Study On Tectonic-Palaeogeography Evolution And Evaluation Of Exploration Right Blocks Of Continental Margin In South China Sea

Continental margin is the special geological tectonic unit between continent and ocean lithosphere ,and it is ideal arena in study of geodynamics and basin sedimentary evolution, where is also enrichment zone for hydrocarbon and other significant resources. The paper analyzed the Cenozoic basin basement characteristics in South China Sea, by comparatively studying the tectonic evolution features of global passive continental margins, such as eastern Brazil,West Africa offshore, Gulf of Mexico and north-western Australia etc, and study on tectonic-palaeogeography evolution of continental margin in South China Sea trough application of Wilson cycle theory and sea-floor spreading hypothesis. The software of evaluation and management system of exploration rights has been developed, and 24 blocks were evaluated. New ideas and achievements have been acquired as follows:a. Four stages ,i.e. the continental rift ,the Neogenic continental margin,the thermal subsidence of mature continental margin and cooling subsidence of the mature continental margin ,can be divided in South China Sea, corresponding with tectonic movement,i.e.Lile,Xiwei,Nanhai and Nansha. The seafloor spreading of the central basin controlled thermal subsidence of the mature continental margin. The seafloor spreading had been limited, while the oceanic basin began becoming cool, and got into regional cooling subsidence period since Late Miocene.b. Based on new gravity&magnetic, seismic data and drilled wells, and combining with important geological limitation line, 8 basement areas can be divided in the Cenozoic basin of South China Sea. The basement features and distribution controlled the strata development and distribution of the Cenozoic basin. Based on the above study, evidences have been provided for that the blocks of Xisha and Nansha, Pearl River Mouth and Lile had been matched before Cenozoic, and reconstruction of the Cenozoic paleogeographic.c. For the first time, paleogeographic framework and lithofacies of the Cenozoic basin was recoveried and reconstructed according with time series in Neogenic continental margins of South China Sea. Paleogeographic maps show that the east of Neo-South China Sea was the open Pacific, the climate was moist, and there’s no condition for gypsolith deposition during neogenic continental-margin.A large island chain (Mindoro,Palawan etc.)had developed between Proto-South China Sea and Neogenic South China from Oligocene to middle Miocene. The proof has been found for sediment-source sedimentary phenomena in Qiongdongnan Basin , the depression of Zhongjian , and Beikang Basin.d. The software of“evaluation and management system of exploration rights blocks (MRGIS 1.0)”has been developed.24 exploration right blocks of South China Sea have been comprehensive evaluated. Huaguang sags of Qiongdongnan Basin, the northern depression of Zhongjiannan basin, and the central uplift of Beikang Basin are the main prospect directions in the near future.