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Published November 5, 2025 | Version Published
Journal Article Open

Elemental signatures of metamorphic, diagenetic, and pedogenic magnesites from Central Queensland, Australia

Creators

  • 1. ROR icon California Institute of Technology
  • 2. ROR icon University of California, Los Angeles
  • 3. ROR icon University of Queensland
  • 4. ROR icon Jet Propulsion Lab

Abstract

Magnesium carbonates record information on water-rock interactions during and after mineral precipitation. The Marlborough Terrane in central Queensland, Australia, contains magnesite-bearing serpentinite highlands surrounded by low-lying sedimentary basins that host authigenic magnesite (MgCO3). Open pit mines in both settings provide exposures of serpentinites (Gumigil) and Cenozoic sediments and overlying black soils (Yaamba) that host the magnesite and other authigenic phases. The Gumigil mine contains deeply weathered serpentinite hosting metamorphic magnesite veins that formed syn-tectonically; both serpentinite and magnesite are now partially dissolving, silicifying, and ferruginizing. Aqueous Mg2+ is being exported into the basins surrounding the serpentinite ridges. The Yaamba magnesite mine in the surrounding plains exposes diagenetic magnesite formation within unlithified alluvial sediments, where ascending magnesium-rich groundwaters replace arkosic sands and silts by magnesite cements, nodules, and pinnacles. Late-stage pedogenic processes at Gumigil and Yaamba drive retrograde transformation of magnesite into geochemically distinct exterior regions of second-generation cryptocrystalline magnesite recording interactions with Fe/Mn-oxides/hydroxides via cerium anomalies, yttrium anomalies and manganese concentrations in zoned magnesites from Yaamba. The complex history of mineral precipitation, dissolution, diagenetic replacement, and supergene alteration is recorded in the major, minor and trace element compositions of magnesites at each site. Serpentinite ridges and magnesite-bearing valley floors in Central Queensland provide a useful analog to the processes that might occur in the ultramafic highlands and carbonated lowlands at Jezero crater, Mars.

Copyright and License

© 2025 The Authors. Published by Elsevier B.V. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Acknowledgement

We thank QMag Pty. Limited and the Gumigil Chrysoprase Mine for sampling access. Peter Martin, Eva Scheller, Kenneth Williford, Kelsey Moore, and Eryn Eitel assisted sample collection in the field. This project benefited from the use of instrumentation made available by the Resnick Sustainability Institute's Water and Environment Lab at the California Institute of Technology, the Environmental Geochemistry Laboratory at the University of Queensland, the Centre for Microscopy and Microanalysis at the University of Queensland, and the Caltech Division of Geological and Planetary Science. This project was supported by Simons Foundation Project Award [668346] and the National Science Foundation Graduate Research Fellowship Grant [DGE-1745301] to Carl Swindle.

Funding

This project was supported by Simons Foundation Project Award [668346] and the National Science Foundation Graduate Research Fellowship Grant [DGE-1745301] to Carl Swindle.

Conflict of Interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
Carl Swindle reports financial support was provided by National Science Foundation. Kenneth A. Farley reports financial support was provided by Simons Foundation. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Supplemental Material

Supplementary material. Table S1 is a Microsoft Excel file that contains the major and trace element data for samples analyzed in this study. The Lab ID column is the laboratory identifier. The Samples column is the sample name. The SAMPLE TYPE contains the name of the mine (Gumigil or Yaamba) and the material type including magnesite (MAGNESITE), serpentinite (SERP), ferricrete (FERRICRETE), arkose (ARKOSE), and (iron)‑manganese-oxides (Mn-OXIDE). The Material type column contains a brief description of the hand sample or subsection of the hand sample from which the analyte was extracted. The Magnesite Genetic Interpretation column lists the genetic interpretation of the magnesite including Metamorphic, Supergene Alteration, Diagenetic, Pedogenic, and NA for non-magnesite samples. The Location column lists the mine name and pit in the mine from which the sample was collected. The Chemical Analysis tab contains the chemical analysis type including whole rock (Whole Rock ICP-OES and ICP-MS) or selective digestion (Selective Digestion ICP-MS). Concentrations data is reported in weight percents (wt%) in parts per billion (ppb). Elemental ratios and anomalies (Y* and Ce*) are calculated from chondrite normalized concentrations (CI Norm) from values reported by McDonough and Sun (1995).

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Additional details

Related works

Is supplemented by
Supplemental Material: https://ars.els-cdn.com/content/image/1-s2.0-S0009254125004589-mmc1.xlsx (URL)

Funding

Simons Foundation
668346
National Science Foundation Graduate Research Fellowship Program
DGE-1745301

Dates

Accepted
2025-09-20
Available
2025-09-26
Available online
Available
2025-10-02
Version of record

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Caltech groups
Division of Geological and Planetary Sciences (GPS)
Publication Status
Published