Geology of the Goulamina spodumene pegmatite field, Mali

The Goulamina LCT spodumene pegmatite field, located south of Bamako in Mali, is one of the largest hard-rock lithium deposits in the world, with a resource of 103 Mt at 1.32% Li₂O for 1.4 Mt of contained Li₂O. Outcrops of spodumene pegmatite at Goulamina were recognised at least as early as the nineteen sixties, but the first recorded exploration activity was in 2007. This paper presents the first substantial description of the deposit and its mineralogy and geochemical composition. The deposit consists of a series of five sub-parallel spodumene pegmatite dykes (Main, West, West I, Sangar I & II) and an anastomosing dyke swarm (Danaya) all of which intrude the peraluminous Goulamina Granite. The dykes are dominated by spodumene pegmatite but contain lesser volumes of spodumene-bearing aplite and hydrothermal albitite but do not show systematic compositional zoning either at regional or local scale. Deformation, presumably during peak Eburnean compression at ca. 2.1 Ga, is evident in undulose extinction of constituent quartz and feldspar. The pegmatites were partially albitised after peak deformation. An unusual feature is the presence of primary magmatic loellingite, suggesting a possible genetic link with nearby hybrid gold deposits such as Morila.