Geochemistry and structural control of magmatism preceeding the modern Cameroon Line
Zusammenfassung der Projektergebnisse
Basalt dykes which cut the Precambrian basement occur in southern continental part of the Cameroon Volcanic Line (Bangangte, Dschang, Manjo areas) are of tholeiitic composition. Their SiO2 ranges from 46 to 50 wt.% and they have moderate Mg-ratios (53–59), medium TiO2 contents (1.48–2,05 wt.%) and flat to mildly enriched incompatible trace element patterns. Comparison of trace element patterns of representative Cenozoic basaltic rocks of the Cameroon Volcanic Line (Bana anorogenic complex, Mt. Bambouto, Adamawa Plateau basalts) with these dykes indicate that the latter are less LREE-enriched 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 composition, 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 Cameroon Line volcanism.
