The Guanaco Mine operates in the Antofagasta Region of Chile, producing gold and silver through cyanide leaching. Austral Gold Limited owns the operation, which began mining in 1993 under Amax and was later rehabilitated by Austral Gold between September 2009 and March 2010. Heap-leach processing restarted in September 2010 with the first gold pour in December of that year. A milling and agitated leach circuit was commissioned in 2017. Heap loading stopped that same year, and all ore went to the agitated leach circuit until February 2020. Amancaya ore continued through the mill until 2025. In 2023, reprocessing of existing heaps began, and studies are ongoing for the Inesperada mine and Dumbo clusters, with routing determined by gold head grade.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| ADR plant design throughput | 350 | m³/h | Approximate design value |
| Agitated leach plant design throughput | 1,500 | tpd | Design value |
| HPGR feed size requirement (nominal) | 5.6 | mm | F80, nominal |
| HPGR product size | 4.1 | mm | P80 |
| Heap III pre-crushed size | 5.2 | mm | Feed to HPGR |
| Grizzly oversize limit | 750 | mm | Material above this rejected |
| Maximum heap lift height | 6 | m | Static leach pad |
| Target grind size | 80–150 | μm | P80, varies with ore |
| Thickener underflow solids | 50 | % by weight | Target |
| Leach retention time (minimum) | 48 | h | Three-tank circuit |
| Filter cake moisture | <20 | % by weight | Plate-and-frame presses |
| Merrill-Crowe silver grade threshold | >15 | g/t | Preferred application |
| Merrill-Crowe silver recovery threshold | >60 | % | Preferred application |
| Heap leach start (restart) | September 2010 | Not applicable | GCM restarted processing |
| First gold pour | December 2010 | Not applicable | After restart |
| Agitated leach commissioning | 2017 | Not applicable | Constructed after Amancaya acquisition |
| Heap loading ceased | 2017 | Not applicable | All ore to mill thereafter |
| HPGR installation | 2023 | Not applicable | HRC-800 model |
Overview
The Guanaco processing facility combines two recovery routes. A permanent heap leach operation uses static pads with carbon-in-column adsorption, while a milling and agitated leach circuit treats higher-grade feed. A conventional three-stage crushing plant feeds both circuits through a reversible conveyor. The quaternary HPGR stage was added in 2023 to improve gold and silver extraction from reprocessed heap material.
Ore routing depends on feed characteristics and gold head grade. Material can pass through all four crushing stages, through the quaternary stage only, or be fed directly to the crushed ore stock heap without further crushing. Sampling determines whether ore goes to heap leach or agitated leach. The heap leach circuit includes static Phase III and Phase IV pads with pregnant and intermediate solution ponds. The agitated leach circuit comprises a closed-circuit ball mill, hydrocyclone cluster, milling thickener, three leach tanks, and a three-stage CCD wash circuit. Solution processing uses both CIC-ADR and Merrill-Crowe systems.
Key Process Stages
Conventional Crushing
Ore arrives by truck and discharges into a coarse ore bin. A grizzly above the bin prevents material larger than 750 mm from entering, and a hydraulic rock breaker handles oversized blocks. An apron feeder delivers ore to the primary jaw crusher. Discharge goes to a double-deck vibrating screen, with oversize reporting to two secondary cone crushers. Tertiary screens feed two short-head cone crushers in closed circuit. Combined screen undersize forms the final conventional crushing product, conveyed by a reversible belt to either circuit. For heap leach feed, lime is added to the conveyor ahead of the truck-loading bin.
Quaternary Crushing
The quaternary stage uses a banana double-deck screen and an HRC-800 high-pressure grinding roll in open circuit. The circuit requires a nominal feed F80 of 5.6 mm, so Heap III material can be fed directly. Heaps I and II material and fresh ore need conventional crushing first. Feed enters through a dedicated external bin loaded by front-end loader or via a transfer conveyor from the secondary and tertiary undersize line. Lime is added from a silo beside conveyor CV07.
Heap Leach and ADR
Crushed ore is trucked to the static pad and stacked in strips to a maximum lift height of six metres, then levelled by dozer. Barren solution applies through drip irrigation. Solution percolates through the heap and drains by gravity through underdrain piping to the PLS pond. The ADR plant pumps PLS through five CIC columns in series at about 350 m³/h. Loaded carbon moves counter-current to solution flow, transferred batchwise from column 5 to column 1. Fully loaded carbon goes to elution, where acid washing removes inorganic foulants. The AARL split elution uses hot sodium cyanide and caustic soda, with high-grade eluate sent to electrowinning and lower-grade eluate recycled to the next elution. Stripped carbon regenerates in a gas-fired kiln. Three electrowinning cells operate in parallel, depositing metals on steel wool cathodes. Cathode sludge is washed, filtered, dried, blended with fluxes, and smelted in an induction furnace to produce doré bars.
