A discussion on the structural deformation and oil/gas traps on the western side of the Xuefeng Mountain

Detachment structures occur widely in the crust, and also constitute an important and common deformation in the area between the orogenic belt and the basin. The“comb-like” and “tough-like”fold belts on the western side of the Xuefeng Mountain result from the multi-layer detachment, and their formation is different from the typical Jura type structures. The reason is that there are several detachment layers and detachment systems in the stratigraphic column from the Neoproterozoic upwards to the Mesozoic in the study area. The structural analysis shows that every detachment system was a relatively independent deformation unit during the multi-layer detachment. In this paper, a model of multi-layer detachment in the study area is set up, and the factors controlling the development of the “comb-like” and“tough-like”fold belts are described. Because there are several detachment layers, the duplex structure is the important deformation style in the area. These are important characteristics different from the typical Jura type structures. Due to the duplex structures, most of topographical heights in the area do not correspond to the structure heights in the depth. In addition, the detachment layers may be effective tunnels for the oil/gas migration, which could shed light on the study of the hydrocarbon migration and accumulation. Based on the deformation styles and assemblages in the area, the authors hold that four types of structural traps could result from the multi-layer detachment and thrust deformation, i.e., the detachment and thrust trap, the detachment folding trap, the fault-flat blocking trap and the detachment layer trap. The potential targets for the marine petroleum exploration in the "comb-like" and "tough-like" fold belts are also discussed.