摘要
分析了南海北部陆架西区盆地的地质、地球物理场特征，计算了研究海域重、磁资料的１阶小波细节、４阶小波逼近变换．根据分析与计算可知，研究区的布格重力异常以北西低的负值，东南高的正值为特征．在东部及东南部异常等值线走向为北东；西部异常等值线以北西走向为特征；西北地区异常以北东东、北东走向的局部等值线圈闭为特征，磁场的展布十分复杂，按磁异常的变化程度可分为三个变化区，即磁异常平静区、剧变区及缓变区．磁异常的平静区位于研究区的西部，即莺歌海盆地所在位置，这一带磁异常等值线极为稀疏，异常值为负背景异常．剧变区位于海南岛，该地区的磁异常变化极为剧烈，异常特征以局部小圈闭为特征，等值线分布密集．磁异常的平缓区位于平静区及剧变区之外的其它地区．琼东南盆地、北部湾盆地的磁异常具有此特征．根据重、磁场资料以及南海北部盆地钻井取样的测试结果、同时参考穿越南海地学断面的结果．对研究区的地壳结构进行了反演计算，计算表明南海陆架盆地区域地壳结构较为复杂，研究区的地壳厚度在２２～３３ｋｍ之间，总的趋势由陆向洋地壳厚度逐渐减薄，反映出该区域地壳具有陆壳、拉伸陆壳、过渡壳的性质，同时存在有上地幔隆起区及凹陷区．磁性底界面厚度在１７～２４ｋｍ之?
This paper analysed characters of geology and geophysical fields of northwestern of South China Sea. One steps detail and four steps approach of wavelet transform of gravity and magnetic anomalies of the study area were calculated. According to analyzing and calculating, Bouguer gravity anomalies of study area are negative in northwestern and positive in southeastern. The tend towards of gravity anomalies is NE in eastern and southeastern. The tend towards of gravity anomalies is NW in western. The gravity anomalies in northwestern is tend towards NEE and NE of local isoline enclose. The distribution of magnetic anomalies of study area is complex. According to extent of distribution of magnetic anomalies, magnetic anomalies of study area are divided three sections. They are quietude section, intense section and relaxed section. The quietude section is located in western of study area (Yinggehai basin). Magnetic anomalies isolines are very sparseness. Background value is negative. The intense section is located in Hainan island. Magnetic anomalies of this area changed very acute. The character of magnetic anomalies of the area is small and local enclosed. Distribution of isolines are denseness. The relaxed section is Located beyond quietude section and intense section. Qiongdongnan basin and Beibuwan basin are belong to relaxed section. Basis on gravity, magnetic, testing results of logging of northern basins of South Sea and results of geoscience transect that through South Sea, we calculated crust structure of study area. The results show that crust structure of the study area is complex. Moho depth is from 22 to 33km. Trend is decreased thin from land to ocean. This distribution shows that crust takes on characters of land crust, draw extend crust and transition crust. Magnetic interface is from 17 to 24km. It is deeper in Yinggehai basin and shallower in Hainan island.
出处
《地球物理学进展》
CSCD
2001年第3期1-11,共11页
Progress in Geophysics
基金
国家重点基础研究发展规划项目(编号:G20000467-01)
中国科学院知识创新工程项目(编号:KZCX2-209-2).
