Riacho dos Machados (RDM)

Status Production
Metal Gold
Location Minas Gerais, Brazil
Mining Method Open Pit
Start-up March 2014
Reserves & Resources (March 31, 2017)
Proven and Probable Reserves* 883 koz at 1.00 g/t gold
Measured and Indicated Resources* 187 koz at 0.95 g/t gold
Inferred Resources 365 koz at 1.19 g/t gold
*Resources are exclusive of reserves.  See Mineral Reserves and Resources Table for more detail.
  2016A 2017A 2018E
Production (oz) 48,246* 43,116 75-85,000
Cash Costs ($ per oz) $881 $814 $790 - $820
AISC ($ per oz) $1,001 $989 $830 - $860
*Gold production including pre-acquisition production. Production attributable to Brio Gold only post-acquisition from April 29, 2016 was 31,714 oz.


The RDM Mine, which was acquired by Brio Gold on April 29, 2016, is located in Minas Gerais State, Brazil and has a land package of 22,600 ha. The operation is a conventional open pit mine with a 7,000 tpd Carbon in Leach plant. The RDM mine commenced production in early 2014. With the water storage facility, which is already complete, powerline installation and plant expansion, plant throughput is expected to increase to 9,000 tonnes per day in 2018. Average life of mine production at RDM is estimated to be approximately 98,000 ounces per year, over a nine year mine life.

Geology and Mineralization

The Riacho Dos Machados gold deposit occurs in the north-south trending Araçuaí Fold- Thrust Belt along the eastern margin of the São Francisco Craton, a major Archean-age basement block which underlies more than one million square kilometers in eastern Brazil. The Araçuaí Fold Belt is 15 km to 45 km wide and consists of a series of metavolcanicmetasedimentary rocks of late Archean to late Proterozoic age.

The mineralization has a typical amphibolite facies mineral association which is progressively altered to greenschist facies assemblage. The principal host for the gold mineralization is the quartz-muscovite schist of the Riacho dos Machados Group. The mineralization occurs in a belt of hydrothermally-altered rock developed along a district-scale shear zone. Mineralization occurs in the hydrothermal/shear zone and gold grades are closely related to the sulfide content, especially arsenopyrite. Gold occurs as microscopic native-gold grains at contacts between recrystallized quartz grains, muscovite grains and as inclusions in arsenopyrite, and less commonly in pyrrhotite, quartzveinlets, tourmaline, and pyrite.

RDM Mine Technical Report