天山—阿尔泰地区古生代构造成矿作用

Paleozoic tectono-metallogeny in Tianshan-Altay area,Central Asia

天山—阿尔泰地区古生代大地构造及其相关的内生金属成矿作用是一个重要而又有趣的研究课题。阿尔泰地区属于早古生代碰撞带,天山地区属于晚古生代早期（晚泥盆世—早石炭世,385～323 Ma）碰撞带,均为区域性近南北向（按现代磁方位）缩短-碰撞作用的结果。在晚泥盆世—早石炭世碰撞作用下,阿尔泰地区近NW向区域性断层呈现为右行走滑的特征,天山地区近东西向的区域性断层表现为逆断层的活动。然而,在晚石炭世—二叠纪（323～260 Ma）受乌拉尔碰撞带向东挤压作用的远程效应影响,该地区受到较弱的向东挤压作用,阿尔泰地区NW向断层转变成左行走滑断层,天山地区近东西向的断层则转为右行走滑断层,使该区岩石发生适度的破碎,以致在天山—阿尔泰地区形成大量世界著名的大型内生金属矿床。对于亚洲大陆来说,碰撞作用最强烈的时期并不一定是内生金属成矿作用最有利的阶段。应该审慎地对待＂造山带成矿＂假说。

Paleozoic tectonics and endogenic metallogeny in Tianshan-Altay area of Central Asia constitute an important research topic in geology. The Altay area, as a collision zone of the Early Paleozoic（500-397 Ma）, and the Tianshan region, as a collision zone of the early period in Late Paleozoic（Late Devonian- Early Carboniferous, 385-323 Ma）, resulted from nearly NS-trending shortening and collision（according to recent magnetic orientation）. In the Late Devonian- Early Carboniferous（385- 323 Ma）,regional NW- trending faults exhibited features of the dextral strike- slip motion in Altay area and Junggar basin. In the Tianshan area, however, nearly EW- trending regional faults caused motions of the thrusts, thus belonging to the collision period of the Tianshan Mountains. However, in the Late Carboniferous- Permian（323- 260 Ma）, these areas suffered from weaker eastward compression, influenced by the long- distance effect of the Ural collision zone, which converted existent NW- trending faults into sinistral strike- slip in Altay and Junggar areas, and also converted existent nearly EW- trending faults into dextral strike- slip in Tianshan area. The rocks of that area in the Late Carboniferous- Permian period were moderately ruptured into a certain tension-shear form, thus forming a number of world-famous giant endogenic metal ore deposits in Tianshan-Altay area. As to the Central Asian continent, the most powerful collision period may not coincide with the most favorable endogenic metallogenic period.Therefore the＂orogenic metallogeny hypothesis＂should be treated with caution in that area.