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Rare earth element fluorocarbonate minerals from the Olympic Dam Cu-U-Au-Ag Deposit, South Australia

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Abstract
Olympic Dam is a world-class breccia-hosted iron-oxide copper-gold-uranium ore deposit located in the Gawler Craton, South Australia. It contains elevated concentrations of rare earth elements (REE) which occur as the REE minerals bastnäsite, synchysite, florencite, monazite, and xenotime. This is the first study to focus on the mineralogy and composition of the most abundant REE mineral at Olympic Dam, bastnäsite, and subordinate synchysite. The sample suite extends across the deposit and represents different sulfide mineralization styles (chalcopyrite-bornite and bornite-chalcocite) and breccias of various types, ranging from those dominated by clasts of granite, dykes, and hematite. The REE-fluorocarbonates (bastnäsite and synchysite) typically occur as fine-grained (2, which may also have been contributed by associated mafic-ultramafic magmatism. However, transport of REE by Cl-ligands is the most likely scenario. Stubby bastnäsite and synchysite may have formed earlier, coincident with hydrothermal alteration of granite releasing Ca from feldspars. Other categories of bastnäsite, notably those co-existing with sulfides, and reaching the top of the IOCG mineralization at Olympic Dam (chalcocite + bornite zone) are relatively younger. Such an interpretation is concordant with subtle changes in the REE patterns for the different categories. The common association of bastnäsite and fluorite throughout the deposit is typical of the hematite breccias and can be deposited from neutral, slightly acidic fluids (sericite stability) at T ≈ 300 °C.
Item Type: | Article |
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Authors/Creators: | Schmandt, DS and Cook, NJ and Ciobanu, CL and Ehrig, K and Wade, BP and Gilbert, S and Kamenetsky, VS |
Keywords: | Olympic Dam, bastnasite, synchysite, mineral compositions |
Journal or Publication Title: | Minerals |
Publisher: | M D P I AG |
ISSN: | 2075-163X |
DOI / ID Number: | https://doi.org/10.3390/min7100202 |
Copyright Information: | Copyright 2017 The AuthorsLicensed under Creative Commons Attribution 4.0 International (CC BY 4.0)https://creativecommons.org/licenses/by/4.0/ |
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