The high-grade Yaramoko underground gold project, located in Burkina Faso, West Africa, is wholly owned by Roxgold Inc., a Canadian-based gold exploration and development company.
In 2013, Roxgold commissioned SRK to lead a team of multidisciplinary consultants from SRK and other independent consulting firms in preparing a bankable feasibility study for a proposed underground mine and on-site concentrator.
Three SRK offices shared the scope of work:
- SRK Toronto was responsible for project management, geological modelling, mineral resource estimation, underground mine planning, financial modelling and compiling the 43-101 technical report.
- SRK Vancouver undertook the rock geotechnical design of the underground mine.
- SRK Cardiff’s scope included hydrogeology and water management, social and environmental management, geochemistry, and mine closure.
This article focuses on the geological modelling, mineral resource evaluation and mine planning aspects of the feasibility study.
At Yaramoko, the mining target is the gold-bearing 55 Zone, a narrow shear zone, which varies in width from a few centimetres to more than four metres. Based on detailed on-site structural geology investigations, the reverse shear zone, which defines a low-grade resource domain, was modelled geologically. Within the shear zone, most of the high-grade gold mineralisation is associated with low-sulphide quartz veins developed within dilational zones. High-grade gold resource domains were modelled with a shallow west plunge, consistent with the structural geology interpretation.
Using a geostatistical block modelling approach, SRK estimated the mineral resources for the 55 Zone. This approach was constrained by geologically-defined low- and high-grade gold mineralisation wireframes and informed by capped and composited core borehole data.
The underground mine plan is based on longhole open stoping on 17m sublevels, using cemented rock backfill (CRF). A dual ramp system will provide access to the underground mine from a single portal. Ore and waste rock will be hauled to the surface by 25-tonne capacity trucks. Probable ore reserves of 2.0 Mt at 11.8 gpt Au will be mined at 750 tpd over a 7.3 year mine life.
Key features of the mine include:
- High-grade gold veins with regular geometry and excellent grade continuity;
- Fast development access planned from the portal to the upper vein area that hosts some of the highest gold grades;
- Full up-hole retreat recovery of planned sill pillars to be located below highstrength CRF; and
- Contractor-operated mine startup with mid-life transition to owner mining.
SRK’s feasibility study report, dated June 4, 2014, is entitled “Technical Report for the Yaramoko Gold Project, Burkina Faso.”
Roxgold expects to begin production in Q2 2016.
