华夏地块中部宽频地震剖面深部速度结构研究
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本文为国家重点研发计划项目(编号2016YFC0600201)、国家自然科学基金项目(编号41630320、41974060)以及中央高校基本科研业务费等项目资助的成果。


Study on deep velocity structure along a broadband seismic profile below the middle part of the Cathaysia block
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    摘要:

    华夏地块处于欧亚板块、太平洋板块和菲律宾海板块相互作用的前沿。我国著名的南岭成矿带和武夷成矿带均位于华夏地块内。已有的研究认为,南岭和武夷的成矿作用可能与中生代晚期岩浆岩的底侵有关。为研究深部速度结构,本研究在2017年7月至2020年8月期间布设了一条横跨南岭成矿带与武夷成矿带的宽频地震测线。该测线共有81个流动台站组成,台站间距5~8 km,总长度约430 km。从连续波形中截取451个震级大于5. 5级的远震事件波形,利用改进的互相关法直接从波形中计算得到7231条相对走时残差数据(误差小于0. 1 s)。本研究采用远震走时层析成像方法反演相对走时残差数据,获得了高分辨率的速度结构。初步的成像结果表明:①华夏地块中部上地幔内存在一个明显的自西向东逐渐变深的低速异常体;②华夏地块岩石圈内速度结构具有很强的横向差异,且与断裂带分布存在一定的空间对应关系;③政和- 大浦断裂带东侧下方200~300km处存在较明显的高速异常体。结合其它已有成果,本研究认为上地幔内的低速异常可能是上涌的软流圈热物质,抵达岩石圈底部引发岩石圈拆沉,可能继续沿深大断裂侵入地壳,形成金属矿藏;而拆沉的岩石圈冷物质下沉,所留痕迹即为软流圈内的高速异常体。

    Abstract:

    The Cathaysia block is at the forefront of the interaction among the Eurasian, Pacific and Philippine plates. The Nanling metallogenic belt and the Wuyi metallogenic belt in China are located in this plate. Previous studies have suggested that Nanling and Wuyi mineralization may be related to magma underplating in late Mesozoic. In order to study the deep velocity structure, a natural earthquake observation line through the Nanling metallogenic belt and Wuyi metallogenic belt was set up from July 2017 to August 2020. The line consists of 81 mobile stations, each 5~8 km apart, with a total length of 430km. 451 teleseismic event waveforms with magnitude greater than 5. 5 were intercepted from the continuous waveforms, and 7231 relative travel time residual data (error less than 0. 1s) were directly calculated from the waveforms by using the improved cross- correlation method. In this study, a high resolution velocity structure is obtained by using teleseismic travel time tomographic imaging to invert relative travel time residual data. The preliminary results show that: ① In the middle part of the Cathaysia block, there is a low- velocity anomaly in the upper mantle which deepens gradually from west to east, which is presumed to be asthenosphere hot material; ② The velocity structure in the lithosphere of the Cathaysia block has a strong lateral difference and has a certain spatial correspondence with the distribution of the fault zone; ③ There is an obvious high- velocity anomaly located 200~300km below the eastern zhenghe- Taepu fault zone. Combined with other existing results, this study believes that the low- velocity anomaly in the upper mantle may be the upwelling asthenosphere hot material, which reaches the bottom of the lithosphere and causes lithospheric subsidence, which may continue to invade the crust along the deep and large faults and form metal mineral deposits. When the cold material in the lithosphere sinks, the trace is a high- velocity anomaly in the asthenosphere.

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席家骥,江国明,张贵宾.2021.华夏地块中部宽频地震剖面深部速度结构研究[J].地质学报,95(3):779-790.
XI Jiaji, JIANG Guoming, ZHANG Guibin.2021. Study on deep velocity structure along a broadband seismic profile below the middle part of the Cathaysia block[J]. Acta Geologica Sinica,95(3):779-790.

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  • 收稿日期:2020-10-05
  • 最后修改日期:2020-11-08
  • 录用日期:2020-11-18
  • 在线发布日期: 2021-03-23