Primary gold deposits in Burkina Faso occur within the Paleoproterozoic Birimian belt. Mineralization was synchronous with regional metamorphism and deformation. Gold deposits found within the Birimian greenstone belts of the West African shield are typically late orogenic hydrothermal deposits that exhibit a strong relationship with regional arrays of major shear zones. The gold mineralization is typically associated with an organized network of quartz veins containing subordinate amounts of carbonate, tourmaline, sulphides, and native gold. In these deposits, the gold is typically free milling. Alternatively, gold mineralization can also be associated with disseminated sulphides in strongly deformed alteration zones. In the alteration zones, gold may be free milling, but also refractory.

Gold mineralization is related to regional arrays of alteration and deformation zones, commonly located at major lithological discontinuities. The local controls on the distribution of the gold mineralization are structural and lithological.

In Burkina Faso, the weathering profile is deep and typically results in extensive surface oxidation of bedrock to a depth reaching more than 100 metres locally. In such areas, gold deposits typically comprise a surface oxide zone, an intermediate transition zone, and a deeper fresh rock zone. Gold is typically free milling in the oxide zone.

The gold mineralization found at the 55 Zone and Bagassi South Zone deposits is associated with low sulphide quartz veins and is free milling. The weathering profile over the deposit is shallow and ranges from approximately 10 to 30 metres.

Property Geology
The north-northeast trending Boni shear zone divides the Yaramoko Gold Project between predominantly Houndé volcanic and volcaniclastic rocks to the west and the minor volcanic rocks of the Diébougou granitoid domain to the east.

The eastern assemblage contains several intrusive bodies, including a diorite body east of the village of Yaramoko, a large quartz bearing granitoid which stretches south from the town of Bagassi, and a smaller granitoid body to the east of Bagassi. The granitoid body east of Bagassi hosts the 55 Zone gold deposit. A diabase (dolerite) dike trends north-northeast across the southern portion of the property.

Outcrop and core observations document the main lithological units present on the Yaramoko Gold Project as mafic volcanic rocks, felsic dikes, and late dolerite dikes. The mafic volcanic rocks constitute the main country rock, and are locally strongly magnetic and in places affected by calc- silicate skarn alteration (garnet, calcite, epidote, and magnetite). The mafic rocks are crosscut by multiple generations of felsic dikes with aplitic, pegmatitic, or porphyritic textures. Late dolerite dikes crosscut mafic volcanic rocks, felsic dikes and gold mineralization (SRK, 2013b).

Mineralization
Gold is the main mineralization of economic interest found on the Yaramoko Gold Project. The main areas of gold mineralization are the 55 Zone, Bagassi South Zone, 109 Zone, and 117 Zone. The 55 Zone and Bagassi South Zone are the two main zones, both of which are hosted in the Diebougou granitoid domain.

Both the 55 Zone and Bagassi South Zone deposits occur along dextral shear zones and gold is primarily associated with quartz veining. The bulk of the gold mineralization occurs in dilational segments of the shear zone where quartz veins are thicker and exhibit greater continuity. Gold typically occurs as coarse free grains in quartz and is associated with pyrite. The gold bearing veins range in size from a few centimetres to over 5 metres in width, and contain only minor concentrations of disseminated pyrite (frequently less than one percent). Adjacent sheared vein wall rock locally contains a small percentage of pyrite.

At the Bagassi South Zone, the gold mineralization is associated with laminated quartz-carbonate veins developed in two shear zones: QV1 and QV'. The average thickness of the gold mineralization at QV1 varies from less than one metre to over 18 metres and extends from the surface to over 300 metres depth; gold mineralization remains open along strike and at depth. Gold mineralization at
the Bagassi South Zone is associated with quartz and pyrite alteration in similar structural settings as at the 55 Zone.

Four mineralogically distinct hydrothermal veins were defined from samples from the 55 Zone: quartz rich veins, iron-dolomite rich veins with quartz and muscovite, iron-dolomite and quartz veins with albite, and albite rich veins with quartz and iron-dolomite (GeoMinEx, 2013). Native gold is present in each vein type, with accompanying sulphides of pyrite and trace tellurides. The most abundant sulphide mineral, pyrite, occurs in veins and altered wall rock. Textural and chemical complexity of pyrite document a protracted period of crystallization from a compositionally evolving hydrothermal fluid. Native gold occurs in numerous textural associations and at a wide range of grain size ranging from less than 1 and up to 300 micrometres.

The second type of gold mineralization encountered is also associated with pyrite, occurring in zones of conspicuous shearing primarily in the volcanic rocks, with minimal to no significant quartz veining. These two styles of mineralization represent two end-members of brittle-ductile deformation within the 55 Zone where coarse gold in veining, usually seen in a granitic host, defines a more brittle environment while pyrite and shearing in the volcanic rocks is typical of a ductile domain.

Mining operations at Yaramoko are comprised of the 55 Zone underground mine, which was commissioned in 2016, and Bagassi South underground mine, which was commissioned in 2019. The underground operations utilize longhole stoping with cemented rock fill as its primary mining method. Mine development and stoping operations are conducted for Roxgold by African Underground Mining Services under a mining services agreement.

The processing plant uses the conventional gravity/CIL gold recovery processes. The comminution circuit of the process plant is comprised of a primary jaw crusher and secondary cone crusher – both in open circuit – followed by a SAG (Semi Autogenous Grinding) mill.

The processing plant was expanded in 2018 increasing the design capacity from 270,000 tonnes per annum to 400,000 tonnes per annum. The expansion was designed by DRA (Pty.) Ltd in Johannesburg, South Africa.

The processing plant uses the conventional gravity/CIL gold recovery processes. The comminution circuit of the process plant is comprised of a primary jaw crusher and secondary cone crusher – both in open circuit – followed by a SAG (Semi Autogenous Grinding) mill.

This is followed by a gravity circuit fed from the cyclone underflow stream, consisting of two centrifugal concentrators and an intensive leach reactor for treatment of the gravity concentrate, treating 70 percent of the cyclone underflow. The process also includes a carbon-in-leach (CIL) circuit consisting of one leach tank and five adsorption tanks, treating the cyclone overflow.

The metal recovery and refining circuit consists of an elution circuit, electrowinning cells, and smelting furnace.