Photoprecipitation and the banded iron-formations — Some quantitative aspects

Braterman, Paul S.; Cairns-Smith, A. G.

doi:10.1007/bf02386463

Cited by 18 publications

(9 citation statements)

References 25 publications

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“…Other estimates place the total amount of Fe(II) photo-oxidized annually at 2.3 × 10 13 mol (Braterman and Cairns-Smith, 1986). These rates are much greater than annual rates inferred during deposition of the largest Archean and Paleoproterozoic BIFs (Pickard, 2002(Pickard, , 2003.…”

Section: Uv Photooxidation Of Fe(ii)mentioning

confidence: 93%

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

Bekker¹,

Krapež²,

Slack³

et al. 2010

Economic Geology

854

494

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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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Section: Uv Photooxidation Of Fe(ii)mentioning

confidence: 93%

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

Bekker¹,

Krapež²,

Slack³

et al. 2010

Economic Geology

854

494

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“…The large inventory of Fe 3+ -bearing oxides (magnetite, hematite) requires an oxidant during BIF genesis, given that all proposed iron sources (riverine, marine hydrothermal) were Fe 2+ . The nature and quantity of this oxidant, however, are not clear and may have included atmospheric O 2 (Cloud 1968), anaerobic photosynthetic Fe 2+ -oxidizing bacteria (Widdel et al 1993), or UV photo-oxidation (Braterman & Cairnssmith 1987), although recent experimental work apparently rules out UV photo-oxidation as a viable mechanism in natural seawater compositions (Konhauser et al 2007). Iron isotope data are available for BIFs from three time periods in the Precambrian: ∼3.7-3.8 Ga, ∼2.5-2.7 Ga, and ∼1.8-1.9 Ga (Figure 5).…”

Section: Banded Iron Formationsmentioning

confidence: 99%

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

Johnson

Beard

Roden

2008

Annu. Rev. Earth Planet. Sci.

419

283

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The largest Fe isotope fractionations occur during redox changes, as well as differences in bonding, but these are expressed only in natural environments in which significant quantities of Fe may be mobilized and separated. At the circumneutral pH of most low-temperature aqueous systems, Fe 2+ aq is the most common species for mobilizing Fe, and Fe 2+ aq has low 56 Fe/ 54 Fe ratios relative to Fe 3+-bearing minerals. Of the variety of abiologic and biologic processes that involve redox or bonding changes, microbial Fe 3+ reduction produces the largest quantities of isotopically distinct Fe by several orders of magnitude relative to abiologic processes and hence plays a major role in producing Fe isotope variations on Earth. In modern Earth, the mass of Fe cycled through redox boundaries is small, but in the Archean it was much larger, reflecting juxtaposition of large inventories of Fe 2+ and Fe 3+. Development of photosynthesis produced large quantities of Fe 3+ and organic carbon that fueled a major expansion in microbial Fe 3+ reduction in the late Archean, perhaps starting as early as ∼3 Ga. The Fe isotope fingerprint of microbial Fe 3+ reduction decreases in the sedimentary rock record between ∼2.4 and 2.2 Ga, reflecting increased bacterial sulfate reduction and a concomitant decrease in the availability of reactive iron to support microbial Fe 3+ reduction. The temporal C, S, and Fe isotope record therefore reflects the interplay of changing microbial metabolisms over Earth's history.

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“…Molecular Hydrogen can also be generated from near UV irradiation of aqueous ferrous hydroxide at pH 6-8 and the presence of banded iron formations in Archean rocks has been cited as evidence that Fe photo-oxidation occurred on the early Earth (Braterman and Cairns-Smith 1987). Chyba and McDonald (1995) described a possible non-atmospheric mechanism by which ultraviolet photolysis could have acted as an energy source for prebiotic organic chemistry.…”

Section: Biological Boundaries For Uv Habitable Zonesmentioning

confidence: 99%

Ultraviolet radiation constraints around the circumstellar habitable zones

Buccino

Lemarchand

Mauas

2006

Icarus

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Ultraviolet radiation is known to inhibit photosynthesis, induce DNA destruction and cause damage to a wide variety of proteins and lipids. In particular, UV radiation between 200-300 nm becomes energetically very damaging to most of the terrestrial biological systems. On the other hand, UV radiation is usually considered one of the most important energy source on the primitive Earth for the synthesis of many biochemical compounds and, therefore, essential for several biogenesis processes. In this work, we use these properties of the UV radiation to define the boundaries of an ultraviolet habitable zone. We also analyze the evolution of the UV habitable zone during the main sequence stage of the star.We apply these criteria to study the UV habitable zone for those extrasolar planetary systems that were observed by the International Ultraviolet Explorer (IUE). We analyze the possibility that extrasolar planets and moons could be suitable for life, according to the UV constrains presented in this work and other accepted criteria of habitability (liquid water, orbital stability, etc.).

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Photoprecipitation and the banded iron-formations — Some quantitative aspects

Cited by 18 publications

References 25 publications

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

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

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

Ultraviolet radiation constraints around the circumstellar habitable zones

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