Geological relationship between Anyui Metamorphic Complex and Samarka terrane,Far East Russia |
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| Authors: | Satoru Kojima Kazuhiro Tsukada Shigeru Otoh Satoshi Yamakita Masayuki Ehiro Cheikhna Dia Galina Leontievna Kirillova Vladimir Akimovich Dymovich Lyudmila Petrovna Eichwald |
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| Institution: | 1. Department of Civil Engineering, Gifu University, Gifu 501‐1193, Japan (email: skojima@gifu‐u.ac.jp),;2. Nagoya University Museum, Nagoya 464‐8601, Japan,;3. Graduate School of Science and Engineering, University of Toyama, Toyama 930‐8555, Japan,;4. Department of Geology, Faculty of Education and Culture, Miyazaki University, Miyazaki 889‐2192, Japan,;5. The Tohoku University Museum, Sendai 980‐8578, Japan,;6. Institute of Tectonics and Geophysics, Far Eastern Branch of the Russian Academy of Sciences, Khabarovsk 680063, Russia, and;7. State Enterprise Dalgeophysics, Khabarovsk 680000, Russia |
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| Abstract: | The Anyui Metamorphic Complex (AMC) of Cretaceous age is composed of metachert, schist, gneiss, migmatite and ultramafic rocks, and forms a dome structure within the northernmost part of the Jurassic accretionary complex of the Samarka terrane. The two adjacent geological units are bounded by a fault, but the gradual changes of grain size and crystallinity index of quartz in chert and metachert of the Samarka terrane and the AMC, together with the gradual lithological change, indicate that at least parts of the AMC are metamorphic equivalents of the Samarka rocks. Radiolarian fossils from siliceous mudstone of the Samarka terrane indicates Tithonian age (uppermost Jurassic), and hence, form a slightly later accretion. This signifies that the accretionary complex in the study area is one of the youngest tectonostratigraphic units of the Samarka terrane. The relationship between the Samarka terrane and AMC, as well as their ages and lithologies, are similar to those of the Tamba–Mino–Ashio terrane and Ryoke Metamorphic Complex in southwest Japan. In both areas the lower (younger) part of the Jurassic accretionary complexes were intruded and metamorphosed by Late Cretaceous granitic magma. Crustal development of the Pacific‐type orogen has been achieved by the cycle of: (i) accretion of oceanic materials and turbidites derived from the continent; and (ii) granitic intrusion by the next subduction and accretion events, accompanied by formation of high T/P metamorphic complexes. |
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| Keywords: | Anyui Metamorphic Complex crystallinity index Jurassic accretionary complex low‐grade metamorphism radiolaria Samarka terrane Sikhote– Alin |
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