THE GEOMETRY AND STRUCTURAL ANALYSIS OF THE GOLD DEPOSITS OF CHIRANO MINE

Authors

  • Kwamina Ackun-Wood Chirano Gold Mines Ltd
  • Jerry S.Y Kuma University of Mines and Technology, UMaT, Tarkwa
  • Jerome Anabannye Yendaw University of Mines and Technology, Tarkwa

Keywords:

ductile, brittle-ductile, brecciated, Chirano Shear Zone, Chirano Lode Horizon.

Abstract

The Chirano Mine gold deposit is a typical example of a structurally controlled deposit developed along the Kumasi Basin and the Sefwi Belt margin structure. The area has undergone various regimes of structural deformations. Consequently, all the Chirano deposits are intimately associated with shears and faults along a single continuous structural corridor known as the Chirano Shear Zone (CSZ). The CSZ geometry has been categorised into three major zones namely: (i) Laminated veins in shears, (ii) Breccia and (iii) Ductile to brittle ductile zones. The shear veins trend NE-SW and N-S, are laminated and occur in the sheared fabric close to the footwall. Penetrative foliated zones varying from a few centimeters to several meters constitute the ductile to brittle ductile structures. Gold grades are much higher within this zone. Analysis of cataclasis intensity recorded in drill core confirms a semi brittle form of deformation within the mineralised domain. The CSZ has different orientations in dip and strike from the south of the mining lease to the north. The subtle changes in orientation are deposit dependent. The structure has a sinuous shape and tends to pinch and swell. The current geometry and the distribution of stratigraphy and orebodies at Chirano is a manifestation of the complex interplay of magmatic and hydrothermal events in the area.

Author Biographies

Kwamina Ackun-Wood, Chirano Gold Mines Ltd

Exploration  Dept

Jerry S.Y Kuma, University of Mines and Technology, UMaT, Tarkwa

Vuce Chancellor

Jerome Anabannye Yendaw, University of Mines and Technology, Tarkwa

Geological Engineering Dept

References

Allibone A., Teasdale J., Cameron G., Etheridge M., Uttley P., Soboh A., Appiah-Kubi J., Adanu A., Arthur R., Mamphey J., Odoom B., Zuta J., Tsikata A., Pataye F. and Famiyeh, S. (2002), “Timing and Structural Controls on Gold Mineralization at the Bogoso Gold Mine, Ghana, West Africaâ€, Economic Geology 97, pp. 949-969.

Allibone A., Hayden P., Cameron G. and Duku, F. (2004), “Paleoproterozoic Gold Deposits Hosted by Albite- and Carbonate-Altered Tonalite in the Chirano District, Ghana, West Africaâ€, Economic Geology 99, pp. 479-497.

Anon. (2008), “Chirano Gold Mine Geological Reportâ€, Technical Report REB001/08, pp. 5-10.

Anon. (2009), “Chirano Gold Mine Technical Reportâ€, Technical Report No. 05/09, pp. 8-10.

Barritt, S. D. and Kuma, J. S. (1998), “Constrained Gravity Models and Structural Evolution of the Ashanti Belt, Southwest Ghana, Journal of African Earth Sciences, Vol. 26, No. 4, pp. 539-550.

Condie, K. C. (1989), “Archean Crustal Evolutionâ€, Elsevier, Amsterdam 86 pp.

Dzigbodi-Adjimah, K. and Asamoah, D. N. (2004), “The Geology of the Gold Deposits of Prestea Gold Belt of Ghanaâ€, 90th Anniv. Conference, Ghana Geological Survey, pp. 3-15.

Eisenlohr, B. N. (1992), “Conflicting evidence on the timing of mesothermal and paleoplacer gold mineralisation in early Proterozoic rocks from southwest Ghana,West Africaâ€, Mineral Deposita, Vol. 27, pp. 23-29.

Eisenlohr, B.N. and Hirdes, W. (1992), The structural development of the early Proterozoic Birimian and Tarkwaian rocks of southwest Ghana, West Africa. J. Afr. Earth Sci., 14, pp. 313-325.

Kesse, G. O. (1985), The Mineral and Rock Resources of Ghana, A.A. Balkema, Rotterdam, 610 pp.

Ledru, P., Milesi, J. P., Vinchon, C., Johan, V., Marcoux, E. and Ankrah, P. (1988), “Géologie et gitologie de l’or des series birrimiennes du Ghanaâ€, BRGM report, 88AFO 122 GEO., 36 pp.

Leube, A., Hirdes, W., Mauer, R. and Kesse, G.O. (1990), “The Early Proterozoic Birimian Supergroup of Ghana and some aspects of its associated gold mineralisationâ€, Precambrian Research, vol. 46, pp. 139-165.

Milesi, J. P., Ledru, P., Feybesse, J-L., Dommanget, A., Marcoux, E., Prost,A., Vinchon, C., Sylvain, J. P., Johan, V., Tegyey M., Calvez, J.Y. and Lagny, P. H. (1989), “West African Gold Deposits in their lower Proteroic Lithostructural Settingâ€,Chronologique Researchezs Minieres 497, Editions of BRGM, Orleans, France, 96 pp.

Milesi, J. P., Ledru, P., Vinchon, C. and Marcoux, E. (1991),“The metallogeneetic relation between Birimian and Tarkwaian gold deposits in Ghanaâ€,Mineral Deposita, vol.26; pp. 228-238.

Pigois, J. P., Groves D. I., Fletcher, I. R., McNaughton N. J. and Snee L. (2003), “ Age constraints on Tarkwaian paleoplacer and lode-gold formation in the Tarkwa-Damang district, SW Ghanaâ€, Mineralium Deposita 38 pp. 695-714.

Woolford, A. (2007), “Akwaaba Geological Reportâ€, Unpublished Technical Report, pp. 10-12.

Downloads

Published

2016-12-20