Thermal Structure and Moho Temperature of the Qiongdongnan Basin, Northern Margin of the South China Sea

Abstract

AbstractCompared with continents, there are less studies on lithospheric thermal structure in oceans or continent‐ocean transition zones. Based on submarine heat flow data and related petrological thermal properties available in the Qiongdongnan Basin, we calculate the constitution of heat flow and deep temperature of different layers along four distinct seismic profiles. The crustal structure in this area is divided into four layers based on latest analysis of P‐wave velocity variation, that is sediment cover. Upper crust, normal lower crust and anomalous lower crust with high velocity, respectively. The results demonstrate that mantle heat flow increases from shallow water to deep water, which predominantly results in the current distribution of submarine heat flow in the Qiongdongnan Basin. Besides, its ratio to submarine heat flow is 76.3±7.0% on average, suggesting a typical feature of the lithospheric thermal structure model consisting of “cold crust and hot mantle”. In addition, Moho temperature beneath the Qiongdongnan Basin concentrates in the range 500~700 °C with a lower temperature region and two higher temperature regions, which is primarily ascribed to the extent of the lithospheric thinning of the northern margin and well‐developed faults of the South China Sea.