The migmatized gneiss (viz. Gwangcheon gneiss) of the southern Hongseong area, central–western Korean Peninsula underwent intermediate to high granulite-facies metamorphism (ca. 9.2–12.0 kbar and 770–870 °C) during Early Silurian to Early Devonian in age. Field and petrographic evidences from the Gwangcheon migmatite provide a clear indication of partial melting. Particularly the migmatized paragneiss is juxtaposed with arc-related doleritic metagabbro, which might be related to the heat source of the migmatization. The migmatized paragneiss has similar arc-related geochemical characteristics, such as depletions in Ta–Nb, Sr, P, and Ti and enrichments in large ion lithophile elements (LILE) caused by the partial melting effect related to the doleritic metagabbro. Sensitive high-resolution ion microprobe (SHRIMP) zircon U–Pb dating of the migmatized paragneiss yielded ages of 432 ± 6 Ma, 431 ± 10 Ma, 421 ± 3 Ma, and 403 ± 3 Ma. The U–Pb ages of inherited zircons from the migmatized paragneiss yielded an age spectra from Neoarchean to Early Paleozoic, with a dominant age population at Neoproterozoic. In contrast, new-growth and recrystallized equant zircons showed dominant concordant Early Silurian to Early Devonian ages that provide critical evidence on the timing of migmatization. These age results and the tectonic signatures are similar to those reported from the Central China Orogenic Belt in China, indicating their tectonic linkage at the northeastern margin of eastern Gondwana during Early to Middle Paleozoic in age.
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This work was supported as a Basic Research Project (GP2016-005; Tectonostratigraphy of the Mid-west Korean Peninsula and construction of the integrated geoscience information system) of the Korea Institute of Geoscience and Mineral Resources (KIGAM), funded by the Ministry of Knowledge Economy, Korea. This study is also supported partially by the Basic Science Research Program through the National Research Foundation (NRF) funded by the Ministry of Education, Science and Technology 2015R1D1A1A09058914 to S. Kwon and 2013R1A1A2058070 to H.S. Kim.
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