Ora Banda Mining Ltd (ASX:OBM) (FRA:M6N) continues to make progress with the ramp-up of activities at Davyhurst Gold Project in Western Australia, with actions taken to ensure delivery of definitive feasibility study (DFS) production levels of around 82,000 ounces recovered for FY22.
Missouri open pit mining is on schedule to begin next month with key items of the mining fleet and site facilities delivered to site.
This open pit is a source of higher grade, harder primary ore feed which will improve mill throughput and gold production.
Open pit and underground mining productivity and production levels have and continue to be impacted by COVID-19 related travel restrictions and the associated extremely tight and highly competitive labour market in Western Australia.
Additionally, processing plant throughput during April and May 2021 has continued to be negatively impacted by low slurry densities caused by the high proportion of viscous, low density oxide material from Stage 1 of the Riverina Open Pit.
The company has taken steps to increase the availability of fresh rock to the mill which is expected to increase gold production levels to DFS levels during the September quarter.
Contained gold within ore mined to date of 26,000 ounces plus ore scheduled to be mined to June 30, 2021, – around 9,000 ounces – remains in line with the DFS estimate of 35,000 ounces while the gold production outlook for FY21 is revised to 13,000-18,000 ounces.
The FY22 gold production outlook of 8,000 ounces recovered, remains unchanged and consistent with the DFS.
“Accelerating ramp up”
Increasingly harder transitional and primary material from the Riverina open pit, together with increasing quantities of primary ore from the Golden Eagle underground mine and the commencement of primary ore deliveries from the Missouri open pit in late June will see a more uniform ore blend available for processing at Davyhurst from July.
This more uniform ore blend is expected to increase monthly gold production to DFS levels during the September quarter.
Ora Banda managing director David Quinlivan said: “Whilst there are always challenges when commissioning a mining project, we are encouraged by the refinements we are making to improve gold production towards the DFS estimates.
“The advancement of Missouri in the production schedule will go a long way to conquering ore viscosity issues encountered during commissioning.
“We are also seeing improvements in a number of other areas of the project, in particular at Riverina and Golden Eagle, which we believe will bode well as we accelerate our ramp-up.”
Missouri open pit
In the DFS, Missouri was planned to be mined in a single stage, which incorporated a three-month pre-strip, but the company has now redesigned the Missouri Open Pit into two stages, which allows ore mining to commence after a modest amount of site preparation.
The Missouri ore reserve grade of 2.6 g/t gold (1.5 million tonnes at 2.6 g/t for 130,000 ounces) is materially higher than the Riverina ore reserve grade of 1.8 g/t gold and mining of the Missouri open pit will increase the average gold grade processed through the Davyhurst mill from July 2021.
Riverina open pit
Mining at Riverina remains slightly ahead of schedule, having delivered more ore tonnes at a slightly lower grade for more total ounces than estimated in the DFS to date.
While the process plant throughput has been impacted by the high proportion of Riverina low density oxide feed, increasingly harder transitional and primary material is scheduled to be mined at Riverina from June 2021.
After lower initial mine ore grades being delivered to the processing plant due to ore stockpiling space restrictions, the company is now utilising high, medium and low-grade stockpiles on the mine ore pad to optimise the processed ore blend.
Golden Eagle underground mineralised zone with flat-lying orientation.
Golden Eagle underground mine
Ora Banda has been working with the underground mining contractor to improve underground production rates with May production to date from the Golden Eagle underground mine of 25,620 dry metric tonnes exceeding the total of production of 25,235 dry metric tonnes during the whole of the March quarter.
Following initial development activities at the Golden Eagle underground mine, new information has led to a review of the geological interpretation of the southern mining area, which had previously been interpreted as a sub-vertical shear, similar to the very consistent north zone.
Development activities identified a fold nose, which has so far been followed up-dip for 60 metres and results in a moderately flat limb to the mineralisation which changes the orientation of the lode.
The new geometry suggests an increased potential for wider, flatter dipping ore zones combined with the narrower sub-vertical zones previously modelled.
Whilst reinterpretation of the mineralisation is underway and needs to be completed, the company is confident that the flat-lying nature of the mineralisation has the potential to increase the ounces per vertical metre in the Golden Eagle underground mine.
On-site preparation laboratory
With heightened mining exploration activity in Western Australia, assay turnaround times have ballooned, with the company’s exploration assays taking several months to be processed and returned.
Ora Banda is awaiting results on around 18,000 assays (incorporating grade control, resource definition and exploration samples) and, working with one of its primary commercial assay laboratories, has identified an opportunity to decrease sample turnaround times by installing an accredited on-site sample preparation laboratory at commercially attractive terms.
The company has begun initial studies to further investigate this opportunity.