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Cited by 537Paleontology and Stratigraphy of FossilsGeochemistry and Elemental AnalysisGeological and Geochemical Analysis

Iron formations: A global record of Neoarchaean to Palaeoproterozoic environmental history

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Konhauser, K.O., Planavsky, N.J., Hardisty, D.S., Robbins, L.J., Warchola, T.J., Haugaard, R., Lalonde, S.V., Partin, C.A. +5 more·2017·Earth-Science Reviews
DOI 10.1016/j.earscirev.2017.06.012
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TL;DR

This review synthesizes the global Neoarchaean–Palaeoproterozoic iron formation record and argues that IF deposition was driven by hydrothermal Fe(II) supply combined with microbial Fe(II) oxidation (photoferrotrophy and/or oxygenic photosynthesis) and diagenetic microbial Fe(III) reduction. It uses IF mineralogy, geochemistry, and isotopes to track evolving seawater redox and atmospheric oxygenation from before the GOE through the ca. 1.88 Ga IF resurgence.

Key findings

  • IFs are iron-rich (15–40 wt.% Fe) and siliceous (40–60 wt.% SiO₂) chemical sedimentary rocks, mostly deposited between 2.80 and 1.85 Ga; they have an average Fe oxidation state of Fe²·⁴⁺, and the largest Superior-type IFs contain over 10¹⁴ tons of iron and can extend over 100,000 km².
  • Microbial Fe cycling is central: photoferrotrophy and/or cyanobacterial O₂ likely oxidized Fe(II), while dissimilatory iron reduction (DIR) explains low organic carbon contents (<0.5 wt.%) and Fe(II)-bearing minerals; estimated initial organic carbon is ~4.70 wt.% for oxide-facies IF (1.28 wt.% from C isotopes plus 3.42 wt.% from magnetite Fe(II)) and ~3.24 wt.% for siderite-facies IF.
  • Hydrothermal Fe sources are supported by REE+Y patterns (positive Eu anomalies, Y/Ho up to 90, La anomalies of 1.32–1.80 in pure IF) and Nd isotopes, but continental/benthic iron shuttle contributions are also indicated by δ⁵⁶Fe and εNd(t) mixing.
  • Redox evolution: pre-GOE IFs lack negative Ce anomalies and show light REE depletion, suggesting anoxic water and no discrete redoxcline; late Palaeoproterozoic ca. 1.88 Ga IFs show variable Pr/Yb(SN) and Y/Ho, indicating redox-stratified basins. Photoferrotroph layer modeling requires 17.6 m thickness for diffusive Fe(II) oxidation, and 34 m or >100 m for upwelling at 0.5 and 5 m/day, respectively, at 0.1 mM Fe(II) and an oxidation rate of 1.4 × 10⁻⁵ M/day.

Methods

  • Review and synthesis of the global IF record, updating Bekker et al. (2010, 2014), integrating sedimentology, petrography, geochronology, and geochemical/isotopic datasets (Fe, C, O, Si, Nd, REE+Y, Cr, U, Mo, Cu) from Archaean–Palaeoproterozoic IFs and associated shales/carbonates.
  • Includes new calculations: mass-balance/diagenetic modeling of pore-water DIC and carbonate δ¹³C, and photoferrotroph layer-thickness calculations adding advection to the Kappler et al. (2005) eddy-diffusion model.
  • No new sample collection is described; data are compiled from literature and previously published datasets.

Limitations

  • The paper states that the dominant Fe(II) oxidation mechanism remains uncertain; primary Fe mineralogy is debated (Fe(III)-oxyhydroxide/Fe(III)-Si gel versus greenalite/green-rust); post-depositional REE+Y mobility and metamorphic/supergene alteration can affect signals; and some Brockman δ⁵⁶Fe–εNd(t) interpretations differ among co-authors.
  • The paper states model limitations: photoferrotroph calculations depend on assumed Fe(II) oxidation rates, upwelling rates, and transport; the DIC model ignores carbonate precipitation/dissolution and a dynamic DIC reservoir; and many IFs remain poorly studied or dated (e.g., Weeli Wolli, Boolgeeda, mid-Proterozoic IFs).
  • Evident from the text: the review relies on literature data with uneven geographic and stratigraphic coverage, and several key questions—timing of cyanobacteria/photoferrotrophs, cause of the Proterozoic IF gap, and nutrient limitation—remain unresolved.

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Integrity signals

Registry

Crossref · 10.1016/j.earscirev.2017.06.012

Cites

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Statistics

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Claims the paper makes

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  • Findingcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    These REE+Y patterns are typically mimicked in the REE+Y patterns of post-Archaean iron formations.

    “These patterns are typically mimicked in the REE+Y patterns of post-Archaean IF (Laajoki, 1975; Fryer, 1977a, b; Graf, 1978; Barrett et al., 1988; Klein and Beukes, 1989).”
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  • Findingcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Even in the modern ocean, particulate and dissolved iron can be transported more than 2000 km from the ridge axis in seafloor-hydrothermal settings.

    “it has been demonstrated that, even in the modern ocean, particulate and dissolved iron can be transported more than 2000 km from the ridge axis in seafloorhydrothermal settings (Fitzsimmons et al., 2017)”
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  • Findingcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Modern hydrothermal systems may contribute up to 75% of dissolved iron to the iron budget in the deep oceans.

    “the recognition that even modern hydrothermal systems may contribute up to 75% of dissolved iron to the iron budget in the deep oceans (German et al., 2010; Carazzo et al., 2013; German and Seyfried, 2014)”
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  • Findingcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    The carbonate REE+Y patterns of the ca. 2.47 Ga Kuruman and Griquatown iron formations seem to mimic that of modern seawater even closer than do bulk-rock patterns.

    “The carbonate REE+Y patterns seem to mimic that of modern seawater even closer than do bulk-rock patterns.”
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  • Findingcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Recent in-situ and fraction-specific REE+Y trends for the ca. 2.47 Ga Kuruman and Griquatown iron formations show a marked difference in carbonate versus oxide mineral-hosted REE+Y patterns.

    “Recent in-situ and fraction-specific REE+Y trends for the ca. 2.47 Ga Kuruman and Griquatown IFs show a marked difference in carbonate versus oxide mineral-hosted REE+Y patterns (Oonk, 2017).”
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    Findingcitation
    § 1. Introduction

    The largest Superior-type iron formations contain over 10^14 tons of iron.

    “the largest Superior-type IFs contain over 10 14 tons of iron (Isley, 1995)”
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    Findingcitation
    § 1. Introduction

    Granular iron formations first appear in the rock record at ca. 2.90 Ga, reach their acme at ca. 1.88 Ga, and are then replaced by ironstones in the Phanerozoic record after ca. 543 Ma.

    “GIF first appear in the rock record at ca. 2.90 Ga (Siahi et al., 2017), reach their acme at ca. 1.88 Ga, and are then replaced by ironstones in the Phanerozoic record (after ca. 543 Ma) (Bekker et al., 2014).”
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    Findingcitation
    § 1. Introduction

    The presence of both ferric and ferrous minerals gives iron formations an average oxidation state of Fe 2.4+.

    “The presence of both ferric and ferrous minerals gives IFs an average oxidation state of Fe 2.4+ (Klein and Beukes, 1992).”
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    Findingnone given
    § 1. Introduction

    Most banded iron formations are commonly either overlain or underlain by organic matter-rich and sulfidic shales, and in some cases are interstratified with them.

    “Most BIF commonly are either overlain or underlain by organic matter-rich and sulfidic shales, and, in some cases, are interstratified with them.”
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    Findingcitation
    § 1. Introduction

    Superior-type iron formations can be very laterally extensive, with original aerial extents estimated in some cases to be over 100,000 km2.

    “Superior-type IFs can be very laterally extensive, with original aerial extents estimated in some cases to be over 100,000 km 2 (Isley, 1995; Bekker et al., 2010).”
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    Findingcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Modern seawater generally displays heavy REE (HREE) enrichments relative to light REE (LREE), positive La, Gd, and Y anomalies, and strong negative Ce anomalies when normalised to shales (PAAS).

    “Modern seawater generally displays heavy REE (HREE) enrichments relative to light REE (LREE), as well as positive La, Gd, and Y anomalies, and strong negative Ce anomalies when normalised to shales (e.g., post-Archaean average shale - PAAS) (e.g., Elderfield and Greaves, 1982; Taylor and McLennan, 1985; De Baar et al., 1985; Derry and Jacobsen, 1990; Bau et al., 1995; Alibo and Nozaki, 1999; Bolha”
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    Findingcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Iron formations older than 2.5 Ga display positive La, Gd, and Y anomalies as well, but lack regular negative Ce anomalies and instead contain large positive Eu anomalies.

    “Iron formations older than 2.5 Ga display positive La, Gd, and Y anomalies as well, but lack regular negative Ce anomalies and instead contain large positive Eu anomalies (e.g., Alexander et al., 2008).”
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    Findingcitation
    § 1. Introduction

    Modern seawater typically has iron concentrations in the range of 0.05 to 2.0 nM.

    “By contrast, modern seawater typically has iron concentrations in the range of 0.05 to 2.0 nM (de Baar and de Jong, 2001).”
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    Findingcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    The oxide fraction of the ca. 2.47 Ga Kuruman and Griquatown iron formations is the most depleted in REE+Y and has a slight MREE enrichment.

    “The oxide fraction is the most depleted in REE+Y and has a slight MREE enrichment (Oonk, 2017), which has been described from modern oxygen-limited ferrous environments (e.g., Haley et al., 2004).”
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    Findingcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Detailed studies of iron formations in the Hamersley Province suggested that the amount of iron deposited was on the order of 1 x 10^13 g/yr, requiring rivers the size of the modern Amazon to transport orders of magnitude more iron than they do today.

    “However, detailed studies of IF that followed in the Hamersley Province, Western Australia, suggested that the amount of iron deposited was on the order of 1 x 10 13 g/yr (Trendall and Blockley, 1970), requiring rivers the size of the modern Amazon to transport orders of magnitude more iron than they do today.”
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    Findingcitation
    § 1. Introduction

    The Archaean ocean had significantly elevated concentrations of dissolved silica, at least as high as saturation with cristobalite (0.67 mM at 40°C in seawater), between 0.5 and 1.5 mM for Fe(III)-Si gels, or as high as 2.20 mM for amorphous silica.

    “Similar to Fe(II), the Archaean ocean had significantly elevated concentrations of dissolved silica, at least as high as at saturation with cristobalite (0.67 mM at 40 o C in seawater), between 0.5 and 1.5 mM for Fe(III)-Si gels, depending on the Fe/Si ratio, or as high as 2.20 mM for amorphous silica (Siever, 1992; Maliva et al., 2005; Konhauser et al., 2007a; Zheng et al., 2016).”
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    Findingcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    The concentration of dissolved Fe(II) effused from some modern deep-sea vents is as high as 25 mM/kg; a few in arc- and back-arc settings have as much as 2500 mM.

    “Indeed, the concentration of dissolved Fe(II) effused from some modern deep-sea vents is as high as 25 mM/kg; a few, in arc- and back-arc settings have as much as 2500 mM (German and Von Damm, 2003)”
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    Findingcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    La anomalies are strongly expressed in pure iron formations (LaSN/LaSN* ratios between 1.32 and 1.80), whereas they are small or absent in impure iron formations (between 0.85 and 1.52).

    “Similarly, Viehmann et al. (2015) noted the depression of the La anomaly in IF with increased detrital contamination; La anomalies are strongly expressed in pure IF (LaSN/LaSN * ratios between 1.32 and 1.80), whereas they are small or absent in impure IF (between 0.85 and 1.52).”
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    Findingcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Aqueous fluids and their precipitates display Y/Ho ratios significantly higher than the molar ratio of 52 shown by common igneous rocks and epiclastic sediments, reaching molar ratios up to 90.

    “Aqueous fluids and their precipitates display Y/Ho ratios significantly higher than the molar ratio of 52 shown by common igneous rocks and epiclastic sediments (Bau, 1996, and references therein), reaching molar ratios up to 90 (Zhang et al., 1994; Bau et al., 1997; Nozaki et al., 1997).”
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    Findingcitation
    § 2.6 Available reductants and diagenesis of iron formations

    Using C isotope data, CO2 content, and Fe(II) and Fe(III) data from Beukes et al. (1990), Beukes and Klein (1990), and Kaufman (1996), the average initial Corg based on C isotope composition is 1.28 wt.% for oxide-facies IF and 3.24 wt.% for siderite-facies IF.

    “Using C isotope data, CO2 content, and Fe(II) and Fe(III) data from Beukes et al. (1990), Beukes and Klein (1990), and Kaufman (1996), the average initial Corg based on C isotope composition is 1.28 wt.% for oxidefacies IF and 3.24 wt. % for siderite-facies IF.”
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    Findingown data
    § 2.6 Available reductants and diagenesis of iron formations

    The δ56Fe values for coexisting oxides and carbonates, from the micron scale to bulk-sample analysis, scatter closely about a 1:1 line, with some samples trending toward, but not reaching, Fe isotope equilibrium.

    “the δ 56 Fe values for coexisting oxides and carbonates, from the micron scale to bulk-sample analysis of gram-size quantities, show that Fe isotope compositions scatter closely about a 1:1 line, with some samples trending toward, but not reaching, Fe isotope equilibrium”
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    Findingcitation
    § 2.7 Iron formations as tracers of seawater redox

    In the pre-GOE BIFs of the Transvaal Supergroup, Mn is only present in its divalent form in carbonate minerals and its concentration increases significantly stratigraphically upwards from the Kuruman to the Griquatown and Koegas IFs.

    “In the pre-GOE BIFs of the Transvaal Supergroup, Mn is only present in its divalent form in carbonate minerals and its concentration increases significantly stratigraphically upwards from the Kuruman to the Griquatown and Koegas IFs (Kurzweil et al., 2016; Oonk, 2017)”
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    Findingcitation
    § 2.6 Available reductants and diagenesis of iron formations

    The mineral-fluid fractionation-specific δ56Fe values of Transvaal BIF samples indicate a similar, consistently lighter source for carbonate- and silicate-bound Fe, whereas oxide-bound Fe tends to have more positive δ56Fe values.

