NEW PROGRESS IN THE STUDY OF THE REGIONAL GEOLOGY OF HUNAN

This paper briefly elucidates the main fruitful results and understandings gained in the study of the regional geology of Hunan province in the past thirty years and presents the current research level of basic geology and geological sciences. In the aspect of stratigraphy, the paper gives a summary of four major stages of deposition and their general regularities, and introduces the significant advances in the study of the stratigraphic paleontology in the Yangtze and South China regions and the transional region between them （which are stratigraphically of nationwide order）. In the aspect of magmatic rocks, six magmatic periods are established: Wulingian, Xuefengian, Caledoni- an, Indosinian, Yanshanian and Himalayan, and it is pointed out that all the intrusions are characterized by composite intrusions and contemporaneous polyphase and multiple intrusions. According to the sources of rock-forming material, granites in Hunan may be divided into two genetic types, the crust- derived anatectic type and the crust-mantle-derived transitional type. The paper summarizes the evolutionary regularity of the composite intrusions and contemporaneous multiple intrusions. The spatial and temporal distribution of the magmatic activity has a general tendency of southeast-directed migration. A comparison is made between the main characteristics of the two types of granite. In the aspect of geological structures, it is pointed out that the deve- lopment of the regional geological structures in Hunan progressed through three phases: the pre-Devonian activity, late Paleozoic stability and Meso- Cenozoic substability. The paper discusses the mode and direction of the cru- stal movements in Hunan, which are dominated by N-Sand E-Wdirected compression or shear. The crustal movements are characterized by nonisotasy, migration of the continental-crustal evolution and superposition of structures that occurred since the Mesozoic. Besides, the paper also analyses the impo- rtant controlling effect of the Jiangnania on the process of development of the geological structures of Hunan, and discusses the controlling effect of the crustal movements and major structural systems on rock and ore formation, earthquakes and geotherms.