A Review of Gold Mineralization in Mali

Abstract

Economic gold mineralization in Mali is confined to two terranes of Birimian-aged (Paleoproterozoic) rocks in the south and south-west of the country. The West Mali gold belt, along the border with Senegal, hosts two world-class orogenic gold districts (>5 Moz of Au mined or in reserve): the Loulo-Gounkoto and Sadiola-Yatela complexes. This gold province is hosted within greenschist metamorphosed siliciclastic and carbonate sedimentary rocks along the eastern side of the Kédougou-Ké-niéba inlier, with mineralization linked to higher-order shears and folds related to the Senegal-Mali Shear Zone. Gold deposits within the West Mali gold belt show many features typical of orogenic gold mineralization, such as geological setting (accretionary orogen), late-orogenic timing (strike-slip deformation; post peak metamorphism), structural paragenesis, and deposit geometry (steep, tabular ore bodies). However, alteration assemblages (tourmalinization, silica-carbonate, sericite-chlorite-biotite, calc-silicate) and ore fluid compositions (carbonic-rich and high-salinity aqueous-rich fluids) are highly variable along the belt. Fluid inclusion and stable isotope studies have shown that this variability is caused by multi-fluid sources, with magmatic, evaporitic and regional metamorphic fluids all likely contributing to gold mineralization within the region. Supergene enrichment of the orogenic gold lodes is economically important in the northern parts of the West Mali gold belt, involving karstification of mineralized limestones. In addition to orogenic gold deposits, other styles of gold mineralization have been reported within the Birimian crust of West Africa. The Morila gold deposit, in southern Mali,

The Tongon Au Deposit, Northern Côte d’Ivoire: An Example of Paleoproterozoic Au Skarn Mineralization☼

“…Africa (Oberthür et al, 1996(Oberthür et al, , 1998Lawrence et al, 2013aLawrence et al, , 2016Treloar et al, 2014;Lambert-Smith et al, 2016;Markwitz et al, 2016).…”

“…The data reported in this paper also highlight the diversity of Au deposits in the Paleoproterozoic rocks of West Africa, many of which have only been recognized in the last ca. 10 years (e.g., McFarlane et al, 2011;Lawrence et al, 2013aLawrence et al, , 2016Treloar et al, 2014;Hein et al, 2015;Béziat et al, 2016;Masurel et al, 2016;Le Mignot et al, 2017).…”

Orogenic gold: is a genetic association with magmatism realistic?

“…Where abundant base metals are present, they are typically local concentrations within a much broader gold resource and are rarely economically recoverable. Examples include the Gara deposit in the Loulo mining district, Mali, where locally high base metal contents and high-salinity fluid inclusions have been interpreted as an indication of either a magmatic fluid source or a fluid produced from metamorphism of an evaporative unit (Lawrence et al 2016;Lambert-Smith et al 2020). The typical lowsalinity fluids have been modeled to show that only 2-5% of the total Cu, Pb, and Zn within a typical metapelite will be mobilized during metamorphic events that release significant Au and As volumes during chlorite dehydration and pyrite desulfidation of the same rocks (Zhong et al 2015).…”

Etude Metallogenique du Prospect Aurifere de Aoulo-Aoulo (Zone D’afema, sud est de la Cote d’Ivore)

“…; Wille etKlemd, 2004) ; au Mali : Boutonnière de Kedougou-Kenieba(Lawrence et al 2016, Masurel et al, 2016, dans la ceinture d'Ashanti au Ghana(Oberthür et al, 1996(Oberthür et al, et 1997 ; au Sénégal : dans les shear-zones aurifères, de Sabodala (Sylla et N'Gom, 1997) ; au Burkina Faso : Taparko (Bourges et al, 1998) et de Diabatou (Milési et al, 1989 et 1992 ; Klemd et al, 1997). Cela montre une corrélation parfaite entre la minéralisation de Woulo-Woulo et les autres minéralisations du Birimien.…”