Aeromagnetic characterization of parts of Ondo and Ekiti States, Southwestern Nigeria

Aeromagnetic characterization of parts of Ondo and Ekiti States, Southwestern Nigeria

Omowumi Ademila

Department of Earth Sciences, Adekunle Ajasin University, Akungba Akoko +234, Nigeria

Corresponding Author Email: 
omowumi.ademila@aaua.edu.ng
Page: 
66-75
|
DOI: 
10.18280/eesrj.040303
Received: 
|
Accepted: 
|
Published: 
30 September 2017
| Citation

OPEN ACCESS

Abstract: 

Aeromagnetic data of Ikole Sheet 245 covering Ikole, Akoko and Kabba areas was studied with the aim of delineating subsurface geological structures towards detailed information on exploration, engineering construction and environmental assessment of the study area. The colour shaded Total Magnetic Intensity (TMI) was interpreted for anomalous zone, structural trends, lithological differentiation and closures. Reductions were made on Residual Field data produced. TMI map revealed high intensity amplitudes within 65 – 180 nT representing crystalline and undeformed basement rocks, -150 to -65 nT for very low magnetic amplitudes representing infilled weathered and non-magnetic materials. Regional lineament trends diagonally from NE-SW dividing the map into equal halves, normal faults trending N–S and a NW–SE trending ridge (intrusive granitic rock) between two large depressions in Akoko axis were seen on TMI map. The reduction to the equator (RTE) map showed that below lineament (Akoko to Kabba) and above lineament (Ikole) have high and low magnetic anomalies respectively. Upward continuation maps revealed rocks trend generally in NW–SE and identified structures as deep-seated. Tilt-angle Derivative (TDR) map showed extent of structures, NE–SW lineaments (R-R’) and phases of N–S trending normal fault (F-F’) to be over a wide area. The spectral depth analysis plot showed that shallow and deeper magnetic sources have an estimated depth of 140 m and 1.60 km respectively. This method has proved valuable in mapping basement structures and targeting suitable areas for groundwater exploration, metalliferous mineral deposits and delineates zones of faulting in bedrock of the study area.

Keywords: 

Aeromagnetic, Ikole Sheet, Magnetic Intensity, Geological Mapping, Depth to Magnetic Sources

1. Introduction
2. Geologic Setting of the Study Area
3. Materials and Methods
4. Results and Interpretation
5. Conclusion
Acknowledgement
  References

[1] Carmichael R.S. (1989). Practical Handbook of Phys-ical Properties of Rocks and Minerals, Boca Raton, Ann Arbor, CRC Press, Boston. 

[2] Physical properties of rocks: Fun¬damentals and principle of petrophysics, (1996). Schon J.H., Klaus H., Sven T. (Eds), Pergamon Press, London, p. 583.

[3] Lowrie W. (2007). Fundamental of Geophysics, Low Price Paper Back Edition, Cambridge University Press, Cambridge. pp. 229–306.

[4] Akanbi E.S., Fakoya A.D. (2015). Regional magnetic field trend and depth to magnetic source determination from aeromagnetic data of Maijuju Area, North Central, Nigeria. Physical Science International Journal, Vol. 8, No. 3, pp. 1-13. DOI: 10.9734/PSIJ/2015/21652

[5] Nabighian M.N., Grauch V.J.S., Hansen R.O., LaFehr T.R., Li Y., Peirce J.W., Phillips J.D., Ruder M.E. (2005). The historical development of the magnetic method in exploration, Geophysics, Vol. 70, pp. 33-61. DOI: 10.1190/1.2133784

[6] Armstrong M., Rodeghiero A. (2006). Airborne geophysical techniques in Aziz, Coal Operators’ Conference, University of Wollongong and the Australasian Institute Mining and Metallurgy, pp. 113-131.

[7] Oyawoye M.O. (1972). The basement complex of Nigeria, In African Geology, Dessauvagie T.F.J., Whiteman A.J. (Eds), Ibadan University Press, pp. 67-99.

