Paracatu mine (Morro do Ouro mine), Paracatu, Minas Gerais, Brazili

Regional Level Types
Paracatu mine (Morro do Ouro mine)	Mine
Paracatu	Municipality
Minas Gerais	State
Brazil	Country

The name of this mine means "Hill of Gold." Actually, gold was first discovered in stream deposits (1722). Placer mining, practiced primarily by garimpieros, peaked in the mid-1800's, and continued until the 1980's. The open-pit Morro do Ouro gold mine was begun by Rio Tinto in 1987. It produced about 50 tonnes of gold through 1999, and accounted for about 9% of Brazil's total gold production from 1982 to 1999. In 1997 the Morro do Ouro deposit had reserves estimated at 42 million tonnes of ore with 0.65 g/t of Au. In 2006, measured plus indicated reserves were 67.5 million tonnes at 0.33 g/t Au, and production for that year was 17.637 million tonnes of ore containing 0.38-0.59 ppm Ag. This very low-grade deposit has been economic to produce because of its flat-lying attitude and deep oxidation of the soil, so that no crushing, milling, or blasting was required to obtain and move the ore. In 2000, operations were conducted by Rio Paracatu Mineraçao S. A., a Brazilian subsidiary of Rio Tinto (51%) and TVX Normandy. Kinross Gold Corporation purchased the assets and assumed operations in December of 2004. More recently the operation has been converted to a tourist mine.

The gold occurs as inclusions of 1 to 800 microns (although 60% of the grains are larger than 50 microns) in pyrite and arsenopyrite in a disrupted stockwork of quartz-sulfide veins and disseminated in weakly metamorphosed graphitic phyllites and argillaceous quartzites of the Paracatu Formation. Paracatu strata were deposited at 1000-850 Ma, and were folded and thrust-faulted over carbonate strata of the Vazante Formation during the Brasiliano Orogeny at 680-650 Ma. During the orogeny quartz veins were broken up into sigmoidal boudins up to 15 cm in length. Mineralization occurred somewhat before the orogeny, when metals moved in solution in hydrothermal fluids possibly related to a deep-seated magmatic center that had become separated from the host strata during the thrusting.

Rev. by NK, September 2016

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