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A. D. Nozhkin I. I. Likhanov T. B. Bayanova P. A. Serov 《Geochemistry International》2017,55(9):792-801
Late Vendian (540–550 Ma) U–Pb age was established for zircon from postcollisional granites of the Osinovsky Massif located among island-arc complexes of the Isakovka terrane in the northwestern Sayan–Yenisei accretionary belt. The granites were formed 150 Ma after the formation of the host island-arc complexes and 50–60 Ma after the beginning of their accretion to the Siberian Craton. These events mark the final stage of the Neoproterozoic history of the Yenisei Ridge related to the end of accretion of oceanic fragments and the beginning of the Caledonian Orogeny. The granites are subalkaline leucoractic Na–K rocks enriched in Rb, U, and Th. The petrogeochemical and Sm–Nd isotope data (TNd(DM)-2st = 1490–1650 Ma and εNd(T) from–2.5 to–4.4) indicate that their source was highly differentiated continental crust of the SW margin of the Siberian Craton. Therefore, the host Late Riphean island-arc complexes were thrust over the craton margin for distance significantly exceeding the size of the Osinovsky Massif. 相似文献
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A. D. Nozhkin I. I. Likhanov V. V. Reverdatto T. B. Bayanova S. V. Zinoviev P. S. Kozlov N. V. Popov N. V. Dmitrieva 《Doklady Earth Sciences》2017,474(2):674-679
The Late Vendian (540–550 Ma) U–Pb zircon age of postcollisional granitoids in the Osinovka Massif was obtained for the first time. The Osinovka Massif is located in rocks of the island-arc complex of the Isakovka Terrane, in the northwestern part of the Sayany–Yenisei accretion belt. These events stand for the final stage of the Neoproterozoic history of the Yenisei Ridge, related to the completing accretion of the oceanic crust fragments and the beginning of the Caledonian orogenesis. The petrogeochemical composition and the Sm–Nd isotopic characteristics support the fact that the granitoid melt originated from a highly differentiated continental crust of the southwestern margin of the Siberian Craton. Hence, the granite-bearing Late Riphean island-arc complexes were thrust over the craton margin at a distance considerably exceeding the dimensions of the Osinovka Massif. 相似文献
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I.I. Likhanov V.V. Reverdatto P.S. Kozlov N.V. Popov 《Russian Geology and Geophysics》2009,50(12):1034-1051
Four Precambrian metamorphic complexes in the vicinity of regional faults in the Transangarian region of the Yenisei Ridge were examined. Based on geothermobarometry and P-T path calculations, our geological and petrological studies showed that the Neoproterozoic medium-pressure metamorphism of the kyanite–sillimanite type overprinted regionally metamorphosed low-pressure andalusite-bearing rocks at about 850 Ma. A positive correlation between rock ages and P-T estimates for the kyanite-sillimanite metamorphism provide evidence of the regional structural and tectonic heterogeneity. The medium-pressure metamorphism was characterized by (1) the development of deformational structures and textures, and kyanite-bearing blastocataclasites (blastomylonites) with sillimanite, garnet, and staurolite after andalusite-bearing regional metamorphic rocks; (2) insignificant apparent thickness of the zone of medium-pressure zonal metamorphism (from 2.5 to 7 km), which was localized in the vicinity of the overthrusts; (3) a low metamorphic field gradient during metamorphism (from 1–7 to 12 °C/km); and (4) a gradual increase in lithostatic pressure towards the thrust faults. These specific features are typical of collisional metamorphism during overthrusting of continental blocks and are evidence for near-isothermal loading. This event was justified within the framework of the crustal tectonic thickening model via rapid overthrusting and subsequent rapid uplifting and erosion. The results obtained allowed us to consider medium-pressure kyanite-bearing metapelites as a product of collision metamorphism, formed either by unidirectional thrusting of rock blocks from Siberian craton onto the Yenisei Ridge in the zones of regional faults (Angara, Mayakon, and Chapa areas) or by opposite movements in the zone of splay faults of higher orders (Garevka area). 相似文献
