Summary:
The Yanfolila Greenstone Belt, which is orientated north-south on the eastern margin of the greater Siguiri Basin hosts the Project. This belt forms part of the Birimian Volcano-Sedimentary series of the West African Craton. The belt contains several sub-basins including the KMSB and the KSB. These sub-basins, and the eastern margin of the wider Siguiri Basin, are bound to the east by the SSZ and the Siekerolé Granite. The SSZ is the major basin-bounding structure in the region. Mineralisation is typical lode gold-style deposits structurally reminiscent of a foreland fold and thrust belt with a deformational framework similar to the hanaian Gold Province.
The KMSB hosts the majority of the Yanfolila gold deposits and targets currently defined. It has a stratigraphic sequence of basalt, polymict conglomerate, feldspathic sandstone, silt-shale, and a lithic-dominated greywacke. Mafic and felsic (porphyry, granodiorite, and diorite) intrusives crosscut the stratigraphy. Splays of the SSZ and regional-scale structures, which crosscut strata, control gold mineralisation. Gold is associated with rheological contrasting rock types that have been structurally deformed to provide fluid pathways from where any combination of disseminated, vein, breccia, intrusive, and replacement styles may evolve.
Outcrop is sparse throughout the basin and is mostly extensive lateritic and depositional terrains.
Lithologies at KW comprise interbedded siltstone and sandstone, with basalts and porphyry intrusives. Regional scale cross-cutting faults and structural lineaments, as well as rheologically contrasting rock types, appear to control the localisation of gold. Mineralisation appears to be related to basalt at the western margin along the main north-south shear zone as well as in the contact zone with metasediment. Feldspar porphyry has locally developed quartz-vein stockwork associated with pyrite and arsenopyrite. Main alteration minerals are sericite, silica, feldspar, chlorite, and epidote. Weathering and oxidation of the sulphide component generally extends to a depth of 50 to 90 m, with a well-developed regolith zone.
The host rocks at KE comprise a mafic dolerite intrusion in the south and a iltstone unit in the north. Mineralisation is quartz-albite-carbonate breccia veins and related pyrite-hematite altered February 2015 4 wall rocks associated with brittle-ductile shear zones. The orebody geometry strikes northsouth to north-northeast and dips steeply to the west and is transected by numerous northeast striking faults, some of which are mineralised. Weathering and oxidation of the sulphide component generally extends to a depth of 30 to 50 m, with a well-developed regolith zone.
At Sanioumale East (SE), the main lithologies include a sequence of basalt and metasediment (interbedded siltstone, sandstone, and polymict conglomerate). Mafic dyke (dolerite) as well as felsic porphyry dykes occur in the system. Mineralisation is hosted mainly in basalt and the dolerite dyke proximal to the contact with metasediment. The mineralisation style comprises quartz-albite carbonate breccia veins and related pyrite-hematite altered wall rocks associated with brittle-ductile shear zones. The orebody geometry is strikes north-south to north-northeast and dips steeply to the west, and is transected by numerous northeast striking faults, some of which are mineralised. Weathering generally extends to a depth of 30 to 50 m, with a welldeveloped regolith zone.
Sanioumale West (SW) lithologies include metasediments made up of sandstone and siltstone, as well as volcanoclastics with coarse grained feldspar and clasts. Mineralisation occurs in a deformed stratigraphic sequence of sandstone and siltstone including the volcanoclastics. Regional scale cross-cutting faults and structural lineaments, as well as rheologically contrasting rock types, appear to control the localisation of gold. Mineralisation styles are dominated by quartz feldspar-carbonate veins in shear zones with disseminated pyrite grains in the numerous fissures. Weathering generally extends to a depth of 30 to 60 m, with a welldeveloped regolith zone.
Guirin West (GW) lithologies comprise metasediments of inter-bedded siltstone and sandstone, with basalt; mafic, and felsic intrusives. Mineralisation appears to be related to a felsic intrusive and volcanoclastics hosting a stockwork of quartz feldspar-carbonate veins (10 to 50 cm in width). Weathering generally extends to a depth of 50 to 70 m, with a well-developed regolith zone.