The Stavely Project is located in western Victoria on the Stavely tablelands approximately 250 km to the west of Melbourne. The project comprises exploration licence 4556, over which a retention licence (RL2017) has been applied for.
The Stavely Project is located within the Mount Stavely Volcanic Complex which is considered a northern extension of the Mt Read Volcanic in Tasmania, which is host to-
- Mount Lyell (1.8 Mt Copper /2 M oz Gold)
- Rosebery (1.1 Mt Lead / 820 kt Zinc/ 115 kt Copper/ 110 M oz silver / 2 M oz Gold)
- Henty (1.2 M oz Gold)
The Mount Stavely Volcanic Complex (MSVC) is classified into the Grampians-Stavely Zone in Western Victoria. The Moyston Fault separates the Delamerian Fold Belt, in which the Stavely Project is located, to the west from the Lachlan Fold Belt to the east. West of the Moyston Fault are fault-bounded belts of submarine calc-alkaline volcanics (Mount Stavely Volcanics) within a sequence of quartz-rich turbidites (Glenthompson Sandstone) deforming during the Late Cambrian to form the basement of the Grampians-Stavely Zone. The Dalamerian Fold Belt rocks are unconformably overlain by an Ordovician-Silurian shallow marine to fluvial sequence of the Grampians Group. The Mount Stavely Volcanics consists of a suite of andesitic lavas at the base of the pile, conformably overlain by felsic volcanics/tuffs, shales and sandstones, with plugs of tonalite and rare slices of ultramafic rocks of the Dimboola Igneous Complex. The Mount Stavely Volcanics are either interbedded with, or faulted against, the arenites of the Glenthompson Sandstone.
The Company is targeting a Cadia-type gold-copper porphyry at the Stavely Project.
At the Thursday’s Gossan Prospect, a near surface secondary chalcocite enriched blanket has an estimated (using a 0.2% Cu grade lower cut-off) –28Mt at 0.4% copper for 110kt of contained copper.
The Company’s conceptual study on the potential for copper concentrate production from the chalcocite-enriched supergene ‘blanket’ at the Thursday’s Gossan copper deposit demonstrated sufficient positive outcomes with respect to net revenue and Net Present Value, as well as an attractive Internal Rate of Return, to proceed to a scoping study.
There are as not yet reasonable grounds to support the discussion of these projected economic outcomes in detail.
The key elements of the conceptual study include:
- An average feed grade of 0.5% copper;
- A sulphide flotation recovery of 87% (based on metallurgical testwork); and
- A sulphide concentrate grade of 27% copper (based on metallurgical testwork) producing a very ‘clean’ concentrate with low deleterious elements.
Financial assumptions included:
- World Bank forecast copper prices;
- A range of A$/ US$ exchange rates of A$1 = US$0.60 to US$0.75
The conceptual study identified a number of opportunities to enhance project economics including:
- Increasing the size of the resource –recent drilling has identified chalcocite copper mineralisation outside the current Mineral Resource. Stavely Minerals’ drill hole SMD004 intersected 52m at 0.23% copper from 39m downhole depth. This intercept is located approximately 400m to the west of the existing Mineral Resource and illustrates the potential for material increases;
- Reducing the assumed mining and milling costs by investigating the suitability of using continuous surface mining equipment. The attraction of the mining method is that it is well suited to long and wide, flat-lying, mineralisation; the oxidised nature of the mineralisation is well suited to this mining method; the product is already partially comminuted and reduces the need for primary crushing; and this mining method can be very selective in the vertical dimension.
- Reducing the processing costs through lowering reagent usage and by streamlining the processing flowsheet – the Scoping Study will investigate the potential to beneficiate the mineralised from un-mineralised clays prior to flotation of the sulphide concentrate amongst other processing enhancements.
Thursday’s Gossan Porphyry Copper Prospect
The first phase of deep diamond drilling by Stavely Minerals in 2014, into the Thursday’s Gossan porphyry target, returned broad zones of low-grade copper mineralisation, including 196m at 0.13% copper, 52m at 0.23% copper, 82.3m at 0.12% copper and 62m @ 0.17% copper.
More recently, additional IP data was collected at the northern end of the prospect in order to better resolve targets beneath the low-angle structural offset, identified in drilling by Stavely Minerals in 2014. The areas to the north and east of previous drilling by Stavely Minerals are considered to have the greatest potential for discovery of copper-gold mineralisation associated with resurgent porphyry intrusion.
Deep drilling conducted by Stavely Minerals and previous explorers has provided a geological vector to the metal-rich potassic ‘core’ of the porphyry system. Three diamond drill holes have been planned at the Thursday’s Gossan Porphyry prospect to target the ‘core’ where the best developed copper and gold grades could be expected and have yet to be discovered. Geophysical information gained from the IP surveys and geological and geochemical evidence obtained from the diamond core including structural investigation, 3D modelling, spatial analysis of alteration and mineralogy, as well as sulphur isotopes has been used to design the drilling programme.
