GreenTech Metals’ recent exploration target model for its Whundo massive sulphide base metals project points to a resource potential of between 15 million tonnes to 23 million tonnes, with copper grades ranging from 0.9 per cent and 1.4 per cent.
The model for the company’s project, near Karratha in Western Australia’s Pilbara region, also indicates a zinc resource potential for the same tonnage, with grades ranging from 0.2 per cent to 0.4 per cent zinc.
The target’s estimated contained metal ranges from 176,000 tonnes to 265,000t of copper and from 46,000t to 69,000t of zinc.
GreenTech’s current JORC-compliant mineral resource estimate for Whundo is an inferred and indicated 6.2 million tonnes at 1.12 per cent copper and 1.04 per cent zinc, containing 69,000t of copper and 64,000t of zinc.
GreenTech Metals executive director Tom Reddicliffe said: “We are very pleased with the potential of the Whundo project. Importantly, our work to date has highlighted both shallow and deep mineralised areas for further drill testing. The shallow mineralisation is of immediate interest as the company looks to identify and evaluate near-term production opportunities.”
The resource estimate applies to two of GreenTech’s six known mineralised zones, Whundo and Ayshia, which have both been exploited by small open pits.
In contrast to the limited mineral resource estimate, the conceptual exploration target modelling aims to develop a realistic expectation of the future potential of the entire string of deposits arrayed along the northeast-striking trend, including Whundo West, Whundo East, Austin, Shelby, Yannery and Ayshia.
Exploration target models are typically based on projections from known mineralised zones and related geology, including rock and structural trends and boundaries, geophysical surveys and their targets, and surface and downhole geochemical trends.
Accordingly, GreenTech used its entire relevant drilling database to inform the potential size and direction of the exploration target beyond the current Whundo mineral resource estimate. The database comprises 1135 holes for a total of 83,298.30 metres. Of these, 42 drill holes for 5916.8m sit within the exploration target area.
The exploration target modelling serves an important purpose, indicating and prioritising where drilling or other exploration and direct testing should be undertaken. However, the company will need to conduct further drilling of the mineralised zones to translate the picture into a resource estimate.
Apart from drilling, other direct testing could include trenching - usually only applicable to shallow near-surface mineralisation - or underground exploration by shafts, adits, winzes or drives, or through previous similar underground developments.
Having assessed its existing resources, GreenTech has determined that the shallow mineralisation is of immediate interest for launching near-term production from Whundo at one of two possible local processing facilities.
The company has engaged mining consultancy Burnt Shirt to evaluate its mining and processing options, identify a viable near-term mining venture and take it through to a scoping study.
The overall Whundo deposit area has a history of intermittent underground production from mining leases at Yannery between 1920 and 1958, amounting to 1132t of copper ore at an average grade of 21 per cent copper.
From 1951 to 1968, a further 1911.8t of ore, averaging 12.87 per cent copper, was reported from its oxidised and supergene zone.
Whim Creek Consolidated opened a pit in 1976 to produce 6200t of supergene copper ore at 29.68 per cent copper.
Fox Resources followed up with open-pit mining of the West Whundo deposit in 2006 and 2007 which yielded 148,310t of ore. It processed the ore at the company’s Radio Hill mill near Karratha to produce 25,812t of copper concentrate at a 20.86 per cent copper grade.
In 2017, Artemis Resources generated revenue through the sale of surface-mined ore, which was heap leached at its Whim Creek mill, 100 kilometres southwest of Port Hedland.
In its next stage of evaluation, GreenTech proposes to undertake a new drilling program focussed on significantly expanding its current Whundo/Ayshia mineral resource and, where possible, establishing new resources.
The company is already planning its next drilling campaign to test for mineralisation continuity between Austin and Shelby via a co-funded hole under the State Government’s Exploration Incentive Scheme.
It will also test the interpreted down-plunge projection of the Ayshia shoot and evaluate shallow, high-grade oxide mineralisation at Yannery.
The company is also launching a conceptual mining study which will see the completion of mineral resource estimates for Whundo, Ayshia and Yannery that will include gold. The metal is known to exist at the project but has not yet been included in previous resource estimates.
Management is fast-tracking its assessment of previously reported mineral resource estimates given their significant gold contribution, which it believes may enhance its in-ground value and improve the project’s economics.
When the resource estimates are completed for Whundo, Ayshia and Yannery, they will be put through the Whittle optimisation process to economically model the resource blocks and create one or more optimised pits around the economic wireframes.
GreenTech will then be able to assess the economics of near-term production opportunities, including further evaluation of the Radio Hill processing site.
In anticipation of near-term mining, GreenTech will also launch the requisite application process for a mining permit.
The Whundo massive sulphide deposit has sat in the sun for years waiting for the right suitor and the right commodity price regime to materialise simultaneously.
For the first time in the project’s history, GreenTech has shone a bright light on the greater potential lurking at depth beneath the scattered and often desultory workings in the Whundo field - rather like finding a sizeable iceberg beneath a seemingly insignificant ice floe – and it appears determined to make a good go of the venture.
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By Doug Bright
