南沙中部海域北康盆地重、磁异常解释

INTERPRETATION OF GRAVITY AND MAGNETIC ANOMALIES IN THE BEIKANG BASIN OF CENTRAL NANSHA

通过对南沙中部海域北康盆地重、磁资料的定量计算、定性解释,认为空间重力异常主要受浅部地质因素影响,空间重力异常的高低间接地反映了海底地形起伏变化、新生代沉积层厚度大小、沉积岩密度变化以及基底的坳、隆等特征;磁力异常资料通过预后处理及反演计算,推测北康盆地新生代火成岩以酸性-中基性岩为主,磁性基底与声波基底基本一致,可划分为三处坳陷及两处隆起;北康盆地位于减薄的大陆壳上,莫霍面深度约19～22 km。重、磁资料综合解释结果为沉积盖层构造分区、基底断裂推断及火成岩岩性识别提供依据。

Through quantitative calculation and qualitative interpretation to gravity and magnet- ic anomalies data collected from the Beikang basin of central Nansha, it is demonstrated that the gravity anomalies mainly influenced by shallow geological factor, the Gravitational high and Gravitational low indirectly reflect the topographical features of the sea bed、 the thickness of Cenozoic sedimentary、 the density changing of sedimentary and the depression or rise of basin . The conclusion that Cenozoic igneous of the Beikang basin mainly is composed of acidite-inter- mediate base rock infers from disposition and opposite calculation of magnetic dates. The mag- netic basement is basically consistent with the acoustic basement, can be divided to two depres- sion and three rise zones. Beikang basin lies to weaken continental crust with thickness of about 19～20 km. The result of gravity and magnetic interpretation provide inference of structural di- vision of the basement and distinguish of igneous rock.