Summary:
The Mt Gibson Gold Project tenements are located at the southern extremity of the Retaliation Greenstone Belt, in the SW portion of the Yalgoo-Singleton Greenstone Belt in the Murchison Province of the Yilgarn Craton. The tenements are mostly covered by a veneer of alluvial quartz sands and laterite gravels, with sporadic greenstone subcrop and outcrop, increasingly exposed in the north of the project area. The mineralised laterite gravels are situated slightly down-slope from the lode deposits on the Gibson trend. Regionally, the greenstone belt has been metamorphosed to middle amphibolite facies and hosts a number of Au-Cu deposits and prospects, including Golden Grove, 90km to the northwest of Mt.Gibson.
he deposit has been defined by drilling over an 8km strike length and as deep as 950m down-dip where it is still mineralised and open down-dip. The mineralised shoots are present in drilling as broad zones up to 50m wide and are continuous down plunge. It is thought the shoots are developed in dilation zones along the main structures. A large laterite and oxide weathering zone is developed over the primary geology and this is mineralised in the near surface, up-dip position of the main shoots of primary mineralisation. A thin veneer of transported sand and colluvium soil covers the deposit and is typically less than 6m thick, the transition/fresh rock boundary is about 40 to 60m below surface.
The lode style mineralisation at Mt. Gibson is predominantly hosted by three main trends:
The Gibson Trend
The majority of the known and mined mineralisation is hosted by this trend. It is hypothesised to have originally been a gold-copper-zinc rich Volcanogenic Hosted Massive Sulphide (VHMS) deposit that has been overprinted by a later hydrothermal gold mineralising event. This mineralised shear zone has an arcuate north-south to northeasterly strike (trending more north-easterly in the north) and extends for more than seven kilometres from the southern granite contact to beyond the Hornet ore body.
The so-called “Mine Sequence” is around 400 metres wide and consists of a parcel of sheared, metamorphosed and chlorite-biotite-muscovite altered mafic volcanics. Numerous felsic porphyries intrude the Mine Sequence. Mineralisation is hosted within multiple sets of elongate lodes with strong strike continuity, which anastomose and pinch-swell along strike and to depth. The main lode systems include Hornet, Enterprise, Orion and S2.
The Taurus Trend
The north-westerly trending Taurus Trend lies west of and diagonal to the Gibson Trend. Mineralisation is intimately associated with an apparently continuous felsic unit emplaced into the northwest trending shear and was discovered late in the life of the mining operation. It is characterised by discontinuous ore bodies, and strongly mineralised quartz-sulphide veining. The ore bodies on this trend include Sheldon and Wombat which, although not as continuous in strike as the ore bodies on the Gibson Trend, show a higher gold tenor.
The Highway Trend
The Highway Trend is a northeast trending shear zone, hosted by a mafic sequence in the western terrain, 11km northwest of the main mining area. This trend hosts the Highway ore body, and the Phoenix and Aquarius Prospects. It shares many of the characteristics of the Gibson trend, but it appears to lack the VHMS mineralising event and has generally been regarded as a predominantly low-grade system, although work from previous explores suggest it may have greater persistence and significance than previously thought and hence justifies further attention. The project area also hosts a number of BIF and quartz hosted small mineral occurrences including Paynes-Crusoe and MacDonald’s Find.
The MGGP mineralisation wireframes have been projected down-dip based on wider spaced drilling intercepts; however, this extrapolation has been removed from the resource estimate by limiting the reported tonnes and grade to within a conceptual optimal pit shell ($2,200/oz Au). The main laterite zone extends 3000m along strike and 500m across. It ranges from 2m to 8m in vertical thickness, although a large portion of the laterite Resource is depleted by historical mining and backfilled with waste.
The primary mineralisation extends below the laterite zone for a further vertical depth of 950m.
The transition/fresh rock boundary is about 40 to 60m below surface. The primary mineralisation has 3 main sub-parallel zones and several smaller zones. Overall these zones extend for 8000m along strike (N-S) and up to 1000m across.
Production
Gold production averaging 152,000 ounces per annum over the project’s first 7.5 years of operation and average annual production of 138,000 ounces per annum over 10 year life of mine (LOM).
| Commodity | Units | Avg. Annual | LOM |
|
Gold
|
koz
| 152 | 1,340 |
All production numbers are expressed as metal in doré.