南海热流分布特征

南海地热异常明显与主要构造断裂带和水热/岩浆活动有关。东部平行于马尼拉海沟的一条SN向低热流异常带起因于南海洋壳对吕宋岛的俯冲。南沙海槽及其南部陆缘的地温场比较复杂。南部的曾母盆地是一个显著的高地热异常区,它起因于年轻的构造拉张,其地幔热流高达中央海盆洋壳的地幔热流值。西南次海盆也是一个高地热异常区,虽然该次海盆形成较早,但与年轻的构造拉张有关。热流资料的分析结果表明,南海中央海盆西缘断裂带、西南次海盆和曾母盆地构成的NE向高热流异常带可能是一个大型的现代构造拉张带。

HEAT FLOW DISTRIBUTION OF THE SOUTH CHINA SEA

The South China Sea (SCS) is the biggest marginal sea in West Pacific, which is located at the convergent juncture of Australian, Eurasian and Pacific plates. Highest heat flow values are often measured at the joint of two kinds of deep faults, probably related to the associated magmatic/hydrothermal activity. The important Beikong-Tinjar fault separated the tectonic units with different temperature fields. A low NS-striking thermal anomaly on the east part parallel to Manila trench is developed by the subduction of oceanic crust of SCS under Luzon island. Nansha trough and the southern continental margin have relatively complicated temperature fields, no typical low thermal anomalous zone, which makes it questionable that Nansha trough is a relict of the old South China Sea. Zengmu basin and Sunda shelf on the south part are apparently thermal anomalous units, whose mantle heat flow values reach that of the central basin of SCS, which probably results from the young tectonic extension in this region. The southwest subbasin is another thermal anomalous unit, which might be also related to the young tectonic extension. Although the southwest subbasin has formed for a longer time, it has a different tectonic and heat history from the east subbasin. The conclusion of heat flow data analyses indicates that the huge NE-striking high thermal anomalous zone corstructed by western faults, southwest subbasin and Zengmu basin might be a modern tectonic extensional zone.