Volcanic edifice types and eruption model of Yingcheng Formation, Lower Cretaceous, in Xujiaweizi fault depression, northern Songliao Basin
松辽盆地北部徐家围子断陷下白垩统营城组火山机构类型与喷发模式研究

Volcanic hydrocarbon reservoir has already been one of the most important reservoir types in Mesozoic-Neozoic rift basin in eastern China. Volcanic rocks, mainly dacitic to rhyolitic rocks, of Yingcheng Formation in Xujiaweizi fault depression, which contain natural gas, have been the key for exploration and production, hence we must make sure volcanic edifice types and eruption model first. According to investigation, there are three types of volcanic edifices, including stratovolcano, lava dome, and caldera, in Xujiaweizi fault depression. Controlled by two phases of orthogonal and oblique extension in Xujiaweizi fault depression, there are three types of spatial patterns of volcanic edifices around the regional fault. In the footwall of fault, volcanic edifices develop; in the fault belt, there is the pattern of volcanic edifices overlapping one by one; in the hanging wall of fault, it is occupied by remarkable amount of volcanic rocks and Xudong caldera. The formation of Xudong caldera indicates that the magma chamber with low aspect ratio intruded to the bottom of crust, and then magma erupted out of the ground to form volcanic edifices. It is a center-fissure eruption model controlled by both the magma chamber and regional fault in Xujiaweizi fault depression.