华南中部地幔转换带厚度异常:海南地幔柱?

Mantle transition zone thickness anomaly at middle Southern China by receiver function:evidence for Hainan Plume

本文利用84个布设于华南中部地区的流动地震台站记录的239个远震地震事件的波形资料,通过接收函数方法得到了华南大陆中部地区的地幔410 km和660 km间断面起伏与地幔转换带厚度变化.结果表明在华夏块体下方转换带厚度明显减薄10~25 km,尤其是在南部靠近海岸线附近(23.7°N,114.5°E)存在一个直径约200 km的转换带厚度异常区域(减薄约25 km),可能揭示海南地幔柱在该处上涌穿透660 km间断面进入地幔,在地幔转换带向周围扩散,热的地幔物质穿过410 km间断面继续上涌,造成了华夏块体下方上地幔大范围的低速异常,以及在雷州半岛和沿岸造成大范围的新生代玄武岩活动.

We have presented the 410 km and 660 km mantle discontinuity structure and mantle transition zone(MTZ) thickness beneath the middle Southern China Block using seismic data recorded by 84 portable seismic stations in the region by receiver function method. We found that transition zone thickness beneath Cathaysia Block is thinned 10~25 km obviously, the MTZ thinned anomalously within an area approximately 200 km in diameter centered(23.7°N,114.5°E),where the Hainan mantle plume may upwell into upper mantle, the continuous upwelling of hot mantle materials resulted in a wide range of low velocity anomalies in the upper mantle beneath the Cathaysia Block(above 410 km), also a large range of Cenozoic basalts in Leizhou Peninsula and coastal areas.