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Петрография и петрология магматических горных пород

Журнальные статьи

1. U10290
Allard P. et al. Degassing dynamics of basaltic lava lake at a top-ranking volatile emitter: Ambrym volcano, Vanuatu arc // Earth and Planetary Science Letters. 2016. Vol. 448. P. 69–80.

Persistent lava lakes are rare on Earth and provide volcanologists with a remarkable opportunity to directly investigate magma dynamics and degassing at the open air. Ambrym volcano, in Vanuatu, is one of the very few basaltic arc volcanoes displaying such an activity and voluminous gas emission, but whose study has long remained hampered by challenging accessibility. Here we report the first high temporal resolution (every 5 s) measurements of vigorous lava lake degassing inside its 300 m deep Benbow crater using OP-FTIR spectroscopy. Our results reveal a highly dynamic degassing pattern involving (i) recurrent (100–200 s) short-period oscillations of the volcanic gas composition and temperature, correlating with pulsated gas emission and sourced in the upper part of the lava lake, (ii) a continuous long period (?8 min) modulation probably due to the influx of fresh magma at the bottom of the lake, and (iii) discrete CO2 spike events occurring in coincidence with the sequential bursting of meter-sized bubbles, which indicates the separate ascent of large gas bubbles or slugs in a feeder conduit with estimated diameter of 6±1 m. This complex degassing pattern, measured with unprecedented detail and involving both coupled and decoupled magma-gas ascent over short time scales, markedly differs from that of quieter lava lakes at Erebus and Kilauea. It can be accounted for by a modest size of Benbow lava lake and its very high basalt supply rate (?20 m3?s?1), favouring its rapid overturn and renewal. We verify a typical basaltic arc signature for Ambrym volcanic gas and, based on contemporaneous SO2 flux measurements, we evaluate huge emission rates of 160 Gg?d?1 of H2O, ?10 Gg?d?1 of CO2 and ?8 Gg?d?1 of total acid gas (SO2, HCl and HF) during medium activity of the volcano in 2008. Such rates make Ambrym one of the three most powerful volcanic gas emitters at global scale, whose atmospheric impact at local and regional scale may be considerable.

http://dx.doi.org/10.1016%2Fj.epsl.2016.05.014

2. U10290
Black B.A., Manga M. Volatiles and the tempo of flood basalt magmatism // Earth and Planetary Science Letters. 2017. Vol. 458. P. 130–140.

Individual flood basalt lavas often exceed 103 km3 in volume, and many such lavas erupt during emplacement of flood basalt provinces. The large volume of individual flood basalt lavas implies correspondingly large magma reservoirs within or at the base of the crust. To erupt, some fraction of this magma must become buoyant and overpressure must be sufficient to encourage failure and dike propagation. The overpressure associated with a new injection of magma is inversely proportional to the total reservoir volume, and as a large magma body heats the surrounding rocks thermally activated creep will relax isotropic overpressure more rapidly. Here, we examine the viability of buoyancy overpressure as a trigger for continental flood basalt eruptions. We employ a new one-dimensional model that combines volatile exsolution, bubble growth and rise, assimilation, and permeable fluid escape from Moho-depth and crustal chambers. We investigate the temporal evolution of degassing and the eruptibility of magmas using the Siberian Traps flood basalts as a test case. We suggest that the volatile inventory set during mantle melting and redistributed via bubble motion controls ascent of magma into and through the crust, thereby regulating the tempo of flood basalt magmatism. Volatile-rich melts from low degrees of partial melting of the mantle are buoyant and erupt to the surface with little staging or crustal interaction. Melts with moderate volatile budgets accumulate in large, mostly molten magma chambers at the Moho or in the lower crust. These large magma bodies may remain buoyant and poised to erupt—triggered by volatile-rich recharge or external stresses—for ?106 yr. If and when such chambers fail, enormous volumes of magma can ascend into the upper crust, staging at shallow levels and initiating substantial assimilation that contributes to pulses of large-volume flood basalt eruption. Our model further predicts that the Siberian Traps may have released 1019–1020 g of CO2 during a number of brief (?104 yr) pulses, providing a plausible trigger for warming and ocean acidification during the end-Permian mass extinction. The assimilation of carbon-rich crustal rocks strongly enhances both flood basalt eruptibility and CO2 release, and the tempo of eruptions influences the environmental effects of CO2, SO2, and halogen degassing. The eruptive dynamics of flood basalts are thus inextricably linked with their environmental consequences.

http://dx.doi.org/10.1016%2Fj.epsl.2016.09.035

3. PDF
Brandstatter J. et al. The Origin of Carbonate Veins Within the Sedimentary Cover and Igneous Rocks of the Cocos Ridge: Results From IODP Hole U1414A // Geochemistry, Geophysics, Geosystems. 2018. Vol. 19, № 10. P. 3721–3738.

Carbonate veins in the igneous basement and in the lithified sedimentary cover of the Cocos Ridge at International Ocean Discovery Program (IODP) Hole 344-U1414A reveal the hydrologic system and fluid-rock interactions. IODP Hole 344-U1414A was drilled on the northern flank of the Cocos Ridge and is situated 1 km seaward from the Middle America Trench offshore Costa Rica. Isotopic and elemental compositions were analyzed to constrain the fluid source of the carbonate veins and to reveal the thermal history of Hole 344-U1414A. The formation temperatures (oxygen isotope thermometer) of the carbonate veins in the lithified sedimentary rocks range from 70 to 92 °C and in the basalt from 32 to 82 °C. 87Sr/86Sr ratios of the veins in the altered Cocos Ridge basalt range between 0.707307 and 0.708729. The higher ratios are similar to seawater strontium ratios in the Neogene. 87Sr/86Sr ratios lower 0.7084 indicate exchange of Sr with the igneous host rock. The calcite veins hosted by the sedimentary rocks are showing more primitive 87Sr/86Sr ratios <0.706396. The isotopic compositions indicate seawater, modified into a hydrothermal fluid by subsequent heating, as the main fluid source. Low-temperature alteration and the presence of a high-temperature fluid resulted in different carbonate precipitates forming up to several cm thick veins. The geochemical data combined with age data of the sedimentary rocks suggest intraplate seamount volcanism in the area between the Galapagos hot spot and the Cocos Island as an additional heating source, after the formation of the Cocos Ridge at the Galapagos hot spot.

http://dx.doi.org/10.1029%2F2018GC007729

4. U01624
Burgess K.D. et al. Submicrometer-scale spatial heterogeneity in silicate glasses using aberration-corrected scanning transmission electron microscopy // American Mineralogist. 2016. Vol. 101, № 12. P. 2677–2688.

Experimental silicate glasses are often used as analog and calibration material for terrestrial and planetary materials. Measurements of Fe oxidation state using electron energy loss spectroscopy (EELS) in an aberration-corrected scanning transmission electron microscope (ac-STEM) show that a suite of experimental silicate (e.g., basaltic, andesitic, rhyolitic) glasses have spatially heterogeneous oxidation states at scales of tens of nanometers. Nano-crystals are observed in several of the glasses, indicating nucleation and incipient crystallization not seen at the scale of electron microprobe analysis (EMPA). Glasses prepared in air are uniformly oxidized while glasses prepared at the iron-wustite (IW) or quartz-fayalite-magnetite (QFM) buffers range from reduced to highly oxidized. EELS spectral shapes indicate that oxidized glasses have tetrahedral Fe3+. The nanoscale compositional and structural heterogeneities present in the experimental glasses mean that the suitability of such glasses as analogs for natural materials and calibration standards depends strongly on the scale of the measurements being done. The electron beam quickly damages silicate glass, but data showing changes in oxidation state among and within samples can be obtained with careful control of the beam current and dwell time. Determination of oxidation state in silicate glasses via STEM-EELS is very challenging, and accurate and reliable measurements of Fe3+/?Fe require careful sample preparation and control of microscope conditions and benefit from comparison to complementary techniques.

http://dx.doi.org/10.2138%2Fam-2016-5696

5. U10290
Chen H. et al. Heterogeneous source components of intraplate basalts from NE China induced by the ongoing Pacific slab subduction // Earth and Planetary Science Letters. 2017. Vol. 459. P. 208–220.

The subduction of oceanic slabs is widely accepted to be a main reason for chemical heterogeneities in the mantle. However, determining the contributions of slabs in areas that have experienced multiple subduction events is often difficult due to possible overlapping imprints. Understanding the temporal and spatial variations of source components for widespread intraplate small volume basalts in eastern China may be a basis for investigating the influence of the subducted Pacific slab, which has long been postulated but never confirmed. For this purpose, we investigated the Chaihe-aershan volcanic field (including more than 35 small-volume Quaternary basaltic volcanoes) in NE China and measured the oxygen isotopes and water content of clinopyroxene (cpx) phenocrysts using secondary ion mass spectrometry (SIMS) and Fourier transform infrared spectroscopy (FTIR), respectively. The water content of magma was then estimated based on the partition coefficient of H2O between cpx and the basaltic melt. The ?18O of cpx phenocrysts (4.28‰ to 8.57‰) and H2O content of magmas (0.19 wt.%–2.70 wt.%) show large variations, reflecting the compositional heterogeneity of the mantle source. The ?18O values and H2O content within individual samples also display considerable variation, suggesting the mixing of magmas and that the magma mixing occurred shortly before the eruption. The relation between the ?18O values of cpx phenocrysts and the H2O/Ce ratio, Ba/Th ratio and Eu anomaly of whole rocks demonstrates the contributions of three components to the mantle source (hydrothermally altered upper oceanic crust and marine sediments, altered lower gabbroic oceanic crust, and ambient mantle). The proportions of these three components have varied widely over time (?1.37 Ma to ?0.25 Ma). The Pacific slab is constantly subducted under eastern Asia and continuously transports recycled materials to the deep mantle. The temporal heterogeneity of the source components may be caused by ongoing Pacific slab subduction. Combined with other basalt localities in eastern China (Shuangliao basalts, Taihang basalts and Shangdong basalts), the contributions of recycled oceanic components in their mantle source are heterogeneous. This spatial heterogeneity of mantle sources may be induced by variable alterations and dehydration during the recycling process of the Pacific slab. Our results show that the source components of Cenozoic intraplate small-volume basalts in eastern China are temporally and spatially heterogeneous, which is likely induced by the ongoing subduction of the Pacific slab. This demonstrates that integrating the temporal variations in geochemical characteristics and tectonic history of a study region can identify the subducted oceanic plate that induced enriched components in the mantle source of intraplate basalts.

http://dx.doi.org/10.1016%2Fj.epsl.2016.11.030

6. PDF
Coote A., Shane P. Open-system magmatic behaviour beneath monogenetic volcanoes revealed by the geochemistry, texture and thermobarometry of clinopyroxene, Kaikohe-Bay of Islands volcanic field (New Zealand) // Journal of Volcanology and Geothermal Research. 2018. Vol. 368. P. 51–62.

