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V.A. Makrygina L.F. Suvorova V.S. Antipin V.M. Makagon 《Russian Geology and Geophysics》2018,59(12):1626-1639
On the background of Early Paleozoic precollisional, syncollisional, and late collisional igneous rocks prevailing in the region (Khaidai and Shara-Nur granitoids and Birkhin gabbroid complex), rare-metal pegmatoid granite bodies and pegmatites along the southern edge of the Ol’khon region are of particular interest. They have a Middle Paleozoic age (390-391 Ma), cut the Caledonides, and belong to different geochemical types. The Anga unit includes amazonite-containing Li-F-B pegmatites, which are also enriched in Ta, Nb, and W. In the Ol’khon Group, only one K-feldspathic body rich in Rb, Be, Nb, W, Sn, Sc, U, and Th, with large crystals of aquamarine, has been found. The compositions of granite-pegmatite bodies and accessory rare-metal minerals have been studied. The rare-metal granite-pegmatites probably form a peripheral zone of the Hercynian within-plate setting widespread in the eastern Baikal area and related to the influence of the Siberian hot spot. 相似文献
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A. V. Travin D. S. Yudin A. G. Vladimirov S. V. Khromykh N. I. Volkova A. S. Mekhonoshin T. B. Kolotilina 《Geochemistry International》2009,47(11):1107-1124
Structural-petrologic and isotopic-geochronologic data on magmatic, metamorphic, and metasomatic rocks from the Chernorud
zone were used to reproduce the multistage history of their exhumation to upper crustal levels. The process is subdivided
into four discrete stages, which corresponded to metamorphism to the granulite facies (500–490 Ma), metamorphism to the amphibolite
facies (470–460 Ma), metamorphism to at least the epidote-amphibolite facies (440–430 Ma), and postmetamorphic events (410–400
Ma). The earliest two stages likely corresponded to the tectonic stacking of the backarc basin in response to the collision
of the Siberian continent with the Eravninskaya island arc or the Barguzin microcontinent, a process that ended with the extensive
generation of synmetamorphic granites. During the third and fourth stages, the granulites of the Chernorud nappe were successively
exposed during intense tectonic motions along large deformation zones (Primorskii fault, collision lineament, and Orso Complex).
The comparison of the histories of active thermal events for Early Caledonian folded structures in the Central Asian Foldbelt
indicates that active thermal events of equal duration are reconstructed for the following five widely spiced accretion-collision
structures: the Chernorud granulite zone in the Ol’khon territory, the Slyudyanka crystalline complex in the southwestern
Baikal area, the western Sangilen territory in southeastern Tuva, Derbinskii terrane in the Eastern Sayan, and the Bayankhongor
ophiolite zone in central Mongolia. The dates obtained by various isotopic techniques are generally consistent with the four
discrete stages identified in the Chernorud nappe, whereas the dates corresponding to the island-arc evolutionary stage were
obtained only for the western Sangilen and Bayankhongor ophiolite zone. 相似文献
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Late Quaternary geyserite and travertine in Ol’khon Area and Ol’khon Island contain a recently discovered high-temperature association of hydrocarbon and carbonaceous phases, including highly crystalline graphite, α-carbyne, and bitumen, which were produced at temperatures no lower than 400°C. A carbon modification α-carbyne, which was previously found only among experimental products, was first identified in geyserite from the Ol’khon area. Nanometer-sized morphostructures and crystallites were detected on the surface of highly crystalline graphite from the geyserite and travertine. No such structures and crystallites have ever been found on graphite of magmatic, metamorphic, metasomatic, or pneumatolytic origin. The newly formed nanometer-sized morphostructures and crystallites should be regarded as typomorphic features of carbonaceous phases in high-temperature hydrothermal rocks. Graphite was likely produced in the geyserite and travertine by low-pressure polycondenssation of hydrocarbons, at free growth in open space from oversaturated solutions and/or a gas phase. 相似文献
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T.V. Donskaya D.P. Gladkochub V.S. Fedorovsky A.M. Mazukabzov M. Cho W. Cheong J. Kim 《Russian Geology and Geophysics》2013,54(10):1205-1218
We present geological, structural, and geochemical data on synmetamorphic granitoids from the Tutai and South Ol’khon plutons of the Ol’khon terrane (Central Asian Fold Belt) with an estimation of the U–Pb zircon age of the Tutai granites. The structural and petrological data suggest the synfolding and synmetamorphic origin of the granitoids. The U–Pb zircon age of the Tutai granites (488.6 ± 8.0 Ma) almost coincides with the previously estimated age of quartz syenites from the South Ol’khon pluton (495 ± 6 Ma). The plutons occupy the same position in the regional structure. The granitoids underwent final deformations and metamorphism at 464 ± 11 Ma. The Tutai pluton consists of moderately potassic granites, whereas the South Ol’khon pluton is made up of quartz syenites and granites. The geochemical characteristics of the granites from both plutons (low Y and Yb contents, fractionated REE patterns) indicate their formation under conditions of garnet crystallization in deep crustal restite. The higher Y and Yb contents of the South Ol’khon quartz syenites as compared with those of the granites suggest the lack of equilibrium between the quartz syenite magmas and garnet parageneses during their formation or evolution. The Tutai and South Ol’khon granites were derived from quartz-feldspar crustal rocks, whereas the South Ol’khon quartz syenites might have originated from a mixed (crust-mantle) source. It is presumed that the granitoids formed within accretion-thickened crust. Early accretion, which has been first identified in the region, affected not only the Pribrezhnaya zone (the zone of the Tutai and South Ol’khon plutons) but also the entire Anga–Satyurty megazone of the Ol’khon terrane. The accretion ended with the convergence and oblique collision of the Ol’khon terrane and Siberian continent, when strike-slip tectonics became ubiquitous. 相似文献
