| Popis: |
Hot mantle plumes, the thermo-chemical instabilities rising from Earth’s deep mantle, are believed to form large, round heads, followed by narrow tails. The impact of a plume onto the continental lithosphere causes uplift, rifting, and flood basalt volcanism. The resulting large igneous provinces (LIPs) are thought to be emplaced rapidly above the plume head as it arrives and spreads, as a circle, beneath the plate. However, LIP eruptions often span up to tens of millions of years in time and are scattered unevenly over areas a few thousand kilometres across, which is inconsistent with this conventional view. Here, we use seismic waveform tomography and obtain clear images of interconnected corridors of hot, partially molten rock beneath the areas of uplift and volcanism in the East Africa-Arabia region. The spatial continuity of the hot rock corridors and the temporal continuity of the volcanism since ~45 million years ago suggest that we are witnessing an extant, integral plume head that was morphed into a three-pointed star by the topography of the lithosphere-asthenosphere boundary. Eruption ages and plate reconstructions indicate that the plume head spread south-to-north, and tomography shows it being currently fed by three upwellings beneath Kenya, Afar, and Levant. Star-shaped plume heads within thin-lithosphere valley systems can account for the enigmatic dispersed and protracted volcanism in LIPs and are, probably, an inherent feature of plume-continent interaction. |
