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111.
Doklady Earth Sciences - For the Permian–Triassic foidite and meimechite lavas of Polar Siberia, both the whole-rock petrochemistry and geochemistry and that of melt inclusions in olivine... 相似文献
112.
The Stress–Strain State of Recent Structures in the Northeastern Sector of the Russian Arctic Region
Doklady Earth Sciences - Complex research to determine the stress–strain state of the Earth’s crust and the types of seismotectonic destruction for the northeastern sector of the... 相似文献
113.
V. L. Afanas’ev M. Yu. Piotrovich Yu. N. Gnedin S. D. Buliga T. M. Natsvlishvili 《Astronomy Reports》2018,62(2):138-143
The results of spectropolarimetric observations of a number of magnetic white dwarfs obtained on the 6-m optical telescope of the Special Astrophysical Observatory are presented. The observations were carried out using the SCORPIO focal aperture-ratio reducer in a spectropolarimetric regime. Two characteristic dependences of the degree of polarization on the wavelength are observed. For one group of objects, the degree of linear polarization grows with wavelength, suggesting that the alignment of atoms and molecules in Rydberg states in the atmosphere of the white dwarf due to the action of its magnetic field influences scattering processes. The second group of objects displays an increase in the degrees of both linear and circular polarization with wavelength, providing evidence for the presence of protoplanetary disks around these magnetic white dwarfs, in which the alignment of circumstellar grains leads to the observed behavior. 相似文献
114.
E.V. Deev I.D. Zol’nikov I.V. Turova G.G. Rusanov Yu.M. Ryapolova N.N. Nevedrova S.A. Kotler 《Russian Geology and Geophysics》2018,59(4):351-362
Paleoseismological studies confirm that the Uimon basin is thrust by its northern mountain border along the active South Terekta fault. The latest motion along the fault in the 7-8th centuries AD induced an earthquake with a magnitude of Mw= 7.4-7.7 and a shaking intensity of I = 9-11 on the MSK-64 scale. The same fault generated another event (M > 7, I = 9-10), possibly, about 16 kyr ago, which triggered gravity sliding. The rockslide dammed the Uimon valley and produced a lake, where lacustrine deposition began about 14 ± 1 kyr ago, and a later M > 7 (I = 9-10) earthquake at ~ 6 ka caused the dam collapse and the lake drainage. Traces of much older earthquakes that occurred within the Uimon basin are detectable from secondary deformation structures (seismites) in soft sediments deposited during the drainage of a Late Pleistocene ice-dammed lake between 100 and 90 ka and in ~ 77 ka alluvium. The magnitude and intensity of these paleoearthquakes were at least M > 5.0-5.5 and I > 6-7. 相似文献
115.
N. G. Lyubimtseva N. S. Bortnikov S. E. Borisovsky V. Yu. Prokofiev O. V. Vikent’eva 《Geology of Ore Deposits》2018,60(2):93-120
The mineral assemblages, mode of occurrence, and chemical compositions of coexisting fahlore and sphalerite from the Darasun gold deposit have been described. Three generations of fahlore and three generations of sphalerite have been recognized. The FeS content in sphalerite coexisting with fahlore ranges from 0.8 to 9.4 mol %. The complete solid solution series Fe-tetrahedrite–Zn-tetrahedrite–Fe-tennantite–Zn-tennantite reflected in Sb/(Sb + As) and Fe/(Fe + Zn) ratios ranging from 0 to 0.97 and from 0.07 to 1.00, respectively, with a predominant negative relationship between these ratios has been identified for the first time at the deposit. Stepped, oscillatory, and combined stepped-oscillatory growth zonings within fahlore grains and heterogeneous aggregates of fahlore have been found. Fahlore is enriched in As with respect to Sb, and Zn-tetrahedrite is followed by Fe- and Zn-tennantite from early to late generation; Zn-tetrahedrite is followed by Fe-tennantite in zoned grains and overgrown rims; sphalerite crystallized at decreased temperature and sulfur fugacity. The evolution of the chemical composition of fahlores was caused by the evolving temperature, fluid salinity, and conditions of metal migration. 相似文献
116.
