The Mount Cameroon stratovolcano (Cameroon Volcanic Line, Central Africa): Petrology, geochemistry, isotope and age data

Abstract

International audienceMount Cameroon, a Plio-Quaternary stratovolcano, is the most important volcano along the Cameroon Volcanic Line, located at the boundary between the continental and oceanic lithosphere. Effusive, explosive and hydromagmatic eruptions were the three main types of volcanic activity. Mount Cameroon has a weakly differentiated alkaline series: mainly basanites, alkaline basalts, hawaiites, and mugearites. Mount Cameroon lavas are a typical alkaline series, characteristic of the interior of plates: high TiO$_2$ contents (2.4-3.7 wt.%), Na$_2$O between 2.9 and 5.2 wt.%, K$_2$O between 1.1 and 3.0 wt.%. Trace element patterns confirm the general evolution by fractional crystallization from a source in a mantle plume. Magmas beneath Mount Cameroon were generated at great depths from a garnet-lherzolite mantle, with an additional contribution from spinel-lherzolite, with small amounts (0.2-2 %) of melting. $^{40}$ K-$^{40}$Ar analyses have yielded ages of 2.83 to 0 Ma. The $^{87}$Sr/$^{86}$Sr ratios of mafic lavas are low (0.703198-0.703344), and $^{143}$Nd/ $^{144}$Nd ratios are intermediate (0.512851-0.512773), as typical of a mantle origin with a HIMU component. $^{206}$Pb/$^{204}$Pb, $^{207}$Pb/$^{204}$Pb and $^{208}$Pb/$^{204}$Pb ratios are respectively 18.8270-20.3911, 15.5999-15.6793 and 40.2093-38.6517