The Iron Isotope Fingerprints of Redox and Biogeochemical Cycling in Modern and Ancient Earth

Johnson, Clark M.; Beard, Brian L.; Roden, Eric E.

doi:10.1146/annurev.earth.36.031207.124139

Cited by 419 publications

(302 citation statements)

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“…Carbon isotope evidence suggests life arose before Ϸ3.8 Ga (36, 37) and the presence of several prokaryotic groups in the Archean including sulfate reducers (38), sulfurdisproportionaters (39), iron reducers (15,40), and methanogens (8, 41) have been proposed. Carbon isotopic evidence also indicates that a significant global methane cycle developed by the late Archean, indicating a growing ecological role for methanogens during this eon (42).…”

Section: Resultsmentioning

confidence: 99%

“…An array of tools has traditionally been harnessed, including organic molecules (12) and the isotopic composition of key bioactive elements whose surface geochemical cycles are dominated by the biosphere (13). The transition metals are a recent addition to the latter group, with Fe undergoing the most intensive study (14,15). Fe has advantages and disadvantages in this regard, as the many studies conducted on its isotope system have shown.…”

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confidence: 99%

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A biomarker based on the stable isotopes of nickel

Cameron

Vance

Archer

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

156

166

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The new stable isotope systems of transition metals are increasingly used to understand and quantify the impact of primitive microbial metabolisms on the modern and ancient Earth. To date, little effort has been expended on nickel (Ni) isotopes but there are good reasons to believe that this system may be more straightforward, and useful in this respect, than some others. Here, we present Ni stable isotope data for abiotic terrestrial samples and pure cultures of methanogens. The dataset for rocks reveals little isotopic variability and provides a lithologic baseline for terrestrial Ni isotope studies. In contrast, methanogens assimilate the light isotopes, yielding residual media with a complementary heavy isotopic enrichment. Methanogenesis may have evolved during or before the Archean, when methane could have been key to Earth's early systems. Our data suggest significant potential in Ni stable isotopes for identifying and quantifying methanogenesis on the early planet. Additionally, Ni stable isotope fractionation may well prove to be the fundamental unambiguous trace metal biomarker for methanogens.biological fractionation ͉ early life ͉ methanogens ͉ trace metal L ife has had a profound impact on the surface of the Earth, with perhaps the most obvious expression being the advent of oxygenic photosynthesis leading to the evolution of an oxidised atmosphere and oceans (1, 2). However, the microorganisms and metabolisms mediating oxygenic photosynthesis probably evolved relatively late in the Archean (3-5) and other metabolisms, such as methanogenesis, likely dominated both the early history of the biosphere itself (6-8) and the surface chemistry of the planet (9, 10). For example, atmospheric methane has been suggested as the dominant greenhouse gas before 2.3 Ga, before the evolution of oxic conditions (10). This inference is based on models of solar luminosity, atmospheric photochemistry and Archean microbial ecology, but little is known about the actual timing of the evolution of methanogens or methanogenesis as a metabolism. Phylogenetic studies indicate methanogens are deeply rooted in the tree of life (6,8,11), but this approach relies on biological evidence to constrain the timing of evolutionary events.In the investigation of the history of life on Earth, isotopic and chemical biomarkers serve both to calibrate time in phylogenetic trees and to document the impact of the biosphere on the physical world. An array of tools has traditionally been harnessed, including organic molecules (12) and the isotopic composition of key bioactive elements whose surface geochemical cycles are dominated by the biosphere (13). The transition metals are a recent addition to the latter group, with Fe undergoing the most intensive study (14,15). Fe has advantages and disadvantages in this regard, as the many studies conducted on its isotope system have shown. The ubiquitous role of Fe in the biosphere makes its isotopes a key system to study, though other isotope systems such as Se (16) and Cu (17) may also be promising....

