First discovered in 1856 and last drilled more than 20 years ago, the Granite Flat goldfield still hosts high-grade mineralisation as Victorian explorer Dart Mining (ASX: DTM) has since found – with drilling producing significant gold-copper-silver intercepts.
Maiden rotary air blast (RAB) drilling on the northeast Victorian historic field has produced “encouraging” intersections including one hole returning 19m at 9.39 grams per tonne gold, 0.61% copper and 19.2 parts per million silver.
Mineralisation began 28m down hole and included a 3m intercept grading 41.1g/t gold, 1.52% copper and 41.1ppm silver.
Dart chairman James Chirnside said this maiden drilling program is the first time in 20 years that holes have been sunk at Granite Flat.
“We have achieved some spectacular results that largely surpass the tenor of historic results,” he added.
“Furthermore, and perhaps more importantly, we have enhanced the wider potential of the prospect with numerous long, lower grade copper and gold intersections over an extensive area that indicate a large, fertile intrusive system.”
Mr Chirnside says this system is potentially the source of the widespread mineralised footprint at Granite Flat.
Discovery coincides with high copper, silver, gold prices
“At a time when prices for copper, silver and gold are surging, the results have elevated Granite Flat to be a potentially company-transformative asset for Dart,” Mr Chirnside said.
In all holes now reported from the maiden RAB program, gold and copper mineralisation remains open and untested along strike and at depth.
Granite Flat is part of a large land position the company holds in northeast Victoria.
Dart is exploring nine goldfields there, where multiple historic mines operated, along with two lithium-tin-tantalum prospects, and six porphyry gold-copper-molybdenum projects.
Other gold hits from Granite Flat included 4m at 3.23g/t (including 1m at 7.84g/t), 9m at 2.1g/t, 20m at 0.96g/t, 10m at 0.85 g/t and 25m at 0.81g/t (including 1m at 4.89g/t).
Of the copper intercepts, in one hole mineralisation extended from surface through the entire 50m drilled, averaging 0.12% (and including 14m at 0.24%).
Current drilling follows new interpretation of data
According to Dart, previous explorers at Granite Flat during the 1980s and 1990s had identified broad copper-gold mineralisation over a large area.
Current exploration is based on new interpretations of this historic data and has now identified numerous high-grade zones of gold-copper-silver mineralisation, the company said.
The first Granite Flat reef claims were pegged in 1856, with most lodged between 1877–1878.
Among explorers active before 2000 was CRA Exploration — an arm of what is now Rio Tinto (ASX: RIO) — which completed extensive exploration in the search for a bulk mineable resource.
This included sampling of 18 costeans, 32 reverse circulation and 13 diamond drill holes, along with aeromagnetic, ground magnetic and induced polarity surveys of the site.
Dart has been seeking porphyry-style deposits
In 1994, the former Perseverance Mining entered into a joint-venture agreement with CRA Exploration, working the Granite Flat prospect from 1996 to 1999, completing an additional 20 drill holes.
Minor stream sediment and soil sampling was completed between 2006-2016 by the former listed Synergy Metals.
Dart, in an earlier update on its exploration, noted that its key founding strategy in 2007 was to seek opportunities for porphyry-style mineralisation in the region.
The region is thought to be underlain by the Macquarie Arc which also hosts the New South Wales mining centres of Cadia and Ridgeway, where Newcrest Mining (ASX: NCM) has its large operations.