The ascent and temporary crustal storage of magmas beneath basaltic monogenetic volcanoes in continental settings is poorly understood, but is important in the study of their petrogenesis, and for monitoring future volcanic unrest. The Kaikohe-Bay of Islands volcanic field in northern New Zealand comprises Quaternary-aged monogenetic basalt volcanoes in an intraplate setting. Clinopyroxene phenocrysts in the basalts provide an opportunity to investigate the ascent history of the magmas that may not be evident from studies at the scale of whole-rock samples. The phenocrysts are texturally and compositionally diverse, and demonstrate the dominance of open system processes such as magma mixing and crystal entrainment in the crust. Many phenocrysts have an Mg (Mg# ~80–83) and Cr rich rim overgrowth which is in equilibrium with the host rock, but a resorbed, core (Mg# ~70) that crystallised from a more evolved magma. These crystals record mafic recharge, presumably the trigger to eruption. Other crystals are characterised by a high-Mg (Mg# ~82–84) and Cr core surrounded by a disequilibrium, low-Mg (Mg# 70–75) rim. The rims are reversely zoned and demonstrate late-stage equilibrium with the host rock. These crystals either nucleated in the host magma or were entrained from earlier basaltic intrusions of similar composition. The rim zones record re-melting of intrusions, or interaction with more differentiated magmas, followed by mafic recharge. Subordinate crystal types include oscillatory zoned crystals (Mg# >80) that nucleated in the ascending magma, and diffusely, patchy-zoned crystals that are variously antecrystic or xenocrystic in origin. Cognate gabbro inclusions contain clinopyroxene in equilibrium with the host basalt, suggesting they originated from side-wall crystallisation. Crystal-melt equilibria indicate that the cognate clinopyroxene formed at 430?±?170?MPa (2?) (=16?±?6?km depth), and a subordinate population formed at 730?±?160?MPa (=28?±?6?km depth). These depths coincide with major seismic velocity contrasts at a zone of partial melt (10–19?km) and the Moho (~28?km). Thus, buoyancy or rheology contrasts in the crust temporarily slowed magma ascent and promoted periods of crystallisation and the assimilation of antecrystic and xenocrystic components. Similar magmatic processes occurred at the neighbouring and contemporaneous Whangarei volcanic field. Both of these fields have been active for millions of years, and longevity could explain the formation of differentiated crustal instrusives. In systems where magmas temporarily stall, there is a greater likelihood of detecting pre-eruption geophysical phenomena that could act as signals to pending eruptions.

http://dx.doi.org/10.1016%2Fj.jvolgeores.2018.11.006

7. PDF
Cucciniello C. et al. The age and petrogenesis of alkaline magmatism in the Ampasindava Peninsula and Nosy Be archipelago, northern Madagascar // Miner Petrol. 2016. Vol. 110, № 2. P. 309–331.

The Ampasindava alkaline province consists of a series of circular and elliptical intrusions, lava flows, dyke swarms and plugs of Cenozoic age emplaced into the Mesozoic-Cenozoic sedimentary rocks of the Antsiranana basin (NW Madagascar) and above the crystalline basement. The magmatism in the Ampasindava region is linked to a NW-SE trending extensional tectonic setting. New 40Ar/39Ar age determinations on feldspar separate of alkali granites and basaltic dykes yielded ages of 18.01 ± 0.36 Ma and 26 ± 7 Ma, respectively. Alkali basalts and basanites, nepheline syenites and phonolites, and silica saturated-to-oversaturated syenites, trachytes, granites and rhyolites are the main outcropping lithologies. These rocks have sodic affinity. The felsic rocks are dominant, and range from peraluminous to peralkaline. The mantle-normalized incompatible element patterns of the mafic lavas match those of Na-alkaline lavas in within-plate rift settings. The patterns are identical in shape and absolute concentrations to those of the Bobaomby (Cap d’Ambre) and Massif d’Ambre primitive volcanic rocks. These geochemical features are broadly compatible with variable degrees of partial melting of incompatible element-enriched mantle sources. The mineralogical and geochemical variations are consistent with fractional crystallization processes involving removal of olivine, feldspar, clinopyroxene, amphibole, Fe-Ti oxides and apatite. Removal of small amount of titanite explains the concave upward lanthanide pattern in the evolved nepheline syenites and phonolites, which are additionally rich in exotic silicates typical of agpaitic magmas (eudialyte, F-disilicates).

http://dx.doi.org/10.1007%2Fs00710-015-0387-1

8. U10290
Dalou C. et al. Nitrogen and carbon fractionation during core–mantle differentiation at shallow depth // Earth and Planetary Science Letters. 2017. Vol. 458. P. 141–151.

One of the most remarkable observations regarding volatile elements in the solar system is the depletion of N in the bulk silicate Earth (BSE) relative to chondrites, leading to a particularly high and non-chondritic C:N ratio. The N depletion may reflect large-scale differentiation events such as sequestration in Earth's core or massive blow off of Earth's early atmosphere, or alternatively the characteristics of a late-added volatile-rich veneer. As the behavior of N during early planetary differentiation processes is poorly constrained, we determined together the partitioning of N and C between Fe–N–C metal alloy and two different silicate melts (a terrestrial and a martian basalt). Conditions spanned a range of fO2 from ?IW?0.4 to ?IW?3.5 at 1.2 to 3 GPa, and 1400?°C or 1600?°C, where ?IW is the logarithmic difference between experimental fO2 and that imposed by the coexistence of crystalline Fe and wustite. N partitioning (DNmetal/silicate) depends chiefly on fO2, decreasing from 24±3 to 0.3±0.1 with decreasing fO2. DNmetal/silicate also decreases with increasing temperature and pressure at similar fO2, though the effect is subordinate. In contrast, C partition coefficients (DCmetal/silicate) show no evidence of a pressure dependence but diminish with temperature. At 1400?°C, DCmetal/silicate partition coefficients increase linearly with decreasing fO2 from 300±30 to 670±50. At 1600?°C, however, they increase from ?IW?0.7 to ?IW?2 (87±3 to 240±50) and decrease from ?IW?2 to ?IW?3.3 (99±6). Enhanced C in melts at high temperatures under reduced conditions may reflect stabilization of C–H species (most likely CH4). No significant compositional dependence for either N or C partitioning is evident, perhaps owing to the comparatively similar basalts investigated. At modestly reduced conditions (?IW?0.4 to ?2.2), N is more compatible in core-forming metal than in molten silicate (1?DNmetal/silicate?24), while at more reduced conditions (?IW?2.2 to ?IW?3.5), N becomes more compatible in the magma ocean than in the metal phase. In contrast, C is highly siderophile at all conditions investigated (100?DCmetal/silicate?700). Therefore, sequestration of volatiles in the core affects C more than N, and lowers the C:N ratio of the BSE. Consequently, the N depletion and the high C:N ratio of the BSE cannot be explained by core formation. Mass balance modeling suggests that core formation combined with atmosphere blow-off also cannot produce a non-metallic Earth with a C:N ratio similar to the BSE, but that the accretion of a C-rich late veneer can account for the observed high BSE C:N ratio.

http://dx.doi.org/10.1016%2Fj.epsl.2016.10.026

9. U10290
Ding S., Dasgupta R. The fate of sulfide during decompression melting of peridotite – implications for sulfur inventory of the MORB-source depleted upper mantle // Earth and Planetary Science Letters. 2017. Vol. 459. P. 183–195.

Magmatism at mid ocean ridges is one of the main pathways of S outflux from deep Earth to the surface reservoirs and is a critical step in the global sulfur cycle, yet our understanding of the behavior of sulfide during decompression melting of the upper mantle is incomplete. In order to constrain the sulfur budget of the mantle and reconcile the sulfur and chalcophile element budget of mantle partial melts parental to primitive mid-ocean ridge basalts (MORBs), here we developed a model to describe the behavior of sulfide and Cu during decompression melting by combining the pMELTS thermodynamic model and empirical sulfur contents at sulfide concentration (SCSS) models, taking into account the effect of the presence of Ni and Cu in sulfides on SCSS of mantle-derived melts. Calculation of SCSS along melting adiabat at mantle potential temperature of 1380?°C with variable initial S content in the mantle indicates that the complete consumption or partial survival of sulfide in the melting residue depends on initial S content and degree of melting. Primitive MORBs (Mg#>60) with S and Cu mostly concentrated in 800–1000 ppm and 80–120 ppm are likely mixture of sulfide undersaturated high degree melts and sulfide saturated low degree melts derived from depleted peridotite containing 100–200 ppm S. Model calculations to capture the effects of variable mantle potential temperatures (1280–1420?°C) indicate that for a given abundance of sulfide in the mantle, hotter mantle consumes sulfide more efficiently than colder mantle owing to the effect of temperature in enhancing sulfide solubility in silicate melt, and higher mantle temperature stabilizing partial melt with higher FeO? and lower SiO2 and Al2O3, all of which generally enhance sulfide solubility. However, sulfide can still be exhausted by ?10–15% melting with bulk S of 100–150 ppm in the mantle when TP is as low as 1300?°C. We also show that although variation of DCuperidotite/melt and initial Cu in the mantle can all affect the Cu concentration of primitive MORBs, 100–200 ppm S in the MORB source mantle can satisfy both S and Cu geochemistry of partial melts parental to ocean floor basalts.

http://dx.doi.org/10.1016%2Fj.epsl.2016.11.020

10. PDF
Dostal J., MacRae A. Cretaceous basalts of the High Arctic large igneous province at Axel Heiberg Island (Canada): Volcanic stratigraphy, geodynamic setting, and origin // Geological Journal. 2018. Vol. 53, № 6. P. 2918–2934.

The Cretaceous (Cenomanian, 96 Ma) basaltic rocks of the Strand Fiord Formation of the Sverdrup Basin of the Canadian Arctic Archipelago, Nunavut, Canada, are a part of the High Arctic large igneous province. The basaltic suite reaches a thickness of almost 1,000 m on Axel Heiberg Island in its depocentre and over 700 m at the studied section. The rocks are variably fractionated tholeiitic basalts, which are geochemically similar to many other continental flood basalts, particularly to low Ti basalts of flood basalt provinces. Geochemical as well as Sr (87Sr/86Srinitial 0.7045 to 0.7067) and Nd (?Nd(t) +1.3 to +4.3) isotopic signatures of the basalts were inherited during partial melting of spinel peridotite of an ancient subcontinental lithospheric mantle, which was modified around 0.7–0.9 Ga by a metasomatic event. The melting generating the Cretaceous basalts was probably triggered by a mantle plume but was also associated with basin rifting and stretching. There is evidence of plume-induced doming and uplift of the crust prior to and during the eruption of the basalts as documented by the progression from marine sedimentation to subaerial/lacustrine and then back to marine sedimentation in the Sverdrup Basin centre. The basalts represent parts of the Early Cretaceous igneous province that is dispersed around the Arctic Ocean due to the opening of the Canada Basin, which is inferred to be related to a mantle plume.

http://dx.doi.org/10.1002%2Fgj.3132

11. PDF
Essaifi A., Zayane R. Petrogenesis and origin of the Upper Jurassic-Lower Cretaceous magmatism in Central High Atlas (Morocco): Major, trace element and isotopic (Sr-Nd) constraints // Journal of African Earth Sciences. 2018. Vol. 137. P. 229–245.

During an uplift phase, which lasted ca. 40 Ma, from the Late Jurassic (165 Ma) to the Early Cretaceous (125 Ma), transitional to moderately alkaline magmatic series were emplaced in the Central High Atlas. The corresponding magmatic products include basaltic lava flows erupted within wide synclines and intrusive complexes composed of layered mafic intrusions and monzonitic to syenitic dykes emplaced along narrow anticlinal ridges. The igneous rock sequence within the intrusive complexes is composed of troctolites, olivine-gabbros, oxide-gabbros, monzonites and syenites. The chemical compositions of the various intrusive rocks can be accounted for by crystal accumulation, fractional crystallization and post-magmatic remobilization. The evolution from the troctolites to the syenites was mainly controlled by a fractional crystallization process marked by early fractionation of olivine, plagioclase and clinopyroxene, followed by separation of biotite, amphibole, apatite, and Ti-magnetite. Hydrothermal activity associated with emplacement of the intrusions within the Jurassic limestones modified the elemental and the Sr isotopic composition of the hydrothermally altered rocks In particular the monzonitic to syenitic dykes underwent an alkali metasomatism marked by depletion in K and Rb and enrichment in Na and Sr. As a result, their Sr isotopic composition was shifted towards higher initial Sr isotopic ratios (0.7067–0.7075) with respect to the associated gabbros (0.7036–0.7046). On the contrary, the Nd isotopic compositions were preserved from isotope exchange with the limestones and vary in a similar range to those of the gabbros (+1.6 < ?Ndi < +4.1). The isotopic and the trace element ratios of the uncontaminated samples were used to constrain the source characteristics of this magmatism. The Sr-Nd isotopic data and the incompatible element ratios (e.g. La/Nb, Zr/Nb, Th/U, Ce/Pb) are consistent with generation from an enriched upper mantle similar to an ocean island basalt source. Melting of the subcontinental metasomatized lithosphere is tentatively related to small-scale shallow mantle upwelling and asthenospheric uprise at the triple junction between the western High Atlas, the Middle Atlas and the eastern High Atlas domains during a period of relative tectonic quiescence.

http://dx.doi.org/10.1016%2Fj.jafrearsci.2017.10.002

12. U01624
Gall N.L., Pichavant M. Experimental simulation of bubble nucleation and magma ascent in basaltic systems: Implications for Stromboli volcano // American Mineralogist. 2016. Vol. 101, № 9. P. 1967–1985.

