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.

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 development headings with first underground stoping ore mined from panel-1 in late September 2020. Mining from panel-2 commenced in late Q2 2021, which enabled more continuous stope production from two ore panels for the remainder of 2021. Some 3.2 km of development was completed in 2021. At the end of 2021 the decline was 385 metres vertically below surface.

The M1 South underground mine is a decline access mine using diesel powered loaders and trucks; and electric powered drilling equipment. A long hole open stoping method with cemented rock fill is used to min ........

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