The Company has two diamond drill holes planned, the first of which has been designed to target a weak and shallow IP chargeability feature, in an area to the north of the previous northernmost historical diamond hole and in the vicinity of an historical aircore hole STAVRA007, which returned 21m @ 0.2 g/t Au and 0.4 % Cu. These northern drill holes have returned the best gold grades in the prospect to-date and the historical auger sampling returned strongly anomalous copper results in this area.
The data acquired from this drill hole, in what will become the northern-most drill hole in the project where the next northern most hole VSTD001 has the strongest magmatic sulphur isotope signature (-6.4‰ d34S) and the best copper gold intercept to date (32m at 0.41 g/t Au and 0.73% Cu from 22m), will be of extreme 3D spatial importance.
The second diamond drill hole has been designed to target an undrilled IP chargeability feature in an area between two historical diamond drill holes that have returned the best copper and gold results in the prospect to date. Drill hole VSTD001 returned 32m at 0.8% Cu and 0.4 g/t Au from 22m and SNDD001 returned 7.7m @ 4.1% Cu and 1.1 g/t Au from 94.7m and 9.5m at 2.9% and 0.4 g/t Au from 154.6m.
The diamond drill holes are 300m apart, leaving a gap of sufficient size for a porphyry intrusion of similar dimensions to those at North Parkes. The historical auger soil results in this area are strongly anomalous in copper.
A review by Corbett and Menzies Consulting in November 2014 identified a Priority A target in the central portion of the Thursday’s Gossan prospect in the vicinity of historical Newcrest diamond drill hole VSTD002A, which reported highly anomalous Cu-Mo values below a flatly dipping normal fault. Drill hole VSTD002A returned 78m at 0.22% Cu and 20 ppm Mo from 125m. Corbett and Menzies recommended that drilling be conducted to the west of, and beneath VSTD002A.
Mount Stavely Porphyry Copper-Gold Prospect
The Mount Stavely porphyry copper-gold target is reflected as a ‘low’ in the gravity data and as a ‘low’ in the airborne magnetic data which is interpreted to reflect respectively as a porphyry intrusive at depth and magnetic destructive hydrothermal fluid alteration. Proximal gold mineralisation at the Fairview gold prospect is interpreted to be mesothermal to epithermal style gold mineralisation. An IP survey, conducted in 2014 in the Mount Stavely area returned a chargeability feature which is slightly offset to the north-east from the gravity low.
Soil samples were collected at the Mount Stavely prospect for primary analysis using a Niton™ portable XRF analysis with gold analysis through Australian Laboratory Services. The Niton™ results show an arsenic anomaly in the immediate vicinity of the topographic high at Mount Stavely possibly indicating a higher-level within the system. The Niton™ results show an elevated molybdenum response which is coincident with an IP chargeability anomaly. A coincident anomalous gold value of 49 ppb was also returned this in area. As the chargeability feature with Mo-Au geochemical support overlies the Williamson Road Serpentinite (not expected to have a high Mo-Au background signature), they are interpreted to be associated with a buried porphyry. Two diamond drill holes have been planned at the Toora West prospect to target intrusion related copper and gold mineralisation. An IP survey has been planned prior to the diamond drilling programme. The survey will close-up the line spacing, which will significantly improve the constraints along strike and also permit 3D inversion modelling and improved drill targeting.
Diamond drilling at Toora West will provide valuable geological information in a highly prospective belt, which has essentially been unexplored. Work to date on the Toora West prospect has identified that it is a stand out target for porphyry-style or diatreme-hosted copper-gold / gold mineralisation.
Fairview Gold Prospect
The 4.8 kilometre long Fairview North and Fairview South mesothermal to epithermal gold anomalies, originally identified in soil sampling and followed-up with shallow reconnaissance aircore, RC and limited diamond drilling, has not been investigated by any geophysical techniques. The drilling to date has returned numerous anomalous gold intercepts, including:
- 5 metres at 17.44 g/t gold from 28 metres drill depth to end of hole,
- 2 metres at 16.06 g/t gold from 23 metres drill depth,
- 4 metres at 6.69 g/t gold from 10 metres drill depth,
- 17 metres at 1.70 g/t gold including 5 metres at 3.1 g/t gold from 12 metres drill depth,
- 12 metres at 2.16 g/t gold from 18 metres drill depth to end of hole including 3 metres at 5.1 g/t gold from 27 metres drill depth to end of hole.
The Fairview gold anomaly is associated with sericite albite and K-spar (adularia) alteration and quartz sulphide veins with chalcopyrite, sphalerite, galena and gold. The sphalerite is of a pale yellow colour and in conjunction with the adularia suggest a low-temperature possibly low-sulphidation epithermal affinity.
Previous drilling has failed to provide a focus for further drilling which could potentially lead to the discovery of a Lake Cowal-style gold deposit. An IP programme is planned that will provide valuable data on which to target future drill programmes. The chargeability response will potentially provide information regarding the location of disseminated sulphides and the resistivity response may be related to silica alteration and veining.