Mantle transition zone thickness beneath Cameroon: Evidence for an upper mantle origin for the Cameroon Volcanic Line

The thickness of the mantle transition zone beneath Cameroon has been mapped using data from the 2005-2007 Cameroon Broadband Seismic Experiment to evaluate models for the origin of the Cameroon Volcanic Line (CVL). Some 2200 receiver functions have been stacked using a 3-D velocity model, revealingP_sconversions from the mantle transition zone discontinuities at depths of ~410 and 660 km. Results yield a nearly uniform transition zone thickness (251 ± 10 km) that is similar to the global average, implying that any thermal anomalies in the upper mantle beneath the CVL do not extend as deep as the transition zone. This finding, when combined with regionalPandSvelocity models of the mantle, supports an explanation attributing the origin of the CVL to upper mantle processes such as an edge flow convection cell in the upper mantle along the northwestern side of the Congo Craton lithosphere.