Please use this identifier to cite or link to this item: https://hdl.handle.net/2440/124577
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Type: Journal article
Title: A mineralisation age for the sediment-hosted blackbush uranium prospect, north-eastern eyre peninsula, South Australia
Author: Domnick, U.
Cook, N.J.
Ciobanu, C.L.
Wade, B.P.
Courtney-Davies, L.
Bluck, R.
Citation: Minerals, 2020; 10(2):1-19
Publisher: MDPI
Issue Date: 2020
ISSN: 2075-163X
Statement of
Responsibility: 
Urs Domnick, Nigel J. Cook, Cristiana L. Ciobanu, Benjamin P. Wade, Liam Courtney-Davies and Russel Bluck
Abstract: The Blackbush uranium prospect (~12,580 tonnes U at 85 ppm cut-o ) is located on the Eyre Peninsula of South Australia. Blackbush was discovered in 2007 and is currently the single example of sediment-hosted uranium mineralisation investigated in any detail in the Gawler Craton. Uranium is hosted within Eocene sandstones of the Kanaka Beds and, subordinately, within a massive saprolite derived from the subjacent Hiltaba-aged (~1585 Ma) granites, a liated with the Samphire Pluton. Uranium is mainly present as co nite in di erent lithologies, mineralisation styles and mineral associations. In the sandstone and saprolite, co nite occurs intergrown with framboidal Fe-sulphides and lignite, as well as coatings around, and filling fractures within, grains of quartz. Microprobe U–Pb dating of co nite hosted in sedimentary units yielded a narrow age range, with a weighted average of 16.98 0.16 Ma (343 individual analyses), strongly indicating a single co nite-forming event at that time. Co nite in subjacent saprolite generated a broader age range from 28 Ma to 20 Ma. Vein-hosted co nite yielded similar ages (from 12 to 25 Ma), albeit with a greater range. Uraninite in the vein is distinctly older (42 to 38 Ma). The 17 0.16 Ma age for sandstone-hosted mineralisation roughly coincides with tectonic movement as indicated by the presence of horst and graben structures in the Eocene sedimentary rocks hosting uranium mineralisation but not in stratigraphically younger sedimentary rocks. The new ages for hydrothermal minerals support a conceptual genetic model in which uranium was initially sourced from granite bedrock, then pre-concentrated into veins within that granite, and is subsequently dissolved and reprecipitated as co nite in younger sediments as a result of low-temperature hydrothermal activity associated with tectonic events during the Tertiary. The ages obtained here for uranium minerals within the di erent lithologies in the Blackbush prospect support a conceptual genetic model in which tectonic movement along the reactivated Roopena Fault, which triggered the flow of U-rich fluids into the cover sequence. The timing of mineralisation provides information that can help optimise exploration programs for analogous uranium resources within shallow buried sediments across the region. The model presented here can be predicted to apply to sediment-hosted U-mineralisation in cratons elsewhere.
Keywords: Uranium mineralisation; Eyre Peninsula; Blackbush uranium prospect; U–Pb microprobe geochronology; Kanaka Beds; coffinite
Rights: © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
DOI: 10.3390/min10020191
Grant ID: http://purl.org/au-research/grants/arc/IH130200033
Published version: http://dx.doi.org/10.3390/min10020191
Appears in Collections:Aurora harvest 4
Civil and Environmental Engineering publications

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