Petrology and Geochemistry of Basement Complex Rocks in Okom-Ita Area, Oban Massif, Southeastern Nigeria

Abstract

The determination of the mineralogical composition of rocks that underlie Okom-Ita area, in Oban Massif became necessary for the interpretation of the petrogenesis and protoliths of rocks in the area. Twelve representative rock samples were selected for thin section petrography and bulk rock geochemical analysis. The results reveal that the dominant intrusive rocks in Okom-Ita area are pegmatites, quartz veins and dolerites emplaced within gneisses, schists and phyllites host rocks. The quartz veins and pegmatites are leucocratic consisting predominantly of quartz, plagioclase and subordinate amount of Muscovites. The dolerite is dark grey, fine to medium grained and texturally ophitic and consists dominantly of pyroxenes, olivine and opaques. Three varieties of gneisses were recognized: feldspathic, banded and biotite gneisses. The gneisses, schists, and phyllites are dominated by SiO2 in the range of (60% - 75%). The rocks exhibit higher molecular concentration {Al2O3 > (CaO + Na2O + K2O)}, high alkali concentration with Na2O > K2O, high Al2O3 to alkali ratios and low TiO2, CaO and MgO concentrations. These distribution trends suggest a compensation for the high silica and alumina concentrations and support a granitic protolith for the pegmatites and their host gneisses and schists. The dolerites and amphibolites are impoverished in SiO2, but relatively enriched in lime and alkali oxides. Plots in the AFM, TiO2-K2O-P2O5 and Na2O/Al2O3-K2O/Al2O3 diagrams show that the pegmatite was derived from calc-alkaline magmatic source, while the dolerite was derived from tholeiitic basalt magma.

Share and Cite:

Opara, K. , Obioha, Y. , Onyekuru, S. , Okereke, C. and Ibeneme, S. (2014) Petrology and Geochemistry of Basement Complex Rocks in Okom-Ita Area, Oban Massif, Southeastern Nigeria. International Journal of Geosciences, 5, 394-407. doi: 10.4236/ijg.2014.54038.

