Seafloor in-situ heat flow measurements in the deep-water area of the northern slope, South China Sea

Seafloor heat flow data is the fundamental data for studying marine geodynamics and evaluating petroleum resource. Though resource of petroleum and gas hydrate is abundant in the deepwater areas of the northern slope of the South China Sea, there are very few heat flow sites. To investigate the geothermal distribution in the deepwater areas of the northern slope, which are thought to be advantaged areas for gas hydrates, a Jianyu-1 type heat flow probe was employed and 16 heat flow data in Xisha and Shenhu sea areas were obtained successfully. The results show that the heat flow of both Xisha Trough and Baiyun Sag is high. In Xisha Trough, except for one unreliable site, the temperature gradients in surface sediment of the other two sites are 105.3 and 99.9 degrees C . km(-1) respectively, and their heat flow values are 89 +/- 1 and 87 +/- 1 mW . m(-2), respectively. The temperature gradients of the 13 heat flows sites in the middle of Baiyun Sag range from 58.5 to 100.7 degrees C . km(-1), and except for 4 heat flows which are lower than 70 mW . m(-2), their heat flow values range from 75 +/- 2 to 101 +/- 4 mW . m(-2), which are generally higher than that previously obtained from the eastern part of Baiyun Sag. Analyses suggest that the high thermal regime in Xisha Trough and Baiyun Sag is related with high thermal background, and affected by latest active faults, diapiric structure, magma intrusion and heat fluid.