Mineralisation
- occurs in granitic and volcanic rocks of Archaean age;
- is contained in dilations within shears which are part of a larger regional shear zone
- the shears mined at Elverdton extend more than 1200m in a generally north-south direction, dip
steeply towards the east and continue below 400m depth;
- the shears are up to 18m wide and mineralised throughout with concentrations into high-grade
zones variously in the footwall (western) contact of the sheer; centre of the shear or the hanging
wall (eastern) contact of the shear and sometimes in all three positions;
- the high-grade zones are usually about 1m wide and average 6% copper, 2.4g/t gold and 7.2g/t silver.
Mineralisation in the Elverdton (and Desmond) Copper-Gold Mine contains magnetite and is associated with subtle but distinct ground and airborne magnetic anomalies. This magnetic anomalism defined zones of potential mineralisation enabling Resource Potentials Pty Ltd to prepare detailed magnetic images.
The mineralised lode mined until 1971 appears as a distinct linear magnetic anomaly and the old workings are clearly situated on the anomaly (Figure 2). Mining only extended about 200m south of the Elverdton shaft but it is apparent that the magnetic anomaly associated with the mined lode extends at least 600m further to the south. The linear magnetic anomalies near the mined lode are also likely to represent mineralisation. A horizontal diamond hole drilled towards the west from the Level 3 drive of the Elverdton workings in about 1915 encountered “... 4 feet of good (10%) ore...” (Reference2). This intersection strongly indicates that the magnetic anomalies west of the mine are associated with mineralisation.
These targets are mineralised shears and are essentially the remainder of the large hydrothermal system of which the historic workings of the Elverdton Copper-Gold Mine accessed only part. These shears have a combined potential to host about 9.4 Mt of copper-gold ore @ 2.2% Cu; 0.9g/t Au and 2.9g/t Ag (Allison,C, 2011) to a depth of only 400m with every indication that the mineralisation continues to greater depths.
Project Potential and Mineral Resource Estimate ( Allison,C, 2011)
The Elverdton Copper-Gold Project can be classified as an ‘Advanced Exploration Area’ mineral asset where a Mineral Resource has been estimated (although not formally reported on the ASX). Remaining exploration area would be classified an ‘Exploration Area’ mineral asset. The commodity item of interest for exploration is primarily structurally-controlled copper-gold mineralisation near-surface and at depth below historical underground development. A Mineral Resource has been defined as below in Table4 and Ravensgate considers the project is of merit and worthy of further assessment towards mine development. Ravensgate has not directly reviewed information relating to the generation of the resource estimates but is satisfied that on limited review the tabled tonnes and grade by resource category are reasonable for use for the purposes of this report. The reader should note that as this report is not intended for release to the ASX, a Competent Person and Consent-to-Reference statement has not be obtained or required (JORC, 2004 and ValMin, 2005).
Table 4 Elverdton Copper-Gold Project – Mineral Resource
Comment Category Tonnes (kT) Copper (Cu %) Gold (g/t Au) Silver (g/t Ag) Metal (Cu T) Metal (Au oz) Metal (Ag oz)
Tailings Dam Measured 714 0.15 0.45 0.57 1,070 10,300 13,100
Remnant (pillars & stopes) Indicated 385 1.0 0.5 1.5 3,850 6,200 18,600
Below mine Indicated 857 1.5 0.8 2.6 12,860 22,000 71,600
South of mine Inferred 828 2.2 0.9 2.9 18,220 24,000 77,200
TOTAL All 2,784 1.3 0.7 2.0 36,000 62,500 180,500
Note:- All resources are contained within Tenement M74/246, east side of Ravensthorpe road. Minor rounding errors may occur. The Inferred portion includes supergene grade enrichment.
(Allison, C, 2011)
Paxton has also defined an exploration target immediately west of the Elverdton workings and east of the Ravensthorpe-Hopetoun Road (Table The exploration target is well supported from the following geological and exploration information as listed below. A good correlation has been compiled by Paxton between geophysical and geochemical information. The target has been derived from weighted grade average methods and includes near-surface supergene grade enrichment (as seen at Elverdton and now mostly mined out as reflected within the Mineral Resource grade estimate).
- Nearby geological and production information from the Elverdton underground workings to the east;
- Surface geochemical surveys;
- Recent aeromagnetic geophysical surveys;
- Historical IP geophysical surveys (1965); and
- The historical drill intersection which recorded 1.2m at 10% Cu
Table 5 Elverdton Copper-Gold Project – Exploration Target
Comment Category Tonnes (kT) Copper (Cu %) Gold (g/t Au) Silver (g/t Ag) Metal (Cu kT) Metal (Au oz) Metal (Ag oz)
Elverdton West Target 9,384 2.2 0.9 2.90 206.5 272,500 878,900
To a depth of 400m, this translates to a possible 206,500t of Cu; 272,500oz of Au and 878,900oz of Ag.