Major elements and lithostratigraphic study of the contact rocks of the Togo and the Dahomeyan formations in Ghana

M Nyarku, S. Y Ganyaglo, E. T Glover, Y Serfor-Armah

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DOI: 10.4236/ns.2011.38088                

Abstract

The thrust contact between the Togo and the Dahomeyan formations in Ghana is a lithotectonic boundary that exists between two major Precambrian formations which are of importance to geologists owing to the fact that Precambrian rocks in Ghana host almost all economic minerals and metals. The lithostratigraphy of the Togo-Dahomyan thrust contact rocks from a borehole in Kwabenya near Accra (the Capital of Ghana) has been studied and major crustal chemical elements assayed using Instrumental Neutron Activation Analysis (INAA) techniques. The results have revealed elemental compositions and the mineralogical make up of the lithostratigraphic units of these contact rocks and the general geology of the Togo and the Dahomeyan formations. The profile shows a thrust contact that exists between the Togo formations which are underlying the Dahomeyan formations. The Togo formations here are made mainly of quartzite in fresh schist and the Dahomeyan made of gneisses. In between these two major geologic formations are the rocks of the contact which are intercalation of quartzite and schist. The rocks are felsic with an average felsic index (F) of 85.74 and feldspar rich with K- (orthoclase) feldspars dominating the Dahomeyan rocks. Iron and titanium oxides are depleted with depth from 52 m depth below surface downward and potassium oxide was enriched with depth from 42 m below surface downward. Major mineral forming elements such as aluminum and calcium had varied levels in the Togo and in the Dahomeyan rocks.

Keywords

Dahomeyan; Togo; Contact Rocks; Elemental; Concentrations; INAA; Ghana

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Blay, P.K. (1982) Geology of 1/4 Field Sheets 184, 185 and 187, Ghana Geological Survey Bulletin, 45.
[2]	Kesse, G.O. (1985) The mineral and rock resources of Ghana, Balkema, Rotterdam, 32-41.
[3]	Wright, J.B. (1985) Geology and mineral resources of West Africa, Science, 58-59.
[4]	Mani, R. (1978) The geology of the Dahomeyan of Ghana. Geology of Ghana Project, Ghana Geological Survey Bulletin, 45.
[5]	Efa, E. and Muff, R. (2003-2005) Ghana Geological Survey Department, Field Mapping.
[6]	ORTEC (2002) Advanced measurement technology, Incorporated Part, 777800.
[7]	Amili, R. (1977) Internal structure and mineralogy of the Gloserheia granite pegmatite, Froland, Southern Norway, Norsk Geologisk Tidsskrift, 57, 243-262.
[8]	Nude, P.M., Shervais, J.W., Attoh, K., Vetter, S.K. and Barton, C. (2009) Petrology and geochemistry of nepheline syenite and related carbonate-rich rocks in the Pan-African Dahomeyan orogen, southern Ghana West Africa, Journal of African Earth Sciences, 55, 147-157. doi.org/10.1016/j.jafrearsci.2009.03.010
[9]	Muff, R. and Efa, E. (2006) Environmental and Engineering Geology for Urban Planning in Accra-Tema, Ghana Geological Survey Department Bulletin, 55.