P- and S-wave tomography of the Hainan and surrounding regions: Insight into the Hainan plume

- High-resolution 3-D Vp and Vs models beneath Hainan and adjacent areas are determined.
- The Hainan plume is characterized by a low-V and high-temperature anomaly.
- The low-V anomaly extends to below the mantle transition zone.
- The low-V anomaly zone exhibits a complex and deflected image toward the northeast.

High-resolution 3-D P- and S-wave velocity structures beneath Hainan and surrounding regions down to a depth of 700 km are determined using teleseismic tomographic inversion of 10,873 P and 9147 S relative arrival time residuals from 165 teleseismic events recorded by 88 permanent seismic stations belonging to three regional seismic networks of Hainan, Guangdong and Guangxi. The present tomographic models show that a low-velocity (low-V) anomaly extends below the transition zone (TZ) in and around the Hainan hotspot. The low-V zone does not exhibit a simple vertical columnar shape but a complex and deflected image toward the northeast. At depths of 13 to 170 km, the main low-V anomaly exists right beneath the Hainan hotspot, but in the depth range of 170 to 700 km, the low-V anomaly gradually deflects to the coastal area of Guangdong, which is to the northeast of the Hainan hotspot, an area with a diameter of approximately 200 km. I think that this area may be the extent of the Hainan plume from the deep upper mantle to the bottom of the TZ. On the basis of the present tomographic models, combined with the receiver function and geochemical results, I believe that the Hainan plume may originate from the low mantle, and is characterized by a high-temperature anomaly.