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Sedimentary manganese carbonate deposits as faithful proxies of ancient ocean redox fluctuations: Insights from the Permian Zunyi Mn deposits, South China.

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Title: Sedimentary manganese carbonate deposits as faithful proxies of ancient ocean redox fluctuations: Insights from the Permian Zunyi Mn deposits, South China.
Authors: Xu, Hai1,2,3, Gao, Junbo3,4, Yang, Ruidong3,4, Chen, Fangge5, Xu, Jinhong1,6, Wang, Li2, Yang, Chenchen2, Yin, Runsheng2 yinrunsheng@mail.gyig.ac.cn
Source: Geological Society of America Bulletin. Nov2025, Vol. 137 Issue 11/12, p5148-5162. 15p.
Subject Terms: *Paleoceanography, *Anoxic waters, *Minerals, *History of geology, *Ore deposits, *Oxidation-reduction reaction, *Diagenesis, *Submarine geology
Geographic Terms: Southeast China
Abstract: Sedimentary manganese (Mn) carbonate deposits, i.e., the land-based major Mn mineral resources on Earth, are of great scientific value for palaeoceanographic research because Mn is a redox-sensitive metal whose deposition is restricted by oceanic redox conditions. The genesis of Mn carbonates remains controversial and the palaeoceanographic implication behind sedimentary Mn carbonate deposits is unclear. Here, we investigate the precipitation mechanisms, spatiotemporal redox, and hydrographic dynamics of the Middle Permian Zunyi Mn carbonate deposits in South China. The preserved original Fe-Mn oxide residues within Mn carbonate nodules, coupled negative δ98MoNIST+0.25 values (mean: −1.59‰), negative δ13Ccarbonate values (mean: −7.68‰), and variable Ce anomalies (0.21–1.71), collectively support that Mn(II) carbonates were formed via the diagenetic reduction of original Mn(III/IV) oxides. Multiple lines of evidence (e.g., lithofacies, authigenic Mo and U enrichments, Ce anomalies, δ34Ssulfide, and δ98MoNIST+0.25) indicate that the deep-waters in the Qianzhong rift basin rapidly shifted from euxinic-anoxic to suboxic-oxic conditions during Mn deposition. This shift was driven by the rapid shallowing and exposure of the basin induced by continuous crustal uplift and global regression. These insights support an "oxidation expansion model" for the genesis of the Zunyi Mn deposits, which involves the downward expansion of the redoxcline triggering swift oxidation of anoxic deep waters and in situ precipitation of Mn(III/IV) oxides, and subsequently transforming to Mn(II) carbonates via diagenetic reduction. This study concludes that ancient Mn carbonate deposits are reliable proxies for paleoceanic redox fluctuations, and an overview of Mn carbonate deposits in the broad context of geological history supports their close genetic connection with oceanic redox perturbations. [ABSTRACT FROM AUTHOR]
Database: Energy & Power Source
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  Label: Title
  Group: Ti
  Data: Sedimentary manganese carbonate deposits as faithful proxies of ancient ocean redox fluctuations: Insights from the Permian Zunyi Mn deposits, South China.
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  Data: <searchLink fieldCode="AR" term="%22Xu%2C+Hai%22">Xu, Hai</searchLink><relatesTo>1,2,3</relatesTo><br /><searchLink fieldCode="AR" term="%22Gao%2C+Junbo%22">Gao, Junbo</searchLink><relatesTo>3,4</relatesTo><br /><searchLink fieldCode="AR" term="%22Yang%2C+Ruidong%22">Yang, Ruidong</searchLink><relatesTo>3,4</relatesTo><br /><searchLink fieldCode="AR" term="%22Chen%2C+Fangge%22">Chen, Fangge</searchLink><relatesTo>5</relatesTo><br /><searchLink fieldCode="AR" term="%22Xu%2C+Jinhong%22">Xu, Jinhong</searchLink><relatesTo>1,6</relatesTo><br /><searchLink fieldCode="AR" term="%22Wang%2C+Li%22">Wang, Li</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Yang%2C+Chenchen%22">Yang, Chenchen</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Yin%2C+Runsheng%22">Yin, Runsheng</searchLink><relatesTo>2</relatesTo><i> yinrunsheng@mail.gyig.ac.cn</i>
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  Data: <searchLink fieldCode="JN" term="%22Geological+Society+of+America+Bulletin%22">Geological Society of America Bulletin</searchLink>. Nov2025, Vol. 137 Issue 11/12, p5148-5162. 15p.
