阿尔金断裂不同时间尺度下的滑移速率及构造意义

阿尔金断裂是亚洲大陆最大、也是最活跃的走滑断层之一.一般认为,印度板块与欧亚大陆间的汇聚通过地壳增厚与沿阿尔金等主要深大断裂的侧向滑移2种机制被青藏高原造山带的地壳形变所吸收.由于这2种机制所预测的阿尔金断裂的左旋滑移速率相差甚巨,因此,阿尔金断裂的滑移速率成为判断2种机制相对重要性的重要依据.采用地质学、大地测量学及数值模拟方法对阿尔金断裂滑移的研究结果表明,阿尔金断裂的滑移速率呈长期减小的趋势;青藏高原经历了由块体的侧向挤出向地壳增厚的转变过程;阿尔金断裂在不同地质时间尺度下的滑移速率尚需精确确定;单纯将阿尔金断裂滑移速率的大小作为判断青藏高原构造模式的依据也是应该受到质疑的.

Slip-Rate of the Altyn Tagh Fault under Various Time-Scales and Its Tectonic Implications

The Altyn Tagh fault(ATF) is the largest,and one of the most active sliding faults in Asia.The paper suggestes that the convergence between the India and Eurasia plates is absorbed by the crustal deformation of the Tibetan orogene by two processes: distributed crustal deformation and lateral sliding along large faults.Since the estimates of the ATF slip-rate by these two competing mechanisms are quite different,the ATF slip-rate becomes an important criterion for determining the relative importance of these two mechanisms.Based on an integrated review on geological,geodetic evidence and numerical results of the slip-rate of the Altyn Tagh fault,a secular decreasing of the slip-rate of ATF is suggested,and a transition of tectonic mode of the Tibetan Plateau from block extrusion to crustal thickening is proposed.It should also be noted that the slip-rate of ATF under geological scale needs more precise determination and that the identification of tectonic mode of the Tibetan Plateau can be doubtful if it is made only by the ATF slip-rate alone.