The ascent of H2O- and H2O-CO2-bearing basaltic melts from the deeper to the shallower part of the Stromboli magmatic system and their vesiculation were simulated from decompression experiments. A well-studied “golden” pumice produced during an intermediate- to a large-scale paroxysm was used as starting material. Volatile-bearing glasses were synthesized at an oxygen fugacity (fO2) ranging from NNO?1.4 to +0.9, 1200 °C and 200 MPa. The resulting crystal- and bubble-free glasses were then isothermally (1200 °C) decompressed to final pressures Pf ranging between 200 and 25 MPa, at a linear ascent rate of 1.5 m/s (or 39 kPa/s) prior to be rapidly quenched. Textures of post-decompression glasses that were characterized by X-ray computed tomography result from different mechanisms of degassing that include bubble nucleation, growth, coalescence, and outgassing, as well as fragmentation. Homogeneous bubble nucleation occurs for supersaturation pressures (difference between saturation pressure and pressure at which bubbles start to form homogeneously, ?PHoN) ? 50 MPa. In the CO2-free melts, homogeneous nucleation occurs as two distinct events, the first at high Pf (200–150 MPa) and the second at low Pf (50–25 MPa) near the fragmentation level. In contrast, in the CO2-bearing melts, multiple events of homogeneous bubble nucleation occur over a substantial Pf interval along the decompression path. Bubble coalescence occurs in both H2O- and H2O-CO2-bearing melts and is the more strongly marked between 100 and 50 MPa Pf. The CO2-free melts follow equilibrium degassing until 100 MPa Pf and are slightly supersaturated at 60 and 50 MPa Pf, thus providing the driving force for the second bubble nucleation event. In comparison, disequilibrium degassing occurs systematically in the CO2-bearing melts that retain high CO2 concentrations. Fragmentation was observed in some CO2-free charges decompressed to 25 MPa Pf and is intimately associated with the occurrence of the second bubble nucleation event. Textures of H2O-CO2-bearing glasses reproduce certain critical aspects of the Stromboli natural textures (bubble number densities, shapes, sizes, and distributions) and chemistries (residual volatile concentrations). Average bubble sizes, bubble size distribution (BSD), and bubble number density (BND) data are used together to estimate that the “golden” pumice magmas ascend from their source region in 43 to 128 min.

http://dx.doi.org/10.2138%2Fam-2016-5639

13. U10290
Gao R., Lassiter J.C., Ramirez G. Origin of temporal compositional trends in monogenetic vent eruptions: Insights from the crystal cargo in the Papoose Canyon sequence, Big Pine Volcanic Field, CA // Earth and Planetary Science Letters. 2017. Vol. 457. P. 227–237.

Many monogenetic vents display systematic temporal–compositional variations over the course of eruption. Previous studies have proposed that these trends may reflect variable degrees of crustal assimilation, or melting and mixing of heterogeneous mantle source(s). Discrimination between these two endmember hypotheses is critical for understanding the plumbing systems of monogenetic volcanoes, which pose a significant volcanic hazard in many areas. In this study, we examine the Papoose Canyon (PC) monogenetic vent in the Big Pine Volcanic Field (BPVF), which had been well characterized for temporal–compositional variations in erupted basalts. We present new major and trace element and Sr–Nd–Pb-O isotopic data from the PC “crystal cargo” (phenocrysts and xenoliths). Comparison of “crystal cargo” and host basalt provides new constraints on the history of magma storage, fractionation, and crustal contamination that are obscured in the bulk basalts due to pre- and syn-eruptive magma mixing processes. The abundances of phenocrysts and ultramafic xenoliths in the PC sequence decrease up-section. Olivine and clinopyroxene phenocrysts span a wide range of Mg# (77–89). The majority of phenocrysts are more evolved than olivine or clinopyroxene in equilibrium with their host basalts (Mg#=68–71, equilibrium Fo?85–89). In addition, the ultramafic xenoliths display cumulate textures. Olivine and clinopyroxene from ultramafic xenoliths have Mg# (73–87) similar to the phenocrysts, and lower than typical mantle peridotites. Sr–Nd–Pb isotope compositions of the xenoliths are similar to early PC basalts. Finally, many clinopyroxene phenocrysts and clinopyroxene in xenoliths have trace element abundances in equilibrium with melts that are more enriched than the erupted basalts. These features suggest that the phenocrysts and xenoliths derive from melt that is more fractionated and enriched than erupted PC basalts. Pressure constraints suggest phenocrysts and ultramafic xenoliths crystallized at ?5–7 kbar, corresponding to mid-crust depths. Correlations between HFSE depletion and Sr–Nd–Pb isotopic compositions, high ?18O values in olivines, and radiogenic Os isotopic compositions in whole rocks also suggest incorporation of a crustally contaminated component. We propose that the phenocrysts and ultramafic xenoliths derive from melts that ponded and fractionated and assimilated continental crust, possibly in mid-crustal sills. These melts were drained and mixed with more primitive melts as the eruption began, and the temporal–compositional trends and decreasing crystal phase abundances reflect gradual deflation and exhaustion of these sills as the eruption progressed. The isotopic variations in the PC sequence span much of the compositional range observed in the BPVF. Evidence for variable crustal contamination of PC basalts suggests that much of the isotopic variation observed in the BPVF may also reflect crustal contamination rather than mantle source heterogeneity as previously proposed. In addition, evidence of pre-eruptive magma ponding and fractionation, if applicable to other monogenetic vents, may have significant implications for monitoring and hazard assessment of monogenetic volcano fields.

http://dx.doi.org/10.1016%2Fj.epsl.2016.10.013

14. U10290
Gibson S.A. et al. The influence of melt flux and crustal processing on Re–Os isotope systematics of ocean island basalts: Constraints from Galapagos // Earth and Planetary Science Letters. 2016. Vol. 449. P. 345–359.

New rhenium–osmium data for high-MgO (>9 wt.%) basalts from the Galapagos Archipelago reveal a large variation in 187Os/188Os (0.1304 to 0.173), comparable with the range shown by primitive global ocean island basalts (OIBs). Basalts with the least radiogenic 187Os/188Os occur closest to the Galapagos plume stem: those in western Galapagos have low 187Os/188Os, moderate 87Sr/86Sr, 143Nd/144Nd, 206Pb/204Pb and high 3He/4He whereas basalts in the south also have low 187Os/188Os but more radiogenic 87Sr/86Sr, 143Nd/144Nd, 206Pb/204Pb and 3He/4He. Our new Os isotope data are consistent with the previously established spatial zonation of the common global isotopic mantle reservoir “C” and ancient recycled oceanic crust in the mantle plume beneath western and southern parts of Galapagos, respectively. Galapagos basalts with the most radiogenic 187Os/188Os (up to 0.1875) typically have moderate MgO (7–9 wt.%) and low Os (<50 pg?g?1) but have contrastingly unenriched Sr, Nd and Pb isotope signatures. We interpret this decoupling of chalcophile and lithophile isotopic systems as due to assimilation of young Pacific lower crust during crystal fractionation. Mixing models show the assimilated crust must have higher contents of Re and Os, and more radiogenic 187Os/188Os (0.32), than previously proposed for oceanic gabbros. We suggest the inferred, exceptionally-high radiogenic 187Os of the Pacific crust may be localised and due to sulfides precipitated from hydrothermal systems established at the Galapagos Spreading Centre. High 187Os/188Os Galapagos basalts are found where plume material is being dispersed laterally away from the plume stem to the adjacent spreading centre (i.e. in central and NE parts of the archipelago). The extent to which crustal processing influences 187Os/188Os appears to be primarily controlled by melt flux: as distance from the stem of the Galapagos plume increases, the melt flux decreases and crustal assimilation becomes proportionally greater, accounting for co-variations in Os and 187Os/188Os. The Os concentration threshold below which the 187Os/188Os of Galapagos basalts are contaminated (100 pg?g?1) is higher than the canonical value (<50 pg?g?1) assumed for many other global OIBs (e.g. for Iceland, Grande Comore and Hawaii). This most likely reflects the low overall melt flux to the crust from the Galapagos plume, which has only a moderate excess temperature and buoyancy flux. Our findings have implications for the interpretation of 187Os/188Os ratios in other ocean island settings, especially those where large variations in 187Os/188Os have been linked to heterogeneity in mantle lithology or sulfide populations: the effect of crustal contamination on 187Os/188Os may be greater than previously recognised, particularly for basalts associated with weak, low melt flux mantle plumes, such as Tristan, Bouvet, Crozet and St Helena.

http://dx.doi.org/10.1016%2Fj.epsl.2016.05.021

15. U10290
Glaze L.S. et al. Assessing eruption column height in ancient flood basalt eruptions // Earth and Planetary Science Letters. 2017. Vol. 457. P. 263–270.

A buoyant plume model is used to explore the ability of flood basalt eruptions to inject climate-relevant gases into the stratosphere. An example from the 1986 Izu-Oshima basaltic fissure eruption validates the model's ability to reproduce the observed maximum plume heights of 12–16 km above sea level, sustained above fire-fountains. The model predicts maximum plume heights of 13–17 km for source widths of between 4–16 m when 32% (by mass) of the erupted magma is fragmented and involved in the buoyant plume (effective volatile content of 6 wt%). Assuming that the Miocene-age Roza eruption (part of the Columbia River Basalt Group) sustained fire-fountains of similar height to Izu-Oshima (1.6 km above the vent), we show that the Roza eruption could have sustained buoyant ash and gas plumes that extended into the stratosphere at ?45°N. Assuming 5 km long active fissure segments and 9000 Mt of SO2 released during explosive phases over a 10–15 year duration, the ?180km of known Roza fissure length could have supported ?36 explosive events/phases, each with a duration of 3–4 days. Each 5 km fissure segment could have emitted 62 Mt of SO2 per day into the stratosphere while actively fountaining, the equivalent of about three 1991 Mount Pinatubo eruptions per day. Each fissure segment could have had one to several vents, which subsequently produced lava without significant fountaining for a longer period within the decades-long eruption. Sensitivity of plume rise height to ancient atmospheric conditions is explored. Although eruptions in the Deccan Traps (?66Ma) may have generated buoyant plumes that rose to altitudes in excess of 18 km, they may not have reached the stratosphere because the tropopause was substantially higher in the late Cretaceous. Our results indicate that some flood basalt eruptions, such as Roza, were capable of repeatedly injecting large masses of SO2 into the stratosphere. Thus sustained flood basalt eruptions could have influenced climate on time scales of decades to centuries but the location (i.e., latitude) of the province and relevant paleoclimate is important and must be considered.

http://dx.doi.org/10.1016%2Fj.epsl.2014.07.043

16. PDF
Heath M., Phillips D., Matchan E.L. An evidence-based approach to accurate interpretation of 40Ar/39Ar ages from basaltic rocks // Earth and Planetary Science Letters. 2018. Vol. 498. P. 65–76.

