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Cummins Range Carbonatite
Western Australia, WA, Australia
Main commodities: REE

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The Cummins Range carbonatite rare earth element (REE) occurrence is located 130 km SSW of the town of Halls Creek, and is at the junction of the King Leopold and Halls Creek Mobile Zones, to the south-east of the stable Kimberley Block in northern Western Australia (#Location: 19° 17' 40"S, 127° 9' 45"E).

The carbonatite complex intrudes a suite of slate, phyllite and greywacke, correlated with the Archaean Halls Creek Group, while Lamboo Complex granite gneiss is also represented nearby.   The carbonatite is believed to be of Neoproterozoic age (905 ±2 Ma to 854 ± 12 Ma) and related to the Bow Hill lamprophyre dyke swarm in the east Kimberley (Andrew, 1990).

The complex is reflected by a major aeromagnetic anomaly, due to coarse magnetite within the carbonatite and finely disseminated magnetite within the pyroxenite (Andrew, 1990).

The Cummins Range complex covers a surface area of some 1.8 x 1.7 km, and comprises a composite sub-vertical to vertical stock composed of three generally concentric zones. The central plug is composed of calcite-dolomite and has a weathered capping of silicified, limonitic collapse breccia that is ~100 m thick (Andrew, 1990).

The central plug is surrounded by an inner zone of carbonate altered mica rich pyroxenite which is now mainly an amphibolite. This altered zone is intruded by numerous steep, up to 60 m thick, carbonatite veins with a cone-sheet/ring dyke form (Andrew, 1990). These veins contain variable proportions of fluorapatite-phlogopite-magnetite ±pyrochlore ±metasomatic Na-Ca amphiboles ± zircon. The phlogopite-diopside clinopyroxenite of these veins contains minor calzirtite that has been replaced in part by zirconolite, ilmenite and baddeleyite (Downes et al., 2012).

With the decrease in carbonatite alteration and veining outwards, the amphibolitised pyroxene grades into an outer zone of unaltered pyroxenite represening 60% of the complex (Andrew, 1990).

The concentric nature of the system is broken by a second plug of carbonated mica pyroxenite toward the eastern margin of the complex (Andrew, 1990).

The carbonatite includes both sovite (calcitic) and beforsite (dolomitic) carbonatite, although the later predominates. One end member contains abundant apatite with variable phlogopite, magnetite and clinopyroxene, and veins and vugs of pyrite, pyrrhotite and chalcopyrite with occassional barite and fluorite.   A supergene zone is developed in the weathered zone with all resistate minerals being upgraded through mechanical concentration of the primary magmatic-hydrothermal REE mineralisation. This cap, which is ~100 m thick, contains the bulk of the resource (Andrew, 1990).

Perovskite within the pyroxenite is interpreted to be primary on the basis of replacement textures comprising intergrowths of ilmenite, lucasite- (Ce), titanite and kassite. Trace Ce-allanite is also found in the pyroxenite. Low-Sr dolomite carbonatite and high-Sr (Sr ≥ 2500 ppm) calcite carbonatite phases are recognised within the central plug, whilst zones of vug development within the carbonatite coincide with the low-Sr dolomite carbonatite. This is interpreted to suggest possible hydrothermal alteration and replacement of calcite carbonatite with dolomite. Hydrothermal REE mineralisation resulted in Ce-monazite rimming and replacing primary fluorapatite; Ce-parisite and synchysite in veins and lining cavities in carbonatite; as well as minor Ce-nioboaeschynite and chevkinite, and Nd-fergusonite. Minor REE-bearing pyrochlore-group minerals are also widespread within the various phases of the carbonatite. The U, Ca and Ba content of pyrochlore in the primary carbonatite is variable and is altered to Sr-rich pyrochlore in the oxidised zone. Zircon may be an important host for Middle REE to Heavy REE whilst rare zircon megacrysts of up to ~1.5 cm in width are seen in the calcite carbonatite. Zircon is also found as a porphyroblast in strongly foliated carbonatite and as a metasomatic phase with complex growth textures. The main REE mineralisation event in the primary carbonatite has been interpreted to have been associated with the a late magmatic-hydrothermal phase of carbonatite emplacement, where REEs were mobilised from primary carbonates (Sr-bearing calcite) and fluorapatite to produce Ce-monazite and REE-fluorocarbonates (parisite-synchysite). This paragraph is drawn from Downes et al. (2012).

