Stavely Minerals (ASX: SVY) has achieved a significant breakthrough in its ongoing search for a world-class porphyry copper-gold deposit at its 100%-owned Stavely Project in western Victoria (Figures 1, 2 and 3) after receiving the results of a recent 20-hole RC drilling programme at the Thursday’s Gossan copper deposit.
- Outstanding initial results received from recently completed shallow reverse circulation (RC) drilling at the Thursday’s Gossan copper deposit, part of the 100%- owned Stavely Project in western Victoria.
- Strong porphyry-style copper-gold mineralisation intersected, with several RC holes ending in mineralisation. Intercepts include:
- 24 metres at 0.64% copper and 1.2 g/t gold
- 29 metres at 0.53% copper and 0.30 g/t gold to end-of-hole (EoH); including o 4 metres at 1.39% copper and 0.5 g/t gold
- 25 metres at 0.52% copper and 0.37 g/t gold to EoH
- 3 metres at 4.14% copper and 0.36 g/t gold
- Copper-gold mineralisation intercepted over 400 metres strike extent and could easily extend beyond 1 kilometre.
- The strength and tenor of the mineralisation intersected, plus the higher gold grades, make these the most important results generated from the Stavely Project to date.
- The mineralisation is interpreted to be hosted within upper-level phyllic (sericitepyrite) to argillic (kaolinite) alteration, meaning that even better developed mineralisation should be located at depth within the potassic (potassium feldsparbiotite-magnetite) alteration.
- Selected RC drill holes have been extended with diamond drill hole ‘tails’ and assays are pending for these intersections, which are visually very encouraging.
- Follow-up deeper drilling is being planned as a priority to target the high-grade core of the Thursday’s Gossan porphyry system.
The shallow drilling, which was designed to follow-up a new interpretation of the controls on high-grade copper-gold mineralisation in the near-surface chalcocite-enriched copper ‘blanket’ at Thursday’s Gossan, has intersected thick zones of strong porphyry-style copper-gold mineralisation, representing a potentially highly significant development. This new interpretation was developed from observations in drill core co-funded by the Victorian Government’s Target Exploration Initiative.
As outlined in the company’s ASX announcement of 9 March, Stavely Minerals recently drilled four sections of five holes each for a total of 20 RC drill holes to confirm an interpretation that high-grade copper-gold mineralisation near surface at Thursday’s Gossan is hosted by sulphide-rich veins in structures ‘leaking’ from a porphyry intrusion at depth (Figures 4 and 5).
Selected results from this highly successful drilling campaign include:
- 24 metres at 0.64% copper and 1.2 g/t gold including
- 14 metres at 0.82% copper and 1.99 g/t gold including
- 1 metre at 0.84% copper and 22.2 g/t gold
- 29 metres at 0.53% copper and 0.30 g/t gold to end of hole (EoH), including
- 4 metres at 1.39% copper, 0.5 g/t gold and 55 g/t silver
- 25 metres at 0.52% copper and 0.37 g/t gold to EoH
- 3 metres at 4.14% copper, 0.36 g/t gold and 59 g/t silver
- 43 metres at 0.55% copper and 0.11 g/t gold
- 28 metres at 0.59% copper and 0.19 g/t gold
- 8 metres at 0.74% copper and 0.17 g/t gold
- 25 metres at 0.30% copper and 0.29 g/t gold to EoH including
- 3 metres at 1.24% copper and 1.31 g/t gold
These shallow copper-gold (and silver) intercepts are very significant for the potential development of the near-surface chalcocite enriched ‘blanket’ at Thursday’s Gossan, demonstrating that significant gold and silver values exist within this zone.
All previous Mineral Resource estimates for the Thursday’s Gossan chalcocite blanket (28Mt at 0.4% copper in Inferred Resources, see Stavely Minerals’ Annual Report 2016) to date have only estimated the copper within the deposit, excluding gold and silver. This was mainly because previous explorers had not assayed for gold or silver in many drill holes within this zone. These results conclusively demonstrate that significant gold and silver grades are hosted within the Mineral Resource area.