    “The mineral-fluid fractionation-specific δ 56 Fe values of these samples indicate a similar, consistently lighter, source for carbonate and silicate bound-Fe, whereas the oxide-bound Fe tends to have more positive δ 56 Fe values”
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    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    The Marra Mamba IF carries a pronounced positive Eu anomaly, suggesting a strong hydrothermal imprint on the REE systematics during its deposition.

    “The Marra Mamba IF carries a pronounced positive Eu anomaly (Alibert and McCulloch, 1993), suggesting a strong hydrothermal imprint on the REE systematics during its deposition”
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    Findingnone given
    § 3.1 Iron formations deposited before the GOE

    Iron formations deposited between 2.60 and 2.45 Ga are the most laterally extensive and economically valuable of any in Earth history.

    “Iron formations deposited between 2.60 and 2.45 Ga are the most laterally extensive and economically valuable of any in Earth history.”
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    Findingcitation
    § 2.7 Iron formations as tracers of seawater redox

    Several studies have reported cases of Ce anomalies in Archaean IF, but many of these cases can be linked to analytical artefacts or the analysis of samples that have experienced supergene alteration.

    “Several studies have reported cases of Ce anomalies in Archaean IF (e.g., Kato et al., 2006), but many of these cases can be linked to analytical artefacts or the analysis of samples that have experienced supergene alteration”
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    Findingnone given
    § 2.7 Iron formations as tracers of seawater redox

    There is no conclusive evidence in the Transvaal IF for either the primary oxidative mechanism for episodic Mn sequestration (aerobic versus photoferrotrophic), nor for the relative role of Mn(II) incorporation into carbonates directly as Mn(II) from porefluid or indirectly through diagenetic bacterial reduction of Mn(IV) oxyhydroxides.

    “at present, there is no conclusive evidence in the Transvaal IF for either the primary oxidative mechanism for episodic Mn sequestration (i.e., aerobic versus photoferrotrophic), nor for the relative role of Mn(II) incorporation into carbonates directly as Mn(II) from porefluid or indirectly through diagenetic bacterial reduction of Mn(IV) oxyhydroxides”
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    Findingreasoning
    § 2.7 Iron formations as tracers of seawater redox

    Many IFs contain low concentrations of crustal-sourced elements such as Al, Ti, Zr, Th, Hf, and Sc, implying an authigenic origin and preservation of geochemical signatures uncontaminated by continental detritus.

    “many IFs contain low concentrations of crustal-sourced elements, such as Al, Ti, Zr, Th, Hf, and Sc, implying an authigenic origin and the preservation of geochemical signatures that are uncontaminated by continental detritus”
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    Findingcitation
    § 2.7 Iron formations as tracers of seawater redox

    In many Archaean and early Palaeoproterozoic IFs there are no Ce anomalies, and thus no deviation from trivalent Ce behaviour.

    “In many Archaean and early Palaeoproterozoic IFs there are no Ce anomalies (Planavsky et al., 2010a), and thus no deviation from trivalent Ce behaviour”
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    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    The Marra Mamba IF was deposited in a deep-water basinal setting adjacent to a passive margin during the sea-level highstand of the Marra Mamba basin, and has an average outcrop thickness of about 210 m.

    “It was deposited in a deep-water basinal setting adjacent to a passive margin during the sea-level highstand of the Marra Mamba basin, and has an average outcrop thickness of about 210 m”
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    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    The Marra Mamba IF is dominated by magnetite, ankerite, and fibrous silicate, which suggests excess organic carbon was present during diagenesis.

    “the Marra Mamba IF is dominated by magnetite, ankerite, and fibrous silicate (Baur et al., 1985), which suggests excess organic carbon was present during diagenesis”
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    Findingnone given
    § 3.1 Iron formations deposited before the GOE

    A lack of geochemical data is apparent for the Boolgeeda Iron Formation, which was deposited at ~2.45 Ga and represents the terminal IF deposit in the Hamersley Basin.

    “A lack of geochemical data is also apparent for the Boolgeeda Iron Formation, which was deposited at ~2.45 Ga and represents the terminal IF deposit in the Hamersley Basin.”
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    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    The Dales Gorge Member lacks a true negative Ce anomaly, suggesting low-oxygen conditions at the time of deposition.

    “the Dales Gorge Member lacks a true negative Ce anomaly, suggesting low-oxygen conditions at the time of deposition”
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    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    The Weeli Wolli Formation displays a marked increase in Cr concentrations, interpreted by Konhauser et al. (2011) as a remnant signature of bacterial pyrite oxidation and associated acid rock drainage.

    “The Weeli Wolli Formation displays a marked increase in Cr concentrations, interpreted by Konhauser et al. (2011) as a remnant signature of bacterial pyrite oxidation and associated acid rock drainage.”
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    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    The Dales Gorge Member displays typical seawater REE+Y patterns, including low Pr/YbSN (0.08-0.3), low Sm/YbSN (0.1-0.4), positive La anomalies, positive Eu anomalies, and superchondritic Y/Ho ratios.

    “Typical seawater REE+Y patterns are displayed by the Dales Gorge Member, including low Pr/YbSN (0.08-0.3), low Sm/YbSN (0.1-0.4), positive La anomalies, positive Eu anomalies, and superchondritic Y/Ho ratios (Pecoits et al., 2009)”
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    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    The Koegas Subgroup only develops in the deeper, southwestern part of the Griqualand West Basin; its absence in the shallower parts is explained by palaeobathymetric considerations.

    “The Koegas Subgroup only develops in the deeper, southwestern part of the Griqualand West Basin. Its absence in the shallower parts - where the Griquatown GIF is directly overlain by the Makganyene diamictite - is explained by palaeobathymetric considerations (Moore et al., 2001; Polteau, et al., 2006).”
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    Findingreasoning
    § 3.1 Iron formations deposited before the GOE

    A negative Ce anomaly is absent in the REE+Y plots of the Joffre Member, suggesting O2 levels below the Ce(III)/Ce(IV) redox boundary.

    “A negative Ce anomaly is absent in the REE+Y plots of the Joffre Member as well, suggesting O2 levels below the Ce(III)/Ce(IV) redox boundary.”
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    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    The regional transition from the stromatolitic Gamohaan Formation upward into the Kuruman BIF is continuous and indicates a progressive deepening of the basin.

    “The regional transition from the stromatolitic Gamohaan Formation upward into the Kuruman BIF is continuous and indicates a progressive deepening of the basin (Klein and Beukes, 1989; Sumner, 1997).”
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    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    The best age estimates for the deposition of the Dales Gorge and Joffre members are 2494-2464 Ma and 2454±3 Ma, respectively.

    “The best age estimates for the deposition of the Dales Gorge and Joffre members are 2494-2464 Ma (Trendall et al., 2004) and 2454±3 Ma (Pickard, 2002), respectively.”
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    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    The Dales Gorge Member is composed of relatively pure chemical precipitates, as supported by low Al, Ti, Th, Zr, Hf, and Sc concentrations.

    “The Dales Gorge Member is also composed of relatively pure chemical precipitates, as supported by low Al, Ti, Th, Zr, Hf, and Sc concentrations (Pecoits et al., 2009)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Pecoits et al., 2009 source

      Not checked in the free run.

  • May combine two claims.

    Findingnone given
    § 3.1 Iron formations deposited before the GOE

    The major IFs of South Africa are developed in the Griqualand West Basin of the 2.6-2.4 Ga Transvaal Supergroup, and comprise the Kuruman and Griquatown formations and BIFs of the Koegas Subgroup.

    “The major IFs of South Africa are developed in the Griqualand West Basin of the 2-6-2.4 Ga Transvaal Supergroup, and comprise the Kuruman and Griquatown formations and BIFs of the Koegas Subgroup (Fig. 19).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    The Koegas BIF represents sea-level fluctuations with alternating regressive and transgressive cycles, with IF deposition thought to have taken place during transgressions, punctuated by siliciclastic deposition during regressions.

    “The Koegas BIF represents sea-level fluctuations with alternating regressive and transgressive cycles. Iron formation deposition is thought to have taken place during transgressions, punctuated by siliciclastic deposition during regressions (Schröder et al., 2011).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Schröder et al., 2011 source

      Not checked in the free run.

  • May combine two claims.

    Findingown data
    § 3.1 Iron formations deposited before the GOE

    The Joffre and Dales Gorge members display similar REE+Y patterns, including large Eu anomalies, but the Joffre Member lacks a strong positive Y anomaly.

    “The two IFs display similar REE+Y patterns, including large Eu anomalies; however, the Joffre Member lacks a strong positive Y anomaly, which is typically associated with a seawater geochemical signature.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    The rhythmically micro-banded Kuruman BIF was deposited largely in an open-shelf environment below wave base and contains multiple cycles of shallowing-upward sequences.

    “The rhythmically micro-banded Kuruman BIF was deposited largely in an open-shelf environment below wave base and contains multiple cycles of shallowing-upward sequences (Beukes, 1984).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Beukes, 1984 source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    Iron isotope compositions in both the Joffre and Dales Gorge members show a wide range in δ56Fe values, indicating multiple Fe sources and pathways, with average δ56Fe values in the Joffre Member heavier than those of the Dales Gorge Member.

    “Iron isotope compositions in both the Joffre and the Dales Gorge members show a wide range in d 56 Fe values, indicating multiple Fe sources and pathways (Fig. 6), where average d 56 Fe values in the Joffre Member are heavier than those of the Dales Gorge Member (Johnson et al., 2008b; Pecoits et al., 2009; W Li et al., 2013a; Haugaard et al., 2016b)”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Johnson et al., 2008b

      Not checked in the free run.

    • cites Pecoits et al., 2009 source

      Not checked in the free run.

    • cites W Li et al., 2013a

      Not checked in the free run.

  • May combine two claims.

    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    The South African IFs are generally sulfur-poor and contain minimal detrital input as recorded in very low bulk Al and Ti abundances.

    “The IFs are also generally sulfurpoor and contain minimal detrital input as recorded in very low bulk Al and Ti abundances (Beukes, 1984; Beukes and Klein, 1990; Horstmann and Hälbich, 1995).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Beukes, 1984 source

      Not checked in the free run.

    • cites Beukes and Klein, 1990

      Not checked in the free run.

    • cites Horstmann and Hälbich, 1995

      Not checked in the free run.

  • May combine two claims.

    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    In situ oxygen isotope analysis documents multiple generations of oxides in the Dales Gorge Member and suggests a primary precipitation temperature as low as ~25 oC.

    “Detailed in situ oxygen isotope analysis (W. Li et al., 2013a), as discussed above (Fig. 8), documents multiple generations of oxides and suggests a primary precipitation temperature as low as ~25 o C.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites W. Li et al., 2013a

      Not checked in the free run.

  • May combine two claims.

    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    The Joffre Member contains many stilpnomelane granules of compositions that appear to record a mixture of volcanic (pyroclastic) and chemical components, making it a poor chemical proxy for atmospheric conditions at the time of deposition.

    “the Joffre Member contains many stilpnomelane granules of compositions that appear to record a mixture of volcanic (pyroclastic) and chemical components, thus making it a poor chemical proxy for atmospheric conditions at the time of deposition (Haugaard et al., 2016b)”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Haugaard et al., 2016b

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingcitation
    § 3.2 Minor iron formation deposition after the GOE and before ca. 1.88 Ga

    The entire Hotazel sequence is thought to have been deposited in a continental shelf environment that was starved of terrigenous siliciclastic input.

    “The entire sequence is thought to have been deposited in a continental shelf environment that was starved of terrigenous siliciclastic input (Schneiderhan et al., 2006).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Schneiderhan et al., 2006 source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    Several Canadian IF successions are Algoma-type and contain major gold deposits, including the ~2.71 Ga Woodburn Lake, ~2.97 Ga North Caribou, ~2.7 Ga Bearmore-Geraldton, ~2.7-2.6 Ga Rankin Inlet, ~2.7 Ga Hope Bay, and ~2.62 Ga Damoti Lake and Back River greenstone belts.

    “Several of these are Algoma-type IF successions that contain major gold deposits, including the ~2.71 Ga Woodburn Lake greenstone belt, the ~2.97 North Caribou greenstone belt, the ~2.7 Ga Bearmore-Geraldton greenstone belt, the ~2.7-2.6 Ga Rankin Inlet greenstone belt (Goucerol et al., 2016), the ~2.7 Ga Hope Bay greenstone belt (Sherlock et al., 2012), and the ~2.62 Ga BIF from Dam”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Goucerol et al., 2016

      Not checked in the free run.

    • cites Sherlock et al., 2012 source

      Not checked in the free run.

    • cites Haugaard et al., 2017a,b

      Not checked in the free run.

  • May combine two claims.

    Findingcitation
    § 3.2 Minor iron formation deposition after the GOE and before ca. 1.88 Ga

    Giant IFs were not deposited between ca. 2.40 and 1.88 Ga, but oolitic hematitic ironstones of the 2.32 Ga lower Timeball Hill Formation in South Africa were deposited in shallow water, above fair-weather wave base.

    “Giant IFs were not deposited between ca. 2.40 and 1.88 Ga, but oolitic hematitic ironstones of the 2.32 Ga lower Timeball Hill Formation in South Africa were deposited in shallow water, above fairweather wave base (Schweigart, 1965; Dorland, 1999).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Schweigart, 1965 source

      Not checked in the free run.

    • cites Dorland, 1999

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingreasoning
    § 3.2 Minor iron formation deposition after the GOE and before ca. 1.88 Ga

    Few geochemical data are available for the lower Timeball Hill Formation, partly because it contains significant amounts of siliciclastic material.

    “Few geochemical data are available for this unit, partly because it contains significant amounts of siliciclastic material.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation
    § 3.3 The ca. 1.88 Ga resurgence in iron formations

    The Animikie Basin contains another stratigraphic level with regionally extensive IFs that is stratigraphically above the 1.85 Ga Sudbury impact ejecta layer and older than the ca. 1.83 Ga regional metamorphic event.

