华南大陆东部若干构造问题的思考

华南大陆的结构、属性、过程与动力学一直是地质学家关注的热点。本文以钦杭构造带东段为主要研究地区,通过精细的构造解析、变质变形研究、年代学分析,结合反射地震剖面,探讨了华南大陆东部几个科学问题。（1）江南造山带形成于新元古代华夏板块与扬子板块的“软碰撞”作用,可划分为扬子板块南缘、扬子—华夏汇聚带和华夏板块北缘3个构造单元,江南断裂带和武夷山—遂昌断裂带分别为江南造山带的北界和南界。（2）扬子—华夏板块汇聚带由多个小板块拼合而成,其间有多条缝合带,大约900 Ma开始汇聚,760 Ma全面闭合,850~780 Ma为活动高峰期,具有递变式的汇聚拼合过程,由南向北发展,先斜向俯冲,后右旋走滑,最晚集中在中部活动。（3）华南大陆东部为中生代奠定的构造格架,主要构造为一系列北东走向褶皱和逆冲断层,大量地壳范围内的叠瓦状逆冲推覆构造,由南向北逆冲,可下切到中—下地壳。（4）华南大陆燕山晚期区域性伸展构造广泛发育,存在“华南热隆”构造,震旦系内的滑覆构造典型,同期大规模岩浆活动、火山活动和大规模的热液成矿。（5）华南大陆构造演化为：850 Ma扬子—华夏板块递进式汇聚,760 Ma全面拼合,江南造山带形成;600 Ma华南大陆盖层发育;430 Ma钦杭构造带受南部构造影响;220 Ma钦杭构造带受北部远程构造影响;160 Ma逆冲推覆构造产生;140 Ma大规模伸展,构造-岩浆-成矿关系密切;随后江南持续隆升,华南强烈热隆。

A tentative discussion on some tectonic problems in the east of South China continent

The structure, properties, processes and dynamics of the south China continent have always been the focus among geologists. In this paper, the eastern part of the Qinghang tectonic belt was taken as the main research area. Based on detailed structural analysis, metamorphism and deformation research, chronology analysis and reflection seismic profile, the authors investigated several scientific problems in the eastern part of the south China continent. (1) The Jiangnan orogenic belt was formed by the "soft collision" between the Cathaysia plate and the Yangtze plate in late Proterozoic, which can be divided into three tectonic units:the southern margin of the Yangtze plate, the Yangtze-Cathaysia convergence belt and the northern margin of the Cathaysia plate. The Jiangnan fault belt and The Wuyishan-Suichang fault belt are the northern and southern boundary of the Jiangnan orogenic belt, respectively. (2) The Yangtze-Cathaysia convergence belt is composed of several small plates and suture zones. The convergence between them was progressive from south to north. It was shown as oblique subduction at first, followed by dextral strikeslipping, and the activity was concentrated in the middle at the latest. It began at about 900 Ma, reached its climax in 850~780 Ma and was closed completely at about 760 Ma. (3) The tectonic framework of the east of South China continent was established in the Mesozoic. The main structure was a series of NE-striking folds and thrust faults. A large number of imbricated thrusting nappe structures with thrusting movement from south to north originated from the middle-lower crust scale. (4) The regional extensional structures were widely developed in the east of the South China continent in late Yanshanian which led to the formation of "the South China thermal upwelling". It developed typical sliding nappe structures in the Sinian strata. The large-scale magmatic activity, volcanic activity and large-scale hydrothermal mineralization took place at the same time. (5) The tectonic evolution of the South China continent is as follows:The peak of progressive convergence between the Yangtze-Cathaysia plate took place at about 850 Ma. Plates were closed completely and the Jiangnan orogenic belt was formed at about 760 Ma. Then the development of cover of South China continent began at 600 Ma. The Qinhang tectonic belt was affected by the southern structure and the remote effect of the north structures at 430 Ma and 220 Ma, respectively. Thrust nappe structure was widely developed at 160 Ma, while widespread extensional structures was developed at 140 Ma. The tectonic-magma-mineralization had close relationship. Then the Jiangnan belt continued to uplift and the South China became a thermo-upwelling.