Alternating Si and Fe deposition caused by temperature fluctuations in Precambrian oceans

Posth, Nicole R.; Hegler, Florian; Konhauser, Kurt O.; Kappler, Andreas

doi:10.1038/ngeo306

Cited by 146 publications

(83 citation statements)

References 39 publications

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“…Experimental evidence suggests that low temperatures indeed promote Si precipitation over microbial Fe 2 þ transformation and vice versa 29 . We suggest that cyclic blooming of anoxygenic photoferrotrophy, related to Fe 2 þ oxidation followed by rapid encrustation and fossilization by Fe 3 þ , is key to BIF formation and banding (Fig.…”

Section: Discussionmentioning

confidence: 99%

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Fossilized iron bacteria reveal a pathway to the biological origin of banded iron formation

et al. 2013

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Debates on the formation of banded iron formations in ancient ferruginous oceans are dominated by a dichotomy between abiotic and biotic iron cycling. This is fuelled by difficulties in unravelling the exact processes involved in their formation. Here we provide fossil environmental evidence for anoxygenic photoferrotrophic deposition of analogue banded iron rocks in shallow marine waters associated with an Early Quaternary hydrothermal vent field on Milos Island, Greece. Trace metal, major and rare earth elemental compositions suggest that the deposited rocks closely resemble banded iron formations of Precambrian origin. Well-preserved microbial fossils in combination with chemical data imply that band formation was linked to periodic massive encrustation of anoxygenic phototrophic biofilms by iron oxyhydroxide alternating with abiotic silica precipitation. The data implicate cyclic anoxygenic photoferrotrophy and their fossilization mechanisms in the construction of microskeletal fabrics that result in the formation of characteristic banded iron formation bands of varying silica and iron oxide ratios.

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Section: Discussionmentioning

confidence: 99%

“…Conveniently, the scale of their activity could have been coupled to increased volcanic release of iron and climatic fluctuations. Microbial growth cycles are universally affected by changes in environmental conditions-including nutrient availability and temperatures 28,29 .…”

Section: Discussionmentioning

confidence: 99%

Fossilized iron bacteria reveal a pathway to the biological origin of banded iron formation

et al. 2013

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“…As most iron formations, particularly those of Archean age, reflect offshore, commonly basinal deposition, silica precipitation was probably not forced by evaporation. Posth et al (2008) have suggested that the alternating Si and Fe deposition in BIFs is caused by temperature fluctuations in the surface waters which slow down microbial iron mineral formation but increase abiotic silica precipitation. While seasonal fluctuations in saturation state might drive silica precipitation in shallow water, it is not clear that this mechanism would work in the open marine settings where Archean iron formations actually accumulated.…”

Section: Silica Cycling and Si Isotopes In Precambrian Oceansmentioning

confidence: 99%

Si isotope variability in Proterozoic cherts

Chakrabarti

Knoll

Jacobsen

et al. 2012

Geochimica et Cosmochimica Acta

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We report Si-isotopic compositions of 75 sedimentologically and petrographically characterized chert samples with ages ranging from $2600 to 750 Ma using multi-collector inductively coupled plasma mass spectrometry. d 30 Si values of the cherts analyzed in this study show a $7& range, from À4.29 to +2.85. This variability can be explained in part by (1) simple mixing of silica derived from continental (higher d 30 Si) and hydrothermal (lower d 30 Si) sources, (2) multiple mechanisms of silica precipitation and (3) Rayleigh-type fractionations within pore waters of individual basins.We observe $3& variation in peritidal cherts from a single Neoproterozoic sedimentary basin (Spitsbergen). This variation can be explained by Rayleigh-type fractionation during precipitation from silica-saturated porewaters. In some samples, postdissolution and reprecipitation of silica could have added to this effect. Our data also indicate that peritidal cherts are enriched in the heavier isotopes of Si whereas basinal cherts associated with banded iron formations (BIF) show lower d 30 Si. This difference could partly be due to Si being derived from hydrothermal sources in BIFs. We postulate that the difference in d 30 Si between non-BIF and BIF cherts is consistent with the contrasting genesis of these deposits. Low d 30 Si in BIF is consistent with laboratory experiments showing that silica adsorbed onto Fe-hydroxide particles preferentially incorporates lighter Si isotopes.Despite large intrabasinal variation and environmental differences, the data show a clear pattern of secular variation. Low d 30 Si in Archean cherts is consistent with a dominantly hydrothermal source of silica to the oceans at that time. The monotonically increasing d 30 Si from 3.8 to 1.5 Ga appears to reflect a general increase in continental versus hydrothermal sources of Si in seawater, as well as the preferential removal of lighter Si isotopes during silica precipitation in iron-associated cherts from silica-saturated seawater. The highest d 30 Si values are observed in 1.5 Ga peritidal cherts; in part, these enriched values could reflect increasing sequestration of light silica during soil-forming processes, thus, delivering relatively heavy dissolved silica to the oceans from continental sources. The causes behind the reversal in trend towards lower d 30 Si in cherts younger than 1.5 Ga old are less clear. Cherts deposited 1800-1900 Ma are especially low d 30 Si, a possible indication of transiently strong hydrothermal input at this time.

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“…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(Posth et al, , 2010. One potential issue with the suggestion of photoferrotrophy in the Archaean is that a lack of an early ozone layer would have allowed high incoming UV radiation in the photic zone where photoferrotrophs are presumed to have resided.…”

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confidence: 99%

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

Konhauser

Planavsky

Hardisty

et al. 2017

Earth-Science Reviews

367

257

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Alternating Si and Fe deposition caused by temperature fluctuations in Precambrian oceans

Cited by 146 publications

References 39 publications

Fossilized iron bacteria reveal a pathway to the biological origin of banded iron formation

Fossilized iron bacteria reveal a pathway to the biological origin of banded iron formation

Si isotope variability in Proterozoic cherts

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

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