地震波成像揭示云南省的热液活动和成矿环境

Hydrothermal activity and metallogenic environment revealed by seismic wave tomography in Yunnan Province,China

采用双差定位层析成像方法揭示S波速度结构,显示大规模低速异常主要集中在10~25km深度的小江断裂带和丽江-小金河断裂带周围;而在川滇块体中南部区域存在一个明显的高速异常,这与峨眉山大型火成岩省分布区域范围一致。根据地质和地球物理资料,推断小江断裂带和丽江-小金河断裂带下的低速异常与来自青藏高原中部的下地壳流动有关。然而,峨眉山地区中部存在明显的高速异常,与峨眉山大型火成岩区一致。峨眉山下方的与地幔柱相关高速异常会阻碍地壳流动,从而使得地壳流被限制在深大断裂带附近。结果还发现多种矿产资源主要集中在大型断层和低速带上,表明下地壳流动和大型深部断层为流体成矿和矿床沉积提供了条件。

S-wave velocity structures are revealed using double-difference tomography,which shows large-scale low-velocity anomalies around the Xiaojiang and Lijiang-Xiaojinhe fault zones at 10-25 km depth.In contrast,an obvious high-speed anomaly exists in the center of Emeishan area,which is consistent with the Emeishan Large Igneous province.Combined with the geological and geophysical data,the low-velocity anomaly might relate to the lower crustal flow of central Tibetan Plateau.The high-velocity anomaly associated with mantle plume in Emeishan would obstruct the crustal flow and limit it around the large deep faults.Meanwhile,the results also show that many mineral resources are mainly concentrated on the major faults and low-velocity zones,indicating that the lower crustal flow and the large deep faults provide conditions for mineral fluids and minerals deposit.