Abstract

The Great Lakes region (Eastern DRC , Southwestern Uganda, Rwanda and Burundi) holds strategic importance due to its wealth of mineral resources critical to modern technology, such as tin (Sn), tantalum (Ta) and tungsten (W), collectively known as the 3Ts, and more recently lithium. The mineralisation is hosted in early Neoproterozoic pegmatites (cassiterite, columbite-tantalite) and quartz veins (cassiterite, wolframite), and their alluvial and eluvial weathering products. The pegmatites and quartz veins are linked to S-type granites that were emplaced in Paleo- and Mesoproterozoic metasedimentary and -volcanic rocks. Many of the pegmatites that were historically, or are currently mined for Sn and Ta, also host significant lithium in minerals such as spodumene, amblygonite-montebrasite or eucryptite, and have recently become important targets for lithium exploration.

In this seminar, I will present new insights into the formation and geological characteristics of lithium pegmatites in the region, focusing on examples from Musha-Ntunga (Rwanda) and Manono-Kitotolo (DRC) – the latter being one of the largest known spodumene pegmatite systems in the world. This giant deposit, with a lateral extent of at least 13.5 km and a thickness of around 300 meters, was historically mined for cassiterite and now holds an estimated resource of 842 million tonnes at 1.61 wt% Li₂O. Drill core samples reveal several high-grade zones exceeding 2% Li₂O, possibly corresponding to the core zones of individual pegmatite sheets.

Drawing on recent fieldwork and petrographic studies of drill cores that offer a full cross-section of the pegmatite system, I will explore potential emplacement mechanisms for this giant pegmatite system. Lastly, I will reflect on the geopolitical implications of mining and exploration in this region amidst growing global competition for critical resources.