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Rare Earth Elements in W.A
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Several large mining and exploration companies have completed regional appraisals of the district for mineral sands, gold, uranium and base metals. In the 1990s, exploration was common for lignite and brown coals, with several coal mining leases taken out in the eastern part of the Mt Ridley Project area. In the early 2000’s, well before the discovery of Nova-Bollinger, a significant 60x15km coincident gravity-magnetic feature, known as the Grass Patch Complex, was recognised by large resource companies. It was researched for a new, large layered mafic intrusion with the potential to host nickel-copper sulphide deposits and PGE deposits.
In November 2020 Mount Ridley Mines Limited (“MRD”) commenced a review of data for its namesake Mount Ridley Project and surrounding area.
The review concluded that areas of the Biranup and Nornalup geological provinces in south-eastern Western Australia have the potential for REE mineralisation, and in particular, the style of mineralisation referred to as Ionic Adsorption Clay (IAC-REE).
Globally, deposits of IAC-REE are most significant in southern China and are the world’s main source of heavy Rare Earth Elements.
rare earth elements
REE mineralisation occurs as large, horizontal, near surface, sheet-like lenses up to a depth of 89 metres. REE mineralisation is interpreted to be present within the in-situ saprolite clay horizon. Patchy lower grade zones occur within transported cover which may vector towards stronger REE mineralisation deeper within the regolith.
Geological Survey of Western Australia (DMIRS) mapping[1] shows that the Mount Ridley Project REE mineralisation occurs within the weathered mantle (regolith) of the Recherche Super-suite, which is described as “granitic and mafic gneiss; may include intrusions of Esperance Super-suite”.
While the source of the REE mineralisation is currently unknown, a detailed sample and litho-geochemistry dataset from bottom of hole aircore samples has been established which includes whole-rock chemical analyses, sample pulps and some end-of-hole air core samples. These samples and data are being studied by the Company’s consultant geochemist to identify the primary rock-type and whether units are REE-enriched.
[1] (DMIRS) Department of Mines, Industry Regulation and Safety 1:100,000 Interpreted Bedrock Geology
