Analyses on the tectonic thermal evolution and influence factors in the deep-water Qiongdongnan Basin
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Analyses on the tectonic thermal evolution and influence factors in the deep-water Qiongdongnan Basin WANG Zhenfeng1, SHI Xiaobin2*, YANG Jun2,3, HUANG Baojia1, SUN Zhen2, WANG Yahui1, JIANG Haiyan2, YU Chuanhai2,3, YANG Xiaoqiu2 1
Zhanjiang Branch of China National Offshore Oil Corporation (CNOOC) Limited, Zhanjiang 524057, China 2 Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China 3 University of Chinese Academy of Sciences, Beijing 100039, China Received 20 June 2014; accepted 29 September 2014 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2014
Abstract To reveal the tectonic thermal evolution and influence factors on the present heat flow distribution, based on 154 heat flow data, the present heat flow distribution features of the main tectonic units are first analyzed in detail, then the tectonic thermal evolution histories of 20 profiles are reestablished crossing the main deep-water sags with a structural, thermal and sedimentary coupled numerical model. On the basis of the present geothermal features, the Qiongdongnan Basin could be divided into three regions: the northern shelf and upper slope region with a heat flow of 50–70 mW/m2, most of the central depression zone of 70–85 mW/m2, and a NE trending high heat flow zone of 85–105 mW/m2 lying in the eastern basin. Numerical modeling shows that during the syn-rift phase, the heat flow increases generally with time, and is higher in basement high area than in its adjacent sags. At the end of the syn-rift phase, the heat flow in the deepwater sags was in a range of 60–85 mW/m2, while in the basement high area, it was in a range of 75–100 mW/m2. During the post-rift phase, the heat flow decreased gradually, and tended to be more uniform in the basement highs and sags. However, an extensive magmatism, which equivalently happened at around 5 Ma, has greatly increased the heat flow values, and the relict heat still contributes about 10–25 mW/m2 to the present surface heat flow in the central depression zone and the southern uplift zone. Further analyses suggested that the present high heat flow in the deep-water Qiongdongnan Basin is a combined result of the thermal anomaly in the upper mantle, highly thinning of the lithosphere, and the recent extensive magmatism. Other secondary factors might have affected the heat flow distribution features in some local regions. These factors include basement and seafloor topography, sediment heat generation, thermal blanketing, local magmatic injecting and hydrothermal activities related to faulting and overpressure. Key words: northern continental margin, South China Sea, surface heat flow, magmatism Citation: Wang Zhenfeng, Shi Xiaobin, Yang Jun, Huang Baojia, Sun Zhen, Wang Yahui, Jiang Haiyan, Yu Chuanhai, Yang Xiaoqiu. 2014. Analyses on the tectonic thermal evolution and influence factors in the deep-water Qiongdongnan Basin. Acta Oceanologica Sinica, 33(12): 107–117, doi: 10.1007/s13131-014-0580-9
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