Mt Clere Rare Earth Project, WA
The Project contains multiple targets, including REE and thorium in enriched monazite sands, REE ion adsorption on clays within the widely preserved deeply weathered lateritic profiles and lastly REE occurring in plausible carbonatites associated with alkaline magmatism.
The Project covers a substantial area of 403km2, in the Gascoyne Region of Western Australia, and was acquired via direct licence application (E52/3720, subject to grant). Whilst the Company is not aware of any reason why the exploration licence for the Project will not be be granted in due course (anticipated within 5 - 9 months), investors are cautioned that there is a risk the exploration licence will not be granted.
The Company will compile the historical exploration data and undertake non-invasive groundwork including mapping and sampling prior to granting of the exploration licence.
The Project is located approximately 200km northwest of Meekatharra, in Western Australia. Access from Meekatharra is northwest along the unsealed road to Mt Augustus via Mt Gould and Errabiddy and Erong Springs stations. Unsealed tracks and pastoral station fence tracks provide access within the project area.
The Project lies near the Errabiddy Shear Zone, a major thrust contact between the Narryer Terrane in the NW part of the Archean Yilgarn Craton and the Palaeoproterozoic Glenburgh Terrane (Figure 2). The Narryer Terrane, which contains the oldest known rocks in Australia (c. 3730 Ma), was reworked by deformation and metamorphism in the late Archaean. It includes several groups of gneiss derived from early to late Archaean granites, and interleaved meta- sedimentary and mafic meta-igneous rocks.
During the Capricorn Orogeny, the north-eastern part of the Narryer Terrane, where the Project is partly located, was deformed, metamorphosed, and intruded by voluminous granite sheets and dykes. This part of the Narryer Terrane is referred to as the Yarlarweelor Gneiss Complex.
The Glenburgh Terrane comprises c.2540–2000 Ma gneissic granitic rocks and metasedimentary rocks that may in part be an exotic terrane incorporated into the Gascoyne Complex during the Palaeoproterozoic. The Glenburgh Terrane is intruded by large plutons of potassic and silicic granite, belonging to the 1830–1780 Ma Moorarie Supersuite.
Large tracts of the Project are covered by a considerable thickness of transported regolith, including broad alluvial sheet-wash and colluvial plains containing braided steams consisting of unconsolidated sand, silt and gravel.
Monazite [(REE)PO4], an important ore for thorium, lanthanum, and cerium, represents one of three primary exploration targets within the Project, is enriched within present day and previous, now-obscured, drainage channels. The mineral is ubiquitous in granitic and many metamorphic rocks, beach sand, and is a primary and hydrothermal mineral in carbonatite. The total REE2O3 contents within monazite range from 49.6 to 74.13 wt % and the average value is 64.31 wt %. Most monazite contains additional thorium, uranium, calcium, strontium, silica, and lead, and some also accommodate sulphur.
From 1995, exploration programs were completed by BHP, Astro Mining NL, and All Star Resources Plc. A summary of this work is detailed below.
Between 1985-1987, a comprehensive programme of stream sediment sampling, heavy mineral sampling and mineralogical analysis across the eastern portion of the Mt Clere Rare Earth Project, targeting Pb-Zn-Ag mineralisation similar to that found at Broken Hill.
Heavy mineral sampling was completed at the approximate density of 500 samples per 1,000km2. The sampling confirmed the presence of gahnite (a mineral associated with Pb-Zn-Ag mineralisation at Broken Hill) but failed to locate any base metal mineralisation.
The ample presence of monazite in pan concentrates, with grades exceeding 50%, was confirmed in greater than 20% of the 176 samples. BHP classified the samples as follows (WAMEX Report A30270):
A = Abundant = >50% of estimated relative abundance of grains C = Common = 30 – 50%
F = Frequent = 5 – 30%
R = Rare = <5%
The resulting abundances for monazite (n=176 samples) is:
Abundant = 21.4% Common = 26%
Thus 47.4% of the samples returned a relative abundance exceeding 30% monazite.
The anomalous samples have not been investigated further, nor has the REE distribution within the monazite been assessed. Given The samples also report varying levels of ilmenite and zircon.
Petrographic analysis of 20 samples sites across the Project area confirmed the following accessory occurrences, which are indicative of REE prospectivity:
Allanite, a sorosilicate group of minerals within the broader epidote group that contain a significant amount of rare-earth elements with cerium, lanthanum, neodymium or yttrium normally the dominate rare earth present. Allanite occurs mainly in metamorphosed clay- rich sediments and felsic igneous rocks.
Titanite, which is a calcium titanium nesosilicate mineral that commonly presents rare earth metals cerium and yttrium.
Astro Mining NL
Between 2005 and 2006, Astro Mining explored the western portion of the Mt Clere Rare Earth Project for diamonds. Nineteen discrete, primitive, alkaline lamprophyres were located during their search, which involved stream sediment sampling and geological surveys.
Though no micro-diamonds were recovered by Astro, grain counts of mineral species in selected samples of heavy mineral concentrates produced extraordinarily high monazite (up to 48%) and very high zircon (up to 60%), ilmenite (up to 29%) and leucoxene (up to 20%). The results independently validate the thorium and REE prospectivity latent in the Project (WAMEX report A58632).
