Petrology, Geochemistry, and Geodynamic Implications of Basaltic Dyke Swarms from the Southern Continental Part of the Cameroon Volcanic Line, Central Africa

Abstract

Basaltic dyke swarms in the southern continental part of the Cameroon Volcanic Line (Bangangte, Dschang, Manjo areas) are tholeiitic in composition with 46 to 50 wt.% SiO 2 and have moderate Mg-numbers (53–59), medium TiO 2 contents (1.48–2,05 wt.%), and flat to mildly enriched incompatible trace element patterns. Comparison with trace element patterns of representative Cenozoic basaltic rocks of the Cameroon Volcanic Line (Bana anorogenic complex, Mt. Bambouto, Adamawa Plateau basalts) indicates that these dykes are less enriched in light REE and show different incompatible trace element ratios (La/Yb: 5.7 to 8.6; Zr/Nb: 7.6 to 12.0; Ba/Th: 87.7 to 93.3). The trace element patterns of the dykes and their Sr- and Nd- isotope compositions, however, are similar to those of the pre-Cenozoic volcanic rocks of the Benue Trough in Nigeria. Our data therefore suggest that these dykes represent the magmatic history related to the break-up of Africa and South America and are unrelated to the Tertiary volcanism of the Cameroon Line.