Summary:
The Project is in the Tintina Mineral Belt, which is a 200 km-wide, 1,200 km-long arc, broadly bounded by the Tintina-Kaltag fault systems to the north and the Denali-Fairwell fault systems to the south. The region contains numerous economic deposits of gold in addition to copper, lead, zinc, silver and tungsten deposits.
The lithological units in the Pogo deposit area are dominantly high-grade metamorphic rocks intruded by later felsic to intermediate intrusive units. Key metamorphic rocks include biotite feldspar gneiss, augen gneiss and mafic schist derived from both sedimentary and igneous protoliths. Metamorphic mineral assemblages observed consist of quartz, feldspar, biotite, chlorite, muscovite, sillimanite, andalusite and garnet. The 50km long Goodpaster batholith (granite-tonalite-diorite) is the dominant intrusive complex in the district. Locally small felsic to intermediate stocks and dykes are present. The principal mineralisation is hosted in biotite-quartz-feldspar paragneiss and orthogneiss, although all other lithologies are cut. Where the veins cross intrusives, they tend to split and become stockwork zones.
Gold at Pogo is predominantly hosted within laminated quartz veins ranging in thickness from <0.5 m to >10 m. Mineralised veins contain around 3% sulphides (arsenopyrite, pyrite, pyrrhotite, loellingite, chalcopyrite, bismuthinite, sphalerite, galena, molybdenite, tetradymite, maldonite) and a variety of Bi-Pb-Ag sulphosalts.
The Pogo gold deposit is an example of a Reduced Intrusive Related Gold Deposit (RIRGD), characterised by a low sulphide content, (typically <5%) and a reduced ore mineral assemblage, that typically comprises pyrite and lacks primary magnetite or hematite. In brief, these deposits typically have the following characteristics:
- Mineralisation occurs as sheeted vein deposits or stockwork assemblages and often combines gold with variably elevated Bi, W, As, Po, Py, Mo, Te, and/or Sb, but low concentrations of base metals.
- Restricted and commonly weak proximal hydrothermal alteration
- Spatially and temporally related to reduced intrusions of intermediate to felsic composition.
Dimensions
Liese – The generally shallowly north-westerly dipping Mineral Resource extends approximately 1,300m in a north-easterly direction along strike and 1,300m down dip.
Eastern Deeps – The shallow to moderately north-westerly dipping Mineral Resource extends approximately 530m in a north-easterly direction along strike, and 600m down dip.
North Zone – The steeply east dipping Mineral Resource extends approximately 950m in a northerly direction along strike, and 970m down dip. A flatter component, dipping west, extends 250m by 190m.
South Pogo – The moderately north-westerly dipping Mineral Resource extends approximately 1100m in a north-easterly direction along strike, and 760m down dip.
Fun Zone – the generally moderate to steep-westerly dipping Mineral Resource extends approximately 880m in a westerly direction across strike, 650m in a northerly direction across- strike and 915m down dip.
Central Zone - The shallow to moderately north-westerly dipping Mineral Resource extends approximately 750m in a north-easterly direction along strike, and 500m down dip.
Hill 4021 – the Hill 4021 prospect consists of two zones of stacked, shallowly dipping mineralised structures with combined extents approximately 1,900 m in a north-westerly direction along strike and 500 m down dip.
Goodpaster is situated ~1,500 m northwest of the nearest Pogo underground development. The deposit is laterally extensive occupying an approximate footprint of 1,830 m by 760 m with a width up to 550 m. Lode orientations are variable but broadly dip ~30° to 280° however conjugate orientations are common.