TRACKING PHANEROZOIC POLYPHASE OROGENIES FROM SHRIMP U-PB DETRITAL ZIRCON AND K-AR ILLITE GEOCHRONOLOGIES: AN EXAMPLE FROM NORTHEASTERN OKCHEON BELT, KOREA

The SHRIMP U-Pb detrital zircon and K-Ar illite geochronological data from the northeastern Okcheon Belt provide clues to understand the polyphase and diachronous orogenic events overlapped in space, resulting in the present-day structural style of this area during the evolution of the Korean Peninsula. To understand these orogenies since its initial basin formation during Neoproterozoic rifting through several successive contractional orogens, here we present the SHRIMP U-Pb ages and Hf isotopic signature of detrital zircons from the Early Paleozoic sedimentary rocks. In addition, we also provide the K-Ar illite ages of fault gouge from the same area. The results show (1) the presence/absence of the Grenville-age (ca. 1.3–0.9 Ga) detrital zircons from the metasedimentary rocks, supported by Hf data, suggest their derivations from different peripheral clastic provenances at least after the Early Cambrian; (2) K-Ar illite 1M_d/1M polytype ages from the fault gouges indicate fault movements during the Late Cretaceous, Early Paleogene, and Early Miocene, while the 2M₁ illite ages provide episodes of deformation, metamorphism and hydrothermal effects related to the tectonic events during the Devonian and Permo-Triassic. These integrated geochronological data from the northeastern Okcheon Belt clearly suggest that the area preserved polyphase orogenic history from Middle Paleozoic to Early Miocene, namely the Okcheon, Songrim, Daebo orogenies and Bulguksa disturbance, reflecting the Phanerozoic tectonic evolution of the Korean Peninsula along the East Asian continental margin.