PRECAMBRIAN GEOLOGY OF SOUTH KOREA: RECENT DEVELOPMENTS

We review geological, metamorphic and geochronological aspects of the two major Precambrian terranes in South Korea, the Yeongnam and Gyeonggi massifs. The Precambrian rocks can be divided into the basement rocks (late Archean to Paleoproterozoic) and the unconformably overlying supracrustal rocks (Meso- to Neoproterozoic), both of which experienced multiple deformation and high-grade metamorphism. The basement rocks of the Yeongnam and Gyeonggi massifs in general show low-pressure granulite-facies peak metamorphism with clockwise isothermal decompressional P-T paths, indicated by kyanite inclusions in the peak metamorphic assemblages. The metamorphic characteristics, along with multiple deformation, suggest that the basement rocks of the two massifs may have formed in a collisional setting. Geochronological data, especially Pb-Pb garnet and U-Pb zircon ages, indicate that the basement rocks were metamorphosed during the Paleoproterozoic (1.9-1.8 Ga), following felsic magmatism (2.1-1.9 Ga) in the case of the Yeongnam massif. We note that the nature of metamorphism, and the formation and metamorphic ages for the basement rocks in the Yeongnam and Gyeonggi massifs appear to be similar to those in the Central Zone (collisional orogen) of the North China craton, suggesting a possible correlation between North China and South Korea. The supracrustal rocks in the Gyeonggi massif exhibit medium pressure amphibolite facies metamorphism with clockwise P-T paths that occurred in the Permo-Triassic, and thus share a similar Phanerozoic tectonothermal history to the rocks in the Imjingang belt, the presumed extension of the Qinling-Dabie-Sulu suture zone between the North and South China cratons. Thus, the Gyeonggi massif appears to have experienced two collisional episodes in the Paleoproterozoic and Permo-Triassic.