In the oxide capping, REEs are hosted by fluorapatite, Ce-monazite, Ce-bastnasite, crandallite-group minerals, and Y-churchite. Minor REEs are also found in iron oxides and pyrochlore-group minerals. Mechanical weathering and deflation of the primary carbonatite concentrated primary fluorapatite and Ce-monazite producing the oxidised zone ore body (Downes et al., 2012).

The inferred resource in 1990 was 3 to 4 Mt @ 2 to 4% Rare Earth Oxides in the top 80 m below surface.   REO grades include 50 to 100 ppm Eu2O3, comparable to the grades at Mountain Pass in California, USA (Andrew, 1990).

Kimberley Rare Earths (2012) quote an inferred resource to a depth of 100 m below surface, of:
    4.90 Mt @ 1.74% TREO, 11.2% P
2O5, 145 ppm U3O8, at a 1% TREO cut-off ; or
  10.76 Mt @ 1.18% TREO, 10.2% P
2O5, 100 ppm U3O8, 47 ppm Th, at a 0.5% TREO cut-off.

RareX Limited (2021) quote resource as follows:
  At a 0.5% TREO cut-off
    Indicated Mineral Resource - 11.1 Mt @ 1.34% TREO, 0.27% NdPr, 0.17% Nb
2O5, 830 ppm HREO;
    Inferred Mineral Resource - 7.7 Mt @ 0.88% TREO, 0.18% NdPr, 0.11% Nb
2O5, 540 ppm HREO;
    TOTAL Mineral Resource - 18.8 Mt @ 1.15% TREO, 0.23% NdPr, 0.14% Nb
2O5, 711 ppm HREO.
  At a 1.0% TREO cut-off
    Indicated Mineral Resource - 4.9 Mt @ 2.11% TREO, 0.41% NdPr, 0.23% Nb
2O5, 1150 ppm HREO;
    Inferred Mineral Resource - 1.6 Mt @ 1.60% TREO, 0.31% NdPr, 0.16% Nb
2O5, 800 ppm HREO;
    TOTAL Mineral Resource - 6.5 Mt @ 1.98% TREO, 0.38% NdPr, 0.21% Nb
2O5, 1060 ppm HREO.

Whilst the bulk of the resources detailed are within the oxidised cap, significant grades and thicknesses have also been intersected in the hypogene zone (RareX Limited (2021).

For detail consult the reference(s) listed below.

The most recent source geological information used to prepare this decription was dated: 2014.     Record last updated: 11/9/2021
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

Cummins Range Carbonatite

  References & Additional Information
   Selected References:
Andrew R L  1990 - Cummins Range Carbonatite: in Hughes F E (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne   Mono 14, v1 pp 711-713
Downes P J, Demeny A, Czuppon G, Jaques A L, Verrall M, Sweetapple M, Adams D, McNaughton N J, Gwalani L G and Griffin B J,  2014 - Stable H-C-O isotope and trace element geochemistry of the Cummins Range Carbonatite Complex, Kimberley region, Western Australia: implications for hydrothermal REE mineralization, carbonatite evolution and mantle source regions: in    Mineralium Deposita   v.49 pp 905-932
Downes, P.J., Sweetapple, M.T., Verrall, M., Adams, D.,McNaughton, N., Gwalani, L. and Griffin, B.,  2012 - Rare earth minerals of the Cummins Range Carbonatite Complex, Kimberley region, Western Australia: in    The 35th Annual Seminar of the Joint Mineralogical Societies of Australasia, 8 to 11 June, 2012,   Proceedings volume, pp. 17-18.
Jaireth, S., Hoatson, D. and Miezitis, Y.,   2014 - Geological setting and resources of the major rare-earth element deposits in Australia: in    Ore Geology Reviews   v.62 pp. 72-128.

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants:   i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and   ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.

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