Geochemistry of Pegmatites associated with the cape coast granite complex in the Egyaa and Akim Oda areas of southern Ghana

The Cape Coast granite complex, which is associated with  metasedimentary rocks of the Birirmian in Ghana, is characterised by various minor intrusions that include pegmatites. The pegmatites, which are feldspar-rich, occur within, and at the margins of the granite batholiths and the surrounding schists. The major and trace element compositions of the pegmatites sampled from Egyaa and Akim Oda areas have been determined. The data indicates that the pegmatites from these areas have granitic compositions. The rocks are medium-K to high-K, calc-alkaline, S-type granitoids that are peraluminous and magnesian. Lower values of molar CaO/ (MgO + FeO <sub>tot</tot>) coupled with higher values of molar Al<sub>2</sub>O<sub>3</sub>/(MgO + FeO<sub>tot</sup>) suggest their derivation from partial melting from metapelitic sources, with the Birimian metasedimentary rocks being the likely source material. The rocks are depleted in Rb, Ba, Nb, Ce and Ti but rich in U, K, La, Hf and Y relative to primitive mantle. The data suggest that the pegmatites from these areas are late orogenic, and were emplaced at upper to middle crustal levels in a volcanic arc geotectonic environment

Assessment of the energy recovery potentials of solid waste generated in Akosombo, Ghana

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Geochemistry of lower proterozoic greywackes from the Birim diamondiferous field, Ghana

The Birim Diamondiferous field from which most of the alluvial diamonds are recovered is underlain by Lower Proterozoic Birimian metasedimentary and associated mafic rocks. Bulk rock geochemistry was carried out on the sandstones from the metasedimentary rocks to constrain the tectonic setting during the early Proterozoic. Bulk rock geochemical studies on greywackes show that they are characterized by moderately low but variable SiO2 contents, generally high Al2O3 and ferromagnesian element (e.g., Fe, Mg, Cr, V, Co, Sc) contents, and K2O/Na20 commonly less than 1. The geochemical data indicate that the greywackes were deposited in an active continental margin environment. The detritus were mainly derived from the upper continental crust but with an admixture of mafic component. Recent studies have shown that some of the mafics/ultramafics are diamondiferous metakimberlites. The inferred tectonic (arc) setting makes the emplacement of the so-called Proterozoic diamondiferous metakimberlites unlikely, if we are to go by the Clifford's Rule. However, if these ultramafic rocks are really metakimberlites and the source of the diamonds, then the Clifford's Rule may not be applicable in the Ghanaian situation, and the Birim field may be one of the few exceptions to this general rule. This would, then, present a typical example of subduction zone related diamondiferous kimberlites. Keywords: Birim Diamondiferous field, Birimian, geochemistry, Ghana, tectornc settingAfrican Journal of Science and Technology Vol. 5(2) 2004: 9-1

Separation of Radioactive Elements from Ethiopian Kenticha Pegmatite Ore by Hydrometallurgical Methods

The leaching and extraction behavior of uranium and thorium from a high-grade Ethiopian pegmatite ore in a mixture of hydrofluoric acid and sulfuric acid has been investigated. The effects of variables such as the temperature, particle size, acid concentration, and leaching time were studied. The leaching efficiency of uranium increased with increasing temperature to 150°C, at which 96% removal of uranium was achieved. Particles in the size range of − 100 + 75 μm resulted in the highest leaching of uranium, while formation of a colloidal suspension was observed when using a fine particle size fraction (− 75 μm). The dissolution of uranium increased with increasing leaching time. No significant systematic dependence of the leachability of thorium on the above variables was observed. Optimum extraction of uranium and thorium using D2EHPA was obtained when using aqueous/organic phase volume ratio of 1:1, solvent concentration of 0.3 M, and contact time of 20 min