Geology and Weathering Indices of the Bedrocks and Sediments in Okemesi -Ijero Area, Southwestern Nigeria


Author(s):
Ayodele Olusiji Samuel

Abstract:
Geological field mapping of the rocks in Okemesi-Ijero area were carried out at a scale of 1:50,000 to determine the underlying lithologic units and petrological characteristics. Also the suitability of the rocks and sediments for geochemical exploration purposes were determined using weathering indices parameters such as chemical index of weathering (CIW), weathering index of Parker (WIP), Plagioclase index of Alteration (PIA) and chemical index of Alteration (CIA). Thirty-five bedrocks and stream sediment samples were collected from various locations within the studied area using grid-controlled sampling techniques. Field studies revealed that the sediments were derived from weathering of the bedrocks such as quartz-biotite-schists, banded gneisses, granite-gneisses, biotite gneisses, calc gneisses, porphyritic granites, charnockites, massive/schistose quartzites and mica schists which are the dominant lithologic units in the studied area. The weathering profiles based on the above parameters showed that sediments from River Elewu and Issa 7c are weakly weathered whereas, sediments from Agbagbara, Ede-1, Ede-2, Effon-Okemesi-2, Esa-Oke-2, Odo-OWa Abidogun, Ofale road, Okemesi-2, 3 and 9 were intensely weathered which makes them unsuitable for geochemical exploration work due to complete weathering of the mineral grains.

Keywords:
okemesi, ijero, lithologic units, sediments, weathering indices

Download:
PDF
 
References:
  
1. Akintola, A.I., Ikhane, P.R., Bankole, S.I., Adeokurolere, D.N. (2013). Petrography and Stream sediment geochemistry of Ede and its environs, southwestern Nigeria. International Research Journal of Geology and Mining. 3(6):2276-6618.

2. Burke, K.C., Dewey, J.F. and Kidd, W.S.F. (1988). World distribution of  Sutures; the sites of former oceans. Tectonophysics. 40: 69-99.

3. British Geological Survey (BGS). (1990). Regional Geochemical Atlas: Argyll. British Geological Survey.

4. Darnley, A.G. (1990). International Geochemical Mapping: A new global project. Journal of Geochemical Exploration 39 : 1-13.

5. Dupuis, C, Hebert, R, Cote, VD, et al., (2006). ”Geochemistry of sedimentary rocks melange and flysch units south of the YarlungZangbo suture zone, southern Tibet”. Journal of Asian Earth Sciences 26: 489- 508.

6. Emmanuel, A. Ariyibi, Samuel., L. Folami, Bankole., D. Ako, Taye., R. Ajayi, Debowale.,O.   Adelusi (2011). Applications of the principal component analysis on geochemical   data; A case study in the basement complex of southern Ilesa area, Nigeria. Arab Journal of Geoscience 4: 239-247.

7. Fadipe, A.A (1988). Chemical composition of Niobium-Tantalite from granitic pegmatite and alkali granites (Egbe and Ijero mineralized region). Journal of Mining and Geology, 7: 42-47.

8. Fedo, C.M., Nesbitt, H.W., Young, G.M. (1995).”Unraveling the effects of potassium metasomatism sedimentary rock sand paleosols, with implications for paleoweathering conditions and provenance”. Geology, 23: 921- 924.

9. Harnois, L. (1988). The CIW index: A new chemical index of weathering. Sedimentary Geology, 55, 319-322.

10. Johnson, C.C., Breward, N., Ander, E.L., Ault, L.,( 2005). G-BASE: baseline geochemical mapping of Great Britain and Northern Ireland. Geochemistry: Exploration, Environment Analysis, 5 : 347-357.

11. Key, R.M., De Waele, B., Liyungu, A.K., 2004. A multi-element baseline geochemical database from the western extension of the Central African Copperbelt in north western Zambia. Applied Earth Sciences (Transn. Inst. Min. Metall. B), 113, 205–226.

12. McLennan, S.M. (1993). ”Weathering and global denudation”.  Journal of Geology, 101, 295- 303.

13. Mumbfu, E.M., Nforba, M.T., Cheo, E.S. (2014). Geochemical dispersion of gold in stream sediment in Paleoproterozoic Nyong Series, Southern Cameroon. Science Research. 2(6):155-165.

14. Nesbitt, HW, and Young, G.M.  (1982). Early Proterozoic climates and plate motions inferred from major element chemistry of lutites. Nature, 299, 715–717.

15. Oyinloye, A.O. and Adebayo O.F.(2005). Petrophysical and chemical properties of Calc-gneiss and clay deposit in Ijero-Ekiti area as industrial raw materials. Global Journal of Mechanical Engineering.  6 (1): 30-34

16. Olaolorun, O.O., Oyinloye, A.O (2010). Geology and geotechnical appraisal of some clay deposits around Ijero Ekiti, Southwestern Nigeria: Implication for Industrial uses. Pakistan  Journal of Science and Industrial Research. 53:  (3), 127-135.

17. Oyinloye, A.O. (1997). Physical and chemical characteristics of residual clay deposits in Ijero Ekiti. Journal Technoscience 1(1): 40-45.

18. Rahaman, M.A. (1988). Recent advances in the Study of the basement complex of Nigeria. In: Precambrian Geology of Nigeria. Geological Survey of Nigeria. 11-43.

19. Reimann, C. and Caritat, P. D., (1998). Chemical elements in the environment. Springer-Verlag, New York.31: 75-85.

20. Rice, K.C., (1999). Trace-element concentrations in streambed sediment across the contemporaneous United States. Environment Science and Technology., 33(15):2499-2504.

21. Watts, D.W. and Johnson, M.H., (2010). Geochemical mapping using stream sediments inwest-central Nigeria. Implications for environmental studies and mineral exploration  in west Africa. Applied geochemistry, 27 (6): 1035-1062.