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Structural controls on granitoid-hosted gold mineralization and paleostress history of the Edikan gold deposits, Kumasi Basin, southwestern Ghana

  • Ghislain TourignyEmail author
  • Markos D. Tranos
  • Quentin Masurel
  • Oliver Kreuzer
  • Steffen Brammer
  • Kwaku Owusu-Ansah
  • David Yao
  • Thomas Hayford
Article
  • 102 Downloads

Abstract

The > 9 Moz total aggregate gold endowment at the Edikan mine, Kumasi Basin, Ghana, is contained within a cluster of orogenic gold deposits located along the Akropong fault zone. The granitoid-hosted orebodies at Edikan (e.g., AG2, AG3, Fobinso, Esuajah), essentially an interconnected mesh of gold-bearing quartz veins, formed during deformation event D3Edk, which postdates the penetrative regional D2Edk deformation. The gold-bearing quartz veins developed in, and adjacent to, N-S- and NW-SE-trending, low-angle thrust faults that crosscut lithological contacts and earlier formed, steeply dipping D2Edk faults. Our paleostress analysis shows that the D3Edk deformation, during which the mineralized fault system developed, was characterized by a WNW-ESE “hybrid” compression that evolved to a strike-slip regime. This progressive deformation is best described with the following stress regimes: WNW-ESE transpression-pure compression (T1) associated with low-angle thrusting, subsequent transpression-strike-slip (T2), and later strike-slip-transtension (T3) associated with steeply dipping strike-slip faulting. The bulk of the granitoid-hosted gold mineralization at Edikan is associated with two principal sets of gold-bearing quartz veins, including low-angle fault-fill veins controlled by thrusts and shallow dipping oblique-extension veins that developed during T1. The activation of the reverse and sinistral strike-slip faults led to the development of restraining jogs characterized by abundant shallow and steeply dipping gold-quartz veins with moderately NE-plunging ore shoots. The geometry of the mineralized fault-fracture meshes is consistent with fault-valve behavior in a horizontal compressive stress regime under sustained conditions of supralithostatic fluid pressures at low differential stress.

Keywords

Fault-fill vein Extension vein Orogenic faulting Orogenic gold Kumasi Basin Ghana 

Notes

Acknowledgements

The authors wish to thank all the staff from the mine geology and exploration departments at Edikan for their fruitful insight and discussions during the field work. The work presented here was initiated when the first author was employed with SEMS Exploration and benefited from discussion with former colleagues Simon Meadows Smith and John Coates. Doug Jones, Kevin Thompson, Eric Dontoh, Francis Azumah, Albert Mortey, Kwabena Asante, Sarfo Kantanka, and Gary Brabham are thanked for their insights and constructive discussions on the geology of Edikan. The authors also gratefully acknowledge Perseus Mining Ghana Ltd. for the assistance with field work logistics. Perseus Mining Ltd. is thanked for the permission to publish this work. We wish to gratefully acknowledge AMIRA International and its industry sponsors for their support of the WAXI-2 Project (P934A). L. Baratoux, O. Vanderhaeghe, and an anonymous reviewer are gratefully appreciated for their insightful and critical reviews that helped to improve the manuscript. We would also like to thank B. Lehmann and H. Frimmel for their excellent editorial assistance.

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Perseus Mining Côte d’IvoireAbidjanCôte d’Ivoire
  2. 2.Department of GeologyAristotle University of ThessalonikiThessalonikiGreece
  3. 3.Centre for Exploration TargetingThe University of Western AustraliaCrawleyAustralia
  4. 4.Corporate Geoscience GroupRockingham BeachAustralia
  5. 5.Economic Geology Research CentreJames Cook UniversityTownsvilleAustralia
  6. 6.SEMS ExplorationAccraGhana
  7. 7.Perseus Mining GhanaAccraGhana

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