Stable isotope geochemistry of cherts and carbonates from the 2.0 Ga gunflint iron formation: implications for the depositional setting, and the effects of diagenesis and metamorphism

Winter, Bryce L.; Knauth, L. Paul

doi:10.1016/0301-9268(92)90061-r

Cited by 71 publications

(68 citation statements)

References 47 publications

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“…In similar contrast to the majority of data are 13 C-depleted Neoarchaean and early Palaeoproterozoic carbonates associated with banded iron formations that either reflect specific environmental conditions or represent a diagenetic or a metamorphic feature (e.g. Beukes et al 1990;Winter and Knauth 1992;Fallick et al 2011).…”

contrasting

confidence: 47%

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7.6 Enhanced Accumulation of Organic Matter: The Shunga Event

Strauß

Melezhik

Lepland

et al. 2012

Frontiers in Earth Sciences

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contrasting

confidence: 47%

“…Karhu 1993). In contrast, many of the negative d 13 C carb values were measured on iron carbonates (Winter and Knauth 1992) for which a formation from a stratified water body was proposed. This observation points to microbial reworking of organic matter in the anoxic part of a stratified water body, possibly by sulfate-reducing bacteria.…”

mentioning

confidence: 97%

7.6 Enhanced Accumulation of Organic Matter: The Shunga Event

Strauß

Melezhik

Lepland

et al. 2012

Frontiers in Earth Sciences

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“…The most extensive carbon isotope studies of iron formations have been undertaken on the low metamorphic grade deposits of the Transvaal Supergroup in South Africa (e.g., , the Brockman Iron Formation in Western Australia (e.g., Becker andClayton, 1972, Baur et al, 1985), and the ca. 1.88 Ga Biwabik and Gunflint Iron Formations in the United States and Canada (Perry et al, 1973;Winter and Knauth, 1992). In addition, numerous siderite-rich iron formations have been analyzed for carbonate carbon isotopes (e.g., Ohmoto et al, 2004).…”

Section: Traditional Light Stable Isotopesmentioning

confidence: 99%

“…Studies of carbonates from the Brockman Iron Formation (Baur et al, 1985) show that isotopically light carbon and oxygen isotope values correlate with concentrations of iron. The negative carbonate carbon isotope values are commonly interpreted as evidence for direct carbonate (siderite) precipitation from an iron-rich water column, stratified with respect to carbon isotope composition of total dissolved inorganic carbon (e.g., Winter and Knauth, 1992). Although a several per mil stratification in carbon isotope composition of dissolved inorganic carbon is present in the modern ocean (e.g., Kroopnick, 1985), a much smaller gradient is observed in the early Precambrian rock record and is expected under the high pCO 2 conditions required to compensate for a lower solar luminosity (Hotinski et al, 2004).…”

Section: Traditional Light Stable Isotopesmentioning

confidence: 99%

Iron Formation: The Sedimentary Product of a Complex Interplay among Mantle, Tectonic, Oceanic, and Biospheric Processes