Diamond exploration was unsuccessful for Astro. However, their work has proved very fertile for rare earth elements, niobium and thorium mineralisation. The company recognised lamprophyre rocks of a deep crustal origin within a highly complex area located at the edge of an Archaean craton. This supports the area as having the considerable potential for a suit of intrusive alkaline ultramafic rocks, including carbonatites which are known hosts for RRE.
All Star Minerals Plc
All Star collected two large samples of alluvium in 2006 to produce a heavy mineral concentrate. Each concentrate was sent for analysis and microscopic mineral examination at Genalysis Laboratory Services. The two samples respectively returned 3% and 2% monazite, as well as 1.4% zircon, 40% and 44% ilmenite, and 9.9% titanium. Rare earth elements, cerium and lanthanum, reported at 0.46% and to 0.25%, respectively.
Seventy-seven samples were collected at a maximum depth of 1.8 metres from auger drilling in 2007. Of the 77 auger regolith samples taken, 55 returned an encouraging grade of over 50 ppm cerium, 30 returned a grade of over 50 ppm lanthanum, and 17 returned a grade of over 200 ppm zircon. Thirty-three (33) samples graded over 30 ppm neodymium, with highs of 360 ppm, 103 ppm, 102 ppm, 95.9 ppm, 87.6 ppm, and 82.6 ppm. Whereas, sample EBA052 [506041 Z50E, 7184977 Z50N] recorded 320 ppm thorium, 660 ppm lanthanum, 37 ppm yttrium, 360 ppm neodymium, 112 ppm praseodymium, 43 ppm samarium. The results confirm the presence of monazite and other rare earths in the alluvium. Refer to Appendix 1 for the full results.
Consequently, the Company believes the Project area shows considerable prospectivity for three REE target styles:
Monazite sands in vast alluvial terraces
Chinese-type Ion Absorption clays in extensive laterite areas, and
Carbonatite dyke swarms
Monazite sands in vast alluvial terraces
The BHP and Astro pan concentrates bearing substantial abundances monazite lie within and are the likely cause of the unusually high thorium anomalies present in radiometric imagery (Figure 1). Many of the samples contained relative abundance mineral estimates exceeding 50% monazite, and many of these samples also contained other valuable heavy minerals, such as ilmenite (to 29%), leucoxene (to 20%) and zircon (to 60%). These minerals all concentrate within the Project’s area drainage networks.
The Company believes that simple screening followed by magnetic, gravity or density separation will recover the key target minerals, including monazite, xenotime, ilmenite, leucoxene and zircon.
Chinese-type Ion Absorption clays in extensive laterite areas
The areas covered by the Mt Clere Rare Earth Project include broad zones with high tenor Th radiometric anomalies. Many, but not all, are associated with concentrations of monazite sands in the drainage networks. Others, however, lie over deeply weathered terrain developed in the country rocks. Such occurrences may represent the primary sources for the monazite found within the drainage networks and may support the prospectivity for ion adsorption REE (Rare Earth Elements) clay-type deposits similar to those found in South China.
The supergene, ion-adsorption REE clay deposits are formed as a result of in-situ lateritic weathering of REE-rich host rocks, leading to the formation of aluminosilicate clays that are capable of adsorbing dissolved REE. Coincident areas between deeply weathered bedrock and high tenor radiometric thorium form a prime target for this style of REE deposits.
Ion-adsorption REE deposits have the benefit of easier mining and ore processing as they involve shallow, open pit mining and no milling.
Carbonatite dyke swarms
Astro Mining (WAMEX Report A58633) confirmed the presence of 19 discrete, primitive lamprophyres within the district. Their presence indicates the area is favourable for alkaline magmatism, which may include the presence of genetically-related REE-bearing carbonatites.
Approximately >50% of global rare earth element (REE) resources are hosted by carbonatite related deposits, of which monazite is one of the most important REE minerals. Monazite dominates more than 30 carbonatite-related REE deposits around the world.
Carbonatite type geochemical signatures are known in the Project area, and a carbonatite dyke swarm occurs 230km to the NW in the Gifford Creek-Yangibana area. The latter contains a resource of 21.67 Mt at 1.17% TREO (Hasting Technology Metals Ltd, ASX release 22nd November 2018).
While carbonatite is yet to be identified within the Project area, any carbonatite is likely obscured by the extensive regolith cover in the hinterland, and the target type remains largely unconsidered.
The Company believe’s the carbonatite-related rare earth potential at the project is significant.
Prior to grant of the exploration licence, the Company will complete the following:
Compilation of legacy data and reprocessing the existing geophysical datasets using modern approaches and enhancements;
Geological mapping of the various laterite/hard cap types to further understand controls on mineralisation and assist with ion-adsorption clay drill target generation;
Ground search for and sampling of alkaline ultramafic outcrops;
Non-ground disturbing activity’s including the collection of monazite samples to determine the relative thorium and rare earth contents with monazite grains.