Three-dimensional P-wave Velocity Structure Modelling of the Middle and Lower Reaches of the Yangtze River Metallogenic Belt: Crustal Architecture and Metallogenic Implications  

作　　者：CHEN Anguo LÜ Qingtian ZHOU Taofa DU Jianguo DING Juan YAN Jiayong LU Zhitang 

机构地区：[1]School of Resources and Environmental Engineering,Hefei University of Technology,Hefei 230009,China [2]Geological Survey of Anhui Province,Hefei 230001,China [3]Chinese Deep Exploration Center(SinoProbe Center),Chinese Academy of Geological Sciences,Beijing 100037,China [4]Anhui Earthquake Agency,Hefei 230031,China

出　　处：《Acta Geologica Sinica(English Edition)》2020年第6期1808-1821,共14页地质学报（英文版）

基　　金：funded by grants from the Key Project of the National Natural Science Foundation of China(No.41630320);the National Key Research and Development Program of China(No.2016YFC0600200);the Hefei Postdoctoral Science Foundation。

摘　　要：In this study,we compiled and analyzed 69310 P-wave travel-time data from 6639 earthquake events.These events(M≥2.0)occurred from 1980 s to June 2019 and were recorded at 319 seismic stations(Chinese Earthquake Networks Center)in the study area.We adopted the double-difference seismic tomographic method(tomo DD)to invert the 3-D P-wave velocity structure and constrain the crust-upper mantle architecture of the Middle and Lower Reaches of the Yangtze River Metallogenic Belt(MLYB).A 1-D initial model extracted from wide-angle seismic profiles was used in the seismic tomography,which greatly reduced the inversion residual.Our results indicate that reliable velocity structure of th e uppermost mantle can be obtained when Pn is involved in the tomography.Our results show that:(1)the pattern of the uppermost mantle velocity structure corresponds well with the geological partitioning:a nearly E-W-trending low-velocity zone is present beneath the Dabie Orogen,in contrast to the mainly NE-trending low-velocity anomalies beneath the Jiangnan Orogen.They suggest the presence of thickened lower crust beneath the orogens in the study area.In contrast,the Yangtze and Cathaysia blocks are characterized by relatively high-velocity anomalies;(2)both the ultra-high-pressure(UHP)metamorphic rocks in the Dabie Orogen and the low-pressure metamorphic rocks in the Zhangbaling dome are characterized by high-velocity anomalies.The upper crust in the Dabie Orogen is characterized by a low-velocity belt,sandwiched between two high velocity zones in a horizontal direction,with discontinuous low-velocity layers in the middle crust.The keel of the Dabie Orogen is mainly preserved beneath its northern section.We infer that the lower crustal delamination may have mainly occurred in the southern Dabie Orogen,which caused the mantle upwelling responsible for the formation of the granitic magmas emplaced in the middle crust as the low-velocity layers observed there.Continuous deep-level compression likely squeezed the granitic magma upward to i

关 键 词：3D P-wave velocity structure double-difference seismic tomography crust-upper mantle Dabie Orogen Middle and Lower Reaches of the Yangtze River Metallogenic Belt 

分 类 号：P612[天文地球—矿床学] P631.4[天文地球—地质学]