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1] Kroner, A., Ekwueme, B.N. and Pidgeon, R.T. (2001) The Oldest Rock in West Africa: SHRIMP Zircon Age for Early Archaean Migmatitic Orthogneiss at Kaduna, Northern Nigeria. The Journal of Geology, 109, 399-406.
http://dx.doi.org/10.1086/319979
[2] Ekwueme, B.N. (1990) Rb-Sr Ages and Petrologic Features of Precambrian Rocks from the Oban Massif, Southeastern Nigeria. Precambrian Research, 47, 271-286.
[3] Ekwueme, B.N. (2003) The Precambrian Geology and Evolution of the Southeastern Nigerian Basement Complex. University of Calabar Press, Calabar, 1-57.
[4] Okezie, C.N. (1974) Geological Map of Nigeria, Scale 1:2,000,000. Geological Survey of Nigeria, Abuja.
[5] Odeyemi, I. (1982) A Review of the Orogenic Events in the Precambrian Basement of Nigeria, West Africa. Geologische Rundschau, 70, 897-909. http://dx.doi.org/10.1007/BF01820170
[6] McCurry, P. (1976) The Geology of the Precambrian to Lower Paleozoic Rocks of Northern Nigeria—A Review. In: Kogbe, C.A., Ed., Geology of Nigeria, Elizabethan Press, Lagos, 15-39.
[7] Ferre, E., Deleris, J.I., Lar, A.U. and Peuct, J.J. (1996) The Pan-African Reactivation of Eburnean and Archaen Provinces in Nigeria: Structural and Isotopic Data. Journal of The Geological Society (London), 153, 719-728.
[8] Burke, K.C. and Dewey, F.J. (1972) Orogeny in Africa. In: Dessauvagie, T.F.J. and Whiteman, A.J., Ed., African Geology, Ibadan University Press, Ibadan, 583-608.
[9] Black, R., Caby, R., Pouchkine, A., Bayer, B., Bertrand, J.M., Boullier, A.M., Fabre, J. and Lesquer, A. (1979) Evidence for the Late Precambrian Plate Tectonics in West Africa. Nature, 278, 223-227.
http://dx.doi.org/10.1038/278223a0
[10] Caby, R., Bertrand, J.M.I. and Black, R. (1981) Pan African Ocean Closure and Continental Collision in the HoggarIforas Segment, Central Sahara. In: Kroner, A., Ed., Precambrian Plate Tectonics, Elsevier, Amsterdam, 407-434.
[11] Ukaegbu, V.U. and Beka, F.T. (2007) Petrochemistry and Geotectonic Significance of Enderbite-Charnockite Association in the Pan-African Obudu-Plateau, Southeastern Nigeria. Journal of Mining and Geology, 43, 1-14.
[12] Rahaman, M.A., Ukpong, E.E.S. and Azmatullah, M. (1981) Geology of Parts of the Oban Massif Southeastern Nigeria. Journal of Mining and Geology, 18, 60-65.
[13] Ekwueme, B.N. (1983) Regional Metamorphism of Pellitic Rocks Southeast of Lokoja, Nigeria. Geology, 20, 71-77.
[14] Ekwueme, B.N. and Onyeagocha, A.C. (1985) Metamorphic Isograds of Uwet Area, Oban Massif Southeastern Nigeria. Journal of African Earth Sciences, 3, 443-454.
[15] Ekwueme, B.N. and Ekwere, S.J. (1989) The Geology of Eastern Section of Oban Massif, SE Nigeria. Journal of Mining and Geology, 25, 317-329.
[16] Ekwueme, B.N. (1993) An Easy Approach to Metamorphic Petrology. University of Calabar Press, Calabar, 169 p.
[17] Ekwueme, B.N. and Shilling, H. (1995) Occurrence, Geochemistry and Geochronology of Mafic-Ultramafic Rocks in the Obudu Plateau, SE Nigeria. In: Srivastava, R.K. and Chandra, R., Eds., Magmatism in Relation to Diverse Tectonic Setting, Oxford & IBH publishing Co. Pvt Ltd., New Delhi, 291-307.
[18] Niggli, P. (1948) Gesteine und Minerallgerstatten. Birkhauser, Basel, 540 p.
http://dx.doi.org/10.1007/978-3-0348-7171-6
[19] Ehlers, E.G. and Blatt, H. (1982) Petrology: Igneous, Sedimentary and Metamorphic. W. H. Freeman, New York, 732.
[20] MacDonald, G.A. and Katsura, I. (1964) Chemical Composition of Hawaiian Lavas. Journal of Petrology, 5, 82-133.
http://dx.doi.org/10.1093/petrology/5.1.82
[21] Winckler, H.G.P. (1967) Petrogenesis of Metamorphic Rocks. Springer-Verlag, New York, Inc., 237 p.
[22] Garrels, R.M. and Mackenzie, F.T. (1971) Evolution of Metasedimentary Rocks. Northern and Co., New York, 394 p.
[23] Leake, B.E. and Singh, D. (1986) The Delaney Dome Formation, Connemara, W. Ireland and the Geochemical Distinction of Ortho- and Para-Quartzofeldspathic Rocks. Mineralogical Magazine, 50, 205-215.
http://dx.doi.org/10.1180/minmag.1986.050.356.03
[24] Pearce, T.H., Gorman, B.E. and Birkett, T.C. (1975) The TiO2-K2O-P2O5 Diagram: A Method of Discriminating between Oceanic and Non-Oceanic Basalts. Earth and Planetary Science Letters, 24, 419-426.
http://dx.doi.org/10.1016/0012-821X(75)90149-1
[25] Obioha, Y.E. and Ekwueme, B.N. (2012) Geochemistry of Schists of Northwest Obudu Plateau, Southeastern Nigeria. Global Journal of Geological Sciences, 10, 157-165.
[26] Rajamani, V., Krogstad, E.J., Hanson, G.N. and Balakrishnan, S. (1987) Are Patna and Bisansttam Granites (Adjoining the Kolar Schist Belt) Cogenetic. Geological Society of India, 30, 98-105.
[27] Obioha, Y.E. and Ekwueme, B.N. (2011) Petrology and Chemical Composition of Gneisses of Northwest Obudu Plateau, Southeastern Nigeria. Global Journal of Pure and Applied Sciences, 17, 215-226.
[28] Oyawoye, M.O. (1972) The Basement Complex of Nigeria. In: Dessauvagie, T.F.J. and Whiteman, A.J., Eds., African Geology, University of Ibadan Press, Ibadan, 67-99.
[29] Ekwueme, B.N. and Onyeagocha, A.C. (1985) Petrology of Intrusive Rocks in Uwet Area, Oban Massif, SE Nigeria. Journal of Mining and Geology,, 22, 71-78.
[30] Cox, K.G., Bell, J.D. and Pankhurst, R.J. (1979) The Interpretation of Igneous Rock. Allen & Unwin, London, 450 p.
[31] Pettijohn, F.J. (1957) Sedimentary Rocks. 3rd Edition, Harper & Row, New York, 628 p.
[32] Eskola, P. (1920) The Mineral Facies of Rocks. Norsk Geologisk Tidsskrift, 6, 143-194.
[33] Turner, F.J. and Verhoogen, J. (1960) Igneous and Metamorphic Petrology. 2nd Edition, McGraw-Hill, New York, 694 p.
[34] Jahns, R.H. and Burnham, C.W. (1969) Experimental Studies of Pegmatites Gneiss: A Model for the Derivation and Crystallization of Granitic Pegmatities. Economic Geology, 64, 843-864. http://dx.doi.org/10.2113/gsecongeo.64.8.843
[35] Ekwueme, B.N. (1998) Geochemistry of Precambrian Gneisses of Obudu Plateau, Southeastern Nigerian. Global Journal of Pure and Applied Sciences, 4, 277-282.

Copyright © 2024 by authors and Scientific Research Publishing Inc.

Creative Commons License

This work and the related PDF file are licensed under a Creative Commons Attribution 4.0 International License.