    “This level is stratigraphically above the 1.85 Ga Sudbury impact ejecta layer and is older than the ca. 1.83 Ga regional metamorphic event related to the Penokean orogeny”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Cannon et al., 2010 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingcitation
    § 3.2 Minor iron formation deposition after the GOE and before ca. 1.88 Ga

    The Hotazel manganese (and iron) formation lies above basaltic andesites of the Ongeluk Formation and has been interpreted previously as a volcanogenic deposit.

    “The manganese (and iron) formation lies above basaltic andesites of the Ongeluk Formation and has been interpreted previously as a volcanogenic deposit (Cornell and Schütte, 1995).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Cornell and Schütte, 1995

      Not checked in the free run.

  • May combine two claims.

    Findingcitation
    § 3.3 The ca. 1.88 Ga resurgence in iron formations

    Deposition of IF on the Superior Craton is coincident with a peak in tonnage for volcanogenic massive sulfide (VMS) deposits, some of which were positioned in island arcs.

    “Deposition of IF on the Superior Craton is coincident with a peak in tonnage for VMS deposits, some of which were positioned in island arcs.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    Iron formations in the Quadrilátero Ferrífero region in Brazil, Middleback Ridge in South Australia, Nimba and Simandou Ranges in Liberia and Guinea, Krivoy Rog area in Ukraine, and Kursk Magnetic Anomaly region in Russia are broadly similar in age based on available geochronological and chemostratigraphical constraints, and display similar patterns of macrobanding.

    “Iron formations in the Quadrilátero Ferrífero region in Brazil, Middleback Ridge (Gawler Craton) in South Australia, Nimba and Simandou Ranges in Liberia and Guinea, Krivoy Rog area in Ukraine, and Kursk Magnetic Anomaly (KMA) region in Russia are broadly similar in age based on available geochronological and chemostratigraphical constraints, and also display similar patterns of macro”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Prilutzky et al., 1992

      Not checked in the free run.

    • cites Kulik and Korzhnev, 1997

      Not checked in the free run.

    • cites Egal et al., 2002 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Findingnone given
    § 3.2 Minor iron formation deposition after the GOE and before ca. 1.88 Ga

    Correlative IFs to the lower Timeball Hill Formation are not documented on other continents.

    “Correlative IFs are not documented on other continents.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation
    § 3.2 Minor iron formation deposition after the GOE and before ca. 1.88 Ga

    The 2.43 Ga Hotazel Formation, whose date of formation has recently been revised from earlier estimates of 2.2 Ga, contains the largest known manganese deposit in the world.

    “The 2.43 Ga Hotazel Formation, whose date of formation has recently been revised from earlier estimates of 2.2 Ga (Gumsley et al., 2017), contains the largest known manganese deposit in the world (Tsikos et al., 2003).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Gumsley et al., 2017 source

      Not checked in the free run.

    • cites Tsikos et al., 2003

      Not checked in the free run.

  • May combine two claims.

    Findingnone given
    § 3.1 Iron formations deposited before the GOE

    These IFs were deposited on reactivated continental margins, and are separated by prominent unconformities from overlying Palaeoproterozoic sequences, which correspond to a long gap in sedimentation following the supercontinent assembly at ca. 2.40 Ga.

    “These IFs were also deposited on reactivated continental margins, and are separated by prominent unconformities from overlying Palaeoproterozoic sequences, which correspond to a long gap in sedimentation following the supercontinent assembly at ca. 2.40 Ga.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation
    § 3.3 The ca. 1.88 Ga resurgence in iron formations

    The ca. 1.88 Ga GIF are commonly interbedded with, or overlain by, black sulfidic shales, which record the development of euxinic conditions in parts of the Animikie Basin.

    “the ca. 1.88 Ga GIF are commonly interbedded with, or overlain by, black sulfidic shales, which record the development of euxinic conditions in parts of the Animikie Basin”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Poulton et al., 2004, 2010

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingcitation
    § 3.2 Minor iron formation deposition after the GOE and before ca. 1.88 Ga

    The significance of weak Ce anomalies in the Hotazel deposits remains contentious considering co-existing positive La anomalies.

    “The significance of weak Ce anomalies remains contentious considering co-existing positive La anomalies (Tsikos and Moore, 1997).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Tsikos and Moore, 1997

      Not checked in the free run.

  • May combine two claims.

    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    Manganese, deposited as discrete Mn-oxide layers in the stratigraphically younger Hotazel Formation, is incorporated entirely in iron carbonate minerals in both the Griquatown and Koegas IFs, where its bulk-rock abundance locally reaches percent levels.

    “Manganese - deposited as discrete Mnoxide layers in the stratigraphically younger Hotazel Formation - is incorporated entirely in iron carbonate minerals in both the Griquatown and Koegas IFs, where its bulk-rock abundance locally reaches percent levels (Tsikos and Moore, 1997; Johnson et al., 2016; Kurzweil et al., 2016).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Tsikos and Moore, 1997

      Not checked in the free run.

    • cites Johnson et al., 2016 source

      Not checked in the free run.

    • cites Kurzweil et al., 2016 source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation
    § 3.1 Iron formations deposited before the GOE

    The Slave Craton IF consists of Mesoarchaean BIF of the ~2.85 Ga Central Slave Cover Group deposited in a continental rift-setting, and Neoarchaean BIF of the 2.62 Ga Slemon Group deposited in a back-arc basin.

    “important petrological and geochemical work was carried out on the Slave Craton IF that consists of Mesoarchaean BIF of the ~2.85 Ga Central Slave Cover Group deposited in a continental rift-setting (Haugaard et al., 2016a), and Neoarchaean BIF of the 2.62 Ga Slemon Group (Haugaard et al., 2017a) deposited in a back-arc basin (Haugaard et al., 2017b).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Haugaard et al., 2016a

      Not checked in the free run.

    • cites Haugaard et al., 2017a

      Not checked in the free run.

    • cites Haugaard et al., 2017b

      Not checked in the free run.

  • May combine two claims.

    Findingreasoning
    § 3.2 Minor iron formation deposition after the GOE and before ca. 1.88 Ga

    The Hotazel Mn-Fe deposits lack positive Eu anomalies, pointing to an extremely dilute hydrothermal signal at best.

    “The Hotazel Mn-Fe deposits lack positive Eu anomalies, pointing to an extremely dilute hydrothermal signal at best.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation
    § 3.3 The ca. 1.88 Ga resurgence in iron formations

    The North American GIFs are correlative based on high-precision geochronology and extend discontinuously at the surface for more than 3000 km along the southern and eastern margins of the Superior Craton.

    “Recognised now to be correlative based on high-precision geochronology”
    • Also stated in: § 3.3 The ca. 1.88 Ga resurgence in iron formations · plain
      “the North American GIFs extend discontinuously at the surface for more than 3000 km along the southern and eastern margins of the Superior Craton”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Findlay et al., 1995 source

      Not checked in the free run.

    • cites Machado et al., 1997 source

      Not checked in the free run.

    • cites Fralick et al., 2002 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingnone given
    § 3.2 Minor iron formation deposition after the GOE and before ca. 1.88 Ga

    The significance of the ca. 2.32 Ga magmatic event is poorly known.

    “However, the significance of this magmatic event is poorly known.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation
    § 3.4 Proterozoic age gap in Superior-type IF deposition

    Large sedimentary iron deposits that formed during the time gap (1.85-0.75 Ga) are absent, but several small IFs and Fe-rich lithologies in sedimentary rock-dominated successions are known.

    “Large sedimentary iron deposits that formed during this time gap (1.85-0.75 Ga) are indeed absent, but several small IFs and Fe-rich lithologies in sedimentary rock-dominated successions are known”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Bekker et al., 2010 source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation
    § Figure Captions

    The earliest magnetite is fine-grained and has low Si contents, whereas high-temperature magnetite is coarse-grained and/or contains high levels of Si.

    “Earliest magnetite is recorded in magnetite that is fine-grained and has low Si contents, whereas high-temperature magnetite is coarse-grained and/or contains high levels of Si (Huberty et al., 2012).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Huberty et al., 2012 source

      Not checked in the free run.

  • May combine two claims.

    Findingown data
    § Figure Captions

    εNd(t) values for iron formations scatter between mantle/primitive crust composition and those of old crust, indicating a mix of REE+Y sources.

    “ε Nd(t) values for IFs scatter between mantle/primitive crust composition and those of old crust, indicating a mix of REE+Y sources.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Jacobsen and Pimentel-Klose (1998a)

      Not checked in the free run.

    • cites Alibert and McCulloch (1993)

      Not checked in the free run.

    • cites Li et al. (2015)

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationcitation
    § 1. Introduction

    The ca. 2.32 Ga oolitic granular iron formation of the Timeball Hill Formation is composed of concentric cortices of hematite that were likely precipitated where Fe(II)-rich waters met more oxygenated shallow seawater.

    “Others, such as the ca. 2.32 Ga oolitic GIF of the Timeball Hill Formation in South Africa, are composed of concentric cortices of hematite (Dorland, 1999) that were likely precipitated where Fe(II)-rich waters met more oxygenated shallow seawater.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Dorland, 1999

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation
    § 1. Introduction

    Many granular iron formation granules are considered detrital, with some derived by sedimentary re-working of iron-rich clay, mudstones, arenites, and even stromatolites.

    “Many of the granules are considered detrital, with some being derived by sedimentary re-working of iron-rich clay, mudstones, arenites, and even stromatolites (e.g., Ojakangas, 1983; Simonson and Goode, 1989).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Ojakangas, 1983

      Not checked in the free run.

    • cites Simonson and Goode, 1989

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given
    § 1. Introduction

    The majority of iron formations were deposited between 2.80 and 1.85 Ga in the Neoarchaean and Palaeoproterozoic.

    “the majority having been deposited between 2.80 and 1.85 Ga in the Neoarchaean and Palaeoproterozoic”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation
    § 1. Introduction

    The sulfide-facies iron formations described by James (1954) are now believed to be pyritic carbonaceous shales and ferruginous slates, and therefore do not represent a chemical precipitate.

    “The sulfide-facies IF described by James (1954) are now believed to be pyritic carbonaceous shales and ferruginous slates, and therefore do not represent a chemical precipitate (Bekker et al., 2010).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Bekker et al., 2010 source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given
    § 1. Introduction

    Superior-type iron formations developed in passive-margin, sediment-dominated settings and generally lack direct stratigraphic relations with volcanic rocks.

    “Superior-type IFs developed in passive-margin, sediment-dominated settings (i.e., after stable continental shelves evolved) and generally lack direct stratigraphic relations with volcanic rocks.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation
    § 1. Introduction

    Algoma-type iron formations were formed close to volcanic arcs and spreading centres and produced by exhalative hydrothermal processes related to submarine volcanism.

    “Algoma-type IFs were apparently formed close to volcanic arcs and spreading centres and produced by exhalative hydrothermal processes related to submarine volcanism (e.g., Goodwin, 1962; Gross, 1980, 1983).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Goodwin, 1962 source

      Not checked in the free run.

    • cites Gross, 1980

      Not checked in the free run.

    • cites Gross, 1983 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation
    § 1. Introduction

    Superior-type iron formations are regarded as having been deposited in near-shore shelf environments because they are typically interbedded with, or grade into, carbonates and black shales.

    “These IFs are regarded as having been deposited in near-shore shelf environments (e.g., Trendall, 2002) because they are typically interbedded with, or grade into, carbonates and black shales (Gross, 1980).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Trendall, 2002

      Not checked in the free run.

    • cites Gross, 1980

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 1. Introduction

    Traditionally, iron oxides in iron formations are interpreted to have formed from an initial Fe(III)-oxyhydroxide phase, such as ferrihydrite, which precipitated in the photic zone from seawater via oxidation of dissolved Fe(II) at concentrations that may have ranged from 0.03 to 0.5 mM.

    “Traditionally, iron oxides in IF are interpreted to have formed from an initial Fe(III)-oxyhydroxide phase, e.g., ferrihydrite, Fe(OH)3, which precipitated in the photic zone from seawater via the oxidation of dissolved ferrous iron, Fe(II), at concentrations that may have ranged from 0.03 to 0.5 mM; Holland, 1973; Morris, 1993).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Holland, 1973 source

      Not checked in the free run.

    • cites Morris, 1993 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation
    § 1. Introduction

    Banded iron formations were generally, but not entirely, deposited in relatively deep-water settings, as they typically lack evidence for wave or storm action.

    “They consist mainly of interbanded iron- and silica-rich layers and were generally, but not entirely, deposited in relatively deep-water settings, as they typically lack evidence for wave or storm action (Simonson and Hassler, 1996; Trendall, 2002; Krape ž et al., 2003)”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Simonson and Hassler, 1996

      Not checked in the free run.

    • cites Trendall, 2002

      Not checked in the free run.

    • cites Krape ž et al., 2003

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationnone given
    § 1. Introduction

    Layering in banded iron formations can be laterally extensive, indicating deposition below wave base.

    “Layering in BIF can be laterally extensive, indicating deposition below wave base.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    The changing steepness of the REE+Y spectra (YbSN/CeSN) could be related to corresponding changes in depth of deposition, as suggested for modern seawater.

    “In addition, the changing steepness of the REE+Y spectra (YbSN/CeSN) could be related to corresponding changes in depth of deposition, as suggested for modern seawater (e.g., Piepgras and Jacobsen, 1992; Alibo and Nozaki, 1999).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Piepgras and Jacobsen, 1992

      Not checked in the free run.

    • cites Alibo and Nozaki, 1999

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 1. Introduction

    Recent work suggests that in the presence of dissolved silica, the initial water column precipitate may have been a Fe(III)-Si gel.

    “However, recent work suggests that in the presence of dissolved silica, the initial water column precipitate may have been a Fe(III)-Si gel (e.g., Percak-Dennett et al., 2011).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Percak-Dennett et al., 2011 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Archaean ridge crests were likely shallower than today, reflecting higher mantle temperatures, and under such conditions, hydrothermal effluent could have risen buoyantly upwards through the water column to the photic zone.

