The deposits and other prospects within the Casposo property are examples of low-sulphidation epithermal deposition of gold and silver.

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. Adularia in the main veins gives an age date of 280 ± 0.8 Ma (K/Ar), very close to the published age dates for the andesite unit. Post-mineralization dykes, of rhyolitic (Kamila), aphanitic-felsic and trachytic (Mercado) composition often cut the vein systems. These dykes, sometimes reaching up to 30 m thickness, are usually steeply dipping and north–south oriented.

Mineralization at Casposo occurs along a 10 km long west–northwest to east–southeast trending regional structural corridor, with the main Kamila Vein system forming a sigmoidal set 500 m long near the centre. The Mercado Vein system is the northwest continuation of Kamila, and is separated by an east–west fault from the Kamila deposit. A series of east–west striking veins (Cerro Norte and Oveja Negra systems) appear to splay off these major sets to the east and northeast. The Casposo mineralized district identified to date covers an area of approximately 100 km2.

KAMILA DEPOSIT
The gold–silver mineralization at the Kamila deposit is structurally controlled and occurs in crustiform-colloform quartz veins and stockworks in both andesite and ........

The Casposo Mine consists of a number of narrow steeply dipping orebodies known as Aztec, B-Vein, B-Vein 1, Inca 0, Inca 1, Inca 2A, Inca 2B, Mercado, and Julieta. Open pit mining in Kamila and Mercado pits was completed in 2013, and all mining is currently planned as underground, although there is potential for open pit mining at Julieta. The main production from the underground mine to date has been from Inca 1, Aztec, and Inca 2A.

The mining method used at Casposo is longitudinal longhole retreat. Mine production is made up of a combination of ore development through sill drifts (34%) and stope production (66%).

The veins are accessed by sub-level footwall drives, driven from the main ramp at 15 m intervals. Stopes were designed using a minimum mining width of 2 m and are 10.5 m high, while sill drifts were designed at 4.5 m high and on average 4.0 m to 5.0 m wide. Stope lengths vary depending on the orebody but are limited to a maximum of 15 m due to geotechnical constraints.

Mining progresses in a bottom up fashion. Stopes on each level are accessed in the middle and developed along strike, at both the top and bottom elevations. Once sill development is completed, the stopes are drilled and blasted. Drilling and blasting start at the end of the stoping blocks and mucked in retreating vertical slices.

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