Ghost plumes hidden beneath Earth’s continents

Abstract

Mantle plumes are hot, buoyant upwellings that rise from Earth’s core-mantle-boundary (CMB) at ∼2890 km depth to the surface. As they ascend towards the lithosphere – our planet’s rigid outermost shell – decompression melting results in surface volcanism. In continental interiors, a thicker lithosphere restricts plume ascent and associated decompression melting. However, it remains uncertain whether limited continental volcanism implies few sub-continental mantle plumes. Here, we present inter-disciplinary evidence revealing the first clear example of an amagmatic “ghost” plume in eastern Oman – the Dani plume. Despite lacking present-day surface volcanism, this plume is robustly imaged using P- and S-wave arrival-time residuals from distant earthquakes, recorded by a dense regional seismic network. A positive thermal anomaly is further corroborated by a ∼14 depression of the 410-km discontinuity and a ∼20 km upward deflection of the 660-km discontinuity. The imaged low-velocity structure is overlain by positive present-day residual topography in a region enigmatically uplifted since the late Eocene (∼40 Ma). Our analyses of kinematic reconstructions demonstrate that asthenospheric flow associated with the Dani plume modified Indian-plate motion in the late Eocene, allowing us to bound the likely arrival time of this plume beneath the lithosphere. Besides offering an approach to identify hidden continental plumes, both at the present-day and via Earth’s geological record, our study suggests that CMB heat-flux estimates should be revised upwards, with implications for thermal and core evolution models.