基于约束三维重力反演的南极大陆地壳密度结构研究  

Crustal density structure of the Antarctic continent from constrained 3-D gravity inversion

作　　者：纪飞[1,2] 李斐 张峤[3] 高金耀 郝卫峰 李永东[4] 管清胜[2] 林星 JI Fei;LI Fei;ZHANG Qiao;GAO JinYao;HAO WeiFeng;LI YongDong;GUAN QingSheng;LIN Xing(Chinese Antarctic Center of Surveying and Mapping,Wuhan University,Wuhan 430079,China;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;Second Institute of Oceanography,Ministry of Natural Resources,Hangzhou 310012,China;Institute of Geophysics and Geomatics,China University of Geosciences,Wuhan 430074,China;Tianjin Center of Geophysical Prospecting,Tianjin 300170,China)

机构地区：[1]武汉大学中国南极测绘研究中心,武汉430079 [2]自然资源部第二海洋研究所,杭州310012 [3]中国地质科学院地质力学研究所,北京100081 [4]中国地质大学地球物理与空间信息学院,武汉430074 [5]天津市地球物理勘探中心,天津300170

出　　处：《地球物理学报》2019年第3期849-863,共15页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41531069;41576069;41706215;41574004);国家重点研发计划(2017YFA0603104);国家海洋局海洋沉积与环境地质重点实验室开放基金(MASEG201704);中国地质调查局中国地质科学院基本科研业务"南极西罗斯海新生代岩浆与构造和冰川作用地球物理研究"联合资助

摘　　要：地壳密度是表征其物质组成以及结构特征的一个基本参数,是深入理解构造演化、地球动力学等问题的重要基础.本文利用最新发布的布格重力异常数据,以现有的三维S波速度模型、地表热流以及岩石学数据作为约束条件,采用引入深度加权函数的三维重力反演算法,获取了南极大陆三维精细密度结构模型.研究结果显示,南极大陆地壳尺度范围内密度异常在-0.25～0.20g·cm^(-3)之间.大致以南极横断山脉为界,受中生代与新生代多期拉张活动的影响,西南极上地壳密度异常以低值为主,与东南极克拉通的高密度异常呈现明显对比关系.通过对比发现,反演的密度结构与岩石圈强度信息存在较好的相关性.进一步分析西南极裂谷系统的密度结构与岩石圈强度,认为受新生代拉张活动和岩浆活动影响的局部地区除外,热沉降作用很可能使得地壳趋于冷却.此外,西南极的低密度特征延伸到南极横断山脉,结合现有的研究结果认为可能需要多种机制来解释南极横断山脉的隆升过程.Crustal density is a fundamental physical parameter that helps to reveal its composition and structure,and hence it is also significantly related to the tectonic evolution and geodynamics.Based on the latest complete Bouguer gravity anomalies and by the constrains of 3-D shear velocity model,surface heat flow and petrology data,the 3-D gravity inversion method,incorporating deep weighting function,has been used to obtain the refined density structure over the Antarctic continent.Our results show that the density anomalies changes from-0.25 g·cm^-3 to 0.20 g·cm^-3.Due to the multi-phase extensional tectonics in Mesozoic and Cenozoic,respectively,the low density anomalies dominates in the West Antarctica,whereas the East Antarctica is characterized by high values of density anomalies.By comparing with the variations of effective elastic thickness,the inverted density structure correlates well with the lithospheric strength.According to the mechanical strength and inverted density anomalies in the West Antarctic Rift System(WARS),our analysis find that except for the small-scale area affected by the Cenozoic extension and magmatic activity,the crustal thermal structure in the most part of WARS tends to be normal under the effect of thermal diffusion.Finally,the low density anomalies features in West Antarctica extend to beneath the Transantarcitc Mountains(TAMs),however,we hypothesize that a single rift mechanism seems not be used to explain the entire TAMs range.

关 键 词：南极大陆 地壳 三维重力反演 密度结构 参考密度模型 

分 类 号：P542[天文地球—构造地质学] P314[天文地球—地质学]