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

A biomarker based on the stable isotopes of nickel

Cameron

Vance

Archer

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

156

166

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“…25). Measurements of DFe redox speciation (DFe II and total DFe from which DFe III can be computed) during the BGH cruise provide the opportunity to evaluate the effect of the iron redox state on its isotope signature in the open ocean.…”

Section: Discussionmentioning

confidence: 99%

Iron isotopes reveal distinct dissolved iron sources and pathways in the intermediate versus deep Southern Ocean

Abadie

Lacan

Radic

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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As an essential micronutrient, iron plays a key role in oceanic biogeochemistry. It is therefore linked to the global carbon cycle and climate. Here, we report a dissolved iron (DFe) isotope section in the South Atlantic and Southern Ocean. Throughout the section, a striking DFe isotope minimum (light iron) is observed at intermediate depths (200–1,300 m), contrasting with heavier isotopic composition in deep waters. This unambiguously demonstrates distinct DFe sources and processes dominating the iron cycle in the intermediate and deep layers, a feature impossible to see with only iron concentration data largely used thus far in chemical oceanography. At intermediate depths, the data suggest that the dominant DFe sources are linked to organic matter remineralization, either in the water column or at continental margins. In deeper layers, however, abiotic non-reductive release of Fe (desorption, dissolution) from particulate iron—notably lithogenic—likely dominates. These results go against the common but oversimplified view that remineralization of organic matter is the major pathway releasing DFe throughout the water column in the open ocean. They suggest that the oceanic iron cycle, and therefore oceanic primary production and climate, could be more sensitive than previously thought to continental erosion (providing lithogenic particles to the ocean), particle transport within the ocean, dissolved/particle interactions, and deep water upwelling. These processes could also impact the cycles of other elements, including nutrients.

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“…Isotopic compositions of iron and sulphur in pyrites from sedimentary rocks have been proposed as potential proxies to assess the redox state of ancient oceans (Rouxel et al, 2005;Reinhard et al, 2009;Marin-Carbonne et al, 2014), the oxygen outgrowth in the atmosphere (Catling and Claire, 2005;Ohmoto et al, 2006) and early microbial metabolisms (Johnson et al, 2008). Moreover, trace metals incorporated in pyrite have been recognised as proxies for ancient ocean chemistry (Large et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Nickel accelerates pyrite nucleation at ambient temperature

Morin¹,

Noël²,

Menguy³

et al. 2017

Geochem. Persp. Let.

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Chemical and isotopic compositions of pyrites are used as biogeochemical tracers in Archean to modern sediments. Moreover, pyrite formation from monosulphide precursors has been proposed to be involved in prebiotic chemistry. However, the factors controlling pyrite formation and distribution in the sedimentary record are incompletely understood. Here, we show that Ni 2+ ions accelerate ~5 times the nucleation of pyrite at ambient temperature. Using Fe and Ni K-edge EXAFS and TEM-EDXS we demonstrate that Ni(II) is directly involved in the nucleation of pyrite synthesised by reacting Fe(III) with Na 2 S in the presence of aqueous Ni(II) impurity. Initial formation of a Ni-enriched pyrite core is followed by overgrowth of a Ni-depleted pyrite shell, leading to compositional zoning of the Fe 1-x Ni x S 2 nanocrystals (x = 0.05 to 0.0004). The molar Ni/Fe ratio in the final aqueous solution was then 2000 times lower than the starting ratio of 0.01. This enhanced and accelerated trapping of Ni by pyrite could be of prime importance in controlling Ni concentration in the ocean during early diagenesis of marine sediments, and could thus have important implications for interpreting abundances of Ni and pyrite in the sedimentary record. In addition, acceleration of pyrite nucleation in the presence of nickel could help understanding the role of Fe-Ni sulphides in catalysing potential prebiotic reactions.

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The Iron Isotope Fingerprints of Redox and Biogeochemical Cycling in Modern and Ancient Earth

Cited by 419 publications

References 144 publications

A biomarker based on the stable isotopes of nickel

A biomarker based on the stable isotopes of nickel

Iron isotopes reveal distinct dissolved iron sources and pathways in the intermediate versus deep Southern Ocean

Nickel accelerates pyrite nucleation at ambient temperature

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