The majority of gold deposits on the West African Craton are orogenic-style deposits (Robertson and Peters, 2016). Orogenic-style deposits are sited proximal to major accretionary structures within, or at the boundaries of, composite metamorphosed volcanic- plutonic or sedimentary terrains. The majority of orogenic gold deposits occur within rocks that have been metamorphosed to greenschist facies, within a metamorphic pressure-temperature regime broadly corresponding to the brittle-ductile transition (McCuaig and Kerrich, 1998; Moritz, 2000).

The Markoye Fault is interpreted to be the main conduit for the gold mineralisation found at Sanbrado, accommodating large scale fluid migration. Sanbrado hosts shear zone type quartz vein gold mineralisation, similar to that found elsewhere in late Proterozoic Birimian terrains of West Africa. These orogenic type deposits exhibit strong relationships with regional arrays of major shear zones.

The structural environment can be described as brittle-ductile, coincident with a greenschist-amphibolite metamorphic facies. Arrays of transtensional features are apparent within a preferred S2 shear corridor and a strong shear controlled folding component is evident. Gold mineralisation is hosted in the sheared diorite and in the deformed mylonitic metasediment, and there is also a spatial relationship with the contact zones. It appears that the competency contrast caused by more brittle bodies of diorite within zones of mo ........

Open pit mining
Mining occurred at the M1 South, M1 North, M5 South and M5 North open pits during 2021. Open-pit mining in 2022 reconciled in-line with WAF’s 10-year production plan. With the completion of the high-grade M1 South open pit in Q1 2022, ounces mined from open pit mining decreased 44% . 2022 saw WAF cut back the M5 South open pit to the final design, resulting in a 24% decrease in ore tonnes mined and a 21% higher average strip ratio in the year. The M5 South cut back, which was completed in Q4 2022, opens access to higher grade ore in the pit and reduces the strip ratio for the remainder of the open pit mine life to an approximate average of 3 : 1 (waste: ore).

The Sanbrado open-pits employ conventional open-pit mining techniques using drill and blast with material movement by hydraulic excavator and trucks. The project scale and selectivity suit the operating mining fleet of 150 t class excavators in a backhoe configuration matched to 90 t class mine haul trucks. The Sanbrado operation is a multi-pit operation with ore being mined from the M5, M1 South, M1 North and M3 pits. All pits are within 2 km of the primary crusher location.

To suit this sized equipment a bench height of 5 m has been adopted. The benches will be excavated on 2 x 2.5 m high flitches, for blasted material this will be 2 x 3 m high flitches when swell is accounted for.

Underground mining
For most of 2020, M1 South underground ore was sourced from d ........

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