1. Exploration and Development ��esearch Institute of Daqing Oilfield��Daqing 163712��Heilongjiang��China; 2. Exploration Division of Daqing Oilfield��Daqing 163712��Heilongjiang��China

The authors pointed out that Cretaceous volcanic activities were controlled by the basement faults and secondary faults in Xujiaweizi��and formed three NNW �� trend volcanic rock belts controlled by basement faults��through the study on the relationship among fracture combination��volcanic mechanism and karst channels�� Due to the different characteristics of the basement faults��the volcanic rock belts had three eruption characteristics: center��fracture��and compound in type�� The careful dissection of Xujiaweizi fault depression in Anda area showed that: the NWW �� trend echelon fractures developed in upper basement fractures and communicated the basement faults downward��which were the volcanic magma invasion routes in western area�� These phenomenon reflected the volcanic activity stronger in the west than in the east in the history period��i. e�� the volcanic scale was larger in the west��charactered by burst facies��while showed effusive facies in the east�� The distribution of volcanic rocks were controlled by basement faults and secondary faults��which also played a remolding part to fracture trace��