated magmatic sequences such as those of Hekla, Iceland display a systematic relationship between isotopic composition and Si content. More complex magmatic suites, such as I- and S-type granites, reveal a range of isotopic compositions not well correlated with chemical composition. Similar effects are found in lower crustal granulite facies xenoliths. Nonetheless the overall composition of the continental crust is only slightly heavy relative to the mantle; in fact the effect is barely resolvable. Therefore, the amounts of surface dissolved heavy Si removed to the mantle via weathering over time have been small or these losses have been balanced by subduction of isotopically light clay.

Schulz T. et al. Formation and exposure history of non-magmatic iron meteorites and winonaites: Clues from Sm and W isotopes // Geochim. Cosmochim. Acta. 2012. Vol. 85. P. 200–212.

New W and Sm isotope measurements for metals and silicates of non-magmatic iron meteorite groups and winonaites are presented and compiled with literature data to assess their exposure history and parent body formation. We report high-precision W-182 data for eight IAB metals supplemented by literature data and introduce a method to calculate their zero-exposure values. Our estimate reveals a common radiogenic W-182 signature of -2.83 +/- 0.03 epsilon-units for the IAB iron meteorite complex. This suggests metal separation at 5.06(+0.42)/(-0.41) Ma after solar system formation. The refined age estimate for core formation agrees remarkably well with previously published Hf-182-W-182 ages for silicate melting (4.6(+0.7)/(-0.6) Ma; Schulz et al., 2009) and the formation of winonaites (4.8(+3.1)/(-2.6) Ma; Schulz et al., 2010), which are assumed to be derived from the same parent body. If interpreted in favour of an asteroid-wide (and therefore most likely internal) heat source, these ages correspond to an accretion age for the IAB/winonaite parent body of similar to 2 Ma after solar system formation. However, metals from ungrouped IAB specimen segregated at significantly different times. Separation of Mundrabilla metals at similar to 13 Ma after solar system formation can best be explained via impact triggered melt pool formation, a process that could also be responsible for metamorphism of IAB silicates and winonaites between similar to 11 and similar to 14 Ma (Schulz et al., 2009, 2010). Sm-149 and Sm-150 compositions, indicative of cosmic ray effects, for five IAB silicates reveal a correlation with exposure ages obtained from metal phases and, together with data on three winonaites, provide no compelling evidence for exposure of silicates within near surface regions of the IAB/winonaite parent asteroid. Tungsten isotope compositions of metals from six IIE iron meteorites, measured in this study and reported in the literature, reveal three consecutive metal segregation events at similar to 3, similar to 13 and similar to 28 Ma after formation of the solar system. Whereas the oldest event could potentially be explained by internal heat sources, impacts provide the only viable explanation for the latter. A prolonged time-span for thermal events, as deduced from IIE metals, is supported by Hf-182-W-182 data for two silicate inclusions from Watson (Snyder et al., 2001) and Miles (this study). Samarium isotope data for a silicate inclusion from the Miles meteorite provides no evidence for 2 pi-exposure.

Shiel A.E., Weis D., Orians K.J. Tracing cadmium, zinc and lead sources in bivalves from the coasts of western Canada and the USA using isotopes // Geochim. Cosmochim. Acta. 2012. Vol. 76. P. 175–190.

Environmental monitoring and remediation require techniques to identify the source and fate of metals emissions. The measurement of heavy metal isotopic signatures, made possible by the advent of the MC-ICP-MS, is a powerful new geochemical tool, which may be used to trace the source of these metals in the environment. In a multi-tracer study, Cd, Zn and Pb isotopic compositions (MC-ICP-MS) and elemental concentrations (HR-ICP-MS) are used to distinguish between natural and anthropogenic sources of these metals in bivalves collected from western Canada (British Columbia), Hawaii, and the USA East Coast. Variability in the delta Cd-114/110 values of bivalves (-1.20 parts per thousand to -0.09 parts per thousand) is attributed to differences in the relative contributions of Cd from natural and anthropogenic sources between sites. Cadmium isotopic compositions (delta Cd-114/110 = -0.69 parts per thousand to -0.09 parts per thousand) identify high Cd levels in B.C. oysters as primarily natural (i.e., upwelling of Cd rich intermediate waters in the North Pacific), with some variability attributed to anthropogenic sources (e.g., mining and smelting). Variability in the delta Zn-66/64 values exhibited by the B.C. bivalves is relatively small (0.28-0.36 parts per thousand). Despite the low Pb levels found in B.C. oysters, Pb isotopes are used to identify emissions from industrial processes and the consumption of unleaded gasoline and diesel fuel as significant metal sources. Although the Cd concentrations of the USA East Coast bivalves are primarily lower than those of B.C. oysters, their relatively light Cd isotopic compositions (delta Cd-114/110 = -1.20 parts per thousand to -0.54 parts per thousand) indicate the significance of anthropogenic Cd sources and are attributed to the high prevalence of industry on this coast. The delta Cd-114/110 values of USA East Coast bivalves include the lightest ever reported, with the exception of values reported for extraterrestrial materials. In addition, the Pb isotopic compositions of bivalves from the USA East Coast indicate Pb emissions from the combustion of coal are an important source of Pb, consistent with the high consumption of coal for power production on this coast. This study demonstrates the effective use of Cd and Zn isotopes to trace anthropogenic sources in the environment and the benefit of combining these tools with Pb "fingerprinting" techniques.

Shulaker D.Z. et al. In-situ oxygen isotope and trace element geothermometry of rutilated quartz from Alpine fissures // Am. Miner. 2015. Vol. 100, № 4. P. 915–925.

Finely acicular rutile intergrown with host quartz (rutilated quartz) is commonly found in hydrothermal veins, including the renown cleft mineral locations of the Swiss Alps. These Alpine cleft mineralizations reportedly formed between similar to 13.5 and 15.2 Ma (based on ages of rare hydrothermal monazite and titanite) at temperatures (7) of similar to 150-450 degrees C (based on fluid inclusions and bulk quartz-mineral oxygen isotope exchange equilibria), and pressures (P) of 0.5-2.5 kbar (estimated from a geothermal gradient of 30 degrees C/km). The potential of rutilated quartz as a thermochronometer, however, has not been harnessed previously. Here, we present the first results of age and T determinations for rutilated quartz from six locations in the Swiss Alps with vein country rocks that cover peak-metamorphic conditions between similar to 600 and <350 degrees C. Samples were cut and mounted in epoxy disks to expose rutile (similar to 30 to 1400 mu m in diameter) and its host quartz. Cathodoluminescence (CL) and backscattered electron (BSE) imaging of host quartz and rutile inclusions, respectively, shows internal zonations, which are nevertheless isotopically homogeneous. Newly developed secondary ionization mass spectrometry (SIMS) oxygen isotopic analysis protocols for rutile were combined with those established for trace elements (including Zr) and U-Pb ages in rutile, and Ti abundances in the host quartz. U-Pb rutile ages average 15.1 +/- 1.7 Ma (2 sigma), in excellent agreement with previous accessory mineral geochronometers. Pressure-independent T estimates, calibrated for low-temperature conditions, from oxygen isotope fractionation between rutile and quartz in touching pairs are 310-576 degrees C. Individual rutile needles vary in Zr abundances beyond analytical uncertainties, but average Zr-in-rutile inversely correlates with oxygen isotopic fractionation between quartz and rutile. Linear regression of the data yields: T(degrees C) = 26(+/- 9)/0.037/(+/- 0.01)-R Inx - 273 with x = Zr ppm and R = 0.008314 (uncertainties scaled by the square root of the mean square of weighted deviates MSWD = 11; n = 9). This relationship supports previously recognized temperature-dependent Zr uptake in rutile, although widely used Zr-in-rutile thermometer calibrations based on high-T experiments are at variance with oxygen isotope exchange temperatures. By contrast, Ti-inquartz lacks systematic relations with oxygen isotope temperatures. The discrepancy between low-T Ti-in-quartz thermometry on one side, and oxygen isotope and Zr-in-rutile thermometry on the other, suggests that Ti-in-quartz thermometry should be applied with caution for low- T (<500 degrees C) rocks.

Sossi P.A. et al. Combined Separation of Cu, Fe and Zn from Rock Matrices and Improved Analytical Protocols for Stable Isotope Determination // Geostand. Geoanal. Res. 2015. Vol. 39, № 2. P. 129–149.

Isotope ratios of heavy elements vary on the 1/10000 level in high temperature materials, providing a fingerprint of the processes behind their origin. Ensuring that the measured isotope ratio is precise and accurate depends on employing an efficient chemical purification technique and optimised analytical protocols. Exploiting the disparate speciation of Cu, Fe and Zn in HCl and HNO3, an anion exchange chromatography procedure using AG1-x8 (200-400 mesh) and 0.4x7cm Teflon columns was developed to separate them from each other and matrix elements in felsic rocks, basalts, peridotites and meteorites. It required only one pass through the resin to produce a quantitative and pure isolate, minimising preparation time, reagent consumption and total analytical blanks. A ThermoFinnigan Neptune Plus MC-ICP-MS with calibrator-sample bracketing and an external element spike was used to correct for mass bias. Nickel was the external element in Cu and Fe measurements, while Cu corrected Zn isotopes. These corrections were made assuming that the mass bias for the spike and analyte element was identical, and it is shown that this did not introduce any artificial bias. Measurement reproducibilities were 0.03 parts per thousand, +/- 0.04 parts per thousand and +/- 0.06 parts per thousand (2s) for Fe-57, Cu-65 and Zn-66, respectively. Les rapports isotopiques des elements lourds varient au niveau de la quatrieme decimale dans les materiaux de haute temperature, fournissant ainsi un acces aux processus ayant participe a la formation de ces derniers. S'assurer que le rapport isotopique mesure est precis et exact depend de l'emploi d'une technique de purification chimique efficace et de protocoles analytiques optimises. L'exploitation de la speciation differentielle de Cu, Fe et Zn dans l'HCl et le HNO3 a permis le developpement d'une procedure de chromatographie echangeuse d'anions utilisant de la resine anionique AG1-X8 (200-400 mesh) et des colonnes en teflon (0.4 x 7cm) pour separer ces elements a la fois les uns des autres mais aussi de ceux de la matrice dans des roches felsiques, des basaltes, des peridotites et des meteorites. Il n'a fallu qu'un seul passage dans la resine pour produire un isolat mono elementaire ultra pur, en minimisant le temps de preparation, la consommation de reactif et le blanc analytique total. En utilisant un MC-ICP-MS ThermoFinnigan Neptune plus, une alternance standard-echantillon avec etalon externe a servi a corriger le biais de masse. Le Nickel etait l'element externe dans les mesures de Cu et de Fe alors que le Cu a ete utilise pour corriger les isotopes du Zn. Ces corrections ont ete apportees en supposant que le biais de masse pour le spike et l'element analyse etait identique, et il est demontre que cela n'a pas introduit de biais artificiel. La reproductibilite des mesures a ete de +/- 0.03 parts per thousand, +/- 0.04 parts per thousand et +/- 0.06 parts per thousand (2s) pour respectivement Fe-57, Cu-65 et Zn-66.

