THE ACTIVITIES OF MANTLE HEAT SOURCE AND LANDMASS DRIFT IN THE SOUTH CHINA AREA

Ring structures of various grades spread widely in the South China area.It is an important intra-plate structure type resulted from the action of mantle heat source on lithosphere since Mesozoic.The second grade ring appeared as four NW-trend ring-chains.The formation time was successively later and later,as moving toward SE.The author tries to explain this phenomena by landmass drift on a fixed heat source settled in mantle.The idea is set up according to the relative movement of mantle heat source (thermal plume) towards SE as the lithosphere (landmass) drifts oppositely above it.It is inferred that South China Landmass drifted a distance of about 600km towards NW during middle-late stage of Mesozoic (190-90 m.y.B.C.) with a speed of 6 km per m.y.Based on the comprehensive analysis of paleomagnetism,paleontology,paleoclimate and track of the mantle heat source,it is indicated that South China Landmass have drifted toward NW in period of Ceno-Mesozic.At Late Permian period (240 m.y.B.C.),it was located in the vicinity Of equator,in the present ocean area between New Guinea and Garoling Islands of SW Pacific.In Late Mesozoic (about 110 m.y.B.C),South China Landmass drifted northwestwards to 14?-24皀orth latitude of the present Philippine Sea Basin.During 190-25 m.y.B.C.,the diift speeded up gradually,varying from 0.6 to 3.8 cm/yr.