论南沙海槽的地壳性质

根据海上地球物理测量,对四条剖面的重力和地震剖面资料进行联合正反演推算,结合已发表的国内外地质、地球物理资料对南沙海槽的地壳厚度及性质进行了分析。结果表明,南沙海槽的地壳为一个减薄的陆壳,从南沙微陆块向婆罗洲方向厚度减薄,具有类似大陆边缘从陆壳向洋壳过渡部位的地壳构造特征。顺着海槽的走向,地壳厚度变化趋势是从东北向西南变薄。从构造演化的角度分析,南沙海槽是古南海洋陆交界的边缘,由于古南海的闭合及晚白垩世以后婆罗洲逆时针方向旋转,海槽的大部分是陆壳,其西南端可能有残留的洋壳。

THE CRUST IN THE NANSHA TROUGH

The crustal thickness and property in the Nansha Trough was discussed in this paper, using inverse methods for intergrating gravity anomalies in 4 seismic profiles collected by Nansha investigation team of Academia Sinica during 1987 - 1995- We concluded that The Crust in Nansha trough is a thinned continental crust and its thickness was reduced from Nansha microblock toward Borneo, similar to the continental margin crust thinned toward oceanic crust. The thinned trend of the crust is from ME toward SE along trough. It is most possibly oceanic crust in the end of profile 94N05. From tectonic evolution point view Nansha trough was a continental margin of antique South China Sea. Since the close of antique South China Sea and counterclockwise rotation of Borneo during Cretaceous, the crust in Nansha Trough is continental crust mostly, but still partly remined oceanic crust. Therefore, the crust in Nansha Trough is continental crust mostly, but small part remined oceanic crust in its southwest end.