A feature of these drill intercepts is that the mineralisation is not just limited to late porphyry sulphide-rich ‘D’ veins, but is in fact fairly consistently distributed throughout the intervals with higher-grade zones correlated with the more sulphide-rich ‘D’ veins. This is a common feature of many porphyry copper-gold deposits.
The mineralisation is associated with sericite-pyrite ‘phyllic’ alteration which, in classical porphyry zonation models could be expected to be located above and lateral to even stronger copper-gold mineralisation in the centrally located potassic alteration zone.
Stavely Minerals’ exploration team has developed a conceptual model that there were two phases of mineralisation at Thursday’s Gossan. The early porphyry phase is a low-grade copper-only phase that previous explorers had identified and is of little economic interest.
Stavely Minerals’ original interest in the project was based on the recognition, in previous explorers’ drill core, of evidence of intense high-level alteration associated with strong copper-gold mineralisation. The company’s belief was that these attributes were indications that a second-phase copper-gold porphyry existed at depth that had not yet been seen in the historical drilling.
The company’s exploration team has identified distinct similarities in alteration styles and copper-gold drill results to those which were the precursor to the world-class Cadia Ridgeway copper-gold porphyry discovery in NSW (owned by Newcrest Mining Limited).
For comparative purposes, it is instructive to note that the current Ore Reserves at the current underground operation at Cadia Ridgeway are 80 million tonnes at 0.28% copper and 0.54 g/t gold1 . While the grades are comparable, Stavely Minerals’ recent results are from as shallow as 22m drill depth and are interpreted to occur in the upper levels of a potentially higher-grade system at depth.
It must be noted that the target at Thursday’s Gossan is conceptual in nature and it is uncertain that further exploration will result a discovery or the estimation of a mineral resource.
A number of the current programme RC drill holes were not completed to their planned depths and, consequently, incomplete RC holes were re-entered by a diamond drill rig providing diamond core ‘tails’ to the original planned depths.
Of the 20 RC drill holes, two were completed planned depth, six were extended to depth with diamond tails and one was re-drilled from surface with diamond core. A number of re-entries are planned to complete diamond tails on more of the incomplete RC drill holes.
RC drill intercept table at Thursday’s Gossan
Stavely Minerals’ Managing Director, Mr Chris Cairns, said the recent RC drilling campaign potentially represented a key turning point in the company’s ongoing campaign to find a world-class porphyry deposit:
“The results are impressive in terms of the width and tenor of the mineralisation, combined with the fact that many holes ended in mineralisation. Importantly, this is the most convincing endorsement we have seen to date of our conceptual model that a second-phase porphyry intrusion is driving the copper-gold mineralisation at Thursday’s Gossan.
Given that these results are from a style of host-rock hydrothermal alteration typically located above and lateral to even stronger copper-gold mineralisation, I am confident that the best results are potentially yet to come with deeper drilling at Thursday’s Gossan.
We are very excited about the emerging discovery opportunity in front of us and we are looking forward to receiving the balance of the assay results and potentially getting a track-mounted rig back into the field as quickly as possible to drill some deeper holes targeting the high-grade centre of the porphyry system.
In response to feedback from some shareholders and brokers, we have split this announcement into two sections. The first section above presents the results and what they mean in simple terms, the second below goes into greater technical detail describing the nature of the mineralisation, alteration and other technical details and a discussion of the implications of these results.
Stavely Minerals’ style of exploration is to apply the sophistication of the best science available in combination with the brute force of drilling often and not being afraid to drill deep. The reason why it is important to provide such depth of technical detail in our reports is that, to take your company to the next level and realise the value we believe rests in your company’s assets, we will need technically sophisticated investors (or corporates) and institutions to pick-up the baton for funding / on-market share buying. The prize is potentially very large and of immense value but the search can also be very expensive when 1,000 metre drill holes are contemplated.”