Rao B Padma, Kumar M Ravi
MoES-National Centre for Earth Science Studies, Govt. of India, Thiruvananthapuram, India.
CSIR-National Geophysical Research Institute, Hyderabad, India.
Sci Rep. 2025 Mar 29;15(1):10884. doi: 10.1038/s41598-025-94831-3.
The Réunion hotspot is the best example of a primary plume, manifested as intraplate-volcanism, a large igneous province and a geochemical anomaly. In this study, we investigate the mantle transition zone (MTZ) structure beneath the Réunion Island using 3D-migration of P-Receiver functions, to decipher the effect of the plume on the MTZ and its architecture. Results indicate a thin MTZ in the regions surrounding the Réunion, like Madagascar and its vicinity, eastern and south-eastern sides of the Réunion, suggesting high-temperature anomalies within, caused by the plume. Interestingly, we detect a depressed 410 km discontinuity exactly beneath the Réunion hotspot and a broader depression of 660 km discontinuity within and regions in its proximity. These maiden results shed-light on the high-temperature anomalies in the mid-mantle, probably sourced from the Réunion plume and provide evidence for the Majorite-garnet phase transformation at 660 km discontinuity. We postulate that an ascending Réunion plume has initially hit the 660 km discontinuity, got horizontally spread and further progressed to the 410 km discontinuity as a columnar structure.
留尼汪热点是原生地幔柱的最佳实例，表现为板内火山活动、大火成岩省和地球化学异常。在本研究中，我们利用P波接收函数的三维偏移成像，研究留尼汪岛下方的地幔过渡带（MTZ）结构，以解读地幔柱对MTZ及其结构的影响。结果表明，在留尼汪岛周围地区，如马达加斯加及其附近、留尼汪岛的东部和东南部，MTZ较薄，这表明地幔柱导致其内部存在高温异常。有趣的是，我们在留尼汪热点正下方探测到410千米间断面凹陷，在其内部及附近区域探测到660千米间断面更宽的凹陷。这些初步结果揭示了地幔中部的高温异常，可能源自留尼汪地幔柱，并为660千米间断面处的镁铁榴石相变提供了证据。我们推测，上升的留尼汪地幔柱最初撞击了660千米间断面，水平扩散，然后作为柱状结构进一步延伸至410千米间断面。