Suresh P.O. et al. Assessment of a sequential phase extraction procedure for uranium-series isotope analysis of soils and sediments // Applied Radiation and Isotopes. 2014. Vol. 83, Part A. P. 47–55.

The study of uranium-series (U-series) isotopes in soil and sediment materials has been proposed to quantify rates and timescales of soil production and sediment transport. Previous works have studied bulk soil or sediment material, which is a complex assemblage of primary and secondary minerals and organic compounds. However, the approach relies on the fractionation between U-series isotopes in primary minerals since they were liberated from the parent rock via weathering. In addition, secondary minerals and organic compounds have their own isotopic compositions such that the composition of the bulk material may not reflect that of primary minerals. Hence, there is a need for a sample preparation procedure that allows the isolation of primary minerals in soil or fluvial sediment samples. In this study, a sequential extraction procedure to separate primary minerals from soils and sediments was assessed. The procedure was applied to standard rock sample powders (TML-3 and BCR-2) to test whether it introduced any artefactual radioactive disequilibrium. A new step was introduced to remove the clay-sized fraction (<2 µm). Significant amounts (5–14%) of U and Th were removed from the rock standards during the procedure. No significant alteration in (234U/238U) and (230Th/238U) activity ratios of the rock standards occurred during the procedure. Aliquots of soil sample were subjected to the sequential extraction process to test how each step modifies the uranium-series activity ratios and mineralogy. Although no secondary minerals were detected in the unleached soil aliquots, the sequential leaching process removed up to 17% of U and Th and modified their activity ratios by up to 3%. The modification of the activity ratios poses a demand for careful means to avoid redistribution of isotopes back to the residual phase during phase extraction.

Suresh P.O. et al. Soil formation rates determined from Uranium-series isotope disequilibria in soil profiles from the southeastern Australian highlands // Earth Planet. Sci. Lett. 2013. Vol. 379. P. 26–37.

The sustainability of soil resources is determined by the balance between the rates of production and removal of soils. Samples from four weathering profiles at Frogs Hollow in the upper catchment area of the Murrumbidgee River (southeastern Australia) were analyzed for their uranium-series (U-series) isotopic composition to estimate soil production rates. Sequential leaching was conducted on sample aliquots to assess how U-series nuclides are distributed between primary and secondary minerals. Soil is increasingly weathered from bottom to top which is evident from the decrease in (U-234/U-238) ratios and increase in relative quartz content with decreasing soil depth. One soil profile shows little variation in mineralogy and U-series geochemistry with depth, explained by the occurrence of already extensively weathered saprolite, so that further weathering has minimal effect on mineralogy and geochemistry. Al2O3 is mobilized from these soils, and hence a silicon-based weathering index treating Al2O3 as mobile is introduced, which increases with decreasing soil depth, in all profiles. Leached and unleached aliquots show similar mineralogy with slight variation in relative concentrations, whereas the elemental and isotopic composition of uranium and thorium show notable differences between leached and unleached samples. Unleached samples show systematic variations in uranium-series isotopic compositions with depth compared to leached samples. This is most likely explained by the mobilization of U and Th from the samples during leaching. Soil residence times are calculated by modeling U-series activity ratios for each profile separately. Inferred timescales vary up to 30 kyr for unleached aliquots from profile F1 to up to 12 kyr for both leached and unleached aliquots from profile F2. Muscovite content shows a linear relationship with U-series derived soil residence times. This relationship provides an alternative method to estimate residence timescales for profiles with significant U-series data scatter. Using this alternative approach, inferred soil residence times up to 33 kyr for leached samples of profile F1 and up to 34 kyr for leached samples of profile F3 were determined. A linear relationship between soil residence times and WIS (Si-based Weathering Index) exists and is used to estimate soil residence times for profile F3 (up to 28 kyr) and F4 (up to 37 kyr). The linear relationship between soil depth and calculated residence time allows determination of soil production rates, which range from 10 to 24 mm/kyr and are comparable to the rates determined previously using cosmogenic isotopes at the same site (Heimsath et al., 2001b). This implies that at this site, on the highland plateau of southeastern Australia, soil thickness has reached steady-state, possibly as a result of stable tectonic conditions but despite variable climatic conditions over the timescale of soil development. Soil-mantled landscapes are the geomorphic expression of this balance between soil production and denudation, and our results show that in tectonically quiescent regions, this landscape can be achieved in less than 30 kyr.

Tanner D. et al. Sulfur isotope and trace element systematics of zoned pyrite crystals from the El Indio Au-Cu-Ag deposit, Chile // Contrib. Mineral. Petrol. 2016. Vol. 171, № 4. P. 33.

We present a comparative study between early, massive pyrite preceding (Cu-Ag) sulfosalt mineralization in high-temperature feeder zones ('early pyrite') and late pyrite that formed during silicic alteration associated with Au deposition ('late pyrite') at the El Indio high-sulfidation Au-Ag-Cu deposit, Chile. We use coupled in situ sulfur isotope and trace element analyses to chronologically assess geochemical variations across growth zones in these pyrite crystals. Early pyrite that formed in high-temperature feeder zones shows intricate oscillatory zonation of Cu, with individual laminae containing up to 1.15 wt% Cu and trace Co, As, Bi, Ni, Zn, Se, Ag, Sb, Te, Au, Pb and Bi. Late pyrite formed after (Cu-Ag) sulfosalt mineralization. It contains up to 1.14 wt% As with trace Cu, Zn, Pb, V, Mn, Co, Ni, Ge, Se, Ag, Sb, Te, Pb and Bi, as well as colloform Cu-rich growth bands containing vugs toward the outer edges of some crystals. Plotting the trace element data in chronological order (i.e., from core to rim) revealed that Co and Ni were the only elements to consistently covary across growth zones. Other trace elements were coupled in specific growth zones, but did not consistently covary across any individual crystal. The delta S-34 of early pyrite crystals in high-temperature feeder zones range from -3.19 to 1.88 parts per thousand (+/- 0.5 parts per thousand), consistent with sublimation directly from a high-temperature magmatic vapor phase. Late pyrite crystals are distinctly more enriched in delta S-34 than early pyrite (delta S-34 = 0.05-4.77 parts per thousand, +/- 0.5 parts per thousand), as a consequence of deposition from a liquid phase at lower temperatures. It is unclear whether the late pyrite was deposited from a small volume of liquid condensate, or a larger volume of hydrothermal fluid. Both types of pyrite exhibit intracrystalline delta S-34 variation, with a range of up to 3.31 parts per thousand recorded in an early pyrite crystal and up to 4.48 parts per thousand in a late pyrite crystal. Variations in delta S-34(pyrite) at El Indio did not correspond with changes in trace element geochemistry. The lack of correlation between trace elements and delta S-34, as well as the abundance of microscale mineral inclusions and vugs in El Indio pyrite indicate that the trace element content of pyrite at El Indio is largely controlled by nanoscale, syndepositional mineral inclusions. Co and Ni were the only elements partitioned within the crystal structure of pyrite. Cu-rich oscillatory zones in early pyrite likely formed by nanoscale inclusions of Cu-rich sulfosalts or chalcopyrite, evidence of deposition from a fluid cyclically saturated in ore metals. This process may be restricted to polymetallic high-sulfidation-like deposits.

Torfstein A. Size fractionation, reproducibility and provenance of helium isotopes in north-equatorial pacific pelagic clays // Earth Planet. Sci. Lett. 2012. Vol. 339. P. 151–163.

Helium isotope compositions were measured in late Quaternary pelagic clays from the North Equatorial Pacific, where terrestrial and extra-terrestrial end member components are identified and quantified in different grain size populations. The results provide important constraints on the nature of interplanetary dust particles (IDPs) in sedimentary environments and on their application as constant flux proxies in paleoceanographic studies. Approximately 92-95% of the extra-terrestrial He-3 (He-3(ET)) is concentrated in particles smaller than 20 mu m. Within this grain size group, similar to 44% of He-3(ET) is concentrated in the 20-10 and 10-2 mu m fractions, while more than 50% of the total He-3(ET) is found in fine particles smaller than 2 mu m. The peak concentration of He-3(ET) in the very fine particle size population explains a consistently better reproducibility of He-3(ET) in sediments compared to model predictions that is related to the relatively homogenous distribution of clay-size particles in sediments compared to coarser particles, especially in deep-sea sediments and ice cores. The He-3/He-4 ratios are highest in the coarser than 20 mu m fractions, peaking between 63 and 38 mu m (1.78 +/- 1.13 x 10(-4)), compared to the bulk and the <20 mu m fractions (3.20 +/- 2.62 x 10(-5) and 2.11 +/- 0.88 x 10(-5) respectively). The isotopic composition of helium in each of the size fractions reflects a mixture between a pure extraterrestrial end member and a terrigenous component, which is itself comprised of varying mixtures of volcanic material and eolian material associated with the fine grain size fraction of loess deposits in South East Asia. Poor He-3(ET) reproducibility observed here and elsewhere, inhibiting its application as a constant flux proxy, stems from the presence of a small number of aliquots displaying significantly higher He-3(ET) contents compared to the average of their reference group. These Helium Rich Particles (HRPs), are probably characterized by a <20 mu m diameter and carry significant amounts of extraterrestrial He-3 and He-4. Careful rejection of such aliquots improves the signal reproducibility by more than two fold.

Verbovsek T., Kanduc T. Isotope Geochemistry of Groundwater from Fractured Dolomite Aquifers in Central Slovenia // Aquat. Geochem. 2016. Vol. 22, № 2. P. 131–151.

The hydrogeochemistry and isotope geochemistry of groundwater from 85 wells in fractured dolomite aquifers of Central Slovenia were investigated. This groundwater represents waters strongly influenced by chemical weathering of dolomite with an average of delta C-13(CARB) value of +2.2 %. The major groundwater geochemical composition is HCO3- > Ca2+ > Mg2+. Several differences in hydrogeochemical properties among the classes of dolomites were observed when they were divided based on their age and sedimentological properties, with a clear distinction of pure dolomites exhibiting high Mg2+/Ca2+ ratios and low Na+, K+ and Si values. Trace element and nutrient concentrations (SO42-, NO3-) were low, implying that karstic and fractured dolomite aquifers are of good quality to be used as tap water. Groundwater was generally slightly oversaturated with respect to calcite and dolomite, and dissolved CO2 was up to 46 times supersaturated relative to the atmosphere. The isotopic composition of oxygen (delta O-18(H2O)), hydrogen (delta D-H2O) and tritium ranged from -10.3 to -8.4 %, from -68.5 to -52.7 % and from 3.5 TU to 10.5 TU, respectively. delta O-18 and delta D values fell between the GMWL (Global Meteoric Water Line) and the MMWL (Mediterranean Meteoric Water Line) and indicate recharge from precipitation with little evaporation. The tritium activity in groundwater suggests that groundwater is generally younger than 50 years. delta C-13(DIC) values ranged from -14.6 to -9.3 % and indicated groundwater with a contribution of degraded organic matter/dissolved inorganic carbon in the aquifer. The mass balances for groundwater interacting with carbonate rocks suggested that carbonate dissolution contributes from 43.7 to 65.4 % and degradation of organic matter from 34.6 to 56.3 %.

von Blanckenburg F., Bouchez J. River fluxes to the sea from the ocean’s Be-10/Be-9 ratio // Earth Planet. Sci. Lett. 2014. Vol. 387. P. 34–43.

