ASX-listed Aldoro Resources says high grade rubidium and lithium has been showing up in rock chips collected from its Wyemandoo pegmatite prospect in Western Australia and rubidium values are comparable with the richest JORC compliant global rubidium deposit in Namibia. The anomalous assay data stretches over an area greater than 9 kilometres over four contiguous exploration permits which Aldoro has termed the Wyemandoo project.
The company says over half the 20 samples analysed around a particular structure in the middle of the defined “Fairway Pegmatite Corridor” assayed up at greater than 1 per cent lithium oxide with a maximum grade coming in at a stunning 2.12 per cent lithium oxide. Grades averaged 1.06 per cent lithium oxide across the samples.
The company recently expanded its WA Windimurra lithium pegmatite footprint after settling a deal with Meridian 120 Mining in July 2021 to acquire the Wyemandoo and Niobe tantalum-lithium projects adjacent to its Windimurra project.
The pegmatites at Wyemandoo generally follow a northeast orientation and have a strike length of around one kilometre. They tend to vary in thickness from 1 to 20 metres with shallow to moderate dips, typically 30 to 60 degrees. The Wyemandoo pegmatite swarm appears across a huge northeast trending corridor which is over a 10km long and up to 4km wide, however the full extent is masked by young alluvium cover.
While more than 20 pegmatite dykes have been mapped to date, of which 10 have been sampled, Aldoro says dozens more are yet to be mapped and sampled. Significantly, they are located only 25km north-northwest of the Youanmi lithium pegmatite field owned by Lithium Australia.
Aldoro’s recent review of the Wyemandoo rock chip assay results from three tenements over the lithium mica-bearing pegmatites found exceptionally high assays over nearly 9 km of outcropping strike. The 52 rock chip samples exhibited a range of rubidium values from 12 parts per million to an extraordinary 1.7 per cent with an impressive average grade of 0.54 per cent rubidium.
Interestingly, these grades are comparable to the grades recorded at Lepidico’s Namibian Karibib deposit where, according to Aldoro, the only rubidium JORC compliant deposit in the world has a published 6.7Mt of ore grading at 0.23 per cent rubidium, 0.46 per cent lithium oxide and 320 parts per million caesium.
The Wyemandoo rocks also contain anomalous lithium oxide averaging 0.63 per cent lithium oxide, with a range from 5 ppm to a whopping 2.6 per cent and caesium averaging 146 parts per million, again comparable with the Karibib deposit in Namibia.
Aldoro says the wide range of lithium values in the Wyemandoo pegmatites reflect the variation in lepidolite mica content across the few pegmatites sampled.
However, pegmatites like the “Loop Pegmatite” structure are located further away from the parental granitic source rock, located in the east, and these pegmatites appears to be more fractionated giving rise to elevated lithium, rubidium and caesium values.
The loop structure resides in the middle of the so-called Fairway Pegmatite Corridor and many of the outcropping pegmatites may be similar to the Loop Pegmatite as they occur away from the granitic source rock and therefore have the potential to be highly fractionated and enriched with the
lithium suite of metals according to the company. Management says it will be targeting this zone in the next phase of rock chip sampling across the Fairway Pegmatite Corridor.
A larger systematic sampling program is currently being finalised and is expected to take place later in October and will focus on sampling at 40-meter intervals along the extent of the outcropping pegmatite. Portable XRF will be utilised to indicate the occurrence of rubidium mineralisation for immediate forward planning of drill hole positions.
Aldoro is convinced the Wyemandoo pegmatites represent a new rubidium-bearing lepidolite pegmatite field and the company is encouraged that the assay results so far demonstrate the early hallmarks of what it refers to as a potential “tier 1” critical resources asset.
Aldoro is also conducting a review into the resource economics of the lithium-rubidium-caesium mineral combination given the current price for lithium concentrate containing 6 per cent lithium oxide is roughly $2,100-$2,200 per tonne and the current price for rubidium carbonate is an extraordinary $1.4 -$1.5 million per tonne.
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By Matt Birney
