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Contribution of melt inclusions to the origin and evolution of the primitive magmas of Mount Cameroon volcano

Pauline Nguet Wokwenmendam 1\, Legrand Joseph Tchop1,2, Caroline Ngwa Neh1, Eddy Mbossi1, Benjamin Ntieche3, Francois Mebara1,2, Merlin Isidore Teitchou1, Ateba Bekoa1

  • Affiliations: 1Centre for Geophysics and Volcanology Research, Institute for Geological and Mining Research, Buea, Cameroon; 2Department of Earth Sciences, Faculty of Sciences, University of Yaoundé I, Yaoundé, Cameroon; 3Department of Earth Sciences, Higher Teacher Training College, University of Yaounde, Yaoundé, Cameroon

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 225

  • Programme No: 1.1.11

  • Theme 1 > Session 1

Abstract

The Mount Cameroon volcano is fed by magmas that originate at depth from the partial melting of the mantle. The magmas are transferred through a network of reservoirs before eruption. Studies of the melt inclusions show they are primitive liquids compared with lavas; they are found in microdroplets trapped in the most magnesian olivines (Mg#84-86) of the pyroclastic products. The melt inclusions underwent the fundamental (or exclusive) process of partial melting, unlike the lavas, which evolved essentially by fractional crystallization and magma mixing. The very high La/Yb ratio > 20 is a geochemical signature of a deep garnet lherzolite source. Rare earth spectra show HIMU characteristics. Major elements show alkaline or tholeiitic trend; "primitive" basanites and alkaline basalt liquid of variable composition compared with lavas; most MgO content (7-11%) reflect those of magmas from partial melting of the mantle (MgO>8%). The equilibrium temperatures (1153-1315 (±20) °C) between the melt inclusions and their olivine host indicate melts of variable composition that were trapped over a wide range of temperatures. Thermobarometry studies corresponds to shallow magma pockets below or at the Moho level beneath the Mt. Cameroon. Melt inclusions and lavas studies indicate that "primitive" liquids and lavas represent a co-genetic sequence formed by varying degrees of partial melting of a primitive and metasomatised mantle model source. Mt. Cameroon is characterized by a complex-plumbing system, with secondary and shallower magmatic chambers nearer the Moho. Keywords: Primitive magma, Partial melting, Fractional crystallization, Alkali basalt, Mount Cameroon active volcano.