The ratio of the meteoric cosmogenic radionuclide Be-10 to the stable isotope Be-9 is proposed here to be a flux proxy of terrigenous input into the oceans. The ocean's dissolved Be-10/Be-9 is set by (1) the flux of meteoric Be-10 produced in the atmosphere; (2) the denudational flux of the rivers discharging into a given ocean basin; (3) the fraction of Be-9 that is released from primary minerals during weathering (meaning the Be-9 transported by rivers in either the dissolved form or adsorbed onto sedimentary particles and incorporated into secondary oxides); and (4) the fraction of riverine Be-10 and Be-9 actually released into seawater. Using published Be-10/Be-9 data of rivers for which independent denudation rate estimates exist we first find that the global average fraction of Be-9 released during weathering into river waters and their particulate load is 20% and does not depend on denudation rate. We then evaluate this quantitative proxy for terrigenous inputs by using published dissolved seawater Be isotope data and a compilation of global river loads. We find that the measured global average oceanic dissolved Be-10/Be-9 ratio of about 0.9 x 10(-7) is satisfied by the mass balance if only about 6% of the dissolved and adsorbed riverine Be is eventually released to the open ocean after escaping the coastal zone. When we establish this mass balance for individual ocean basins good agreement results between Be-10/Be-9 ratios predicted from known river basin denudation rates and measured ocean Be-10/Be-9 ratios. Only in the South Atlantic and the South Pacific the Be-10/Be-9 ratio is dominated by advected Be and in these basins the ratio is a proxy for ocean circulation. As the seawater Be-10/Be-9 ratio is faithfully recorded in marine chemical precipitates the Be-10/Be-9 ratio extracted from authigenic sediments can now serve to estimate relative changes in terrigenous input into the oceans back through time on a global and on an ocean basin scale.

Wang X. et al. Stable carbon isotope of black carbon in lake sediments as an indicator of terrestrial environmental changes: An evaluation on paleorecord from Daihai Lake, Inner Mongolia, China // Chem. Geol. 2013. Vol. 347. P. 123–134.

We measured the carbon isotope ratio of black carbon (BC) from the Daihai Lake sediment core (DH99a) in north-central China with an objective to examine the effectiveness and sensitivity of the delta C-13 values of BC (delta C-13(BC)) as a potential indicator of terrestrial environmental changes. We first performed a statistical study on the available data regarding carbon isotope fractionation (CIF) during the conversion of C3 and C4 vegetation to BC and observed that the mean CIF for BC produced from C3 plants is -03%., whereas that for BC from C4 plants is -1.7 parts per thousand. This result provides a solid reference for reconstructing vegetation and environmental changes using the delta C-13(BC) values. The delta C-13(BC) record in the DH99a sediment core spanning the last ca 10,000 years displayed large variations from -23.7 parts per thousand to -29.2 parts per thousand, which suggests that C3 plants dominantly occupied the Daihai Lake region during the Holocene. The most negative delta C-13(BC) peaks coincided with high values of tree percentages and grain sizes, which occurred under relatively wetter climatic conditions during the middle Holocene (ca 6500-3200 cal. yr BP) and an interval between 1700 and 1350 cal. yr BP. In contrast, the least negative delta C-13(BC) values corresponded to low values of tree percentages and grain sizes during relatively drier phases of the early and late Holocene. The generally negative correlation of the delta C-13(BC) values with the tree percentages and grain sizes was thought to reflect a negative correlation of the delta C-13(BC) values with the monsoon precipitation. This correlation is consistent with the response of carbon isotope in modern C3 plants to precipitation in north China. Therefore, we developed a computational model to reconstruct the changes in annual precipitation over the Daihai Lake region using the delta C-13(BC) values. The results indicated that the annual precipitation was highly variable, ranging from 170 mm lower to 310 mm higher than that at present during the middle Holocene, whereas the annual precipitation was generally similar to 70 mm lower than that at present during the early and late Holocene. The general features of the inferred precipitation changes using the delta C-13(BC) values are generally consistent with those reconstructed using pollen data of the same sediment core. Meanwhile, the delta C-13(BC) values tend to register some extreme variations of monsoon precipitation, which were not reflected in the pollen assemblages. We conclude that the delta C-13(BC) values in the Daihai Lake sediments may serve as a sensitive and reliable proxy for monitoring monsoon precipitation.

Wang Y. et al. Variation of molybdenum isotopes in molybdenite from porphyry and vein Mo deposits in the Gangdese metallogenic belt, Tibetan plateau and its implications // Miner. Depos. 2016. Vol. 51, № 2. P. 201–210.

We present Mo isotopic ratios of molybdenite from five porphyry molybdenum deposits (Chagele, Sharang, Jiru, Qulong, and Zhuonuo) and one quartz-molybdenite vein-type deposit (Jigongcun) along the Gangdese metallogenic belt in the Tibetan Plateau. These deposits represent a sequence of consecutive events of the India-Asia collision at different periods. Additional molybdenite samples from the Henderson Mo deposit (USA), the oceanic subduction-related El Teniente (Chile), and Bingham (USA) porphyry Cu-(Mo) deposits were analyzed for better understanding the controls on the Mo isotope systematics of molybdenite. The results show that molybdenite from Sharang, Jiru, Qulong, and Zhuonuo deposits have similar delta Mo-97 (similar to 0 aEuro degrees), in agreement with the values of the Henderson Mo deposit (-0.10 aEuro degrees). In contrast, samples from the Changle and Jigongcun deposit have delta Mo-97 of 0.85 aEuro degrees to 0.88 aEuro degrees and -0.48 %, respectively. Molybdenite from the El Teniente and Bingham deposits yields intermediate delta Mo-97 of 0.27 and 0.46 aEuro degrees, respectively. The Mo isotopes, combined with Nd isotope data of the ore-bearing porphyries, indicate that source of the ore-related magmas has fundamental effects on the Mo isotopic compositions of molybdenite. Our study indicates that molybdenite related to crustal-, and mantle-derived magmas has positive or negative delta Mo-97 values, respectively, whereas molybdenite from porphyries formed by crust-mantle mixing has delta Mo-97 close to 0 aEuro degrees. It is concluded that the Mo isotope composition in the porphyry system is a huge source signature, without relation to the tectonic setting under which the porphyry deposits formed.

White W.M. Isotopes, DUPAL, LLSVPs, and Anekantavada // Chem. Geol. 2015. Vol. 419. P. 10–28.

The mantle perspective provided by radiogenic isotope geochemistry has evolved over the last 40 years. Although the idea of an upper mantle depleted in incompatible elements by extraction of partial melt remains, ideas about the lower mantle have evolved from simple primitive material occupying the lower two-thirds of the mantle to a heterogeneous, multicomponent lower mantle. The lower mantle is sampled by plumes rising from it, and although each is compositionally unique, these plumes can be divided into 5 or 6 genera with the compositional similarity within each suggesting they have evolved in similar ways. The dominant signature in these plumes is that of lithospheric material carried into the deep mantle through subduction, subduction erosion, and continental foundering, and these processes have also polluted and refertilized the depleted upper mantle. The stable isotope geochemistry of these plumes confirms the presence of recycled material, including material derived fromthe continents, oceans and atmosphere. Noble gas isotope ratios provide a dramatically different perspective: that of reservoirs of noble gases isolated from the convecting mantle for the entire history of the Earth. Neither perspective is likely to be wrong and the conclusion to be drawn is that plumes, at least some of them, draw on reservoirs of both recycled and primitive material from the deep mantle. The difference in noble gas content in the primitive and recycled material may well be such that the primitive noble gas isotopic signature dominates in any mixture of these. In the meantime, the suprachondritic Nd-142/Nd-144 ratio of the modern mantle has reopened the question of the composition of the Earth and therefore primitive mantle. If this is not entirely a result of nebular isotopic heterogeneity, then "primitive mantle", defined as the composition that has given rise to the lithosphere and convecting mantle, appears to be depleted in light rare earths, and likely other incompatible elements such as U and Th. This material would have eNd in the range of 3 to 7, which matches the most common compositions observed in oceanic island basalts, particularly those of the PREMA genera. PREMA cannot be truly primitive mantle, even defined in this way, instead, it appears to consist of balanced mix of recycled enriched and depleted components with only a limited contribution from long-isolated, nearly primitive material. As the geochemical perspective of the mantle has evolved, so has the geophysical one, and it now reveals a highly heterogeneous lowermost mantle dominated by two large low-shear-wave velocity provinces (LLSVPs) beneath Africa and the South Pacific and associated with the DUPAL anomaly. The latter appears to actually be two anomalies, DUPAL and SOPITA, each closely associated with an LLSVP. Mantle plumes have nowbeen shown to preferentially rise from the margins of these structures, while subduction zones overly apparently cold high-seismic velocity regions surrounding the LLSVPs. The LLSVPs appear to be both hot and dense, and may consist of the PRIMA-like mixture of recycled and primitive material present in many mantle plumes. Geoneutrino studies may eventually resolve some of these questions, including both the total amount of U and Th in the Earth and whether these elements are concentrated within the LLSVPs.

Wing B.A., Farquhar J. Sulfur isotope homogeneity of lunar mare basalts // Geochim. Cosmochim. Acta. 2015. Vol. 170. P. 266–280.

We present a new set of high precision measurements of relative S-33/S-32, S-34/S-32, and S-36/S-32 values in lunar mare basalts. The measurements are referenced to the Vienna-Canyon Diablo Troilite (V-CDT) scale, on which the international reference material, IAEA-S-1, is characterized by delta S-33 = -0.061%, delta S-34 = -0.3% and delta S-36 = -1.27%. The present dataset confirms that lunar mare basalts are characterized by a remarkable degree of sulfur isotopic homogeneity, with most new and published SF6-based sulfur isotope measurements consistent with a single mass-dependent mean isotopic composition of delta S-34 = 0.58 +/- 0.05%, Delta S-33 = 0.008 +/- 0.006%, and Delta S-36 = 0.2 +/- 0.2%, relative to V-CDT, where the uncertainties are quoted as 99% confidence intervals on the mean. This homogeneity allows identification of a single sample (12022, 281) with an apparent S-33 enrichment, possibly reflecting cosmic-ray-induced spallation reactions. It also reveals that some mare basalts have slightly lower d34S values than the population mean, which is consistent with sulfur loss from a reduced basaltic melt prior to eruption at the lunar surface. Both the sulfur isotope homogeneity of the lunar mare basalts and the predicted sensitivity of sulfur isotopes to vaporization-driven fractionation suggest that less than approximate to 1-10% of lunar sulfur was lost after a potential moon-forming impact event.

Wittig N. et al. Coupled W-Os-Pt isotope systematics in IVB iron meteorites: In situ neutron dosimetry for W isotope chronology // Earth Planet. Sci. Lett. 2013. Vol. 361. P. 152–161.

