Early neoproterozoic supracrustal successions in the central Korean Peninsula: Implications for the paleotectonic history of East Asia

초록

The Early Neoproterozoic supracrustal metasedimentary succession from the Paju-Yangju-Dongducheon area in the central Korean Peninsula is distributed along the northwestern margin of the basement gneisses in the Middle Paleoproterozoic Gyeonggi Massif. The metasedimentary succession includes quartzite, quartz-mica schist, mica schist, calc schist, marble, and calc-silicate, showing alternating layering and large-scale isoclinal folds with Middle Paleoproterozoic gneisses. The basement gneisses yield zircon LA-MC-ICPMS U-Pb ages of 1.87-1.86 Ga. Detrital zircon U-Pb ages of eight quartzites, seven quartz-mica schists and four calc schists suggest the following features. (1) Early Neoproterozoic (ca. 0.92 Ga) sedimentation, (2) prominent age peaks in the Late Paleo-proterozoic to Mesoproterozoic range, (3) sandy proximal and muddy to calcic distal provenances, and (4) age population under extensional and trailing edge settings. The detritus of the quartzites were mainly derived from the peripheral Middle Paleoproterozoic basement. In contrast, quartz-mica schists and calc schists show detritus derived from distal Late Paleoproterozoic to Mesoproterozoic clastic sources in the southeastern North China Craton and central Korean Peninsula where magmatic rocks related to the extensional tectonics associated with the disruption of the Columbia supercontinent occur. The detrital zircon records and litho-tectonic features indicate that the Early Neoproterozoic rocks in the Paju-Yangju-Dongducheon area, as well as the central Korean Peninsula, show similarities with the southeastern North China Craton. We therefore interpret that the Early Neoproterozoic supracrustal metasedimentary successions were deposited in marginal shallow marine to fluvial environments from the marginal part of the linked central Korean Peninsula and the southeastern North China Craton which were located at the southwestern margin of western part of the Columbia supercontinent during the Early Neoproterozoic (ca. 0.92 Ga). However, metamorphic overgrowths on zircons and large-scale isoclinal folding in the alternation of the Early Neoproterozoic metasedimentary and the Middle Paleoproterozoic rocks in the Paju-Yangju-Dongducheon area are related to Late Permian to Triassic compressional collision tectonics in the central Korean Peninsula after the Early Neoproterozoic sedimentation.

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