BASIC CHARACTERISTICS OF CRUSTAL EVOLUTION IN HAINAN ISLAND,CHINA

This paper analysis asedimentary and magmatic formations, metamorphism and structural feature in Hainan Island using the historic analysis method. The crustal evolution of the area can be divided into four stages, pre-geosynclinal, geosynclinal, platform and diwa; Classifying genetically related structures using the dy- namic analysis method, the author points out that there are four kinds of tectonic systems: NE, E, NNE and N-trending, and ring structure. Dealing with the crustal evolution and the vicissitudes of the tectonic framework in Hainan Island using the synthetic analysis method, the following conclusions can be drawn: the pre-geosynclinal stages was controlled by an NE-trending tectonic system, on which an E-trending tectonic system was superimposed during the geosynclinal stage. In the maximum-mobility period of diwa stage, an NNE-trending tectonic system was superimposed on the E-trending tectonic systen and resulted in compounding. In the maximum-mobility period of diwa stage, the NNE-and E-trendind tectonic systems producted a joint ring structure, on which an E-and an N-trending tectonic systems were superimposed in the residual-mobility period of diwa stage. During the long, complicated and multistage crustal evolution, Hainan Island has alternately experienced left-lateral and right-lateral shear movements. Finally, the Hainan ring block was formed.