Since its inception in the mid-1960s, the 40Ar/39Ar dating technique has been the premier method for determining the eruption ages of basaltic rocks, providing valuable insights into a plethora of terrestrial and planetary processes. Advances in multi-collector mass spectrometry and improved sample preparation procedures are enabling ever-improving analytical precision and clearer evaluation of the isotopic disturbances that affect many basaltic samples and cause discordant 40Ar/39Ar age spectra. Here, we present 40Ar/39Ar step-heating data for multiple samples from two Quaternary basalt flows (0.8038 ± 0.0017 and 2.309 ± 0.009 Ma) of the intraplate Newer Volcanic Province, southeast Australia. A small proportion of these samples give concordant 40Ar/39Ar results, but most are variably discordant. The factors controlling these disturbances and implications for accurate age determination are examined and modelled in both step-heating spectra and inverse isochron space. We demonstrate that the proportion of radiogenic 40Ar (40Ar?) present in these samples strongly influences the nature of the discordance reflected in 40Ar/39Ar data. Mass-dependent fractionation appears to have a major influence on low-40Ar? samples, whereas 39Ar recoil loss/redistribution effects are evident in samples with higher 40Ar? proportions. The impact of mass fractionation is quantified via step-heating analyses of unirradiated basalt, whereby a ?4% difference in 38Ar/36Ar ratios is observed between low- and high-temperature heating steps. On an inverse isochron plot (39Ar/40Ar vs 36Ar/40Ar), isotopic disturbance for groundmass samples primarily manifests as isochron rotation, leading to a negative correlation between initial 40Ar/36Ar ([40Ar/36Ar]i) values and associated 40Ar/39Ar ages. We propose a new framework for the interpretation of 40Ar/39Ar step-heating data for basaltic samples, through judicious evaluation of inverse isochron data, (40Ar/36Ar)i ratios and inverse isochron ages. Results from this study suggest that only samples exhibiting both flat 40Ar/39Ar age spectra and atmospheric (40Ar/36Ar)i ratios yield accurate eruption ages; in the case of more discordant age spectra, intermediate temperature steps with atmospheric (40Ar/36Ar)i ratios may provide the closest approximation of the eruption age.

http://dx.doi.org/10.1016%2Fj.epsl.2018.06.024

17. 045054
I Международный базальтовый форум: оценка реалий и возможностей базальтовой индустрии // Рациональное освоение недр. 2016. № 5–6. С. 117–119.

Впервые организованный и проведенный в Москве базальтовый форум стал уникальной площадкой для обсуждения перспектив развития базальтовой индустрии, производства базальтового волокна и композитных материалов на его основе.

https://elibrary.ru/item.asp?id=32235465

18. U59752
Jenner F.E., Arevalo R.D. Major and Trace Element Analysis of Natural and Experimental Igneous Systems using LA–ICP–MS // Elements. 2016. Vol. 12, № 5. P. 311–316.

Laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) enables spatially resolved quantitative measurements of major, minor and trace element abundances in igneous rocks and minerals with equal or better precision than many other in situ techniques, and more rapidly than labour-intensive wet chemistry procedures. Common applications for LA–ICP–MS in the Earth sciences centre on investigating the composition of natural and experimental geological materials, including: analysis of whole rock silicate glasses, flux-free pressed powder tablets and/or fused aliquots of materials; in situ probing of individual minerals, xenocrysts, fluid and melt inclusions, experimental run products, and siderophile-rich micronuggets; and multidimensional chemical mapping of complex (multiphase) materials.

https://doi.org/10.2113/gselements.12.5.311

19. PDF
Kuwahara H. et al. Simultaneous determination of melting phase relations of mantle peridotite and mid-ocean ridge basalt at the uppermost lower mantle conditions // Physics of the Earth and Planetary Interiors. 2018. Vol. 284. P. 36–50.

Interpretation of melting phase relationships of mantle peridotite and subducted basaltic crust is important for understanding chemical heterogeneity in the Earth’s interior. Although numerous studies have conducted melting experiments on peridotite and mid-ocean ridge basalt (MORB), and suggested that the solidus temperature of MORB is lower than that of peridotite at whole mantle pressure conditions, both solidus temperatures overlap within their uncertainties. In this study, we conducted simultaneous experiments on KLB-1 peridotite and normal MORB (N-MORB) at pressures from 25?GPa to 27?GPa and temperatures from 2398?K to 2673?K, to compare the solidus temperatures and their melting phase relations. The experimental results show that the solidus temperature of the N-MORB is nearly identical to the KLB-1 peridotite at 25?GPa but lower at 27?GPa. In addition, we found that the crossover of melt fractions between KLB-1 peridotite and N-MORB occurs at 25–27?GPa. These changes are likely to be attributed to the majorite-bridgmanite transition of MORB. This indicates that the dominant melting component may change depending on the location of the uppermost lower mantle. Our calculation result on the density of partial melts along the mantle geotherm suggests that partial melts of KLB-1 peridotite are gravitationally stable around the top of the transition zone, whereas partial melts of N-MORB are gravitationally stable even at the top of lower mantle. These results suggest that the distribution of partial melts may be different between KLB-1 peridotite and N-MORB in the deep Earth. Our results may be useful for understanding the fate of partial melts of peridotitic mantle and recycled basaltic crust.

http://dx.doi.org/10.1016%2Fj.pepi.2018.08.012

20. PDF
Li Y. et al. Early–Middle Ordovician volcanism along the eastern margin of the Xing’an Massif, Northeast China: constraints on the suture location between the Xing’an and Songnen–Zhangguangcai Range massifs // International Geology Review. 2018. Vol. 60, № 16. P. 2046–2062.

We present new zircon U–Pb and Hf isotopic as well as whole-rock geochemical data for volcanic rocks from the eastern margin of the Xing’an Massif, Northeast China, in order to further our understanding of the suture location between the Xing’an and Songnen–Zhangguangcai Range massifs. Zircon secondary ion mass spectrometry U–Pb dating indicates that the volcanic rocks formed during the Early–Middle Ordovician (473–463 Ma). Compared with the coeval Moguqi basalts (rare earth element [REE] = 171–183 ppm; ?Hf(t) = +0.3 to +2.7; TDM1 = 1074–977 Ma), the Duobaoshan andesites exhibit lower overall REE abundances (109–131 ppm) with relatively high heavy REE contents, stronger high-field-strength element depletion, higher ?Hf(t) values (+13.0 to +14.8), and much younger TDM1 ages (559–484 Ma). This suggests that the primary magma for the andesites was generated by the partial melting of a relatively depleted mantle wedge that was metasomatized by subduction-related fluids. The primary magma for the basalts in the Moguqi area was probably derived from the partial melting of a relatively enriched lithospheric mantle that was also modified by fluids sourced from a subducted slab. These interpretations suggest that the andesites in Duobaoshan formed in a newly accreted island arc setting, whereas the coeval basalts in Moguqi formed along an active continental margin. We therefore attribute the Early–Middle Ordovician volcanism along the eastern margin of the Xing’an Massif to the northwestward subduction of the Nenjiang–Heihe oceanic plate beneath the Xing’an Massif. Furthermore, considering coeval igneous activity in the southern parts of the Xing’an Massif, we suggest that a magmatic arc existed along the margin of the Xing’an Massif in the early Palaeozoic (490–420 Ma). We conclude that the location of the suture between the Xing’an and Songnen–Zhangguangcai Range massifs runs from Airgin Sum, via south of Xilinhot, to Ulanhot, Moguqi, Nenjiang, and finally Heihe.

http://dx.doi.org/10.1080%2F00206814.2017.1402378

21. U10290
Millet M.-A. et al. Titanium stable isotope investigation of magmatic processes on the Earth and Moon // Earth and Planetary Science Letters. 2016. Vol. 449. P. 197–205.

We present titanium stable isotope measurements of terrestrial magmatic samples and lunar mare basalts with the aims of constraining the composition of the lunar and terrestrial mantles and evaluating the potential of Ti stable isotopes for understanding magmatic processes. Relative to the OL–Ti isotope standard, the ?49Ti values of terrestrial samples vary from ?0.05 to +0.55‰, whereas those of lunar mare basalts vary from ?0.01 to +0.03‰ (the precisions of the double spike Ti isotope measurements are ca. ±0.02‰ at 95% confidence). The Ti stable isotope compositions of differentiated terrestrial magmas define a well-defined positive correlation with SiO2 content, which appears to result from the fractional crystallisation of Ti-bearing oxides with an inferred isotope fractionation factor of ?Tioxide–melt49=?0.23‰?106/T2. Primitive terrestrial basalts show no resolvable Ti isotope variations and display similar values to mantle-derived samples (peridotite and serpentinites), indicating that partial melting does not fractionate Ti stable isotopes and that the Earth's mantle has a homogeneous ?49Ti composition of +0.005 ± 0.005 (95% c.i., n=29). Eclogites also display similar Ti stable isotope compositions, suggesting that Ti is immobile during dehydration of subducted oceanic lithosphere. Lunar basalts have variable ?49Ti values; low-Ti mare basalts have ?49Ti values similar to that of the bulk silicate Earth (BSE) while high-Ti lunar basalts display small enrichment in the heavy Ti isotopes. This is best interpreted in terms of source heterogeneity resulting from Ti stable isotope fractionation associated with ilmenite–melt equilibrium during the generation of the mantle source of high-Ti lunar mare basalts. The similarity in ?49Ti between terrestrial samples and low-Ti lunar basalts provides strong evidence that the Earth and Moon have identical stable Ti isotope compositions.

http://dx.doi.org/10.1016%2Fj.epsl.2016.05.039

22. PDF
Mitsunobu S. et al. ?XAFS and TEM studies of Fe(III) oxides precipitated on submarine basaltic glass from South Pacific Gyre // Chemical Geology. 2018. Vol. 501. P. 51–57.

In the present study, we investigated secondary products formed on the surface of altered basaltic glass from the sediment-basalt interface by multiple characterizations with EPMA, ?XANES, ?EXAFS, TEM, and EELS. ?XANES and EPMA analyses showed that secondary products with high Fe abundance were precipitated on the surface of basalt glass and that the Fe species in the secondary product was dominantly composed of Fe(III) oxides, hematite, which was also agreeable with EELS result. Characterization by TEM and ?EXAFS suggested that the hematite was nanoparticulate with particle size of 10–20?nm. This is the first study showing the occurrence of nanosized hematite as secondary products in altered basaltic glass, although there are many studies on the formation of Fe(III) (hydr)oxides in basalt alteration.

http://dx.doi.org/10.1016%2Fj.chemgeo.2018.10.005

23. PDF
Mordensky S.P., Wallace P.J. Magma storage below Cascades shield volcanoes as inferred from melt inclusion data: A comparison of long-lived and short-lived magma plumbing systems // Journal of Volcanology and Geothermal Research. 2018. Vol. 368. P. 1–12.

In the central Oregon Cascades, mafic volcanic edifices include both short-lived cinder cones and a spectrum of much larger, longer-lived volcanoes. We analyzed olivine-hosted melt inclusions from explosive eruptions from three of the larger edifices to compare crystallization, volatile contents, and storage depths to those of the shorter-lived cinder cones. The melt inclusions were sampled from calc-alkaline basalt to basaltic andesite tephra collected from Belknap, Mount Washington, and North Sister volcanoes. Olivine host compositions are Fo80–83, Fo79–82, and Fo74–81, respectively. These Fo values are lower than the published values for nearby cinder cones (mostly Fo83–85), indicating greater extents of differentiation beneath the longer-lived edifices. The H2O contents of melt inclusions from each of the three volcanoes form a continuous range of values from ?0.5 to ~2.5?wt% H2O. Many of the inclusions contain a vapor bubble, and the bubbles are mostly in the range of 1.0–6?vol% of the inclusion. After correcting bubble-bearing inclusions for the amounts of CO2 lost to the bubbles, our data show that variable degassing and olivine crystallization occurred beneath the larger edifices over a wide range of depths from >?7?km (>?2–5?kbar) to as shallow as ~0.1?km (~10–30 bars). In contrast, olivine-hosted melt inclusions from nearby cinder cones record entrapment at >?4–5?km depth, with no evidence for shallow crystallization and storage (e.g. Ruscitto et al., 2010). Our results demonstrate that the longer-lived edifices develop a vertically extensive zone of storage and crystallization that extends from the middle to the upper crust and continues into the core of the edifice itself. Modeled primary magma compositions for Belknap, Mount Washington, and North Sister are similar to those from nearby cinder cones, indicating that shield volcanoes and nearby cinder cones are supplied by the same magma sources. The results demonstrate that the shield volcanoes have more complex, shallow magmatic plumbing systems than that of the cinder cones.

http://dx.doi.org/10.1016%2Fj.jvolgeores.2018.10.011

24. PDF
Morgavi D. et al. The Grizzly Lake complex (Yellowstone Volcano, USA): Mixing between basalt and rhyolite unraveled by microanalysis and X-ray microtomography // Lithos. 2016. Vol. 260. P. 457–474.

