Underground operations at Mt Morgans are sourced from the Westralia mine area which comprises the Beresford and Allanson deposits. The deposits are ~15km from the Mt Morgans treatment plant.
The deposits occur over a horizontal strike distance of 2.8km and lies within 700m of the surface. Previous mining and on-site treatment of the deposit has demonstrated that the gold is free milling with recoveries of 91%-93% achieved historically from conventional site-based CIP/CIL processing.
The gold at Westralia occurs within a banded iron formation (BIF) unit from which approximately 900,000 ounces at 4.5 g/t gold was produced up to 1998; with the majority being sourced from the Westralia open pit and historic underground workings.
Underground mining at Westralia is by Long-Hole Stoping methods (LHS), retreating to three separate declines – two at Beresford and one at Allanson.
STRATEGY FOR THE WESTRALIA MINE AREA
During the March quarter of CY2020, a detailed review of current underground mining operations determined that a revised strategy for Westralia is warranted.
During this review period, capital development will cease and stoping from levels currently in production will be completed. Ore drives currently in progress (followed by stoping) will also be completed by 31 August 2020. Optimisation studies for Westralia are underway.
During this optimisation period, the Company plans to conduct various activities including the following:
- Confirmation that Westralia's updated Mineral Resource and resultant Ore Reserve performs in line with expections.
- Determine the optimal operating model including production rate, capital development requirements and equipment size to ensure the mine can sustainably operate on a positive cash flow basis moving forward.
- Analysis of grade control drill spacing with respect to more accurately predicting mined grades over short intervals.
- Further underground drill testing during FY2021 to drive future investment decisions.
With 195,000oz in Ore Reserves and 655,000oz in Mineral Resources (see ASX announcement dated 27 February 2020), the Company believes there is potential for a de-risked operating model at Westralia.
The review period will afford the Company time to have reasonable confidence that the operation can be a sustainable positive cash flow contributor in the future.