扬子区地壳密度扰动成像和华南燕山期花岗岩成因  

Crustal Density Imaging of Yangtze Craton and Formation of the Yanshanian Granitites in South China

作　　者：杨文采[1] YANG Wencai(College of Geosciences,Zhejiang University,Hangzhou,310027)

机构地区：[1]浙江大学地球科学学院,杭州310027

出　　处：《地质论评》2018年第5期1045-1054,共10页Geological Review

基　　金：国家自然科学基金资助项目(编号:41574111)的成果~~

摘　　要：用区域布格重力场小波变换多尺度分析方法确定了扬子克拉通地壳的密度扰动模式,它反映了区域的壳源大花岗岩基等板内构造。扬子克拉通的大地构造边界和上地壳浅层密度扰动梯度带重合。克拉通内部上地壳浅层密度扰动和大地构造分区没有明显的对应关系;但是它和地质图有一定对应关系。根据构造边界和上地壳浅层密度扰动梯度带一致的原则,利用研究区重力小波细节勾画出了上地壳结晶基底构造图,提供基底构造准确定位的参考。由于大陆地壳经常发生岩层的近水平拆离,地面的地质构造和地下构造可能发生明显变化。基于密度成像的地壳构造研究表明,古地块的碰撞作用使大陆地壳发育裂隙裂缝,在三叠纪华北和扬子克拉通碰撞时地壳原有的裂隙裂缝复活了,又使得热流体活动加剧和中地壳岩石逐渐重熔,形成了雪峰山—幕阜山—皖南黄山燕山期花岗岩带。花岗岩重熔作用属于岩石圈克拉通化的一种作用。现今雪峰山、幕阜山和皖南黄山还是弱地震多发区,说明这个燕山期花岗岩带虽然已经克拉通化,但是克拉通化的程度还是比扬子地块略逊。Objectives： This work shows the results of computing the 3D density disturbance images in Yangtze Craton and interpretation of the these results based on geodynamics and petro-physics,especially for crust beneath craton terrains.Methods： We apply the scale—depth relationship of gravity anomalies and the multi-scale wavelet analysis for extracting crustal density information from surface Bouguer gravity data,and presents density disturbance images of the upper,middle and lower crust,which represent the three dimensional density structures in the studied area.Results： The tectonic boundary of the Yangtze craton are coincided with the upper-crust density perturbation gradient zones.But inside the craton,there is no obvious correspondence between the density perturbation of the upper crust and the tectonic zoning.However,it has a certain correspondence with the geological map.According to the principle of uniforming structure boundaries and shallow density perturbation gradient bands in the crust,the structure map of the deep crystal basement is drawn by using the detail of gravity wavelet in the study area,which provides a reference for accurate location of basement structure.Because the continental crust often occurs near horizontal detachment of strata,the ground geological structure and underground structure may change obviously.The study of crustal tectonics based on density imaging shows that the ancient collision processes caused cracks and faults in the continental crust,which were resurrected during the Triassic collision between the North China and Yangtze Craton,gradually reducing the hot-fluid activity,rock anatexis and melting in the middle crust.The Xuefeng—Mufu—South Anhui Huangshan Mountain Yanshanian Granite Belt was formed by this way.Conclusions： The granite anatexis is a process of Lithospheric cratonization.Nowadays of Lithospheric craton.Nowadays the Xuefeng—Mufu—Huangshan mountains still belong to weak earthquake regions,which indicates that the Yanshanian Granite Belt has bec

关 键 词：中国大陆 扬子克拉通 地壳密度成像 区域布格重力场 中地壳重熔作用 燕山期花岗岩 

分 类 号：P588.121[天文地球—岩石学]