Abstract
The Bangangte area belongs to the Cameroon Volcanic Line. The volcanic rocks exposure in the area consist of fine microlitic porphiritic Basalts which still poorly surveyed. Petrographically, the studied rocks are made up of minerals like plagioclase, clinopyroxene, olivine phenocrysts and a lot of opaque minerals within a very fine grained matrice. The Bangangte basalts are quartz normative free and are olivine, Diopside, Hypersthene normative. Alkaline (Na2O + K2O) contents vary from 2.247% to 5.46%. These rocks are low-Mg basalts with the Mg# values vary from 42.86 to 45.95 which are characteristic of primitive mantle source. The studied rocks are alkali to transitional basalts with Nb/Y ratio>1.5. Chondrite normalized spider diagram pattern of REE shows uniform patterns with enrichment in LREE and a relative depletion in HREE. While MORB normalized spider diagram pattern of multi elements reveals a negative anomaly with K2O, with enrichement in LILE and depletion in HREE. The Eu anomalies are positive to nulle and are typical of alkali basalts. The Bangangte transitional alkali basalts were formed in intraplate setting of continental part of the CVL. They are the products of partial melting of about 13% of an asthenosphere made up of garnet peridotite. Geochemically, the studied basalts are similar to alkali basalts from Mount Bamenda.
Highlights
The West Cameroon region constitutes an integral part of the Cameroon Volcanic Line (CVL), which is a megastructure in central Africa oriented N30°E and extending ~ 2000km in a length and ~ 100km in width
We present the preliminary data of transitional to alkalic basalts from Bangangte area, this include detailed petrographic description and whole rock geochemical characterization with the aim to constraint the source of their magma; contribute to the knowledge database of the CVL
Source of magma and geotectonic context The Mg# values of Bangangté basalts which are
Summary
The West Cameroon region constitutes an integral part of the Cameroon Volcanic Line (CVL), which is a megastructure in central Africa oriented N30°E and extending ~ 2000km in a length and ~ 100km in width. In Cameroon the tertiary volcanism seems to be related to a regional fracture trending N30°E [1], reactivated during the tertiary volcanism, [2, 3, 4, 5]. Basaltic rocks of various affinities constitute the greatest proportion of exposed rocks in the west Cameroon where they form a series of plateau basalts on which numerous works have been done [6, 7, 8]. Basaltic rocks along the CVL are Alkaline, tholeiitic, and transitional with the alkali basalts been the most studied along the Cameroon Volcanic line [9, 10]. Subalkaline, tholeiitic rocks are enriched in Fe relative to Mg, compared to calc-alkaline rocks, while silica remains relatively the same [12]
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