攀西及邻区印支-燕山期地块构造运动的古地磁考证

为研究四川攀西（攀枝花-西昌）地区大陆演化,在该区及邻区采集了中生代岩石标本。用热退磁和交变场退磁方法对59个采点的619块样品做了磁清洗处理。古地磁结果满足褶皱检验,对精度参数K小于10的采点或有后期重磁化的样品未纳入统计处理。 古地磁结果表明,攀西断隆、凉山断陷、断凹属扬子地块的西缘,早三叠世时位于北纬13°左右,至今北移了千余公里,上三叠纪后北移速度明显减慢;其西邻盐源断陷自早三叠世以来南移数百公里,无论古纬度或古方位与东邻地块的结果有较明显差异。

PALEOMAGNETIC STUDY ON THE TECTONIC MOTION OF PAN-XI BLOCK AND ADJACENT AREA DURING YINZHI-YANSHAN PERIOD

In order to study the evolution of the continent in Pan-Xi （Panzhihua-Xichang） area, some Mesozoic rock samples have been collected. We have carried out magnetic cleaning for 619 specimens from 59 sites by A. F and thermal demagnetization. The fold test showed that remanent magnetization of samples collected for this work are stable. Those with precision parameter K less than 10, or with remagnetization have rejected.The paleomagnetic results indicate that Pan-Xi fault-uplift, Liangshan fault-depression （Fig. 1） belong to the west edge of Yangtze block. They located 13° or so （north latitude） in early-Triassic period. Up to now they have moved northerly about one thousand km and the motion has systematically slowed down since late-Triassic Era. Yanyuan fault-depression has moved southerly about hundreds km since early-Triassic Era, the paleolatitude and paleo-orien-tation were systematically different from those in eastern adjacent block.