An "unsolicited" lithium review at Estrella Resources’ Carr Boyd nickel project near Kalgoorlie in Western Australia has spun out both new and historical pegmatite potential – but the extent and lithium content is not yet known.
The company says the approaches from an unnamed third party – which it describes as a “leading global mining group” – to evaluate the possibilities for lithium-caesium-tantalum (LCT)-type pegmatites at Carr Boyd, led to the review that has only reconfirmed its belief in what it believes the project may hold.
Management says an area of surficial quartz and pegmatite float material in alluvial and colluvial sediments that is 9km-wide and 14km long is associated with the Carr Boyd monzogranite. Magnetics and historic drilling within the area show it to be underlain by the Carr Boyd mafic intrusion and that pegmatites have developed within it.
It adds that further support for that theory is provided by an auger drilled geochemical program it undertook while exploring for nickel and which partly overlapped the sub-crop and float. Modelling of the LCT results from the program identified a moderate level of anomalism some distance from the margins of monzogranite and into the surrounding pegmatite field.
It is seen as a positive indication that the fractionating pegmatites could also potentially produce rare earths within the tenure.
Estrella Resources managing director Chris Daws said: “While it is only early days in our understanding of what could be a significant pegmatite field located on our Carr Boyd Ni/Cu mine exploration area, we are nonetheless pleased with the modelling of soil geochemistry work which highlights the project’s LCT potential. The Estrella team is at the initial phase of a staged work program to evaluate the lithium prospectivity on our 100% owned tenure. With further work, we hope to ascertain a strong understanding of this possibility which may eventually lead to generation of lithium targets for drilling.”
The company recently revealed that it was examining all available geological and geophysical datasets in a bid to determine the likely presence and potential extent of lithium-bearing pegmatites within its 228-square-kilometre tenement holding at the Carr Boyd layered intrusive complex. But it was adamant the assessment would not detract from its ongoing efforts to find a significant nickel sulphide deposit at Carr Boyd.
Historically, the complex is better known for its mafic-ultramafic-hosted nickel potential than for mineralisation such as LCTs, which are typically associated with acidic and late-stage granitic rocks.
In addition to the external inquiry, Estrella’s recent lithium interest in the complex arises from a new lithological classification and its 3D visualisation, which confirmed its interpretation of the orientation and geometry. It shows the complex lying on its side, having been rotated 90 degrees from its original orientation along a north/north-west, south/south-east rotational axis.
It means that primary igneous layering that would have originally been more or less horizontal is now steeply-dipping and that the south/south-west edge of the complex potentially represents the original floor or basal contact.
Almost all historic exploration in the area was nickel-related – no-one was looking for lithium and rare earths back then and even tantalite only had a relatively short run in the 1980s.
So while limited and mostly only visual information to date suggests the nearby presence of extensive and thick pegmatites, there is little information relating to LCT prospectivity, the actual extent, thicknesses or orientation of pegmatites – nor their level of mineralisation.
Estrella has obtained hand specimens of pegmatite from historic diggings in the area and they offer encouraging evidence that the pegmatite system is fractionating as it moves south and away from the monzogranite. It is a factor considered for any LCT model.
Additionally, potassium radiometrics provide a useful insight to the possible extent of pegmatite development to the south and west and at least provides a guide as to where to look first.
In contemplating its way forward, Estrella considers that a staged approach will be required, initially to determine the LCT potential of the “source granite” and the geochemistry of the resulting pegmatites and then more detailed field and geochemical investigations.
Management says that work will be followed up with broad-spaced geochemistry to determine fractionation patterns and for broad anomaly generation.
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By Doug Bright
