摘要
通过变形构造几何学、岩石学和区域构造对比研究,认为阿尔金断裂西北侧的阿尔金山北缘、南缘近EW走向的蓝片岩-榴辉岩高压变质带、榴辉岩超高压变质带分别与阿尔金断裂东南侧的北祁连山、柴北缘NW—SE/NWW—SEE走向的蓝片岩-榴辉岩高压变质带、榴辉岩超高压变质带相对应,并且,高压变质带与超高压变质带的宽度和走向在断裂两侧存在较大的变化。这种在断裂带中宽度变窄、角度趋于与断裂带走向一致的变化是韧性或韧脆性走滑过程中产生的拖曳构造。因此,阿尔金断裂带走滑过程中存在较大的韧性变形,它的最大累积走滑位移量应由韧性和脆性走滑位移量组成,至少大于500km,小于1000km。另外,拖曳构造的几何特征,以及西昆仑库地北蛇绿岩、阿尔金南缘蛇绿岩和柴北缘蛇绿岩在年龄、岩石组合及地球化学特征方面均具有相似之处,暗示在早古生代时期西昆仑和阿尔金南缘、柴北缘很可能处于相同的构造背景之中,后被阿尔金断裂所切割。因此,综合得出了阿尔金断裂带最大累积左旋走滑位移量为900～1000km。
Comparative studies of the geometry and petrology of deformational structures and regional tectonics indicate that： the nearly E-W-trending blueschist-eclogite HP metamorphic belt and eclogite UHP metamorphic belt on the northern and southern margins of the Altyn Tagh Mountains at the northwest side of the Altyn Tagh Fault correspond to the NW-SE- and WNW-ESE- trending blueschist-eclogite HP metamorphic belt and eclogite UHP metamorphic belt in the North Qilian Mountains and on the northern margin of the Qaidam basin at the southeast side of the fault respectively. Moreover, the widths and strikes of the metamorphic belts vary significantly from one side of the fault to the other. The narrowing of the metamorphic belts in the fault belt and the tendency of their strikes to be parallel to that of the fault belt indicate the occurrence of drag structure in the process of ductile or ductile-brittle strike-slip motion. Therefore, there occurred fairly strong ductile deformation in the process of strike-slip motion of the Altyn Tagh Fault and its maximum cumulative strike-slip displacement should include both ductile and brittle components and should range from 500 to 1000 kin. Furthermore, the geometric features of the drag structure are similar and the North Kiida ophiolite in the West Kunlun, southern Altyn Tagh marginal ophiolite and northern Altyn Tagh marginal ophiolite have similarities in respect to the age, rock association and geochemistry, which implies that the West Kuulun and the northern and southern margins of the Altyn Tagh were very likely to lie in the same tectonic setting during the Early Paleozoic, and later they were cut by the Altyn Tagh Fault. By integrating all the above-mentioned data, we may draw the following conclusion： the maximum accumulative sinistral strike-slip displacement of the Altyn Tagh Fault may be 900-1000 km.
出处
《地质通报》
CAS
CSCD
北大核心
2007年第10期1288-1298,共11页
Geological Bulletin of China
基金
国家自然科学基金项目(编号:40272096
40572122)
中国地质调查局地质调查项目(编号:1212010611811
1212010610105)
作者简介
李海兵（1966-），博士，研究员，从事青藏高原变形构造方面的研究工作。E-mail：lihaibing06@yahoo．com．cn
