A calculated punt by Allup Silica to test for rare earths at its Pink Bark project, 90km north-east of Esperance in Western Australia, has seen it hit clay-hosted mineralisation beneath the sand in its maiden drilling program.
The company today revealed results from the program that returned intriguing intercepts of 1m at 1169 parts per million total rare earth oxides (TREO) from 20m, 1m at 1985ppm from 21m, 1m at 798ppm from 8m and 1m at 659ppm TREO from 9m.
Allup says the high-value magnetic rare earth oxides (MREO) of dysprosium, neodymium, praseodymium and terbium make up an average of 23.6 per cent of the TREO in the intercepts, while the critical rare earth oxides (CREO) of dysprosium, europium, neodymium, terbium and yttrium make up an average of 23.4 per cent.
Allup Silica managing director Andrew Haythorpe said: “Our air-core drilling program at Pink Bark has yielded encouraging results, with significant clay-hosted rare earth elements discovered, reaching grades of up to 1985 ppm TREO. This highlights a previously unrecognised potential for REO mineralisation in clay units beneath and beyond drilling to date. At Allup Silica, we're committed to developing critical mineral deposits vital for the energy transition.”
Management says its maiden drilling effort consisted of 26 holes for 421m at an average depth of 16.2m. The holes were not drilled to basement and as a result, have not adequately tested the full thickness of the rare earths-enriched clay horizon immediately overlying the granites believed to be the parent rock.
OD6 Metals has a clay-hosted rare earths play at Splinter Rock, about 120km to the east of Allup’s ground, with a resource of 344 million tonnes at 1308ppm TREO, with a 1000ppm grade cut off. Splinter Rock is comparable to Pink Bark in that both have rare earths-enriched clay horizons directly overlying or adjacent to the granites of the Albany-Fraser Orogen.
The Splinter Rock clay horizon overlies the Booanya suite granites of the eastern Nornalup zone, while Pink Bark clays sit above the granites of the Biranup zone. Both granites are thought to be rare earths-enriched, representing an exploration focus for multiple companies in the area.
Uplift along the craton margin caused the granites to become deeply weathered, resulting in the formation of basin features that now host a network of clay-plugged channels. Acidic groundwater and topographic differences are believed to have mobilised rare earths from the granites into groundwater, enriching the clays.
Interestingly, Allup says the virgin clay enrichment may be even higher than indicated, due to assays being undertaken using four-acid soluble digestion, which does not return results for resistant non-acid soluble rare earths.
The company says it will now attempt to establish the continuity of the Pink Bark prospective clay zones along strike and at depth through a follow-up drilling program scheduled to begin in November, with heritage approvals already granted.
To guide the drillbit, Allup will also undertake airborne geophysical surveys and a mini seismic survey to see just how much rare earths-bearing clay sits beneath its sands.
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By Andrew Duffy
