Reach Resources says geophysics, geochemistry and rock microscopy have confirmed a 4.5-square-kilometre oval body as an alkaline intrusive and the likely source of big rare earths-niobium hits at its Wabli Creek project in Western Australia’s Gascoyne region.
The company says its latest discovery arose from the acquisition and interpretation of detailed geophysical data by consultants Southern Geoscience (SGC). It peered through previous low-resolution imagery and highlighted the footprint and intrusive contact boundaries of the body, which had initially been considered a granitic pegmatite and the most likely principal source of the rare earths-lithium-caesium-tantalum (LCT)-style mineralisation.
Another additional important factor was the coincident association of the bulk of the rare earths and niobium anomalism with the margins of the intrusive, as noted by consultants Sugden Geoscience. Several other targets were also identified by SGC and they are thought likely to be satellite intrusives into major structures around the main ovoid body that have strong potential to also carry high-grade mineralisation of similar style.
Wabli Creek is one of two exploration licences held by Reach in the highly-prospective Yinnetharra area that is well-known for its often unusual, but critical mineral assemblages. Many of those occurrences, such as the rare earths-LCT style of mineralisation around Morrissey Hill and Camel Hill about 13km north of Yinnetharra Station, are pegmatite-related and have been prospected and mined for decades.
But the same suite of minerals can be hosted by other rocks, too, such as in alkaline carbonatites or in the monazite associations hosted by other rocks, as seen within Hastings Technology Metals’ Yangibana project, about 140km north of Wabli Creek. Yangibana represents one of the world’s most highly-valued deposits of neodymium and praseodymium (NdPr), in addition to abundant niobium with monazite in ironstones.
Reach Resources chief executive officer Jeremy Bower said:“The identification of the host of the high-grade niobium and REE as a fine-grained alkali rock and these new targets provided by Southern Geoscience is another major breakthrough for the project. We now have the trifecta of data highlighting the potential of this project: geology confirming in situ mineralisation, geochemistry confirming high-grade niobium and REE assay results and geophysics showing coincident anomalism in the magnetics and radiometrics.”
The company first reported on the outcome of a tenement-wide, 1489-sample soil geochemical program at its 100 per cent-owned Wabli Creek project last December. Anomalous rock chips reported levels of niobium pentoxide between 14.3 and 32 per cent, accompanied by a peak total rare earth oxides (TREO) assay of 2.57 per cent and the program significantly extended the known anomalism and threw up multiple targets in both of the company’s tenements.
Further geological and geochemical evaluation corralled and ranked that anomalism into 16 strong, coherent rare earths-niobium targets for further assessment and they were put up for inclusion in follow-up programs. The company kicked off that subsequent field work in March with further rock chip sampling and mapping and potentially, drilling.
Back in May, Reach said it had used geophysics to identify an areally-extensive ovoid intrusive body within its southern licence. The outline of the body as defined from magnetic data measures about 3km long and 1.8km wide.
It was initially interpreted as a magnetic low feature and believed to be consistent with a late-stage intrusive granitic body or sequence. The body naturally elicited a heightened level of interest, mainly because three of the 16 priority soil geochemistry targets set for evaluation were noted as being coincident with historic small-scale niobium (as columbite) mining.
But the targets also coincide with arcuate and linear structures on the margin of the interpreted intrusive. Subsequent review and interpretative work increased the number of potential targets from 16 to 27 for further evaluation of the project’s expansion possibilities.
By June, the over-arching view seemed to be that the late-stage ovoid intrusive feature was probably a granitic pegmatite and likely to be the primary source of the ubiquitous rare earths-LCT anomalism at Wabli Creek. However, from later geochemical data, it was not possible to discount the chance that the intrusive could be an alkaline carbonatite body.
Reach says its most recent geophysical interpretations were mainly concerned with finding previously unrecognised locations that could host additional prospective intrusives hosting rare earths-LCT style mineralisation. As a result, targeting strategies remained focussed on lithological associations, structural context and complexity and deformation and proximity to possible source granitic bodies.
Now that the source of the high-grade rare earths-LCT has been confirmed as a fine-grained alkali igneous rock and that it could be found to have affinities with or be analogous to the classic carbonatite style of mineralisation, the model has changed radically. For example, the project could be similar to Venture Minerals’ more extensive Jupiter intrusive body that stretches for 40sq km.
Reach says further laboratory work is in train to confirm the presence of mineral assemblages in or from weathered forms of its intrusive, which might confirm where it sits in the broad suite of carbonatite-related rocks. The next spaces to watch will be how the laboratory characterisation work pans out and how many satellite intrusives could show up, in addition to establishing the relative timelines between the country rocks, the pegmatites and their host rock and the alkaline intrusive bodies.
The latter assessment could assist management with understanding the origin and style of dark, fine-grained mineralised pegmatite-related rocks on the margins of the intrusive.
Reach has completed its heritage survey at the Wabli Creek project. The company already has more mapping and sampling underway and it is also proposing petrological analysis of samples to determine mineral types and drilling once heritage and regulatory approvals have been obtained.
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By Doug Bright
