Chile

Guanaco-Amancaya Complex

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Overview

Mine TypeUnderground
Commodities
  • Gold
  • Silver
Mining Method
  • Sub-level open stoping (SLOS)
  • Vertical Crater Retreat
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ShapshotThe Guanaco-Amancaya Operation consists of the Guanaco Mine and Inesperada satellite deposit, the Amancaya Mine and the Guanaco heap leach pads (Heap Reprocessing project).

Mining at Guanaco was discontinued in February 2020. Amancaya is currently in production, while Guanaco Heap Reprocessing and Inesperada are new projects. Amancaya's Mineral Reserves will be exhausted in 2023 when Inesperada commences production. It is anticipated that the Inesperada open pit Mineral Reserves will be exhausted by the end of 2025.

The Company completed construction of the heap reprocessing project in early July 2023 and production commenced during the last week of July 2023.
Related Asset

Owners

SourceSource
CompanyInterestOwnership
Austral Gold Ltd. 100 % Indirect
Guanaco Compañía Minera Ltda. (operator) 100 % Direct
The Guanaco-Amancaya Operation is held by Austral Gold through its wholly-owned subsidiary Guanaco Mining Company Ltd (GMC). GMC has a 99.99% interest in Guanaco Compañía (Cía.) Minera SpA (GCM), the subsidiary entity in Chile that owns and currently operates the Guanaco and Amancaya mines.

Contractors

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Deposit type

  • Epithermal
  • Vein / narrow vein

Summary:

The Guanaco-Amancaya Operation is located in the Central Depression of northern Chile, which is a north-northeast striking Paleocene to early Eocene morphostructure formed as part of a volcanic arc under extensional and/or transtensional conditions. The structure extends for 3,000 km, is composed of mafic to felsic volcanic rocks of calc-alkaline affinity, typically affected by extensive alteration, and has gabbroic to dacitic intrusive and subvolcanic bodies emplaced over its length. These rocks are grouped into the Cinchado (north) and Chile-Alemania (south) formations that lie unconformably over Cretaceous volcanic rocks. During the middle Eocene, the change of convergence angle and the acceleration of subduction resulted in crustal thickening, eastward migration of the volcanic arc, and the onset of the Incaic orogeny, which uplifted the Incaic Range and produced giant middle to late Eocene copper porphyry deposits to the east.

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

The most important structural features related to gold mineralization at Guanaco follow east-west and east-northeast to west-southwest trends. Gold bearing structures are all steeply inclined ledges (veins) composed of massive vuggy and cryptocrystalline quartz of replacement origin. Individual ledges are up to five metres wide, however, more commonly they appear to comprise several impersistent siliceous strands separated by altered, but barren, wall rock. The ledge structures extend for at least four kilometres along strike, although gold concentrations are confined to relatively restricted shoots. The ledges, formerly mined underground, and afterward in the Dumbo, Defensa, and Perseverancia open pits, contain the largest mineralized shoots, which reportedly extended for up to 300 m vertically. Further west, the mineralized shoots defined to date appear to be more restricted, both laterally and vertically. For example, individual shoots discovered at Cachinalito West range vertically from 50 m to 150 m and occur at slightly different elevations along closely spaced, parallel structures rather than within a single continuous ledge.

The deposit at Amancaya is an epithermal gold-silver deposit hosted in a steeply dipping, structurally controlled quartz vein emplaced on a volcano-tectonic basin. 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 an LS type based on their metal content and the volcano-tectonic setting.

The Inesperada deposit is an HS breccia controlled epithermal gold deposit, hosted in phreatomagmatic tuffs and breccias. Alteration zonation is characterized by a silica-quartz-alunite-jarosite core surrounded by a quart-alunite-dickite alteration halo, changing outwards to a quartz-kaolinite assemblage. Gold mineralization is directly controlled by the morphology of the conduit of the phreatomagmatic unit. Mineralization depth is estimated to be greater than 100 m, the large part of which is oxide, changing below 2,400 MASL to a sulphide association of silica-quartz-alunite-pyrite alteration, with enargite and traces of chalcopyrite, chalcocite, and covellite.

Guanaco Mineralization
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 copper carbonates, silicates, and a number of rare copper arsenates (chenevixite, ceruleite) have been found in secondary-enrichment 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 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 copper. Gold grades in this zone are generally high, sometimes exceeding 50 g/t.

Inesperada Area
Phreatomagmatic tuffs and breccias occur in andesitic lava flows and their fragments are found along second order northwest-southeast structures possibly related to an extensional to transtensional tectonic regime.

