【摘要】 珠江口盆地白云凹陷是南海最具代表性的第三系深水陆坡沉积区。以穿过白云凹陷中部的一条深反射地震剖面(14s)为研究基础,采用综合地球物理研究方法分析了该区地球物理场特征,根据重力异常平面等值线勾画了白云凹陷的形态,并提取该测线相对应的重磁剖面数据,利用重磁资料和地震剖面进行了综合反演。以深剖面地震资料建立了地质模型,利用所得的重力数据进行了研究深部结构的正演拟合,实测与计算值拟合较好,支持中生代俯冲洋壳存在的观点;同时结合地震资料对深部结构进行了分析,该区莫霍面由陆向海抬升,呈阶梯状变化,地壳厚度逐渐减薄,具有大陆边缘陆壳向洋壳过渡的特征。根据地质模型还进行了变密度综合反演拟合来分析基底岩性特征,该区基底主要为中酸性岩浆岩,部分为变质岩和基性火山岩,岩石密度由陆向洋逐渐减小,磁性体分布不均。更多还原

【Abstract】 The Baiyun sag in the southern Zhujiang River Mouth Basin contains Cenozoic deep-water deposition system. This paper discusses the characteristics of gravitational and magnetic fields of the Baiyun sag and conducted a gravity-magnetic inversion along a long-cable seismic section across the sag. The negative area enclosed by +5mGal contour of the free-air gravity anomaly approximates the outline of the sag and corresponds to negative gravity and magnetic anomalies. The Moho surface shallows and the crust beneath the sag thins seawards stepwisely, indicating a transitional-type crust. Gravity modeling supports the proposal that there is a distinct Mesozoic subduction zone at the depth of the southern segment of the profile. The basement along the profile contains mainly acid-intermediate igneous rocks and secondarily metamorphic rocks and basic igneous rocks.更多还原