Agitated Leach
Ore reclaims from the covered stock heap through two vibrating feeders onto a belt conveyor to the ball mill. The single-stage mill operates in closed circuit with a hydrocyclone cluster. Cyclone underflow returns for further grinding; overflow is the circuit product at a target P80 of 80 to 150 μm. Overflow feeds the milling thickener, with underflow at 50% solids by weight going to three agitated leach tanks providing at least 48 hours retention. Cyanide addition starts in the milling circuit. Leach discharge enters the three-stage CCD wash circuit, where wash solution flows counter-currently to maximise recovery. CCD thickener 1 overflow goes to the rich solution tank and Merrill-Crowe plant. CCD thickener 3 underflow goes to filter feed, then three plate-and-frame filter presses dewater and wash tailings to below 20% moisture. Freshwater serves as filter wash water and is the primary freshwater addition.
Merrill-Crowe
The refurbished Merrill-Crowe plant treats rich solution from CCD. It is preferred when silver grades exceed 15 g/t and silver recoveries top 60%; otherwise the CIC-ADR circuit should be evaluated. Solution passes through clarification filters, then a vacuum de-aeration tower reduces dissolved oxygen. Zinc dust addition precipitates gold and silver as metallic cement, retained in plate-and-frame filter presses cleaned manually. Precipitate is dried, fluxed, and smelted. Barren solution recycles as CCD wash water.
Tailings
Filter cake discharges to a concrete-lined containment area. A front-end loader transfers tailings to haul trucks for the dry stack storage facility. Residual cyanide degrades naturally through solar ultraviolet radiation and the arid climate. Tailings are spread, irrigated, and tilled to promote degradation.
Additional Interesting Data and Summary
The processing facility began as a heap leach operation under Amax in 1993, with three-stage crushing and a plant combining Merrill-Crowe and CIC-ADR circuits. After care and maintenance from 1997, Austral Gold modernised the operation. The Amancaya acquisition led to construction of the milling and agitated leach circuit in 2017. The existing Merrill-Crowe circuit was refurbished to handle higher-silver ore from Amancaya. Heap reprocessing starting in 2023 involves excavating and re-crushing material from Heaps I, II, and III.
Several design values stand out. The agitated leach plant is designed for 1,500 tpd. The ADR plant handles approximately 350 m³/h. The HPGR delivers a final product P80 of 4.1 mm from a nominal feed F80 of 5.6 mm. The milling circuit targets a grind P80 between 80 and 150 μm depending on ore leach characteristics. Leach retention is a minimum of 48 hours. Tailings filter cake moisture stays below 20%.
The facility comprises crushing, heap leach, agitated leach, and solution processing units. Crushing includes primary jaw, secondary and tertiary cone crushers with vibrating screens, plus the HRC-800 quaternary stage. The heap leach uses static pads with PLS and ILS ponds. The agitated leach circuit has a covered ore stock heap, closed-circuit ball mill, thickener, three leach tanks, CCD wash, and filter presses. Solution processing includes the five-column CIC circuit, acid wash column, AARL split elution, electrowinning cells, and the Merrill-Crowe system with zinc precipitation. An emergency solution storage pond contains solution during extreme precipitation or abnormal conditions.
Key Processes
- Three-stage conventional crushing with primary jaw, secondary and tertiary cone crushers
- Quaternary HPGR crushing with HRC-800 high-pressure grinding roll
- Static heap leach with drip irrigation and gravity drainage to PLS pond
- Five-column CIC adsorption with counter-current carbon movement
- AARL split elution with acid wash and carbon regeneration kiln
- Electrowinning with steel wool cathodes and induction furnace smelting
- Closed-circuit ball mill with hydrocyclone classification
- Three-tank agitated leach with minimum 48-hour retention
- Three-stage counter-current decantation wash circuit
- Merrill-Crowe zinc precipitation with clarification and de-aeration
- Plate-and-frame filter press tailings dewatering
- Dry stack tailings storage with natural cyanide degradation
Source: Technical Report on the Guanaco Mine, July 21, 2026. Project website: Guanaco Mine
Technical report and processing history
The following archived source profiles have been consolidated here to preserve the project’s processing history and study context.
Guanaco Gold Project — 2016 Technical Report
Guanaco Gold Project — 2016 Technical Report
| Company | Argentex Mining Corporation |
| Date | April 2016 |
| Region | Antofagasta Province, Region II, Chile |
| Commodities | Gold, Silver |
| Throughput | 1,090 tpd |
| Mine Life | 2010 – 2018 |
| Annual Production | 50,374 oz Au |
Executive Summary
The Guanaco Gold Project, operated by Argentex Mining Corporation, is located in the Antofagasta Province of Chile. The process plant was fully refurbished and recommissioned in late 2010 and has been running continuously since. The operation utilizes a combination of open pit and underground mining to feed a conventional heap leach circuit. The Life of Mine (LOM) production plan extends through 2018, with gold production expected to decline from 2014 levels.
