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41.
The electric and magnetic variations observed during the earthquake of March 11, 2011 that occurred in the Pacific close to the northeastern coast of Honshu Island in Japan are analyzed. The variations in the electric voltage were measured at the decommissioned submarine telecommunication cable laid on the bed of the Sea of Japan. The neighboring observatories recorded the anomalous geomagnetic variations during the studied time interval; the sources and spatial location of these anomalies are studied. The seismic signals were identified from the seismograms recorded by the broadband seismometer STS-2 at the nearest seismic station. 相似文献
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Based on the investigation of melt inclusions using electron and ion microprobe analysis, we estimated the composition, evolution, and formation conditions of magmas responsible for the calcite-bearing ijolites and carbonatites of the Belaya Zima alkaline carbonatite complex (eastern Sayan, Russia). Primary melt and coexisting crystalline inclusions were found in the nepheline and calcite of these rocks. Diopside, amphibole (?), perovskite, potassium feldspar, apatite, calcite, pyrrhotite, and titanomagnetite were identified among the crystalline inclusions. The melt inclusions in nepheline from the ijolites are completely crystallized. The crystalline daughter phases of these inclusions are diopside, phlogopite, apatite, calcite, magnetite, and cuspidine. During thermometric experiments with melt inclusions in nepheline, the complete homogenization of the inclusions was attained through the dissolution of a gas bubble at temperatures of 1120–1130°C. The chemical analysis of glasses from the homogenized melt inclusions in nepheline of the ijolites revealed significant variations in the content of components: from 36 to 48 wt % SiO2, from 9 to 21 wt % Al2O3, from 8 to 25 wt % CaO, and from 0.6 to 7 wt % MgO. All the melts show very high contents of alkalis, especially sodium. According to the results of ion microprobe analysis, the average content of water in the melts is no higher than a few tenths of a percent. The most salient feature of the melt inclusions is the extremely high content of Nb and Zr. The glasses of melt inclusions are also enriched in Ta, Th, and light rare earth elements but depleted in Ti and Hf. Primary melt inclusions in calcite from the carbonatites contain a colorless glass and daughter phlogopite, garnet, and diopside. The silicate glass from the melt inclusions in calcite of the carbonatite is chemically similar to the glasses of homogenized melt inclusions in nepheline from the ijolites. An important feature of melt inclusions in calcite of the carbonatites is the presence in the glass of carbonate globules corresponding to calcite in composition. The investigation of melt inclusions in minerals of the ijolites and carbonatites and the analysis of the alkaline and ore-bearing rocks of the Belaya Zima Massif provided evidence for the contribution of crystallization differentiation and silicate-carbonate liquid immiscibility to the formation of these rocks. Using the obtained trace-element compositions of glasses of homogenized melt inclusions and various alkaline rocks and carbonatites, we determined to a first approximation the compositions of mantle sources responsible for the formation of the rock association of the Belaya Zima alkaline-carbonatite complex. The alkaline rocks and carbonatites were derived from the depleted mantle affected by extensive metasomatism. It is supposed that carbonate melts enriched in sodium and calcium were the main agents of mantle metasomatism. 相似文献
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Lykhin D. A. Yarmolyuk V. V. Nikiforov A. V. Kozlovsky A. M. Magazina L. O. 《Geology of Ore Deposits》2018,60(6):461-485
The role of magmatic differentiation is considered for the formation of the Ulan-Tologoi Ta–Nb–Zr deposit (northwestern Mongolia) related to the eponymous alkali granite pluton. Data are presented on the structure of the pluton, the composition of its rocks, and distribution of rare metal mineralization. The ores of the pluton include alkali granites with contents of ore elements exceeding the normative threshold for Ta (>100 ppm). The rare metal mineralization includes pyrochlore, columbite, zircon, bastnaesite, monazite, and thorite, which are typical of all alkali–salic rocks; however, their amount varies depending on the REE content of the rocks. The pluton was formed ~298 Ma ago under the influence of a mantle-crustal melt source.
