长江中下游成矿带岩石圈深部结构的远震P波层析成像  

Deep structure of the middle and lower reaches of Yangtze River metallogenic belt from teleseismic P-wave tomography

作　　者：郑洪伟[1] 李廷栋[2,3] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质科学院,北京100037 [3]国土资源部咨询研究中心,北京100035

出　　处：《地球物理学进展》2013年第5期2283-2293,共11页Progress in Geophysics

基　　金：国家专项深部探测技术实验与集成项目SinoProbe-2(No.201011044);国家专项深部探测技术实验与集成项目SinoProbe-2(No.201011044)联合资助;国家自然科学基金项目(40904026;41274095;41374101);中国地质科学院地质所基本科研业务费(J1204;J1216);国土资源部公益行业科研专项(201011013)

摘　　要：长江中下游成矿带是我国重要的铜铁等多金属矿产资源基地.本文利用中国地震台网中心和国际地震中心的震相报告资料,11个地震台站记录的2880个远震事件,共8640条远震P波到时数据,对长江中下游成矿带岩石圈深部结构进行了层析成像反演.结果表明:合肥盆地上地幔表现为低速特征;大别造山带岩石圈内的高速体应该是向华北板块下俯冲并在深部发生断离的扬子板块;扬子板块的俯冲断离导致了软流圈物质上涌;长江中下游成矿带地幔都以低速为主,且均表现为从地幔深处向北涌向地表.该上涌的软流圈物质是矿集区形成的深部物质来源;同为长江中下游地区的东经120°以东地区,该区几乎没有大规模的矿床出露,由浅部到深部总体表现为高速,也佐证了上涌的软流圈物质是成岩成矿的物质来源.初步提出长江中下游地区的成矿模式,认为扬子板块俯冲断离导致软流圈上涌,进而引起岩石圈拉张,岩浆通过底侵作用上升到地壳浅部,然后沿着断裂构造形成侵入岩体,并最终形成了长江中下游巨型成矿带.The middle and lower reaches of Yangtze River metallogenic belt is an important iron, copper and polymetallic base in China. We determined a detailed three-dimensional P-wave velocity structure of the upper mantle beneath the middle and lower reaches of Yangtze River by applying teleseismic tomography to 8640 high-quality P- wave arrival times from 2880 teleseismic events recorded by 11 broadband stations of seismic networks. Our tomographic results show that prominent low P-wave velocity anomalies under the Hefei Basion. High Pwave velocity anomalies are revealed in the upper mantle of the Dabie orogen, which represent the subdected Yangtze block. Our image also suggests the break-off of the subducted Yangtze block caused by its interaction with the North China Craton under the Dabie orogen. The block break-off may have created the upwelling of the asthenospheric matter,causing magma underplated into the lower crust of the Yangtze metallogenetic belt along the extended lithosphere, resulted in the formation of mineral deposits. There are no mineral deposits under the east of longitude 120°E in the middle and lower reaches of Yangtze River metallogenetic belt because of lacking the magma source from the upwelling of asthenospheric matter.

关 键 词：长江中下游成矿带 深部结构 层析成像 扬子板块拆沉 软流圈上涌 

分 类 号：P541[天文地球—构造地质学] P315[天文地球—地质学]