    “Archaean ridge crests were likely shallower than today (Isley, 1995), reflecting higher mantle temperatures, and under such conditions, hydrothermal effluent could have risen buoyantly upwards through the water column to the photic zone - where various oxidative mechanisms could have occurred (see section 2.4).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Isley, 1995 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning
    § 2.1 Hydrothermal sources of iron to the oceans

    Although modern hydrothermal Fe(II) input concentrations (1-3 nM) are significantly below what would be required to form an iron formation, this system provides evidence that long-distance transport of iron and formation of Superior-type iron formations is mechanistically possible.

    “Although modern hydrothermal Fe(II) input concentrations (1-3 nM) are significantly below what would be required to form an IF, this system provides evidence that the long-distance transport of iron and the formation of Superior type IF is mechanistically possible.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Positive Eu anomalies in hydrothermal fluids are linked to the breakdown of plagioclase minerals within the volcanic rocks underlying hydrothermal vents, as plagioclase is intrinsically enriched in Eu relative to other REE+Y during igneous crystallisation.

    “Positive Eu anomalies in hydrothermal fluids are linked to the breakdown of plagioclase minerals within the volcanic rocks underlying hydrothermal vents, as plagioclase is intrinsically enriched in Eu relative to other REE+Y during igneous crystallisation (Schnetzler and Philpotts, 1970; Graf, 1977, 1978; Fryer et al., 1979).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Schnetzler and Philpotts, 1970

      Not checked in the free run.

    • cites Graf, 1977 source

      Not checked in the free run.

    • cites Fryer et al., 1979 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Holland (1973) suggested that the iron was sourced from deep-marine, hydrothermally influenced waters and supplied to depositional settings via upwelling processes.

    “Holland (1973) had previously suggested that the iron was instead sourced from deep-marine, hydrothermally influenced waters and supplied to the depositional settings via upwelling processes.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Holland, 1973 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given
    § 1. Introduction

    The consensus suggests that the primary mineral phase of banded iron formations was a silica-associated Fe(III)-oxyhydroxide.

    “but we note here the consensus suggests that the primary mineral phase being a silica-associated Fe(III)-oxyhydroxide.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Eu remains in the soluble Eu2+ state in hydrothermal fluids because Eu2+ is more stable at higher temperatures.

    “Furthermore, Eu remains in the soluble Eu 2+ state in hydrothermal fluids because Eu 2+ is more stable at higher temperatures (Sverjensky, 1984; Bau, 1991).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Sverjensky, 1984 source

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    • cites Bau, 1991 source

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    Interpretationcitation
    § 1. Introduction

    Siderite in some iron formations has been interpreted as primary, but strong isotopic and petrographic arguments point instead to formation linked to remineralisation of organic matter.

    “Although siderite in some IF has been interpreted to be a primary mineral phase (e.g., Beukes and Klein, 1990), there are strong isotopic and petrographic arguments that point instead to formation linked to the remineralisation of organic matter (e.g., Johnson et al., 2003, 2008; Fischer et al., 2009; Pecoits et al., 2009; Heimann et al., 2010; Johnson et al., 2013).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Johnson et al., 2003 source

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    • cites Johnson et al., 2008

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    • cites Fischer et al., 2009

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    Interpretationcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Iron formations typically lack significant detrital input, which argued against a riverine source of the iron.

    “Furthermore, IFs typically lack significant detrital input, which argued against a riverine source of the iron (Holland, 1978).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Holland, 1978

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    Interpretationreasoning
    § 1. Introduction

    Organic material would have fuelled organic remineralisation reactions and is likely to have been largely consumed by excess Fe(III) oxidants during diagenesis and metamorphism.

    “Organic material, whether in the form of pelagic rain or intimately associated with sinking Fe(III)-oxyhydroxide particles, would have fuelled the organic remineralisation reactions mentioned above, and is likely to have been largely consumed by excess Fe(III) oxidants during diagenesis and metamorphism (see section 2.6).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Eu concentrations can also be elevated by erosion of Eu-enriched Archaean continental crust, and anomalies generated in vent systems may be diluted by mixing of seawater and hydrothermal fluids.

    “However, Eu concentrations can also be elevated by the erosion of Eu-enriched Archaean continental crust (Taylor and McLennan, 1985; Bohlar et al., 2004), and anomalies generated in vent systems may be diluted by mixing of seawater and hydrothermal fluids (Olivarez and Owen, 1991).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Taylor and McLennan, 1985

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    • cites Bohlar et al., 2004

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    • cites Olivarez and Owen, 1991

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    Premisecitation
    § 2.3 Plausible primary iron mineralogy

    Dissolved Fe(II) oxidation in the presence of dissolved silica produces an Fe(III)-Si gel that is homogenous on the nm scale, indicating a single phase in which Si and Fe are tightly bonded and distinct from Si sorbed to ferrihydrite.

    “PercakDennett et al. (2011) and Wu et al. (2012) studied dissolved Fe(II) oxidation in the presence of dissolved silica, which produced an Fe(III)-Si gel that was homogenous on the nm scale, indicating the presence of a single phase in which Si and Fe are tightly bonded and distinct from, for example, Si sorbed to ferrihydrite”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Percak-Dennett et al., 2011 source

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    • cites Wu et al., 2012

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  • Probably not a substantial claim: may not pass S1 (asserted).

    Interpretationreasoning
    § 2.3 Plausible primary iron mineralogy

    The primary Fe(III) minerals in IFs may have been enriched in SiO2.

    “raising the possibility that the primary Fe(III) minerals were enriched in SiO2”
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    Premisecitation
    § 2.3 Plausible primary iron mineralogy

    Iron-ore formation was a long-lived and multi-stage process.

    “geochronological studies of xenotime and monazite paragenesis within hematite and martite-goethite ore bodies that formed during hydrothermal alteration of IF indicate that iron-ore formation was a long-lived and multi-stage process (Rasmussen et al., 2007).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Rasmussen et al., 2007 source

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    Interpretationcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    The magnitude of positive Eu anomalies steadily decreases from the Eoarchaean, reflecting both high hydrothermal input and low dissolved oxygen required to stabilise Eu2+ for transport before the deep oceans became oxygenated.

    “The magnitude of positive Eu anomalies steadily decreases from the Eoarchaean, which reflects both high hydrothermal input and low dissolved oxygen required to stabilise Eu 2+ for transport before the deep oceans became oxygenated (Viehmann et al., 2015).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Viehmann et al., 2015 source

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    Interpretationcitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Typically, HREE are enriched in the oxide facies of iron formations, as the result of interaction between hydrothermal fluids and mid-ocean ridge basalt (MORB) at spreading centres, which are typically tholeiitic and depleted in LREE.

    “Typically, HREE are enriched in the oxide facies of IF, as the result of interaction between hydrothermal fluids and mid-ocean ridge basalt (MORB) at spreading centres, which are typically tholeiitic and depleted in LREE (Derry and Jacobsen, 1990; Bau, 1991).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Derry and Jacobsen, 1990 source

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    • cites Bau, 1991 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given
    § 2.3 Plausible primary iron mineralogy

    Most workers consider magnetite to have formed through diagenetic and metamorphic reactions.

    “most workers consider magnetite to have formed through diagenetic and metamorphic reactions”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Secular trends in the magnitude of Eu anomalies in large Superior-type iron formations have historically been assumed to record variations in hydrothermal flux.

    “Nonetheless, secular trends in the magnitude of Eu anomalies in large Superior-type IFs have historically been assumed to record variations in hydrothermal flux (e.g., Fryer, 1977a; Derry and Jacobsen, 1990; Danielson et al., 1992; Bau and Möller, 1993; Sreenivas and Murakami, 2005; Viehmann et al., 2015).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Fryer, 1977a

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    • cites Derry and Jacobsen, 1990 source

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    • cites Danielson et al., 1992 source

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    Premisecitation
    § 2.1 Hydrothermal sources of iron to the oceans

    Ce and Nd have short residence times in the modern ocean, 90-165 and 1000-1500 years, respectively.

    “Both Ce and Nd have short residence times in the modern ocean, 90-165 and 1000-1500 years, respectively (Amakawa et al., 1996)”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Amakawa et al., 1996 source

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  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given
    § 2.3 Plausible primary iron mineralogy

    Porewater pH in systems dominated by DIR will be in the range expected for greenalite precipitation.

    “it is important to note that porewater pH in systems dominated by DIR will be in the range expected for greenalite precipitation”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation
    § 2.3 Plausible primary iron mineralogy

    Fine-grained greenalite nanoparticles in laminated cherts have been taken as evidence for water column precipitation of greenalite and as a critical precursor to hematite and magnetite.

    “The identification of fine-grained greenalite nanoparticles in laminated cherts (Rasmussen et al., 2016, 2017) has been taken as evidence for water column precipitation of this mineral, and by extrapolation, as a critical precursor to hematite and magnetite.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Rasmussen et al., 2016, 2017

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationcitation
    § 2.3 Plausible primary iron mineralogy

    Green-rust may have been an important factor in Archaean IF deposition before the Great Oxidation Event (GOE).

    “Those authors further suggested that green-rust may have been an important factor in Archaean IF deposition before the Great Oxidation Event (GOE)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Halevy et al., 2017

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    Premisecitation
    § 2.3 Plausible primary iron mineralogy

    Green-rust can be found within a naturally stratified water column and may act as an important transitory phase between the redoxcline and the export of iron phases to the sediment.

    “Zegeye et al. (2012) demonstrated that green-rust can be found within a naturally stratified water column, and that it may act as an important transitory phase between the redoxcline and the export of iron phases to the sediment.”
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    • cites Zegeye et al., 2012 source

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    Premisecitation
    § 2.4 Available oxidants in seawater for Fe(II) oxidation

    Dissolved ferrous iron species, such as Fe2+ or Fe(OH)+, absorb radiation in the 200-400 nm range, leading to photochemical formation of dissolved ferric iron, which hydrolyses to form Fe(III)-oxyhydroxides at circumneutral pH.

    “Under such conditions, dissolved ferrous iron species, such as Fe 2+ or Fe(OH) + , absorb radiation in the 200-400 nm range, leading to the photochemical formation of dissolved ferric iron [reaction 1], which in turn, hydrolyses to form Fe(III)-oxyhydroxides at circumneutral pH (Cairns-Smith, 1978; Braterman et al., 1983; Anbar and Holland, 1992).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Cairns-Smith, 1978 source

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    • cites Braterman et al., 1983 source

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    • cites Anbar and Holland, 1992

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    • Rests on an assumption: Prior to the rise of atmospheric oxygen and the development of a protective ozone layer, Earth's surface was subjected to high levels of ultraviolet radiation.

  • Classified as probably not a substantial claim.

    Premisecitation
    § 2.3 Plausible primary iron mineralogy

    In experiments, reacting natural ferrihydrite-encrusted bacterial mats with dissolved Fe(II) formed hexagonal platelets of a siliceous green-rust phase, which then agglomerated into aggregates.

    “In experiments conducted by Li et al. (2017), the authors reacted natural ferrihydrite-encrusted bacterial mats with dissolved Fe(II) and showed that hexagonal platelets of a siliceous green-rust phase formed, which then agglomerated into aggregates.”
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    • cites Li et al., 2017

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 2.3 Plausible primary iron mineralogy

    The consensus amongst workers is that the precursor phase during sedimentation of IF was most likely Fe(III)-oxyhydroxides or an Fe(III)-Si gel.

    “Despite the consensus amongst workers that the precursor phase during the sedimentation of IF was most likely Fe(III)-oxyhydroxides (e.g., Konhauser et al., 2002; Kappler et al., 2005; Posth et al., 2014; Sun et al., 2015) or an Fe(III)-Si gel (e.g., Percak-Dennett et al., 2011; Zheng et al., 2016)”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Konhauser et al., 2002 source

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    • cites Kappler et al., 2005 source

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    • cites Posth et al., 2014 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 2.3 Plausible primary iron mineralogy

    Lake Matano is proposed to be an analogue for the Archaean ocean.

    “an environment proposed to be an analogue for the Archaean ocean (Crowe et al., 2008)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Crowe et al., 2008 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning
    § 2.3 Plausible primary iron mineralogy

    Green-rust may have been a precursor to magnetite in IFs.

    “it is possible that green-rust was a precursor to magnetite in IFs.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 2.3 Plausible primary iron mineralogy

    Green rust might be the product of a bacterially mediated reaction involving Fe(III)-reducing bacteria and magnetite.

    “Etique et al. (2015) demonstrated that green rust might be the product of a bacterially mediated reaction involving Fe(III)-reducing bacteria and magnetite.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Etique et al., 2015 source

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    Premisecitation
    § 2.3 Plausible primary iron mineralogy

    Green-rust phases are of mixed valence and require a source of Fe(III).

    “Critically, green-rust phases are of mixed valence (e.g., Rickard and Luther, 2007), and accordingly, require a source of Fe(III).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Rickard and Luther, 2007

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    Premisecitation
    § 2.3 Plausible primary iron mineralogy

    The earliest generation of magnetite in the Dales Gorge Member contains minimal Si content and has δ18O values of ca. -6 to +4‰, indicating formation temperatures between ~50°C and ~100°C.

    “The earliest generation of magnetite in the Dales Gorge Member contains minimal Si content (Huberty et al., 2012), and in situ analysis shows that this magnetite has δ 18 O values of ca. -6 to +4‰, indicating formation temperatures between ~50 o C and ~100 o C (Fig. 8).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Huberty et al., 2012 source

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    • cites W. Li et al., 2013a

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    Premisecitation
    § 2.5.1 Evidence in the rock record for the evolution of oxygenic photosynthesis

    Satkoski et al. used stable Fe and radiogenic U-Th-Pb isotope data from the 3.2 Ga Manzimnyama IF to demonstrate that proximal, shallow-water samples record precipitation under more oxic conditions compared to the distal, deeper-water facies, and that U enrichment in the shallow-water samples indicates the presence of free oxygen in the photic zone.

