Rumble managing director Shane Sikora told MNN the project had come to dominate the company's focus, and while it may have looked like an overnight success last year it was the culmination of a five-year plan to develop a sustainable exploration company.
Founded a decade ago, Rumble had been scrabbling about in Western Australia's Fraser Range and Eastern Goldfields before it recruited technical director Brett Keillor and decided to switch its strategy.
Sikora told MNN if you want to find and develop a deposit, you want the kind of people who have done it before, which the eminently qualified Keillor has, having twice been AMEC's Prospector of the Year, for the Marymia gold discovery in 1998 and IGO's Tropicana discovery in 2012.
He's played a role in the discovery and development of seven globally significant orebodies, most recently the Karlawinda gold deposit.
"He has been critical in our success. We've been able to harness the technical nous of someone who's an expert in everything from early stage exploration to discovery," Sikora said.
Keillor generated a range of targets, and Rumble got out the chequebook, securing a string of low-cost options that gave it the rights to undertake first pass work.
"It was our drill-to-kill strategy, to inform if we should pass or move on. We had seven projects and have killed four," Sikora said.
In 2017 it optioned the Chinook-Magazine project in the Earaheedy Basin from Zenith Minerals, which still retains a 25% interest.
The discovery hole in April 2021 delivered 34m at 4.22% zinc-lead from 66m, including 17m grading 6.65% from 73m.
The Tonka discovery followed last December.
Chinook was given a 40 million tonne exploration target, but given Tonka alone has twice the strike, it has now been boosted to between 100-120Mt grading 3.5%-to-4.5%.
It had found evidence of copper
and has described five styles of mineralisation now defined across multiple deposits.
"We're working on a maiden resource in the back end of next year, but we can see this is only going to get bigger, because we still haven't found the edges," Sikora said.
The Earaheedy Basin was always known to be prospective but hadn't seen a lot of attention.
Renison Goldfields had completed some drilling in the early 2000s, finding zinc, but the area was remote and challenging, and the zinc price was much lower, so the area languished.
There's also a hard iron sequence in the area, and a lot of the prior drilling stopped in that zone, or just below it, as rigs lacked the power to punch through it.
"We also had the same issues, so we used mud doctors and specialists to work better drilling method. It took us about 2-3 months to master with high-powered drilling," Sikora said.
The persistence paid off.
Similar settings have delivered large base metal discoveries around the world
, and Rumble is betting its resource will be world-class, and support a development of a large, shallow, and flat-lying orebody that unlike most zinc-lead deposits globally can be developed an economic open pit, not a more costly underground.
"This is a zinc-dominant sulphide deposit already, and now we're regularly getting 5% plus zinc in the feeder zones, so we think there's potential for this to become a supergiant deposit, and one of the world's best mines," Sikora said.
"We think this is still the tip of the iceberg. We've achieved exceptional results from our technical team, and the next 6-12 months will be even more exciting."
Its next target will be Sweetwater, a 15km trend that has just two holes into it.
"There's no reason the mineralisation won't extend from Chinook," he said.
"We're still at the beginning of this journey."
The company has tested just 15% of the prospective 90km of strike, and had focused on just one of three targets, the Navajoh Dolomite.
The deeper Purple Shale (which can be up to 70m thick) and Iroquois formation
(which can be up to 280m thick) are still to be tested, but there is every expectation they will add tonnes given drilling by others in the area.
With zinc now dubbed a critical metal, and shortages of 7Mtpa expected from the middle of the decade, any development would be well timed.
*Rumble Resources is a nominee for Explorer of the Year in the 2022 MNN Awards.