Minimal biomass deposition in banded iron formations inferred from organic matter and clay relationships

Dodd, Matthew S.; Pirajno, Franco; Wan, Yusheng; Karhu, Juha A.

doi:10.1038/s41467-019-12975-z

Cited by 14 publications

(19 citation statements)

References 60 publications

(103 reference statements)

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“…38 ). Yet, cyanobacteria in the palaeontological record are primarily benthic, with sparse evidence for pelagic forms [39][40][41] . Hypotheses for the limited pelagic productivity during the Proterozoic range from an inaccessible, toxic or damaging photic zone to late evolution of a planktonic lifestyle 21,66,77 .…”

Section: Methodsmentioning

confidence: 99%

“…1). As the relative contributions of benthic and pelagic to total marine C org burial are highly uncertain [38][39][40][41][42] , we expressed the benthic term as a fraction of total marine burial, assumed to be at modern levels. Beyond the marine realm, we considered the possible effect of terrestrial mats in the Precambrian 43 .…”

Section: Spinning Down To Oxygenationmentioning

confidence: 99%

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Possible link between Earth’s rotation rate and oxygenation

et al. 2021

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The biotic and abiotic controls on major shifts in atmospheric oxygen and the persistence of low-oxygen periods over a majority of Earth’s history remain under debate. Explanations of Earth’s stepwise pattern of oxygenation have mostly neglected the effect of changing diel illumination dynamics linked to daylength, which has increased through geological time due to Earth’s rotational deceleration caused by tidal friction. Here we used microsensor measurements and dynamic modelling of interfacial solute fluxes in cyanobacterial mats to investigate the effect of changing daylength on Precambrian benthic ecosystems. Simulated increases in daylength across Earth’s historical range boosted the diel benthic oxygen export, even when the gross photosynthetic production remained constant. This fundamental relationship between net productivity and daylength emerges from the interaction of diffusive mass transfer and diel illumination dynamics, and is amplified by metabolic regulation and microbial behaviour. We found that the resultant daylength-driven surplus organic carbon burial could have shaped the increase in atmospheric oxygen that occurred during the Great and Neoproterozoic Oxidation Events. Our suggested mechanism, which links the coinciding increases in daylength and atmospheric oxygen via enhanced net productivity, reveals a possible contribution of planetary mechanics to the evolution of Earth’s biology and geochemistry.

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Section: Methodsmentioning

confidence: 99%

Section: Spinning Down To Oxygenationmentioning

confidence: 99%

Possible link between Earth’s rotation rate and oxygenation

et al. 2021

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“…Some of the organic compounds were degraded by diagenetic and metamorphic processes (Köhler et al, 2013;Posth et al, 2013;Halama et al, 2016). In addition, there is evidence that the depositional environment was most likely scarce in organic compounds (Dodd et al, 2019). Thus, the majority of the organic compounds was likely lost prior to deposition.…”

Section: Introductionmentioning

confidence: 99%

Fate of organic compounds during transformation of ferrihydrite in iron formations

Jelavić¹,

Mitchell²,

Sand³

2020

Geochem. Persp. Let.

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The absence of organic compounds from Precambrian iron formations (IF) challenges the hypothesis of the biogenic origin of IF. Here we address the fate of adsorbed organic compounds during transformation from ferrihydrite to hematite. We determined the binding energy between hematite and common molecular terminations found in extracellular polymeric substances and biofilms: carboxylic, hydroxyl and phosphate functional groups. We found that the bond between hematite and hydroxyl groups is approximately 2 times stronger than the bond between hematite-carboxyl and-phosphate groups. We transformed synthetic ferrihydrite to hematite at 90°C in presence of glycerol, which has a high density of hydroxyl groups, and measured the amount of mineral associated glycerol before and after the transformation. We show that the transformation releases glycerol highlighting that organic compounds adsorbed at precursor ferrihydrite could be desorbed during the process of IF sedimentation and diagenesis. Our results suggest that the absence of organic compounds in IF should not be used as evidence against their biogenic origin.

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“…24−28 The Fe 2+ produced by these reactions may have reacted with the remaining HFOs to form magnetite, or precipitated directly as Fe carbonate (siderite) or Fe 2+ silicates as early diagenetic phases. 14,29−31 Organic carbon is present in very low abundance in IFs, 32 possibly because it was respired away by reduction of excess Fe 3+ .…”

Section: Introductionmentioning

confidence: 99%

Isotopic Constraints on the Nature of Primary Precipitates in Archean–Early Paleoproterozoic Iron Formations from Determinations of the Iron Phonon Density of States of Greenalite and 2L- and 6L-Ferrihydrite

Heard

Dauphas

Hinz

et al. 2023

ACS Earth Space Chem.

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Iron formations (IFs) are chemical sedimentary rocks that were widely deposited before the Great Oxidation Event (GOE) around 2.4–2.2 Ga. It is generally thought that IFs precipitated as hydrated Fe3+ oxides (HFOs) such as ferrihydrite following surface oxidation of Fe2+-rich, anoxic deep waters. This model often implicates biological oxidation and underpins reconstructions of marine nutrient concentrations. However, nanoscale petrography indicates that an Fe2+ silicate, greenalite, is a common primary mineral in well-preserved IFs, motivating an alternative depositional model of anoxic ferrous silicate precipitation. It is unclear, however, if Fe2+-rich silicates can produce the Fe isotopic variations in IFs that are well explained by Fe2+ oxidation. To address this question, we constrain the equilibrium Fe isotopic (56Fe/54Fe) fractionation of greenalite and ferrihydrite by determining the iron phonon densities of states for those minerals. We use ab initio density functional theory (DFT + U) calculations and nuclear resonant inelastic X-ray scattering spectroscopy to show that ferrous greenalite should be isotopically lighter than ferrihydrite by ∼1–1.2‰ at equilibrium, and fractionation should scale linearly with increasing Fe3+ content in greenalite. By anchoring ferrihydrite–greenalite mineral pair fractionations to published experimental Fe isotopic fractionations between HFOs and aqueous Fe2+, we show that ferrous greenalite may produce all but the heaviest pre-GOE Fe isotopic compositions and mixed valence greenalites can produce the entire record. Our results suggest that heavy Fe isotope enrichments alone are not diagnostic of primary IF mineralogies, and ferrihydrite and partially oxidized or even purely ferrous greenalite are all viable primary IF mineralogies.

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Minimal biomass deposition in banded iron formations inferred from organic matter and clay relationships

Cited by 14 publications

References 60 publications

Possible link between Earth’s rotation rate and oxygenation

Possible link between Earth’s rotation rate and oxygenation

Fate of organic compounds during transformation of ferrihydrite in iron formations

Isotopic Constraints on the Nature of Primary Precipitates in Archean–Early Paleoproterozoic Iron Formations from Determinations of the Iron Phonon Density of States of Greenalite and 2L- and 6L-Ferrihydrite

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