Basement Classification through Enhanced Magnetic Data Reductions in parts of Ekiti State, Southwestern Nigeria

Authors

  • Adedibu Akingboye Adekunle Ajasin University, Akungba-Akoko
  • Abimbola Ogunyele Adekunle Ajasin University, Akungba-Akoko

DOI:

https://doi.org/10.14419/ijag.v6i1.8573

Keywords:

Magnetic Reductions, Filtering, Basement, Structures, Depth.

Abstract

Enhanced magnetic data reductions via the use of various forms of filters were employed for basement classification in parts of Ekiti State. The data reductions and enhancement involve: reduction to equator (RTE), regional and residual, automatic gain control (AGC), downward continuation, upward continuations (1, 2, and 3 km), analytic signal (AS) and horizontal gradient (HG) to map and delineate basement rocks and structures, while surface relief and spectral plot were used to determine depth to top of magnetic sources. The images revealed that the study area is characterized by different lithologies. The rocks evinced lineaments and faults trending NE-SW (G–G’, H–H’, J–J’, K–K’), NNE-SSW, E-W (minor) and approximately N-S, while the dykes are in NW-SE, NNW-SSW directions. The analytic signal (AS) and horizontal gradient (HG) revealed high amplitude reversed Z-like shape as migmatite rocks, differentiating them from the two flanks with low amplitude signals as schist and quartzite schist of Ijero and Aramoko and the granitic intrusive within these migmatised rocks around Ijan, Gbonyin and Ise/Otun. The shaded relief and the spectral plot showed that the total depth to top of magnetic sources ranged from 20m to 1.8km for shallower and deeper sources respectively.

References

[1] Abraham, E. M., Lawal, K. M., Ekwe, A. C., Alile, O., Murana, K. A. and Lawal, A. A. (2014). Spectral analysis of aeromagnetic data for geothermal energy investigation of Ikogosi Warm Spring - Ekiti State, Southwestern Nigeria. Geothermal Energy, Springer Open Journal, vol. 26, pp. 1-21. https://www.geothermal-energy-journal.com/content/2/1/6.

[2] Ademilua, O. L. (1997). A Geoelectric and Geologic Evaluation of Groundwater Potential of Ekiti and Ondo States, Southwestern Nigeria, Unpublished M.Sc. Thesis, Department of Geology, Obafemi Awolowo University, Ile-Ife, Nigeria. pp. 1-67.

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

[4] Ansari, A. H. and Alamdar, K. (2009). Reduction to the Pole of Magnetic Anomalies Using Analytic Signal. World Applied Sciences Journal, vol. 7(4), pp. 405-409.

[5] Ayodele, O. S. (2013). Geology and Structure of the Precambrian Rocks in Iworoko, Are, and Afao Area, Southwestern, Nigeria. International Research Journal of Natural Sciences, vol. 1, no. 1, pp. 14 – 29.

[6] Bayowa, O. G., Olorunfemi, O. M., Akinluyi, O.F. and Ademilua, O. L. (2014). A Preliminary Approach to Groundwater Potential Appraisal of Ekiti State, Southwestern Nigeria. International Journal of Science and Technology, vol. 4, no. 3. pp. 48-58.

[7] Briggs I. C., (1974). Machine contouring using minimum curvature. Geophysics, vol. 39, pp. 39-48. https://doi.org/10.1190/1.1440410.

[8] Eze, C. L., Sunday, V. N., Ugwu, S. A., Uko, E. D., Ngah, S. A. (2011). Mechanical model for Nigerian intraplate earth tremors. Earthzine. http://www.earthzine.org/2011/05/17/mechanical-model-for-nigerian-intraplate-earth-tremors

[9] Fitzgerald, D., Yassi, N. and Dart, P. (1997). A case study on geophysical gridding techniques: INTREPID perspective. Exploration Geophysics, vol. 28, pp. 204-208. https://doi.org/10.1071/EG997204.

[10] Gunn, P., Maidment, D. and Milligan, P. (1997). Interpreting aeromagnetic data in areas of limited outcrop. AGSO Journal of Australian Geology and Geophysics, vol. 17, no. 2, pp. 175–185.

[11] Hsu, S., Sibuet J. C. and Shyu, C. (1996). High-resolution detection of geologic boundaries from potential field anomalies: an enhanced analytic signal technique. Geophysics, vol. 61, pp. 373-386. https://doi.org/10.1190/1.1443966.

[12] Hsu, S., Sibuet J. C. and Shyu, C. (1998). Depth to magnetic source using the generalized analytic signal. Geophysics, vol. 63, pp. 1947-1957. https://doi.org/10.1190/1.1444488.

[13] Jeng, Y., Lee, Y. L., Chen, C. Y. and Lin, M. J. (2003). Integrated signal enhancements in magnetic investigation in archaeology. Journal of Applied Geophysics, vol. 53, pp. 31–48. http://dx.doi.org/10.1016/S0926-9851.

[14] Jones, H. A. and Hockey, (1964). The Geology of part of’ Southwestern Nigeria. Nigerian Geological Survey, bulletin No, 31.

[15] 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, pp. 445.

[16] Luyendyk, A. P. J. (1997). Processing of airborne magnetic data. AGSO Journal of Geology and Geophysics, vol. 17, pp. 31-38.

[17] Mackey, T., Lawrie, K. Wilkes, P., Munday, T., de Souza K. N., Chan, R., Gibson, D., Chartres, C. and Evans, R. (2000). Paleochannels near West Wyalong, New South Wales: A case study in delineation and modelling using aeromagnetics. Exploration Geophysics, vol. 31, pp. 1-7. https://doi.org/10.1071/EG00001.

