青藏高原南北向地堑系的实验研究

MECHANISM OF N-S TRENDING GRABEN SYSTEM IN THE QINGHAI-TIBETAN PLATEAU

青藏高原南北向正断层及与其伴生的地堑是当前的热门话题。对其成因的认识分歧颇大 ,它们与高原隆升的关系则还处于推论阶段。本文用模拟实验的方法检验了其中的主要观点 ,结果表明 :南北向正断层及与其伴生的地堑是南北向挤压的结果 ,是在挤压中期横张裂隙的基础上发展起来的。因此 ,它不代表高原已抬升到了最大高度后的塌陷 ,而是伴随高原隆升过程中的产物。

This paper dealt with the mechanism of N S trending graben system in the Qinghai Tibetan Plateau. Three experiments were conducted for E W extension, and one compressive experiment was aimed to model the deformation mechanism when the Indian continent moved northwards and collided the Eurasia plate. Our modelling experiments showed that the N S trending normal faults and associated graben systems might result from the cross tensile fracture under the N S compression, instead of from E W extension. The N S trending normal faults and associated graben system took their shape from, at least, the early Miocene, and mainly in an interval time of 14～8 Ma ago. Therefore, they were not the mark of collapse when the plateau was uplifted to the highest altitude. The E W striking normal faults and related graben system did not occur until the middle late Quaternary, most of them being active at present, which should be a product of the N S compressional stress field created by collision between the India and Eurasia plates.