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Kotov A. B. Skovitina T. M. Kovach V. P. Sklyarov E. V. Donskaya T. V. Lopatin D. V. Plotkina Yu. V. Tolmacheva E. V. Gorokhovskii B. M. Buchnev I. N. 《Doklady Earth Sciences》2019,484(1):45-47
Doklady Earth Sciences - Geochronological (LA–ICP–MS) U–Th–Pb studies of detrital zircon of the Late Cenozoic sand deposits on Ol’khon Island have been performed. It... 相似文献
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E. V. Sklyarov T. M. Skovitina O. A. Sklyarova A. B. Kotov E. V. Tolmacheva S. D. Velikoslavinskii 《Petrology》2014,22(6):536-546
Late Quaternary geyserites in the Ol’khon area, Baikal rift zone, are a geologically and petrologically unique rocks, which may provide information on the character of hydrothermal processes during the development of modern rift zones. The geyserites of this area are characterized by the presence of minerals atypical of such rocks: highly crystalline graphite (which is usually formed at high temperatures) and α-carbyne (which is a natural carbon modification that has been previously found only among products of experiments). Other newly formed minerals of the geyserites are equilibrium chalcedony, talc, and tremolite. This suggests that the rocks were formed under conditions significantly different from those under which classic geyserites are produced. Geyserites in the Ol’khon area were most probably produced by silica-saturated solutions rich in certain ore components (Fe, Mn, Sb, As, and Y) and heated to temperatures of about 400°C. 相似文献
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Morphology and mineralogical and geochemical compositions of freshwater ferromanganese nodules of Ol’khon Island (Sasa Formation) and Kulunda Plain (Lake Porozhnee) were studied. The study has shown rhythmic structures of the nodules, formed by macro- and microlayers with mineralized microflora. The layers are composed of either crystalline Mn mineral phases and finely dispersed Fe phases (Lake Porozhnee) or, on the contrary, crystalline goethite and X-ray amorphous Mn phases (Ol’khon Island). Separation of Mn and Fe mineral phases in the nodules proceeded during their formation and diagenesis. The freshwater nodules show both high (Lake Porozhnee) and low (Ol’khon Island) Mn/Fe ratios. The predominance of Fe phase in the Ol’khon nodules accounts for their high contents of REE, including Ce. The Porozhnee nodules grew, most likely, more rapidly, which is reflected in their low REE contents and Ce anomaly. The examined chemical and mineral compositions, textures, and structures of the nodules testify to the low-temperature hydrothermal source of their ore substance. 相似文献
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V. A. Makrygina L. F. Suvorova O. V. Zarubina N. V. Bryanskii 《Doklady Earth Sciences》2016,469(1):751-757
The first data on the geochemistry of the alkali syenite massif in Cape Budun of Ol’khon Island, where it makes contact in the south with the Khuzir gabbroid massif, are presented. Syenites occur among granite gneisses of the Sharanur dome and, like its granites, are enriched with Zr and REEs, but depleted in other trace elements. They contain anorthoclase, corundum, rare nepheline, zircon, and hercynite and are accompanied by desilicified pegmatites. Their unusual geochemical properties allow the assumption that alkaline magmas resulted from the interaction between basic and granitoid melts. 相似文献
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The classical models of adakite formation by melting of basaltic layer of oceanic lithosphere in the subduction zone were verified using geochemical and Sr–Nd isotope data on the Early Paleozoic granitoids of Eastern Sayan. The presence of adakites in fold belts is usually regarded as geochemical proxy for paleogeodynamic reconstruction. The formation of felsic derivatives with adakitic signatures in the collisional orogens is inconsistent with these models and requires their revision. It is shown that the composition of the granitoids and their evolution cannot be described with these models. In order to solve this problem, two hypotheses of granitoid formation by mixing of two geochemically contrasting reservoirs were proposed and verified. According to the first hypothesis, the granitoids represent the mixing products between alkaline olivine basalts and partial melts of the gray gneiss basement of this region. The second model relates the formation of the granitoids with melting of geochemically 2700 Ma-old enriched source in the subcontinental lithospheric mantle. In spite of differences, both these hypotheses are based on the remobilization of sources formed at the previous stages of the geological evolution of the region. In both cases, adakitic geochemical characteristics of forming felsic magmas are determined by the composition of protolith rather than by their geodynamic position. Obtained preliminary results place constraints on genetic models and geochemical reservoirs participating in the formation of the granitoids. 相似文献
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E. I. Mikheev A. G. Vladimirov V. S. Fedorovsky T. B. Bayanova A. M. Mazukabzov A. V. Travin N. I. Volkova S. V. Khromykh V. V. Khlestov P. A. Tishin 《Doklady Earth Sciences》2017,472(2):152-158
The western Baikal region (Ol’khon region, Nutgei zone, Kharikta area) is characterized by the development of packets of thrust-type folds and synkinematic granites corresponding to the stage of thrust deformations (overthrust-type granites). Two stages in the formation of thrust-type folds separated by episodes of granite emplacement are definable. The data obtained make it possible to estimate both the time of transition from thrust to strike-slip deformations and the duration of accretionary?collisional events that resulted in regional strike-slip deformations, which terminated in the western Baikal region 460?455 Ma ago. 相似文献