Structurally Controlled Prospectivity Map of the Sefwi Volcanic Orogenic Belt of Ghana

Fareed Majeed, Isaac Dadzie, Gordon Foli, Kwaku Tekyi Kyeremeh

Abstract


In this study, datasets obtained from ground magnetic and electrical geophysical surveys were integrated with existing solid geology, structural lineaments to map out structures in the Sefwi Belt of Southern Ghana. The prospecting and exploration stages of mining involve long periods of investment with a high risk of failure. In view of that, prospecting for gold needs to be optimised and that requires choosing the right techniques that will enhance the success of the exploration projects. It is for this reason that this paper exploits the integration of geological, geophysical (magnetic and electrical) and structural dataset to produce a prospective map of the study area. Elrec Iris 10 channel Induced receiver and Geometrics 859 magnetometer were used for Induced Polarisation (IP) and Resistivity and Magnetic data acquisition respectively. The magnetic data obtained were corrected and enhanced using Reduced to pole (RTP), 1 vertical derivative and analytical signal filters. The outcome of the electrical resistivity and IP inversions indicated that depths ranging from 50 to 200 m suggest conductive and chargeable bodies. The low-resistivity zones coincided with sheared and altered acidic meta-sediments. The geophysical signatures obtained from the enhanced magnetic data and the electrical data showed that the study area is structurally complex with a few of the structures corresponding to D1 deformation and most structures corresponding to D2 deformation. The study resulted in better illuminating geological structures and lithological boundaries, and thus has demonstrated the worth of geophysical data as an enhancement tool in mapping possible geological structures that host hydrothermal gold mineralisation within the Sefwi volcanic orogenic gold belt of Ghana. Seven diamond drill holes were intuitively planned to test the hypothesised model and determine the depth of the resistive-chargeable anomalous units as well as litho-structural boundaries.

Keywords


Volcanoclastic, Birimian, Metavolcanic, Auriferous, Pole-dipole, Reduce-to-pole

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References


Baranov, V. (1957), “A new method for interpretation of aeromagnetic maps pseudo-gravimetric anomalies”, Geophysics, Vol. 22, pp. 359–383.

Baranov, V., and Naudy, H. (1964), “Numerical calculation of the formula of reduction to the magnetic pole”, Geophysics, Vol. 29, pp. 67–79.

Boyle, R. W. (1979), “The Geochemistry of Gold and Its Deposits”, Geol. Surv. Can. Bull. 280, 584 pp.

Briggs, I. C. (1974), “Machine contouring using minimum curvature”, Geophysics, Vol. 39, pp. 39–48.

Brodie, R. C. (2002), “Airborne and ground magnetics”, Geoscience Australia, pp. 33-45

deGroot-Hedlin, C. and Constable, S. (1990), “Occam's inversion to generate smooth, two dimensional models from magnetotelluric data”, Geophysics, 55 (12), pp. 1613-1624.

Dentith, M. and Mudge S. T. (2014), Geophysics for the Mineral exploration geoscientist, University Printing House, Cambridge CB2 8BS, United Kingdom, 516 pp.

Fon, A.N., Che V.B. and Suh, C.E. (2012), “Application of Electrical Resistivity and Chargeability Data on a GIS Platform in Delineating Auriferous Structures in a Deeply Weathered Lateritic Terrain, Eastern Cameroon”, International Journal of Geosciences. doi.org/10.4236/ijg.2012.325097

Loke, M. H. (2003), “Electrical Imaging Survey for Environmental and Engineering Studies”, A Practical Guide to 2-D and 3-D Survey. USM, Penang, Malaysia,

Griffis, R. J., Barning K., Agezo, F. L. Akosah, F. K. (2002), Gold Deposits of Ghana, Minerals Commision, Cantoments, Ghana, 438 pp.

Heureux, E. L., Ugalde, H., Qian, W., Milkereit, B., and Nasui, C. (2007), “An integrated geophysical study for orebody delineation”, CSEG Recorder. pp. 36–39.

Hinze, W. J., Von-Frese R. R. B. and_Saad_A. H. (2013), Gravity and magnetic exploration, Principles, Practices, and Applications, Cambridge University Press, 525 pp.

Kearey, P., Brooks, M. and Hill, I. (2002), “An Introduction to Geophysical Exploration Third Edition”, Osney Mead, Oxford OX2 0EL: Blackwell Science Ltd, 281 pp.

Kellogg, O. D. (1953), “Foundations of potential theory”, Dover Publications

Loke, M. H. (2003), “Electrical Imaging Survey for Environmental and Engineering Studies”, A Practical Guide to 2-D and 3-D Survey. USM, Penang, Malaysia,

Miller, H. G. and Singh, V. (1994), “Potential Field Tilt – a new concept for location of potential field sources”, Journal of Applied Geophysics, 32, pp. 213-217.

Milligan, P. R and Gunn, P. J. (1997), “Enhancement and presentation of airborne geophysical data”, AGSO Journal of Geology and Geophysics 17: pp. 63-75.

O’Connell, M. D. R. S. Smith, and M. A. Vall´ ee, (2005), “Gridding aeromagnetic data using longitudinal and transverse gradients with the minimum curvature operator”, The Leading Edge, 24, pp. 142–145.

Reeves, C. V. (2001), Aeromagnetic surveys, principles, practice and interpretations, Geosoft, 155 pp.

Sasaki, Y. (1992), “Resolution of resistivity tomography inferred from numerical simulation”, Geophysical Prospecting 40 (4), pp. 453-464.

Verduzco, B., Fairhead J. D., Green C. M. and Mackenzie C. (2004), “New insights into magnetic derivatives”, The Leading Edge, 22, pp. 116–119, doi:10.1190/1.1651454.


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