Lithospheric imaging in the west Africa craton using receiver function modelling

Abstract

Abstract Lithospheric structure beneath West African Craton (WAC) is presented in this study, with an aim to understand the oldest parts of the continent. The velocity structure, associated composition (felsic/intermediate/mafic) and nature of crust (sharp or flat) at depth provides the link between the age these formed and reworked in, formulating models of their evolution. This work using data from 8 broadband seismic stations, shows significant variation of crustal properties in the Precambrian WAC. The shear-wave velocity (Vs) at depth reveals 42-47 km thick crust of felsic-to-intermediate composition near the boundary of the Precambrian old lithosphere and ~39 km thick felsic crust in the cratonic interior. The thick crust near the margins is also synchronous with thick (~10-21 km) layer as lower crust with high Vs (4.0-4.3 km/s). Contrarily thin crust accommodates thin (~4-6 km) high Vs layer in the cratonic interior. This high velocity composition laminated as the base layer of crust is linked with evolution, from the time of lamination of high velocity base, to dissolving reworking and delamination over time until stabilisation and leaving a thin felsic crust. Upper mantle Vs is found to be similar to the other Precambrian cratons (≥4.5 km/s).