Loulo is a world-class orogenic gold mining district in the Birimian terrane of western Mali. Orebodies are located along second or higher order shears associated with the Senegal-Mali shear zone, with gold mineralization largely linked to a transtensional event. The mine camp is divided into two distinct styles of gold deposit on the basis of differing geologic characteristics. One group is typified by the Gara deposit, whereas the other by the Yalea deposit. Both deposit styles are hosted by similar rock types (calcareous graywackes and calciticdolomitic marbles). Gara-style orebodies occur as sulfide disseminations or ankerite-rich shear vein stockworks, hosted in folded tourmalinized sandstones and breccias mainly within 2 km of the Senegal-Mali shear zone. These deposits are characterized by intense multi-stage albitization and tourmalinization (pre-, syn- and postmineralization).

Gold lodes are Fe-rich (dominated by nickeloan pyrite), contain Cu-Ni ± Co minor and trace sulfides (e.g., chalcopyrite, gersdorffite, pentlandite, cobaltite, millerite), and show consistently high levels of P-REE-W bearing phases (apatite, monazite, xenotime, and scheelite). Base metal concentrations show a marked increase in marble host rocks, with the formation of nickeloan pyrite-cobaltite clausthalite ores.

In contrast, Yalea-style deposits are associated with quartz ± ankerite vein lodes and disseminated sulfide stringer zones. Mineralization occurs along highly altered (tourmaline-absent), brittle-ductile, shears up to 8 km away from the Senegal-Mali shear zone. Wall-rock alteration is characterized by addition of K2O, CaO, CO2, H2O, and SiO2, with mineral assemblages consisting of chlorite-sericite carbonate-quartz ± albite. Ore paragenesis is enriched in As, mainly as multistage growth of arsenopyrite and arsenian pyrite. Base metal sulfides, scheelite, and (REE)-phosphates are extremely rare.

A combination of transverse and longitudinal longhole stoping mining method is used at Yalea, and longitudinal longhole stoping at Gara.

Overall gold recovery of 90.1% was in line with the prior year, while plant utilisation of 92.3% increased from 91.7% in 2014. Gold recovery of plus 91.0% is being targeted for 2016 on the back of the upgrades to the gravity, elution and regeneration circuits, along with other improvement initiatives, including an upgrade to the Aachen reactors to increase oxygen availability in the CIL.