Drivers of critical metal enrichment in peralkaline magmas recorded by clinopyroxene zoning

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2025

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Simpson, B.
Ubide, T.
Spandler, C.

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Communications Earth & Environment, 2025; 6(1):89-1-89-9

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Brenainn Simpson, Teresa Ubide, Carl Spandler

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Highly sodic peralkaline magmas can reach hyper-enrichment in critical metals including rare earth elements (REE).Weexplore clinopyroxene zoning to track the evolution of peralkalinemagmas and the mechanisms that trigger critical metal mineralisation, focusing on the Mesozoic Benolong Volcanic Suite in eastern Australia, which includes a zirconium + hafnium + niobium + tantalum mineralised subvolcanic sill. Major and trace element analysis of clinopyroxene across the volcanic field tracks continuous magma differentiation from diopside-hedenbergite to aegirine, associated with progressive enrichment of rare metals. Crucially, aegirine in the mineralised trachyte becomes sectorzoned and depleted in critical metals, which instead partition into latest-stage eudialyte. Association with vesiculated portions of the sill suggests that sector zoning is the product of undercooling which may be driven by degassing. Because volatiles increase the solubility of critical metals in silicate magmas, we suggest retention of volatiles and dynamic crystallisation conditions drive enrichment of critical metals in the Toongi deposit. Our data show that pyroxene chemistry and zoning can help track fertility in critical metals in peralkaline magmas.

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© Crown 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/.

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