Tungsten isotope compositions of magmatic iron meteorites yield ages of differentiation that are within +/- 2 Ma of the formation of CAIs, with the exception of IVB irons that plot to systematically less radiogenic compositions yielding erroneously old ages. Secondary neutron capture due to galactic cosmic ray (GCR) irradiation is known to lower the epsilon W-182 of iron meteorites, adequate correction of which requires a measure of neutron dosage which has not been available, thus far. The W, Os and Pt isotope systematics of 12 of the 13 known IVB iron meteorites were determined by MC-ICP-MS (W, Os, Pt) and TIMS (Os). On the same dissolutions that yield precise epsilon W-182, stable Os and Pt isotopes were determined as in situ neutron dosimeters for empirical correction of the ubiquitous cosmic-ray induced burn-out of W-182 in iron meteorites. The W isotope data reveal a main cluster with epsilon W-182 of similar to-3.6, but a much larger range than observed in previous studies including irons (Weaver Mountains and Warburton Range) that show essentially no cosmogenic effect on their epsilon W-182. The IVB data exhibits resolvable negative anomalies in epsilon Os-189 (-0.6 epsilon) and complementary epsilon Os-199 anomalies (+0.4 epsilon) in Tlacotepec due to neutron capture on Os-189 which has approximately the same neutron capture cross section as W-182, and captures neutrons to produce Os-199. The least irradiated IVB iron, Warburton Range, has epsilon Os-189 and epsilon Os-199 identical to terrestrial values. Similarly, Pt isotopes, which are presented as epsilon Pt-192, epsilon Pt-194 and epsilon Pt-198 range from +4.4 epsilon to +53 epsilon, +1.54 epsilon to -0.32 epsilon and +0.73 epsilon to -0.20 epsilon, respectively, also identify Tlacotepec and Dumont as the most GCR-damaged samples. In W-Os and W-Pt isotope space, the correlated isotope data back-project toward a 0-epsilon value of epsilon Pt-192, epsilon Os-189 and epsilon Os-199 from which a pre-GCR irradiation epsilon W-182 of -3.42 +/- 0.09 (2 sigma) is derived. This pre-GCR irradiation epsilon W-182 is within uncertainty of the currently accepted CAI initial epsilon W-182. The Pt and Os isotope correlations in the IVB irons are in good agreement with a nuclear model for spherical irons undergoing GCR spallation, although this model over-predicts the change of epsilon W-182 by similar to 2x, indicating a need for better W neutron capture cross section determinations. A nucleosynthetic effect in epsilon W-184 in these irons of -0.14 +/- 0.08 is confirmed, consistent with the presence of Mo and Ru isotope anomalies in IVB irons. The lack of a non-GCR Os isotope anomaly in these irons requires more complex explanations for the production of W, Ru and Mo anomalies than nebular heterogeneity in the distribution of s-process to r-process nuclides.

Wittkop C. et al. Carbon- and oxygen-stable isotopic signatures of methanogenesis, temperature, and water column stratification in Holocene siderite varves // Chem. Geol. 2014. Vol. 389. P. 153–166.

Manganoan siderite ([Fe,Mn]CO3) occurs in abundance of up to 19% (dry weight) as the sole endogenic carbonate within a succession of Holocene, organic-rich, varved sediments from freshwater Otter Lake (OL), Michigan. Radiocarbon dating and varve counts from a 7-m piston core constrain periods of major siderite accumulation to sediments older than 1200 cal yr BP. Sediment petrography suggests that siderite was a seasonal precipitate confined to the summer layer of the varve couplet. Bulk-sediment chemistry reveals cycles in abundance of manganese and aluminum coincident with centennial-scale cycles of siderite accumulation. Siderite delta C-13 and delta O-18 are enriched when the mineral is abundant and depleted when it is least abundant. Samples with high abundance of siderite precipitated in oxygen isotopic equilibrium with modern lake water, but are delta C-13 enriched relative to modern waters. Samples from intervals of low siderite abundance are delta C-13 and delta O-18 depleted relative to equilibrium with modern lake water. These data suggest that abundant siderite precipitation occurred when the OL water column was ferruginous (iron meromictic), allowing for enhanced ferrous iron concentrations and dissolved inorganic carbon (DIC) enriched in delta C-13 below the chemocline, where methanogenesis in waters and sediments influenced DIC composition. Seasonal siderite precipitation was triggered by water column alkalinity fluctuations driven by summer calcite dissolution. Manganese substitution in siderite lowered kinetic barriers to low-temperature mineral precipitation. Climate changes and basin filling influenced lake stratification and the rate of siderite precipitation. The siderite occurrence reported here displays remarkable similarity to its occurrence in Paleogene maar lake deposits, suggesting that further studies of Holocene lacustrine siderites may provide insight into ancient sedimentary systems and environments.

Wu W.N., Schmitt A.K., Pappalardo L. U-Th baddeleyite geochronology and its significance to date the emplacement of silica undersaturated magmas // Am. Miner. 2015. Vol. 100, № 10. P. 2082–2090.

Baddeleyite is a frequently found accessory mineral in silica undersaturated lavas. Because it is typically enriched in uranium, while having low initial lead, baddeleyite has long been a prime target for U-Pb geochronology of mafic rocks. The difficulties in retrieving small baddeleyite grains from volcanic samples and the lack of a detailed understanding of baddeleyite occurrence, however, have limited baddeleyite chronology largely to coarse-grained mafic intrusive rocks. Here, the development of U-Th in situ baddeleyite analysis using secondary ionization mass spectrometry (SIMS) is presented together with an assessment of baddeleyite occurrence in Quaternary silica-undersaturated lavas from Campi Flegrei (Naples, Italy). Samples studied comprise the pre- and post Campanian Ignimbrite (ca. 40 ka) lava domes of Cuma and Punta Marmolite, and Astroni and Accademia, respectively. The in situ sample preparation required initial identification of baddeleyite crystals from sawed and polished rock billets using scanning electron microscope (SEM) backscatter imaging and energy-dispersive X-ray analysis. U-Th baddeleyite isochron ages for intra-caldera Astroni and Accademia lava domes are 5.01(-2.55)(+2.61)A ka (MSWD = 2.0; n = 17) and 4.36(-1.12)(+1.13) ka (MSWD = 2.9; n = 24), respectively. The ages for Punta Marmolite (62.4(-3.08)(+3.9) ka; MSWD = 1.2; n = 11) and Cuma (45.91(-3.5)(+3.6) ka; MSWD = 2.2; n = 11) predate the Campanian Ignimbrite. Rapid baddeleyite crystallization at the time of emplacement is supported by petrologic observations that >50% of the baddeleyite crystals documented in this study occur either in vesicles or in vesicle-rich regions of the host lavas whose textures developed over timescales of a few years to a few decades based on microlite crystal size distribution (CSD) analysis. Radiometric U-Th baddeleyite ages are mostly in agreement with previously determined K-Ar eruption ages, except for the Punta Marmolite lava dome whose U-Th baddeleyite age predates the K-Ar age by ca. 15 ka. Baddeleyite thus records eruptive emplacement with little evidence for significant pre-eruptive crystal residence, and has potential as an eruption chronometer for Quaternary silica-undersaturated volcanic rocks.

Балтыбаев Ш.К. Свекофеннский ороген Фенноскандинавского щита: вещественно-изотопная зональность и ее тектоническая интерпретация // Геотектоника. 2013. №6. С.44-59.

В пределах Свекофеннского орогена Фенноскандии эндогенные события в виде интрузивной активности и регионального метаморфизма проявлены асинхронно в разных частях этой структуры. Изотопные данные позволяют выделить два этапа регионального высокотемпературного метаморфизма и сопряженного с ним плутонизма: раннесвекофеннский и позднесвекофеннский. Вещественный состав, особенности строения, а также несинхронность пиков эндогенной активности в пределах орогена предполагают необходимость выделения в составе свекофеннид, по меньшей мере, двух зон ? внутренней и внешней. Латеральная неоднородность орогена в современных координатах прослеживается от края архейского кратона к югу. Зона сочленения Свекофеннского орогена и архейского Карельского кратона характеризуется переходом значений величины Nd гранитоидов с возрастом 1.9 млрд лет от отрицательных к положительным, что указывает на уменьшение вклада архейского корового материала в образование протерозойских гранитоидов по мере движения с севера на юг в сторону протерозойского домена. С учетом латеральной неоднородности, проявленной в Свекофеннском орогене на вещественном и изотопно-геохимическом уровнях, а также асинхронной кульминации эндогенных событий в разных частях этого орогена, предложена новая схема тектонического районирования.

Бибикова Е.В. Ранняя кора Земли в свете изотопно-геохимических и изотопно-геохронологических данных // Мінералогічний журнал. 2014. Т. 36. № 2. С. 18-26.

Анализ изотопно-геохимических и изотопно-геохронологических данных, полученных в последние годы для образований ранней коры Земли, позволяет установить определенные ограничения на время возникновения, масштабы распространения и геохимические особенности первичной коры Земли. Наиболее информативными оказались изотопно-геохимические и геохимические данные, полученные по древнейшим цирконам с возрастом до 4,4 млрд лет, в том числе данные по Lu-Hf изотопной системе в цирконах, по короткоживущей 146Sm- 142Nd изотопной системе основных-ультраосновных пород зеленокаменных поясов, по изотопному составу свинца древнейших пород. Наличие положительной аномалии 142Nd в породах Западной Гренландии и отрицательной в амфиболитах древнейшего зеленокаменного пояса Нуввуагитук провинции Квебек свидетельствуют о ранней дифференциации вещества Земли на "обедненную" мантию и "обогащенную" (базальтовую) кору. Данные о поведении свинец-свинцовой изотопной системы в древнейших коровых образованиях Западной Гренландии и Лабрадора свидетельствуют о существовании "обогащенной" коры, имевшей базальтовый состав и высокое значение по величине m ( 238U/ 204Pb = 10,9) уже 3,9 млрд лет назад.

Борисов А.А., Дубинина Е.О. Влияние структурообразующих катионов на фракционирование изотопов кислорода между силикатными расплавами: экспериментальное исследование при 1400-1570°С // Петрология. 2014. Т. 22. № 4. С. 380-404.

