GUANACO
The Guanaco deposits are considered examples of high-sulphidation epithermal systems.

Native gold forming lamellae and coarse and fine grains is the most important economic mineral, although it is rarely visible. Disseminated pyrite is the most common mineral in the non-weathered mineralized material; enargite, luzonite, and minor chalcopyrite are present in the deeper horizons. Chalcocite and covellite, together with Cu carbonates, silicates, and a number of rare Cu arsenates (chenevixite, ceruleite) have been found in secondaryenrichment zones.

Important gangue minerals are quartz, tabular barite, pink alunite, kaolinite (in substitution of feldspars in zones affected by advanced argillization), hematite, chlorite, and epidote. Pervasive silicification commonly replaces all the primary rocks, whereas vuggy silica resulting from extreme acid leaching is a preferred host of the gold mineralization.

In the Cachinalito vein system, the economic mineralization appears to form 50 m to 150 m long clusters, locally known as “bolsones”. A narrow vertical range (less than 150 m) corresponding to relatively restricted paleo-depth conditions seems to have been relevant for economic gold deposition. The majority of the gold mineralization is concentrated between the 2,500 MASL and 2,650 MASL. High-grade shoots (up to 180 g/t Au), 0.5 m to 3.0 m wide, have been mined. Lower-grade halos, below 2 g/t Au, reach 20 m in width.

The oxidation zone extends down to 150 m, and is relatively free of Cu. Au grades in this zone are generally high, sometimes exceeding 50 g/t.

Quillota
The Quillota deposit consists of a vein system that has an area of approximately 200 m long (north–south) by 500 m wide (east–west). The deepest drill hole reached approximately 210 m depth. The main mineralization at Quillota was open pit mined to a depth of approximately 40 m.

Defensa
The Defensa vein system occupied an area of 300 m north–south by 600 m east–west. The deepest drill hole reached 160 m depth. Mineralization was exploited using open pit methods.

Perseverancia
The deepest drill hole reached 270 m at Perseverancia, with the vein system encountered to approximately 160 m vertical depth. Mineralization was defined over an area of 300 m (north–south) by 600 m (east–west). Mining was by open pit methods.

Dumbo
The Dumbo vein system occupies an area of approximately 250 m north–south by 500 m east–west. The deepest drill hole reached 300 m; the vein system reaches approximately 250 vertical metres depth. Dumbo has been mined by an open pit operation.

Cachinalito
As a result of the 2014-2015 drilling campaign, a clear continuity has been established between nearly all previously known sectors in Cachinalito, so that it is now recognized as a single, 1,100 m long, east–west-oriented system.

Cachinalito Central extends for approximately 150 vertical metres from surface, and the deepest drill hole is 300 m. The mineralization has been defined over an area of 100 m north–south by 700 m east-west. Cachinalito Central is currently being mined by underground methods. Aurora is a new vein, discovered during the 2014-2015 drilling campaign between Cachinalito Central and the Soledad property.

Cachinalito West covers an area of approximately 70 m north–south by 400 m east–west. Veins do not crop out at surface. Drilling encountered the veins from approximately 40 m to a maximum of 130 m vertically. The deepest drill hole is currently 340 m.

Natalia
Natalia is a northwest-oriented vein system. The central part covers an area of 200 m north– south by 450 m east–west.

AMANCAYA
The deposit at Amancaya is an epithermal gold and silver deposit, hosted in a steeply dipping structurally controlled quartz vein. Gold mineralization comprises disseminations of native gold and silver, electrum, silver sulphosalts, and accessory sphalerite, galena, chalcopyrite, and pyrite occurring with quartz, adularia, carbonates, clay minerals, limonite, and manganese oxides. These minerals were deposited from boiling of dilute saline fluids circulating in a hydrothermal system driven by the Eocene to Paleocene magmatism. The hydrothermal vein systems are considered a low sulphidation type based on their metal content and the volcanotectonic setting.

The most relevant mineralization from an exploratory point of view corresponds to the low sulphidation epithermal veins rich in gold and silver. These structures are distributed to the east of the La Peineta Fault System, along a north-south corridor of approximately two kilometres by eight kilometres (Central Veta Sector and Rosario del Llano Mine). They are mostly housed in the basal units of Paleocene (Chile-Alemania Formation, e.g., Amancaya Breccia).

In the Cerro Morros Blancos sector towards the southeast of the Central Vein, there is an area of advanced argillic type alteration that affects the basal units of the Paleocene. This sector is characterized by the presence of fault breccias with alunite and kaolinite, and subhorizontal silicified layers.

To the west of the Peineta Fault system there is mineralization of which the most important is the gold-copper veins of the Amancaya West sector. The veins strike north-south, 020° and 330° possibly associated with a porphyritic system of the Upper Cretaceous. In this sector, moreover, manifestations of IOCG mineralization linked to the Fm. La Negra, have been found.

Finally, thick quartz epithermal veins with iron and copper oxides are recognized in the sector Northwest sector, embedded in Devonian and Triassic units (Las Tórtolas formation and Agua Verde Granodiorite).