    “Satkoski et al. (2015) used a combination of stable Fe and radiogenic UTh-Pb isotope data from the 3.2 Ga Manzimnyama IF of the Fig Tree Group, South Africa to demonstrate that proximal, shallow-water samples record precipitation under more oxic conditions compared to the distal, deeper-water facies, and that the presence of U enrichment in the shallowwater samples indicates the”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Satkoski et al., 2015 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning
    § 2.5.1 Evidence in the rock record for the evolution of oxygenic photosynthesis

    The limited extent of predicted Fe(II) oxidation could have been linked to oxidation pathways independent of O2.

    “Although this approach clearly delineates a shift in the oxidative capacity of surface seawater, the limited extent of predicted Fe(II) oxidation could have been linked to oxidation pathways independent of O2.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning
    § 2.4 Available oxidants in seawater for Fe(II) oxidation

    These contradictory findings may suggest that primitive cyanobacteria had, at least by 1.9 Ga, some form of protection mechanism against Fe(II) concentrations becoming too high in proximal environments.

    “These contradictory findings may suggest that primitive cyanobacteria had, at least by 1.9 Ga, some form of protection mechanism against Fe(II) concentrations becoming too high in proximal environments.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § 2.5.1 Evidence in the rock record for the evolution of oxygenic photosynthesis

    Since photoferrotrophy produces particulate Fe(III)-oxyhydroxide as well as organic carbon, this process is more likely to produce organic carbon-poor, iron-rich rocks like IF, because much of the organic matter would be oxidised via DIR.

    “Since photoferrotrophy produces a particulate Fe(III)-oxyhydroxide as well as organic carbon, this process is more likely, as outlined below, to produce organic carbon-poor, iron-rich rocks like IF, because much of the organic matter would be oxidised via DIR”
    Quote in the paperSubstantial claim

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    Interpretationcitation
    § [2] 4Fe 2+ + HCO3 -+ 10H2O à 4Fe(OH)3 + CH2O + 7H +

    Such biogenic minerals are expected to bind to organic carbon (cells) and silica, with the net effect being the deposition of Fe-Si-C aggregates onto the sea floor.

    “Such biogenic minerals are expected to bind to organic carbon (cells) and silica, with the net effect being the deposition of Fe-Si-C aggregates onto the sea floor (Posth et al., 2008, 2010).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Posth et al., 2008, 2010

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Interpretationcitation
    § 2.5.1 Evidence in the rock record for the evolution of oxygenic photosynthesis

    These Mo isotope signatures likely required an oxygenated water column and delivery of Mn(IV) oxides to the sediment pile, given rapid Mn(IV) oxide reduction via Fe2+.

    “These Mo isotope signatures likely required an oxygenated water column and delivery of Mn(IV) oxides to the sediment pile, given rapid Mn(IV) oxide reduction via Fe 2+ (e.g., Busigny et al., 2014).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Busigny et al., 2014 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 2.5.1 Evidence in the rock record for the evolution of oxygenic photosynthesis

    Results of the same approach applied to the 3.4 Ga Marble Bar Chert led W. Li et al. to conclude that Fe(II) oxidation occurred under anoxic marine conditions by photoferrotrophy.

    “Results of the same approach applied to the 3.4 Ga Marble Bar Chert led W. Li et al. (2013b) to conclude that Fe(II) oxidation occurred under anoxic marine conditions by photoferrotrophy.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites W. Li et al., 2013b

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 2.5.1 Evidence in the rock record for the evolution of oxygenic photosynthesis

    Czaja et al. modelling Fe isotope fractionations estimated free oxygen contents of <0.001% that of modern seawater during deposition of the Isua IF.

    “Czaja et al. (2013), modelling Fe isotope fractionations, estimated free oxygen contents of &lt;0.001% that of modern seawater during deposition of the Isua IF.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Czaja et al., 2013 source

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  • May combine two claims.

    Premisecitation
    § 2.4 Available oxidants in seawater for Fe(II) oxidation

    Fe(II)-oxidisers were associated with low oxygen concentrations and active Fe redox cycling in the oxic-anoxic transition zone (<3 μM O2, <0.2 μM H2S) in Chesapeake Bay.

    “These authors demonstrated that the Fe(II)-oxidisers were associated with low oxygen concentrations and active Fe redox cycling in the oxic-anoxic transition zone (&lt;3 µ M O2, &lt;0.2 µ M H2S).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Field et al., 2016 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning
    § 2.5.1 Evidence in the rock record for the evolution of oxygenic photosynthesis

    If the Mo necessary to allow for Mo nitrogenase to be the predominant pathway for biological nitrogen fixation was sourced by weak oxidative weathering, then cyanobacteria would have been active since ~3.2 Ga.

    “If we assume that the Mo necessary to allow for Mo nitrogenase to be the predominant pathway for biological nitrogen fixation was sourced by weak oxidative weathering, then the implicit implication is that cyanobacteria would have been active since ~3.2 Ga.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 2.4 Available oxidants in seawater for Fe(II) oxidation

    Some ca. 1.88 Ga Gunflint-type microfossils from the Animikie Basin have been reinterpreted as chemolithoautotrophic Fe(II)-oxidisers.

    “some of the ca. 1.88 Ga Gunflint-type microfossils from the Animikie Basin have been reinterpreted as chemolithoautotrophic Fe(II)-oxidisers (Golubic and Lee, 1999; Planavsky et al., 2009).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Golubic and Lee, 1999

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    • cites Planavsky et al., 2009 source

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  • May combine two claims.

    Interpretationcitation
    § 2.5.2 Evidence in the rock record for the evolution of photoferrotrophy

    It is likely that photoferrotrophs flourishing at depth could have exhausted dissolved phosphorous in upwelling waters, thus outcompeting cyanobacteria for a key nutrient, and by extension limiting their activity in overlying waters.

    “It is also likely that photoferrotrophs flourishing at depth could have exhausted dissolved phosphorous in upwelling waters, thus outcompeting cyanobacteria for a key nutrient, and by extension limiting their activity in overlying waters (Jones et al., 2015).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Jones et al., 2015 source

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  • May combine two claims.

    Premisecitation
    § 2.5.2 Evidence in the rock record for the evolution of photoferrotrophy

    Much of the evidence for pre-GOE surface-ocean oxygenation remains contested and proxies that specifically focus on shallow-ocean redox conditions, such as carbonate iodine and REEs, point to the dominance of IF and carbonate deposition under broadly anoxic conditions in the oceans until the GOE.

    “An argument in favour of photoferrotrophy having played a prominent role in IF deposition is that much of the evidence for pre-GOE surface-ocean oxygenation remains contested and proxies that specifically focus on shallow-ocean redox conditions, such as carbonate iodine (Hardisty et al., 2014) and REEs (Planavsky et al., 2010a), point to the dominance of IF and”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Hardisty et al., 2014 source

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    • cites Planavsky et al., 2010a

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  • May combine two claims.

    Interpretationcitation
    § 2.5.1 Evidence in the rock record for the evolution of oxygenic photosynthesis

    The construction of stromatolite-like structures by the anoxygenic phototroph Rhodopseudomonas palustris challenges the notion that stromatolites uniquely mark cyanobacterial presence in the geologic record and that microfossil metabolism can be inferred from morphology alone.

    “However, the construction of stromatolite-like structures by the anoxygenic phototroph Rhodopseudomonas palustris (Bosak et al., 2007) challenges the notion that stromatolites uniquely mark cyanobacterial presence in the geologic record and that microfossil metabolism can be inferred from morphology alone.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Bosak et al., 2007 source

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    Premisecitation
    § [2] 4Fe 2+ + HCO3 -+ 10H2O à 4Fe(OH)3 + CH2O + 7H +

    Photoferrotrophs have been identified in Kabuno Bay, Democratic Republic of Congo, a basin characterised by ferruginous conditions and by observed rates of Fe(II) oxidation that appear to exceed those required for IF deposition.

    “Photoferrotrophs have also been identified in Kabuno Bay, Democratic Republic of Congo, a basin characterised by ferruginous conditions and by observed rates of Fe(II) oxidation that appear to exceed those required for IF deposition (Llirós et al., 2015).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Llirós et al., 2015 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 2.5.2 Evidence in the rock record for the evolution of photoferrotrophy

    Numerical models have been used to suggest that anoxygenic photosynthesisers would control Fe(II) oxidation even if the surface layer was weakly oxygenated.

    “Numerical models have been used to suggest that anoxygenic photosynthesisers would control Fe(II) oxidation even if the surface layer was weakly oxygenated (Kappler et al., 2005).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Kappler et al., 2005 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation
    § 2.5.1 Evidence in the rock record for the evolution of oxygenic photosynthesis

    Strong Re and Mo enrichments and coupled Mo-Fe isotope data were interpreted as evidence for oxidative weathering of sulfide-bearing minerals on the continents, and thus the evolution of oxygenic photosynthesis as early as ca. 2.6 Ga.

    “Strong Re and Mo enrichments and coupled Mo-Fe isotope data were interpreted as evidence for oxidative weathering of sulfide-bearing minerals on the continents, and thus the evolution of oxygenic photosynthesis as early as ca. 2.6 Ga (Anbar et al., 2007; Kendall et al., 2010; Czaja et al., 2012; Stüeken et al., 2015b).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Anbar et al., 2007 source

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    • cites Kendall et al., 2010 source

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    • cites Czaja et al., 2012 source

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  • May combine two claims.

    Premisecitation
    § 2.5.1 Evidence in the rock record for the evolution of oxygenic photosynthesis

    Satkoski et al. calculated shallow photic zone O2 contents at ~10 μM (between 10^-3 and 10^-2 POL) and deep-water O2 contents at ~0.4 μM.

    “Based on modelling of Fe isotopes in the Manzimnyama jasper, Satkoski et al. (2015) calculated shallow photic zone O2 contents at ~10 µM (between 10 -3 and 10 -2 POL, or Present Ocean Level; Fig. 10), and deep-water O2 contents at ~0.4 µM.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Satkoski et al., 2015 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 2.4 Available oxidants in seawater for Fe(II) oxidation

    Some Gunflint fossil groupings (e.g., Gunflintia) may encompass multiple types of bacteria, including those with different metabolisms.

    “some Gunflint fossil groupings (e.g., Gunflintia ) may encompass multiple types of bacteria, including those with different metabolisms (Shapiro and Konhauser, 2015).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Shapiro and Konhauser, 2015

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  • May combine two claims.

    Interpretationnone given
    § 2.5.1 Evidence in the rock record for the evolution of oxygenic photosynthesis

    Many indicators exist in the rock record pointing to an earlier appearance in the Archaean for both oxygenic photosynthesis and anoxygenic photosynthesis.

    “many indicators exist in the rock record pointing to an earlier appearance in the Archaean for both.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given
    § 2.5.1 Evidence in the rock record for the evolution of oxygenic photosynthesis

    Photoferrotrophs can drive a wide range of extent of water column Fe(II) oxidation, including quantitative oxidation.

    “Indeed, as explored below, photoferrotrophs can drive a wide range of extent of water column Fe(II) oxidation-including quantitative oxidation.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given
    § 2.5.1 Evidence in the rock record for the evolution of oxygenic photosynthesis

    Fe(II) oxidation does not require oxygenic photosynthesis.

    “As outlined above, Fe(II) oxidation does not require oxygenic photosynthesis.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 2.6 Available reductants and diagenesis of iron formations

    Under ideal growth conditions, as much as 70% of the biologically produced Fe(III) could have been recycled back into the water column via fermentation and organic carbon oxidation coupled to DIR.

    “They showed that under ideal growth conditions, as much as 70% of the biologically produced Fe(III) could have been recycled back into the water column via fermentation and organic carbon oxidation coupled to DIR.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Konhauser et al., 2005 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation
    § 2.6 Available reductants and diagenesis of iron formations

    The 1:1 line can be considered a common source of Fe for specific magnetite-hematite and magnetite-siderite pairs, reflecting authigenic formation of magnetite and siderite through reduction of Fe(III)-oxyhydroxide.

    “The 1:1 line can be considered a common source of Fe for specific magnetite-hematite and magnetite-siderite pairs (e.g., W. Li et al., 2013a), taken to reflect authigenic formation of magnetite and siderite through reduction of Fe(III)-oxyhydroxide”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites W. Li et al., 2013a

      Not checked in the free run.

  • May combine two claims.

    Premisecitation
    § 2.6 Available reductants and diagenesis of iron formations

    DIR has been shown to be broadly distributed amongst several known Proteobacteria genera, suggesting that this form of metabolism became widespread early in the course of evolution.

    “Moreover, DIR has been shown to be broadly distributed amongst several known Proteobacteria genera, suggesting that this form of metabolism became widespread early in the course of evolution (Barns and Nierzwicki-Bauer, 1997).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Barns and Nierzwicki-Bauer, 1997

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning
    § 2.6 Available reductants and diagenesis of iron formations

    Magnetite that has δ18O values less than zero requires formation at lower temperature, and in such cases, direct, microbially-catalysed reduction seems the best explanation.

    “However, as noted above, magnetite that has δ 18 O values less than zero requires formation at lower temperature (Fig. 8), and, in such cases, direct, microbially-catalysed reduction seems the best explanation.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given
    § 2.6 Available reductants and diagenesis of iron formations

    IF minerals that formed in equilibrium with seawater should have δ56Fe values offset from the seawater composition based on specific mineral-fluid Fe isotope fractionation factors.

    “IF minerals that formed in equilibrium with seawater should have δ 56 Fe values offset from the seawater composition based on specific mineral-fluid Fe isotope fractionation factors.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation
    § 2.6 Available reductants and diagenesis of iron formations

    Although IF sedimentation was likely highly pulsed and variable, slow net accumulation rates were probably linked to a low siliciclastic flux that allowed for accumulation of pure chemical sediments.

    “although IF sedimentation was likely highly pulsed and variable (Bekker et al., 2010; Haugaard et al., 2016a), slow net accumulation rates were probably linked to a low siliciclastic flux that allowed for accumulation of pure chemical sediments”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Bekker et al., 2010 source

      Not checked in the free run.