The processing route involves crushing open pit and underground material to a fine size suitable for heap leaching. The crushed ore is stacked on the Phase III heap leach pad, where it is irrigated with barren solution. Pregnant solution is collected and treated in an Adsorption, Desorption, and Regeneration (ADR) plant. The ADR circuit utilizes Carbon-in-Column (CIC) technology for gold adsorption, followed by AARL elution and electrowinning to produce doré bars.
Website: https://finance.yahoo.com/news/argentex-mining-announces-5-0-140600880.html
Report Date: April 2016
Region: Antofagasta Province, Region II, Chile
Project Status:
Commodity: Gold, Silver
Throughput: 1,090 tpd
Mine Life: 2010 – 2018
Mine Type:
Ore type:
Guanaco-Amancaya Operation — 2022 Technical Report
This technical report describes the processing facilities at the Guanaco-Amancaya Operation, including historical heap leach and current milling operations, as well as a proposed heap reprocessing project.
Report context
This NI 43-101 Technical Report is dated March 25, 2022 and covers the Guanaco-Amancaya Operation. The report presents the recovery methods for the operation, which includes both existing facilities and a proposed heap leach reprocessing project currently in the design and permitting stages.
Processing route
Historical heap leach operations
Guanaco operations were initiated by Amax in 1993 using a permanent leach pad, crushing, cyanide leaching, and a Merrill-Crowe plant. In 1997, Guanaco was placed on care and maintenance. Between September 2009 and March 2010, the Guanaco infrastructure, including the process facilities, were refurbished and upgraded by Austral Gold. Restart of leach pad stacking at Guanaco occurred in September 2010 and the first gold bar was poured in December 2010.
The existing three-stage crushing circuit consists of primary jaw crushing, secondary cone crushing and screening, and tertiary cone crushing and screening. Ore is trucked from the mines and dumped into a coarse ore storage bin with a grizzly positioned to prevent oversize rocks larger than 750 mm from entering. A rock breaker is available to reduce large rocks. Ore is transferred from the bin to a grizzly screen using an apron feeder. Fine material bypasses the jaw crusher while coarse material larger than 150 mm feeds the jaw crusher for primary crushing. Discharge from the jaw crusher and grizzly screen undersize is conveyed to a secondary double deck vibrating screen, with oversize feeding two secondary standard cone crushers. Discharge from secondary crushers and tertiary crusher feeds two tertiary screens, with oversize fed to two tertiary short head cone crushers. Undersize from secondary and tertiary screens is the final product. Lime is added to the conveyor feeding the truck load out bin.
The heap leach pad is designed in strips stacked to a height of three metres. After ore is dumped by trucks, it is leveled using a dozer. Irrigation drip tubes apply barren solution to the ore. Solution percolates through the pad and is collected in pipes, flowing by gravity to the pregnant solution pond. From the pond, pregnant solution is pumped to the adsorption, desorption, regeneration (ADR) plant.
The ADR plant has a design capacity of approximately 400 m³/h. The adsorption circuit consists of one train of five carbon-in-column (CIC) columns. Solution flows by gravity from column one through column five. Activated carbon is advanced counter-currently to solution flow. In the desorption circuit, carbon is first acid washed, then moved to a carbon elution column. The desorption circuit consists of two circuits operating in parallel: one designed to treat two tonnes of carbon and the second designed to treat one tonne of carbon. After elution, activated carbon is regenerated in a gas-fired carbon regeneration kiln and returned to the CIC circuit.
The elution circuit is a split Anglo American Research Laboratory (AARL) circuit. Hot caustic cyanide solution strips precious metals from the activated carbon. Eluate from the first half of the elution cycle is collected in the electrolyte tank, while solution from the second half is collected in the eluate mix tank for use in the first half of the next elution cycle. Solution from the electrolyte tank is pumped to the electrowinning (EW) circuit, where three EW cells operate in parallel. Precious metal is removed by plating onto steel wool cathodes. Sludge is dried, mixed with fluxes, and smelted in an induction furnace to produce doré bars.
Current milling operation
With the acquisition and initiation of mining at Amancaya, a milling and agitated cyanide leaching circuit was constructed at Guanaco, beginning operation in 2017. Crushed ore is delivered to the milling circuit from the existing three-stage crushing circuit. Crushed material discharges onto a reversible conveyor which feeds both the heap leach truck loading bin and the covered crushed ore stockpile at the mill.
