Dolocrete blanket over Mt Weld carbonatite (Western Australia) - A geochemical and mineralogical window to REE super-resource

Anderson M. Santos; Artur P. Deditius; Hans Oskierski; Arthur O. Vicentini; Malcolm P. Roberts; Ganesh Bhat; Denis Fougerouse

doi:10.1016/j.chemgeo.2026.123327

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Dolocrete blanket over Mt Weld carbonatite (Western Australia) - A geochemical and mineralogical window to REE super-resource

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Dolocrete blanket over Mt Weld carbonatite (Western Australia) - A geochemical and mineralogical window to REE super-resource

Anderson M. Santos, Artur P. Deditius, Hans Oskierski, Arthur O. Vicentini, Malcolm P. Roberts, Ganesh Bhat and Denis Fougerouse

Chemical geology, Vol.707, 123327

2026

DOI: https://doi.org/10.1016/j.chemgeo.2026.123327

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Abstract

Dolomite

REE-phosphates

Nb-goethite

Pedogenesis

Dolocrete

Carbonatite

REE-hosting regolith

Mt Weld

The geochemistry and mineralogy of REE and Nb were examined in lens-shaped dolocrete covering the central part of the (REE, Nb)-rich regolith derived from the Mount Weld carbonatite, Western Australia. Dolocrete was divided into three distinct units: (a) Upper White Dolocrete (UWD), comprising dolomite interwoven by palygorskite and traces of quartz, florencite-Ce, Ti-oxides, monazite-Ce; (b) Middle Pisolite Dolocrete (MPD) containing dolomite matrix with nodules of Nb-goethite, allogenic quartz, monazite-Ce, florencite-Ce, and cerianite; (c) Basal Breccia Dolocrete (BBD) comprising massive dolomite hosting monazite-Ce, florencite-Ce, and ironstone clasts containing Nb-goethite, Nb-ilmenite, Nb-rutile, quartz, baddeleyite, and zircon. The whole-rock analysis revealed an increase in (La/Yb)N with depth from UWD at 74, 247 in MPD, to 723 in BBD. The concentrations of REE in dolomite (Ca/Mg=1–1.2) increased from 66 ppm (median) in UWD, 281 ppm in MPD, to 347 ppm in BBD. Niobium-bearing ilmenite was altered to Nb-leucoxene (max. 18 wt.% Nb2O5). Incorporation of Nb into goethite (0.1–1.4 wt.%) and the absence of pyrochlore suggest Nb migration during the dolocrete formation. Stable isotope values (δ18OVPDB = −2.9‰ – −0.6‰, δ13CVPDB = −6.7‰ – −5.9‰) support a sedimentary origin of dolomite formed in saline groundwaters. A fluctuating water table in a semi-arid environment promoted dissolution and reprecipitation of REE-enriched dolomite with Mg most likely derived from carbonatite. These results reveal a complex evolution of REE and Nb during the weathering of metal-enriched regolith, underscoring the importance of dolocrete as a geochemical archive and a tool for exploration targeting ore deposits of critical minerals.

Details

Title: Dolocrete blanket over Mt Weld carbonatite (Western Australia) - A geochemical and mineralogical window to REE super-resource
Authors/Creators: Anderson M. Santos - School of Mathematics, Statistics, Chemistry and Physics, Murdoch University, Murdoch 6150, Western Australia, Australia
Artur P. Deditius - Murdoch University
Hans Oskierski - Murdoch University
Arthur O. Vicentini - Curtin University
Malcolm P. Roberts - Centre for Microscopy, Characterisation, and Analysis (CMCA), University of Western Australia, Crawley 6009, Western Australia, Australia
Ganesh Bhat - Lynas Rare Earths Ltd – Level 4, 1 Howard Street, Perth 6000, Western Australia, Australia
Denis Fougerouse - Curtin University
Publication Details: Chemical geology, Vol.707, 123327
Publisher: Elsevier B.V.
Number of pages: 21
Identifiers: 991005868907707891
Murdoch Affiliation: School of Mathematics, Statistics, Chemistry and Physics; Centre for Water, Energy and Waste
Language: English
Resource Type: Journal article

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