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Three complexes in the zones of the Ishimbinskii and Tatarka deep faults in the Transangarian part of the Yenisei Range were studied to reproduce their metamorphic evolution and elucidate distinctive features of regional geodynamic processes. The results of our geological and petrological studies with the application of geothermobarometry and P-T metamorphic paths indicate that the Neoproterozoic kyanite-sillimanite intermediate-pressure metamorphism overprinted regionally metamorphosed rocks of low pressure of Middle Riphean age. The kyanite-sillimanite metamorphism was characterized by (1) the development of deformational structures and textures and kyanite-bearing blastomylonites with sillimanite, garnet, and staurolite after andalusite-bearing regional-metamorphic mineral assemblages; (2) insignificant apparent thickness of the zone of intermediate-pressure zonal metamorphism (from 2.5 to 7 km), which was localized near overthrusts; (3) a low geothermal gradient during metamorphism (from 1–7 to 12°C/km); and (4) a gradual increase in the total metamorphic pressure from southwest to northeast with approaching the overthrusts. These features are typical of collisional metamorphism during the thrusting of continental blocks and testify that the rocks subsided nearly isothermally. The process is justified within the scope of a model for the tectonic thickening of the crust via rapid thrusting and subsequent rapid exhumation and erosion. The analysis of our results with regard for the northeastern dips of the thrusts allowed us to consider the intermediate-pressure metapelites as products of collision metamorphism, which were formed in the process of a single thrusting of ancient rock blocks from the Siberian Platform onto the Yenisei Range. 相似文献
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I. I. Likhanov A. A. Ten V. A. Ananiev V. V. Reverdatto I. Memmi 《Mineralogy and Petrology》2001,71(1-2):51-65
Summary A new approach for deriving kinetic parameters of diffusion-controlled metamorphic reactions is described. It is based on
comparison of models of temperature field evolution near a cylindrical intrusion and observable chemical changes in biotite
at the contact aureole of the Kharlovo massif. Unlike other methods used to construct quantitative models of reactions which
produce distinctly expressed zoned microtextures, the proposed approach allows better understanding of the processes occurring
in texture-homogeneous rocks, where complete consumption of some reactant mineral phases prevent accurate reconstruction of
the metamorphic process. The calculations yielded estimates of the effective rates of metamorphic reactions (10−12 s−1) and the effective diffusion coefficient (5.29 × 10−16 cm2 s−1). These values are consistent with experimentally and theoretically derived estimates of solid-state diffusion, including
grain-boundary diffusion.
Received July 14, 1998; revised version accepted June 28, 2000 相似文献
Zusammenfassung Inverse Modellierung zur Bestimmung kinetischer Parameter diffusionskontrollierter metamorpher Reaktionen in der Kontaktaureole von Kharlovo (Südsibirien, Ru?land) Ein neuer Ansatz zur Herleitung kinetischer Parameter diffusionskontrollierter metamorpher Reaktionen wird beschrieben. Er basiert auf einem Vergleich der Modelle für die Temperaturentwicklung um eine zylindrische Intrusion mit beobachtbaren ?nderungen im Chemismus von Biotit in der Kontaktaureole des Kharlovo Massivs. Im Unterschied zu anderen Methoden, die quantitative Modelle von Reaktionen mit deutlich zonierten Mikrotexturen verwenden, erlaubt dieser Ansatz ein besseres Verst?ndnis der Prozesse in texturell homogenen Gesteinen, in denen die vollst?ndige Reaktion einiger Reaktanden (Mineralphasen) sonst die Rekonstruktion des Metamorphoseprozesses verhindert. Die Berechnungen erlauben eine Absch?tzung der metamorphen Reaktionsraten und des effektiven Diffusionskoeffizienten . Diese Werte sind mit experimentell und theoretisch ermittelten Werten der Diffusion in Festk?rpern, einschlie?lich der Diffusion entlang von Korngrenzen, konsistent.
Received July 14, 1998; revised version accepted June 28, 2000 相似文献
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I. I. Likhanov P. S. Kozlov V. V. Reverdatto N. V. Popov 《Doklady Earth Sciences》2018,480(1):568-572
Petrogeochemical and geochronological study of boudined quartzite sandstones and tonalites, as well as host amphibolites, in the shear zone showed that potential sources of detrital zircons were Neoarchean–Paleoproterozoic rocks of the Angara–Kan block and products of their metamorphism. Interpretation of the available data does not confirm the inferred presence of the Early Precambrian basement of the Siberian Craton in the Transangara region. 相似文献