JOHANNESBURG (miningweekly.com) – Gold junior Reed Resources on Wednesday said early indications were that the change to ore block interpretations at its Meekatharra gold mine, in Western Australia, had improved the mine-to-mill reconciliation.
The company performed an external and independent review of Meekatharra’s grade control and reconciliation processes in April and early May. The review recommended some areas for improvement; however, concluded that the work at the southern Bluebird ore lodes in general was being carried out in typical Australian openpit mining standards.
Immediate action was taken to tighten up ore lock interpretations to exclude as much as practicable, marginal material and increase the feed grade to the processing facility.
Reed announced in June that the mine-to-mill ounces reconciliation had declined materially from that previously achieved.
Also in June, Meekatharra tightly constrained the northern ore block, interpreting assay data sets as discrete higher-grade mineralised zones in readily identifiable shears. Although the continuity of gold distribution in the northern lodes was not readily identifiable in the geological date, the northern ore zones appeared to present as dispersed and disparate gold accumulation in identifiable sheer zones and anomalous gold accumulations between shear zones.
This contrasted with the southern Bluebird ore lodes that were clearly identifiable in the stratigraphy with little dissemination either side of the ore grade intercepts. Reed noted that Meekatharra’s implementation of the review recommendation to tightly constrain the other Bluebird ore lodes may have exacerbated the variance between mined and milled ounces in June.
Revised geological interpretation indicates that the northern Bluebird ore lodes appeared to present quite differently to the southern Bluebird ore lodes. A significant geological feature cutting through the Bluebird pit appears to create a structural boundary between the southern and northern lode systems.
Meekatharra performed further grade control drilling in the northern and southern Bluebird ore lodes in the second half of June, which had been combined with face sampling, blast-hole definition sampling and existing geological data to better define the ore blocks remaining to be mines from Bluebird.
Although not definitive, Reed had compared the depleted resource estimate with Meekatharra’s grade control model that incorporated historic and recent grade control data below the 400 metres rotary level and represented the approximate location of the Bluebird pit floor at the end of June.
The grade control model and estimate confirmed that about 58 500 oz of gold remained to be mined from Bluebird from below the 400 metres rotary level at a 0.6 g/t cut-off.
About 84% of the remaining ounces were contained in the southern high-grade ore zone, with the miner stating that much of Bluebird’s production in July and August would be sourced from the higher-grade southern ore zones.