Summary:
Bartons, Crossing, Genie, Hopetoun and Red Ensign deposits are situated within tenements forming part of the greater Nullagine Gold Project.
The Beatons Creek Project is formed part of the Nullagine Gold Project. At Beatons Creek Project, mineralization is present as either fluvial channel or marine lag conglomerates. Marine lags (Grant’s Hill, Grant’s Hill South, Edwards, Central, North and Central North). Fluvial channels (South Hill and part of Golden Crown). Complex interplay of lags and channels (part of Golden Crown).
The Nullagine Gold Project deposits at large (excluding the Beaton’s Creek deposit) are hosted within the sediments of the Mosquito Creek Basin (MCB); a Meso-Archaean sequence of fluvial / alluvial coarse clastic sediments attributed to fluvio-deltaic fan facies, and the accompanying fine-grained sediments of deeper water turbiditic sequences.
The MCB overlies the suture between the greenstone belts of the McPhee Dome and Mt Elsie Greenstone Belt to the north (the East Pilbara Greenstone Terrane) and the Kurrana Granitoid (Kurrana Terrane) to the south.
Mineralisation at Bartons, Crossing, Hopetoun and Red Ensign comprises sulphidic auriferous quartz veins contained within sericitic and chloritically altered sandstones, pelites, siltstones and shales of the turbiditic sequences of the MCB. Gold is variably associated with pyrite ± arsenopyrite and minor chalcopyrite, in veins that form en-echelon and ladder structures within shear and fault strike corridors, defining lodes of mineralisation. Mineralisation is considered syn-deformational to the main structural features of the MCB. The Genie deposit is also hosted partially within syn-deformational dolerite dykes which appear to have taken advantage of the same zones of deformation.
Dimensions
Bartons: Presents as a principal lode with a northeasterly strike, which turns further northwards at the eastern limits. This lode has a subvertical to steep southerly dip. A hanging wall lode, modelled as a splay structure from the Middle Creek shear associated main lode strikes northeasterly, converging with the main lode to the west. The splay lode has a subvertical to steep southerly dip. Strike length of the deposit is 925m, with an across dimension of 150m. Bartons is mineralised to the surface, but has been depleted by open pit mining. The main lode extends 295m below surface and is open at depth – limited by the extent of drilling.
Crossing: Presents as a series of sub vertical, parallel lodes with a northnortheasterly strike. Strike length of the deposit is 400m, is 120m across strike. Lodes are mineralised to surface, and currently extend up to 80m below the natural surface. Mineralisation is open at depth.
Hopetoun: Has a northeasterly strike and a length of 800m. The majority of the deposit has a shallow southeasterly dip (~30-40°), is approximately 100m across strike, and has an average depth below the natural surface of 75m. The northern quarter of Hopetoun has a more east-northeasterly strike, and is steeper in its southeasterly dip (~70°).
Genie: Presents as a series of stacked lodes with a general northwesterly strike and moderate south-westerly dip. Strike length of the lode stack is ~120m and the dimensions of the stack in a northeasterly direction is approximately 275m. Lodes extend up to 100m below the natural surface.
Red Ensign: extends for 300m along a northeasterly strike, with across strike dimensions of 60m, and a steep southeasterly dip. Mineralisation extends from surface to a depth of 80m, and is currently open down dip and along strike.
Beatons Creek Project
The Beatons Creek project consists of auriferous conglomerate reefs hosted by the Hamersley Basin of late Archaean-Paleoproterozoic age within the East Pilbara granite-greenstone terrain of the Early to Late Archaean Pilbara Craton on the northwestern part of Western Australia. The auriferous conglomerates of the Beatons Creek Gold Project are hosted by the Lower Fortescue Group sedimentary sequence. The auriferous conglomerates of the Beatons Creek Gold Project occur at different stratigraphic levels in the Fortescue Group within the Nullagine sub-basin, occurring in the mid-to-upper parts of the Hardey Formation.
Gold mineralisation occurs within the Beatons Creek conglomerate member of the Hardey Sandstone formation, which constitutes part of the Fortescue Group. Gold is present as fine (<100 µm) to coarse (> 100 µm) particles within the matrix of multiple, narrow, stacked, and unclassified ferruginous conglomeritic mineralised horizons, which are interbedded with unmineralised conglomerates, sandstones, and grits with minor intercalations of shale, mudstone, siltstone, and tuff. The lateral extent of the mineralisation has been identified as being up to 2.5 km.
Gold-bearing conglomerates have been identified at several stratigraphic levels, from surface to approximately 70 m in depth within the Fortescue Group in the Nullagine sub-basin. Auriferous conglomerates at Beatons Creek occur in the mid-to-upper part of the Hardey Formation.
Mineralisation relates to the energy level, either during deposition (channel) or reworking (marine lag).
Fluvial type channel conglomerates are typically clast-supported, heterolithic, pebble-to-cobble conglomerates with occasional boulders. Imbrication of clasts is commonly evident, indicating a general north-northwest flow direction in the project area. Trough cross-bedding and channels are commonly evident, suggesting a braided river environment. Individual channels are often ~50 m across and can be traced over hundreds of meters. The thickness varies between 0.5 m and several meters. Clasts are dominantly sandstone, conglomerate, siltstone, and shale locally derived from the nearby Mosquito Creek Formation (+70%), and clasts of several types of metamorphic rock and granite derived from the basement are less common (<10%), but still ubiquitous. White and grey vein clasts are also ubiquitous, making up around 10% to 20% of the clast population; sand and silt dominate the matrix and spotty clusters of detrital pyrite (up to 1 cm diameter), and fine (<1 mm) rounded and boxwork pyrite are common in matrix material, making up to 10% of the rock.
Marine lags (sometimes referred to as ‘armoured lags’) are typically tightly packed, clast-supported cobble-to-boulder conglomerate. Individual boulders can exceed 1 m diameter and are dominated by hard, resistant, siliceous dromedary clasts, vein quartz and chert. Sandstone and locally derived shale clasts are less common in marine lags and are commonly tucked between or under larger siliceous boulders. Imbrication is rare and individual beds are 0.3 m to 1.5 m thick and sheet-like, being continuous over hundreds of metres, with the main two marine lags (M1 and M2) continuous over 2.5 km. The matrix is comprised of sand and silt flakes of yellow shale, with ubiquitous and abundant detrital pyrite (up to 3 cm diameter) common in matrix material and making up to 20% of the rock.
Nature of the gold
Gold within the Beatons Creek conglomerates occurs as fine grains, larger flakes, and rounded particles up to 2 mm across, occasionally exceeding 5 mm. Coarse gold particles (>0.5 mm) are regularly visible, and fine gold can be panned from crushed matrix material with large pyrite concentrations.
Dimensions
Mineralisation at Beatons Creek strikes approximately east-northeast to west-southwest over 2.5 km by 2 km. The key domains are mineralised marine lags M1 and M2, which extend across all fault blocks except for Golden Crown and South Hill. The topography is undulating and so depth to the M1 and M2 is variable, depending on topographic highs and lows. The M1 in Grant’s Hill can be up to 65 m below surface and M2 up to 80 m at deepest within the optimised pit shell. In Edwards, the M1 is often less than 5 m below topography. Marine lags vary in thickness between 0.3 m.