湘中地区造山运动期后的拉伸作用

A TENSLIE ACTION AFTER THE OROGENY PERIOD IN THE CENTRAL HUNAN AREA

The central Hunan area has undergone four orogeny ecycles of broad scope since the protereozoic Era,i.e.Xuefongian,Caledonian,Indosinian and Yanshanian orogeny cycle. The tensile action after the Indosinian cycle is especially obvious.This mechjanical trans- formation of the dip-slip fault from compressive to tensile and from inverse to normal slid- ing as well as the layer-slip extensinal tectonics of the superimposed basin in Lianyuan have been now well recognized in the connection zone betwen the mountains and basins. Specifically they occur in some complex structural phenomena which indicate the fore-nappes,the after-glidings,and the comperssion-extension in the same moving system.The transformation of the mechanical nature of the dip-slip fault may be attri- buted to the changes of the regional,adjustable,and local structral stress fields.