Geology, geodynamics and orogenic gold prospectivity modelling of the Paleoproterozoic Kumasi Basin, Ghana, West Africa Bijal Chudasama a, ⁎, Alok Porwal a,b , Oliver P. Kreuzer c,d , Kris Butera c a Centre of Studies in Resources Engineering, Indian Institute of Technology Bombay, Powai, 400076, India b Centre for Exploration Targeting, University of Western Australia, Crawley, 6009 WA, Australia c Corporate Geoscience Group, PO Box 5128, Rockingham Beach, WA 6969, Australia d Economic Geology Research Centre, James Cook University, Townsville, QLD 4811, Australia abstract article info Article history: Received 22 April 2015 Received in revised form 27 July 2015 Accepted 18 August 2015 Available online xxxx Keywords: West Africa Craton Ghana Paleoproterozoic Kumasi Basin Orogenic gold Mineral systems Prospectivity modelling Fuzzy inference systems This paper describes the geology and tectonics of the Paleoproterozoic Kumasi Basin, Ghana, West Africa, as applied to predictive mapping of prospectivity for orogenic gold mineral systems within the basin. The main objective of the study was to identify the most prospective ground for orogenic gold deposits within the Paleoproterozoic Kumasi Basin. A knowledge-driven, two-stage fuzzy inference system (FIS) was used for prospectivity modelling. The spatial proxies that served as input to the FIS were derived based on a concep- tual model of gold mineral systems in the Kumasi Basin. As a first step, key components of the mineral sys- tem were predictively modelled using a Mamdani-type FIS. The second step involved combining the individual FIS outputs using a conjunction (product) operator to produce a continuous-scale prospectivity map. Using a cumulative area fuzzy favourability (CAFF) curve approach, this map was reclassified into a ternary prospectivity map divided into high-prospectivity, moderate-prospectivity and low-prospectivity areas, respectively. The spatial distribution of the known gold deposits within the study area relative to that of the prospective and non-prospective areas served as a means for evaluating the capture efficiency of our model. Approximately 99% of the known gold deposits and occurrences fall within high- and moderate-prospectivity areas that occupy 31% of the total study area. The high- and moderate- prospectivity areas illustrated by the prospectivity map are elongate features that are spatially coincident with areas of structural complexity along and reactivation during D4 of NE–SW-striking D2 thrust faults and subsidiary structures, implying a strong structural control on gold mineralization in the Kumasi Basin. In conclusion, our FIS approach to mapping gold prospectivity, which was based entirely on the con- ceptual reasoning of expert geologists and ignored the spatial distribution of known gold deposits for prospectivity estimation, effectively captured the main mineralized trends. As such, this study also demon- strates the effectiveness of FIS in capturing the linguistic reasoning of expert knowledge by exploration ge- ologists. In spite of using a large number of variables, the curse of dimensionality was precluded because no training data are required for parameter estimation. © 2015 Elsevier B.V. All rights reserved. 1. Introduction The Birimian metavolcanic and metasedimentary successions of Ghana form part of the Paleoproterozoic West African Craton that also underlies much of Burkina Faso, Niger, Cote d'Ivoire, Mali, Sierra Leone, Liberia, Guinea, and Senegal. Some of the world's largest gold deposits are localised along a network of shear zones and faults that cut the Paleoproterozoic Birimian Supergroup of West Africa (Allibone et al., 2002b). Much of this mineral wealth is concentrated in Ghana, the second largest gold producer in Africa (Brown, 2015). The main gold belts in southwestern Ghana are the Ashanti Belt (total endowment ca. 170 Moz Au), the Sefwi–Bibiani Belt (N 30 Moz Au) and the Asankrangwa Belt (N 10 Moz Au) (Fig. 1; Table 1). Compared to the established gold belts, such as Ashanti and Sefwi– Bibiani, exploration activities within the Asankrangwa Belt (Fig. 2a) and enclosing Kumasi Basin have been limited and mainly focused around artisanal and past colonial operations. Possible explanations for the scarcity of detailed exploration are: (1) extensive recent alluvial and colluvial cover, and (2) relatively poor knowledge of the geology and structure of the Kumasi Basin. Moreover, (3) it was not until the mid-1990s that the gold potential of the Asankrangwa Belt (a shear zone along the central axis of the Kumasi Basin, Fig. 2a) was fully recognised. The discovery in 2006 by Asanko Gold Inc. of the outcropping Esaase gold deposit (Table 1) illustrates the potential of the Ore Geology Reviews xxx (2015) xxx–xxx ⁎ Corresponding author. OREGEO-01590; No of Pages 20 http://dx.doi.org/10.1016/j.oregeorev.2015.08.012 0169-1368/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Ore Geology Reviews journal homepage: www.elsevier.com/locate/oregeorev Please cite this article as: Chudasama, B., et al., Geology, geodynamics and orogenic gold prospectivity modelling of the Paleoproterozoic Kumasi Basin, Ghana, West Africa, Ore Geol. Rev. (2015), http://dx.doi.org/10.1016/j.oregeorev.2015.08.012