Crustal structure of Namibia from P-wave receiver functions

Abstract:

In order to further explore the nature of Precambrian crust in Africa as well as the extensiveness of local mantle plume activity and pervasiveness of crustal modification, new estimates for crustal thickness and Vp/Vs have been obtained for Namibia. Previous studies have found anonymously high Vp/Vs ratios and excess crustal thicknesses in northern Namibia and attributed them to magmatic underplating produced by a mantle plume. However, the full extent of mantle plume activity and associated crustal modification beneath Namibia was not fully characterized because of spatially limited networks. In this study, 18 stations from the AfricaArray-Namibia 8A network, 2 stations from the AfricaArray AF network, and one station from the GSN IU network are used to model P-wave receiver functions using the H-k staking method and a joint inversion of receiver functions and Rayleigh wave group velocities. Preliminary results from northern Namibia agree with previous studies which found anonymously high Vp/Vs ratios associated with the Walvis Ridge and Etendeka flood basalts. However, anonymously high Vp/Vs ratios and crustal thickening has also been detected in central and southern Namibia, indicating that the influence of the Tristan hot spot on crustal structure, which formed the Etendeka basalts, may have been more extensive than originally thought, or alternatively that the Karoo magmatism may also have contributed to crustal modification in many parts of Namibia.