华南中部地幔转换带厚度异常：海南地幔柱？
北京大学理论与应用地球物理研究所，北京 100871
南方科技大学海洋科学与工程系，广东深圳 518055
上海佘山地球物理国家野外科学观测研究站，上海 201602
国家自然科学基金项目(41890814, U1901602), 大洋“十三五”项目(DY35-G2-1-01), 广东省自然科学基金(2018A030310121)，深圳市海外高层次人才创新创业专项资金团队资助项目(KQTD20170810111725321)，中国地质科学院地质调查项目(DD20160082)资助
中图分类号:P315, P541
Department of Geophysics, Peking University, Beijing 100871, China
ShanghaiSheshan National Geophysical Observatory, Shanghai 201602, China
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.
图 1流动台站位置
流动台站位置
Figure 1.Position of portable seismic stations
Position of portable seismic stations
图 2研究使用远震事件分布
研究使用远震事件分布
Figure 2.Maps of teleseismic events used in the study
Maps of teleseismic events used in the study
图 3BD19台全部接收函数
BD19台全部接收函数
Figure 3.Receiver functions of BD19 station
Receiver functions of BD19 station
图 4接收函数叠加剖面图
接收函数叠加剖面图
Figure 4.Stack of receiver function profiles
Stack of receiver function profiles
图 5410 km、660 km间断面深度及地幔转换带厚度分布
410 km、660 km间断面深度及地幔转换带厚度分布
Figure 5.Maps of 410 km, 660 km discontinuity′s depth and thickness of mantle transition zone
Maps of 410 km, 660 km discontinuity′s depth and thickness of mantle transition zone
图 6海南地幔柱上涌示意图
海南地幔柱上涌示意图
Figure 6.Diagram of Hainan mantle plume upwelling
Diagram of Hainan mantle plume upwelling
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Position of portable seismic stations
Maps of teleseismic events used in the study
Receiver functions of BD19 station
Stack of receiver function profiles
Maps of 410 km, 660 km discontinuity′s depth and thickness of mantle transition zone
Diagram of Hainan mantle plume upwelling