All of the veins that occur at Amancaya can be subdivided into two groups according to host units.
• Veins hosted in dacite-andesite domes (Central, Griega, Inesperada, and Cerro Amarillo).
• Veins hosted by breccias, tuffs, and volcanoclastic rocks (Rosario del Llano, Janita, Rosa, Nueva, and Julia etc.).

The main veins have been grouped within the Southern Block (Veta Central, Veta Griega, Veta Julia), and North Block (Veta Janita, Veta Nueva, Veta Rosa, Veta Laureana, Rosario del Llano, etc.).

During the 2020 year mining continued at the Amancaya underground operations while at the Guanaco underground operations mining was only in the first half of 2020.

Guanaco mine
The mining methodology used at Guanaco consists of sub-level open stoping (SLOS) and mining is carried out by following the veins with drifts on two levels, separated by 16 m (20 m floor to floor). The main production at Guanaco comes from the Cachinalito West vein, with additional production coming from the Dumbo and Perseverancia veins.

Stopes are designed at a minimum mining thickness of 1.5 m with planned dilution of 0.5 m on either side resulting in final stope widths of 2.5 m. Drifts are designed at 3.5 m with 0.25 m of dilution on either side resulting in a final width of 4 m. Sill pillars of four metres in height are left every 40 m (vertical) and ten metre wide rib pillars are left every 70 m (horizontal).

Guanaco will use the vertical crater retreat (VCR) to connect the upper and lower drifts and create and open face for long hole blasting.

Amancaya mine
The Amancaya Mine underground Mineral Reserves were estimated based on stope designs applied against the Mineral Resource block models for the Central Vein deposit. Planned and unplanned dilution are included in the stope shapes which have been designed for a sub-level stoping mining method.

The sub-level open stoping (SLOS) mining methods employed are similar to those used at the Guanaco Mine. The Amancaya orebody is generally thinner than Guanaco resulting in the use of split-blasting to minimize dilution during drift development. Split blasting involves the separate blasting of ore and waste in the drift face.

Similar to Guanaco, Amancaya will use the vertical crater retreat (VCR) to connect the upper and lower drifts and create and open face for long hole blasting.

21 December 2020 - Austral Gold Limited has decided to outsource its underground mine operation at Amancaya mine.

Crushing
Ore is trucked from the mines and dumped into a coarse ore storage bin. A grizzly is positioned over the bin to prevent oversize rocks (i.e., larger than 750 mm) from entering the bin. A rock breaker is available to reduce the size of large rocks. Ore is transferred from the bin to a grizzly type screen using an apron feeder. Fine material that passes through the screen bypasses the jaw crusher and coarse material (i.e., larger than 150 mm) is fed to the jaw crusher for primary crushing. Discharge from the jaw crusher and the grizzly screen undersize is conveyed to the secondary screen, which is a double deck vibrating screen. Oversize from the secondary screen feeds the two secondary standard cone crushers. Discharge from the secondary crushers as well as discharge from the tertiary crusher feeds two tertiary screens. Oversize from the tertiary screens is fed to two tertiary short head cone crushers. Undersize from the secondary and tertiary screens is the final product from the crushing circuit. The final product is conveyed to a bi-directional conveyor which can direct the crushed ore to the truck load out bin. Lime is added to the conveyor that feeds the bin. Trucks are loaded from the bin and transport ore to the permanent leach pad. When the conveyor is operated in the opposite direction, it is conveyed to the covered crushed ore stockpile to be fed to the mill.

Milling
From the covered stockpile, two vibrating feeders are used to remove ore from the bottom of the stockpile and feed it to a series of conveyors that are used to feed the ball mill.

The grinding circuit includes a single-stage ball mill that operates in closed circuit with hydrocyclones. The crushed ore is conveyed to the ball mill feed bin where it is mixed with water for grinding. The slurry discharges from the mill through a trommel screen and flows by gravity into a pump feed box. From the box, the slurry is pumped to the cyclone cluster. The cyclone underflow is returned to the ball mill for further grinding. The cyclone overflow is the final product from the grinding circuit. The target grind size is P80 150 µm.

Between September 2009 and March 2010, the infrastructure, including the process facilities, at Guanaco were refurbished and upgraded by Austral Gold. GCM restarted leach pad stacking in September 2010 and the first gold bar was poured in December 2010. With the acquisition and start of mining at Amancaya, a milling circuit was constructed at Guanaco. The plant began commissioning in March 2017. The commissioning phase was completed in November 2017. The Amancaya ore is being trucked to the new plant at Guanaco for processing.

The new plant is integrated into the existing operation in order to minimize construction and capital costs as much as possible. The existing crushing operation will be utilized to prepare feed for the milling circuit. The existing Merrill-Crowe circuit was refurbished to accommodate ore with higher silver concentrations from Amancaya and the zinc precipitate that is produced in the Merrill-Crowe circuit will be processed in the existing refinery.