Экспериментально изучено поведение изотопного состава кислорода в силикатных расплавах, значительно варьирующих по содержанию структурообразующих катионов. Изотопное уравновешивание расплавов Di-An эвтектики, модифицированных добавками Si, Al, Ti и Fe, проводилось в вертикальной трубчатой печи в области температуры от 1400 до 1570°С. Установлено, что при 1400 и 1450°С величина 103Ln между кислым и основным расплавами закономерно возрастает с увеличением содержания SiO2, достигая 1 при обогащении расплава кремнеземом на 20 мас. %. Влияние содержаний Fe2O3, TiO2 и Al2O3 изучалось при 1500°С. При увеличении Fe2O3 от 5 до 20 мас. % величина 18 возрастает на 0.4. Возрастание содержаний Ti и Al приводит к нелинейному поведению величин 18, которые уменьшаются в области максимальных содержаний TiО2 (28.4 мас. %) и Al2О3 (29.3 мас. %). В области умеренных содержаний Fe2O3, TiO2 и Al2O3 наблюдается монотонная прямая зависимость величин 18 от содержания оксидов. На основании экспериментальных данных рассмотрены методы оценки коэффициентов фракционирования изотопов кислорода при Т > 1400°C в изученной области вариаций содержания породообразующих оксидов. Расчет коэффициентов фракционирования с использованием индекса I18O показал, что с возрастанием кремнекислотности экспериментальные величины нелинейно отклоняются от значений, предсказываемых расчетом на 0.3 в области основных и на 0.5?0.6 в области кислых составов. Аналогичная картина наблюдается при аппроксимации расплава нормативным минеральным составом. Расчет с использованием индекса Гарлика приводит к систематическому занижению расчетных величин 103Ln коэффициентов фракционирования по сравнению с экспериментальными в среднем на 0.3 . Отношение NBO/T оказалось наиболее эффективным параметром для описания 103Ln в системе расплав-расплав, в том числе в области высокожелезистых составов.

84. 033165
Буйкин А.И., Камалеева А.И., Мигдисова Н.А. Информативность и перспективы применения метода ступенчатого дробления при изучении флюидной фазы пород и минералов // Петрология. 2016. Т. 24. № 3. С. 325-336.

Показаны возможности метода ступенчатого дробления для исследования флюидной фазы геологических объектов. Благодаря эффективному разделению газов из флюидных включений разных генераций, захваченных в процессе роста минерала и/или в ходе последующих его преобразований (метасоматических, гидротермальных), метод ступенчатого дробления позволяет получать изотопные характеристики конечных членов и, таким образом, надежно выявлять источники флюидов и отслеживать их эволюцию в магматическом и постмагматическом процессах, дает ключ к лучшему пониманию взаимодействия таких глобальных резервуаров, как мантия, кора и атмосфера. Информативность получаемых с помощью этого метода данных продемонстрирована на примере результатов исследований мантийных пород и минералов из разных геологических обстановок (MORB, СКЛМ, карбонатизированная мантия). Показано, что мульти-изотопный подход дает более полную информацию о генетических особенностях и эволюции флюидной фазы. Важность сочетания изотопно-геохимического и термобарогеохимического подходов представлена на примере мантийного ксенолита гранатового лерцолита из Оазиса Джетти. В совокупности с термобарогеохимическими методами исследования и при развитии лазерных методик вскрытия отдельных включений метод ступенчатого дробления позволяет разрешить одну из первостепенных практических задач - получение информации о геохимических особенностях и физико-химических параметрах минералообразующих (и рудообразующих) процессов.

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Буякайте М.И., Лаврушин В.Ю. и др. Изотопные системы стронция и кислорода в водах грязевых вулканов Таманского полуострова // Литология и полезные ископаемые. 2014. № 1. С. 52-59.

В 10 из 11 проанализированных проб вод грязевых вулканов Таманского полустрова отношения 87Sr/86Sr находятся в пределах 0.70734-0.70957, которые практически совпадают с интервалом, характерным для осадочных карбонатов мезозойского и кайнозойского возраста, но резко отличаются от 87Sr/86Sr в глинистых отложениях майкопской серии (0.7157 ± 0.0022). Эти данные свидетельствуют об определяющем влиянии на изотопный состав Sr карбонатных коллекторов и относительно малой роли элизионных растворов. Влияние последних заметно лишь в воде вулкана Гладковский (87Sr/86Sr = 0.71076). Высокие значения 18 в грязевулканических водах (до 14.2) также могут интерпретироваться как результат изотопного обмена с осадочными карбонатами при температурах порядка 150°.

Вавилин В.А. Описание кинетического эффекта фракционирования стабильных изотопов азота в процессе нитрификации // Водные ресурсы. 2014. Т. 41. № 3. С. 319-324.

Предложена математическая модель, позволяющая оценить динамику стабильных изотопов азота 14N и 15N в процессе нитрификации - превращение аммония в нитриты и нитраты. Для калибровки модели использованы экспериментальные данные, в которых нитрит - конечный продукт нитрификации. Модель, в которой используется традиционная зависимость Моно, позволила описать нелинейную динамику фракционирования и уточнить кинетические коэффициенты процесса нитрификации.

Васильев С.С., Дергачев В.А. и др. Долговременные изменения потока космогенного изотопа 10Be за последние 10 тысяч лет, вариации геомагнитного поля и климат // Геомагнетизм и аэрономия. 2012. Т. 52. № 1. С. 127-137.

Проведен спектральный анализ данных по потоку космогенного 10Be в керне льда со станции Summit, Центральная Гренландия (проект GRIP) за последние 10 тыс. лет. Показано, что поток 10 меняется циклически. Наиболее значимый цикл имеет период 2300 лет. Выполнен анализ изменений положения виртуального геомагнитного полюса за 8 тыс. лет. На периодограмме долготы виртуального геомагнитного полюса обнаружены значимые компоненты, указывающие на циклическое изменение положения геомагнитного полюса с периодом 2300 лет. Кроме 2300-летнего цикла, на периодограмме данных по потоку 10 наблюдается ряд линий, присутствие которых можно рассматривать как проявление 1000-летнего цикла в скорости осаждения 10 на поверхность ледника. Обсуждается связь цикличности положения геомагнитного полюса и потока 10.

Высоцкий С.В., Игнатьев А.В. Особенности соотношения изотопов кислорода в благородных опалах // Тихоокеанская геология. 2013. Т. 32. № 6. С. 64-67.

В статье приводятся результаты исследования ? 18О в благородных опалах Приморья (месторождение Радужное), Австралии, Эфиопии и современных опалах из гидротерм вулкана Менделеева (о. Кунашир, Курильские острова). Установлено, что соотношение изотопов кислорода в опалах может служить критерием оценки температуры их образования. Низкотемпературные осадочные опалы обладают относительно “тяжелым” изотопным составом кислорода, независимо от того, в каких породах они сформировались – осадочных или вулканогенных. Примером могут служить австралийские и словацкие опалы А-типа. Гидротермальные опалы характеризуются более “легким” изотопным составом кислорода, который зависит от температуры осаждения из раствора. Чем выше температура раствора, тем “легче” изотопный состав кислорода выпадающего из него опала и тем ближе он к изотопному составу кислорода самого гидротермального раствора.

Дубинина Е.О., Бортников Н.С., Силантьев С.А. Отношение флюид–порода в процессах серпентинизации океанических ультраосновных пород, вмещающих гидротермальное поле Лост Сити, 30° C.Ш., САХ // Петрология. 2015. Т. 23. № 6. С. 589-606.

Оценка отношения флюид/порода (W/R) по изотопно-кислородным характеристикам является специфичной для процессов серпентинизации, поскольку они сопровождаются не только изменением стехиометрических соотношений кислорода во флюиде и в породе, но и формированием сопутствующих серпентину минералов. Учет этих факторов необходим для обстановок, предполагающих ограниченную роль водного флюида, например, глубинной серпентинизации пород океанической литосферы в условиях низких скоростей спрединга. В работе изучены изотопные характеристики образцов, отобранных при погружении ГОА “МИР” в 50-м рейсе НИС “Академик Мстислав Келдыш”, вдоль вертикального профиля на южном склоне массива Атлантис, на котором расположено гидротермальное поле Лост Сити. Почти все изученные серпентиниты имеют гомогенный изотопный состав стронция, соответствующий таковому составу современной океанической воды. Изотопный состав кислорода серпентинитов закономерно изменяется в зависимости от глубины отбора образца, общий интервал изменения величины 18 составляет от 2.6 до 6.1 . Закономерные вариации указывают на сохранность стратиграфической позиции образцов в разрезе массива Атлантис и свидетельствует о глобальной серпентинизации всей толщи плутонических пород массива. Мы провели оценку отношения флюид?порода при серпентинизации в закрытой относительно флюида системе, используя модель растворения-кристаллизации, которая учитывает переменную стехиометрию кислорода и влияние параллельного формирования брусита на изотопный состав новообразованного серпентина. Результаты моделирования показывают, что при умеренно-повышенных температурах ( 300°C) существует область 0.1 < W/R < 5, характеризующаяся резкими вариациями изотопного состава кислорода как во флюиде (1.3?7.8 ), так и кристаллизующихся минералах ? серпентине (2.5?8.9 ) и брусите (от ?4.5 до 1.9 ). Модель объясняет наблюдаемый диапазон вариаций величин 18 в серпентинизированных гарцбургитах массива Атлантис. По нашим оценкам, наиболее вероятными условиями серпентинизации пород изученного разреза массива Атлантис являлись Т = 270?350°C при отношении W/R = 0.7?3. При более низкотемпературной серпентинизации, например при Т = 250°C, отношение W/R могло достигать 6. Современный процесс серпентинизации глубинных зон массива Атлантис, в котором участвует флюид поля Лост Сити, протекает при Т > 270°C и отношении W/R < 1. Эти условия аналогичны условиям серпентинизации гарцбургитов нижних частей изученного разреза массива Атлантис.

Дубинина Е.О., Чугаев А.В. и др. Источники вещества и флюидный режим формирования кварц-карбонатных жил на месторождении золота Сухой Лог, Байкало-Патомское нагорье // Петрология. 2014. Т. 22. № 4. С. 347-379.

Комплексное изотопно-геохимическое ( 18, 13, 87Sr/86Sr, 143Nd/144Nd, состав РЗЭ) изучение минералов кварц-карбонатных жил и метаосадочных пород позволило установить источник вещества и оценить флюидный режим формирования минерализации малосульфидного золото-кварцевого типа на месторождении Сухой Лог. Для изотопно-кислородной термометрии кварцевых жил проведена калибровка эмпирической зависимости коэффициентов фракционирования изотопов кислорода между жильным кварцем и околожильными измененными породами. Температурный интервал изотопного уравновешивания кварца с измененными зонами околожильных вмещающих пород составил 380?190°C. Независимые оценки температуры, полученные по данному термометру, показывают, что жильный анкерит является как более ранним, так и более поздним по отношению к жильному кварцу. Изотопная ( 13, 18) систематика анкерита кварц-карбонатных жил, карбонатов рудовмещающих сланцев хомолхинской и имняхской свит в пределах и за пределами рудных зон месторождения показывает, что в околожильных породах и жилах рудной зоны присутствует привнесенный карбонат, вероятным источником которого являются карбонатные толщи имняхской свиты. Состав РЗЭ жильного анкерита указывает на их перенос во флюиде в карбонатных комплексах. Поведение отношений Eu/Eu* и (La/Yb)n и содержания Mn в жильном анкерите характерны для кристаллизации анкерита в закрытой относительно флюида системе. С помощью изотопной Sr-Nd систематики установлено, что в формировании изотопных параметров жильного анкерита принимали участие метаосадочные вмещающие породы как имняхской, так и хомолхинской свит, контрастные по изотопному составу Nd. Расчет отношений флюид/порода в процессе формирования околожильных изменений вмещающих пород проведен для двух вариантов термальной истории: с постоянным источником тепла под структурой Сухого Лога и при линейном остывании структуры. Рассчитанные эффективные интегральные отношения W/R находятся в интервале от 0.046 до 0.226 и указывают на образование жильных тел месторождения с участием флюида дегидратационной или метаморфогенной природы. Низкие отношения W/R противоречат механизму кристаллизации кварца кварц-карбонатных жил за счет пересыщения флюида относительно SiO2 на фоне снижения температуры. В качестве основного механизма нами рассмотрено формирование кварцевых жил за счет вариаций пересыщения флюида, вызванных перепадами давления (“pressure solution”). С этим предположением согласуются приведенные изотопно-геохимические характеристики околожильных пород на месторождении Сухой Лог.

