地质论评2011，Vol.57Issue(4)：480-494,15.
论大别山南缘襄樊—广济断裂的两次向南逆冲推覆
A Discussion on Two Times Southward Thrusting of Xiangfan—Guangji Fault in South Dabie Orogen, Central China
摘要
Abstract
The Xiangfan—Guangji fault (XGF) which separates the Dabie orogen belt (DOB) from the Yangtze block is the south boundary fault of the DOB. The XGF is divided into two parts by the Jianghan rift basin.The western and eastern parts of the XGF show significantly different structural features. The western XGF is characterized by typical N-dipping listric margin fault that has a thrust displacement of at least 30km, while the eastern part underwent more complex tectonic evolution. After a similar initial southward thrusting with the western part, the eastern DOB made a large-scale southwestward thrust onto the North Yangtze foreland basin along the XGF in late Jurassic. The low angular N-dipping XGF was then rebuilt by succedent northward compression from the Jiangnan uplift while the deep still shown southward thrusting features.New field structural data, 40Ar/39Ar ages, zircon LA-ICP-MS ages and sedimentology evidence indicate that the XGF have experienced twice significant southward thrusting since Middle Triassic: 40Ar/39Ar ages indicate that both the XGF and the Huwan detachment, south and north margins of the DOB respectively, were formedcontemporaneously as a result of the initial extrusion of UHP from mantle to lower crustal level during the continental—continental collision stage in Early Triassic ( about 240 ～ 231 Ma); the second apparent thrusting was in Middle—Late Jurassic (about 160 ～ 140Ma ) before the DOB' s thermal doming extension for the granitic intrusion during this period wasn' t involved into deformation. The first thrusting was characterized by inner orogen ductile, Brittle—ductile deformation accompany with exhumation of UHP terrains while the second was characterized by large-scale( thrusting distance ＞ 60km) low-angle shallow thrusting of the south margin of the DOB against above the North Yangtze foreland. During this period, extension of the north margin, large-scale thrusting of the south margin together with the contemporary sinistral strike-slip of the east margin of the DOB draw a clear tectonic framework and indicate a clockwise rotation of the eastern DOB.关键词
襄樊—广济断裂/逆冲推覆/挤出构造/大别山南缘Key words
Xiangfan—Guangji fault/ thrust/ extrusion/ South Dabie orogen引用本文复制引用
杨坤光,程万强,朱清波,李学刚..论大别山南缘襄樊—广济断裂的两次向南逆冲推覆[J].地质论评,2011,57(4):480-494,15.基金项目
本文为国家自然科学基金资助项目(编号40972137)和中石化重大基础研究项目"中国南方中上扬子大陆构造与海相油气前景"的成果. （编号40972137）
