Abstract

Mantle plumes are hot, buoyant upwellings that rise from Earth’s core-mantle-boundary (CMB) at ~2900 km to the surface. As they ascend towards the lithosphere – our planet’s rigid outermost shell – decompression melting results in surface volcanism, typically distant from plate boundaries. In continental interiors, a thicker lithosphere restricts plume ascent and associated decompression melting. However, whether limited continental volcanism implies few sub-continental mantle plumes remains uncertain. I present inter-disciplinary evidence revealing the first clear example of a new, magmatic “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. The imaged low-velocity structure is overlain by positive present-day residual topography in a region enigmatically uplifted since the late Eocene (~40 Ma). Analyses of kinematic reconstructions demonstrate that asthenospheric flow associated with the Dani plume modified the Indian-plate motion in the late Eocene, allowing for bounding the likely arrival time of this plume beneath the lithosphere. These findings imply that other “ghost” plumes are likely to exist on Earth, for example, beneath the magmatic topographic swells on the African continent. At the same time, there is strong evidence for their existence in the recent geological past. Besides offering an approach to identify hidden continental plumes, both at present and via Earth’s geological record, I suggest that CMB heat-flux estimates should be revised upwards, with implications for thermal and core evolution models. 

Biography

Dr. Simone Pilia graduated with a PhD from the Research School of Earth Sciences (Australian National University) in 2014, after which he moved to the Petroleum Institute in Abu Dhabi to work on a collaborative project with the University of Oxford. He then held an independent Marie Curie fellowship at the University of Cambridge, which followed an equally prestigious NERC independent fellowship. After four years at the University of Cambridge, he moved to the University of Milano-Bicocca in 2021 and joined KFUPM in early 2023.