Aeris Resources’ Tritton Copper Operations, located near Nyngan in New South Wales, is targeting 27,000 tonnes of copper production in FY18. Ore is currently sourced from the Tritton and Murrawombie underground mines. The operations are 100 per cent owned and operated by Aeris’ subsidiary, Tritton Resources Pty Limited.
History of the Tritton Operations
Mining within the Tritton area in modern times began in 1992 at the Murrawombie open pit and heap leach operation by the Girilambone Copper Company, a Joint Venture between Straits Resources (now Aeris) and Nord Pacific. The Girilambone Copper Company eventually became a wholly owned subsidiary of Straits Resources. Operations at the Girilambone copper project involved the mining of several open pits to recover copper oxide ore that was treated by heap leach, followed by solvent extraction and electrowinning processing to produce copper cathode. The Murrawombie pit was the largest of the mines. Open pit mining at Girilambone ended in 1999, although copper cathode production continued for two more years.
Leaching of residual copper from the Murrawombie heap leach continues today. Approximately 400 tonne per year of copper is extracted from the leach solution as a copper cement by reaction with scrap iron.
Exploration by the Straits Resources and Nord Joint Venture resulted in the discovery of the Tritton deposit in 1995 as part of an exploration program focused on the historical Budgerygar and Bonnie Dundee copper gold mines. Geophysical techniques were successful in identifying the buried Tritton deposit 800m to the south of these historical workings. Tritton Resources Limited was formed to develop the Tritton deposit. It was for a time listed as an independent company on the Australian stock exchange, before being privatised as a subsidiary of Straits Resources.
All Copper concentrate is sold to Glencore, following a life of mine offtake agreement executed in September 2012.
Mining and processing
At current production rates, the Tritton Copper Operations have an estimated mine life of six years. This said, Aeris has an extensive portfolio of identified exploration and development projects, and remains confident about the long-term growth prospects at the Tritton Copper Operation, and the potential for further discoveries in this highly prospective region.
During FY2017 three major capital projects were commenced which set-up the Tritton Copper Operations for the coming years:
· Ventilation Shaft at the Tritton Underground Mine;
· Commissioning of Murrawombie Underground Mine; and
· A strategic $7.5M exploration program on our Tritton tenement package
The 864 metre, 5 metre diameter, Ventilation Shaft at the Tritton Underground Mine will enable mining to be extended to at least 4000mRL at production rates of 1Mtpa or better and will be commissioned in the first quarter of FY18. Development of the Murrawombie Underground Mine commenced in FY17 and replaces the North-East / Larsens mine, which ceased production during the year. The Murrawombie underground mine will reach full production during FY18. To view the Vent Shalf Video; please click here.
Ventilation fans being installed at Tritton Underground Mine
Mining methods at the Tritton underground operations include sublevel open stoping or retreating bench stoping. Stope orientation is transverse and longitudinal depending on the geometry of the ore lenses. Backfill at the Tritton mine is cemented paste fill from reused mill tailings, whereas the Murrawombie underground mine utilises dry waste backfill.
Ore from the Murrawombie underground mine is trucked 30km by road train to the Company’s 1.8 million tonne per annum processing plant, located near the larger Tritton underground mine. Here the ore is processed through conventional crushing and flotation methods, producing a clean copper concentrate.
Concentrate is transported by rail to the port of Newcastle, and is then shipped to smelters, predominantly in the Asia Pacific region.
The Tritton deposit is a large, (over 20 million tonne), copper dominant VMS system, discovered in the mid 1990s via geophysical methods.
Mining of the Tritton ore body commenced in 2004 with the development of an access decline and construction of a sulphide ore processing plant. Copper is extracted via conventional crushing and flotation circuits producing a copper concentrate. Stope production commenced in March 2005. In its first year of production, Tritton produced 23,088 tonnes of copper in concentrate.
Tritton reached 10 years of production in 2015 with significant Mineral Resource remaining. As at 30th June 2016, the combined Measured, Indicated and Inferred Tritton Mineral Resource Estimate is 11.2 million tonne at 1.5% Cu for 169 thousand tonne of copper metal. Find out more
Murrawombie Underground Mine
The Murrawombie deposit is located in the southern area of the Girilambone Complex. The deposit is the largest concentration of copper metal outside the Tritton deposit, with 110 thousand tonne of contained copper 8 Million tonnes at 1.4% copper (as at 30 June 2016).
Murrawombie was mined in the 1990s as an open pit to access the oxide portion of the deposit for heap leach processing. However the sulphide portion of the deposit was not mined due to its unsuitability for heap leaching.
A feasibility study has been completed to design an underground mining method for extraction of the deeper sulphide ore. The Aeris Board recently approved the start of the Murrawombie underground mine, with full production to come on stream in FY17.
The production from Murrawombie mine has replaced the production from the Larsens and North East mines, concluded in July 2016, production rates of up to 650,00 tonne per year are planned.
The mine will have decline access for truck hauling of ore to the surface. 600m of the decline is already in place from mining in 2008. Ore will be extracted by sublevel open sloping and pillar recovery by caving methods. Ore will be trucked to the Tritton plant for processing as a blend with Tritton mine and other deposits.
Stope backfill will use the crushed rock on the Murrawombie heap leach pads, helping with closure of the pad. Find out more