二滩坝址F-20断层泥中方解石的热发光年龄测定

本文研究了二滩坝址玄武岩中方解石的热发光性质。这些方解石是中温热液蚀变的产物,当受到新断裂活动作用时,方解石晶体发生变形。实验表明,方解石受压力作用时,其天然热发光逐渐衰减,直至全部消失。根据这种原理,可以用二滩坝址方解石变形后积累的天然热发光测定最新断层活动的年龄。利用这种方法测得方解石受压变形事件发生在距今140.3万年和115.5万年之间。据此推断F-20老断层复活时期不晚于距今115.5万年。     

THERMOLUMINESCENCE DATING OF CALCITE IN THE GOUGE OF F-20 FAULT AT ERTAN DAM SITE

The thermoluminescence of calcite in basalt from Ertan dam site is studied in this paper. The calcite is product of mesothermal action in late Permian. The deformation of the calcite crystals occurred during neofaulting. Experimental study indicates that the natural thermoluminescence of calcite declines under the action of pressure till exhaustion. On this basis, the age of the latest fault activity can be determined by the natural thermoluminescence accumulated since deformation of the calcite from Ertan dam site. By this method, it has been obtained that the deformation event of the calcite under pressure occurred between 1.403 and 1.155m.y. ago. Based on these results, it can be inferred that the active time of F-20 fault was not later than 1.155 m.y. ago.