Probing the Impact of Multiple Upwellings on the African Mantle Transition Zone using Converted Seismic Phases


The African continent is largely void of recent subduction but is thought to be underlain by multiple distinct thermochemical upwellings that may originate below the mantle transition zone. Most notably, the African superplume, is widely considered to have caused the ~30Ma volcanism at the Ethiopian traps and uplifted plateaus of eastern Africa. Internal heterogeneity within the superplume below the mantle transition zone has not, as yet, been unambiguously observed, a feature predicted following studies of the south Pacific superplume. Further, numerous other distinct loci of Cenozoic volcanism throughout Africa are often linked to more localised upwellings, but this remains uncertain. Africa therefore presents an ideal setting to investigate the impact of thermochemical upwellings on the mantle transition zone to understand the dynamics of mantle upwellings in a continental setting. Key to better understanding these issues are localised short-wavelength observations from converted seismic phases. Here we present a new compilation of P-to-s receiver function stacks derived from publicly available seismograph networks across Africa from 1990 to the present day. We capitalise on a new high-resolution P-wave absolute velocity model for the African continent (Boyce et al., in prep.) to migrate our receiver functions to depth. Our consistent, continent-wide data processing and quality control procedure enables direct comparison between adjacent regions/tectonic environments. Our results will be used to constrain potential scatterers above the African LLSVP, within the superplume, and map discontinuity topography beneath Africa.