Antipa and Rio gunning for high Calibre addition to Winu
Special Report: Antipa Minerals and Rio Tinto have approved another big exploration budget for their Citadel joint venture in Western Australia’s Paterson Province, where the Calibre gold-copper deposit continues to shape as a fine complement to Rio’s more hyped Winu discovery 45km away.
After Rio sole funded $12.6 million worth of exploration work at Citadel in 2020, bringing it within $1.4 million of meeting the expenditure milestone that will see its interest in the joint venture rise from 51% to 65%, the partners have agreed to spend another $13.8 million on exploration in 2021.
Antipa (ASX: AZY) said in an announcement on Monday that the 2021 Citadel programme would include 11,000-14,000m of reverse circulation (RC) and diamond drilling focused on the Magnum Dome area, which hosts Calibre and the Magnum and Corker deposits, and other priority areas within the 1,300km2 Citadel tenement holding.
The partners also anticipate updating the Calibre Mineral Resource, which currently stands at 47.7 million tonnes at 0.9 g/t Au and 0.15% copper for 1.3 million ounces of gold and 69,500 tonnes of copper, next year based on drilling conducted at the deposit since 2017.
Foreshadowing the resource upgrade, Antipa managing director Roger Mason said: “Since the maiden Calibre resource was delivered in 2017, drilling has produced significant intersections beyond the limits of that resource envelope.”
Results returned in recent months as part of the 2020 drilling programme have highlighted the quality and potential of the deposit. Among those was 319.8m at 0.96 g/t Au and 0.05% copper from 95m including 129.3m at 1.5 g/t gold and 0.05% copper from 159m and 78m at 2.05 g/t gold and 0.06% copper from 159m.
Although Calibre hasn’t garnered the same level of attention as Winu, Mason said the deposit had several advantages that explained Rio’s clear desire to see it progress closer to development.
“There’s a very significant high grade component to the Calibre system so it’s that factor plus a couple of other contributing positives that are of interest to Rio with respect to what they’re doing over at Winu,” he said.
“Depending on where you are in the system, Calibre can be 20-30% higher grade than Winu. It’s got shallower cover by about 20m in general, it’s only under 80m of cover. It also doesn’t have any significant oxide or supergene blanket at the top. It’s got a metallurgical recovery advantage over Winu, which has a fairly significant supergene blanket.”
In Monday’s announcement, Antipa flagged the possibility that a preliminary assessment of development options for Calibre will be undertaken next year. This exercise would presumably include examining the prospect of it being established as a satellite mine providing additional feed for a central processing plant at Winu.
Other work proposed as part of the 2021 Citadel exploration programme will focus on identifying additional priority target areas within the tenement holding that might deliver further discoveries.
“There’s still plenty of untested ground for greenfield discoveries all within about 50km of Winu and under shallow cover,” Mason said.
Rio announced a maiden inferred resource for Winu of 503 million tonnes at 0.35% copper, 0.27 g/t gold and 2.15 g/t silver in July. The resource included a higher grade component of 188 million tonnes at 0.55% copper, 0.36 g/t gold and 3.21 g/t silver.
The Citadel joint venture is one of three exploration partnerships Antipa has with major mining companies in the Paterson. Earlier this year it signed farm-in agreements over large tracts of land with Newcrest Mining and IGO Limited.
Antipa also retains 100% ownership of 144km2 of ground in the region, which includes an established resource of 11 million tonnes at 2.0 g/t gold and 0.24% copper for 723,340 ounces of gold and 26,390 tonnes of copper at the neighbouring Minyari and WACA deposits.
Drilling and other activities including the resumption of a gradient array induced polarisation (GAIP) survey are expected to start on the Citadel joint venture in March.