Magma mixing is a widespread petrogenetic process. It has long been suspected to operate in concert with fractional crystallization and assimilation to produce chemical and temperature gradients in magmas. In particular, the injection of mafic magmas into felsic magma chambers is widely regarded as a key driver in the sudden triggering of what often become highly explosive volcanic eruptions. Understanding the mechanistic event chain leading to such hazardous events is a scientific goal of high priority. Here we investigate a mingling event via the evidence preserved in mingled lavas using a combination of X-ray computed microtomographic and electron microprobe analyses, to unravel the complex textures and attendant chemical heterogeneities of the mixed basaltic and rhyolitic eruption of Grizzly Lake in the Norris-Mammoth corridor of the Yellowstone Plateau volcanic field (YVF). We observe evidence that both magmatic viscous inter-fingering of magmas and disequilibrium crystallization/dissolution processes occur. Furthermore, these processes constrain the timescale of interaction between the two magmatic components prior to their eruption. X-ray microtomography images show variegated textural features, involving vesicle and crystal distributions, filament morphology, the distribution of enclaves, and further textural features otherwise obscured in conventional 2D observations and analyses. Although our central effort was applied to the determination of mixing end members, analysis of the hybrid portion has led to the discovery that mixing in the Grizzly Lake system was also characterized by the disintegration and dissolution of mafic crystals in the rhyolitic magma. The presence of mineral phases in both end member, for example, forsteritic olivine, sanidine, and quartz and their transport throughout the magmatic mass, by a combination of both mixing dynamics and flow imposed by ascent of the magmatic mass and its eruption, might have acted as a “geometric perturbation” of flow fields further fuelling mass exchange between magmas in terms of both chemical diffusion and crystal transfer. These results illuminate the complexity of mixing in natural magmatic systems, identifying several reaction-related textural factors that must be understood more deeply in order to advance our understanding of this igneous process.

http://dx.doi.org/10.1016%2Fj.lithos.2016.03.026

25. U10290
Namur O. et al. Sulfur solubility in reduced mafic silicate melts: Implications for the speciation and distribution of sulfur on Mercury // Earth and Planetary Science Letters. 2016. Vol. 448. P. 102–114.

Chemical data from the MESSENGER spacecraft revealed that surface rocks on Mercury are unusually enriched in sulfur compared to samples from other terrestrial planets. In order to understand the speciation and distribution of sulfur on Mercury, we performed high temperature (1200–1750?°C), low- to high-pressure (1 bar to 4 GPa) experiments on compositions representative of Mercurian lavas and on the silicate composition of an enstatite chondrite. We equilibrated silicate melts with sulfide and metallic melts under highly reducing conditions (IW-1.5 to IW-9.4; IW = iron-wustite oxygen fugacity buffer). Under these oxygen fugacity conditions, sulfur dissolves in the silicate melt as S2? and forms complexes with Fe2+, Mg2+ and Ca2+. The sulfur concentration in silicate melts at sulfide saturation (SCSS) increases with increasing reducing conditions (from <1 wt.% S at IW-2 to >10 wt.% S at IW-8) and with increasing temperature. Metallic melts have a low sulfur content which decreases from 3 wt.% at IW-2 to 0 wt.% at IW-9. We developed an empirical parameterization to predict SCSS in Mercurian magmas as a function of oxygen fugacity (fO2), temperature, pressure and silicate melt composition. SCSS being not strictly a redox reaction, our expression is fully valid for magmatic systems containing a metal phase. Using physical constraints of the Mercurian mantle and magmas as well as our experimental results, we suggest that basalts on Mercury were free of sulfide globules when they erupted. The high sulfur contents revealed by MESSENGER result from the high sulfur solubility in silicate melt at reducing conditions. We make the realistic assumption that the oxygen fugacity of mantle rocks was set during equilibration of the magma ocean with the core and/or that the mantle contains a minor metal phase and combine our parameterization of SCSS with chemical data from MESSENGER to constrain the oxygen fugacity of Mercury's interior to IW-5.4±0.4. We also calculate that the mantle of Mercury contains 7–11 wt.% S and that the metallic core of the planet has little sulfur (<1.5 wt.% S). The external part of the Mercurian core is likely to be made up of a thin (<90 km) FeS layer.

http://dx.doi.org/10.1016%2Fj.epsl.2016.05.024

26. U10290
Peters B.J., Day J.M.D., Taylor L.A. Early mantle heterogeneities in the Reunion hotspot source inferred from highly siderophile elements in cumulate xenoliths // Earth and Planetary Science Letters. 2016. Vol. 448. P. 150–160.

Ultramafic cumulate rocks form during intrusive crystallization of high-MgO magmas, incorporating relatively high abundances of compatible elements, including Cr and Ni, and high abundances of the highly siderophile elements (HSE: Os, Ir, Ru, Pt, Pd, Re). Here, we utilize a suite of cumulate xenoliths from Piton de la Fournaise, La Reunion (Indian Ocean), to examine the mantle source composition of the Reunion hotspot using HSE abundances and Os isotopes. Dunite and wherlite xenoliths and associated lavas from the Piton de la Fournaise volcanic complex span a range of MgO contents (46 to 7 wt.%), yet exhibit remarkably homogeneous 187Os/188Os (0.1324±0.0014, 2?), representing the Os-isotopic composition of Reunion hotspot primary melts. A significant fraction of the xenoliths also have primitive upper-mantle (PUM) normalized HSE patterns with elevated Ru and Pd (PUM-normalized Ru/Ir and Pd/Ir of 0.8–6.3 and 0.2–7.2, respectively). These patterns are not artifacts of alteration, fractional crystallization, or partial melting processes, but rather require a primary magma with similar relative enrichments. Some highly olivine-phyric (>40 modal percent olivine) Piton de la Fournaise lavas also preserve these relative Ru and Pd enrichments, while others preserve a pattern that is likely related to sulfur saturation in evolved melts. The estimate of HSE abundances in PUM indicates high Ru/Ir and Pd/Pt values relative to carbonaceous, ordinary and enstatite chondrite meteorite groups. Thus, the existence of cumulate rocks with even more fractionated HSE patterns relative to PUM suggests that the Reunion hotspot samples a yet unrecognized mantle source. The origin of fractionated HSE patterns in Reunion melts may arise from sampling of a mantle source that experienced limited late accretion (<0.2% by mass) compared with PUM (0.5–0.8%), possibly involving impactors that were distinct from present-day chondrites, or limited core–mantle interactions. Given the remarkably homogeneous Os, Pb, and noble-gas isotopic signatures of Reunion, which plot near the convergence point of isotopic data for many hotspots, such a conclusion provides evidence for an early differentiated and subsequently isolated mantle domain that may be partially sampled by some ocean island basalts.

http://dx.doi.org/10.1016%2Fj.epsl.2016.05.015

27. PDF
Sawlan M.G. Alteration, mass analysis, and magmatic compositions of the Sentinel Bluffs Member, Columbia River flood basalt province // Geosphere. 2018. Vol. 14, № 1. P. 286–303.

Accurate characterization of the magmatic compositions of flood basalt lavas is fundamental to interpretations of magma genesis, stratigraphy, and correlation across these extensive provinces. Analysis of the geochemistry of the Sentinel Bluffs Member of the Grande Ronde Basalt, Columbia River Basalt Group (northwestern USA), demonstrates that a mass-based methodology, similar to those routinely used in studies of weathering and soil formation, enables the identification of subtle and previously unrecognized low-temperature alteration, and the determination of primary magmatic geochemical characteristics in rocks modified by secondary processes. This methodology, here termed mass analysis, employs concentrations and ratios of immobile elements, which are not transported by low-temperature alteration processes, to show that alteration has resulted in loss of rock mass due to mineral dissolution in anoxic groundwater. Immobile element abundances corrected for mass loss permit the identification and province-wide correlation of individual flows and flow packages, even for rocks that have undergone nearly 50% mass loss. The methodology developed with Sentinel Bluffs lavas is applicable to other lavas of the Columbia River flood basalt province, and most likely to other volcanic provinces in which lavas have undergone long-term interaction with groundwater.

http://dx.doi.org/10.1130%2FGES01188.1

28. U59752
Scaillet B., Holtz F., Pichavant M. Experimental Constraints on the Formation of Silicic Magmas // Elements. 2016. Vol. 12, № 2. P. 109–114.

A rich history of experimental petrology has revealed the paths by which silicic igneous rocks follow mineral–melt equilibria during differentiation. Subdividing these rocks by ‘molar Al versus Ca + Na + K’ illustrates first-order differences in mineralogy and gives insight into formation mechanisms. Peraluminous magmas, formed by partial melting of sediments, largely owe their attributes and compositions to melting reactions in the protoliths, whereas most metaluminous felsic magmas record both continental and mantle inputs. Peralkaline rhyolites are mainly derived from either protracted crystallization or small degrees of partial melting of basalt, with only a marginal crustal contribution. Most silicic magmas hold 3–7 wt% H2Omelt, which is inversely correlated with pre-eruptive temperature (700 °C to >950 °C) but unrelated to their reduced/oxidized state.

https://doi.org/10.2113/gselements.12.2.109

29. U10290
Stefansson A., Barnes J.D. Chlorine isotope geochemistry of Icelandic thermal fluids: Implications for geothermal system behavior at divergent plate boundaries // Earth and Planetary Science Letters. 2016. Vol. 449. P. 69–78.

The chlorine isotope composition of thermal fluids from Iceland were measured in order to evaluate the source of chlorine and possible chlorine isotope fractionation in geothermal systems at divergent plate boundaries. The geothermal systems studied have a wide range of reservoir temperatures from 40 to 437?°C and in-situ pH of 6.15 to 7.15. Chlorine concentrations range from 5.2 to 171 ppm and ?37Cl values are ?0.3 to +2.1‰ (n=38). The ?37Cl values of the thermal fluids are interpreted to reflect the source of the chlorine in the fluids. Geothermal processes such as secondary mineral formation, aqueous and vapor speciation and boiling were found to have minimal effects on the ?37Cl values. However, further work is needed on incorporation of Cl into secondary minerals and its effect on Cl isotope fractionation. Results of isotope geochemical modeling demonstrate that the range of ?37Cl values documented in the natural thermal fluids can be explained by leaching of the basaltic rocks by meteoric source water under geothermal conditions. Magmatic gas partitioning may also contribute to the source of Cl in some cases. The range of ?37Cl values of the fluids result mainly from the large range of ?37Cl values observed for Icelandic basalts, which range from ?0.6 to +1.2‰.

http://dx.doi.org/10.1016%2Fj.epsl.2016.05.041

30. PDF
T. Ohashi, T. Sakamaki et al. Pressure–induced structural changes of basaltic glass // J. Mineral. Petrol. Sci. 2018. Vol. 113, № 6. P. 286-292.