    • cites Haugaard et al., 2016a

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning
    § 2.6 Available reductants and diagenesis of iron formations

    The model explains why organic carbon contents are lowest in oxide-facies IF compared to siderite-facies IF and the relation between δ13C and wt.% Corg.

    “This model also explains the observation that organic carbon contents are lowest in oxide-facies IF as compared to siderite-facies IF and the relation between δ 13 C and wt.% Corg (Fig. 14)”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning
    § 2.6 Available reductants and diagenesis of iron formations

    In the absence of O2, the fermentation products in the bottom waters and/or shallow sediments would have been oxidised via some other form of anaerobic respiratory process.

    “In the absence of O2, the fermentation products in the bottom waters and/or shallow sediments would have been oxidised via some other form of anaerobic respiratory process.”
    Quote in the paperNot a substantial claim

  • May combine two claims. The quote only partly states this claim.

    Interpretationcitation
    § 2.6 Available reductants and diagenesis of iron formations

    Coupling the reduction of some Fe(III) minerals to the oxidation of organic matter explains the low content of organic carbon in IFs (<0.5 wt.%), the highly negative δ13C values of early diagenetic Fe(II)-rich carbonates, the small-scale heterogeneity in δ56Fe values, the presence of Fe(II)-bearing minerals in IF, and the general lack of microfossils preserved in Fe-rich layers lacking siliciation

    “Significantly, coupling the reduction of some Fe(III) minerals to the oxidation of organic matter not only explains the low content of organic carbon in IFs (&lt;0.5 wt.%; Gole and Klein, 1981), but it also explains highly negative δ 13 C values of the early diagenetic Fe(II)-rich carbonates (Perry et al., 1973; Walker, 1984; Baur et al., 1985; Heimann et al., 2010; Craddock and Dauphas,”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Gole and Klein, 1981

      Not checked in the free run.

    • cites Perry et al., 1973 source

      Not checked in the free run.

    • cites Walker, 1984 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning
    § 2.6 Available reductants and diagenesis of iron formations

    Such quantities of Corg are similar to those in Neoarchaean black shales, and highlight the possibility that significant organic carbon was buried with Fe(III) precipitates during IF deposition.

    “Such quantities of Corg are similar to those in Neoarchaean black shales, and highlight the possibility that significant organic carbon was buried with Fe(III) precipitates during IF deposition.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationcitation
    § 2.6 Available reductants and diagenesis of iron formations

    The difference in the carbonate- versus oxide-bound δ56Fe signals could be causally linked to DIR or to varying extents of oxidation on a basin-wide scale.

    “The difference in the carbonateversus oxide-bound δ 56 Fe signals could be causally linked to DIR or to varying extents of oxidation on a basin-wide scale (e.g., Oonk, 2017)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Oonk, 2017

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning
    § 2.6 Available reductants and diagenesis of iron formations

    Iron may be oxidised, deposited on continental shelves, reduced, shuttled to distal locations, oxidised, settled to the deep basin along with organic carbon, and then reduced in the final location of the sediment before being lithified into IF.

    “Iron may be oxidised, deposited on continental shelves, reduced, shuttled to distal locations, oxidised, settled to the deep basin along with organic carbon, and then reduced in the final location of the sediment before being lithified into IF”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 3.1 Iron formations deposited before the GOE

    Isley and Abbott (1999) estimated that during those 100 m.y., perhaps as much as 60% of the global volume of preserved IF was deposited.

    “Isley and Abbott (1999) estimated that during those 100 m.y., perhaps as much as 60% of the global volume of preserved IF was deposited.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Isley and Abbott (1999)

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning
    § 2.6 Available reductants and diagenesis of iron formations

    DIR may operate on both large (basin-wide Fe-shuttle) and local (in situ microbial reduction) scales.

    “the comparison seemingly indicates that DIR may operate on both large (basin-wide Fe-shuttle) and local ( in situ microbial reduction) scales”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation
    § 2.7 Iron formations as tracers of seawater redox

    This suggests that the water column from which Fe(III) oxyhydroxides precipitated was relatively anoxic, or at least below the Eh of the Ce4+/Ce3+ redox couple.

    “This suggests that the water column from which Fe(III) oxyhydroxides precipitated was relatively anoxic, or at least below the Eh of the Ce 4+ /Ce 3+ redox couple (Bau and Dulski, 1996)”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Bau and Dulski, 1996

      Not checked in the free run.

  • May combine two claims.

    Premisecitation
    § 3. Neoarchaean-Palaeoproterozoic Iron Formations

    In the rock record, the GOE is manifested by changes including loss of detrital uraninite, pyrite, and siderite from fluvial siliciclastic sediments at ca. 2.4 Ga; loss of iron from palaeosols older than ca. 2.4 Ga; appearance of red beds after ca. 2.3 Ga; loss of S-MIF in sulfide and sulfate minerals after 2.3 Ga; and an increase in Cr and U contents in IF at 2.45 Ga.

    “In the rock record, this event is manifested by a number of changes (see Farquhar et al., 2011, 2014, for reviews), including (1) loss of easily oxidisable detrital uraninite, pyrite, and siderite from fluvial siliciclastic sediments at ca. 2.4 Ga”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Farquhar et al., 2000 source

      Not checked in the free run.

    • cites Bekker et al., 2004 source

      Not checked in the free run.

    • cites Konhauser et al., 2011 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning
    § 2.7 Iron formations as tracers of seawater redox

    This consistent depletion in LREE suggests the lack of a discrete redoxcline during this time period and points toward O2-independent Fe(II) oxidation mechanisms.

    “This consistent depletion in LREE suggests the lack of a discrete redoxcline during this time period and points toward O2-independent Fe(II) oxidation mechanisms”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation
    § 2.7 Iron formations as tracers of seawater redox

    Deposition of late Palaeoproterozoic IF at ca. 1.88 Ga occurred in basins having varied redox conditions and a strong redoxcline separating an upper oxic water column from deeper waters that were suboxic to anoxic.

    “This interpretation implies deposition of late Palaeoproterozoic IF at ca. 1.88 Ga in basins having varied redox conditions and a strong redoxcline separating an upper oxic water column from deeper waters that were suboxic to anoxic (Planavsky et al., 2009)”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Planavsky et al., 2009 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation
    § 3.1 Iron formations deposited before the GOE

    Major IF deposition occurred between 2.50-2.40 Ga in association with a series of mantle plume breakout events and was immediately preceded by the final stage in the supercontinent assembly of the Gawler Craton, North China Craton, East Antarctica Craton, and the central Indian tectonic zone of India.

    “Major IF deposition occurred between 2.50-2.40 Ga in association with a series of mantle plume breakout events (e.g., Heaman, 1997) and was immediately preceded by the final stage in the supercontinent assembly of the Gawler Craton (South Australia), North China Craton, East Antarctica Craton, and in the central Indian tectonic zone of India (Barley et al., 2005)”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Heaman, 1997 source

      Not checked in the free run.

    • cites Barley et al., 2005 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given
    § 2.7 Iron formations as tracers of seawater redox

    To oxidise Mn(II), the oxidation state of the basin needs to be significantly higher than that required for Fe(II) oxidation.

    “To oxidise Mn(II), the oxidation state of the basin needs to be significantly higher than that required for Fe(II) oxidation.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § 2.7 Iron formations as tracers of seawater redox

    This pattern indicates a relative Mn enrichment in the basin with time, either passively or due to effective reductive cycling of Mn(IV) oxyhydroxides during IF deposition.

    “This pattern indicates a relative Mn enrichment in the basin with time, either passively or due to effective reductive cycling of Mn(IV) oxyhydroxides during IF deposition”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 2.7 Iron formations as tracers of seawater redox

    Ce anomalies need not develop solely within the water column of a basin; they can develop in groundwater systems.

    “Ce anomalies need not develop solely within the water column of a basin. For instance, Ce anomalies can develop in groundwater systems (Johanneson et al., 2006)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Johanneson et al., 2006 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation
    § 3.1 Iron formations deposited before the GOE

    Becker and Clayton (1976) noted isotopic exchange between minerals within the Dales Gorge Member at burial metamorphic temperatures of 270 to 310 oC, and suggested that oxygen isotopes in quartz and carbonate may have equilibrated completely.

    “Based on bulksample analysis, Becker and Clayton (1976) noted isotopic exchange between minerals within the Dales Gorge Member at burial metamorphic temperatures of 270 to 310 o C, and suggested that oxygen isotopes in quartz and carbonate may have equilibrated completely.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Becker and Clayton (1976) source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 3.1 Iron formations deposited before the GOE

    The consensus view is that the Brockman Iron Formation was deposited on a large, stable, and clastic-starved continental platform, only influenced by episodic inputs of fine-grained tuffaceous detritus.

    “The consensus view is that the Brockman Iron Formation was deposited on a large, stable, and clastic-starved continental platform, which was only influenced by episodic inputs of fine-grained tuffaceous detritus”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Ewers and Morris, 1981

      Not checked in the free run.

    • cites Gross, 1983 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation
    § 3.1 Iron formations deposited before the GOE

    Beukes and Gutzmer (2008) suggest that the Hamersley and Transvaal BIF sequences reflect deposition in the same basin, although it cannot be ruled out that they were two separate, but coeval basins.

    “Beukes and Gutzmer (2008) presented detailed correlations between the Hamersley and Transvaal BIFs, and suggest that these sequences reflect deposition in the same basin, as originally proposed by Button (1976) and then Cheney (1996), although it cannot be ruled out that they were two separate, but coeval basins.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Beukes and Gutzmer (2008)

      Not checked in the free run.

    • cites Button (1976)

      Not checked in the free run.

    • cites Cheney (1996) source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 3.1 Iron formations deposited before the GOE

    Barley et al. (1997) suggested that deposition of the Hamersley IFs was possibly linked to major submarine magmatic plume activity in the form of a large igneous province (LIP).

    “Barley et al. (1997) suggested that deposition of the Hamersley IFs was possibly linked to major submarine magmatic plume activity in the form of a large igneous province (LIP)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Barley et al. (1997) source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation
    § 3.1 Iron formations deposited before the GOE

    Morris (1993) proposed that the depositional environment for the Hamersley BIFs included a steady source of silica and iron, and a water depth shallow enough to form the large carbonate platforms.

    “Morris (1993) also proposed that the depositional environment for the Hamersley BIFs included a steady source of silica and iron, and a water depth shallow enough to form the large carbonate platforms”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Morris (1993) source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation
    § 3.3 The ca. 1.88 Ga resurgence in iron formations

    The absence of iron-oxide exhalites is unlikely to reflect preservational bias because slightly younger Cu-rich VMS deposits in arc settings contain abundant hematite and magnetite exhalites, jasper, and IF.

    “This observation is unlikely to reflect preservational bias because slightly younger 1.84, 1.79, and 1.78 Ga Cu-rich VMS deposits that similarly formed in arc settings contain abundant hematite and magnetite exhalites, jasper, and IF”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Slack et al., 2007 source

      Not checked in the free run.

    • cites Slack and Cannon, 2009

      Not checked in the free run.

    • cites Bekker et al., 2010 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationnone given
    § 3.3 The ca. 1.88 Ga resurgence in iron formations

    These IFs are mineralogically and texturally different from the ca. 1.88 Ga GIF and were likely deposited in deeper waters, below fair-weather wave base, and probably even below storm wave base.

    “These IFs are mineralogically and texturally different from the ca. 1.88 Ga GIF and were likely deposited in deeper waters, below fair-weather wave base, and, probably, even below storm wave base.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationcitation
    § 3.2 Minor iron formation deposition after the GOE and before ca. 1.88 Ga

    Recent applications of combined iron isotope geochemistry and Mn/Fe ratios suggest that enrichment in the Hotazel palaeobasin in Mn and isotopically light Fe could have ensued progressively through prior protracted deposition.

    “recent applications of combined iron isotope geochemistry and Mn/Fe ratios suggest that enrichment in the Hotazel palaeobasin in Mn and isotopically light Fe could have ensued progressively through prior protracted deposition of”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationcitation
    § 3.2 Minor iron formation deposition after the GOE and before ca. 1.88 Ga

    The deposition of the lower Timeball Hill Formation at ca. 2.32 Ga may coincide with a magmatic event at that time.

    “Its deposition at ca. 2.32 Ga (Hannah et al., 2004) may coincide with a magmatic event at that time”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Hannah et al., 2004 source

      Not checked in the free run.

    • cites Eriksson et al., 1994a, b

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning
    § 3.3 The ca. 1.88 Ga resurgence in iron formations

    The presence of these units indicates that the conditions necessary for IF deposition in marine settings were reestablished in the Animikie Basin after 1.85 Ga, in association with mafic volcanism.

    “The presence of these units indicates that the conditions necessary for IF deposition in marine settings were reestablished in the Animikie Basin after 1.85 Ga, in association with mafic volcanism.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation
    § 3.4 Proterozoic age gap in Superior-type IF deposition

    Between 1.85 and 0.8 Ga, open-marine, deep-water environments may, in some cases, have been sufficiently oxygenated to oxidise and precipitate Fe(II) from hydrothermal plumes as Fe(III) oxyhydroxides, whereas evidence for Mn(II) oxidation in the deep ocean is generally lacking.

    “Between 1.85 and 0.8 Ga, open-marine, deep-water environments may, in some cases, have been sufficiently oxygenated to oxidise and precipitate Fe(II) from hydrothermal plumes as Fe(III) oxyhydroxides (e.g., Slack et al., 2007, 2009), whereas evidence for Mn(II) oxidation in the deep ocean is generally lacking.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Slack et al., 2007, 2009

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Interpretationreasoning
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    The decrease in seawater Ni content after 2.7 Ga is consistent with a progressively cooling Archaean mantle, whereby the volume of ultramafic melts and komatiites decreased, and less Ni was dissolved into seawater.