– Name: Subject
  Label: Subject Terms
  Group: Su
  Data: *<searchLink fieldCode="DE" term="%22Paleoceanography%22">Paleoceanography</searchLink><br />*<searchLink fieldCode="DE" term="%22Anoxic+waters%22">Anoxic waters</searchLink><br />*<searchLink fieldCode="DE" term="%22Minerals%22">Minerals</searchLink><br />*<searchLink fieldCode="DE" term="%22History+of+geology%22">History of geology</searchLink><br />*<searchLink fieldCode="DE" term="%22Ore+deposits%22">Ore deposits</searchLink><br />*<searchLink fieldCode="DE" term="%22Oxidation-reduction+reaction%22">Oxidation-reduction reaction</searchLink><br />*<searchLink fieldCode="DE" term="%22Diagenesis%22">Diagenesis</searchLink><br />*<searchLink fieldCode="DE" term="%22Submarine+geology%22">Submarine geology</searchLink>
– Name: SubjectGeographic
  Label: Geographic Terms
  Group: Su
  Data: <searchLink fieldCode="DE" term="%22Southeast+China%22">Southeast China</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Sedimentary manganese (Mn) carbonate deposits, i.e., the land-based major Mn mineral resources on Earth, are of great scientific value for palaeoceanographic research because Mn is a redox-sensitive metal whose deposition is restricted by oceanic redox conditions. The genesis of Mn carbonates remains controversial and the palaeoceanographic implication behind sedimentary Mn carbonate deposits is unclear. Here, we investigate the precipitation mechanisms, spatiotemporal redox, and hydrographic dynamics of the Middle Permian Zunyi Mn carbonate deposits in South China. The preserved original Fe-Mn oxide residues within Mn carbonate nodules, coupled negative δ98MoNIST+0.25 values (mean: −1.59‰), negative δ13Ccarbonate values (mean: −7.68‰), and variable Ce anomalies (0.21–1.71), collectively support that Mn(II) carbonates were formed via the diagenetic reduction of original Mn(III/IV) oxides. Multiple lines of evidence (e.g., lithofacies, authigenic Mo and U enrichments, Ce anomalies, δ34Ssulfide, and δ98MoNIST+0.25) indicate that the deep-waters in the Qianzhong rift basin rapidly shifted from euxinic-anoxic to suboxic-oxic conditions during Mn deposition. This shift was driven by the rapid shallowing and exposure of the basin induced by continuous crustal uplift and global regression. These insights support an "oxidation expansion model" for the genesis of the Zunyi Mn deposits, which involves the downward expansion of the redoxcline triggering swift oxidation of anoxic deep waters and in situ precipitation of Mn(III/IV) oxides, and subsequently transforming to Mn(II) carbonates via diagenetic reduction. This study concludes that ancient Mn carbonate deposits are reliable proxies for paleoceanic redox fluctuations, and an overview of Mn carbonate deposits in the broad context of geological history supports their close genetic connection with oceanic redox perturbations. [ABSTRACT FROM AUTHOR]
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RecordInfo BibRecord:
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      – Type: doi
        Value: 10.1130/B38103.1
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      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 15
        StartPage: 5148
    Subjects:
      – SubjectFull: Paleoceanography
        Type: general
      – SubjectFull: Anoxic waters
        Type: general
      – SubjectFull: Minerals
        Type: general
      – SubjectFull: History of geology
        Type: general
      – SubjectFull: Ore deposits
        Type: general
      – SubjectFull: Oxidation-reduction reaction
        Type: general
      – SubjectFull: Diagenesis
        Type: general
      – SubjectFull: Submarine geology
        Type: general
      – SubjectFull: Southeast China
        Type: general
    Titles:
      – TitleFull: Sedimentary manganese carbonate deposits as faithful proxies of ancient ocean redox fluctuations: Insights from the Permian Zunyi Mn deposits, South China.
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            NameFull: Xu, Hai
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            NameFull: Chen, Fangge
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            – D: 01
              M: 11
              Text: Nov2025
              Type: published
              Y: 2025
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