华南东南部上地幔远震P波速度结构及意义

Teleseismic P-wave velocity structure of upper mantle beneath the southeastern part of South China and its implications

本研究利用114个固定台站记录的121个远震事件,以钦杭结合带为中心,采用天然地震层析成像构建了华南东南部上地幔P波速度结构模型。研究结果表明:(1)钦杭结合带、武夷成矿带以及南岭成矿带的深部结构存在着差异,说明3个成矿带经历了不同的构造演化过程;(2)江绍断裂的上地幔中存在着低速异常,推测该低速异常为从地幔过渡带或者下地幔上涌的热物质,与钦杭结合带和武夷成矿带的成矿作用有着密切的关系;(3)下扬子地区上地幔底部的高速异常可能为拆沉的岩石圈,而华夏板块上地幔顶部的高速异常则有待进一步研究。本研究的结果为认识华南东南部的深部结构提供了新的证据。

This paper determined a P-wave velocity structure of upper mantle beneath the southeastern part of South China, with the emphasis placed on the Qinhang Joint Belt, by using 121 teleseismic events received by 114 permanent seismic stations. The results show that:(1) the deep structures of the Qinhang Joint Belt, the Wuyi Metallogenic Belt and the Nanling Metallogenic Belt are different, suggesting that the tectonic processes of the three metallogenic belts are also different;(2) there exists a low velocity anomaly in the upper mantle beneath the Jiangshao Fault,suggesting that the upwelling of thermal flow probably originated from mantle transition zone or lower mantle, and might have been closely related to the mineralization in the Qinhang Joint Belt and the Wuyi Metallogenic Belt;(3) the high velocity anomaly at the bottom of the upper mantle beneath the Yangtze Block is probably the detached lithosphere;however, the high velocity anomaly beneath the Cathaysia Block should be further studied. These results provide new evidence for understanding deep structure about the southeastern part South China.