| 长江中下游成矿带及邻区地壳剪切波速度结构和径向各向异性 |
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| 引用本文： | 欧阳龙斌,李红谊,吕庆田,李信富,江国明,张贵宾,史大年,郑丹,张冰,李佳鹏.长江中下游成矿带及邻区地壳剪切波速度结构和径向各向异性[J].地球物理学报,2015,58(12):4388-4402. |
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| 作者姓名： | 欧阳龙斌 李红谊 吕庆田 李信富 江国明 张贵宾 史大年 郑丹 张冰 李佳鹏 |
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| 作者单位： | 1. 地下信息探测技术与仪器教育部重点实验室(中国地质大学, 北京), 北京 100083;2. 广东省地震局, 广州 510070;3. 中国地质大学(北京), 地球物理与信息技术学院, 北京 100083;4. 中国地质科学院矿产资源研究所, 国土资源部成矿作用和资源评价重点实验室, 北京 100037 |
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| 基金项目： | 中国地质调查局地质调查工作项目(1212011220243,1212011220244)和国家深部探测专项第3项目(SinoProbe-03),国家自然科学基金项目(41374057),教育部"新世纪优秀人才支持计划"和中央高校基本科研业务费专项资金资助. |
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| 摘 要： | 收集了安徽、江西、浙江、江苏、湖北和河南6个省的区域地震台网138个宽频地震台站以及中国地质大学(北京)在长江中下游成矿带布设的19个流动宽频地震台站的三分量背景噪声数据,利用背景噪声面波层析成像方法,获得了长江中下游成矿带及其邻区地壳三维剪切波速度结构和径向各向异性特征.首先获得了5~38s周期的瑞利波和勒夫波相速度,结果显示短周期(16s)的瑞利波和勒夫波相速度与研究区内的主要地质构造单元具有良好的相关性,但在中长周期(20~30s)瑞利波相速度显示大别造山带东部为明显低速特征,而勒夫波相速度并未表现出异常特征.研究区域地壳三维有效剪切波速度和径向各向异性结果显示:苏北盆地和江汉盆地上地壳都表现为低速和正径向各向异性特征,华北克拉通东南部也表现为正径向各向异性,这可能与盆地浅部沉积层的水平层理结构相关.大别造山带中地壳显示为弱的正径向各向异性,同时其东部下地壳显示为低剪切波速度和强的正径向各向特征,可能是由于其在造山后发生了中下地壳的流变变形,引起各向异性矿物近水平排列所导致的.长江中下游成矿带内的鄂东南和安庆—贵池矿集区中地壳弱的负径向各向异性可能是由于深部岩浆向上渗透时所产生的有限应力导致结晶各向异性矿物的垂直排列所引起的.整个长江中下游成矿带下地壳都表现出正径向各向异性特征,可能是由于在伸展拉张的构造作用力下,下地壳矿物的晶格优势水平排列所引起的.
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| 关 键 词： | 长江中下游成矿带 背景噪声层析成像 径向各向异性 |
| 收稿时间： | 2015-05-16 |
Crustal shear wave velocity structure and radial anisotropy beneath the Middle-Lower Yangtze River metallogenic belt and surrounding areas from seismic ambient noise tomography |
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| OUYANG Long-Bin,LI Hong-Yi,LV Qing-Tian,LI Xin-Fu,JIANG Guo-Ming,ZHANG Gui-Bin,SHI Da-Nian,ZHENG Dan,ZHANG Bing,LI Jia-Peng.Crustal shear wave velocity structure and radial anisotropy beneath the Middle-Lower Yangtze River metallogenic belt and surrounding areas from seismic ambient noise tomography[J].Chinese Journal of Geophysics,2015,58(12):4388-4402. |
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| Authors: | OUYANG Long-Bin LI Hong-Yi LV Qing-Tian LI Xin-Fu JIANG Guo-Ming ZHANG Gui-Bin SHI Da-Nian ZHENG Dan ZHANG Bing LI Jia-Peng |
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| Institution: | 1. Key Laboratory of Geo-detection (China University of Geosciences, Beijing), Ministry of Education, Beijing 100083, China;2. Earthquake Administration of Guangdong Province, Guangzhou 510070, China;3. School of Geophysics and Information Technology, China University of Geosciences, Beijing 100083, China;4. MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China |
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| Abstract: | The crustal anisotropy of the Middle-Lower Yangtze River region is critical for observation of crustal deformation and understanding its deep geodynamic process. In this paper, through analysis of Rayleigh waves and Love waves using empirical Green's functions estimated from ambient noise tomography, we continue our previous work of imaging isotropic shear velocity to study the crustal radial anisotropy beneath the Middle-Lower Yangtze River Metallogenic belt and its surrounding areas. The data include 14 months (from July 2012 to August 2013) three-component continuous ambient noise data recorded at 138 seismic stations of newly upgraded China Provincial Digital Seismic Networks (Anhui, Jiangxi, Zhejiang, Jiangsu, Hubei and Henan) and 19 temporary seismic stations deployed by China University of Geosciences (Beijing). Firstly, these phase velocity dispersion curves between 5 and 38 s periods are measured from those three-component cross-correlation functions for each interstation path by using the automatic time-frequency analysis method with phase-matched processing. Then the study area is divided into a 0.5°×0.5° grid to invert the Rayleigh and Love wave phase velocity distributions with the Occam inversion method. At short periods ( < 16 s), the Rayleigh and Love wave phase velocity maps both show clear lateral variations which correlate well with major geological structures and tectonic units in the study region. The basins show low velocities, including the Jianghan, Hehuai, Subei, Hefei and Nanyang basins, but the Dabie orogenic belt and the Lower Yangtze Craton show high velocity. At intermediate-to-long periods (20~30 s), it is noticeable that the eastern Dabie orogenic belt is featured with low velocity only on the Rayleigh wave phase velocity map. Finally, we determine the crustal shear wave velocity and radial anisotropy by inverting the local phase velocity dispersion curves of Rayleigh and Love waves. In the upper crust, strong positive radial anisotropy and low shear wave velocity are imaged in the southeast of the North China Craton, Subei and Jianghan basins. Due to thick sedimentary cover in these areas, this strong positive radial anisotropy at shallow depths can be interpreted in terms of the horizontally layered sedimentary with larger velocity in the horizontal than in the vertical direction. In the Dabie orogenic belt, the radial anisotropy is weakly positive in the middle crust. Meanwhile strong radial anisotropy and low velocity in the lower crust beneath the eastern Dabie orogenic belt is imaged. The anisotropy could be caused by sub-horizontal mica fabric due to rheological deformation in the deep crustal zones. In the middle crust of southeastern Hubei and Anqing-Guichi ore districts of the Middle-Lower Yangtze River metallogenic belt, the negative radial anisotropy may result from crystalized anisotropic minerals aligned vertically induced by finite strain associated with the vertical intrusion of deep magma. The most striking feature of our crustal radial anisotropy model is the strong positive radial anisotropy observed in the lower crust beneath the Middle-Lower Yangtze River metallogenic belt and southeastern North China Craton. We consider that the strong positive radial anisotropy beneath the metallogenic belt may mainly result from the sub-horizontal alignment of seismically anisotropic crustal minerals induced by the finite strain accompanying extension. |
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| Keywords: | Middle-Lower Yangtze River metallogenic belt Ambient noise tomography Radial anisotropy |
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