Alteration is primarily associated with highly permeable phreatomagmatic rocks and strongly fractured andesitic rocks close to the contact between the units. The alteration zonation is characterized by a silica– quartz-alunite-jarosite core surrounded by a quartz-alunite-dickite alteration halo, changing outwards to a quartz-kaolinite assemblage developed over tuff and phreatomagmatic breccias. The outermost zone represents a halo of white micas that are developed mainly in the andesitic volcanic rocks.

Both gold mineralization and associated alteration are controlled by the morphology of the conduit of the phreatomagmatic unit. Mineralization depths are estimated to be greater than 100 m, with mineralization above 2,400 MASL being generally oxide and mineralization below 2,400 MASL being generally sulphide, characterized by a silica-quartz-alunite-pyrite association, with enargite and traces of chalcopyrite, chalcocite, and covellite.

Amancaya Mineralization
Amancaya is a vein hosted gold-silver deposit. The principal minerals are pyrite, galena, and sphalerite, with native gold, electrum, acanthite, chlorargyrite, and silver sulphosalts (pyrargyrite) also present. Native gold and electrum are rarely visible. There are three major veins in the mine area, the Central Norte and Central Sur veins, which have been mined, and the Oeste vein, not mined yet, all of which are quartz veins with hematite, jarosite, siderite-ankerite, and manganese oxides. The description of the veins follows.

Norte Vein
The Central Norte vein is banded and has a brecciated centre with milky quartz fragments. It extends for 850 m along strike in a N15°E direction, dipping between 77° and 90° to the east. Its thickness varies between 0.25 m and 3.0 m. It is characterized by high contents

Sur Vein
The Central Sur vein is a brecciated vein with banded quartz fragments. It extends for 600 m along strike in a N30°W direction, dipping between 59° and 88° to the east. Its thickness varies between 0.18 m and 3.5 m. It is characterized by low levels of manganese oxides, and siderite is the predominant carbonate. Galena and sphalerite become more abundant in the vein with depth.

Oeste Vein
The Oeste vein is a brecciated vein with banded quartz fragments. Based on the current knowledge, it extends for 250 m along strike in a N15°E direction, dipping between 60° and 75° to the west. Itsthickness varies between 0.5 m and 3.0 m. It is characterized by low contents of manganese oxides and carbonates.

Reserves

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Mining Methods

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Comminution

Crushers and Mills

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Processing

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Production

CommodityUnits202320222021202020192018201720162015
Gold Equivalent oz  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe67,00561,271
Gold oz  ....  Subscribe  ....  Subscribe  ....  Subscribe60,66654,07544,27539,77651,534
Silver oz  ....  Subscribe  ....  Subscribe  ....  Subscribe543,906585,20158,83247,66740,108
All production numbers are expressed as metal in doré. ^ Guidance / Forecast.

Operational metrics

Metrics20222021202020192018201720162015
Daily processing capacity  ....  Subscribe  ....  Subscribe1,500 t1,500 t
Ore tonnes mined  ....  Subscribe  ....  Subscribe  ....  Subscribe250,986 t295,481 t
Tonnes processed  ....  Subscribe  ....  Subscribe  ....  Subscribe253,024 t278,447 t505,711 t502,257 t430,480 t
Daily mining capacity  ....  Subscribe  ....  Subscribe  ....  Subscribe1,000 t

Production Costs

CommodityUnits2023202220212020201920182017
All-in sustaining costs (AISC) Gold Equivalent USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 899 / oz   943 / oz   908 / oz  
C1 cash costs Gold Equivalent USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 661 / oz   792 / oz   759 / oz  
^ Guidance / Forecast.

Financials

Units20222021202020192018
Capital expenditures M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe 12.1   8.8  
Sustaining costs M USD 9.7   6.6  
Revenue M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe 93.5   85.1  
After-tax Income M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe 17.7   3  

Heavy Mobile Equipment

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Personnel

Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Dec 31, 2021
....................... Subscription required ....................... Subscription required Subscription required Dec 31, 2021
....................... Subscription required ....................... Subscription required Subscription required Sep 20, 2023
....................... Subscription required ....................... Subscription required Subscription required Sep 20, 2023
....................... Subscription required ....................... Subscription required Subscription required Sep 20, 2023

EmployeesContractorsTotal WorkforceYear
...... Subscription required ...... Subscription required ...... Subscription required 2021

Aerial view:

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