[18] MacLeod, I. N., Jones, K. and Ting Fan Dai, (1993). 3-D analytic signal in the interpretation of total magnetic field data at low magnetic latitudes. Exploration Geophysics, vol. 24, pp. 679-688. https://doi.org/10.1071/EG993679.

[19] Milligan, P. R. and Gunn, P. J. (1997). Enhancement and presentation of airborne geophysical data. AGSO Journal of Geology and Geophysics, vol. 17, pp. 63-75.

[20] MontajTM, (2004). Tutorial and help file on Two–Dimensional frequency domain processing of potential field data.

[21] Mudge, S. T. (1991). New developments in resolving detail in aeromagnetic data. Exploration Geophysics, vol. 22, pp. 277-284. https://doi.org/10.1071/EG991277.

[22] Nabighian, M. N. (1972). The analytic signal of two-dimensional magnetic bodies with polygonal cross-section: its properties and use for automated anomaly interpretation. Geophysics, vol. 37, pp. 501–517. https://doi.org/10.1190/1.1440276.

[23] Okpoli, C. and Akingboye, A. (2016a). Reconstruction and appraisal of Akunu–Akoko area iron ore deposits using geological and magnetic approaches.RMZ – Materials and Geoenvironment Journal, vol. 63. pp. 19-38.

[24] Okpoli, C. C. and Akingboye, A. S. (2016b). Magnetic, radiometric and geochemical survey of quarry sites in Ondo State, Southwestern Nigeria. International Basic and Applied Research Journal, vol. 2, no. 8, pp. 16-30.

[25] Okubo, Y., Matsushima, J., Correia, A. (2003). Magnetic spectral analysis in Portugal and its adjacent seas. Physics and Chemistry of the Earth, vol. 28, pp. 511–519. https://doi.org/10.1016/S1474-7065(03)00070-6.

[26] Okunlola, A. O., Akinola, O. O. and Olorunfemi, A. O. (2011). Petrochemical Characteristics and Industrial Features of Talcose Rock on Ijero Area, Southwestern Nigeria. Ife Journal of Science,vol. 13, no. 2, pp. 317 – 326.

[27] Oladapo, M. I. and Ayeni, O. G. (2013). Hydrogeophysical Investigation in Selected Parts of Irepodun/Ifelodun Local Government Area of Ekiti State, Southwestern Nigeria. Journal of Geology and Mining Research, vol. 5, no. 7, pp. 200 – 207. https://doi.org/10.5897/JGMR2013.0183.

[28] Oluyide, P. O., Udoh, A. N. (1989). Preliminary comments on the fracture systems of Nigeria. In: Ajakaiye, D. E., Ojo, S. B. and Daniyan M. A. (ed.)Proceedings of the national seminar on earthquakes in Nigeria. pp. 97–109.

[29] Omosanya, K. O., Ariyo, S. O., Kaigama, U., Mosuro, G. O., and Laniyan, T. A. (2015). An outcrop evidence for polycyclic orogenies in the basement complex of Southwestern Nigeria. Journal of Geography and Geology, vol. 7, no. 3, pp. 24-34. https://doi.org/10.5539/jgg.v7n3p24.

[30] 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.

[31] Rahaman, M. A. (1976). Review of Basement Geology of Southwestern Nigeria. In: Kogbe, C.A., (ed.) Geology of Nigeria. Rock View (Nig.) Limited, Jos, Nigeria. pp. 39-56.

[32] Rahaman, M. A. (1981). Recent Advances in the Study of the Basement Complex of Nigeria. First Symposium on the Precambrian Geology of Nigeria, Summary.

[33] Rahaman, M. A., Emofureta, W. O. and Vachette, M. (1983). The potassic-granites of the Igbeti area: further evidences of the polycyclic evolution of the Pan-African belt in Southwestern Nigeria. Precambrian Res., 22, pp. 75-92. https://doi.org/10.1016/0301-9268(83)90059-1.

[34] Rajagopalan, S. (1987). The use of automatic gain control to display vertical magnetic gradient data. Exploration Geophysics, vol. 18, pp. 166-169. https://doi.org/10.1071/EG987166.

[35] Rajagopalan, S. and Milligan, P. (1995). Image enhancement of aeromagnetic data using automatic gain control. Exploration Geophysics, vol. 25, pp. 173-178. https://doi.org/10.1071/EG994173.

[36] Roest, W. R., Verhoef, J. and Pilkington, M. (1992). Magnetic Interpretation using the 3D Analytic Signal, Geophysics, vol. 57, pp. 116-125. https://doi.org/10.1190/1.1443174.

[37] Ross, C. B. (2000). Airborne and Ground Magnetics. In: Papp, E. (ed.) Geophysical and Remote Sensing Methods for Regolith Exploration, CRCLEME Open File Report 144. pp. 33-45.

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

[39] Setyawan, A., Yudianto, H., Nishijima, J. and Hakim, S. (2015). Horizontal Gradient Analysis for Gravity and Magnetic Data beneath Gedongsongo Geothermal Manifestations, Ungaran, Indonesia. Proceedings World Geothermal Congress, Melbourne, Australia. pp. 1-6.

[40] Telford, W. M., Geldart, L. P., Sheriff, R. E., Keys, D. A. (1990). Applied Geophysics. Cambridge University Press. https://doi.org/10.1017/CBO9781139167932.

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

Downloads

Additional Files

Published

2017-12-01

Issue

Section

Articles