3D VTEM inversion for delineating sub-vertical shear zones in the West African gold belt

Magdel Combrinck; Leif H. Cox; Glenn A. Wilson

doi:10.1071/ASEG2012ab374

ISSN: 2202-0586
E-ISSN:

oa 3D VTEM inversion for delineating sub-vertical shear zones in the West African gold belt
Authors Magdel Combrinck^a, Leif H. Cox^b and Glenn A. Wilson^c
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^a Tau Geophysical Consultants, Calgary, , Canada, [email protected] ^b TechnoImaging, Salt Lake City, , USA, [email protected] ^c TechnoImaging, Salt Lake City, , USA, [email protected]
Publisher: Australian Society of Exploration Geophysicists
Source: ASEG Extended Abstracts, Volume 2012, Issue ASEG2012 - 22nd Geophysical Conference, Dec 2012, p. 1 - 4
DOI: https://doi.org/10.1071/ASEG2012ab374
- Published online: 01 Dec 2012

Abstract

Summary

Accurately delineating sub-vertical graphitic thrust faults and shear systems is one of the major strategies followed in West African gold exploration. Due to the dense vegetation and limited outcrops, airborne electromagnetic (AEM) surveys have been routinely flown for geological mapping. We present a case study for practical 3D inversion of VTEM data acquired in Ghana. The geology is very complex, and consists of carbonaceous shear zones containing multiple thrust faults. Certain types of gold mineralization are directly associated with the shear zones which manifest themselves as sub-vertical conductors. We compare results from 3D AEM inversion to those obtained from traditional AEM interpretation methods, including conductivity depth imaging, decay constant analysis, profile anomaly picking, Fraser filtering, and plate modelling. We show that even with no a priori information, 3D AEM inversion accurately delineates the sub-vertical conductors, and recovers the most accurate representation of the geology. Interpretations based on CDIs are shown to be unreliable.

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2012-12-01

2026-01-18

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References

Allibone, A., Teasdale, J., Cameron, G., Ethridge, M., Uttley, P., Soboh, A., Appiah-Kubi, J., Adanu, A., Arthur, R., Mamphey, J., Odoom, B., Zuta, J., Tsikata, A., Pataye, F., Famiyeh, S., and Lamb, E., 2002, Timing and structural controls on gold mineraliation at the Bogoso Gold Mine, Ghana, West Africa: Economic Geology, 97, 949-969.
Cox, L. H. and Zhdanov, M. S., 2007, Large-scale 3D inversion of HEM data using a moving footprint: 77th Annual International Meeting, SEG, Expanded Abstracts, 467-470.
Cox, L. H., Wilson, G. A., and Zhdanov, M. S., 2010, 3D inversion of airborne electromagnetic data using a moving footprint: Exploration Geophysics, 41, 250-259.
Griffis, R. J., Barning, K., Agezo, F. L., and Akosah, F. K., 2002, Gold Deposits of Ghana: Minerals Commission of Ghana, Accra.
Kesse, G. O., 1985, The Mineral and Rock Resources of Ghana: Balkema, Rotterdam.
Wilson, G. A., Cox, L. H., Hope M., and Zhdanov, M. S., 2011, Practical 3D AEM inversion – A case study from Golden Ridge, Tanzania: presented at GeoSynthesis, Cape Town.
Zhdanov, M. S., 2009, Geophysical Electromagnetic Theory and Methods: Elsevier, Amsterdam.

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Article Type: Research Article

Keyword(s): 3D; AEM; Ghana; inversion; VTEM

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