The Horizontal Loop Electromagnetic (HLEM) Response of Ifewara Transcurrent Fault,Southwestern Nigeria: A Computational Results

Authors

  • A. A. Adepelumi Department of Geology, Obafemi Awolowo University, Ile-Ife, Nigeria
  • O. B. Olayiwola Nigerian Defence Academy, Kaduna, Nigeria
  • D. E. Falebita Department of Geology, Obafemi Awolowo University, Ile-Ife, Nigeria
  • O. Afolabi Department of Geology, Obafemi Awolowo University, Ile-Ife, Nigeria
  • B. O Soyinka Terracon, Seattle, Washington DC, USA
  • J. Obokoh Sam Houston State University, Spring, Texas, USA

DOI:

https://doi.org/10.30564/jgr.v3i3.3146

Abstract

The need to accurately interpret geological models that approximate mineralized zones in a Basement Complex terrain necessitate the development of horizon loop electromagnetic method (HLEM) forward modeling solutions for such scenarios. The focus of the present work is on finding rapid forward modeling solutions for synthetic HLEM data as an aid in exploration for moderate to deep conductive mineral exploration targets.The main thrust is obtaining idealized HLEM models that are required for geological interpretation of the subsurface in such environment. The original HLEM equations developed by Wesley were extended to represent a horizontally stratified earth with a conductive approximated by shear zone. From these equations a computer program was written to calculate the HLEM responses for optimal conductor model with known values of coil separations (L), depth of burial (z) and angle of dip of the target.The thin conductive model was used because it is simple and suitable for different geological scenarios. The accuracy of the approximate forward solution has been confirmed for HLEM systems with various geometric ranges, frequencies and conductivities. Three models having varying overburden thickness, dip angle of target and source-receiver separation were used in the forward modeling. The effect of varying the dip angle,overburden thickness and coil separation was studied in all the three models used. The result obtained from the forward modeling showed that variation of the dip angle gave rise to changes in the amplitudes of the anomalies generated, while that of overburden and coil separation gave rise to changes in anomaly shape. Also, the geometry and position of the causative body were precisely delineated.

Keywords:

Mineralized, Conductor, Overburden, HLEM, Modeling, Basement complex

References

[1] Ward, S. H., and Gledhill, T., (1957), Electromagnetic Surveying-ground methods, in Methods and case histories in mining geophysics: Bull. Can. Inst. Min.Metallurg., 63-70.

[2] Ward., S. H. and Hohmann., G. W. 1988. Electromagnetic Theory for Geophysical Applications, in Electromagnetic Methods in Applied Geophysics—Theory,” Society of Exploration Geophysicists,Tulsa, Vol. 1, 1988, pp. 131- 311.

[3] Spies, B. R., and Frischknecht, F. C., 1991. Electromagnetic sounding. In: Nabighian MN (ed) Electromagnetic methods in applied geophysics, Volume 2,Applications. Society of Exploration Geophysics.,Tulsa, 285-425.

[4] Wannamaker, P. E., Hohmann, G. W., and San-Filipo,W. A., 1984. Electromagnetic modeling of three-dimensional bodies in layered earths using integral equations. Geophysics, 49, 60-74.

[5] Newman, G. A., and Hohmann, G. W., 1988. Transient electromagnetic responses of high-contrast prisms in a layered earth. Geophysics, 53, 691-706.

[6] Lee, K. H., Liu, G., and Morrison, H. F., 1989. A new approach to modeling the electromagnetic response of conductive media. Geophysics, 54, 1180-1192.

[7] Xiong, Z., 1992. Electromagnetic modeling of three-dimensional structures by the method of system iteration using integral equations. Geophysics, 57,1556-1561.

[8] Wang, T. and Hohmann, G. W., 1988. ‘A finite-difference time-domain solution for three-dimensional electromagnetic modeling’, Geophysics, 58, 797-809.

[9] Mackie, R. L., Madden, T. R., and Wannamaker, P. E.,1993. Three-dimensional magneto-telluric modeling using difference equations. Geophysics, 58, 215-226.

[10] Torres-Verdín, C., and Habashy, T. M., 1994. Rapid 2.5-dimensional forward modeling and inversion via a new nonlinear scattering approximation. Radio Science, 29, 1051-1079.

[11] Zhdanov, M. S., and Fang, S., 1996. ‘Quasi-linear approximation in 3-D electromagnetic modeling’,Geophysics, 61, 646-665.

[12] Liu, E. H., and Lamontage, Y., 1998. Geophysical application of a new surface integral equation method for EM modeling. Geophysics, 63, 411-423.

[13] Mitsuhata, Y., 2000. 2-D electromagnetic modeling by finite-element method with a dipole source and topography. Geophysics, 65, 465-475.

[14] Sasaki, K., 2001. Full 3-D inversion of electromagnetic data on PC. Journal of Applied Geophysics, 46:,45-54.

[15] Hohmann, G. W., 1988. Numerical Modelling for Electromagnetic methods in geophysics in Nabighian, M. N., Ed., Electromagnetic methods in geophysics, Vol. 1, Soc. Explorations Geophysics. 313-363.

[16] Wesley, J. P., 1958. Response of a dike to an oscillating dipole. Geophysics, 23 (1), 128-133.

[17] Parasnis, D. S., (1971), Analysis of some multi-frequency, multiseparation electromagnetic surveys:Geophysical Prospecting, 19, 163-179.

[18] Telford, W. M., Geldart,L.P., Sheriff, R.E and Keys,D. A., 1976. Applied Geophysics, Cambridge University Press, 250 - 270.