    “The decrease in seawater Ni content after 2.7 Ga is consistent with a progressively cooling Archaean mantle, whereby the volume of ultramafic melts produced by partial mantle melting and the eruption of Ni-bearing ultramafic volcanic rocks (known as komatiites) decreased, and, subsequently, less Ni was dissolved into seawater.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    To maintain low atmospheric oxygen levels despite O2 production in the oceans requires that oxygen sinks must have been much larger than they are now, or the oxygen flux was greatly reduced, or both.

    “To maintain low atmospheric oxygen levels despite O2 production in the oceans requires that oxygen sinks must have been much larger than they are now (including reduced solutes in seawater, volcanic gases, or crust), or the oxygen flux was greatly reduced (due to limited cyanobacterial productivity), or both.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationcitation
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    It is possible that prior to the GOE cyanobacterial activity was depressed by high Fe(II) concentrations in surface waters.

    “It is also possible that prior to the GOE cyanobacterial activity was depressed by high Fe(II) concentrations in surface waters.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Swanner et al., 2015 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    Elevated 87Sr/86Sr ratios in the early Archaean oceans point to significant exposure of evolved continental crust at that time.

    “Such conclusions, however, conflict with the growing evidence for elevated 87 Sr/ 86 Sr ratios in the early Archaean oceans that point to significant exposure of evolved continental crust at that time (Satkoski et al., 2016, 2017).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Satkoski et al., 2016, 2017

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Classified as probably not a substantial claim.

    Interpretationcitation
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    Recent models suggest that continental landmasses did not reach modern level of emergence in the Archaean.

    “Recent models suggest that continental landmasses did not reach modern level of emergence in the Archaean”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Korenega et al., 2017

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    Euxinic conditions could develop under an Archaean anoxic atmosphere.

    “Scott et al. (2011) have subsequently shown that euxinic conditions could develop under an Archaean anoxic atmosphere, and alternatives to the 'whiff' model have been proposed.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Scott et al., 2011 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing). May combine two claims.

    Interpretationreasoning
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    A shift from predominantly submarine to subaerial volcanism, releasing more oxidising volatiles such as H2O, CO2, and SO2, would have reduced the overall sink for oxygen and led to the rise of atmospheric oxygen.

    “A shift from predominantly submarine to subaerial volcanism, releasing more oxidising volatiles such as H2O, CO2, and SO2, would have reduced the overall sink for oxygen and led to the rise of atmospheric oxygen.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    Dissolved Cr dispersal would be limited upon delivery to the oceans due to low solubility of Cr(III) at marine pH, rapid reduction of Cr(VI) by aqueous Fe(II), and near-instantaneous coprecipitation of Cr(III) with Fe(III)-oxyhydroxide.

    “Considering the low solubility of Cr(III) at marine pH levels, the rapid reduction of Cr(VI) by aqueous Fe(II), and near-instantaneous coprecipitation of Cr(III) with Fe(III)-oxyhydroxide (e.g., Fendorf, 1995), dissolved Cr dispersal would be limited upon delivery to the oceans.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Fendorf, 1995 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    A moderate enrichment in Cr (molar Cr/Ti) beginning at 2.45 Ga in the Weeli Wolli Formation and similarly aged Cauê Iron Formation was followed by a spike in Cr enrichment in oolitic and pisolitic ironstone associated with the ca. 2.32 Ga Timeball Hill Formation.

    “For instance, a moderate enrichment in Cr (as expressed by the molar Cr/Ti ratio) beginning at 2.45 Ga in the Weeli Wolli Formation, as well as the similarly aged Cauê Iron Formation in Brazil, was followed by a spike in Cr enrichment in oolitic and pisolitic ironstone associated with the ca. 2.32 Ga Timeball Hill Formation (Konhauser et al., 2011).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Konhauser et al., 2011 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationnone given
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    Several lines of evidence tentatively point to the evolution of cyanobacteria by at least 3.0 Ga, and perhaps even earlier.

    “several lines of evidence tentatively point to their evolution by at least 3.0 Ga, and perhaps even earlier.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    Mobilisation and incorporation of Cr into IF indicates enhanced chemical weathering at that time, most likely associated with the emergence of aerobic oxidation of continental pyrite.

    “Given the insolubility of Cr(III) minerals, mobilisation and incorporation of Cr into IF indicates enhanced chemical weathering at that time, most likely associated with the emergence of aerobic oxidation of continental pyrite.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation
    § 3.4 Proterozoic age gap in Superior-type IF deposition

    The emerging consensus is that the redox state of the deep ocean was spatially and temporally variable during the mid-Proterozoic but was generally at a low oxidation state.

    “The emerging consensus is that the redox state of the deep ocean was spatially and temporally variable during the mid-Proterozoic but was generally at a low oxidation state”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Planavsky et al., 2011 source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Interpretationreasoning
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    Acid-generated attack would have enhanced in-situ dissolution of Cr-bearing crustal minerals (including soils) that previously retained Cr under anoxic, pH-neutral conditions, leading to increased continental Cr(III) supply to the oceans.

    “Such an acid-generated attack would have enhanced in-situ dissolution of Cr-bearing crustal minerals (including soils) that previously retained Cr under anoxic, but pH-neutral conditions, leading to increased continental Cr(III) supply to the oceans.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    Pyrite oxidation generates significant acidity.

    “Pyrite oxidation generates significant acidity [reaction 10]:”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    The whiff is recorded by spikes in Mo and Re concentrations, elevated nitrogen isotope values, and iron speciation data.

    “The whiff is recorded by spikes in Mo and Re concentrations, elevated nitrogen isotope values, and iron speciation data (Anbar et al., 2007; Reinhard et al., 2009; Garvin et al., 2009);”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Anbar et al., 2007 source

      Not checked in the free run.

    • cites Reinhard et al., 2009 source

      Not checked in the free run.

    • cites Garvin et al., 2009 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    Limited emergent continental crust would have severely limited the availability of continental crustal sources for weathering and compounded nutrient limitation for elements such as Mo supplied dominantly by oxidative weathering.

    “Limited emergent continental crust would not only have severely limited the availability of continental crustal sources for weathering, but it would have compounded nutrient limitation for elements such as Mo supplied dominantly by oxidative weathering of crustal materials”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    There is a 10‰ increase in δ13C values in kerogen in the post-2.7 Ga shallow-water facies relative to the deep-water settings, suggesting that the shallow waters became oxygenated (or oxidant-rich) as cyanobacteria became more abundant.

    “there is a 10‰ increase in δ 13 C values in kerogen in the post-2.7 Ga shallow-water facies relative to the deep-water settings, suggesting that the shallow waters became oxygenated (or oxidant-rich) as cyanobacteria became more abundant.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationreasoning
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    The Cr enrichment beginning at ca. 2.45 Ga reflects Earth's first acidic continental rock drainage, whereby acidity was generated with rising O2 at unprecedented scales via oxidation of a previously untapped terrestrial pyrite reservoir.

    “Accordingly, it has been suggested that the Cr enrichment beginning at ca. 2.45 Ga reflects Earth's first acidic continental rock drainage, whereby acidity was generated with rising O2 at unprecedented scales via the oxidation of a previously untapped terrestrial pyrite reservoir.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Konhauser et al., 2011 source

      Not checked in the free run.

    • cites Bekker and Holland, 2012

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    New evidence indicates that early Archaean continents were greater in size and that a larger proportion was emergent than previously thought, highlighting the potential importance of consumption of O2 through oxidative weathering of the continents and suppression of atmospheric O2 until the GOE.

    “New evidence that the early Archaean continents were greater in size and that a larger proportion was emergent than previously thought, highlights the potential importance of consumption of O2 through oxidative weathering of the continents and suppression of atmospheric O2 until the GOE”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Satkoski et al., 2016, 2017

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Interpretationreasoning
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    It is possible that a Ni famine eventually led to a cascade of events that began with reduced methane production, the expansion of cyanobacteria into deep-water settings previously occupied by methanogens, and ultimately increased oxygenic photosynthesis that tipped the atmospheric redox balance in favour of oxygen, leading to the GOE.

    “It is thus possible that a Ni famine eventually led to a cascade of events that began with reduced methane production, the expansion of cyanobacteria into deep-water settings previously occupied by methanogens, and ultimately increased oxygenic photosynthesis that tipped the atmospheric redox balance in favour of oxygen, leading to the GOE.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    This process continued perhaps for 150-200 m.y. (the crustal half-life) until the volume of easily oxidisable pyrite in the weathered crust was diminished.

    “This process continued perhaps for 150-200 m.y. the crustal half-life (Garrels and Mackenzie, 1971) - until the volume of easily oxidisable pyrite in the weathered crust was diminished (Konhauser et al., 2011; Bekker and Holland, 2012).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Garrels and Mackenzie, 1971

      Not checked in the free run.

    • cites Konhauser et al., 2011 source

      Not checked in the free run.

    • cites Bekker and Holland, 2012

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    Mn deposits are uncommon during this time period.

    “Similarly, Mn deposits are uncommon during this time period.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Atmospheric and ocean oxygen levels remained low until ca. 1.2 Ga or even ca. 800 Ma.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given
    § 5. Concluding remarks

    Evidence for these processes continues to be found in trace element and isotopic signatures contained within Fe-rich chemical deposits.

    “Evidence for these processes continues to be found in trace element and isotopic signatures contained within these Ferich chemical deposits as they continue to be the subject of intense study.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisereasoning
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    IFs resurface, reaching their peak at ca. 1.88 Ga.

    “Consistent with these observations, IFs resurface, reaching their peak at ca. 1.88 Ga.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    Following the end of the Lomagundi carbon isotope excursion, multiple redox indicators point to the collapse of seawater sulfate and atmospheric/oceanic oxygenation.

    “Following the end of the Lomagundi carbon isotope excursion, multiple redox indicators point to the collapse of seawater sulfate and atmospheric/oceanic oxygenation (e.g., Planavsky et al., 2012b; Scott et al., 2008, 2014; Bekker and Holland, 2012; Partin et al., 2013a, b).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Planavsky et al., 2012b source

      Not checked in the free run.

    • cites Scott et al., 2008, 2014

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Bekker and Holland, 2012 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    Paleosol data suggest atmospheric oxygen might have risen to levels of 0.03 atm, and perhaps as high as 0.1 atm.

    “For instance, paleosol data from that time suggests that atmospheric oxygen might have risen to levels of 0.03 atm, and perhaps even as high as 0.1 atm Bekker and Holland (2012) (Fig. 10).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Bekker and Holland, 2012

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    At ca. 1.88 Ga, shallow-marine GIFs were deposited above wave-base on several cratons, indicating a large flux of Fe(II) and Mn(II) from submarine-hydrothermal vents in association with an extensive LIP event.

    “At this time, shallow-marine GIFs were deposited above wave-base on several cratons (e.g., Rasmussen et al., 2012; Bekker et al., 2014) indicating a large flux of Fe(II) and Mn(II) from submarine-hydrothermal vents in association with an extensive LIP event.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Rasmussen et al., 2012 source

      Not checked in the free run.

    • cites Bekker et al., 2014

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning
    § Figure Captions

    The lower δ30Si values of iron formation cherts cannot be explained solely by Si sorption to Fe(III)-oxyhydroxides, but likely involve Fe(III)-Si gels as the primary phase.

    “Lower δ 30 Si values of IF cherts cannot be explained solely by Si sorption to Fe(III)-oxyhydroxides, but likely involves Fe(III)-Si gels as the primary phase.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given
    § 5. Concluding remarks

    Identification of widespread DIR, a deeply rooted metabolism in both bacteria and archaea, has allowed understanding of the diversity of microbial ecology in the Archaean.

    “Identification of widespread DIR, a deeply rooted metabolism in both bacteria and archaea, has also allowed us to understand the diversity of microbial ecology in the Archaean.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    The extent and volume of these GIFs point to a rather peculiar state of the Earth System characterised by fully Fe-charged deep oceans like in the Archaean, and oxygenated nearshore conditions like in the Phanerozoic.

    “The extent and volume of these GIFs point to a rather peculiar state of the Earth System characterised by fully Fe-charged deep oceans like in the Archaean, and oxygenated nearshore conditions like in the Phanerozoic.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    This low-oxygen redox state in the deep oceans formed a prelude to Snowball glaciations, the rise of atmospheric and oceanic oxygen, and the emergence of complex life.

    “This low-oxygen redox state in the deep oceans formed a prelude to Snowball glaciations, the rise of atmospheric and oceanic oxygen, and the emergence of complex life; the only return of massive IFs was in association with the Sturtian glaciation (e.g., Klein and Beukes, 1993; Hofmann et al., 1998).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Klein and Beukes, 1993

      Not checked in the free run.

    • cites Hofmann et al., 1998

      Not checked in the free run.

    • The authors state this as an assumption: Atmospheric and ocean oxygen levels remained low until ca. 1.2 Ga or even ca. 800 Ma.

  • May combine two claims.

    Interpretationnone given
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    The Phanerozoic is a logical continuation of this trend during which higher atmospheric oxygen and a more intense biological pump restricted ironstones to relatively short time periods when the emplacement of LIPs resulted in greenhouse conditions, sea level rise, and extensive anoxic conditions in ocean basins.

    “The Phanerozoic is a logical continuation of this trend during which higher atmospheric oxygen and a more intense biological pump restricted ironstones to relatively short time periods when the emplacement of LIPs resulted in greenhouse conditions, sea level rise, and extensive anoxic conditions in ocean basins.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisenone given
    § 5. Concluding remarks

    Iron formations are a defining part of the Neoarchaean to Palaeoproterozoic marine sedimentary record.

    “Iron formations are a defining part of the Neoarchaean to Palaeoproterozoic marine sedimentary record.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given
    § 5. Concluding remarks

    The emergence of an aerobic biosphere was likely brought on by an oxidative component to nutrient cycling and chemical weathering reactions, potentially altering nutrient fluxes to the oceans.

    “The emergence of an aerobic biosphere was likely brought on by an oxidative component to nutrient cycling and chemical weathering reactions, potentially altering nutrient fluxes to the oceans.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given
    § 5. Concluding remarks

    Evidence for extensive microbial Fe(III) reduction (DIR) on a basin-wide scale, as well as locally in the sediment, is compelling.