The structural determinations of basaltic glass under pressure were conducted. The obtained structure factor, S(Q) indicates that the position of the first sharp diffraction peak (FSDP) shifts to higher–Q region with increasing pressure up to 6 GPa. This result indicates the intermediate–range order structure of glass becomes compact. The radial distribution function, RDF shows the shrinkage of the average T–T length with increasing pressure, but indicates no detectable change of the average T–O length (T = Si4+ and Al3+) and its coordination. This result implies that the positional shift of the FSDP is attributed to the polymerization of TO4 tetrahedra to form …–T–O–T–… linkage, with the concomitant narrowing of the mean T–O–T angle. The RDF also shows that the distances of Fe(Mg)–O extend due to the changes in the structural roles of Fe and Mg from the network modifiers to the charge–balancing cations. The structural data of the recovered condition imply that the tetrahedral networks of the present glass is permanently polymerized and densified after compression. On the other hand, the network modifier cations undergo both contraction and relaxation processes.

https://doi.org/10.2465/jmps.171114a

31. PDF
Tapsoba B. et al. Chemical and Sr-Nd compositions and 40Ar/39Ar ages of NW-trending dolerite dikes of Burkina Faso: Evidence for a Mesoproterozoic magmatism in the West African Craton // Geoscience Frontiers. 2018. Vol. 9, № 6. P. 1957–1980.

The Paleoproterozoic basement of the northeastern part of the Leo-Man craton is intruded by generally NW-trending dikes. These regional scale dikes extend over 1000 km in Burkina Faso, Mali and Niger. We present chemical and Sr-Nd isotope compositions, as well as 40Ar/39Ar ages of these dikes with the following strikes N98°–N112°, and N114°–N124° in NE Burkina Faso. Field relationships show that the dikes are posterior to all other rock types dated between 2.26 Ga and 2.0 Ga. Chemical data indicate that the dikes are continental flood basalts and composed of low-Ti (TiO2 ? 2 wt.%) sub-alkaline basalts and andesites. They exhibit a minor negative Europium anomaly (0.86–0.99) and slightly fractionated REE patterns ((La/Yb)N = 2.5–9.1; YbN = 9.5–19.9). The ratios of Th/Ta (1.3–11.4) and Ce/Pb (5.2–58.5) suggest a varying crustal assimilation of the dike magmas during ascent in the continental crust for all studied samples. Calculated P-T conditions indicate that the magma reached temperatures of 1285 °C (calculated from olivine compositions) and pressures of 6.9 kbar (calculated for pyroxene minerals). Calculated initial 87Sr/86Sr (0.70040–0.70260) and ?Nd(t) = +2.1 to ?3.5 at 1575 Ma, also point to a crustal contamination with the most primitive samples showing TDM values of 1946 Ma and 2154 Ma. The low values of La/Ba (<0.2) and Nb/La (<1.0), contrast with the low Th/Nb (<0.9), and suggest a lithospheric mantle or subduction-modified mantle as possible source for the dikes. Sr-Nd data, Mg# and Nb-Ta-Zr-Y-Th-Tb-Yb compositions further suggest that the most primitive samples were emplaced in a none orogenic setting and their magmas were subjected to variable crustal contaminations. Literature and the present whole rock 40Ar/39Ar age determinations show that the dikes were emplaced during a widespread Mesoproterozoic magmatism between 1.6 Ga and 1.2 Ga, and were affected by a thermal event causing the argon systematics resetting, best constrained by the date of sample KK1 (1236 ± 20 Ma, 40Ar/36Ar = 294 ± 13, MSWD = 2.2). Contemporaneous 1590–1570 Ma extensive magmatism is reported in other crustal blocks in Baltica (Sveconorw-Goth, svecofennian) NW Laurentia (Slave craton, Yukon), and Australia (Gawler craton), and together with the 1575 studied dikes, are related to the breakup of the supercontinent Nuna.

http://dx.doi.org/10.1016%2Fj.gsf.2017.12.015

32. U10290
van den Hove J.C. et al. Controls on volcanism at intraplate basaltic volcanic fields // Earth and Planetary Science Letters. 2017. Vol. 459. P. 36–47.

A broad range of controlling mechanisms is described for intraplate basaltic volcanic fields (IBVFs) in the literature. These correspond with those relating to shallow tectonic processes and to deep mantle plumes. Accurate measurement of the physical parameters of intraplate volcanism is fundamental to gain an understanding of the controlling factors that influence the scale and location of a specific IBVF. Detailed volume and geochronology data are required for this; however, these are not available for many IBVFs. In this study the primary controls on magma genesis and transportation are established for the Pliocene–Recent Newer Volcanics Province (NVP) of south-eastern Australia as a case-study for one of such IBVF. The NVP is a large and spatio-temporally complex IBVF that has been described as either being related to a deep mantle plume, or upper mantle and crustal processes. We use innovative high resolution aeromagnetic and 3D modelling analysis, constrained by well-log data, to calculate its dimensions, volume and long-term eruptive flux. Our estimates suggest volcanic deposits cover an area of 23,100 ± 530 km2 and have a preserved dense rock equivalent of erupted volcanics of least 680 km3, and may have been as large as 900 km3. The long-term mean eruptive flux of the NVP is estimated between 0.15 and 0.20 km3/ka, which is relatively high compared with other IBVFs. Our comparison with other IBVFs shows eruptive fluxes vary up to two orders of magnitude within individual fields. Most examples where a range of eruptive flux is available for an IBVF show a correlation between eruptive flux and the rate of local tectonic processes, suggesting tectonic control. Limited age dating of the NVP has been used to suggest there were pulses in its eruptive flux, which are not resolvable using current data. These changes in eruptive flux are not directly relatable to the rate of any interpreted tectonic driver such as edge-driven convection. However, the NVP and other IBVFs used for comparison have long-term eruptive fluxes that are considerably less than definitive plume-related volcanic systems. Along with their spatio-temporal patterns and other analysis it is suggested that the NVP and the vast majority of low- and high-flux IBVFs appear to be the result of tectonic processes without requiring additional thermal input from a deep mantle source. Considering a control on volcanism by tectonic processes, the range of eruptive flux of IBVFs is related to variations in the rate of the effecting tectonic process, mantle composition, and the size of the mantle source zone where melt generation and accumulation is taking place.

http://dx.doi.org/10.1016%2Fj.epsl.2016.11.008

33. U16831
Yamasaki T., Nanayama F. Enriched mid-ocean ridge basalt-type geochemistry of basalts and gabbros from the Nikoro Group, Tokoro Belt, Hokkaido, Japan // J. Mineral. Petrol. Sci. 2017. Vol. 112, № 6. P. 311–323.

The Tokoro Belt is a subduction complex located in eastern Hokkaido, Japan. The Nikoro Group, a constituent of the Tokoro Belt, is composed mainly of Late Jurassic to Early Cretaceous igneous rocks intercalated with bedded chert and limestone. These rocks have been regarded as fragments of seamounts. Here, we report new whole–rock geochemistry, clinopyroxene major and trace element compositions of the basalts and gabbros, and re–evaluate the origin and geodynamic setting of the Nikoro Group. The gabbros showed ophitic texture and contain fresh, large oikocrystic clinopyroxenes. Fe–Mg partitioning between the clinopyroxenes and whole–rock (i.e., melt) can be regarded as in equilibrium. The trace element composition of the clinopyroxenes within the gabbros and the whole–rock geochemistry of the gabbroic rocks are almost identical to the basalts. This evidence suggests that the whole–rock compositions were not extensively modified and the gabbroic rocks represent the melt composition. Whole–rock trace elements indicated Enriched Mid–Ocean Ridge Basalt (E–MORB)–type patterns as well as ‘garnet signatures’ [e.g., (Sm/Yb)N > 1]. After correction of the gabbros and basalts for the fractionation effect to Mg# = 0.72, the whole–rock chemistry suggests a significantly shallow lithosphere–asthenosphere boundary depth of ~ 0–km. Whole–rock (Sm/Yb)N ratios also confirm the same results. These geochemical results constrain the geodynamic setting of the Nikoro Group; the greenstone most likely originated from a plume–influenced ridge in the Pacific Ocean basin during the Middle Jurassic to Early Cretaceous.

https://doi.org/10.2465/jmps.170613

34. PDF
Аблесимов Н.Е. Из чего производят непрерывное базальтовое волокно (НБВ) // Композитный мир. 2017. № 6 (75). С. 56–60.

Употребление термина базальт в практике производства и маркетинга НБВ является не строгим, а, скорее, тривиальным, бытовым. Научным является термин - горные породы базальтового состава. Почему? Базальты - разновидность магматических пород, образовавшаяся из глубинного высокотемпературного алюмосиликатного раствора. Собственно базальтом называют эффузивные (излившиеся на поверхность) породы «кайнотипные» с неизмененными минералами. Обычно по времени своего излияния, относящиеся к третичному и четвертичному периодам и реже - к юрскому и меловому. «Палеотипные» базальты, сильно разрушенные и измененные процессами хлоритизации, обычно являются более древними и выделяются под названием диабазов. Подобные палеобазальты характерны для Урала, Карелии и Кавказа. Известен также амфиболит, образующийся в результате изменения средних и оснoвных магматических пород. Описание сырьевой базы для производства непрерывных базальтовых волокон изложено в данной статье.

https://elibrary.ru/item.asp?id=36322311

35. 04092X
Аблесимов Н.Е., Малова Ю.Г. Каменное (базальтовое) волокно: исследования и научные школы // Научное обозрение. Технические науки. 2016. № 6. С. 5–9.

В работе обобщены данные о 78 диссертациях на русском и украинском языках, посвященных исследованиям как самих каменных (базальтовых) волокон и ваты, так и композитов армированных ими. Охватывается период с 1993 по 2013 годы (2014-2016 годы отражены частично). Области исследования: химические (10), технические (66) и экономические (2) науки.

https://elibrary.ru/item.asp?id=27685289

36. PDF
Андреев В.В. и др. Исследование технологии получения стеклокристаллических материалов на основе базальтов Приморского края // Вестник Инженерной школы Дальневосточного Федерального Университета. 2017. № 3 (32). С. 156–166.

Магматические горные породы - базальты или диабазы используются как исходный природный материал при создании новых материалов и разработки эффективных технологий по их получению. Так, базальты применяются в качестве сырья при производстве базальтового волокна, каменолитных изделий (брусчатка, трубы, желоба и др.) и петроситаллов, в настоящее время ведутся исследования в области базальтовых покрытий. В данной статье представлено исследование технологии получения стеклокристаллических материалов на основе базальтов Приморского края (Шкотовское и Шуфанское плато). Проведен анализ базальтов различных месторождений Приморского края по их химическому и фазовому составу. Данные микроскопического и рентгенофазового анализа до и после термической обработки показали явную зависимость процесса кристаллизации от состава шихты, температуры обработки, а также от самого метода термической обработки образцов базальтов. В частности, установлено, что исследуемые базальты обладают повышенным коэффициентом кислотности, и для получения кристаллической структуры необходимо проводить термическую обработку - кристаллизацию (отжиг), при температуре не менее 950 °С. Исследовано влияние различных компонентов, таких как оксид кальция (CaO), оксид магния (MgO), а также минерала доломита (Ca,Mg[CO3]2) на кристаллизацию базальта. В качестве основных кристаллических фаз, полученных после термической обработки базальтовых композиций, выступали минералы анортит и авгит. Представленная технология позволит получать стеклокристаллические материалы на основе базальтов Приморского края.

https://elibrary.ru/item.asp?id=30034593

37. 006651
Гольдшлегер Н.Ф., Цивадзе А.Ю. и др. Супрамолекулярные гели на основе солей желчных кислот // Успехи Химии. 2017. Т. 86. № 4. С. 269–297.

Обобщены результаты исследований по формированию и свойствам супрамолекулярных гидрогелей на основе солей желчных кислот - биологических поверхностно-активных веществ. Основное внимание уделено свойствам дезоксихолата натрия, в том числе его способности к эффективной солюбилизации и транспортировке гидрофобных лекарств, связыванию ионов металлов и формированию флуоресцентных гидрогелей. Обсуждены особенности формирования гидрогелей с участием краун-содержащих фталоцианинов и дезоксихолата натрия, включая агрегатное состояние активного компонента и его флуоресцентные свойства. Библиография - 184 ссылки.

https://elibrary.ru/item.asp?id=28867107

38. 027681
Зимин Д.Е., Ходакова Н.Н. Химический состав горных пород, пригодных для выработки базальтовых волокон, устойчивых к агрессивным средам // Стекло и керамика. 2016. № 3. С. 9–15.

