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Paleoproterozoic high temperature metamorphism and anatexis in the northwestern Korean Peninsula: Constraints from petrology and zircon U-Pb geochronology
Author(s): ZHAO Lei, ZHANG YanBin, WU FuYuan, LI QiuLi, YANG JongHyok, KIM JongNam, CHOI WonJong, State Key Laboratory of Lithospheric evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Institute of Geology, State Academy of Sciences
Pages: 3045-
3069
Year: 2016
Issue:
10
Journal: Acta Petrologica Sinica
Keyword: Northwestern Korean Peninsula; Paleoproterozoic; High temperature metamorphism and anatexis; Rangrim massif; North China Craton;
Abstract: The Korean Peninsula is juxtaposed by the North China Craton( NCC) to the left and the Japanese island chain to the right.Its position is of both geographical and geological importance and thus the study of its geological evolution and tectonic features will greatly stimulate the thorough understanding and interpretation of northeastern Asia geology.In this paper,we present the study results of rocks sampled from the Nampo and Jungsan groups located in the western Rangrim massif.Field as well as microscopic observations show that the studied samples from both the Nampo and Jungsan groups preserve macroscopic and microscopic evidence of anatexis,like the leucosome patches,melanosome,the thin-film structure between mineral boundaries.Mineral assemblages and reaction textures of the studied samples suggest that these rocks experienced anatexis,under both fluid present(?) and fluid absent conditions and the metamorphic grade is amphibolite to granulite facies.During later cooling and melt crystallization stage,backreaction and/or retrograde metamorphism occurred.Zircon U-Pb age results of the seven studied samples indicate episodic metamorphism and anatexis.Samples of the Nampo Group recorded an episode of metamorphism and fluid absent melting at 1917 Ma and another at 1877 ~ 1855 Ma.Melt cooling and crystallization probably occurred at 1842 Ma.Samples of the Jungsan Group give the time of anatexis( fluid present?) and garnet growth at 1841 ~ 1830 Ma and melt cooling and crystallization at 1785 Ma.This study shows that the time of the Paleoproterozoic metamorphism and anatexis in the Rangrim massif is broadly similar to those in the NCC( although there might be some difference in the patterns of metamorphism and anatexis) which,in turn,might suggest that the NCC and the Rangrim massif might have evolved into a uniform continent before Paleoproterozoic.
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