Rio Tinto’s seemingly huge Winu copper, gold silver strike in the eastern Pilbara region of Western Australia is looking more interesting after the miner released more drill results to follow up on the first release of data in March.
Despite the new round of encouraging grades, Rio said says it is still too early to assess the potential size or quality of the mineralisation at Winu which remains open in three directions and depth.
Rio revealed that the new results include significant intercepts for 11 diamond drill holes not previously available in full for the March report, as well as changes to previously reported assays as part of ongoing quality control, assurance procedures and changes in analytical techniques.
The results cover drilling to the end of last year and a further update on drilling in 2019 is due in the third quarter.
“Results continue to indicate relatively wide intersections of vein-style copper mineralisation associated with gold and silver beneath relatively shallow cover which ranges from 50 to 100 metres,” the company said in Thursday’s statement.
“The mineralisation remains open at depth and to the east, north, and south.”
Rio said it had 180 people at the remote site along with eight diamond drill rigs, three RC rigs, and a waterborne rig.
“Other activity at Winu includes cultural heritage surveys and the commencement of construction of a gravel airstrip for emergency response purposes, given the exploration camp is located approximately 200km by gravel and sand track from the Great Northern Highway and a seven-hour drive from Port Hedland,” the company said.
Winu lies 130 kilometres m north of the veteran Telfer operation of Newcrest, had been the subject of speculation for more than a year, prompting a nearology-style rush for tenements in the area before the company revealed its first drilling results in March.
Assays show wide intersections of vein-style mineralisation with grades above one percent copper, 1g/t gold and up to 26.41g/t silver.
The results include figures for 11 diamond drill holes that were not previously available, in addition to previously reported results for exploration drilling to the end of 2018.
Highlights from the 11 drill results, which were not available at the time of the company’s last update in February, included: 456 metres at 0.43% copper, 0.6 grams of gold per tonne and 2.56 grams of silver per tonne; 245 metres at 0.47% copper, 0.6 grams of gold per tonne and 2.56 grams of silver per tonne; and 185 metres at 0.51% copper, 0.37 grams of gold per tonne and three grams of silver per tonne.
Some of the intersections are massive – 683 metres of 0.43% copper, 0.12 grams of gold to the tonne and 3.13% silver, 681 metres with 0.49% copper, 0.33 grans per tonne and 3.17 grams of silver,
Based on these limited results the Winu prospect looks more like a silver copper-gold deposit. The outlook for silver is nowhere near as positive as for copper.
The shallowness of many of the intercepts is positive because what Rio could end up with is a large, shallow in places, low-grade copper and gold mine with the richer overlay of silver.
With Telfer nearby (its a gold-copper open cut and underground operation) and the Nifty mine of Metals X close by (its an underground copper mine and like Telfer, run on a fly in fly out staffing basis) there is some water and infrastructure as well as a gas pipeline to Telfer.
Rio shares lost 2.6% to end the day at $96.94.