The Wassa deposit: A poly-deformed orogenic gold system in southwest Ghana – Implications for regional exploration. (December 2015)

• Record Type: Journal Article
• Authors: Perrouty, Stéphane; Jessell, Mark W.; Bourassa, Yan; Miller, John; Apau, Daniel; Siebenaller, Luc; Velásquez, Germán; Baratoux, Lenka; Aillères, Laurent; Béziat, Didier; Salvi, Stefano
• Is Part Of: Journal of African earth sciences. Volume 112:Part B(2015:Dec.)
• Page Start: 536
• Page End: 547
• Publication Date: 2015-12
• Subjects: Wassa -- Birimian -- Tarkwaian -- Eburnean -- Eoeburnean -- Ashanti Belt; Earth sciences -- Africa -- Periodicals; Earth sciences -- Middle East -- Periodicals; Geology -- Africa -- Periodicals; Geology -- Middle East -- Periodicals; Sciences de la terre -- Afrique -- Périodiques; Sciences de la terre -- Moyen-Orient -- Périodiques; Géologie -- Afrique -- Périodiques; Géologie -- Moyen-Orient -- Périodiques; Earth sciences; Geology; Africa; Middle East; Periodicals; Electronic journals; 556.05
• DOI: 10.1016/j.jafrearsci.2015.03.003
• Languages: English
• ISSNs: 1464-343X

Abstract

Abstract: The Ashanti greenstone belt in southwest Ghana hosts many gold deposits distinguished by different timing and structural contexts. This study investigates the evolution of the Wassa system by integrating field and geophysical observations. This 4 million ounces (past production and current resources) gold deposit is interpreted to represent the oldest gold mineralization event in West Africa with gold-bearing pyrites aligned and stretched within the S1 ductile fabric. Mineralized quartz-carbonate veins were strongly deformed during the D1 deformation event. Three additional folding events are characterized by hectometer-scale tight to isoclinal folds, by a kilometer-scale synform fold centered on the mine and by a late recumbent metric-scale folds. Because of its early timing, the Wassa system represents a new poly-deformed deposit type in West Africa and highlights a potential for new discoveries in the underexplored meta-volcanic and meta-sedimentary Sefwi Group. Timing of the gold mineralization at the Wassa mine makes this deposit type a possible candidate for the source of the gold contained in the Tarkwa paleoplacer. Highlights: The Wassa mine is the first example of an early-orogenic gold system in West Africa. Gold-bearing pyrite are aligned and stretched along the S1 ductile fabric. Mineralized quartz-calcite-ankerite veins have been folded at least four times. Wassa-type deposits are possible sources of gold for the Tarkwa paleoplacer.