Casposo – Argentina
The Casposo mine is a low-sulphidation epithermal deposit of gold and silver located 10km NW of the township of Calingasta, in the Calingasta department, San Juan Province. The Casposo mine consists of an underground mining operation and processing plant. The mine is approximately 150km from San Juan, the capital of San Juan province and covers an area of 100.21km²
The Cordillera Principal runs along the Chile-Argentine border for some 1,500 km. It is a volcanically and seismically active zone formed by subduction of the Nazca plate beneath the South American continent. The main basement is formed by Permian–Triassic intrusive and volcanic rocks, of calc-alkaline affinity and andesitic to rhyolite composition, regionally known as the Choiyoi Group. These and younger sediments of Jurassic and Cretaceous age have been thickened by compression and thrusting principally since the Late Cretaceous in a thin-skinned fold-thrust belt.
The Mine is located on the eastern border of the Cordillera Frontal. Basal andesitic volcanic flows, tuffs and breccias are the main sub-surface unit in the Casposo Property and are overlain by rhyolite, rhyolite-dacite flows and dacitic ignimbrite flows.
Ownership: 100% Austral Gold
Status: Currently on care and maintenance
Historical Production: 2010-2019
Gold: 329,374 oz
Silver: 13,662,197 oz
Gold equivalent: 529,861 oz
Capacity: 1500 tpd crushing circuit to agitation leach and Merril-Crowe processing plant.
The Casposo gold–silver mineralization occurs in both the rhyolite and underlying andesite, where it is associated with banded quartz–chalcedony veins, typical of low sulphidation epithermal environments.
Mineralization at Casposo occurs along a 10 km long W–NW to E-SE-trending regional structural corridor, with the main Kamila Vein system forming a sigmoidal set 500m-long near the center. The Mercado Vein system is the northwest continuation of Kamila and is separated by an east-west fault from the Kamila Deposit. The Casposo Norte deposit is located on a parallel structure approximately two kilometers north of Kamila.
The Casposo Mine consists of a number of narrow steeply dipping orebodies known as Aztec, B-Vein, B-Vein1, Inca0, Inca1, Inca2A, Inca2B, Mercado, and Julieta. The main production from the underground mine to date has been from Inca1, Aztec, and Inca2A.
The mining method used at the Casposo Mine is Longitudinal Longhole Retreat.
Processing capacity is 1500 tpd through a crushing circuit to agitation leach and Merril-Crowe processing plant.