N.A. Gibsher A.A. Tomilenko A.M. Sazonov T.A. Bul’bak M.O. Khomenko M.A. Ryabukha E.O. Shaparenko S.A. Sil’yanov N.A. Nekrasova 《Russian Geology and Geophysics》2018,59(8):983-996
The Eldorado low-sulfide gold-quartz deposit, with gold reserves of more than 60 tons, is located in the damage zone of the Ishimba Fault in the Yenisei Ridge and is hosted by Riphean epidote-amphibolite metamorphic rocks (Sukhoi Pit Group). Orebodies occur in four roughly parallel heavily fractured zones where rocks were subject to metamorphism under stress and heat impacts. They consist of sulfide-bearing schists with veins of gray or milky-white quartz varieties. Gray quartz predominating in gold-bearing orebodies contains graphite and amorphous carbon identified by Raman spectroscopy; the contents of gold and amorphous carbon are in positive correlation. As inferred from thermobarometry, gas chromatography, gas chromatography-mass spectrometry, and Raman spectroscopy of fluid inclusions in sulfides, carbonates, and gray and white quartz, gold mineralization formed under the effect of reduced H2O-CO2-HC fluids with temperatures of 180 to 490 °C, salinity of 9 to 22 wt.% NaCl equiv, and pressures of 0.1 to 2.3 kbar. Judging by the presence of 11% mantle helium (3He) in fluid inclusions from quartz and the sulfur isotope composition (7.1-17.4‰ δ34S) of sulfides, ore-bearing fluids ascended from a mantle source along shear zones, where they “boiled”. While the fluids were ascending, the metalliferous S- and N-bearing hydrocarbon (HC) compounds they carried broke down to produce crystalline sulfides, gold, and disseminated graphite and amorphous carbon (the latter imparts the gray color to quartz). Barren veins of milky-white quartz formed from oxidized mainly aqueous fluids with a salinity of < 15 wt.% NaCl equiv at 150-350 °C. Chloride brines (> 30 wt.% NaCl equiv) at 150-260 °C impregnated the gold-bearing quartz veins and produced the lower strata of the hydrothermal-granitoid section. The gold mineralization (795-710 Ma) was roughly coeval to local high-temperature stress metamorphism (836-745 Ma) and intrusion of the Kalama multiphase complex (880-752 Ma). 相似文献
117.
D. M. Ol’shanetsky 《Russian Journal of Pacific Geology》2018,12(2):93-118
Based on the stratigraphic distribution of benthic foraminifera in the lower bathyal–abyssal sediments uncovered by boreholes drilled under the framework of the Deep Sea Drilling Project (DSDP) and Ocean Drilling Project (ODP) in the Northern and Southern Pacific, the Lower Paleogene biostratigraphic zonal scale based on deep-water benthic foraminifera is proposed. The proposed scale includes eight subdivisions: six zones and two subzones. The boundaries of the zonal subdivisions are determined by biotic events (appearance or disappearance (extinction)) of stratigraphically important taxa and are correlated to the zonal scales based on planktonic foraminifera and calcareous nanoplankton. Most of these events are considered to be subglobal. 相似文献
118.
E. N. Gramenitskii A. R. Kotel’nikov T. I. Shchekina O. V. Yakubovich V. N. Devyatova E. S. Zubkov N. I. Suk M. F. Vigasina Z. A. Kotel’nikova 《Geochemistry International》2018,56(6):521-534
Fluoro-sodalite was synthesized for the first time at temperatures of 400–800°C and H2O pressures of 1–2 kbar in the Si–Al–Na–H–O–F system. X-ray diffraction and infrared spectroscopic investigations showed that fluorine is incorporated in the sodalite structure as anionic octahedral groups, [AlF6]3–, the number of which can vary from 0 to 1. Correspondingly, the end-members of the F-sodalite series are Na7(H2O)8[Si5Al7O24] and Na8(AlF6)(H2O)4[Si7Al5O24]. Depending on the composition of the system, F-sodalite associates at 500–650°C with nepheline, albite, cryolite, and villiaumite, which are joined by analcime below 500°C and aluminosilicate melt above 650°C. Fluorine-bearing sulfate–chlorine-sodalite was found for the first time in a pegmatite sample from the Lovozero massif. The highest fraction of the fluorine end-member in natural sodalite is 0.2. The incorporation of F into the sodalite structure requires much more energy compared with Cl– and SO 4 2- , because it is accompanied by a structural rearrangement and a transition from tetrahedral Al to octahedral Al. 相似文献
119.
