Petro-geochemistry, Genesis and Economic Aspects of Mafic Volcanic Rocks in the West and Southern Part of The Mamfe Basin (SW Cameroon, Central Africa)

Abstract

Geologic prospecting, petrographic and geochemical analyses of mafic volcanic exposures in the west and southern part of the Mamfe Basin (SW Cameroon) distinguishes: basanites, picro-basalts, alkali basalts and tholeiitic basalts. They are relatively LREE-enriched, undersaturated, saturated or oversaturated due to presence or absence of normative nepheline, hypersthene or quartz. Basanites mainly form pillow-like lavas, and are aphyric or porphyritic. They have significant concentration of Ni (up to 387 ppm) and Ba (up to 436 ppm). These alkaline rocks cooled from less evolved mantle source magma. Picro-basaltic fragments exclusively found in the western part of the basin are Ni (up to 259 ppm) Ba (up to 2090 ppm) -enriched porphyritic, alkaline or subalkaline rocks. They also cooled from less evolved mantle source magma. Basalts form volcanoclasts, flow and dykes. They are aphyric or porphyritic, alkaline, transitional or subalkaline. Some of these rocks are Al-enriched. They crystallized from variably evolved mantle source magma within the Oceanic Island Basalt and Continental Rift Basalt tectonic settings.

U-Pb Zircon Age: Preliminary Data Evaluating the Earth History Recorded by Two Basement Rocks (Granitic Pegmatite and Mica-Schist) in Mamfe Basin (Sw Cameroon, Central Africa)

“…Alkaline, tholeiitic, and transitional basalts, basanites, and picro-basalts found in the west and southern part of the basin were mainly crystallized from less evolved mantle source magmas [38]. Those in the west (mainly basanite and picro-basalts) are alkaline to tholeiitic Ocean Island Basaltic rocks crystallized during post sedimentary tectonovolcanic activities [23,38].…”

“…Sedimentary rocks in the Mamfe Basin are locally cross-cut or overlain by undated volcanic to sub-volcanic rocks (basalts, phonolites, trachytes, basanites, and picro-basalts) [18,20,21,24,37,38]. Alkaline, tholeiitic, and transitional basalts, basanites, and picro-basalts found in the west and southern part of the basin were mainly crystallized from less evolved mantle source magmas [38].…”

Petro-Geochemistry, Genesis and Economic Aspect of Syenitic and Mafic Rocks in Mindif Complex, Far North Cameroon, Central Africa

“…The relative high content alumina, iron oxide, MgO and CaO in peridotgabbro than in gabbro also differentiate this tow rocks. The high Al 2 O 3 content in peridotgabbro is probably due to important plagioclase crystallization in this rock and could classify it as high-Al basaltic rock [50]; and, noted high Fe 2 O 3 and MgO contents in this same rock can be justified by the presence of high olivine. The other difference is that of specific elements (e.g., Cr, Ni, Cu, Sr, Zr, Ba and REE) higher in gabbro than in peridotgabbro (V, Sr, and Zn-enriched).…”

“…For [51], continental alkaline basaltic rocks are often enriched in trace elements relative to oceanic counterparts. The trace elements abundances in peridotgabbro (the only studied alkaline basaltic rock) are globally less than those in continental basaltic rocks presented in [50] and [51]. They can therefore be classified as oceanic alkaline peridotgabbro.…”

“…Peridotgabbro and gabbro are basaltic rocks crystallized from mantle source magma(s) in continental and oceanic settings. The study of a basaltic rock can elucidate the nature of the underlying upper mantle and even aspects of the composition of the lower mantle [27] [51]) and in the Mamfe Basin (qualified as high-Ba basaltic rocks: [50]). Slightly Ti-enrichment (a less mobile element) in peridotgabbro could be due to ilmenite crystallization in its source magma.…”