Зыкин Н.Н., Сокерина Н.В. Генезис вод гидротермальных месторождений Приполярного Урала // Вестник института геологии Коми научного центра Уральского отделения РАН. 2015. № 9 (249). С. 18-23.

Генезис гидротермальных месторождений во многом определяется источником и генезисом вод рудообразующих флюидов. С целью выявления генезиса золоторудных и кварцевых месторождений Приполярного Урала проведены изотопные исследования водорода (dD) и кислорода (d 18O) водной и газовой фаз из флюидных включений сингенетичных с рудами минералов. Приведены данные по изотопному составу кислорода и водорода вод современных гидротермальных систем, dD и d 18O вод из флюидных включений других гидротермальных месторождений мира и изотопному составу вод их возможных источников (метеогенных, захоронённых, метаморфогенных, «ювенильных»). Показано, что в рудообразующих растворах месторождений Приполярного Урала, как и других гидротермальных месторождений, доминирует вода метеогенного генезиса и вода дегидратации OH --содержащих минералов.

Киквадзе О.Е., Лаврушин В.Ю. и др. Изотопный и химический состав грязевулканических газов Таманского полуострова и проблема их генезиса // Литология и полезные ископаемые. 2014. № 6. С. 525-538.

Исследованы вариации изотопного состава углерода в грязевулканических газах и водах Таманского полуострова. Величины 13 в СН4 и СО2 меняются в диапазонах от -59.5 до -44.0 ( 13Cсредн = 52.4 ± 5.4 ) и от -17.8 до +22.8 ( 13Cсредн = +6.9 ± 9.3 ) соответственно. Вариации значений 13СTDIC в водах большинства грязевых вулканов полуострова составляют +3.3... +33.1 , но в редких случаях встречаются и более низкие их значения - до -12 . Фракционирование изотопов углерода в системе СО2 НСО3 вод соответствует изотопному равновесию при температурах земной поверхности. Рост концентрации углекислоты в газовой фазе и увеличение концентрации НСО3-иона в их водной фазе сопровождается обогащением последнего тяжелым 13. На величину 13СTDIC в водорастворенном углероде, помимо его исходного состава, влияет время нахождения воды на поверхности земли (обмен с атмосферной СО2, окисление метана, осаждение карбонатов и т.п.). За счет этого флуктуации значений 13СTDIC в сальзах со стоячей водой могут достигать 10-20 . В глинистой пульпе концентрация карбонатного вещества в пересчете на СаСО3 составляет от 1-4 до 36-50% вес. Значение 13 в нем варьирует от -3.6 до +8.4 . Карбонатное вещество глинистой пульпы представляет собой смесь седиментогенных и аутигенных карбонатов, поэтому в большинстве случаев по валовому изотопному составу углерода оно неравновесно с водорастворенными формами СО2.

Коваленко Д.В., Лебедев В.И. и др. Геодинамические условия формирования и источники раннекембрийских доаккреционных магматических комплексов Западной Монголии// Петрология. 2016. Т. 24. № 2. С. 194-211.

Проведены изотопные и геохимические исследования раннекембрийских лав Озерной зоны Монголии. По спектрам концентраций элементов-примесей их можно разделить на несколько групп: (1) близкие к N-MORB; (2) близкие к E-MORB; (3) обогащенные элементами-примесями базальты с минимумами высокозарядных (HFSE) элементов и (4) деплетированные элементами-примесями базальты с минимумами HFSE. Все типы лав могли образоваться в системе островная дуга?задуговый бассейн. Магматические породы группы (1), вероятно, формировались в задуговом спрединговом бассейне. Магматические породы группы (2), возможно, образовывались в области действия горячей точки мантии или при плавлении обогащенных участков гетерогенной верхней мантии. Лавы группы (3), по-видимому, являются фрагментами энсиматической относительно примитивной островной дуги. Базальты и андезибазальты группы (4), вероятно, являются результатом смешения расплавов группы (1) и (3). Чередование в едином разрезе лав группы (1) и (4) показывает, что зоны растяжения и субдукции были сближены и действовали одновременно. Магмы групп (1), (2) и (3) выплавлялись из отличающихся источников мантии, характеризующихся различными величинами отношений элементов-примесей и разным изотопным составом

Костицын Ю.А., Белоусова Е.А., Силантьев С.А., Бортников Н.С., Аносова М.О. Современные проблемы геохимических и U–Pb геохронологических исследований циркона в океанических породах // Геохимия. 2015. № 9. С. 771-800.

Приводятся результаты исследования методом лазерной абляции (LA-ICP-MS) зерен циркона, выделенного из магматических пород впадины Маркова и гидротермального поля Ашадзе (Срединно-Атлантический хребет). Изучены U-Pb и Lu-Hf изотопные системы индивидуальных зерен циркона и их микроэлементный состав. Также исследованы Sm-Nd и Rb-Sr изотопные системы пород, содержащих циркон. U-Pb система зерен циркона трех образцов габбро-норитов впадины Маркова показала значения возраста от 0.90 ± 0.02 до 2.00 ± 0.05 млн лет, причем более молодой возраст оказался у образцов, драгированных с большей глубины. Циркон из четырех образцов габбро и трондьемитов поля Ашадзе оказался одновозрастным - от 1.04 ± 0.07 до 1.12 ± 0.09 млн лет. В образце I-1069/19 плагиоклазового троктолита впадины Маркова были обнаружены экзотические зерна циркона с возрастом от 90 млн лет до 3.2 млрд лет, что не согласуется с возрастом пород в Срединно-Атлантическом хребте. В статье обсуждаются гипотезы происхождения подобных экзотических зерен, в частности, их образование в мантийных глубинах, попадание туда с субдуцированным материалом и др. Эксперименты по растворимости циркония показывают, что основные и ультраосновные расплавы могут стать пересыщенными относительно циркония только при нереально высоких его содержаниях, которых в соответствующих породах обычно не встречаются. Инородный, захваченный циркон в расплавах основного и ультраосновного состава должен растворяться и его находки в этих породах, скорее всего, указывают на отсутствие равновесия. Циркон может формироваться в интрузивных породах основного состава в условиях фракционной кристаллизации на заключительных ее стадиях, поэтому в габброидах нередко присутствует собственный циркон.

Крылов Д.П., Шуколюков Ю.А. Xes-Xen термохронология рейнерского метаморфического комплекса Земли Эндерби (Восточная Антарктида, район станции Молодежная) // Петрология. 2014. Т. 22. № 5. С. 469-481.

В результате выполненного в настоящей работе Xes-Xen датирования цирконов из пород рейнерского комплекса Земли Эндерби в районе станции Молодежная (побережье залива Алашеева) получены оценки возрастов 550 ± 50 млн лет и 1040 ± 30 млн лет. Метаморфические породы рейнерского комплекса сохранили свидетельства о двух главных событиях: во-первых, о кристаллизации магматических протолитов чарнокито- и эндербитогнейсов, а во-вторых, о наложенных структурно-метаморфических преобразованиях в условиях переходных от амфиболитовой до гранулитовой фаций (метаморфизм, регионально проявленный в породах рейнерского комплекса). Наиболее достоверные оценки возрастов, полученные Xes-Xen методом по цирконам магматического происхождения из чарнокито- и эндербитогнейсов, соответствуют гренвильскому этапу развития рейнерского комплекса (около 1.0 млрд лет). Изотопные системы ксенона цирконов метаморфического происхождения свидетельствуют о панафриканском этапе формирования рейнерского комплекса (600?550 млн лет). Панафриканские процессы отображаются в изотопной системе U-Xe в двух случаях: при кристаллизации метаморфогенных цирконов в это же время (при этом, вероятно, на возрастном спектре Xes-Xen получается плато) и при преобразовании исходных изотопных систем (при этом кажущиеся возрасты снижаются к низкотемпературным фракциям газа). Существенно, что вторичные преобразования с понижением кажущихся возрастов к значениям 600-550 млн лет затрагивают только те компоненты (т.е. приводят к выносу ксенона только из тех ловушек), которые неустойчивы при максимальных температурах метаморфизма, для которых вычисленные Tcl меньше 750°С (в условиях, переходных от амфиболитовой к гранулитовой фациям). Если же стабильность ксенона выше, то сохраняются “первичные” изотопные системы. Следовательно, возраст метаморфизма, переходного от амфиболитовой к гранулитовой фаций на основании Xes-Хеn датирования, оценивается в 600-550 млн лет. В целом результаты выполненных исследований свидетельствуют о том, что региональный метаморфизм рейнерского комплекса в районе станции Молодежная имеет возраст не около 1.0 млрд лет, как считалось ранее, а около 600-550 млн лет.

Лохов К.И., Прасолов Э.М. и др. Изотопно и элементно фракционированные He, Ne и Ar во флюидных включениях минералов метаморфических пород Северной Карелии с аномальным изотопно легким кислородом: фракционирование изотопов в эндогенном флюиде по механизму термодиффузии с каскадированием // Вестник Санкт-Петербургского университета. Серия 7. Геология. География. 2016. № 1. С. 29-47.

Изучены изотопы гелия и аргона во флюидных включениях минералов корундсодержащих пород с аномальным изотопно легким кислородом Хитоострова (северная Карелия, Россия). Изотопный состав аргона показывает, что атмосферная компонента благородных газов отсутствует. Поэтому все ранее предложенные модели участия во флюиде поверхностных талых вод высокоширотных ледников являются несостоятельными. Установлено закономерное уменьшение величин отношений He/Ar и Ne/Ar от вмещающих пород к центру тела с корундовыми породами. Это указывает на то, что существовал поперечный термический градиент. Установлено, что изотопный состав гелия существенно отличен во вмещающих породах и в корунд-содержащих, при этом наблюдается тренд корреляции обогащения легкими изотопами как гелия, так и кислорода. Это позволило впервые предложить и обосновать эндогенный механизм фракционирования изотопов кислорода и других химических элементов по механизму термической диффузии. Геологически обосновано существование эффекта каскадирования разделительных ячеек, что обуславливает существенные изотопные эффекты. Эффект каскадирования достигается за счет «флюидного насоса», в роли которого выступают амфиболизирующиеся габброиды на контакте с корундовыми породами. Предполагается, что данные механизм не является специфическим для случая корундсодержащих метасоматитов, которые являются частным случаем проявления такого сценария в процессах с участием эндогенных флюидных потоков в термоградиентных условиях. Библиогр. 33 назв. Ил. 10. Табл. 1.