Paolo?A.?SossiEmail author Julie?Prytulak Hugh?St.?C.?O’Neill 《Contributions to Mineralogy and Petrology》2018,173(4):27
Vanadium has multiple oxidation states in silicate melts and minerals, a property that also promotes fractionation of its isotopes. As a result, vanadium isotopes vary during magmatic differentiation, and can be powerful indicators of redox processes at high temperatures if their partitioning behaviour can be determined. To quantify the partitioning and isotope fractionation factor of V between magnetite and melt, piston cylinder experiments were performed in which magnetite and a hydrous, haplogranitic melt were equilibrated at 800 °C and 0.5 GPa over a range of oxygen fugacities (\({f_{{{\text{O}}_{\text{2}}}}}\)), bracketing those of terrestrial magmas. Magnetite is isotopically light with respect to the coexisting melt, a tendency ascribed to the VI-fold V3+ and V4+ in magnetite, and a mixture of IV- and VI-fold V5+ and V4+ in the melt. The magnitude of the fractionation factor systematically increases with increasing log\({f_{{{\text{O}}_{\text{2}}}}}\) relative to the Fayalite–Magnetite–Quartz buffer (FMQ), from ?51Vmag-gl = ? 0.63?±?0.09‰ at FMQ ? 1 to ? 0.92?±?0.11‰ (SD) at ≈?FMQ?+?5, reflecting constant V3+/V4+ in magnetite but increasing V5+/V4+ in the melt with increasing log\({f_{{{\text{O}}_{\text{2}}}}}\). These first mineral-melt measurements of V isotope fractionation factors underline the importance of both oxidation state and co-ordination environment in controlling isotopic fractionation. The fractionation factors determined experimentally are in excellent agreement with those needed to explain natural isotope variations in magmatic suites. Furthermore, these experiments provide a useful framework in which to interpret vanadium isotope variations in natural rocks and magnetites, and may be used as a potential fingerprint the redox state of the magma from which they crystallise. 相似文献
120.
S. V. Rud’ko 《Lithology and Mineral Resources》2018,53(4):307-323
The paper presents results of the lithological study of Upper Jurassic limestones, flyschoids and limestone breccias on the southern side of the Baidar Valley in the Crimean Mountains. Study of the microfacies revealed that the limestones are represented by deposits on lagoons, platform edge shoals, reefs, and forereef aprons on the carbonate platform slope. Flyschoids include deposits in the distributive turbidite channels and hemipelagic sediments in the deep-water part of the basin. Limestone breccias were formed by gravitation flows on the carbonate platform toe-of-slope and slope. The presence of gravitation deposits in the Upper Jurassic carbonate complexes of the Crimean Mountains can testify to the primary clinoform structure of this sedimentary sequence. Comparison of the obtained sedimentological data made it possible to reconstruct the facies model of the Crimean carbonate platform and main episodes of its formation. Development of the carbonate shelf was related to two transgressive-regressive cycles. A dome-shaped reef was formed away from the coast at the initial (Oxfordian) stage. The carbonate platform was formed at the early Kimmeridgian lowstand stage when sediments were deposited in the internal part of the platform adjacent to land. In the late Kimmeridgian and early Tithonian, configuration of the carbonate platform profile resembled a distally steepened ramp, and its active progradation and shelf expansion took place in the course of transgression. Regression in the late Tithonian–early Berriasian led to regressive transformation of the ramp into platform with a flattened shallow-water shelf. Tectonic deformations at the Jurassic/Cretaceous transition promoted the formation of megabreccias on the carbonate platform foreslope. The tectonically reworked rock sequence of the “extinct” carbonate platform was overlapped transgressively by the upper Berriasian or lower Valanginian, relatively deep-water deposits of the Cretaceous platform cover. 相似文献