摘要
重力均衡是一普遍的地球物理现象,可为区域深部构造、岩石圈形变、地壳结构以及应力场状态研究提供参考信息,是研究地壳内部结构和划分大地构造单元的重要方法之一。华南陆块是欧亚板块重要组成部分,也是我国矿产资源“大粮仓”,虽然对华南陆块的研究已持续近百年,但在构造、成矿等诸多地质问题上仍存在较大争议。为了解华南陆块均衡程度及其对构造、成矿的影响,本文尝试从均衡重力异常和均衡深度异常两个方面来探索。首先利用卫星布格重力计算得到了均衡剩余重力异常,然后利用高程和壳幔密度差计算了均衡深度异常。结果表明华南陆块大部分区域地壳处于均衡状态,相对正均衡异常主要位于东部沿海地区和武陵山一带,相对负均衡异常反映了秦岭—大别造山带、江南造山带及华南陆块西缘造山活动。地震多沿正、负均衡深度异常的转换带或梯度带发生,认为这些地带通常为深部构造转换部位,应当成为地震活动研究关注的重点区域。均衡剩余重力异常也间接约束了不同类型金属矿床分布,正均衡剩余重力异常区多分布地幔来源金属矿床,而负均衡异常区则多产出壳源相关金属矿床。
Isostatic gravity is a universal geophysical phenomenon that can provide reference information for regional deep structure,lithospheric deformation,crustal structure,and stress field.It is one of the important methods to study the internal structure of the crust and divide tectonic units.The South China block is an important part of the Eurasian block and the“granary”of mineral resources in China.Although research on the South China block has been conducted for nearly 100 years,there are still great controversies regarding many geological issues.To understand the isostatic degree of the South China block and its influence on the structure and control of mineral resources,we investigated isostatic gravity and isostatic depth anomalies.The isostatic gravity anomaly was obtained using the satellite Bouguer gravity calculation,and then the isostatic depth anomaly was calculated using elevation and crust-mantle density contrast.We determined that the crust is iso-static in most regions of the South China block,and the relative positive isostatic anomalies are mainly dis-tributed in the eastern coastal areas and Wuling Mountains.The relative negative isostatic anomalies reflected the orogenic activities in the Qinling–Dabie orogenic belt,Jiangnan orogenic belt,and western margin of the South China block.The transition or gradient zone with positive and negative isostatic depth anomalies is usually the deep structural transition zone,and earthquakes occur along these areas intensively,which should be the key areas of earthquake activity research.Isostatic gravity anomalies also indirectly constrain the distribution of different types of metal deposits.The positive isostatic gravity anomalies mainly produce mantle-derived metal deposits,whereas the negative isostatic anomalies mainly produce crust-derived metal deposits.
作者
严加永
张永谦
罗凡
佘京瑾
姜昶旭
刘家豪
YAN Jia-yong;ZHANG Yong-qian;LUO Fan;SHE Jing-jin;JIANG Chang-xu;LIU Jia-hao(Chinese Academy of Geological Sciences,Beijing 100037;China Deep Exploration Center,China Geological Survey&Chinese Academy of Geological Sciences,Beijing 100037;School of Geophysics and Measurement-control Technology,East China University of Technology,Nanchang,Jiangxi 330013)
出处
《地球学报》
CAS
CSCD
北大核心
2022年第6期744-754,共11页
Acta Geoscientica Sinica
基金
中国地质调查局地质调查项目(编号:DD20190012
DD20221643)
国家自然科学基金项目(编号:92062108
42074099
41630320)联合资助。
关键词
华南陆块
均衡重力异常
均衡深度异常
动力学
South China block
isostatic gravity anomaly
isostatic depth anomaly
earth dynamics
