青藏高原西部日土-普兰一带古构造应力值的估算

本文用超显微构造的位错密度法,估算了该地区6次构造事件的古构造应力值。尽管从现在的构造形变特征来看,不同构造事件都是沿近南北方向的伸展或挤压,但其形变强度各不相同,印支运动（晚三叠世）最强,平均差应力值达201MPa,四川运动（白垩纪—早第三纪早期）次之,为183MPa,其它各次构造运动均较弱,阿森特运动（前寒武纪末期）为101MPa,海西运动（早二叠世晚期）为121MPa,燕山运动（晚侏罗世）为130Mpa,喜马拉雅运动（中新世末期以来）为110MPa,加里东运动在本区大部分地方较弱,我们未采集到能反映其构造应力状态的样品。

ESTIMATIONS OF PALEOTECTONIC STRESS MAGNITUDE IN RUTOG-BURANG AREA, WESTERN XIZANG-QINGHAI PLATEAU, CHINA

By using the dislocation density method of microstruc-tures, the paleotectonic stress magnitudes of 6 tectonic events were estimated in western Ngan area. Although different tectonic events manifest themselves as extension or compression along north-south direction from the structure characteristics, the strength of their deformations are obviously variable. In late Triassic (Indo-sinian movement), the tectonic strength is most violent, the average differential stress magnitude is 204 MPa; in Cretaceous-early Eogene (Sichuan movement, it becomes smaller, the average differential stress magnitude is 183 MPa: and others are rather weak, in the end of Pre-Cambrian (Assyntian orogeny), is 101 MPa; in late Permian (Hercynian orogeny), is 121 MPa; in late Jurassic (Yansha-nian movement),is 130 MPa;and since late Miocene (Himalayan orogeny) , is no MPa. As to the Caledonian cycle (Cambrian-Silurian), the orogeny was rather weak in the most parts of this area. Owing to we have not collected samples to reflect its tectonic stress state, so we could not estimate its differential stress magnitude. Depending on the above data, we find that the dislocation density method is suitable to estimate the tectonic stress magnitude in regions, and in general, the dislocations are not superposed.