南海北部磁静区重磁特征及成因  

RESEARCH ON GENESIS AND CHARACTERISTICS OF MAGNETIC QUIET ZONE IN THE NORTH SOUTH CHINA SEA

作　　者：刘鸿[1,2,3] 栾锡武[3,4] 岳保静[3,4] 曾洁[1,2] 

机构地区：[1]中国科学院海洋研究所,海洋地质与环境重点实验室,青岛266071 [2]中国科学院大学,北京100049 [3]青岛海洋地质研究所,青岛266071 [4]国土资源部海洋油气资源与环境地质重点实验室,青岛266071

出　　处：《海洋地质与第四纪地质》2014年第4期65-78,共14页Marine Geology & Quaternary Geology

基　　金：国家重点基础研究发展规划项目(2007CB411702)

摘　　要：南海磁静区位于南海北部的洋陆结合带上,在磁异常图上位于陆架高值正磁异常带以南,海盆磁异常条带区以北。收集了南海北部的地质和地球物理相关资料,总结了南海北部磁静区的研究现状,对ΔT磁异常数据进行了低纬度化极处理,参考磁静区周围的自由空间重力异常分布,结合区域地质背景划分了南海磁静区的分布;采用小波多尺度分解方法讨论了南海北部磁静区及周围区域的重磁场特征,对主要界面的反演发现磁静区内存在磁性基底深度增加、居里等温面隆升、磁性层厚度减薄和莫霍面抬升的现象,认为南海磁静区形成的直接原因是区域内磁性层厚度的减薄,包括中生代末期地壳的拉张沉降使区域老地层断陷,磁性基底深度增加,磁异常减弱;拉张减薄促使深部地幔热物质向上运移,莫霍面抬升,磁性层发生热退磁,居里等温面抬升,磁性层厚度减薄,磁异常减弱;南海扩张期和张裂以后磁静区的热活动剧烈,深部高温物质底侵,形成高速层,进一步减弱了区域磁异常。Marine magnetic anomalies have two kinds of distribution patterns：the magnetic lineation and the magnetic quiet zone（MQZ）.The MQZs show large-area magnetic anomalies with low value in magnetic anomaly maps.The MQZ in the northern South China Sea is located along the continent-ocean boundary（COB）,to the south of high positive magnetic anomaly belt and the north of the magnetic lineation in the sea basin.We define the distribution range of the MQZ clearly according to the△T magnetic anomaly data,the free air gravity anomaly data and tectonic background information.We obtain the reduction to pole magnetic anomaly using a low magnetic latitude method and discuss the characteristics of gravity and magnetic field in the Northern South China Sea by the wavelet multi-scale decomposition method.We obtain the depth of the magnetic basement,the depth of the Curie isothermal interface,the thickness of the magnetic layer and the depth of Moho interface by the Parker inversion method.The inversion results show that the depth of Curie isothermal interface and the depth of Moho in the MQZ are shallow.The magnetic basement is deeper than surrounding areas.We infer that the thinning of the magnetic layer is the direct reason of the formation of the MQZ which has three causes.

关 键 词：南海北部 磁静区 化磁极 居里等温面 高速层 

分 类 号：P531[天文地球—古生物学与地层学]