COOLING AGE OF DABIE OROGEN, CHINA, DETERMINED BY AR-40-AR-39 AND FISSION-TRACK TECHNIQUES

Based on Ar-40-Ar-39 results of hornblendes and biotites and fission track dating results of apatites separated from the same rock samples, cooling history of rocks from Dabie orogen is discussed. Rocks from both Southern Dabie Terrain (SDT) and Northern Dabie Terrain (DT) have an early East cooling followed by a more recent slow cooling. Rocks from SDT cooled to about 540 degrees C at about 190 Ma B.C., while rocks from NDT cooled to about 540 degrees C at 125 Ma B.C. Until about 110-120 Ma B.C., rocks from both SDT and NDT cooled to about 100 degrees C. This suggests that a relative movement among rocks from SDT, NDT and ultra-high pressure metamorphic rocks exists before 110-120 Ma B.C.