Middle Island Resources’ review of data from its fully owned Ridgelands project in Queensland has produced a walk-up target area where 1980s exploration revealed enticing rock sample assays to 14.6 grams per tonne (g/t) gold.
The old data also reveals soil-gold anomalism above 0.05 parts per million to a peak of 5.66g/t gold, while shallow reverse circulation drilling attained a best intercept of 10m at 1.15g/t gold.
The Ridgelands project lies within the geological framework of the New England Fold Belt in eastern coastal Queensland and presents a potential district-scale opportunity in a globally recognised gold-copper region. The project is centred about 35km north-northwest of the Queensland city of Rockhampton and about 48km north of the historic world-class Mt Morgan gold mine.
The Mt Morgan mine has proven to be one of the largest porphyry copper systems in Eastern Australia. It operated between 1882 and 1981, mining 50 million tonnes at 4.75g/t gold and 0.72 per cent copper to yield 7.7million ounces of gold and 361,000 tonnes of copper.
The company has identified a small number of shallow historic reverse circulation drill holes in the old Ridgelands goldfield. The holes were put in to follow up soil-gold anomalism coinciding with a magnetic high on the flanks of the Ridgelands Granodiorite, which could turn out to be the source of gold mineralisation throughout the area.
Six of the holes terminate in old mine voids and four holes end in low-grade gold. The existence of old mine workings in the locality could be a positive indication.
The Ridgelands gold workings are an extensive area of shallow shafts to a maximum depth of 24.4 metres, remaining within the weathered zone, within an area of distinctive reddish soil.
Mapping indicates several bigger parallel reefs from 0.5m to 3m wide with likely flat dips were selectively mined. Early assays reported from the old Kirker reef were as high as 214g/t gold.
Three holes each intercepted 2m intervals from surface that carry better gold grades, including 1.15g/t gold, 1.03g/t and 1.24g/t gold.
Additionally, one hole intercepted 6m at 1.78g/t from surface.
Three other intercepts include 2m at 3.54g/t gold from 10m depth, 2m at 2.68g/t gold from 6m depth and 2m at 2.34g/t from 4m depth.
The company says the geological relationships point to possible pipe-like intrusives – or pencil porphyry deposits - which typically comprise elongated narrow structures, often with high-grade mineralised cores.
Apart from historical thin testing of the external margins of the gold-rich zones, the company has not yet identified any geophysics or deep drilling at Ridgelands or on nearby similar magnetic targets.
The Ridgelands data review was prompted by the company’s more extensive review of its current assets, starting with its Ridgelands, Greenbank and Cockatoo projects in eastern Queensland.
The company wants to generate walk-up targets for reconnaissance exploration fieldwork in the second half of the year that offer shallow, near-surface prospectivity and unexplored depth potential in geological terrain hosting major gold±copper deposits.
Ridgelands is also well-situated close to the handsomely endowed Mt Morgan mine.
The company’s Greenbank and Cockatoo projects lie about 280km south-southeast and 280km south of Ridgelands respectively, and both are also strategically located next to other major gold projects.
Middle Island’s Greenbank project area sits immediately west of the Mt Rawdon gold mine.
Evolution Mining through its subsidiary, Mt Rawdon Operations, has owned and operated Mt Rawdon since November 2011. The company has a long history of reliable production, having produced more than 2 million ounces of gold to date and about 80,000 to 100,000 ounces annually.
Middle Island’s Cockatoo project lies south along strike from Aeris Resources’ widely recognised Cracow gold mine, which is on or close to the major contact between the Bowen Basin and the New England Fold.
The high-grade, low-cost Cracow operation has been continuously operated since 2004.
Gold was discovered in the area in the 1930s and more than two million ounces of the glittering metal have since been mined from the Cracow goldfields, including production from underground and open pit operations.
Middle Island Resources chief executive officer Roland Bartsch said: Ridgelands is the first project off the rank; the data compilation has highlighted multiple targets. The primary target at the historical Ridgelands goldfield stands out, where 1980s exploration defined shallow gold mineralisation that appears to be open at surface and where there is no record of it having been tested at depth.”
In total, the company has identified five separate project areas from its overview of its Queensland gold-copper project. The Ridgelands, Greenbank and Cockatoo projects are protected by granted exploration permits, while two other areas, Acacia and Fernbank, are still under application and awaiting grant.
At Ridgelands, it has defined near-surface gold in drilling, along with a handful of other targets such as lode-gold and copper-gold skarn mineralisation on the Ridgelands Granodiorite contact.
Patchy testing of some of the known skarns was undertaken mainly by Esso Australia in the 1970s.
Ridgelands’ location is favourable, with excellent proximity to power, road, rail and port infrastructure.
Exploration to date at Ridgelands might have been thin and sporadic but Middle Island could still find itself in the box-seat to define a significant gold+/-copper target by employing modern, well-designed exploration.
With the passage of time, a host of techniques have evolved that were not even thought of or possible in the 1970s, while geochemical detection limits have dropped by as much as two orders of magnitude, and analytical costs have been reduced by process automation.
Remote sensing, satellite and multi-spectral imagery and geophysical methods, and their related 3D colour processing of data, have further transformed the game and companies can now cheaply run their own passive geophysical surveys, although usually with external data processing.
Middle Island’s next phase of work will include field check-sampling and mapping and landowner access discussions. The company expects its upcoming programs will also include detailed geophysics, such as induced polarisation, both shallow and deep drilling, subject to the results of its preliminary reconnaissance checks and geophysics.
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By Doug Bright