[8] Rahaman M.A. (1981). Recent advances in the study of the basement complex of Nigeria, First Symposium on the Precambrian Geology of Nigeria, Summary.

[9] Woakes M., Ajibade C.A., Rahaman M.A. (1987). Some metallogenic features of the Nigerian Basement, Journal of Africa Science, Vol. 5, pp. 655-664.

[10] Ajibade A.C., Fitches W.R. (1988). The Nigerian Precambrian and the Pan –African Orogeny, Precambrian Geology of Nigeria, pp. 45-53.

[11] Oyinloye A.O. (2011). Geology and geotectonic setting of the basement complex rocks in southwestern Nigeria: Implications on provenance and evolution, Earth and Environmental Sciences, pp. 98–117. 

[12] Rahaman M.A., Emofurieta W.O., Cean-Vachette M. (1983). The potassic granite of Igbetti area. Further evidence of the polycyclic evolution of the Pan-African belt in Southwestern Nigeria, Journal of Precambrian Resources, Vol. 22, pp. 75-92.

[13] Ajibade A.C., Woakes M., Rahaman M.A. (1987). Proterozoic crustal development in Pan-African regime of Nigeria: In A. Croner (ed.), Proterozoic Lithospheric Evolution Geodynamics, Vol. 17, pp. 259-231.

[14] Jones H., Hockey R. (1964). Geology of parts of southwestern Nigeria, Geological Survey of Nigeria Bulletin, No. 31.

[15] Nigerian Geological Survey Agency (NGSA), (2009). Geological map of Nigeria, Map prepared by Nigerian Geological Survey Agency. 31, Shetima Mangono Crescent Utako District, Garki, Abuja.

[16] Briggs I.C. (1974). Machine contouring using minimum curvature, Geophysics, Vol. 39, pp. 39-48.

[17] Leu L.K. (1981). Use of reduction-to-equator process for magnetic data interpretation: Presented at the 51st Ann, Internat. Mtg., Sot. Exnl. Geonhv, Geophysics, Vol. 47, p. 445.

[18] Oasis MontajTM Tutorial, (2004). Two – Dimensional frequency domain processing of potential field data.

[19] Telford W.M., Geldart L.P., Sheriff R.E., Keys D.A. (1990). Applied Geophysics, 2nd edition, Cambridge University Press, Cambridge.

[20] Blanco-Montenegro I., Torta J.M., Garcia A., Arana V. (2003). Analysis and modeling of the aeromagnetic anomalies of Gran Canaria (Canary Islands), Earth and Planetary Science Letters, Vol. 206, pp. 601 616. DOI: 10.1016/S00128821X(02)01129-9

[21] Rabeh T. (2009). Prospecting for the ferromagnetic mineral accumulations using the magnetic method at the Eastern Desert, Egypt, Geophysical Engineering, Vol. 6, pp. 401-411. DOI: 10.1088/1742-2132/6/4/008

[22] Spector A., Grant F. (1970). Statistical models for interpreting aeromagnetic data, Geophysics, Vol. 35, pp. 293-302.

[23] Gunn P.J., Maidment D., Milligan P.R. (1997). Interpreting magnetic data in areas of limited outcrop, AGSO Journal of Australian Geology and Geophysics, Vol. 17, No. 2, pp. 175-185.

[24] Parasnis D.S. (1996). Principles of applied geophysics, 5th ed. Chapman Hall, London, p. 456.

[25] Fieberg F.C. (2002). Ground magnetic investigations for gold prospecting in Southwestern Nigeria, Presentation given at the 62nd Meeting of the German Geophysical Society, Hannover.

[26] Kearey P., Brooks M., Hill I. (2002). An Introduction to Geophysical Exploration. 3rd ed, Oxford: Blackwell Science, p. 262. 

[27] Salem A., Williams S., Fairhead J., Ravat D., Smith R. (2007). Tilt-depth method: a simple depth estimation method using first-order magnetic derivatives, The Leading Edge, Vol. 26, pp. 1502-1505. DOI: 10.1190/1.2821934