皖浙赣断裂带的界定及其基本特征

以往文献中及众多研究者所指的“皖浙赣断裂带”实际上包括了不同时代形成的、方向有变化的多组规模巨大的区域性断裂带;最早的断裂带形成于新元古代,最晚的形成于晚中生代。在地壳演化过程中,随着构造应力场的变化,不同时代的断裂带方向变化较大,新元古代晋宁期为北东向,早古生代加里东期为近东西向—北东东向,晚中生代为北北东向;每一期断裂带都有它们自己的大地构造背景和指示意义。文中认为,不同阶段形成的断裂带不能混为一谈。新元古代晋宁期的北东向断裂带南段基本上以赣东北蛇绿混杂岩带为代表,向北东延至皖南伏川断裂带,具有板块(或地体)边界断裂的性质;加里东期以近东西向祁门—歙县断裂带为代表,其西段被后期牵引成北东向,造成两侧的变质基底特征明显不同;二者均不属于皖浙赣断裂带的组成部分。而通常意义上所指的具有区域控岩控矿作用的皖浙赣断裂带,是晚中生代北北东向的赣东北—五城—歙县—绩溪—宁国断裂带,控制了侏罗—白垩纪红色盆地及燕山期岩浆岩的形成和分布,是一条具有控矿作用的重要的构造岩浆岩带。

Identification and basic characteristics of the Anhui-Zhejiang-Jiangxi fault zone

The term of 'Anhui-Zhejiang-Jiangxi fault zone’ in literature, occurred in the border region of Zhejiang,Jiangxi and Anhui provinces, which comprised several giant regional fault belts with various orientation formed at different geological ages. Among these faults, the oldest formed in the Neoproterozoic age, and the youngest in the age of the late Mesozoic. Occurrence direction of these faults was different corresponding to the tectonic stress field during geological evolution processes. These faults had been categorized into three groups: those trending in northeast in the Neoproterozoic age, trending in near west-east and/or east-northeast in the Caledonian age and trending in north-northeast in the late Mesozoic age, each group had its own geological setting and significance. However, authors of this paper think that these faults can not be grouped as one belt due their differences in ages and trending directions. The northeast trending faults in the Neoproterozoic started from northeast Jiangxi and extending northeastward to Fuchuan, Anhui Province, should be a boundary fault zone of a plate or block juncture. The near west-east or east-northeast faults in the Caledonian age, represented by Qimen-Shexian fault, were the boundary of a basement, characterized by the obvious dissimilarity of its two sides. In the authors' view, the previously named Anhui-Zhejiang-Jiangxi (Wan-Zhe-Gan) fault zone was only the north-northeast faults in the late Mesozoic age, which began in Yiyang, Northern Jiangxi and then connected with Wucheng, Shexian-Ningguo faults. These faults were a key fault-magma belt controlling the formation of Jurassic-Cretaceous red basins, ore distribution, magmatic activity and mineralization.