Abstract:

Five first-order ring structures,such as Hunan-Jiangxi,Guangdong,Fujian-Zhejiang,Jiangsu-Zhejiang,Sichuan-Hunan,have been revealed in south China.They might be considered as manifestations of both fossil hot spots and crustal micro-expansion centres appeared due to the effects of mantle convection or heat plumes on lithosphere in the Mesozoic.The mantle convection can cause not only a sea floor spreading,but also extention and splitting of the continental lithosphere.The arcuate structures,such as the southeast Sichuan,Bamianshan,Guangxi and Dabashan arcuate struc-tures found in the southwestern China,might be formed through horizontal compression exerted by the intracontinental micro-expansion centres during theLate Mesozoic time.In the southeastern area of Sichuan Province,the intersec-tion of different strike of folds are clearly resulted from the stress transmitted from different micro-expansion centres.The nappes located both in Mt.Xuefeng of Hunan Province and in the southern part of Jiangsu Province are also considered to be related with adjacent intracontinental expansions.The mantle hot spots indicated the above mentioned five first-order ring structures have seemingly migrated all the time southeast ward from the hinter-land towards the sea area ever since the Mesozoic.Along the trajectories oftheir migration,it seems that the supracrustal sediments might have been subjected to high temperature ranging from 200℃ to 700℃.This would be harmful to the pre-servation of hydrocarbon in Palaeozoic systems.The heat value of the western part of Mr.Xuefeng is in general lower than 200℃,and this is better for the preservation of hydrocarbon in the area,whereas in the eastern part,the conditions are different.