Monazite, lanthanide-rich glasses, and other trace elements in copper smelter slags: constraints on critical metal behaviour in Si-Fe-rich melts
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Date
2025
Authors
Gezzaz, H.
Ciobanu, C.L.
Cook, N.J.
Ehrig, K.
Slattery, A.
Wade, B.
Gilbert, S.
Rodriguez, Y.T.C.
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Journal article
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Mineralogy and Petrology, 2025; 119(2):197-221
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Hassan Gezzaz, Cristiana L. Ciobanu, Nigel J. Cook, Kathy Ehrig, Ashley Slattery, Benjamin Wade, Sarah Gilbert, Yuri T. Campo Rodriguez
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Abstract
Furnace slags are potential new sources of critical metals. We undertook a micron- to nanoscale study that addresses speciation, distribution and associations of phases in air-cooled flash furnace (FF, oxidised) and electric furnace (EF, reduced) slags from the Olympic Dam mining-smelting-refinery operation. Results enable understanding of the behaviour and partitioning of critical metals between melt and cooling crystalline phases in a controlled smelter environment that mimics Fe-Si-rich systems in Nature. Melts at ~ 1300 °C result in slags that differ in the relative proportions of component phases. Both FF and EF slags comprise major magnetite and two, compositionally distinct Si-Fe-rich glasses (glass-1 and -2); fayalite is a main component of EF slag. Glass-1 is rich in REE + Y (4.5–5.4 wt%, Ce2O3 + La2O3) and contains dendritic monazite-(Ce). Glass-2 (~ 70 wt% SiO2) contains < 1 wt% Ce2O3 + La2O3. The EF slag reaction sequence is: magnetite → fayalite + glass-1 → monazite → glass-2. Immiscibility of REE-rich liquid from Si-Fe-rich melt is inferred from amorphous ‘monazite-like’ droplets. Chondrite-normalised fractionation patterns are defined by downwards-sloping LREE segments in both glasses. Partition coefficients are calculated for magnetite and fayalite relative to glasses. DREY for HREE exceeds those for LREE in all phases and fayalite has an order of magnetite higher DHREE than co-existing EF magnetite. Applying lattice strain models to experimental values show excellent fits for DHREE- model trends, even if lattice strain is not the sole factor controlling partitioning. Melt polymerisation, variable/unpredictable oxidation states, and constraints from specific crystallographic sites, also impact on observed trends. This study provides clues to element behaviour in metallurgical plants that can assist potential utilization of copper smelter slags to meet the demand for REE and other contained critical metals.
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Published online: 06 May 2025
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© The Author(s) 2025. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.