TIMING AND SPATIAL-DISTRIBUTION OF RIFTING IN CHINA

A compilation of recognized rifts in China indicates that five distinct episodes of rifting have occurred. These episodes occurred at approximately 2.3 Ga, 1.85-1.7 Ga, 1.0-0.7 Ga, 550-190 Ma, and 175 Ma to present. The timing and location of rifting has largely been a function of tectonic activity along the margins of the various Chinese paleocontinents. Some of the oldest rocks in China are found in the Sino-Korean and Tarim cratons, and most of the identified Precambrian rifts are found within or on the margins of these cratons. These cratons are viewed as the continental nucleus of China, and fold belts and microcontinents have been accreted to this nucleus through time. Much of the locus of rifting has migrated away from this nucleus as has the location of the continental margin-especially in the Paleozoic. Beginning in the Middle Mesozoic, rifting commenced along the entire eastern margin of China. Extension occurred concomitantly with subduction in a backarc setting; this is the dominant Cenozoic extensional regime in China and is still active today. To date, few Cenozoic rifts have been found in western China where most tectonism is probably a consequence of the collision between India and China, but it seems likely that more rifts will be discovered in this area as it becomes better studied.