Multigenetic Origin of the X‐Discontinuity Below Continents: Insights From African Receiver Functions

Constraints on chemical heterogeneities in the upper mantle may be derived from studying seismically observable impedance contrasts that they produce. Away subduction zones, several causal mechanisms are possible to explain intermittently observed X-discontinuity (X) at 230–350 km depth: coesite-stishovite phase transition, enstatite clinoenstatite and/or carbonated silicate melting, all requiring a local enrichment of basalt. Africa hosts broad range terranes, Precambrian cores Cenozoic hotspots with or without lowermost origins. With absence below margins African plate for >0.5 Ga, presents an ideal study locale explore origins X. Traditional receiver function (RF) approaches used map seismic discontinuities, such as common conversion-point stacking, ignore slowness information crucial discriminating converted phases surface multiples. By manually assessing depth and stacks 1° radius overlapping bins, normalized vote mapping RF is robustly assess spatial distribution phases. The X mapped beneath 233–340 depth, revealing patches heterogeneity proximal upwellings Afar, Canaries, Cape Verde, East Africa, Hoggar, Réunion further observations Cameroon, Madagascar, Morocco. There lack southern strikingly, magmatic eastern rift branch Rift. no relationships existing between amplitudes estimated temperatures, multiple required across continental geodynamic settings.