The Oceans; A Possible Source of Iron in Iron-Formations

Holland, Heinrich

doi:10.2113/gsecongeo.68.7.1169

Cited by 356 publications

(164 citation statements)

References 11 publications

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“…We assume that the deep ocean is Fe 2+ -buffered [92][93][94][95][96] . Conceptually, this means that hydrothermal sulphide introduced to the ocean through seawater-basalt interaction is negligible due to near vent iron sulphide precipitation, and is thus assumed not to participate in the isotope mass balance of oceanic sulphur.…”

Section: Supplementary Information Researchmentioning

confidence: 99%

Long-term sedimentary recycling of rare sulphur isotope anomalies

Reinhard

Planavsky

Lyons

2013

Nature

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Sulphur Isotope Database:An extensive sulphur isotope database was used in the construction of Main Text Figure 1. These data were compiled from primary references 1-37 , although in some cases age constraints for certain units were obtained from other sources [38][39][40][41] or estimated. For Main Text Figure 1b, we calculated the cumulative average ∆ 33 S value for all samples up to each year of publication. The average values reported here thus include some contribution from sulphate minerals. However, the overwhelming majority of the data are sulphide mineral phases, and given that most sulphate data are characterized by negative ∆ 33 S values their inclusion will largely attenuate the pattern emphasized here, rendering our argument conservative. Furthermore, the overall effect of their inclusion is quite small (Fig. S1a,b). We also examined the effect of filtering data from analyses made via secondary ion mass spectrometry (SIMS) and analyses of macroscopic pyrite textures, which are not likely to be representative of bulk weathering crust, but again note that the basic pattern remains unchanged (Fig. S1a,b).The mean ∆ 33 S values shown in Fig. 1 are presented as unweighted averages. We consider this approach qualitatively justified, in that the database is composed largely of fine-grained siliciclastic sedimentary rocks that are relatively organic carbon and sulphur rich. Such rocks will not only be, on average, the most sulphur-enriched phases of the crust, but they will also likely hold the majority of the weathering sulphur reservoir at Earth's surface. Nonetheless, it is important to consider the possibility that there is a bias related to systematic relationships between the sulphur content of sedimentary rocks and their ∆ 33 S value. For this purpose, we compiled the available sulphur concentration data for the units within the isotope database and performed concentration-weighted statistical analyses.There does not appear to be any systematic relationship between rare sulphur isotope composition and sulphur content within the database (Fig. S2a). In addition, the cumulative unweighted average is nearly indistinguishable from the concentration-weighted average within this subset of the database (Fig. S2a,b). When the evolution of the overall ∆ 33 S value of the database is concentration-weighted, it shows a generally similar pattern through time to that of the overall mean values (Fig. S2b). Indeed, the mean ∆ 33 S value when weighted by concentration is more positive than the unweighted mean for a given population from the database. We stress the caveat that many of the published rare sulphur isotope datasets do not contain sulphur concentration data, so unfortunately this analysis cannot be performed on the entire database. However, the coupled isotope and concentration data represent well over 500 samples that range in sulphur content over three orders of magnitude. These considerations lead us to conclude that the pattern expressed in the overall mean ∆ 33 S values through time is robust and is ...

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Section: Supplementary Information Researchmentioning

confidence: 99%

Long-term sedimentary recycling of rare sulphur isotope anomalies

Reinhard

Planavsky

Lyons

2013

Nature

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“…Konhauser et al, 2002;Kappler et al, 2005) or atmospheric oxygen (e.g. Holland, 1973;Drever, 1974;Ehrenreich and Widdel, 1994;Kaufman et al, 2007). In the absence of silica-secreting organisms, the Si concentration in the Precambrian ocean could have been as high as 110 ppm, the saturation state of amorphous silica (Maliva et al, 2005).…”

Section: Significance Of Bulk Fe and Si Isotope Composition In The Olmentioning

confidence: 99%

Micro-scale tracing of Fe and Si isotope signatures in banded iron formation using femtosecond laser ablation