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V. V. Yarmolyuk D. A. Lykhin A. M. Kozlovsky A. V. Nikiforov A. V. Travin 《Petrology》2016,24(5):477-496
The Ulaan Tolgoi massif of rare-metal (Ta, Nb, and Zr) granites was formed at approximately 300Ma in the Eastern Sayan zone of rare-metal alkaline magmatism. The massif consists of alkaline salic rocks of various composition (listed in chronologic order of their emplacement): alkaline syenite → alkaline syenite pegmatite → pantellerite → alkaline granite, including ore-bearing alkaline granite, whose Ta and Nb concentrations reach significant values. The evolution of the massif ended with the emplacement of trachybasaltic andesite. The rocks of the massif show systematic enrichment in incompatible elements in the final differentiation products of the alkaline salic magmas. The differentiation processes during the early evolution of the massif occurred in an open system, with influx of melts that contained various proportions of incompatible elements. The magma system was closed during the origin of the ore-bearing granites. Rare-metal granitoids in the Eastern Sayan zone were produced by magmas formed by interaction between mantle melts (which formed the mafic dikes) with crustal material. The mantle melts likely affected the lower parts of the crust and either induced its melting, with later mixing the anatectic and mantle magmas, or assimilated crustal material and generated melts with crustal–mantle characteristics. The origin of the Eastern Sayan zone of rare-metal alkaline magmatism was related to rifting, which was triggered by interaction between the Tarim and Barguzin mantle plumes. The Eastern Sayan zone was formed in the marginal part of the Barguzin magmatic province, and rare-metal magmas in it were likely generated in relation with the activity of the Barguzin plume. 相似文献
46.
V. M. Nikiforov G. N. Shkabarnya A. Yu. Zhukovin V. B. Kaplun N. A. Palshin I. M. Varentsov Do Huy Cuong Phung Van Phach Hoang Van Vuong S. S. Starzhinsky 《Russian Journal of Pacific Geology》2016,10(6):395-407
The transverse current anomalies evident from magnetotelluric sounding (MTS) data in the transition zone from the Asian continent to the Pacific Ocean and a geoelectrical model suitable for explaining these effects are discussed. Using simulation results and new MTS data on Sakhalin and northern Vietnam, ultra-deep fluid–fault system (UDFFS) models are constructed, comprising steeply dipping low-resistivity and high-resistivity linear bodies which penetrate through the whole section of the lithosphere, continuing deep into the asthenosphere. The structure of these systems reflects the development of deep and ultra-deep fault zones, along which mantle-originated fluids may migrate through sediments to reach the surface. This allows the anisotropic–conductive fractured structures adjacent to these faults to be considered as being most favorable for hydrocarbon accumulations. 相似文献
47.
Starzhinskii S. S. Nikiforov V. M. Yoshikawa A. 《Izvestiya Physics of the Solid Earth》2020,56(2):225-237
Izvestiya, Physics of the Solid Earth - Abstract—We present the results of magnetovariational soundings at two sites (Tiksi Observatory and Kotelny Island in the Laptev Sea region of the... 相似文献
48.
Nikiforov S. L. Sorokhtin N. O. Dmitrevskiy N. N. Ananiev R. A. Sokolov S. Yu. Ambrosimov A. K. Meluzov A. A. Mutovkin A. D. 《Oceanology》2019,59(5):801-802
Oceanology - First results of the multidisciplinary expedition onboard the R/V Akademik Nikolaj Strakhov in the Barents Sea in August–September 2018 are presented. Hydrophysical sounding has... 相似文献
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Yu. A. Izrael L. I. Boltneva S. M. Vakulovskii M. V. Nikiforov 《Russian Meteorology and Hydrology》2014,39(8):507-513
Considered are the examples of the use of airborne gamma-ray spectrometry for studying the radioactive contamination of big territories and for other purposes. 相似文献