Bekker¹,

Krapež²,

Slack³

et al. 2010

Economic Geology

852

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Iron formations are economically important sedimentary rocks that are most common in Precambrian sedimentary successions. Although many aspects of their origin remain unresolved, it is widely accepted that secular changes in the style of their deposition are linked to environmental and geochemical evolution of Earth. Two types of Precambrian iron formations have been recognized with respect to their depositional setting. Algoma-type iron formations are interlayered with or stratigraphically linked to submarine-emplaced volcanic rocks in greenstone belts and, in some cases, with volcanogenic massive sulfide (VMS) deposits. In contrast, larger Superior-type iron formations are developed in passive-margin sedimentary rock successions and generally lack direct relationships with volcanic rocks. The early distinction made between these two iron-formation types, although mimimized by later studies, remains a valid first approximation. Texturally, iron formations were also divided into two groups. Banded iron formation (BIF) is dominant in Archean to earliest Paleoproterozoic successions, whereas granular iron formation (GIF) is much more common in Paleoproterozoic successions. Secular changes in the style of iron-formation deposition, identified more than 20 years ago, have been linked to diverse environmental changes. Geochronologic studies emphasize the episodic nature of the deposition of giant iron formations, as they are coeval with, and genetically linked to, time periods when large igneous provinces (LIPs) were emplaced. Superior-type iron formation first appeared at ca. 2.6 Ga, when construction of large continents changed the heat flux at the core-mantle boundary. From ca. 2.6 to ca. 2.4 Ga, global mafic magmatism culminated in the deposition of giant Superior-type BIF in South Africa, Australia, Brazil, Russia, and Ukraine. The younger BIFs in this age range were deposited during the early stage of a shift from reducing to oxidizing conditions in the ocean-atmosphere system. Counterintuitively, enhanced magmatism at 2.50 to 2.45 Ga may have triggered atmospheric oxidation. After the rise of atmospheric oxygen during the GOE at ca. 2.4 Ga, GIF became abundant in the rock record, compared to the predominance of BIF prior to the Great Oxidation Event (GOE). Iron formations generally disappeared at ca. 1.85 Ga, reappearing at the end of the Neoproterozoic, again tied to periods of intense magmatic activity and also, in this case, to global glaciations, the so-called Snowball Earth events. By the Phanerozoic, marine iron deposition was restricted to local areas of closed to semiclosed basins, where volcanic and hydrothermal activity was extensive (e.g., backarc basins), with ironstones additionally being linked to periods of intense magmatic activity and ocean anoxia.Late Paleoproterozoic iron formations and Paleozoic ironstones were deposited at the redoxcline where biological and nonbiological oxidation occurred. In contrast, older iron formations were deposited in anoxic oceans, where ferrous iron oxid...

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“…Beside magnetite and haematite, siderite is one of the most abundant Fe-bearing minerals in IF. The origin of siderite has been suggested to involve primary precipitation in the water column through the reaction of Fe 2 þ with bicarbonate from seawater as soon as the solubility product of siderite (controlled by the Fe 2 þ and carbonate/bicarbonate concentrations in the ocean water) is exceeded 28,29 . Alternatively, siderite can be formed during the diagenetic (biological or nonbiological), and subsequent metamorphic, oxidation of microbial biomass to CO 2 /bicarbonate coupled to the reduction of Fe(III), followed by reactions of the product Fe 2 þ with the sediment pore-water bicarbonate 30 .…”

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confidence: 99%

Biological carbon precursor to diagenetic siderite with spherical structures in iron formations

et al. 2013

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During deposition of Precambrian iron formation, the combined sedimentation of ferrihydrite and phytoplankton biomass should have facilitated Fe(III) reduction during diagenesis. However, the only evidence for this reaction in iron formations is the iron and carbon isotope values preserved in the authigenic ferrous iron-containing minerals. Here we show experimentally that spheroidal siderite, which is preserved in many iron formation and could have been precursor to rhombohedral or massive siderite, forms by reacting ferrihydrite with glucose (a proxy for microbial biomass) at pressure and temperature conditions typical of diagenesis (170°C and 1.2 kbar). Depending on the abundance of siderite, we found that it is also possible to draw conclusions about the Fe(III):C ratio of the initial ferrihydrite-biomass sediment. Our results suggest that spherical to rhombohedral siderite structures in deepwater, Fe-oxide iron formation can be used as a biosignature for photoferrotrophy, whereas massive siderite reflects high cyanobacterial biomass loading in highly productive shallowwaters.

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Stable isotope geochemistry of cherts and carbonates from the 2.0 Ga gunflint iron formation: implications for the depositional setting, and the effects of diagenesis and metamorphism

Cited by 71 publications

References 47 publications

7.6 Enhanced Accumulation of Organic Matter: The Shunga Event

7.6 Enhanced Accumulation of Organic Matter: The Shunga Event

Iron Formation: The Sedimentary Product of a Complex Interplay among Mantle, Tectonic, Oceanic, and Biospheric Processes

Biological carbon precursor to diagenetic siderite with spherical structures in iron formations

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