广西地区岩石圈表层与深部构造之关联性:源于岩石圈密度与磁性结构的解读  

Tectonic Relationship between Upper and Lower Lithosphere in Guangxi Area:A Comprehension from Lithospheric Density and Magnetic Structures

作　　者：黎海龙 胡正旺[1] 杜劲松[1,3] 涂晨鸣 支剑丽 刘鹏宇 梁青 陈超[1] Li Hailong;Hu Zhengwang;Du Jinsong;Tu Chenming;Zhi Jianli;Liu Pengyu;Liang Qing;Chen Chao(Institute of Geophysics&Geomatics,China University of Geosciences,Wuhan 430074,China;China-ASEAN Geosciences Cooperation Center,Nanning 530023,China;State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]中国地质大学地球物理与空间信息学院,湖北武汉430074 [2]中国-东盟地学合作中心,广西南宁530023 [3]中国地质大学地质过程与矿产资源国家重点实验室,湖北武汉430074

出　　处：《地球科学》2022年第4期1507-1516,共10页Earth Science

基　　金：国家自然科学基金项目(No.41774091);中国地质调查局地质调查项目(Nos.DD20179607,DD20160060)。

摘　　要：广西地处华南地块、印支地块与西太平洋板块的汇合部位,因特殊的构造部位,广西区内大地构造单元归属、构造单元边界等许多基础地质问题一直存在争议.自新生代以来的板块构造运动对岩石圈的改造,广西地壳与上地幔在地震波速度及温度结构方面具有显著差异.应用卫星重、磁异常数据以及区域重力和航磁资料对广西地区岩石圈密度和磁化率结构及其与上地壳构造的关系开展了研究,结果显示广西地区地壳密度和上地壳磁性结构与现今地表构造较为契合,但下地壳密度结构与上地幔存在不连续现象;此外,岩石圈磁化率结构指示中下地壳存在不同范围和程度的解耦.对广西岩石圈密度与磁性结构的解读认为,在中生代以来岩石圈被大规模改造的背景下,幔源物质上侵至上地壳的规模和范围都有限,这可能是整个广西地区上地幔结构与地壳构造不对应的主要原因.Guangxi is located in the convergent region among South China block,Indo-Chinese block and West Pacific plate.Due to its special tectonic position,there have been disputed on several basic geological problems in Guangxi region,such as the ascription and boundaries of tectonic units.Because the lithosphere has been reconstructed by the plate tectonic movements since the Cenozoic,the crust and upper mantle beneath Guangxi area have obvious differences in seismic wave velocity and temperature structures.It employs satellite gravity and magnetic data as well as regional gravity and aeromagnetic survey data to investigate the relationship between lithospheric density and magnetic susceptibility structure and upper crust structure in Guangxi area.Results suggest that the crustal density and upper-crust susceptibility structures coincide with the surface geological structures,and the density structures of the lower crust and the upper mantle are discontinuous beneath Guangxi area.Susceptibility structure implies that different extents of mid-lower crust decoupling had caused in different parts in Guangxi area.As a result,the scale and scope of mantle-derived materials into the upper crust were limited under the background of large-scale lithospheric reconstruction since Mesozoic.It may be the main reason why the upper mantle structure in Guangxi area is not corresponding to that of the crust.The mid-lower crust decoupling results in that the magmatic activity in Guangxi area is obviously weaker than that in the surrounding area since Cretaceous,especially in the northern region of the Pingxiang-Dali fault zone.

关 键 词：广西地区 重磁异常 岩石圈 密度结构 磁性结构 地球物理 

分 类 号：P318[天文地球—固体地球物理学]