Abstract
Mount Etinde is a Recent (<1 Ma) strombolian-type volcano located on the southern flank of Mount Cameroon. Mount Etinde lavas are distinguished on the basis of the mineralogical compositions of their phenocrysts: olivine-pyroxene, olivine-melilite and clinopyroxene-nepheline. Some magnetite and ilmenite occur as inclusions in these early phases. Mafic mineral composition indicates that fractionation involved only limited Fe-enrichment. Oscillatory, normal and sectorial zoning in clinopyroxene relates to the differentiation and fractional crystallization of the magma. Based on the primitive mantle-normalized trace and rare earth element patterns, all nephelinites have high abundances of incompatible elements (103 < La < 281; 131 < Ce < 503), with negative anomalies for high field strength element Ti and low Nb/Y (0.1 - 0.2) and Rb/Y (<0.03) ratios, suggesting derivation from a similar source. Textural characteristics and mineral chemical data, as well as whole-rock compositions, suggest that the nephelinitic lavas may have been derived from basaltic magma from a heterogeneous lithospheric mantle. Geochemical modeling of major and trace element variations indicates that the Etinde lavas could not have been produced by only fractional crystallization. Pneumatolytic reaction probably affected the pyromagmas (basaltic magma composition) and was responsible for the nephelinite rocks at lower oxygen fugacity (fO2).
Highlights
Located near Batoke village (Figure 1), Mount Etinde is unique among the many volcanoes along the 1600 km long Cameroon Hot Line
We present new petrological, mineralogical and geochemical data on the main rock types of Mount Etinde, in order to describe the magmatic processes that led to their formation
Mineralogical, geochemical and trace elements are reported for the main nephelinite rocks on the Mount Etinde
Summary
Located near Batoke village (Figure 1), Mount Etinde is unique among the many volcanoes along the 1600 km long Cameroon Hot Line. They erupted at the very limit between the ocean and the continent, where fracturation (fractures at the continent-ocean boundary and regional N308E and N708E zones) is more intense and deeper [1]. We present new petrological, mineralogical and geochemical data (major and trace elements) on the main rock types of Mount Etinde, in order to describe the magmatic processes that led to their formation
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