Rox Resources Limited (ASX: RXL) and joint venture partner Venus Metals Corporation Limited have obtained improved metallurgical testwork recently conducted on the Youanmi Deeps Resource, located within the OYG JV area (Rox 70% and Manager, VMC 30%) in Western Australia.
Managing Director, Alex Passmore, said thework forms part of development studies currently underway into potential future production at the Youanmi Gold Project. This preliminary part of the study will establish processing pathways to optimise gold recovery prior to progressing to more extensive and detailed “feasibility study level” metallurgical testwork.
“In June 2021 we reported a 30% increase in the Youanmi Deeps Resource, and now we are pleased to report that advances in gold extraction technology over the last 30 years (since GMA built its processing plant) have made a significant difference in gold recovery,” Mr Passmore said.
“Preliminary metallurgical testwork indicates a 10% increase on historical gold recoveries by utilising a pressure oxidation leach process (i.e. POX).
“Furthermore, we look forward to results of (scoping level) process plant design and costing later this year being undertaken by Como Engineers who have a long track record of success for both design and development of similar sized gold processing facilities in WA with a variety of flowsheet designs.”
The principal past producer at Youanmi, Gold Mines of Australia (GMA) operated the Youanmi Deeps underground mine in the 1990s. At which time GMA also operated a 600ktpa oxide ore CIL plant configured to handle 270ktpa of sulphide (i.e. Youanmi Deeps) feed through a bacterial oxidation plant (Bachtech technology). During this period the operation achieved an average of around 87% metallurgical recovery up until the plant shut down in November 1997.
Rox’s September 2021 testwork results included two composite samples taken from 30 individual diamond drill core intervals of historical drilling comprising of mainly half and quarter NQ drilling core, including 14 sections from the upper part of the Hangingwall Lode domain, and 16 sections from the upper part of the Main Lode domain. The Main Lode, and Hangingwall Lode domains combined represent over 30 percent of the entire Deeps Mineral Resource.
Processing Plant Scoping Level Study
Como Engineers have been engaged to conduct scoping level design and costing including capital cost estimate and operating cost for a processing plant solution which will include utilising parts of the existing 1990s circuit where appropriate into a new build located away from the recently discovered Grace mineralisation.
The flowsheet design is based on utilising a standard crushing and grinding circuit to 75 microns, before performing conventional flotation to extract the high gold grade sulphides, after which float concentrates are re- ground to 15 microns before undergoing a pressure oxidation leach process to liberate gold at very high recovery rates. Float tails will also be leached to ensure highest possible gold recoveries overall.
The scoping level design work is based on a small processing plant of just 300 ktpa capacity incorporating a relatively small Pressure Oxidation Leach (POX) circuit as the base case option being considered. The size of the POX circuit is small comparable to other low grade high tonnage operations for two main reasons. Firstly, very low mass pulls achieved of under 15%, and secondly, the low tonnage nature of the plant required to treat very high head grade material from the Deeps Resource (noting resource grade is over 7.5 g/t Au).
Other oxidation process technologies are still under consideration to establish the most economically feasible solution going forward.
Next Steps
The testwork has demonstrated a well understood pathway to very high gold recoveries, something which was not achieved in the 1990s, and further testwork in combination with the costing studies will determine the optimal and most economical feasible process solution, exploring various other suitable processes.
Further testwork in combination with the costing studies will determine the optimal and most economical feasible process solution. The additional testwork is not only recovery related.
Incremental capital cost versus gold recovery analysis outcomes are being continuously examined with current flow sheet scenarios.
Future work is planned to include a wider range of underground resource domains for which the OYG JV has abundant samples in the form of diamond drill core, including the recently discovered Link area to the north of the current deeps resource, which after geological modelling has been completed will be included in the next resource update.
For further information please visit: https://www.roxresources.com.au/
