南海中央海盆热结构及其地球动力学意义

依据南海中央海盆大地热流观测值及地壳结构资料 ,利用地热学方法计算了海盆及周缘壳内温度和热流分布 ,并得出壳幔热结构配分比例 .计算结果表明 ,中央海盆洋壳层内垂向热流变化不大 ,但垂向温度变化较大 ,这是地幔上涌所致 .海盆内成片分布的地热区 ,则是局部地区地幔上涌 ,导致多期次、多方向海底扩张的反映 .海盆区地幔热流在地表实测大地热流中所占比例高于 80 %,地壳下部热流在地壳总热流中所占比例小于 2 0 %.由此推测 ,中央海盆洋壳层 3厚度过薄 ,可能是后期热事件减缓了上地幔的冷却过程 ,而初始地壳熔融程度较低 ,2种因素综合所致

Thermal Structure of Central Basin in South China Sea and Their Geodynamic Implications

Based on the terrestrial heat flow and crustal structure data, this paper calculates the temperature and the thermal structure of lithosphere in the South China Sea. The result shows that there is a larger change of temperature along vertical direction in the central basin, which is caused by the uplifting of mantle. Mantle uplifting in local areas would cause seabed outspread in multi periods and multi aspects.As a result, different areas of heat flow value in the central basin are formed. The percentage of heat flow from mantle is bigger than 80% in terrestrial heat flow, whereas the percentage of lower crustal heat flow is smaller than 20% in terrestrial heat flow. We argue that two factors might produce the thinning of layer 3 in central basin crust. One factor is the lower original crustal temperature, the other is the slowly cooling process after late heating event.