Лысенко О.Б., Демихов Ю.Н., и др. Роль магнитного эффекта при фракционировании изотопов урана // Химическая физика. 2014. Т. 33. № 12. С. 49-52.

Исследовано влияние магнитного изотопного эффекта на реакции радикальных пар, содержащих радикал-ионы с тяжелым атомом (UO 2+ 2 ), что в дальнейшем может быть связано с решением практических задач с новым способом обогащения изотопов урана в химических реакциях за счет различия в их магнитных свойствах. Магнитный изотопный эффект урана может быть положен в основу эффективного метода разделения его изотопов (234U, 235U, 238U). На основании проведенных теоретических и экспериментальных исследований были обоснованы особенности поведения в химических реакциях природных и искусственных изотопов урана, обусловленные фундаментальными свойствами их ядер, а также возможность использования в виде ядерного топлива как отходов обогащенных урановых руд (хвосты в хвостохранилищах), так и отработанного ядерного топлива. Было также изучено поведение четных природных и искусственных изотопов изотопной смеси в ядерном топливе (232U, 234U, 236U), которые являются вредными примесями, поглощающими часть тепловых нейтронов и ухудшающими гомогенность топлива.

Малич К.Н., Баданина И.Ю. и др. U-Pb возраст и Hf-Nd-Sr-Cu-S изотопная систематика Бинюдинского и Дюмталейского рудоносных интрузивов (Таймыр, Россия) // Литосфера. 2016. № 1. С. 107-128.

Впервые охарактеризованы U-Pb возраст и Hf-Nd-Sr-Cu-S изотопно-геохимические особенности пород и сульфидных руд ультрамафит-мафитовых интрузивов п-ва Таймыр Российской Арктики. Цирконы Бинюдинского и Дюмталейского интрузивов характеризуются сходными U-Pb возрастами (245.7 ± 12 млн лет и 256.2 ± 0.89 млн лет соответственно), что свидетельствует о временной близости с толеит-базальтовым магматизмом Сибирской платформы. Cиликатное вещество Бинюдинского и Дюмталейского интрузивов характеризуется различными Hf-Nd-Sr изотопными параметрами (?Hf = -3.8 ± 1.3, ?Nd = -3.8 ± 0.4, 87Sr/86Sri = 0.70588 ± 0.00013 и ?Hf = 9.5 ± 2.5, ?Nd = 4.2 ± 0.7, 87Sr/86Sri = 0.70474 ± 0.00020 соответственно). Специфичность Hf-Nd-Sr изотопных характеристик пород Бинюдинского интрузива отражает взаимодействие примитивной магмы с литосферой, представленной веществом древней коры или субконтинентальной мантии, которые обладают сходными изотопными параметрами. Совокупность Hf-Nd-Sr изотопных характеристик Дюмталейского интрузива отвечает параметрам, характерным для “ювенильного” мантийного источника. Выявленные особенности U-Pb возраста и Hf-Nd-Sr изотопных составов пород Бинюдинского и Дюмталейского интрузивов отличаются от таковых промышленно-рудоносных интрузивов Норильской провинции, характеризующихся продолжительной магматической эволюцией со значительным временным интервалом образования циркона и бадделеита (от 350 до 230 млн лет), относительно постоянными значениями ?Nd (?1 ± 0.5), неоднородным ?Hf (от -2.3 до 16.3) и 87Sr/86Sri (от 0.70552 до 0.70798). По данным Cu-изотопной систематики, сульфидные руды Бинюдинского и Дюмталейского интрузивов обладают сходными вариациями ?65Cu (-0.4 ± 0.1 и -0.66 ± 0.42‰ соответственно), характерными для сульфидных руд Талнахского месторождения Норильской провинции. По данным S изотопной систематики, сульфидные руды Бинюдинского и Дюмталейского интрузивов значимо отличаются друг от друга (?34S = 1.5 ± 0.4 и ?34S = 11.4 ± 0.6‰ соответственно). Мы полагаем, что Cu-S изотопные характеристики сульфидных руд Бинюдинского и Дюмталейского интрузивов отражают их первичную характеристику и не являются результатом смешения источников или магматического фракционирования стабильных изотопов. Тем не менее последний вариант не может быть исключен для изотопно “тяжелой” S в составе сульфидных руд Дюмталейского интрузива. Изотопные составы S и Cu вкрапленных сульфидных руд Дюмталейского интрузива близки параметрам ?34S-?65Cu вкрапленных и массивных сульфидных руд промышленно-рудоносного Талнахского интрузива и могут рассматриваться как критерии перспективности обнаружения богатых платиноидно-медно-никелевых руд.

Малышев С.В., Худолей А.К. Источники сноса каменноугольно-нижнемеловых терригенных отложений северо-востока Сибирской платформы: результаты Sm-Nd изотопно-геохимических исследований // Геология и геофизика. 2016. Т. 57. № 3. С. 537-552.

Впервые проведены Sm-Nd изотопные исследования обломочных пород каменноугльно-раннемелового возраста северо-восточной окраины Сибирской платформы. Установлена и проинтерпретирована изменчивость изотопного состава осадков в данном временном интервале. Высокие значения ?Nd( t ) для каменноугольно-пермских отложений (от -11 до -2) свидетельствуют, что при их накоплении значительный вклад вносили продукты размыва островодужных и ювенильных комплексов, расположенных в каменноугольное время в Таймыро-Североземельском складчато-надвиговом поясе. Положительные значения ?Nd( t ) для песчаников триаса указывают на размыв близких по возрасту магматических пород трапповой формации. Верхнеюрские и особенно меловые отложения, формирующие Лено-Анабарский и Приверхоянский прогибы, характеризуются резко отрицательными значениями ?Nd( t ) от -15 до -19, указывающими на размыв зрелой континентальной коры. Карбон-триасовые комплексы, входящие в состав Верхоянского складчато-надвигового пояса, имеют более высокие значения ?Nd( t ) и не могли быть источником детритового материала для меловых песчаников. Отложения, заполняющие Приверхоянский краевой прогиб, формировались не за счет разрушения растущей к востоку горной системы, а за счет разрушения удаленных и гомогенизированных источников сноса с изотопными характеристиками древней коры. Такими потенциальными питающими провинциями могли быть выступы кристаллического фундамента Сибирской платформы, такие как Алданский щит.

Мартынов А.Ю., Мартынов Ю.А., Рыбин А.В., Кимура Д.И. Роль задуговых процессов в происхождении субдукционных магм: новые данные по изотопии Sr, Nd И Pb в вулканитах ранних этапов формирования о. Кунашир (Курильская островная дуга) // Геология и геофизика. 2015. Т. 56. № 3. С. 469-487.

Новые данные по изотопии Sr, Nd, Pb в разновозрастных преимущественно основных породах о. Кунашир (южное звено Курильской островной дуги) позволяют реконструировать главные события магматической эволюции субдукционной системы. Признаки участия высокотемпературного субдукционного осадочного компонента (расплава и/или надкритического флюида) в происхождении ранних миоцен-плейстоценовых базальтов тыловой зоны свидетельствуют о сравнительно высоких (> 800 °C) температурах на поверхности погружающейся океанической плиты. Голоценовые основные вулканиты как фронтальной, так и тыловой зон отличаются деплетированными изотопными характеристиками, отражающими преобладающую роль в их магмогенезисе низкотемпературного водного субдукционного компонента, образовавшегося в результате дегидратации измененной океанической коры тихоокеанского MORB типа. Смена геологических и изотопных характеристик вулканических продуктов в плейстоцене и голоцене связана, по-видимому, с изменением геодинамического режима развития задуговой Курильской котловины - прекращение активного растяжения и начало сжатия.

Недосекова И.Л., Белоусова Е.А., Беляцкий Б.В. U-Pb возраст и Lu-Hf изотопные системы цирконов Ильмено-Вишневогорского щелочно-карбонатитового комплекса, Южный Урал // Литосфера. 2014. № 5. С. 19-32.

В статье представлены результаты изотопного U-Pb датирования методом лазерной абляции (LA-ICP MS) цирконов из различных типов пород (карбонатитов, миаскитов, щелочных метасоматитов, гипербазитов) Ильмено-Вишневогорского щелочно-карбонатитового комплекса (ИВК) Южного Урала. Датирование циркона миаскитов показывает возраст ранних стадий кристаллизации щелочно-карбонатитовой магматической системы (T = 428 ± 8 млн лет). Возраст цирконов карбонатитов (T = 417.3 ± 2.8 млн лет) соответствует позднемагматической стадии кристаллизации остаточных щелочно-карбонатитовых расплавов. Кроме того, в различных породах ИВК (миаскитах, карбонатитах, гипербазитах) устанавливаются поздние генерации цирконов (T = 270-350 млн лет), формирование которых, по-видимому, связано с постколлизионными метаморфическими и метасоматическими процессами. Hf-изотопные данные, полученные для цирконов ИВК, подтверждают мантийный характер источника магм ИВК и указывают на участие в магмогенерации вещества умеренно обедненной мантии (DM) и более обогащенного в отношении нерадиогенного Hf источника (возможно, представляющего собой нижнекоровый компонент).

Недосекова И.Л., Беляцкий Б.В., Белоусова Е.А. Редкие элементы и изотопный состав гафния как индикаторы генезиса циркона при эволюции щелочно-карбонатитовой магматической системы (Ильмено-Вишневогорский комплекс, Урал, Россия) // Геология и геофизика. 2016. Т. 57. № 6. С. 1135-1154.

Приводятся результаты изучения особенностей химического (РЗЭ, высокозарядные литофилы) и изотопного состава (Hf) единичных зерен циркона и локального определения U-Pb возраста циркона, кристаллизовавшегося из щелочно-карбонатитовых магм ильмено-вишневогорского комплекса (Урал, Россия). Установлено, что состав раннего циркона (U-Pb возраст 430-410 млн лет) из щелочных пород и карбонатитов ильмено-вишневогорского комплекса (ИВК) определяется в основном эволюцией родительских флюидонасыщенных щелочно-карбонатитовых расплавов и в значительной мере связан с совместной кристаллизацией циркона и урансодержащих редкометалльных минералов (гатчеттолита и пирохлора) на заключительных стадиях функционирования магматической системы. Ранние генерации циркона ИВК имеют умеренно деплетированный изотопный состав Hf (?Hf = +11.3…+4.7) и подтверждают мантийный характер источника магм, указывая на участие в магмогенерации вещества DM типа и обогащенного источника. Значительные вариации начального изотопного состава Hf ранних генераций циркона свидетельствуют о многостадийном характере процесса кристаллизации циркона и участии различных порций расплава, отличающихся изотопным составом, определяемым смешением вещества в источнике. Поздние генерации циркона ИВК (U-Pb возраст 250-350 млн лет) имеют в значительной степени нарушенные «омоложенные» изотопные системы и химический состав, отличный от состава магматических цирконов. Эти цирконы, вероятно, были сформированы на метаморфогенном этапе развития ИВК без существенного привноса вещества.

Садыков С.А. Распределение стабильных изотопов углерода в кристаллах кальцита // Записки Российского минералогического общества. 2014. Т. 143. № 4. С. 34-44.

