Diablillos is a high-sulphidation epithermal silver-gold deposit located in the southern part of Salta Province, Argentina.
AbraSilver Resource, an advanced-stage exploration company, is the 100%-owner of the project.
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The company announced results of Preliminary Feasibility Study (PFS) for Diablillos project in March 2024. In December 2024, an updated PFS superseded the previous report.
The PFS predicted that the mine would produce 13.4 Moz silver-equivalent (AgEq) on average over a 14-year life-of-mine (LOM), comprised of 7.6 Moz silver (Ag) and 72 koz gold (Au).
Initial pre-production capital expenditure is estimated to be $544m, including contingency. The project will require an additional $77m in sustaining capital over the LOM.
AbraSilver plans to finalise the Definitive Feasibility Study (DFS) for the silver-gold project in first half of 2026. The DFS will build upon the PFS conclusions, and it will also incorporate the exploration results from the Phase IV, 20,000m drill programme.
Diablillos Project Location
The Diablillos Project is located in the Argentina’s high Puna and Altiplano region, around 375km northwest of the city of Catamarca.
According to PFS report effective March 2024, the property includes an area of 11,403-hectares. It features 15 contiguous and overlapping concessions, which AbraSilver bought in 2016.
The project site is accessible throughout the year via a 150km paved road, followed by a well-maintained gravel road that is shared with neighbouring projects.
Diablillos Project History
Although Diablillos property witnessed exploration since the 1960s, focused activity at the site commenced in 1971.
Shell with Billiton carried out rock chip sampling and geochemical surveying from 1984 to 1985. Diablillos was with BHP until 1991.
In 1992, Pacific Rim acquired it and continued with exploration work. Barrick Exploraciones Argentina obtained an option on the shares of Pacific Rim in 1996 and commenced preliminary environmental impact and metallurgical studies.
In 2001, Silver Standard Resources acquired Pacific Rim Corporation and conducted further ground magnetic surveying and drilling on the majority of the identified targets on the property.
The Diablillos mining concessions were granted by the Government of Salta to SSRM Mining and Pacific Rim Mining, which is owned by AbraSilver.
In 2019, AbraPlata and Aethon signed binding arrangement on the property, supported by Silver Standard Resources.
AbraPlata rebranded as AbraSilver Resources Corporation in 2021.
Geology and Mineralisation
Diablillos is situated near the eastern margin of the Puna towards the intersection of the north-south trending Diablillos – Cerro Galán fault zone.
The project hosts a weathered high-sulphidation epithermal silver-gold system in Tertiary volcanic and sedimentary rocks.
Drilling activity at the property identified multiple epithermal silver-gold mineralisations including the Oculto zone, JAC zone, Laderas zone and Fantasma zone.
Several satellite mineralisation zones occur within a 500m to 1.5km distance of the Oculto/JAC epicentre.
Diablillos Project Reserves
According to the PFS, Diablillos Project contains Proven and Probable Mineral Reserves of 42.3Mt grading 91g/t Ag and 0.81g/t Au containing 210 Moz of AgEq metal.
Contained metal is estimated to be 123.5Moz of silver and 1.1Moz of gold.
Mining and Recovery
The Diablillos Project’s large, near-surface orebody will be mined using open pit mining operation.
The JAC and Oculto zones will be drilled and blasted, and the recovered material to hauled to long-term stockpiles or a run-of-mine (ROM) pad. Hydraulic shovels and loaders will be used for loading, and haul trucks for transport.
Gold and silver will be recovered via cyanidation followed by the Merrill Crowe process.
The process plant will have a nameplate capacity of 9,000tpd.
Primary crushing will reduce ROM material to a P80 of 150 microns, while the grinding circuit, with one SAG mill and one ball mill, reduces particle size to around 150 microns and hydro cyclones overflow thickened to 45% solids for leaching.
A portion of hydro cyclones underflow will pass onto two gravity concentrators. Gravity concentrate will flow into an intensive cyanidation circuit, and the gravity tails will be sent back to the ball mill.
Gold and silver in a solution phase will be recovered via intensive cyanidation and pass onto the pregnant solution tank feeding the Merrill Crowe plant, while the solids tails report back to the ball mill circuit.
The process flowsheet includes eight agitated leaching tanks to provide a 36-hour retention time, and a six-stage Counter Current Decantation (CCD) circuit to optimise gold and silver recovery.
The Merrill Crowe circuit will clarify and deaerate the pregnant solution followed by zinc precipitation to recover gold and silver.
Precipitated cake will undergo retorting to remove mercury and moisture. It is then smelted into doré, and slag is recycled into the grinding circuit.
The detoxified tailings are thickened and stored in a tailings storage facility (TSF), with process water recovered and recycled.
Key Infrastructure
The project will receive power from a 20MW hybrid power plant equipped with solar panel arrays and stationary diesel generators.
A raw water wellfield in Barranquillas district has also been identified to supply water for production and living requirements.
The locations for Tailings Storage Facility (TSF) and Waste Rock Facilities (WRF) have been identified near the plant and to the mine.
The Diablillos project will also include a service hub with main maintenance steel building (truckshop), main warehouse and lay-down area, plant and mine offices, metallurgical and chemical laboratories among others.
Contractors Involved
The updated Diablillos Project PFS was completed by a team of Mining Plus Peru, Whittle Consulting, BMining, INSA, SGS North America, and Envis Consulting.
The PFS, which was released in March 2024, was completed by SGS Geological Services, with support from Knight Piesold, SGS Bateman, Bmining (Chile), and INSA (Argentina).
