Structural Control of Auriferous Mineralization in the Birimian: Case of the Agbahou Deposit in the Region of Divo, Côte d’Ivoire

Abstract

Located in the southwestern of the Oume-Fettekro greenstone belt, the Agbahou gold deposit is controlled by structural factors. Geophysics, teledetection and core data suggest the presence of NE and NW faults. However, the NEfaults define two major shear zones (ATZ: Agbahou Tectonic Zone and WTZ: West Tectonic Zone) that control the Agbahou gold mineralization. These first order structures are subparallel to the regional tectonic grain mostly north-east oriented. They seem to respectively develop on the both arms (eastern and western) of an anticline moderately plunging ~25˚ towards northeast. Each shear-zone contains several second-order shear-zones or lenses of variable direction and of 50˚ -80˚ dip. NW-faults however correspond to strike-slip faults and their development should be related to transcurrent tectonics. They acted as control channels on the distribution of gold mineralizations. The ductile-brittle character of shear-zones favored the ascent of hydrothermal fluids and the formation of multiple auriferous quartz veins: veins Type IIa and veins Type IIb relating respectively to the shear-veins and extensional veins. However, Agbahou also shows the existence of a disseminated sulphides-bearing mineralization within host-rocks. At Agbahou, the precipitation of gold probably occurred in a post to late ductile-brittle deformation period.

Mise En Évidence De Nouvelles Structures Géologiques Dans La Région De Brobo (Centre De La Côte d’Ivoire). Aide À La Compréhension De La Tectonique Du Paléoprotérozoïque Du Craton Ouest Africain

“…Les contextes des minéralisations aurifères décrites dans le sillon d' Oumé (dans la partie Sud) indiquent un contrôle lithologique et structural (Houssou, 2013 ;Ouattara, 2015 ;Houssou et al, 2017). Nombreuses nouvelles zones de failles sont décrites dans la région de Brobo.…”

“…Ces formations sont intrudées par des plutons de granites calco-alcalins et alcalins. Il est également à noter que les formations paléoprotérozoïques (birimiennes) de l'Afrique de l'Ouest sont bien connues pour accueillir de nombreuses minéralisations aurifères économiques (Milési et al, 1989(Milési et al, , 1992 ; Kusnir, 1999 ;BRGM, 2005 ;Assié, 2008 ;Béziat et al, 2008 ;Billa & Bonnemaison, 2009 ;Dabo, 2011 ;Houssou, 2013 ;Gnanzou, 2014 ;Ouattara, 2015 ;Ouattara et al, 2016 ;Houssou et al, 2017 ;Traoré, 2017).…”

Mineralization and sustainable development in the West African Craton: from field observations to modelling

“…Gold is found mostly in greenstone belts, especially in the interfaces of the Birimian volcanic and volcanoclastics (Burkina Faso, Côte d'Ivoire, Ghana, Mali, Senegal, etc. )(e.g., Davis et al, 1994;Béziat, et al, 2008;Ballo et al, 2016;Dabo et al, 2016;Augustin and Gaboury, 2017;), but also in the contacts between both these formations, affected by shear zones (Milési et al, 1989;Houssou, 2013;Ouattara, 2015;Ouattara et al, 2015;Houssou et al, 2017;Ouattara et al, 2018a). The paper of Ouattara et al (2020) concerns gold mineralization in the Oumé-Fettèkro greenstone belt, one of the largest Precambrian belts (300 km long and 40-5 km wide) of Côte d'Ivoire.…”

“…The paper of Ouattara et al (2020) concerns gold mineralization in the Oumé-Fettèkro greenstone belt, one of the largest Precambrian belts (300 km long and 40-5 km wide) of Côte d'Ivoire. This greenstone belt, composed of NNE-SSW schist and quartzite, sandstone and conglomerates, is affected by different injections of meta-basites and acidites (Yacé, 1982;Lemoine, 1988;Mortimer, 1990;Daouda, 1998;Houssou, 2013, Ouattara, 2015Ouattara et al, 2015;Houssou et al, 2017). The authors concentrated on the Bonikro deposit to try establish a relationship with the shear zones.…”

“…The Fettèkro is one of the numerous greenstone belts NE to ENE trending along with their shear zones, considered as the most productive gold belt in Côte d'Ivoire. In its southern part, namely the Oumé-Fettèkro greenstone belt, extensive exploration resulted in the discovery of four gold deposits: Bonikro (15.9 kt at 1.8 g/t) (Ouattara, 2015;Ouattara et al, 2018a, b), Agbahou (Houssou, 2013;Houssou et al, 2017), Dougbafla-Bandama (Ouattara et al, 2017) and Hiré (Gnanzou, 2006). The first Bonikro pit, located in the southern part of the deposit where the shear zone can be seen (Ouattara et al, 2018a), the higher-grade ores were found around NNE quartz veins.…”