Australia

Cosmo Mine

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Overview

Mine TypeUnderground
StatusClosing / Closed
Commodities
  • Gold
Mining Method
  • Open stoping
  • Cut & Fill
  • Cemented (undefined) backfill
ShapshotThe Cosmo Mine ceased production in February 2020. Work commenced on the Cosmo Howley rehabilitation strategy in October 2020, under Kirkland Lake Gold ownership, and Agnico Eagle continued implemention of this closure strategy following the merger. Although reclamation is a legislative requirement, the manner it is executed is determined by the company that owns the property. The work at the site aligns with Agnico Eagle’s regulatory and risk based approach to remediate land in a manner that allows for future land use when possible.

Reclamation of a 100-year-old mining camp is underway. Acid generating waste rock was excavated and placed into the Cosmo Pit. This waste was layered with non-acid generating waste rock then submerged under 19 metres of water to inhibit acid rock drainage.

Owners

SourceSource
CompanyInterestOwnership
Agnico Eagle Mines Ltd. 100 % Indirect
NT Mining Operations Pty Ltd. (operator) 100 % Direct
February 8, 2022 – Agnico Eagle Mines Limited and Kirkland Lake Gold Ltd. are pleased to announce the successful completion of the previously announced merger of equals transaction (the “Merger”).

The combined company will continue as Agnico Eagle Mines Limited.

Deposit type

  • Vein / narrow vein
  • Orogenic

Summary:

A variety of genetic models, ranging from magmatic through hydrothermal to syngenetic, have been postulated in the past for the formation of gold deposits in the Pine Creek Geosyncline. Gold and base metal mineralization in the Pine Creek Geosyncline is commonly associated with granite intrusions and have often been classified as high temperature contact aureole deposits. A secondary host rock control has also been suggested due to the association of gold mineralization with carbonaceous metasedimentary rocks, such as at Cosmo Mine.

Native gold is the main mineralization mineral and is commonly present as micron sized grains; coarse nuggets are rare. Gold is commonly associated with pyrite, arsenopyrite and pyrrhotite and in places with minor base metal sulphides. Quartz, chlorite, sericite and carbonates are the common gangue minerals in the gold-quartz deposits.

All gold deposits in the Northern Territory show some structural control at the regional and deposit scales, with most deposits within the Pine Creek Orogen trending northwest southeast.

Base metal mineralization in the Pine Creek Orogen strike significantly differently than the gold veins, suggesting different discrete mineralizing events. They are syngenetic.

Cosmo gold mineralization is hosted across a stratigraphic sequence (‘Cosmo Mine Sequence”) that lies between a major dolerite sill (‘Zamu’ dolerite unit) and a thick package of high sulfide, graphitic mudstone (‘Pmc’ unit). This sequence is folded across the major Cosmo Howley Anticline with numerous limb parallel faults found to splay and roll inwards across the anticline nose as they migrate northwards down plunge. Also of major significance is the shallow (-40o to -55o) east-west F1 Fault which shows local steps and thrust related jogs and is suggested to be at least partly contemporaneous with limb parallel faults. The majority of gold mined to date comes from within ~200m above or below the F1 Fault so an empirical major control on mineralization is credited to this fault.

Reserves

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Mining Methods

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Comminution

Crushers and Mills

Milling equipment has not been reported.

Summary:

ROM ore is crushed at a rate of up to 2.5Mtpa in a three stage crushing circuit incorporating a primary jaw crusher operating in open circuit and a secondary and tertiary cone crushers operating in closed circuit with a double deck banana screen. Crushing circuit product, at a nominal size of 12mm is conveyed to the grinding circuit via the Fine Ore Bin (“FOB”).

The FOB, with a live capacity of 2,500 tonne, provides a buffer of approximately seven to eight hours between the crushing and grinding circuits. Ore is reclaimed via a slot feeder at a variable rate and is conveyed to the grinding circuit.

As the crushing circuit capacity exceeds that of the milling circuit, crushed ore is stockpiled and fed back into the grinding circuit using a front end loader into an emergency feed hopper and feeder arrangement.

Crushed ore is ground in the grinding circuit consisting of two ANI single stage rubber lined ball mills operating in closed circuit with a nest of Warman cyclone classifiers. A proportion of ball mill discharge is directed to the gravity circuit incorporating four Knelson concentrators, two per mill. Knelson concentrator tailings report back to the mill discharge stream whilst the concentrated coarse gold is sent to the gold room for further processing.

Processing

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Production

CommodityUnits20172016
Gold oz 20,59555,764
All production numbers are expressed as metal in doré.

Operational metrics

Metrics20172016
Tonnes milled 259,729 t646,848 t
Annual mining capacity 2 Mt

Production Costs

CommodityUnits2017
Cash costs (sold) Gold USD 1,661 / oz  
All-in sustaining costs (sold) Gold USD 1,996 / oz  

Financials

Units2017
Capital expenditures M USD 7.5  
Revenue M USD 27.4  
Operating Income M USD -33.5  
Pre-tax Income M USD
After-tax Income M USD

Heavy Mobile Equipment

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Personnel

Mine Management

Source Source
Job TitleNamePhoneEmailProfileRef. Date
....................... Subscription required ....................... Subscription required ........... Subscription required ........... Subscription required Oct 6, 2023
....................... Subscription required ....................... Subscription required Subscription required Apr 15, 2024
....................... Subscription required ....................... Subscription required Subscription required Apr 15, 2024

EmployeesYear
Subscription required 2022
Subscription required 2021

Aerial view:

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