TECTONIC CYCLES AND PETROLEUM EXPLORATION POTENTIAL IN THE EAST QINLING AND DABIE OROGENIC BELT

The basin groups in both sides of the East Qinling and Dabie Orogenic Belt have experienced 5 different tectonic cycles since the Mesoproterozoic.After Zhongtiao(Luliang)Movement,the Jiliao,Yushaan and Xuhuai Aulacogens were formed in North China.With brokenness of the Rodinia ancient continent after the Jinning Movement,the Qinling-Dabie ocean,which was a part of the Tethyan ocean for a time,was gradually developed and the margin of the Yangtze Craton and North China Craton had gone through the evolution from continental rift to passive continental margin.The alternative pattern of subduction-collision mountain system and convergent basins was developed due to transferring of extend system to convergent system after the middle Caledonian movement(the Middle Ordovician).In the late Caledonian or early Hercynian,the early detached continental blocks were combined together again.And the alternative graben-horst pattern was presented in the Devonian.Some small scales of rift groups were developed in the southern side of the orogenic belt in the Late Permian and it was changed to convergent system after the Middle and Late Triassic Indosinian Movement.They went through the collection,collision and compression process,which was maximized in the Yanshanian period of the end of the Jurassic.Since the Cretaceous,basin groups with domination of intracontinental extension-strike slip-weak compression were developed and then the basins were destroyed by extension or strip slip again.The multiple combination of basin prototypes was formed by 5 basinal tectonic cycles,which formed basic conditions for hydrocarbon accumulation.There were 8 sets of combination of source,re-servoir and seal in vertical section.The effective hydrocarbon kitchen and preservation,which was controlled by tectonic evolution and thermal system,was the critical factors for hydrocarbon accumulation.There are favorable potential for petroleum exploration of basins in both sides of the orogenic belt.Besides the Cenozoic Nanxiang and Jianghan oil producing basins,the potential regions include the Late Paleozoic to Early Mesozoic Louyu residual basin,the Taikang residual basin,the Zhoukou superimposed composite basin and Xinyang composite basin in the northern side,the deep seated Paleozoic in the Nanxiang basin of internal orogenic belt,and the pre-Tertiary Jianghan composite basin,the Paleozoic Yichang-Dangyang reformed residual basin,the shadow basins under the southeastern Hubei thrust belt and the Dahongshan thrust belt respectively,in the southern side of the orogenic belt.