Feedback between topography and lithosphere–asthenosphere dynamics beneath the Yerer‐Tulu Wellel volcano‐tectonic lineament: Insights from apatite thermochronology and basalt geochemistry

Abstract

Ethiopian topography is dominated by an ~2‐km high plateau that underwent uplift and incision after or during the Cenozoic Flood Basalt event in the Early Oligocene; however, the timing and drivers of plateau dynamics are poorly constrained. We constrain the onset and causal mechanism of plateau uplift using thermochronologic and basaltic geochemical techniques. We performed low‐temperature apatite fission track and (U–Th)/He thermochronologic dating on three Neoproterozoic basement rocks from the Yerer‐Tullu Wellel volcano‐tectonic lineament, directly west of Addis Ababa. Thermal models based on these results suggest this part of the plateau underwent slight heating in the Oligocene through Late Miocene, followed by rapid and recent cooling until the present day. To determine the nature of these Cenozoic thermal events, we compiled and reinterpreted a suite of partially published basaltic geochemical data. These geochemical data suggest this part of the plateau is underlain by a metasomatized and pyroxenite‐rich lower lithosphere that began to drip into the asthenosphere in the Miocene. Fault‐facilitated release of the lithospheric drip in the Late Cenozoic encouraged basin inversion, driving rapid cooling and incision within the last 5 Ma. Our study suggests that a direct coupling between lithospheric removal and topographic response highlights significant plateau formation around the Yerer‐Tullu Wellel volcano‐tectonic lineament zone within the Pliocene.