Lithospheric thermal structure of the Pearl River Mouth Basin, northern South China Sea

Abstract

The lithospheric thermal structure is resulted from lithospheric tectono-thermal evolution. It provides fundamental constraints on thermal history reconstruction which is of great importance to basin dynamics investigation and hydrocarbon resources assessment. Due to the fact that conducting geological exploration offshore is much more difficult than inland, lithospheric thermal structure studies are less abundant in the continental margin basins than in the continental areas in China. In this study, we update the existing heat flow database of the Pearl River Mouth Basin of northern South China Sea with data published since 2003 to produce a new heat flow map for the study area. We further analyze the lithospheric thermal structure of the Pearl River Mouth Basin based on the updated heat flow database and the existing seismic crustal structure data acquired by the project USA-China Joint Investigation on Marine Geology of South China Sea. Result shows that the crustal heat flow of the study area is 18. 7 similar to 28. 6 mW . m(-2), while the mantle heat flow ranges from 36. 9 to 91. 4 mW . m(-2). The ratio of crustal heat flow to mantle heat flow varies between 0. 23 and 0. 75. From the continental shelf area to the ocean-continental transition zone, the surface heat flow appears to increase while crustal heat flow decrease, implying that the mantle heat flow is the predominant contributor to the surface heat flow in the Pearl River Mouth Basin. The thermal lithospheric thickness of the study area turns out to be 34. 0 similar to 87. 2 km, with the average value of 65. 5 km, showing that the Pearl River Mouth Basin is of characteristics of lithosphere stretching and thinning.