Tectonic Framework and Deep Structure of South China and Their Constraint to Oil‐Gas Field Distribution

Abstract

Abstract:South China could be divided into one stable craton, the Yangtze Craton (YzC), and several orogenic belts in the surrounding region, that is the Triassic Qinling‐Dabie Orogenic Belt (QDOB) in the north, the Songpan‐Garzê Orogenic Belt (SGOB) in the northwest, the Mesozoic‐Cenozoic Three‐river Orogenic Belt (TOB) in the west, the Youjiang Orogenic Belt (YOB) in the southwest, the Middle Paleozoic Huanan Orogenic Belt (HOB) in the southeast, and the Mesozoic‐Cenozoic Maritime Orogenic Belt (MOB) along the coast. Seismic tomographic images reveal that the Moho depth is deeper than 40 km and the lithosphere is about 210 km thick beneath the YzC. The SGOB is characterized by thick crust (>40 km) and thin lithosphere (<150 km). The HOB, YOB and MOB have a thin crust (<40 km) and thin lithosphere (<150 km). Terrestrial heat flow survey revealed a distribution pattern with a low heat flow region in the eastern YzC and western HOB and two high heat flow regions in the TOB and MOB respectively. Such a “high‐low‐high” heat flow distribution pattern could have resulted from Cenozoic asthenosphere upwelling. All oil‐gas fields are concentrated in the central part of the YzC. Remnant oil pools have been discovered along the southern margin of the YzC and its adjacent orogenic belts. From a viewpoint of geological and geophysical structure, regions in South China with thick lithosphere and low heat flow value, as well as weak deformation, might be the ideal region for further petroleum exploration.