Представлены результаты исследований устойчивости базальтовых волокон различного химического и минералогического составов к агрессивным средам. Показана их высокая химическая стойкость к воде, кислотам и щелочам. Предложен параметр для прогнозирования химической стойкости волокон в зависимости от содержания оксидов металлов в стекле. Наиболее достоверные результаты дает метод определения изменения прочности волокон после их обработки в агрессивных средах

https://elibrary.ru/item.asp?id=27811598

39. 035724
Казаченко В.Т., Перевозникова Е.В., Лаврик С.Н. Геохимические и изотопные «метки» древних габброидов в триасовых метаморфизованных металлоносных осадках, скарнах и рудах скарновых месторождений Сихотэ-Алиня // Вестник Кольского научного центра РАН. 2016. № 4 (27). С. 16–36.

По геологическим, геохимическим и изотопным данным, триасовые метаморфизованные металлоносные осадки (марганцево-силикатные породы, силикатно-магнетитовые руды и др.) и скарны Сихотэ-Алиня изначально являлись продуктами размыва (поздний анизий - конец триаса) латеритной коры выветривания островов и окраины Ханкайского массива. Свинец руд скарновых и жильных месторождений Сихотэ-Алиня по изотопным отношениям сопоставим со Pb слагавших острова габброидов Сергеевского, Владимиро- Александровского и Калиновского комплексов

https://elibrary.ru/item.asp?id=28351573

40. PDF
Косарев А.М., Серавкин И.Б., Шафигуллина Г.Т. Баймакский колчеданоносный палеовулканический комплекс // Геологический вестник. 2018. № 2. С. 14–35.

В работе рассмотрены особенности минералогии, петрографии и геохимии вулканитов базальт-андезит-риодацитового состава баймакского колчеданоносного комплекса, завершающего формирование фронтальной островной дуги позднеэмсского возраста на Южном Урале. Использованы новые материалы по содержаниям микроэлементов (анализы ICP MS, ХЛ ИГМ СО РАН, г. Новосибирск) и микрозондовые определения химического состава минералов (ХЛ ИГ КарНЦ РАН, г. Петрозаводск). Обсуждается сериальная принадлежность вулканитов и вопросы их петрогенеза. Породы этого комплекса имеют повышенную магнезиальность, представлены фациальным рядом, включающим тефроидные, эффузивные, пирокластические, экструзивные, субвулканические и гиповулканические породы. Рассмотрены вопросы типизации кислых пород и проблемы их генезиса. Предполагается, что в эффузивной фации присутствуют кислые породы - продукты кристаллизационной и флюидной дифференциации на путях движения расплавов к поверхности Земли, гибридные породы дацит-риодацитового состава, возникшие при загрязнении кислых магм частично или полностью раскристаллизованными габброидами или базитами предшествующих этапов вулканизма, и продукты частичного плавления базитов нижней коры. Спецификой вулканитов баймакского комплекса являются повышенные концентрации и большой размах колебаний Ba, Pb и Au как в слабоизмененных породах, так и в метасоматитах околорудных ореолов.

https://elibrary.ru/item.asp?id=35574527

41. 002260
Кренёв В.А. и др. Физико-химическое моделирование и модифицирование состава магматических и метаморфических пород. Диориты // Неорганические материалы. 2018. Т. 54. № 8. С. 907–910.

Приведены общие сведения о семействе диоритов – средних плутонических породах подотряда нормально- и низкощелочных. На примере кварцевого диорита Горного Алтая рассмотрены возможности применения разработанных в ИОНХ РАН методов модифицирования состава магматических и метаморфических пород для получения минеральных волокон и изделий каменного литья.

https://elibrary.ru/item.asp?id=35446317

42. 002260
Кренёв В.А., Дергачева Н.П., Иванов В.К. Физико-химическое моделирование и модифицирование состава магматических и метаморфических пород. Основные пикробазальты // Неорганические материалы. 2018. Т. 54. № 4. С. 394–398.

На примере пикробазальта месторождения Булатовское (Архангельская область), рассмотрены возможности применения разработанных в ИОНХ РАН методов модифицирования состава магматических и метаморфических пород для получения минеральных волокон и изделий каменного литья.

https://elibrary.ru/item.asp?id=32839234

43. PDF
Макаров В.П., Сопубеков Н.А. Оценка пригодности алевролитового базальта для производства супертонкого волокна // Вестник Кыргызско-Российского Славянского Университета. 2017. Т. 17. № 8. С. 159–163.

Приведены результаты комплексного изучения алевролитового базальта месторождения Таш-Булак с целью оценки его пригодности для производства высококачественного супертонкого волокна.

https://elibrary.ru/item.asp?id=30362049

44. 033184
Маркова Ю.Н. и др. Влияние изменений климата позднего плейстоцена-голоцена на состав донных отложений Селенгино-Бугульдейской перемычки озера Байкал // Стратиграфия. Геологическая корреляция. 2018. Т. 26. № 3. С. 109–116.

Исследование донных отложений озера Байкал, вскрытых скважиной подводного бурения на Селенгино-Бугульдейской перемычке (керн VER93-2 st.24GC), позволило реконструировать климатические события в Байкальском регионе за последние 20-25 тыс. лет. На основании данных о распределении химических элементов в разрезе скважины методом физико-химического моделирования рассчитан минеральный состав осадков. Изучение изменения соотношений глинистых минералов в разрезе позволило выделить плейстоцен-голоценовую границу, постледниковое потепление беллинг-аллеред и похолодание поздний дриас. Расчетные данные по минеральному составу донных отложений керна VER93-2 имеют хорошую сходимость с результатами рентгенофазового анализа. Предложенный подход может быть использован для расчета минерального состава других осадочных разрезов с изученным химическим составом.

https://elibrary.ru/item.asp?id=35104751

45. 009132
Мизиряк Д.Г. Петрохимическая характеристика магматических горных пород и гидротермально-метасоматических образований Кедровского золоторудного поля // Разведка и охрана недр. 2017. № 9. С. 27–32.

По результатам силикатного анализа и петрографического описания шлифов дана характеристика основных типов магматических горных пород, представляющих габбро-анортозитовую и гранодиорит-лейкогранитовую магматические формации Кедровского золоторудного поля. Охарактеризованы породы рудоносной гидротермально-метасоматической формации березитов.

https://elibrary.ru/item.asp?id=30032185

46. 001408
Николаев Г.С., Арискин А.А., Бармина Г.С. Spinmelt-2.0: Численное моделирование равновесия шпинелид-расплав в базальтовых системах при давлениях до 15 кбар: I. формулировка, калибровка и тестирование модели // Геохимия. 2018. № 1. С. 28–49.

Проведено тестирование существующих моделей равновесия хромшпинелид - расплав: программы семейства MELTS Гиорсоу с коллегами, программа SPINMELT Арискина - Николаева и "Шпине-левый калькулятор MELT-CHROMITE" Пустоветова и Редера. Представлена новая калибровка модели SPINMELT, которая позволяет рассчитывать шестикомпо-нентный (Mg, Fe2+, Cr, Al, Fe3+, Ti) состав хромшпинелида и T - /02-условия его стабильности на ликвидусе для базальтового расплава при давлениях до 15 кбар. В ее основу положены данные 392 опытов с системами нормальной щелочности при /о2 < QFM + 2, представляющих 43 экспериментальных исследования. Расширенная, относительно предыдущей калибровки, экспериментальная база позволила не только учесть барический эффект, но и распространить модель на высокоглиноземистые и водосодержащие системы. Тестирование модели SPINMELT-2.0 показало, что погрешность расчета температуры равновесия шпинелид-расплав увеличивается с ростом давления от 16°С для 1 атм до 50°С при 15 кбар. Составы шпинелида воспроизводятся с точностью не хуже 3 ат. % для Al и Cr; погрешности для других катионов не превышают 1 ат. %.

https://elibrary.ru/item.asp?id=32659114

47. PDF
Оснос М.С., Оснос С.П. Исследование процессов плавления базальтовых пород при производстве непрерывных волокон // Композитный Мир. 2018. № 2 (77). С. 80–85.

В настоящее время в мире существует значительный интерес к производству и применению базальтовых непрерывных волокон (БНВ) и материалов на их основе. БНВ обладают достаточно высокой прочностью, стойкостью к воздействию агрессивных сред, долговечностью, электроизоляционными свойствами. Производство базальтовых волокон имеет практически неограниченную и доступную сырьевую базу. Базальтовые породы - это готовое магматическое сырье, энергетические затраты на подготовку которого выполнены природой. Однако производство и широкое применение БНВ сдерживается относительной сложностью технологий их производства. Поэтому особую актуальность представляют научные работы по исследованию процессов и технологий производства базальтовых волокон. В настоящей статье приведены результаты исследований процессов плавления базальтов, проведенных специалистами «BASALT FIBER MATERIALS TECHNOLOGY DEVELOPMENT Co Limited» («BFM TD») на опытно-промышленных и промышленных установках по производству БНВ на Украине, России и в КНР.

http://www.kompomir.ru/projects/reading/

48. PDF
Оснос М.С., Оснос С.П. Проведение исследований и выбор месторождений базальтовых пород для производства непрерывных волокон // Композитный Мир. 2018. № 1 (76). С. 50–58.

В статье впервые представлены сведения о классификации месторождений базальтовых пород, а также опыт компаний по обследованию месторождений; методики и оборудование для проведения исследований образцов базальтов и их расплавов, исследование способностей расплавов к волокнообразованию и параметров вытяжки первичных волокон; оценка степени пригодности базальтовых пород для производства непрерывных волокон.

http://www.kompomir.ru/projects/reading/

49. 001200
Персиков Э.С., Бухтияров П.Г., Сокол А.Г. Вязкость водосодержащих кимберлитовых и базальтовых расплавов при высоких давлениях // Геология и геофизика. 2017. Т. 58. № 9. С. 1377–1387.

Получены новые экспериментальные данные по температурной и барической зависимостям вязкости водосодержащих модельных кимберлитовых расплавов (система: силикат 82 + карбонат 18 мас. %, степень деполимеризации - 100·NBO/ T = 313 - безводный состав, 100·NBO/ T = 247 - содержание воды 3 мас. %) при давлении Н2О, равном 100 МПа, и при литостатическом давлении 5.5 и 7.5 ГПа в температурном диапазоне 1300-1950 °С. Установлено, что зависимость вязкости таких расплавов от температуры соответствует экспоненциальному уравнению Аррениуса-Френкеля - Эйринга в исследованном диапазоне температур и давлений. Впервые установлен линейный рост энергий активации вязкого течения водосодержащих кимберлитовых расплавов с увеличением давления. Вязкость водосодержащих кимберлитовых расплавов экспоненциально растет в изотермических условиях ( Т = 1800 °С) почти на порядок величины с ростом давления от 100 МПа до 7.5 ГПа. Полученные экспериментальные данные по вязкости водосодержащих кимберлитовых расплавов (погрешность ± 30 отн. %) сравнены с прогнозными зависимостями вязкости безводных кимберлитовых и базальтовых расплавов (100·NBO/ T = 51.5), а также водосодержащих базальтовых расплавов (100·NBO/ T = 80). Показано, что при соизмеримых значениях температуры вязкость водосодержащих кимберлитовых расплавов при умеренном давлении ( Р = 100 МПа) почти на порядок величины меньше вязкости водосодержащих базальтовых расплавов, а при высоких давлениях ( Р = 7.5 ГПа), напротив, более чем в два раза больше вязкости водосодержащих базальтовых расплавов. Впервые установлено, что растворение воды в кимберлитовых расплавах в пределах ошибок измерений не оказывает принципиального влияния на изменения их вязкости как при умеренных (100 МПа), так и при высоких давлениях (до 7.5 ГПа). Тогда как вязкость базальтовых расплавов значительно снижается при растворении в них воды при умеренных давлениях (100 МПа), но при высоких давлениях ( Р > 3.5 ГПа) эффект растворенной воды также нивелируется.

https://elibrary.ru/item.asp?id=30029596

50. 04568X
Писаренко М.В., Патраков Ю.Ф. Комплексное освоение месторождений Барзасского геолого-экономического района // Горная промышленность. 2017. № 2 (132). С. 31.

