Mantle Transition Zone Beneath Hainan Island and Its Surrounding Areas Revealed by Receiver Function Analysis

Abstract Investigating the structure of the mantle transition zone (MTZ) can provide significant insights into the origin and morphology of the Hainan mantle plume. In this study, we employ the receiver function (RF) method to map the 410 and 660 km discontinuities and the MTZ thickness beneath Hainan Island and its adjacent areas. We obtain 42,786 high‐quality RFs from 2,581 teleseismic events recorded at 132 broadband seismic stations from a newly deployed portable HAVESArray and Chinese provincial networks. After corrections using a 3‐D velocity model, our results show that the average depths of the 410 and 660 km discontinuities beneath Hainan Island and its surrounding areas are 419 ± 6 km and 660 ± 7 km, respectively. The average MTZ thickness is 239 ± 9 km, thinner than the global average of 250 km. There are two long northeast‐trending MTZ thinning zones. One is from the Hainan volcanoes, which is consistent with the hotspot track, whereas the other is 150–200 km east of the Pearl River Mouth Basin. These MTZ thinning zones, combined with low‐velocity anomalies within the MTZ, suggest that the Hainan mantle plume originates from the lower mantle and that the plume is not directly situated beneath the volcanic zone of Hainan Island, but northeast of the Leizhou Peninsula.