U-PB AGES OF DETRITAL ZIRCONS FROM KOREAN FOLD-THRUST BELTS: IMPLICATIONS FOR THE PALEOZOIC CRUSTAL ARCHITECTURE OF EAST ASIA

Detrital zircons in eight (meta)sandstones of the Taebaeksan Basin, Ogcheon Metamorphic Belt, and Imjingang Belt, Korea, were analyzed using a sensitive high-resolution ion microprobe (SHRIMP), to provide geochronologic constraints for relationships among various tectonic provinces. These samples yielded a spectrum of U-Pb ages ranging from Archean to Paleozoic; distribution patterns permit us to subdivide them into two groups correlative with the North China craton (NCC) and the Qinling Belt, China, respectively. Five sandstones from the Taebaeksan Basin show distinct peaks at ~1.87 and 2.5 Ga without any Meso- or Neoproterozoic ages. This pattern is characteristic of the NCC, corroborating previously published fossil evidence. The youngest zircon populations define Paleozoic magmatic events that occurred intermittently along the periphery of the NCC. In contrast, metasandstones of the Ogcheon Metamorphic Belt and the Imjingang Belt yielded identical age-probability patterns typified by major populations at ~950 and 440 Ma, constraining the maximum age of deposition as Silurian. These results suggest that the Imjingang Belt is continuous with the Ogcheon Metamorphic Belt across the Gyeonggi Massif. The marked contrast in age distributions suggests a suture between the Taebaeksan Basin and the Ogcheon Metamorphic Belt, and is accounted for by a tectonic model where the Gyeonggi Massif is a microcontinent similar to the northern Qinling Belt. Clearly, the microcontinental strip comprising the Qinling-Dabie-Sulu Belt extends through the Korean Peninsula along the southern margin of the NCC.