В качестве возможного направления расширения минеральносырьевой базы Кузнецкого бассейна предлагается вовлечение в промышленное освоение запасов высокозольного горючего сланца Барзасского геолого-экономического района. Учитывая ресурсный и инфраструктурный потенциал данного района, такая возможность просматривается при реализации комплексного проекта с формированием промышленного кластера на базе производства каменного литья с получением широкой гаммы продуктов высокой добавленной стоимостью и минимальным экологическим воздействием на окружавшую среду при максимальном использовании всех полезных компонентов месторождений. По технологии каменного литья путем плавления переработке подвергаются базальты Мариинского участка и подобные им по составу зольные отходы. В качестве топлива для производства каменного литья предлагается использовать горючий газ и жидкие углеводородные продукты полукоксования сланцев Дмитриевского месторождения, добыча которых осуществлять попутно с базальтами, а зольные отходы сланцев использовать как сырье в основном процессе.

https://elibrary.ru/item.asp?id=29214513

51. 027681
Руми М.Х. и др. Химическая стойкость материалов на основе плавленого минерального сырья Узбекистана // Стекло и керамика. 2017. № 7. С. 32–36.

Изучены химическая стойкость, изменение состава и структуры материалов на основе плавленых минералов и натриевого жидкого стекла при взаимодействии с агрессивными жидкостями. Методами ИК-спектроскопии и химического анализа определено, что при воздействии кислот степень полимеризации силикатных композиций увеличивается пропорционально уменьшению содержания катионов-модификаторов. Воздействие щелочного раствора приводит к смещению полос валентных колебаний связей Si-O-Si в низкочастотную область из-за уменьшения содержания SiO2. Все исследуемые материалы устойчивы в воде и 3%-ном CH3COOH. В растворах 20%-ной H2SO4 и 35%-ной NaOH максимальной устойчивостью обладают материалы на основе плавленых пироксенов

https://elibrary.ru/item.asp?id=29677746

52. 001200
Сасим С.А. и др. Шошонит-латитовая серия Восточного Забайкалья: 40Ar/39Ar возраст, геохимия и Sr-Nd изотопный состав пород Акатуевской вулканоплутонической ассоциации Александрово-Заводской впадины // Геология и геофизика. 2016. Т. 57. № 5. С. 962–982.

Приведены новые данные о возрасте, геохимии и изотопном составе Sr и Nd Акатуевского массива и комагматичных пород нижней пачки кайласской свиты (акатуевская вулканоплутоническая ассоциация), локализованных в пределах Александрово-Заводской впадины Восточного Забайкалья. Проведенное изотопное 40Ar/39Ar датирование амфиболов дает значения 154.8 ± 4.4 млн лет для монцогаббро ранней фазы Акатуевского массива; 160.7 ± 3.9 млн лет для монцонита главной фазы этого массива и 161.5 ± 1.7 млн лет для шошонитового базальта нижней пачки кайласской свиты. Ведущим петрогенетическим механизмом пород акатуевской вулканоплутонической ассоциации является процесс кристаллизационной дифференциации расплавов при подчиненной роли коровой контаминации, проявленной в минералого-петрографических особенностях некоторых геохимических и изотопных характеристиках пород. Характерной геохимической чертой пород акатуевской вулканоплутонической ассоциации является их обогащенность LILE, легкими REE, U, Th, Pb при резко проявленном дефиците элементов высокозарядной группы (Nb, Ti) и P. Изотопные Sr-Nd характеристики пород (87Sr/86Sr(160 млн лет) = 0.70642-0.70688 и ?Nd(160 млн лет) = -0.6…-2.2) свидетельствуют об их образовании из обогащенного мантийного источника типа EMII, а также отражают незначительное влияние процессов коровой контаминации на состав эволюционировавших расплавов.

https://elibrary.ru/item.asp?id=26006042

53. PDF
Сопубеков Н.А. Исследование химического состава алевролитовых горных пород // Наука. Образование. Техника. 2017. № 2 (59). С. 30–33.

Данная статья посвящена одной из актуальных проблем науки, техники и технологии: создания новых неорганических супертонких волокон с переработкой горных пород и изделий на их основе различного назначения. Цель работы: исследование физико-химических свойств алевролитовых пород, и разработка научно-технологических основ получения композитов. Использованы экспериментально-теоретические методы по исследованию составов и свойств композиционных материалов на основе супертонких волокон из горных пород. В результате исследованы химический состав и свойства алевролитовых горных пород в процессе получения супертонких волокон. Практическая значимость работы заключается в разработке технологий переработки алевролита методом пиролиза с целью получения активного наполнителя.

https://elibrary.ru/item.asp?id=29993019

54. 045834
Третьяков Г.А., Масленников В.В. Сопоставление минеральных ассоциаций в Курильщиках разных типов по данным парагенетического анализа и физико-химического моделирования // Минералогия. 2017. Т. 3. № 1. С. 71–81.

На основе физико-химического моделирования поведения элементов методом минимизации потенциала Гиббса впервые дана оценка вторичных преобразований различных пород в зависимости от их соотношений с нагретой морской водой в зоне рециклинга. Рассмотрены минеральные ассоциации, отлагающиеся при кондуктивном охлаждении раствора, покидающего зону реакции, что может интерпретироваться как один из механизмов формирования состава и зональности труб современных и древних курильщиков. Расчётные данные указывают на то, что температура в зоне взаимодействия морской воды с породами, их состав и «зрелость» гидротермальной системы являются важными факторами минералогического разнообразия рудных ассоциаций, отлагающихся на морском дне.Илл. 4. Табл. 1. Библ. 28.

https://elibrary.ru/item.asp?id=28945942

55. 044719
Уляшева Н.С. Геохимические особенности и геодинамическая обстановка формирования верхнепротерозойских отложений няровейской серии // Вестник института геологии Коми Научного центра Уральского отделения РАН. 2017. № 5 (269). С. 20–30.

В результате изучения геохимических особенностей верхнепротерозойских метаморфизованных вулканогенно-осадочных пород няровейской серии Центральной тектонической зоны Полярного Урала установлено, что они сформировались в окраинно-океанической обстановке, возможно в условиях задугового моря. В западной зоне распространения няровейской серии метабазальты представлены высокожелезистыми толеитами, а в восточной - высокомагниевыми. Геохимический состав у них схож и тождествен составу базальта E-MORB, что предполагает близкие условия генерации магматического расплава. Низкие содержания Nb, Zr и Hf в метабазальтах указывают на надсубдукционную природу данных образований. Среди метаосадочных пород няровейской серии широко распространены углеродсодержащие и безуглеродистые кварциты, которые хорошо коррелируются по содержанию редких и редкоземельных элементов. Среди углеродсодержащих кварцитов выделяются кремниевые и терригенно-кремниевые разновидности. Безуглеродистые кварциты образовались по терригенным породам. Анализ геохимического состава метаосадочных пород няровейской серии дал основание предположить, что их образование происходило за счет разрушения преимущественно богатых кремнием осадочных образований при участии кислых, средних и основных магматических пород зрелой континентальной коры раннепротерозойского возраста.

https://elibrary.ru/item.asp?id=29659404

56. PDF
Уляшева Н.С., Денисова Ю.В., Панфилов А.В. Метабазальты и метатуфы Няровейской серии (полярный Урал) // Геология, полезные ископаемые и проблемы геоэкологии, Башкортостана, Урала и сопредельных территорий. 2016. № 11. С. 30–31.

Нами изучены породы няровейской серии по руч. Няршор, Сядатояха, Графитовый, Харчерузь с западной стороны марункеуского комплекса и по руч. Ингилоръеган и его левым притокам с восточной стороны. Петрографические исследования позволили выделить по минеральному составу кварц­эпидот­хлорит­актинолитовые породы, залегающие в основном среди слюдисто­кварцевых сланцев.

https://elibrary.ru/item.asp?id=26232754

57. 001200
Федосеев Г.С., Воронцов А.А., Орехов А.А. Палеотравертины и квазитравертины Минусинского прогиба (Западная Сибирь): строение, состав и сравнительная характеристика // Геология и геофизика. 2017. Т. 58. № 8. С. 1157–1173.

Детально изучен квазитравертин, впервые обнаруженный в Чебаково-Балахтинской впадине Минусинского прогиба (Республика Хакасия, Россия) и получивший свое название благодаря внешнему сходству с классическими ископаемыми травертинами (палеотравертинами). Он слагает небольшой тонкий слой между кровлей базальт-долеритового силла и вмещающими известковистыми алевролитами. Проведено детальное его изучение и сравнение с девонскими палеотравертинами, находящимися на удалении нескольких километров, указаны визуальные и петрогеохимические признаки их сходства и различия. Согласно модели авторов, формирование квазитравертина происходило в два этапа - седиментационный и гидротермально-метасоматический. На первом этапе образовались тонкослоистые известняки, находящиеся в тесной ассоциации с известковистыми алевролитами раннедевонской шунетской свиты, а на втором этапе они подверглись гидротермально-метасоматической проработке, которая сопровождалась попутным отложением кальцита, пренита и пиробитума (керита).

https://elibrary.ru/item.asp?id=29945765

58. 045270
Хакбердиев Н.М. Базальты ходжирбулакской свиты и оценка их пригодности в качестве базальтового волокна (горы Сурхантау, юго-западные отроги Гиссарского хребта) // Вестник Пермского Университета. Геология. 2017. Т. 16. № 2. С. 104–113.

Изложены результаты предварительной оценки базальтов ходжирбулакской свиты гор Сурхантау в качестве базальтового волокна. По данным петрографического исследования породы представлены базальтами миндалекаменной структуры. По содержанию стекловой массы и миндалин кальцита выделены три группы базальтов. Установлена обратная связь между содержаниями основной массы и содержанием кальцита: чем больше основной массы вулканитов, тем меньше кальцита, и наоборот. Модуль кислотности составляет в среднем 3,52.

https://elibrary.ru/item.asp?id=29808688

59. 039284
Шевко В.М. и др. Термодинамическое моделирование получения карбида кальция и ферросплава из Даубабинского базальта // Международный журнал прикладных и фундаментальных исследований. 2018. № 5. С. 55–60.

В статье приведены результаты исследований термодинамического моделирования взаимодействия базальта месторождения Даубаба с углеродом в температурном интервале 1000–2500?°С и давлении 0,1МПа. Количество углерода изменялось от 20 до 45?% от массы базальта. Исследования проведены с использованием программного комплекса HSC – 5,1 на основе принципа минимума изменения энергии Гиббса. Установлено, что карбид кальция в системе базальта Даубаба (40,88?% SiO2, 19,58?% CaO, 13,36?% Al2O3, 15,25?% FeO, 6,68?% MgO, 1,74?% Na2O, 0,98?% TiO2, 0,41?% MnO) образуется при температуре более 1800?°С, кремний и алюминий восстанавливаются и переходят в ферросплав соответственно при Т > 1400?°С и Т > 1700?°С. Увеличение количества углерода от 20 до 45?% от массы базальта при 2000?°С приводит к возрастанию степени перехода кальция в CaC2 от 1,3 до 54,7, кремния в ферросплав от 59,3 до 85,6?%, а Al в сплав при 2100?°С от 18,2 до 84,9?% в соответствии с уравнениями. ?Ca(CaC2) = –45,202 + 2,1953?У, ?Si(сплав) = 9,0307 + 3,1832?У – 0,033?У2, ?Al(сплав) = –166,45 + 12,057?У – 0,1436?У2. При 45?% углерода и 2000?°С от базальта формируемый ферросплав, содержащий 43,6 Si и 14,4?%Al, соответствует комплексному ферросплаву марки ФС45А15 карбид кальция соответствует 1 и 2 сорту, литражом 264,5 л/кг.

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