[19] Palacky, G. J., Ritsema, I. L., and De Jong, S. J.,1981. Electromagnetic prospecting for groundwater in Precambrian terrains in the Republic of Upper Volta: Geophysical Prospecting, 29, p.932-955.

[20] Adepelumi, A. A., Ako, B. D., Ajayi, T. R., Olorunfemi, A. O., Awoyemi, M. O and Falebita. D.E.,2008. Integrated geophysical mapping of the Ifewara transcurrent fault system, Nigeria. Journal of African Earth Sciences, 52 (4-5), 161-166.

[21] Akinde., A. S., Adepelumi, A .A and Dikedi., P.N., 2019. IFEWARA MYLONITE: Identifying the Neo-Tectonic Overprint Using Integrated Geophysical. Journal of Geology and Geophysics, 8 (2) 458, 1-12.

[22] A Ako, B.D., Ajayi, T.R. and Alabi, A.O. (1978): A geochemical study of Ifewara area. Journal of Mining and Geology, Vol. 15(2), pp. 85 - 90.

[23] De Swardt, A.M.J. (1953): The geology of the country around Ilesha.Geological Survey of Nigeria, Bulletin. No. 23, pp 1-54.

[24] Elueze, A. A. (1982). Metallographic studies of ore minerals in the amphibolites of llesha Schist belts,southwestern Nigeria. Nigerian Journal Mining Geology, 19, 53-58.

[25] Turner, D.C. 1983. Recent advances in the study of the basement Complex of Nigeria. In: Oluyide P.O.,et. al. (Eds). Precambrian Geology of Nigeria. Geology survey of Nigeria, 11 - 43.

[26] 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 - 41.

[27] Caby R., and Boesse J.M., (2001), Pan-African nappe system in southwest Nigeria: the Ife-llesha schist belt. Journal of African Earth Sciences, Vol 33,2, 21 l-225.

[28] Frischknetch, F. C., Labson, V. F., Spies, B. R., and Anderson, W. L., 1991. Profiling Methods Using Small Sources: Electromagnetic Methods in Applied Geophysics, Vol. 2, Application, Parts A and B, 105-270.

[29] Dondurur, D., and Sari, C., 2004. A Fortran 77 Computer Code for Damped Least-squares Inversion of Slingram Electromagnetic Anomalies over Thin Tabular Conductors: Computers and Geosciences, 30,591-599.

[30] Duckworth, K., Krebes, E.S., 1995. A Quickbasic program for the computation of the response of a thin tabular perfect conductor to a two coil horizontal coplanar electromagnetic prospecting system.Computers & Geosciences 21 (2), 333-343.

[31] Duckworth, K., and O’Neil, D. A., 1989. Turam responses in a scale model conductive environment for single and paired conductors. Canada Journal of Exploration Geophysicists, 25. 115-137.

[32] Duckworth, K., Calvert, H.T., Juigalli, J., 1991. A method for obtaining depth estimates from the geometry of Slingram profiles. Geophysics, 56 (10), 1543-1552.

[33] Joshi, M. S., Gupta, O. P and Negi, J. G., 1988. On the effects of thickness of the half-plane model in HLEM induction prospecting over sulphide dykes in a highly resistive medium. Geophysical Prospecting,36, 551-558.

[34] Lowrie, W., and West, G. F., (1965), The effect of a conductive overburden on electromagnetic prospecting measurements. Geophysics, 30 (4), 624-632.

[35] Poddar, M., 1982. Interpretation of pulse EM anomalies over Gani conductors: Geophysical Prospecting.30, 86-100.

[36] McNeill, J. D., Edwards, R. N., and Levy, G. M.,1984. Approximate calculations of the transient electromagnetic response from buried conductors in a conductive half-space: Geophysics, 49, 918-924.

[37] Lilley, F. E. M., and Woods, D. V., 1978. The channeling of natural electrics by orebodies:Bulletin of Australian Society of Exploration Geophysics., 9, 62-63.

[38] Negi, J. G., Gupta, O. P., and Joshi, M. S., 1987. Corrections for conductivity estimates in induction prospecting of sulphide-dykes in a layered environment:Geophysical Prospecting, 35,718-734.

[39] Gupta, 0. P., Joshi, M. S., and Negi, J. G., 1980.Scale model electromagnetic response to inline and broadside systems at skew traverses of a dipping half-plane embedded in a conductive host rock: Geophysical Prospecting, pp.119-134.

[40] Hanneson, J.E., West, G.F., 1984. The horizontal loop electromagnetic response of a thin plate in a conductive earth: Part II—computational results and examples. Geophysics 49 (4), 421-432.

[41] Dondurur., D (2005), Depth Estimates for Slingram Electromagnetic Anomalies from Dipping Sheet-like Bodies by the Normalized Full Gradient Method:Pure and applied geophysics, 162,2179-2195.

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How to Cite

Adepelumi, A. A., Olayiwola, O. B., Falebita, D. E., Afolabi, O., Soyinka, B. O., & Obokoh, J. (2021). The Horizontal Loop Electromagnetic (HLEM) Response of Ifewara Transcurrent Fault,Southwestern Nigeria: A Computational Results. Journal of Geological Research, 3(3), 3–13. https://doi.org/10.30564/jgr.v3i3.3146

Issue

Vol. 3 , Iss. 3 (July 2021)

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Copyright © 2021 A. A. Adepelumi, O. B. Olayiwola, D. E. Falebita, O. Afolabi, B. O Soyinka, J. Obokoh

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