Выполнены исследования изотопного состава углерода в элементах анатомии кристаллов кальцита датолитового месторождения (Дальнегорск, Приморье). Исследовано 9 образцов кристаллов кальцита. Кристаллы имеют разный габитус и морфологическое строение. В каждом из представленных образцов наблюдаются неодинаковые значения ? 13C на разных гранях. Предложены возможные пути изменения изотопного состава углерода в элементах анатомии при образовании и росте исследованных кристаллов кальцита.

Садыхов Э.А., Шатова Н.В. Геохимические характеристики и изотопное U-Pb датирование пород плагиогранитового плутонического комплекса Лок-Гарабахской зоны Малого Кавказа (Азербайджан) // Региональная геология и металлогения. 2016. № 66. С. 67-74.

Проведены петрографические, петрохимические, геохимические и изотопные исследования пород байосского плагиогранитового комплекса Лок-Гарабахской тектонической зоны, включающие исследования микроэлементного состава, редкоземельных элементов и результаты U-Pb датирования (SHRIMP II), что позволило обосновать природу формирования комплекса. Полученные данные свидетельствуют о его образовании в гипабиссальных условиях островодужной системы в две последовательные стадии внедрения (180 и 170 млн лет).

Толстихин И.Н., Скиба В.И. и др. Места нахождения и происхождение благородных газов в минералах (на примере ильменита из щелочных гранитов Кольского полуострова) // Геохимия. 2014. № 12. С. 1099-1107.

Термический анализ выделения гелия из ильменита щелочных гранитов (Понойский массив, Кольский полуостров) и экстракция газов посредством дробления, плавления и ступенчатого нагрева образца в вакууме выявили несколько разных мест нахождения (мн) благородных газов в одном минерале. В диапазоне температур 400-600°C выделяются радиогенные 40Ar* и Не, при этом, несмотря на близкие температуры экстракции, газы занимают разные мн: захваченный избыточный 40Ar* находится в относительно крупных включениях (>10 мк) и почти полностью выделяется при дроблении (более 80%, первое мн), в то время как Не находится в “залеченных” -треках и выделяется при нагреве образца (второе мн). В третьем мн находится почти исключительно радиогенный Не, выделяющийся при температуре около 1100°C; в этой температурной фракции отношение 4He/40Ar* = 830, в то время как для образца в целом оно близко к 10. Из четвертого мн выделился гелий с наиболее высоким отношением 3He/4He = 1.1 ? 10-6, свидетельствующим о вкладе мантийного гелия. Наблюдаемое распределение изотопов гелия и аргона в ильмените согласуется с геологическими данными об эволюции пород Понойского массива. Кварц-полевошпатовая жила, из которых был отобран ильменит, образовались в результате кристаллизации остаточных щелочно-гранитных расплавов; расплавы содержали мантийный Не, попадающий в конечном итоге в первичные включения (четвертое мн). После формирования породы массива накапливали радиогенный 40Ar*, но теряли более подвижный радиогенный Не. Во время палео-протерозойского метаморфизма Понойского массива радиогенный 40Ar* выделился из К-содержащих минералов гранитов и был импрегнирован в “безкалиевый” ильменит (первое мн). В дальнейшем захваченный 40Ar* сохранялся во включениях в минерале, а возникавший in situ при радиоактивном распаде U и Th гелий преимущественно мигрировал из него. В настоящее время ильменит характеризуется значительным избытком 40Ar* и, одновременно, дефицитом 4He (второе и третье мн). Ни K-Ar, ни U-Th-He изотопные системы минерала не могут быть использованы для датирования.

Туркина О.М., Бережная Н.Г., Сухоруков В.П. Изотопный Lu-Hf состав детритового циркона из парагнейсов Шарыжалгайского выступа: свидетельства роста коры в палеопротерозое // Геология и геофизика. 2016. Т. 57. № 7. С. 1292-1306.

Изучен редкоэлементный и Lu-Hf изотопный состав цирконов из палеопротерозойских высокометаморфизованных осадочных пород (парагнейсов) ЮЗ окраины Сибирского кратона (Иркутный блок Шарыжалгайского выступа). Метаморфическая генерация циркона представлена оболочками и многоплоскостными кристаллами с возрастом ~1.85 млрд лет. Метаморфический циркон обеднен легкими и тяжелыми редкоземельными элементами вследствие субсолидусной перекристаллизации и/или формирования одновременно с минералами концентраторами РЗЭ - гранатом и монацитом. В отличие от метаморфического циркона детритовые ядра характеризуются высокими концентрациями тяжелых лантаноидов и высоким (Lu/Gd) n, что типично для цирконов магматического происхождения. Слабая положительная корреляция между 176Lu/177Hf и 176Hf/177Hf для ядер циркона доказывает изменение их изотопного состава в закрытой системе за счет радиоактивного распада, что позволяет использовать изотопные параметры этих цирконов для характеристики пород питающей провинции. Палеопротерозойские детритовые ядра циркона из парагнейсов с возрастом ~2.3-2.4 и 2.0-1.95 млрд лет характеризуются широким диапазоном eHf (от +9.8 до -3.3) и модельного возраста - T CHf = = 2.8-2.0 млрд лет. Питающая провинция для палеопротерозойских детритовых цирконов из парагнейсов включала как породы с ювенильными изотопными характеристиками, так и образованные в результате рециклинга архейской коры с варьирующей добавкой ювенильного материала. Цирконы с высокими положительными eHf формировались при эрозии пород, представляющих ювенильную кору палеопротерозойского возраста, тогда как снижение величин eHf и рост T CHf отражает вклад архейской коры в образование терригенного материала. Таким образом, на палеопротерозойском этапе эволюции юго-западной части Сибирского кратона происходили как процессы рециклинга, так и рост коры за счет поступления ювенильного материала. На юго-западе Сибирского кратона детритовые цирконы с возрастом ~2.3-2.4 и 1.95-2.0 млрд лет характерны для палеопротерозойских парагнейсов Иркутного и Ангаро-Канского блоков и терригенных пород Урикско-Ийского грабена, что свидетельствует в пользу их общих и, скорее всего, неудаленных источников сноса. По времени метаморфизма (1.88-1.85 млрд лет), возрасту палеопротерозойских детритовых цирконов (2.4-2.0 млрд лет) и их Lu-Hf изотопному составу (eHf от положительных до отрицательных значений) парагнейсы юго-запада Сибирского кратона близки к метаосадочным породам палеопротерозойских орогенических поясов Северо-Китайского кратона. Для обоих регионов в формировании источников детритовых цирконов участвовала как архейская кора, так и ювенильный материал, что дает свидетельства роста коры в интервале 2.4-2.0 млрд лет.

Чижова Ю.Н., Рец Е.П., Васильчук Ю.К. и др. Два подхода к расчёту расчленения гидрографа стока реки с ледниковым питанием с помощью изотопных методов// Лед и снег. 2016. Т. 56. № 2. С. 161-168.

Рассмотрено применение метода стабильных изотопов в балансовых расчётах расчленения гидрографа стока с ледника Джанкуат. Изученные изотопные вариации стока на замыкающем створе р. Джан- куат для двух сезонов абляции 2013 и 2014 г. совместно с измерениями 618О и минерализации различных источников питания р. Джанкуат (атмосферные осадки, снег разных сезонов, фирн, лёд и грунтовые воды) позволили расчленить гидрограф стока 2014 г. Применялись два методических подхода к расчётам: разделение гидрографа стока решением систем уравнений ионного и изотопного баланса с учётом изотопного фракционирования при таянии снега и без учёта фракционирования. Установлена величина погрешности расчётов с использованием значений 618О и абсолютных концентраций 18О.

Чугаев А.В., Чернышев И.В. и др. Изотопный состав свинца и происхождение четвертичных лав вулкана Эльбрус, Большой Кавказ: данные высокоточного метода MC-ICP-MS // Петрология. 2013. Т. 21. № 1. С. 20-33.

Проведено систематическое изучение вариаций изотопного состава Pb в четвертичных лавах одного из крупнейших вулканов Европы ? Эльбруса. Исследование было выполнено с помощью высокоточного анализа методом многоколлекторной масс-спектрометрии с индуктивно связанной плазмой (MC-ICP-MS). Погрешность измерения изотопных отношений Pb, оцененная по результатам параллельных анализов международных стандартных образцов горных пород BCR-1 и AGV-1, составила ±0.03 (±2SD). На основе изучения представительной коллекции образцов дацитов, характеризующих все три фазы магматической активности вулкана Эльбрус, установлен относительно небольшой масштаб вариаций изотопного состава Pb в его лавах: 206Pb/204Pb ? 18.621?18.670, 207Pb/204Pb ? 15.636?15.659 и 208Pb/204Pb ? 38.762?38.845. Полученные новые свинцово-изотопные геохимические характеристики в совокупности с ранее опубликованными для этих же пород Sr-Nd данными указывают на смешанное мантийно-коровое происхождение материнских магм Эльбруса, образовавшихся в результате взаимодействии глубинных расплавов с веществом континентальной коры Большого Кавказа в условиях континентальной коллизии Евразийской, Аравийской, Турецкой и Иранской плит.

Яковлев Е.Ю., Киселев Г.П., Дружинин С.В. Неравновесный уран в кимберлитах и вмещающих породах трубки Пионерская месторождения имени м.В. Ломоносова // Вестник Северного (Арктического) федерального университета. Серия: Естественные науки. 2016. № 1. С. 19-28.

Существующие в настоящее время проблемы в применении традиционных методов прогноза и поисков месторождений алмазов на территории Архангельской области, связанные со снижением контрастности выделяемых аномалий, обуславливают необходимость поиска других подходов к решению этих задач. Одним из таких направлений, активно развиваемых в последние годы, стало выявление в керне поисковых скважин признаков околорудных изменений вмещающих отложений, связанных с воздействием кимберлитов, таких как тектонические деформации, приконтактовые изменения пород, увеличение концентраций радиационных дефектов. Установлено, что в околотрубочном пространстве также обнаруживается увеличение интенсивности гамма-излучения пород, повышение концентрации ряда радиоактивных элементов, таких как уран-238, торий-232, калий-40, и возрастание величины отношения активностей четных изотопов урана, которое является трассером взаимодействия рудного вещества и вмещающих отложений. Возникла необходимость изучения особенностей фракционирования изотопов урана в твердой фазе приконтактовой области на примере ряда кимберлитовых трубок месторождения имени М.В. Ломоносова. Выполнено исследование изотопного состава урана в кимберлитах и вмещающих отложениях трубки Пионерская Золотицкого поля Архангельской алмазоносной провинции. Показано, что в кимберлитах диатремы, а также вмещающих отложениях, отдаленных от трубки, преимущественно сохраняется близкий к равновесному изотопный состав урана. В то же время в твердой фазе горных пород в приконтактовой зоне кимберлитов отмечается возрастание неравновесия альфа-активностей изотопной пары урана, что является следствием взаимодействия кимберлитового вещества и вмещающих отложений, приводящих к фракционированию четных изотопов урана

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