    “In addition, evidence for extensive microbial Fe(III) reduction (e.g., DIR), on a basin-wide scale, as well as locally in the sediment, seems compelling.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § Figure Captions

    Intermediate εNd(t) values for shales associated with Hamersley Basin iron formations indicate that local continental crust may have near-zero εNd(t), which would increase the continental component of REE+Y relative to an assumed continental εNd(t) value of -3.

    “Intermediate ε Nd(t) values for associated shales indicate local continental crust may have near-zero ε Nd(t), which would increase the continental component of REE+Y relative to an assumed continental ε Nd(t) value of -3.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    The Cu concentration record for IFs and shales is relatively constant in abundance, reminiscent of the Zn record, raising the possibility of stabilisation of these trace metals by organic ligand complexation.

    “Although the Cu concentration record presented by Chi Fru et al. (2016) for IFs and shales is relatively constant in terms of abundance reminiscent of the Zn record raising the possibility of stabilisation of these trace metals by organic ligand complexation (see Robbins et al., 2013; Scott et al., 2013) - there is a clear trend in the stable isotopes values of Cu.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Chi Fru et al., 2016 source

      Not checked in the free run.

    • cites Robbins et al., 2013 source

      Not checked in the free run.

    • cites Scott et al., 2013 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationcitation
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    The ability of cyanobacteria in the ocean's photic zones to remotely facilitate their own nutrient supply via O2-enhanced chemical weathering may represent an unrecognised positive biological feedback.

    “The ability of cyanobacteria in the ocean's photic zones to remotely facilitate their own nutrient supply via O2-enhanced chemical weathering may represent an unrecognised positive biological feedback (Konhauser et al., 2011).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Konhauser et al., 2011 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning
    § 4. Iron Formations, Primary Productivity, and Atmospheric Oxygenation

    A growing worldwide database for IFs and much more precise ages point to a dynamic redox state of the deep oceans, with IFs speaking to the water column's episodic anoxic (ferruginous) state; for the rest of the time low but substantial deep-ocean oxygen levels restricted Fe(II) transport in solution from hydrothermal vents.

    “However, a growing worldwide database for IFs and much more precise ages point to a dynamic redox state of the deep-oceans with IFs speaking to the water column's episodic anoxic (=ferruginous) state; for the rest of the time low, but substantial deepocean oxygen levels restricted Fe(II) transport in solution from hydrothermal vents.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: Atmospheric and ocean oxygen levels remained low until ca. 1.2 Ga or even ca. 800 Ma.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given
    § 5. Concluding remarks

    The IF record has helped shape the view on the evolution of aerobic metabolisms tied to earlier expansion of cyanobacteria throughout the surface oceans during the Archaean.

    “For example, the IF record has helped shape our view on the evolution of aerobic metabolisms tied to earlier expansion of cyanobacteria throughout the surface oceans during the Archaean.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § 5. Concluding remarks

    A complex set of factors, including the evolution of submarine-hydrothermal systems, is behind the secular distribution of IF, rather than simply the deep marine redox evolution (ocean oxygenation) as was often imagined by early workers.

    “Similarly, a complex set of factors - including the evolution of submarine-hydrothermal systems - is behind the secular distribution, rather than simply the deep marine redox evolution (i.e., ocean oxygenation) as was often imagined by early workers.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationnone given
    § Figure Captions

    Mn(IV)-hydroxide dissolution in an anoxic water column lowers Y/Ho ratios, raises LREE to HREE ratios, and increases Ce concentration relative to neighbouring REE (La and Pr).

    “Mn(IV)-hydroxide dissolution in anoxic water column lowers Y/Ho ratios, raises LREE to HREE ratios, and increases Ce concentration relative to neighboring REE (La and Pr).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given
    § Figure Captions

    The very fine hematite in oxide-facies BIF of the Joffre Member is likely a product of secondary oxidation of magnetite.

    “The latter likely is a product of secondary oxidation of magnetite.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationnone given
    § Figure Captions

    Delivery of Fe(OH)3 to sediment is controlled by O2 concentrations and/or metabolism of photoferrotrophic bacteria.

    “delivery of Fe(OH)3 to sediment is controlled by O2 concentrations and/or metabolism of photoferrotrophic bacteria.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data
    § Figure Captions

    The estimated original organic carbon content of oxide-facies iron formation is comparable to that measured in Neoarchaean black shales, indicating potentially large amounts of initial organic carbon deposition that was later respired to produce siderite and magnetite via dissimilatory iron reduction (DIR).

    “which is comparable to those measured in Neoarchaean black shales, indicating potentially large amounts of initial organic carbon deposition that was later respired to produce siderite and magnetite via DIR.”
    Quote in the paperSubstantial claim
206 of 206

  • The authors state this as an assumption.

    Fe and REE+Y will not be fractionated during transport from spreading ridges or other exhalative centres, owing to the high sorption capacity of Fe(III)-oxyhydroxides.

    “It is generally assumed that Fe and REE+Y will not be fractionated during transport from spreading ridges or other exhalative centres, owing to the high sorption capacity of Fe(III)oxyhydroxides”

  • The authors state this as an assumption.

    REE+Y patterns record the source of iron due to high partition coefficients of REEs onto hydrothermal precipitates.

    “based on the assumption that their patterns record the source of iron due high partition coefficients of the REEs onto hydrothermal precipitates (e.g., Koeppenkastrop and De Carlo, 1992)”

  • The paper relies on this without support.

    Fe(III) is essentially insoluble at circumneutral pH values.

    “because Fe(III) is essentially insoluble at circumneutral pH values”

  • The authors state this as an assumption.

    The sources of REE+Y closely track the sources of Fe(II).

    “Assuming that the sources of REE+Y closely track the sources of Fe(II)”

  • The paper relies on this without support.

    Prior to the rise of atmospheric oxygen and the development of a protective ozone layer, Earth's surface was subjected to high levels of ultraviolet radiation.

    “Prior to the rise of atmospheric oxygen and the development of a protective ozone layer, Earth's surface would have been subjected to high levels of ultraviolet radiation.”

  • The paper relies on this without support.

    Ocean waters at this time were anoxic and could have supported high concentrations of dissolved Fe(II).

    “Ocean waters at this time were anoxic and could have supported high concentrations of dissolved Fe(II).”

  • The authors state this as an assumption.

    Carbonate precipitation/dissolution, and accompanying buffering effects linked with a dynamic DIC reservoir, are ignored in the mass-balance model.

    “For simplicity, carbonate precipitation/dissolution, and accompanying buffering effects, linked with a dynamic DIC reservoir, are ignored.”

  • The authors state this as an assumption.

    A constant DIC concentration, C0, is contributed from seawater to the sediment profile and is equal to the DIC concentration of the overlying water column.

    “A basic assumption of the model is that a constant DIC concentration, C0, is contributed from seawater to the sediment profile and is equal to the DIC concentration of the overlying water column.”

  • The authors state this as an assumption.

    The Nd-Fe isotope interpretations outlined by Li et al. (2015) are correct.

    “assuming the Nd-Fe isotope interpretations outlined by Li et al. (2015) are correct”

  • The authors state this as an assumption.

    The general solution for the diagenetic expression is obtained assuming steady state.

    “The general solution for this expression was obtained assuming steady state, = 0, and the boundary condition C = , giving the following analytical solution [equation B]:”

  • The authors state this as an assumption.

    The iron in the ca. 1.88 Ga GIF was hydrothermally derived.

    “assuming that the iron was hydrothermally derived”

  • The authors state this as an assumption.

    After ca. 1.85 Ga, Superior-type IFs were not deposited for approximately 1.1 b.y. until precipitation of Rapitan-type IF.

    “It is generally assumed that after ca. 1.85 Ga, Superior-type IFs were not deposited for approximately 1.1 b.y. until precipitation of Rapitan-type IF”

  • The paper relies on this without support.

    The oxygen content of the oceans directly controls seawater U concentrations once oxidative continental weathering was established.

    “Given that the oxygen content of the oceans directly controls seawater U concentrations once oxidative continental weathering was established”

  • The paper relies on this without support.

    Most organic matter produced in the upper water column will be remineralised before reaching the seafloor.

    “most organic matter produced in the upper water column will be remineralised before reaching the seafloor”

  • The paper relies on this without support.

    Continental freeboard depends more on mantle temperature, crustal composition, and continental hypsometry than on the growth of continental crust.

    “Continental freeboard depends more on mantle temperature, crustal composition, and continental hypsometry (also temperature-dependent) than on the growth of continental crust.”

  • The authors state this as an assumption.

    Atmospheric and ocean oxygen levels remained low until ca. 1.2 Ga or even ca. 800 Ma.

    “It is generally assumed that atmospheric and ocean oxygen levels remained low until ca. 1.2 Ga (Kah et al., 2004) or even ca. 800 Ma (Thomson et al., 2015; Turner and Bekker, 2016; Planavsky et al., 2014b).”
16 of 16

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Iron formations indicate that the deep Archean ocean contained Fe2+(aq) and so was anoxic.

    “Iron formations (IFs), which are marine chemical sedimentary rocks rich in iron and silica [15 to 40 weight % (wt %) Fe and 40 to 60 wt % SiO2], indicate that the deep Archean ocean contained Fe2+(aq) and so was anoxic [e.g., (72)].”

    From The Archean atmosphere (2020) · cites this paper as [72]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Figure 11 gives conflicting thicknesses at 5 m/day upwelling

    Major

    For 0.1 mM (100 μM) Fe(II), a 5 m/day upwelling rate, and the same 1.4 × 10−5 M/day oxidation rate, the main text says the required layer exceeds 100 m. The figure caption instead says it is approximately 35 m.

  • Figure 11 gives conflicting diffusion-only layer thicknesses

    Major

    The main text assigns a 17.6 m layer to an eddy-diffusion rate of 0.1 cm2/s. The Figure 11 caption assigns 17.6 m to 1 cm2/s and 5.6 m to 0.1 cm2/s for the same stated Fe(II) concentration and oxidation rate.

  • Figure 5 uses two different Eu-anomaly normalizations

    Minor

    The text describes Figure 5's Eu anomalies as chondrite-normalized, while the figure caption calls them PAAS-normalized. These are different reference compositions for the same plotted data.

3 of 3

Cites

Flagged first, then by citations

48 of the 564 references couldn’t be matched to a known paper.

Research works printed but not linked: 10

  1. Akhmedov, 1972, Hematite oolites in sedimentary rocks of the Pechenga complex, materials on mineralogy of Kola Peninsula, Nauka, 9, 135
  2. Akhmedov, 1972, 4, 125
  3. Bau, 1995, Yttrium and holmium in South Pacific seawater: vertical distribution and possible fractionation mechanisms, Chem. Erde, 55, 1
  4. Button, 1976, Transvaal and Hamersley basins—review of basin development and mineral deposits, Miner. Sci. Eng., 8, 262
  5. Eriksson, 1994, The Bushy Bend lavas, a new volcanic member of the Pretoria Group, Transvaal Sequence, S. Afr. J. Geol., 97, 1
  6. Hartlaub, 2007, Circa 2.3Ga magmatism of the Arrowsmith Orogeny, Uranium City Region, Western Churchill Craton, Can. J. Earth Sci., 115, 181
  7. Master, 1991, 238, 1
  8. Nealson, 1990, Iron reduction by bacteria: a potential role in the genesis of banded iron formations, Am. J. Sci., 290, 35
  9. Often, 1985, The early Proterozoic Karasjok Greenstone Belt, Norway: a preliminary description of lithology, stratigraphy and mineralization, Norges Geol. Unders. Bull., 403, 75
  10. Prilutzky, 1992, Reconstruction of environmental conditions of early Proterozoic carbonate deposits of the Ukrainian and Baltic Shields based on isotopic studies, Lithol. Miner. Deposits, 5, 76

Cited by

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Related

Authors
Konhauser, K. O., Planavsky, N. J., Hardisty, D. S., Robbins, L. J., Warchola, T. J., Haugaard, R., Lalonde, S. V., Partin, C. A., Oonk, P. B. H., Tsikos, H., Lyons, T. W., Bekker, A., & Johnson, C. M.
Affiliations
  • University of Alberta (CA)
  • NASA Astrobiology Institute (US)
  • Woods Hole Oceanographic Institution (US)
  • Institut Universitaire Européen de la Mer (FR)
  • University of Saskatchewan (CA)
  • Rhodes University (ZA)
  • University of California, Riverside (US)
  • University of Wisconsin–Madison (US)
Corresponding author
Konhauser, K.O.
ORCID
Venue
Earth-Science Reviews
Publisher
Elsevier BV
Published
2017-09
Volume
172
Pages
140-177
ISSN
0012-8252 (ISSN-L)
DOI
10.1016/j.earscirev.2017.06.012
OpenAlex
W2728922582
Cited by
537
References
564
Citations by year
2026: 62 · 2025: 76 · 2024: 76 · 2023: 67 · 2022: 65 · 2021: 57 · 2020: 47 · 2019: 41 · 2018: 38 · 2017: 7
FWCI
24.81
Type
journal article
Language
en
Open access
Licence
Locations
  • Earth-Science Reviews (publishedVersion)
  • Helmholtz Centre for Ocean Research Kiel (GEOMAR) (acceptedVersion)
  • HAL (submittedVersion, other-oa)
  • Open Access Server of the Woods Hole Scientific Community (Woods Hole Scientific Community) (submittedVersion)
Funders
Natural Sciences and Engineering Research Council of Canada (RGPIN-165831, RGPIN-00062, RGPIN-316500)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Stratigraphy of Fossils
  • Physical Sciences › Earth and Planetary Sciences › Geochemistry and Petrology › Geochemistry and Elemental Analysis
  • Physical Sciences › Earth and Planetary Sciences › Geophysics › Geological and Geochemical Analysis
Keywords
iron-formation, Neoarchaean, Paleoproterozoic, Great Oxidation Event, iron cycling, Fe(II) oxidation, oxygenic photosynthesis, hydrothermal systems, seawater chemistry

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-08.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-08.

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