Terrain Minerals has settled on an exploration target range for its Larin’s Lane prospect near Mt Magnet in WA of between 25 and 33 million tonnes at a total rare earths oxide grade between 880 and 980ppm TREO and from 19 to 21ppm gallium.
The company says it expects to launch drilling next year to update that exploration target estimate once results from the program are to hand.
The maiden Phase-1 conceptual target ranges are based solely on Terrain’s limited air-core (AC) drilling results from the shallow regolith / oxide zone above unweathered bedrock.
The exploration target was defined by well-recognised Perth geological consultants SRK Consulting, from drilling which covers a mere 5 per cent of the total known, mapped, estimated or inferred prospective geology.
With that limited initial area extent in mind, SRK has designed a follow-up scout AC drilling program comprising a further 53 holes for a proposed 3500m of advance aimed at tripling the area of prospective geology.
Terrain says it sees the extensive, laterally-persistent and cohesive gallium anomalism as being of particular interest at the project.
Last year, the company undertook a 101-hole AC drilling program in the area which established that anomalous levels of clay-hosted rare earth elements and gallium mineralisation have both developed in the regolith.
The anomalism seems to occur along the trend of an elongated amphibolite body which sits on or within 500m of a contact between two adjacent granitoids, most notably in three separate zones, each zone being about 1km long.
Those three zones combined now constitute the total maiden South, Central and North targets which together make up the total Exploration Target estimate.
The depth of the relatively shallow AC drilling at the project is limited by the undulating surface topography of the bedrock which consists of two monzogranites of the Walgunna suite, with scattered patches of amphibolite and north-east and east-trending mafic dikes cross-cutting the southern corner of the tenement.
Higher-value rare earths signatures appear to be strongly associated with the contact between two granitoids and are neatly mirrored by gallium anomalism above 35ppm to peak values of 50ppm gallium.
Selected gallium oxide intercepts encountered in Terrain’s drilling last year above a cut-off grade of 40.32ppm gallium saw a best intercept of 16m at 53.74ppm gallium oxide (Ga203) from 64m depth, with another hole running 20m at 48.33ppm gallium oxide from just 4m depth. A third hole gave up 30m at 40.32ppm gallium oxide from 24m depth.
Those hits offer some idea of the vertical distribution of gallium mineralisation in the near-surface regolith profile.
Terrain Minerals executive director Justin Virgin said: “We’re excited to announce this initial Exploration Target for the Larins Lane Project, marking a pivotal step in unlocking the project’s vast potential. The Phase One findings have shown us just a glimpse of what Larins Lane holds, and our planned drilling campaigns aim to substantially increase our understanding of the resource.”
Continuous gallium responses between drill holes above a nominal cutoff of 20ppb exists within two distinct horizons, a shallow one usually extending from surface to a about 12m deep and a second deeper horizon ranging in thickness between about 21 and 80m deep, bottoming out on the bedrock.
Better TREO responses – above 1000ppm TREO - generally occur at the base of the regolith, on the transition to bedrock or drill refusal, broadly between depths of 57m and 80m, with grades ranging between at least 400 and 2600ppm TREO.
In the deeper horizon, gallium results hover around the 20ppm mark in direct association with the highest TREO values but appear to increase in value in a layer between 3m and up to about 25m thick, sitting just above the better TREO values.
The Larin’s Lane prospect is part of Terrain’s Smokebush project area about 40km west of the historic gold mining centre of Paynes Find in Western Australia’s Mid West.
Terrain engaged SRK Consulting to conduct an interim review of the available geological and drilling data to assess the prospectivity of the area.
Following its initial data review, SRK Consulting concluded that sufficient data exists in selected parts of the deposit to define a JORC-compliant rare earths and gallium exploration target.
In a related research foray, Terrain is a participant in the Minerals Research Institute of Western Australia (MRIWA) research project M10528 and in the light of recent gallium results from Larin’s Lane, it plans to provide selected samples from the next round of drilling at the project for a series of metallurgical extraction processes through Curtin University.
The aim of the government-sponsored research project is to optimise the recovery of regolith-hosted critical minerals –including gallium - with a particular focus on extraction by organic solvents which are almost pH-neutral.
Results from the research project will be provided to Terrain over the next 12 months and could play a significant role in future evaluations of the project’s gallium potential.
The Larin’s Lane mineralisation contains coherent, contourable gallium anomalism in distinct zones which extend along the granite contact for between 1km and 2km and can be identified as related to or confined by particular horizons.
The emplacement and concentration mechanisms and controls could include regolith environments, humic content, geological contact and other source influences, possible reduction-oxidation boundaries, groundwater saturation and salinity boundaries and possibly also structural conduits.
The metal gallium was discovered spectroscopically in 1875 by French chemist Paul-Émile Lecoq de Boisbaudran. The name comes from the Latin word for France, Gallia.
Gallium melts near room temperature and has one of the largest liquid ranges of any metal, so it has found use in high-temperature thermometers amongst other things.
It easily forms alloys with most metals and has been used to create low-melting alloys. It is used as a doping material in the lucrative semiconductor industry and is used to produce solid-state items like transistors and light-emitting diodes.
Gallium arsenide can produce laser light directly from electricity. Large amounts of gallium trichloride (GaCl3) have been gathered to build the Gallium Neutrino Observatory, located in Italy and designed to study particles called “neutrinos” which are produced inside the sun during the process of nuclear fusion.
If Terrain can demonstrate that sufficient volumes of material at meaningful recoverable grades can be proven at the prospect and that metallurgical recovery tests identify practicable extraction methods, there exists potential for Australia to move towards industrial-scale gallium production which at present does not exist in the country.
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By Doug Bright
