Mount Ridley Mines says it has defined rare earths mineralisation at depths ranging from 6m to 41m – with intersections averaging 12m and total rare earth oxides (TREO) grades frequently going 1200ppm – at its Mia project, about 50km north-east of Esperance in Western Australia.
The results have emerged from the company’s recent grid-based, resource-focussed drilling of 155 air-core (AC) holes at its most advanced project. The program infilled a previous reconnaissance drilling pattern put in at a spacing of 2500m by 400m, covering a 27-square-kilometre area on section lines spaced 400m apart, with holes selectively spaced between 100m and 400m.
The best 10 holes of the infill program include a headline intercept length of 31m at 1379ppm TREO from 18m, of which 22 per cent comprises magnet rare earth oxides (MREO). The highest TREO grade of 2194 parts per million was identified in a 9m intercept from 21m and included 24 per cent MREO.
To date, the company has defined rare earths mineralisation at Mia along a north-east/south-west-trending strike of more than 8km and it remains open beyond that in both directions. It is continuing its geological modelling from drilling data and anticipates releasing its maiden mineral resource estimate for the Mia prospect by next month.
The new drill intersections provide a higher level of confidence regarding continuity of mineralisation between high-grade REE holes. The project continues to advance rapidly with each set of new results adding valuable information as we work towards our maiden mineral resource estimate for the central zone of our Mia Prospect. Mount Ridley Mines chairman Peter Christie
Management says the desirable and more highly-valued MREO content comprises as much as 25 per cent of the TREO encountered in its samples, while thorium and uranium numbers remain low.
It interprets the mineralisation as a supergene rare earths deposit hosted with kaolinitic clays overlying a granitic or gneissic contact. The highest rare earths grades occupy a sinuous geological structure, which is evident in aeromagnetic imagery and inferred as being associated with the contact zone.
While Mount Ridley is likely to be tempted to interpret the sinuous feature as a possible palaeochannel incised into the ancient granitic surface that has become filled with mineralised clays, similar to some other projects, its exploration of the trend shows it contains elevated niobium and yttrium, which is interpreted as originating from calc-alkaline rocks rich in metals that might have been emplaced along the line of contact.
Management says relatively undisturbed sample material from more than 50 mineralised drillholes at Mia has been stored, providing the company with location-specific identifiable material for current and future metallurgical testwork.
The work to date has indicated that significant beneficiation of potential “ore” material, up to 160 per cent, can be achieved by screening and it has also demonstrated that hydrochloric acid is an effective leachant to move the rare earth oxides from the clays into solution.
Mount Ridley’s largely contiguous rare earths project comprises nine granted exploration licences centred about 80km north of Esperance on the south coast of WA. The ground covers about 3400sq km and extends parallel to major north-east/south-west-oriented regional structures including the Coramup Shear and Heywood-Cheyne Fault.
Including Mia, the company has defined seven target areas throughout its tenement suite.
If Mount Ridley can define an 8km-long rare earths mineralised zone at Mia that might be up to 2km wide and a conservative 10m thick, it will have a handy resource upon which to develop its project … and it may then look to achieve similar outcomes in its remaining ground.
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