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Mount Coolon Project

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Mine TypeOpen Pit & Underground
StagePreliminary Economic Assessment
  • Gold
Mining Method
  • Truck & Shovel / Loader
  • Longhole stoping
Mine Life... Lock


GBM Resources Ltd. 100 % Indirect
The Mount Coolon Project is located in the Drummond Basin in Queensland. Tenements and resources are owned by the GBM’s 100% owned subsidiary, Mount Coolon Gold Mines Pty. Ltd.



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Deposit type

  • Breccia pipe / Stockwork
  • Epithermal
  • Vein / narrow vein


The MCSS (Mount Coolon Scoping Study) evaluates the economic potential of three deposits which includes Eugenia, Koala & Glen Eva.

Auriferous epithermal veining at Koala is hosted in a thick package of shallow dipping andesitic to rhyolitic volcanic flows, which form part of the regional Drummond Basin Cycle 1 sequence. The Koala gold mineralisation lies approximately 500m east of a major granodiorite intrusion and is preferentially hosted by porphyritic andesite.

High grade gold mineralisation at Koala occurs in a narrow, steeply dipping high grade colloform quartz vein sporadically enveloped by a wider lower grade, veinlet stockwork and is locally disrupted by faulting. The main vein has been defined by drilling over a strike length of about 1,200m and down dip about 200m.

The main vein is offset by steeply dipping, west-northwest striking cross faults with high grade zones sometimes formed at the intersection of the cross faults and the main vein. The most significant cross fault is the Sullivan Fault which forms a zone about 20m wide at the south end of the Ross Mining pit.

The main vein changes dip direction along strike. In the south it dips steeply to the west, whereas in the north it dips steeply to the east. The main vein splits into a series of splay veins at the southern end. To the North the up-dip extent of the main vein appears to be capped by a rhyolitic unit which results in a gentle north plunge to the mineralisation.

A number of alteration styles are evident including silica – sericite – pyrite + K-Feldspar associated with gold mineralisation.

Weathering varies significantly in both depth and intensity across the deposit. North of Sullivan’s fault weathering is intense and extends to about 60m below surface. South of Sullivan’s fault weathering is weak with fresh pyrite observed at surface and logged weathering rarely extending more than 15m below surface.

Glen Eva
Au-Ag mineralisation at Glen Eva occurs within a predominantly dacitic volcanic sequence of the Silver Hills Volcanics and is overlain by 20m to 30m of strataform siliceous material (previously interpreted as sinter). The sequence dips NW at about 25º. Lateritised Tertiary sediments up to 10m thick unconformably overlying the silicified zone.

Mineralisation occurs as epithermal colloform and crustiform quartz veins within tectonically and hydrothermally brecciated dacitic volcanics. Quartz veins are often brecciated and exhibit multiple phases of re-sealing. Abundant dark pyritic bands are seen in the quartz veins and these are thought to host sporadic ‘bonanza’ gold grades. The hydrothermal breccia, as defined by >10% logged quartz, forms a funnel shape (in section) flaring up to the base of the silicified zone.

The system is structurally complex with multiple mineralisation episodes and cross faulting. The main fault zone strikes WNW and dips steeply northwest. The main fault zone is inferred to be the feeder conduit to the overlying, gently NW dipping silicification zone (‘sinter’). Quartz veining and silicification occur along the main fault, as moderately NE dipping splays and subparallel to the overlying silicification zone. High grade gold mineralisation occurs on the main fault and in the NE dipping splays, with grades in the NE splays generally decreasing away from the main fault. Alteration is dominated by sericite – pyrite near the veins and grades out to chlorite – calcite – pyrite.

The gold mineralisation at Eugenia is a complex arrangement of at least 5 styles of structurally-controlled quartz veins and sulphide disseminations, characteristic of a low sulphidation epithermal deposit type. The host rocks are crystal-rich dacitic ignimbrites located in the Devono-Carboniferous Drummond Basin. The host units are reported to have a shallow dip to the west combined with inferences of a steeper ‘feeder’ zone in the centre of the mineralisation. An intermediate argillic alteration assemblage is extensively developed at Eugenia, which exhibits both vertical and lateral zonation. Higher grade gold mineralisation occurs as quartz-carbonate veins and horizons within the porous host lithologies. Outcrop is very limited with thick soil cover, namely the Tertiary Suttor Formation to the north and Quaternary sands to the south.

The weathering profile has been interpreted as a truncated lateritic profile with depth to fresh rock averaging 50m below surface. There is evidence of localised supergene enrichment of the gold associated with the base of oxidation.

A lack of drilling suggests the mineralisation is open along strike and at depth. A number of drill holes have terminated in significant gold mineralisation Oxidation due to weathering has been defined by logged codes and low value sulphur assays. There is evidence of gold enrichment at the base of the oxide zone Geological understanding appears to be good and appropriate for resource estimation.



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Mining Methods


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Crushers and Mills


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Gold koz 155
All production numbers are expressed as metal in doré.

Operational metrics

Stripping / waste ratio 4.6 *
Waste tonnes, LOM 13,735,000 t *
Ore tonnes mined, LOM 2,998,000 t *
Total tonnes mined, LOM 16,733,000 t *
Tonnes processed, LOM 3 Mt *
* According to 2017 study.

Production Costs

All-in sustaining costs (AISC) Gold 1,020 / oz *  AUD
C1 cash costs Gold 909 / oz *  AUD
Assumed price Gold 1,250 / oz *  USD
* According to 2017 study / presentation.

Operating Costs

OP mining costs ($/t mined) AUD 4 *  
UG mining costs ($/t mined) AUD  ....  Subscribe
* According to 2017 study.

Project Costs

MetricsUnitsLOM Total
Pre-Production capital costs $M AUD  ......  Subscribe
Sustaining CapEx $M AUD  ......  Subscribe
OP OpEx $M AUD  ......  Subscribe
UG OpEx $M AUD  ......  Subscribe
Processing OpEx $M AUD 63.2
Total OpEx $M AUD  ......  Subscribe
Royalty payments $M AUD  ......  Subscribe
Gross revenue (LOM) $M AUD  ......  Subscribe
Pre-tax Cash Flow (LOM) $M AUD  ......  Subscribe
Pre-tax NPV @ 10% $M AUD  ......  Subscribe
Pre-tax NPV @ 8% $M AUD  ......  Subscribe
Pre-tax IRR, %  ......  Subscribe
Pre-tax payback period, years  ......  Subscribe

Heavy Mobile Equipment

Fleet data has not been reported.


Mine Management

Job TitleNamePhoneEmailProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Feb 6, 2024
....................... Subscription required ....................... Subscription required Subscription required Dec 4, 2017
....................... Subscription required ....................... Subscription required ........... Subscription required ........... Subscription required Subscription required Feb 6, 2024

Aerial view:


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