Lithospheric Structure of the West and Central African Rift Zone

The West and Central African Rift System (WCARS) is a geologically complex region offering insights into continental rifting, magmatism, and lithospheric evolution. This thesis integrates geophysical, petrological, and thermal data to examine lithospheric structure, crustal composition, and thermal regime, addressing four key questions: WCARS’s structural framework, the origins of the Cameroon Volcanic Line (CVL) and Bangui Magnetic Anomaly (BMA), and the link between surface heat flow, crustal composition, and magmatism.

A 3D lithospheric model using gravity, seismic, and petrological data confirms WCARS’s passive origin and heterogeneity. Crustal thickness varies from 25 km in rift zones to 50 km in cratons, while lithospheric thickness ranges from 70 km in the Benue Trough to 250 km beneath cratons, highlighting tectonic inheritance in rift evolution.

The CVL likely formed due to edge-driven convection from WCARS’s V-shaped opening, creating magma chambers along pre-existing weaknesses. The BMA, analyzed via gravity and magnetic data, likely results from felsic and plutonic intrusions with strong remnant magnetization during Mesozoic rifting.

Heat flow variations show high heat flow in rift zones due to magmatism and radiogenic heat production, while low heat flow in cratonic regions reflects thick, insulating lithosphere.

This study enhances understanding of WCARS’s lithospheric structure, geophysical anomalies, and thermal evolution, emphasizing the value of integrated geophysical and petrological analysis for studying rift systems and lithospheric modification.

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