New Data on the Genesis and Evolution of the Primitive Magmas of Mount Cameroon: Contribution of Melt Inclusions

Source:
By:Legrand Joseph Tchop, Pauline Wokwenmendam Nguet, Benjamin Ntieche, Victor Metang, Jacques Dili Rake, Merlin Isidore Teitchou, Jacqueline Vander Auwera, Georges Emmanuel Ekodeck, Charles Nkoumbou

DOI: https://doi.org/10.30564/jgr.v2i4.2308

Abstract:

Mount Cameroon is a Plio-Quaternary volcanic massif, without a central crater, made up of more than 140 pyroclastic cones. It is one of the active volcanoes of the Cameroon Volcanic Line. Mount Cameroon melt inclusions are found in microdroplets trapped in the early minerals (olivines) from the pyroclastic products. The analysis of these melt inclusions allowed us to find primitive liquids compared to lavas. Major elements study of the magmatic inclusions, trapped in the most magnesian olivines (Mg#84-86) of Mount Cameroon revealed “primitive” liquids of basanite and alkali basalt type with variable composition compared to the much more uniform basalts of the magmatic series of Mount Cameroon. The study of these trapped liquids shows that: (1) the original primitive lavas did not undergo the process of evolution by FC, but rather underwent fundamentally (or exclusively) the process of partial melting; (2) the emitted lavas, evolved essentially by FC; (3) the variations in the trace element contents of the primitive liquids directly reflect a variation in the rate of partial melting of a homogeneous mantelic source. The very high La/Yb ratios of the Mount Cameroon melt inclusions (> 20) characterize a garnet lherzolite source. Spectra of the melt inclusions show a negative anomaly or depletion in K, Rb and Ba as those of HIMU. The “primitive” liquids and lavas of Mount Cameroon represent a co-genetic sequence formed by varying degrees of partial melting of a source considered as homogeneous.

References:

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