南海西北次海盆及其邻区的地热流特征与研究

西北次海盆是南海海盆的一个重要构造单元，揭示西北次海盆的地热流特征对于整体认识南海海盆热状态和热结构至关重要.沿着OBS2006-1地震剖面采集的一批实测地热流数据显示，该热流探测剖面横穿南海北部陆坡、西北次海盆、中沙隆起、东部次海盆4个构造单元，结合地震解释剖面等资料对西北次海盆进行地热流特征分析及研究.结果表明:西北次海盆的平均热流密度值为104.5±9.9 mW/m2，与中沙隆起相邻的东部次海盆北部的平均热流密度值为97±2.5 mW/m2，热流密度值的空间变化与地幔埋深起伏相对应，并受地幔热源所控制；通过研究热流异常点，发现水深相近的相邻站位之间的海底表层沉积物温度差异是判别测站受海底地下水热循环影响程度和类型的依据之一；用最新海洋地热流探测成果，结合区域地质与地球物理资料，推测西北次海盆形成演化时代与西南次海盆相近，只是它的生命史比较短暂. 

Characteristics and Research of Heat Flow in the Northwest Sub-Basin and Its Adjacent Areas of the South China Sea

The Northwest sub-basin (NW sub-basin) is an important tectonic unit in the South China Sea. It is of great importance to reveal the geothermal characteristics of the NW sub-basin for the better understanding of thermal and thermal structures of the basins of South China Sea. We have collected a series of measured heat flow data along the OBS2006-1 seismic profile. This heat flow profile crosses four tectonic units, including the northern slope of the South China Sea, the NW sub-basin, the Zhongsha rise and the east sub-basin. With the seismic interpretation profile, this paper analyzes and studies in detail the heat flow characteristics. The results show that the average heat flow value is 104.5±9.9 mW/m2 in the NW sub-basin, and the average heat flow value in the northern part of the East sub-basin is 97±2.5 mW/m2, the change trend of the heat flow values is similar to that of the Moho depth, which manifests that the deep thermal state is controlled by the source of mantle heat. By studying the anomalies of heat flow, it is found that the temperature difference between the seabed surface sediments in adjacent sites is one of the basis for judging the degree and type of groundwater thermal cycling. With the latest ocean heat flow detection results, combined with regional geology and geophysical data, it is suggested that the formation of the NW sub-basin is similar to that of the Southwest sub-basin, but with relatively shorter history.