BlackEarth Minerals NL (‘BlackEarth’) currently has four graphite projects within Western Australia: Donnelly River, Greenhills, Northern Gully and Yalbra.
This project comprises three exploration licences – E70/4824, 4825 and 4972 – in the far southwest of Western Australia, immediately to the north and northwest of the regional town of Manjimup. The South West Highway, a major transport corridor, passes through E70/4825, with internal access provided by secondary roads and forestry tracks.
The graphite at Donnelly River occurs in several graphitic horizons up to 11 metres (‘m’) wide. At the surface, graphite is found within a clayey ferruginous duricrust overlying a clayey graphitic chlorite schist. The graphite mineralisation has formed as a result of high-grade regional metamorphic processes acting on carbonaceous shale, limestone and sandstone. Containing from 2 to 60 per cent total carbon (‘TC’), these have been altered by pressure and high temperature to form graphitic phyllites, schists, marbles and quartzites. The process commonly results in the formation of beds, veins and lenses containing graphite that ranges from low-grade amorphous material to high-grade, large-flake deposits.
Graphite was noted at Donnelly River as early as 1888. In 1902, trial ore parcels were sent to London but met with limited acceptance there. However, efforts to develop the deposits into a commercial enterprise continued from 1904 to 1916.
In 1905, a mining operation was established at Donnelly River Southeast, with at least four shafts sunk on the leases. Although records are limited, they indicate that graphite was shipped from there via Fremantle and that mining continued until 1916. Historical newspaper reports from 1910 state that the operator arranged to ship 20 tonnes (‘t’) of graphite to England, while onsite stockpiles included 90 t of first-grade and 200 t of second-grade ore. At the time, unfortunately, applications for the Donnelly River graphite were limited.
In 1943, operations at Donnelly River recommenced, probably due to wartime demand, and a further 18 t of graphite were produced. Much later, in 1984, mapping of the area identified an adit and several shafts up to 15 m deep, with an associated washing plant.
Previous exploration activity in the area targeted base metals, gold and tin-tantalum but not graphite as such. Given the extent of favourable host lithologies there, it seems there is potential to discover new deposits of commercial-grade graphite. BlackEarth aims to discover repetitions of the known graphite occurrences at Donnelly River.
BlackEarth’s Greenhills project consists of four exploration licences – E70/4811, 4812, 4903, and 4906 – located 20 km east of the township of York in Western Australia. The sealed Quairading-York, Doodenanning and Cubbine Roads cross the project area, and numerous gravel roads and tracks traverse the tenements themselves.
The graphite in the area, often described as ‘flaky’, has been defined in weakly- to well-foliated kaolinite rocks interpreted as originally gneiss, as well as metasedimentary rocks in contact with the gneiss, and intruding leucogranite with adamellite stocks.
Three graphite occurrences have been recorded within the project area – at Balkuling, Doodenanning and Greenhills.
Previously, a single sample from Balkuling was shown to contain 5 per cent graphite flakes less than 0.2 millimetres (‘mm’) in diameter and with 10 per cent total graphite carbon (‘TGC’). The host was completely kaolinised, foliated metasedimentary rock.
Another two samples, containing flake graphite of various sizes taken from the Doodenanning occurrence, returned assays of 5.6 per cent and 18.7 per cent TGC.
The graphite zone at Greenhills, meanwhile, was interpreted as being a 20 km, east-northeast trending zone from Greenhills railway siding towards Doodenanning. The host rock, containing fine- to medium-grained flake graphite with accessory mica and limonite, was deemed to be completely kaolinised, foliated and metasedimentary. The graphite itself returned an 8.7 per cent TGC assay from 10 per cent flake graphite exceeding 0.6 mm in diameter.
Historically, exploration in the area targeted mostly kaolin, base metals and gold, with lesser attention paid to iron mineralisation and no primary targeting of graphite. Past explorers did identify a black, flaky mineral in both air-core and rock chips in a kaolinised, banded gneiss. The samples were taken during kaolin exploration near the Balkuling graphite occurrence. A massive silvery-grey mineral noted in both rock chips and air-core chips from gossanous schistose gneissic rocks near the Doodenanning graphite occurrence could be another graphite occurrence.
In view of the extent of favourable host lithologies, as well as the known graphite occurrences in the area, BlackEarth believes a dedicated exploration programme aimed at discovering an economic graphite deposit within the tenements is warranted.
Consisting of a single exploration licence – 66/95 – located 26 km east-southeast of the township of Geraldton, this project covers an area of around 48 km2. The Geraldton-Mt Magnet road passes 5 km south of the tenement area, so the distance by road from the site to the port at Geraldton is 35 km. A number of gravel roads and tracks traverse the tenement itself.
At Northern Gully, flake graphite is contained within iron-rich rock consisting of limonite and mica that is proximal to shear zones related to movements along the fault and numerous tension and cross-cutting faults, as well as drag/dilation zones. Graphite associated with tension-related quartz and pegmatite veins at and adjacent to the historic Lady Sampson mine also occurs.
Historically, two graphitic samples from the Lady Sampson pegmatite returned assay grades of 16.5 per cent and 19.4 per cent TGC. The greatest concentration of graphite was exposed at the Northern Gully mine, within graphite-silica matts infilling strain zones in pegmatites, gneiss and migmatites.
Past exploration targeted mainly base metals and gold, with lesser attention paid to iron mineralisation and kaolin; there was no primary targeting of graphite. In view of the extent of favourable host lithologies and known graphite occurrences in the area, BlackEarth believes exploration aimed at discovering an economic graphite deposit is warranted.
The Yalbra project comprises a single exploration licence, E09/2234 (to be granted), located 280 km east of the township of Carnarvon. It covers an area of around 247 km2. The gravel Carnarvon-Mullewa Road, which passes through the northwest corner of the tenement, provides access to the port at Carnarvon, while access within the tenement area is limited to the Glenburgh Station tracks.
Graphite occurrences of amorphous to coarse-flake graphite in a graphitic gneiss are located within 10 km of the licence area, at Coordewandy and Yalbra. The former lies 950 m south of E09/2234, while the latter is 6.3 km to the east of it.
Urangesellschaft Australia Pty Ltd discovered the graphite occurrence at Coordewandy in the late 1970s. There, the graphite is mainly amorphous; it produced a peak assay of 19.85 per cent TC. The occurrence is proximal to the faulted contact between the partly retrograde quartz-sericite-muscovite-chlorite (magnetite-tourmaline-biotite) schist of the Camel Hill Metamorphics (originally termed ‘the Morrissey Metamorphic Suite’) and the meta-granites of the Bertibubba Supersuite.
When Carpentaria Exploration Company Pty Ltd first investigated the Yalbra graphite occurrence in the early 1970s, it was found to consist of six graphite prospects over a strike length of 4 km, with the graphite contained as multiple bands in schist that strikes generally east-west with sub-vertical dips. It. Most recently, Buxton Resources Ltd has defined an Inferred JORC (2012) Code Mineral Resource of 4 million tonnes (‘Mt’) at 16.2 per cent TGC over a strike length of 600 m. Moreover, a heli-borne VTEM™ survey has defined strong graphite conductors over a strike length exceeding 6 km. Most of the mineralisation remains open at depth and along strike. It ranges from amorphous to medium-coarse flakes greater than 1 mm in length. Typically, graphite greater than 150 microns long is considered coarse-flake.
Given the extent of favourable host lithologies and known graphite occurrences in the area, BlackEarth believes a dedicated exploration programme aimed at discovering an economic graphite deposit within the tenement is warranted.