Steinhoefel

Horn

Blanckenburg

2009

Geochimica et Cosmochimica Acta

136

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We have detected micrometer-scale differences in Fe and Si stable isotope ratios between coexisting minerals and between layers of banded iron formation (BIF) using an UV femtosecond laser ablation system connected to a MC-ICP-MS. In the magnetite-carbonate-chert BIF from the Archean Old Wanderer Formation in the Shurugwi Greenstone Belt (Zimbabwe), magnetite shows neither intra-nor inter-layer trends giving overall uniform  56 Fe values of ~0.9‰, but exhibits intra-crystal zonation. Bulk iron carbonates are also relatively uniform at near-zero values, however their individual  56 Fe value is highly composition-dependent: both siderite and ankerite and mixtures between both are present, and  56 Fe end member values are 0.4‰ for siderite and -0.7‰ for ankerite. The data suggest either an early diagenetic origin of magnetite and iron carbonates by the reaction of organic matter with ferric oxyhydroxides catalysed by Fe(III)-reducing bacteria; or more likely an abiotic reaction of organic carbon and Fe(III) during low-grade metamorphism. Si isotope composition of the Old Wanderer BIF also shows significant variations with  30 Si values that range between -1.0 and -2.6‰ for bulk layers. These isotope compositions suggest rapid precipitation of the silicate phases from hydrothermal-rich waters. Interestingly, Fe and Si isotope compositions of bulk layers are covariant and are interpreted as largely primary signatures. Moreover, the changes of Fe and Si isotope signatures between bulk layers directly reflect the upwelling dynamics of hydrothermal-rich water which govern the rates of Fe and Si precipitation and therefore also the development of layering. During periods of low hydrothermal activity, precipitation of only small amounts of ferric oxyhydroxide was followed by complete reduction with organic carbon during diagenesis resulting in carbonate-chert layers. During periods of intensive hydrothermal activity, precipitation rates of ferric oxyhydroxide were high, and subsequent diagenesis triggered only partial reduction, forming magnetite-carbonate-chert layers. We are confident that our micro-analytical technique is able to detect both the solute flux history into the sedimentary BIF precursor, and the BIF's diagenetic history from the comparison between coexisting minerals and their predicted fractionation factors.

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“…Cloud [35] and Holland [36] ¢rst suggested that iron and silica, the main components of BIFs, were derived from seawater. This concept is now generally accepted, although some disagreement still exists as to the ultimate origin of these components.…”

Section: The Origin Of Bifmentioning

confidence: 99%

“…This concept is now generally accepted, although some disagreement still exists as to the ultimate origin of these components. Holland [36] suggested that Fe 2þ could be provided either from terrestrial weathering in an anoxic environment, volcanic emanations into the ocean, or bottom waters. Low-temperature weathering and high-temperature alteration [37] of the ocean £oor could also be sources of iron.…”

Section: The Origin Of Bifmentioning

confidence: 99%

Barite, BIFs and bugs: evidence for the evolution of the Earth’s early hydrosphere

Huston

Logan

2004

Earth and Planetary Science Letters

284

142

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The presence of relatively abundant bedded sulfate deposits before 3.2 Ga and after 1.8 Ga, the peak in iron formation abundance between 3.2 and 1.8 Ga, and the aqueous geochemistry of sulfur and iron together suggest that the redox state and the abundances of sulfur and iron in the hydrosphere varied widely during the Archean and Proterozoic. We propose a layered hydrosphere prior to 3.2 Ga in which sulfate produced by atmospheric photolytic reactions was enriched in an upper layer, whereas the underlying layer was reduced and sulfur-poor. Between 3.2 and 2.4 Ga, sulfate reduction removed sulfate from the upper layer, producing broadly uniform, reduced, sulfur-poor and iron-rich oceans. As a result of increasing atmospheric oxygenation around 2.4 Ga, the flux of sulfate into the hydrosphere by oxidative weathering was greatly enhanced, producing layered oceans, with sulfate-enriched, ironpoor surface waters and reduced, sulfur-poor and iron-rich bottom waters. The rate at which this process proceeded varied between basins depending on the size and local environment of the basin. By 1.8 Ga, the hydrosphere was relatively sulfate-rich and iron-poor throughout. Variations in sulfur and iron abundances suggest that the redox state of the oceans was buffered by iron before 2.4 Ga and by sulfur after 1.8 Ga. Crown

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The Oceans; A Possible Source of Iron in Iron-Formations

Cited by 356 publications

References 11 publications

Long-term sedimentary recycling of rare sulphur isotope anomalies

Long-term sedimentary recycling of rare sulphur isotope anomalies

Micro-scale tracing of Fe and Si isotope signatures in banded iron formation using femtosecond laser ablation

Barite, BIFs and bugs: evidence for the evolution of the Earth’s early hydrosphere

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