Name of the Mine
Kalgoorlie Consolidated Gold Mines (KCGM) Operations.

Location  
Adjacent to the City of Kalgoorlie-Boulder, in Western Australia.

Mine Owner/s  
Northern Star.

Brief Description  
The KCGM Operations form part of the Kalgoorlie Production Centre and are simple, large-scale mining operations.

KCGM include the Fimiston openpit (Super Pit), the Mt Charlotte underground mine and the Fimiston and Gidji processing plants.

Brief History  
KCGM is located on the Golden Mile, one of the world’s richest gold deposits.

In the 1980s, Western Australian businessman Alan Bond started to acquire the individual leases along the Golden Mile to consolidate them into one company.  While Bond’s company failed to complete the takeover, the entire area was combined in 1989.

KCGM was founded to manage the KCGM Operations, owned by joint venture (JV) parties Normandy Australia and Homestake Gold of Australia.

Existing smaller pits were amalgamated into the Super Pit. All underground operations were phased out except for the Mt Charlotte underground mine, and the Fimiston and Gidji processing plants were built.

Barrick Gold Corporation and Newmont Goldcorp Corporation owned the KCGM Operations in a 50:50 JV until November 2019. In January 2020, they sold their 50:50 interests in the KCGM Operations to Saracen Mineral Holdings and Northern Star respectively, resulting in the KCGM Operations becoming 100% Australian-owned for the first time in its 31-year history on January 3, 2020.

When the merger by scheme of arrangement between Northern Star and Saracen was implemented in February 2021, the KCGM Operations became controlled by one entity, Northern Star – the first time in its history. The KCGM Operations JV was terminated on June 30, 2021.

Primary Metals/Minerals  
Gold.

Secondary Metals/Minerals  
Not stated.

Geology/Mineralisation  
The Golden Mile at the centre of the Kalgoorlie goldfield is one of the richest gold deposits in the world.

The goldfield is between 2.6-billion and 2.9-billion years old and is part of the Norseman-Wiluna belt, a greenstone belt comprising volcanic and sedimentary rocks belonging to the Archaean period, and surrounded by extensive granite.

The stratigraphy of the Kalgoorlie area comprises a 1 500-m-thick stratigraphic succession of mafic-ultramafic volcanic rocks that are unconformably overlain by a 3 000-m-thick succession of volcanic and sedimentary rocks. The volcanic rocks include lavas and pyroclastic flows. This succession is interbedded with siltstone and sandstone, and is unconformably overlain locally by a unit of poorly sorted sandstone and conglomerates.

The deposit encompasses a series of mineralised faults, known as lodes, and were formed by ancient shears, mainly occurring in a host rock known as the Golden Mile dolerite. Two mineral styles are present: the Fimiston style comprises classic Golden Mile lodes with abundant sulphides and tellurides, and the Charlotte style comprises younger white quartz veins, which have also been found in other smaller deposits in the area.

More than 1 000 ore lodes occur within the Golden Mile, some extending up to 1 800 m long, 1 200 m deep and 10 m wide. They are within an area more than 5 km long, 1 km wide and more than 1 km deep.

Reserves  
Not stated.

Resources  
Total measured, indicated and inferred resources as at March 31, 2021, were estimated at 526.7-million tonnes grading1.6 g/t gold.

Mining Method  
Openpit and underground.

The extensive underground network of historical workings throughout the Golden Mile has shaped the way the Super Pit has been mined over the past 30 years. 

Major Infrastructure and Equipment  
Ore is transported from the Fimiston openpit by haul trucks and stockpiled at the run-of-mine pad, where is it is crushed and then treated at the Fimiston plant using flotation and conventional carbon-in-leach (CIL) circuits, which include semiautogenous grinding and ball mills. A sulphide concentrate, produced as one of the CIL streams, is transported 17 km north of Kalgoorlie-Boulder to the Gidji plant for further processing using ultrafine grind (UFG) mills.

The majority of waste rock from the Fimiston openpit is placed in waste rock dumps. These dumps will remain in situ after the mine’s closure. Tailings from the Fimiston plant are pumped to the Fimiston I, Fimiston II and Kaltails tailings storage facilities.

The sulphide concentrate from Fimiston plant is processed using UFG methods at Gidji. Tailings from the Gidji plant are disposed of in the Gidji tailings storage facilities to the north of the plant.

Prospects  
None stated.

Contact Details
Northern Star, tel +61 8 6188 2100 or email info@nsrltd.com

Sources
Northern Star. Kalgoorlie Consolidated Gold Mines: Mine closure plan 2018 (December 2019)
Northern Star.  https://www.nsrltd.com/ (accessed August 12, 2021).