The plant is designed to process 1,500 tpd. From the covered stockpile, two vibrating feeders draw ore from the bottom and place it on conveyors feeding the ball mill. The grinding circuit includes a single stage ball mill operating in closed circuit with hydrocyclones. Crushed ore is conveyed to the ball mill feed bin and mixed with water. Slurry discharges through a trommel screen and flows by gravity into a pump box, from which it is pumped to the cyclone cluster. Cyclone underflow returns to the ball mill, while cyclone overflow is the final product with a target grind size of P 80 150 µm.
Slurry from cyclone overflow feeds the pre-leach thickener. Underflow from the thickener, designed to produce a slurry density of 50% solids by weight, is pumped to the agitated leaching circuit. The grinding solution contains cyanide, so gold and silver dissolution begins in the grinding circuit. The leach circuit consists of three leach tanks designed to provide 48 hours of residence time. Slurry discharges from the third leach tank to the counter current decantation (CCD) washing circuit.
In the CCD circuit, leach residue advances from CCD thickener one to two and then to three. Barren solution from the Merrill-Crowe circuit is used as wash water, flowing counter current to the slurry flow. Underflow from CCD three is pumped to the filter feed tank. Two plate and frame pressure filters wash and dewater tailings to produce a filter cake containing less than 20% moisture by weight.
The existing Merrill-Crowe circuit was refurbished to accommodate ore with higher silver concentrations from Amancaya. Pregnant solution is pumped through clarifying filters and on to the de-aeration tower, a packed column operated under vacuum to remove oxygen. Zinc dust is added to the clarified, de-aerated solution where gold and silver ions are reduced to form solid metal precipitate. Solids are removed with plate and frame filter presses. Dewatered precipitate is dried, mixed with fluxes, and smelted in the existing refinery.
Washed, dewatered tailings drop by gravity into a concrete lined containment area. A front end loader places tailings into haul trucks for transport to the dry tailings storage facility (TSF). Tailings contain residual cyanide that undergoes natural degradation due to ultraviolet exposure and the dry, windy climate. Tailings are spread and plowed to assist the cyanide degradation process.
Proposed heap reprocessing project
GCM discontinued loading of the heap leach pads in 2017 and subsequently directed all ore to the mill. Ore from Guanaco was processed through February 2020. Amancaya ore is currently the primary source for mill production. Solution application on the heaps continued until operations were uneconomic, after which the ore was rinsed with water to remove residual cyanide and gold.
GCM plans to reprocess the existing heaps (Heap I, Heap II, and Heap III) by excavating the material, crushing it through a quaternary HPGR crushing circuit, and placing the crushed material on a new heap leach pad, Heap IV. A fourth stage HPGR crushing circuit will be integrated into the existing 300 tph three-stage crushing plant, which currently produces a P 80 5.3 mm product, to produce a final product of P 80 3.3 mm. The HPGR circuit design project is currently in the design and permitting stages. The HPGR circuit is in the basic engineering stage pending equipment purchases required for detailed engineering. Heap IV is in the detailed engineering stage and the required information for the permitting process is being provided.
The HPGR requires a nominal F 80 of 5.6 mm. When processing Heap III, the material can be fed directly to the HPGR circuit. When processing Heaps I and II, the material will require secondary crushing prior to the HPGR. The HPGR circuit consists of a feed hopper, screen feed conveyor, double deck screen, screen oversize conveyor feeding the HPGR, and screen undersize conveyor conveying undersized material and HPGR crushed material to the existing truck loadout conveyor.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Crushing plant capacity | 300 tph | Existing three-stage circuit |
| Final product current crush size | P 80 5.3 mm | Existing crushing circuit |
| Final product proposed crush size | P 80 3.3 mm | Proposed HPGR circuit |
| HPGR nominal feed size required | F 80 5.6 mm | Design specification |
| ADR plant design capacity | 400 m³/h | Design |
| Heap leach pad lift height | 3 m | Design |
| Mill design throughput | 1,500 tpd | Design |
| Target grind size | P 80 150 µm | Design |
| Leach circuit residence time | 48 hr | Design |
| Pre-leach thickener underflow density | 50% solids by weight | Design |
| Filter cake moisture content | <20% moisture by weight | Design |
Project website: https://australgold.com/projects/operations/chile-guanaco-amancaya-mine-complex/
Technical qualifications
The HPGR circuit design project is currently in the design and permitting stages. The HPGR circuit is in the basic engineering stage pending equipment purchases required for detailed engineering. Heap IV is in the detailed engineering stage and the required information for the permitting process is being provided.
GCM discontinued loading of the heap leach pads in 2017 and subsequently directed all ore to the mill. Ore from Guanaco was processed through February 2020. Amancaya ore is currently the primary source for mill production.
An intermediate pond is available for use as part of a solution enrichment system but has never been used.
Source: Guanaco-Amancaya Operation , 2022 Technical Report, Section 17.0 Recovery Methods, dated March 25, 2022.
