Numerical modeling of REE fractionation patterns in fluorapatite from the olympic dam deposit (South Australia)

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dc.contributor.authorKrneta, S.
dc.contributor.authorCiobanu, C.L.
dc.contributor.authorCook, N.J.
dc.contributor.authorEhrig, K.J.
dc.date.issued2018
dc.description.abstractTrace element signatures in apatite are used to study hydrothermal processes due to the ability of this mineral to chemically record and preserve the impact of individual hydrothermal events. Interpretation of rare earth element (REE)-signatures in hydrothermal apatite can be complex due to not only evolving fO2, fS2 and fluid composition, but also to variety of different REE-complexes (Cl-, F-, P-, SO4, CO3, oxide, OH− etc.) in hydrothermal fluid, and the significant differences in solubility and stability that these complexes exhibit. This contribution applies numerical modeling to evolving REE-signatures in apatite within the Olympic Dam iron-oxide-copper-gold deposit, South Australia with the aim of constraining fluid evolution. The REE-signatures of three unique types of apatite from hydrothermal assemblages that crystallized under partially constrained conditions have been numerically modeled, and the partitioning coefficients between apatite and fluid calculated in each case. Results of these calculations replicate the measured data well and show a transition from early light rare earth element (LREE)- to later middle rare earth element (MREE)-enriched apatite, which can be achieved by an evolution in the proportions of different REE-complexes. Modeling also efficiently explains the switch from REE-signatures with negative to positive Eu-anomalies. REE transport in hydrothermal fluids at Olympic Dam is attributed to REE–chloride complexes, thus explaining both the LREE-enriched character of the deposit and the relatively LREE-depleted nature of later generations of apatite. REE deposition may, however, have been induced by a weakening of REE–Cl activity and subsequent REE complexation with fluoride species. The conspicuous positive Eu-anomalies displayed by later apatite with are attributed to crystallization from high pH fluids characterized by the presence of Eu3+ species.
dc.description.statementofresponsibilitySasha Krneta, Cristiana L. Ciobanu, Nigel J. Cook and Kathy J. Ehrig
dc.identifier.citationMinerals, 2018; 8(8):342-1-342-21
dc.identifier.doi10.3390/min8080342
dc.identifier.issn2075-163X
dc.identifier.issn2075-163X
dc.identifier.orcidCook, N.J. [0000-0002-7470-3935]
dc.identifier.urihttp://hdl.handle.net/2440/117345
dc.language.isoen
dc.publisherMDPI
dc.rights© 2018 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/).
dc.source.urihttps://doi.org/10.3390/min8080342
dc.subjectApatite; numerical modeling; Olympic Dam; rare earth elements; ore genesis
dc.titleNumerical modeling of REE fractionation patterns in fluorapatite from the olympic dam deposit (South Australia)
dc.typeJournal article
pubs.publication-statusPublished

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