Tectonic evolution and control of coal in Donghai Xihu sag

Xihu sag is a Cenozoic back-arc basin which experienced multi-episodic tectonic setting. Based on the analysis of characteristics of regional structure and its internal structure, on the basis of using balanced section technique, the tectonic evolution characteristics of Xihu sag and control of coal were discussed. The results showed that Xihu sag has the structure of "Zonation in latitudinal direction and blocking in longitudinal direction" pattern. Under the control of the regional evolution, Xihu sag tectonic evolution can be divided into fault depression stage, depression stage and regional subsidence stage. Coal accumulating effect before the flat terrain, coal accumulating period of development of syndepositional structural slope-break zone and coal accumulating a series of inversion structures, which formed the current CBM regularity of Xihu sag.