SHRIMP U–Pb zircon ages of tuffaceous mudrocks in the Brockman Iron Formation of the Hamersley Range, Western Australia

Pickard, A.L.

doi:10.1046/j.1440-0952.2002.00933.x

Cited by 91 publications

(78 citation statements)

References 22 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: 94%

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

Bekker¹,

Krapež²,

Slack³

et al. 2010

Economic Geology

827

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: 94%

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

Bekker¹,

Krapež²,

Slack³

et al. 2010

Economic Geology

827

494

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“…Xenomorphic quartz occurs in form of microcrystalline chert grains with grain-sizes between 5 to 50 µm in diameter. Assuming similar depositional rates as estimated for other BIF deposits (Trendall et al, 2004, Pickard 20023003), the investigated thin section may represent some 10 2 to 10 3 years of deposition.…”

Section: Investigated Bifmentioning

confidence: 94%

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

130

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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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“…Group of the Pilbara Craton in Western Australia (Isley, 1995;Trendall and Blockley, 2004 (Pickard, 2002), respectively. The consensus view is that the Brockman Iron Formation was deposited on a large, stable, and clastic-starved continental platform, which was only influenced by episodic inputs of fine-grained tuffaceous detritus (e.g., Ewers and Morris, 1981;Gross, 1983).…”

Section: The Largest Ifs By Mass Are Associated With the Brockman Iromentioning

confidence: 99%

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

Konhauser

Planavsky

Hardisty

et al. 2017

Earth-Science Reviews

360

257

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SHRIMP U–Pb zircon ages of tuffaceous mudrocks in the Brockman Iron Formation of the Hamersley Range, Western Australia

Cited by 91 publications

References 22 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

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

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

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