古深断裂活化与燕山期陆内造山运动——以川南—滇东和中扬子褶皱-冲断系为例

REJUVENATION OF FOSSIL DEEP FRACTURES AND RELATED YANSHANIAN INTRACONTIN ENTAL OROGENICS:EXAMPLES FROM SOUTH SICHUAN-EAST YUNNAN AND MIDDLE YANGTZE AREAS

基于花岗岩侵入、构造变形和磨拉石建造(或长期隆起)提出川南—滇东和中扬子地区侏罗-白垩纪时发生造山事件。分析了造山带的内部结构、范围和动力机制,发现川南—滇东褶皱-冲断系为北东向及近南北向断裂控制发育,其西以滇中古陆块与燕山期消减型造山带相隔;中扬子褶皱-冲断系为北西向断裂控制发育,向南西扩展时止于黄陵古陆核。两者均属印支运动后出现的中国—东南亚次大陆外侧的新特提斯洋消减,及嗣后的碰撞激活拼合大陆内的古深断裂活化而发生的燕山期陆内造山运动,构成中国大地构造演化的一个显著特色。

The China—SE Asia subcontinent was created by a malgamation of some micro-continents in the Indosinian orogen y,which was surrounded by the Neotethyan oceans.The Juro -Cretaceous tectono-magmatis m resulted from rejuvenation of inte rior fossil sutures or deep fractures caused by the Neotethyan s ubduction and followed collision events outside the sub-continent.In this paper,the South S ichuan—East Yunnan and Middle Yangtze fold-thrust systems are taken as examples for rejuvenation of fossil deep fractures a nd related Yanshanian intracontinental orogens.The Yanshanian granitism,structur al deformation and molasse formatio n(or long-termed uplifting and erosion)indicate an orogenic event in South S ichuan—East Yunnan and Middle Yangtze areas,with the sub-order units and temporal-spatial developin g of orogens being dis-cussed.It reveals that the former wa s controlled by the NE-striking as we ll as N —S-striking faults,and the thrusting expanded t owards the northwest.To the west of t he South Sichuan-East Yunnan fold-thrust system was t he Central Yunnan Massif(a lower-strain area during the Mesozoic),which separated the East Xizang(Tibet)—West Yunnan subduction-related oro gen in the west from the intracontinenta l one in the east.The Middle Yangtze f old-thrust system was controlled by the NW-striking fa ults,which intersected obliquely t he Indosinian geosuture in an elongation of NWW—W—E.The thrusting expanded towards th e southwest,and termi-nated by the Huangling Massif.