A series of “stunning” assays showcasing grades of up to 40% copper have confirmed a significant shallow discovery for Stavely Minerals (ASX: SVY) at the Thursday’s Gossan target within its namesake porphyry copper-gold project in Victoria.
The first diamond hole of a shallow drilling program which kicked off earlier this month intersected a 32m thick zone of high-grade mineralisation grading 5.88% copper, 1 gram per tonne gold and 58g/t silver, including 2m at 40% copper, 3g/t gold and 517g/t silver.
A step-out hole, collared 160m to the south-west, intersected an 85m-wide structural zone including an aggregate of 60m of massive to semi-massive sulphide including zones of strong copper-sulphide mineralisation.
Stavely said a “surprising interval” of high-grade nickel and cobalt mineralisation located below the copper-gold-silver interval has been interpreted to be a result of hot and acidic hydrothermal fluids having acquired the metals in similar circumstances to mineralisation at Tasmania’s Avebury nickel deposit.
Drilling at Thursday’s Gossan has been designed to delineate high-grade, near-surface copper-gold-silver mineralisation over a significant strike extent which would complement the target’s existing inferred mineral resource of 28 million tonnes at 0.4% copper (gold and silver not estimated).
The program is being carried out while Stavely completes a review of results and data from recent deep diamond drilling targeting the source porphyry.
Teamed with visual observations of drill core from a second step-out hole 80m south-west of the first which also encountered a thick zone of massive to semi-massive mineralisation, the “outstanding” results represent a “major exploration breakthrough” which is believed to have significantly improved the company’s understanding of the mineralisation setting at Thursday’s Gossan.
The results highlight similarities between the large mineral system at Thursday’s Gossan and that of copper deposits at the world-class Butte basin in Montana (once known as the richest hill on earth) and the historic Magma mine in Arizona.
Stavely executive chairman Chris Cairns said the company has been exploring for similar high-grade, lode-hosted copper-gold-silver mineralisation.
“The recognition that we should be using a Magma/Butte mineralisation model for our exploration drill targeting has been rewarded with spectacular success in the first diamond hole drilled to evaluate a shallow target at the Ultramafic Contact Fault,” he said.
“It is not often in the career of an explorer that you see 40% copper grades over sub-metre intervals, let alone over two metres – and those stunning copper numbers are accompanied by very significant gold and silver values as well.”
At midday, shares in Stavely were 175% higher at $0.66.