Authors / CoAuthors
Hohl, M. | Steadman, J.A. | Cloutier, J. | Barker, S.L.L. | Belousova, I. | Goemann, K. | Cooke, D.R.
Abstract
Hydrothermal magnetite from the Starra iron oxide‑copper gold (IOCG) deposit in northwest Queensland, Australia, records a gradual decrease in V, Ni, Cr, and Mn that correlates with the transition from early, amphibole-biotite-magnetite dominant alteration to late, chlorite-quartz-hematite-dominated alteration assemblages. The observed systematic change in multivariate elements in magnetite is interpreted to indicate an increase in fO2 during the main Cu(Au) mineralization. We suggest that variations in the V, Ni, and Cr contents of magnetite at Starra indicate either a primary magmatic fluid source or the leaching of mafic rocks by fluids during early albitization. Late silician magnetite contained in ankerite veins that crosscut the pre-existing alteration assemblages in the hanging wall to the Starra 222 ore body is likely the result of a second mineralization phase, which contributed additional metals to the Starra ore bodies. Existing data on magnetite chemistry from several IOA, IOCG, Fe, and Fe-W skarn deposits show that the ratio of V to Ga discriminates the various ore types effectively. Skarn deposits are separated from IOA and IOCG by lower concentrations of V, Ni, and Cr, suggesting a more primitive fluid source or the precipitation of magnetite at distinct physicochemical conditions than IOA and IOCG deposits. Magnetite from IOA deposits exhibits a consistently elevated V concentration whereas magnetite from Fe(–– W) skarn records an increase in V concentration with the evolution of the system. A pronounced decrease in the V contents of magnetite associated with Cu Au mineralization at Starra is interpreted as a change in redox conditions from reduced to oxidized at the time of mineralization. Such variations are also observed in other IOCG deposits. We propose that systematic decreases in V concentration in magnetite during the paragenetic evolution of the host mineral system is a diagnostic indicator for Cu(Au) mineralization in IOCG deposits, and as such, it may be used as a proxy for Cu-Au exploration, if the paragenetic context of magnetite is well constrained. <b>Citation:</b> Max Hohl, Jeffrey A. Steadman, Jonathan Cloutier, Shaun L.L. Barker, Ivan Belousov, Karsten Goemann, David R. Cooke, Trace element systematics of magnetite from the Starra iron oxide‑copper gold deposits reveals early fluid conditions characteristic for Cu mineralization, <i>Chemical Geology</i>, Volume 648, 2024, 121960, ISSN 0009-2541, https://doi.org/10.1016/j.chemgeo.2024.121960
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document
eCat Id
149303
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
Canberra
ACT
2601
Australia
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Keywords
- ( Project )
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- CODES
- ( Project )
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- University of Tasmania
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- Starra
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- iron oxide copper gold - IOGG
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- pyrite
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- mineral chemistry
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- sulfur isotope
- theme.ANZRC Fields of Research.rdf
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- Inorganic GeochemistryIsotope GeochemistryGEOLOGY
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- Published_External
Publication Date
2024-09-03T02:48:20
Creation Date
2024-03-02T09:00:00
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completed
Purpose
The study is part of Max Hohl PhD and focuses on the Starra IOCG deposits. It aims at identifying key proccesses that formed the deposits using pyrite mineral chemistry and isotopic signature.
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notPlanned
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geoscientificInformation
Series Information
Chemical Geology Volume 648, 20 March 2024 121960
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<div>Samples used in the study were collected with the approval of Chinova Resources. The data from this manuscript are from the CODES LA ablation facility and the S isotopes were collected at the Centre for Microscopy, Characterization and Analysis (CMCA) at the University of Western Australia.</div>
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[-21.1423, -18.0231, 138.7525, 141.8338]
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