Mining Rate: 1500 tpd
- Guanaco Underground: 1000-1100 tpd
- Amancaya 400-500 tpd
Processing: 1500 tpd crushing circuit to agitation leach and Merril-Crowe processing plant.
Annual Production (2013-16): 45-51,000 oz p.a.
Average Cash Cost (2013-16): $683/ oz Au Eq.
Average All-in Sustaining Cost (2013-16): $753/oz Au Eq
Gold mineralisation at Guanaco is controlled by pervasively silicified, E/NE trending sub-vertical zones with related hydrothermal breccias. Silicification grades outward into advanced argillic alteration and further into zones with propylitic alteration. The deposit is classified as a high sulphidation epithermal system. The weathering profile is very deep, with all ore production being oxidised material.
Mineralisation is structurally controlled with some lithological controls over higher grade mineralisation seen at the Cachanalito vein system.
The Amancaya project represents a low sulphidation gold-silver epithermal deposit hosted in the Depresión Central; a Paleocene-Eocene volcanic belt that host numerous epithermal deposits in northern Chile. Mining operations are currently focussed on the Central vein, a N-S striking vein. The Central Vein exhibits banded textures, with bands of grey chalcedony, clear crystalline quartz, amethyst, and dark bands containing sphalerite, silver, and lead sulphosalts. Other textures include colloform, sinuous alternating bands of chalcedony and amethyst, and crustiform quartz. Interstices are filled with clays, limonites, manganese oxides, and carbonates (ankerite mainly). Supergene enrichment of silver in the oxide zone is exhibited.
Dozens of mineralised veins have been exploited in the district, the most important veins being the Defensa, Perseverancia, Abundancia, and San Lorenzo.
Current operations are all underground with typical mining width of 2-6 metres. Production stopes within ore shoots utilise open sub-level stoping methodology.
The project has had no historical mining, despite outcropping at surface. The open-pit mine at Amancaya is carried out as a conventional operation using 30t trucks and a combination of excavators and front-end loaders. Waste and ore is blasted and mined separately using a “trenching” method to reduce the amount of dilution.
Ore from Guanaco and Amancaya is treated at the Company’s new plant at Guanaco (Figure 1). Ore trucked from Amancaya is batched through the plant due to its higher silver content.
Ore is passed through a three stage crushing process, prior to entering the 1500 tpd agitation leach plant. Pregnant solution is passed into a Merrill-Crowe circuit where gold and silver are extracted and a gold and silver doré is produced.