Siliciclastic‐hosted iron‐formations in the early Archaean Barberton and Pilbara sequences

Eriksson, Kenneth A.

doi:10.1080/00167618308729271

Cited by 28 publications

(7 citation statements)

References 31 publications

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“…Two thin jaspilitic BIF units interbedded with ferruginous shale also occur at the top of fining-upward sequences within the ca. 3.23 Ga Moodies Group and in association with syndepositional volcanic rocks (Eriksson, 1983). The lower one, within the Clutha Formation, is interlayered with air-fall tuff, accretionary lapilli, and a metabasaltic flow, whereas the upper one, in the Joe's Luck Formation, is immediately above the basaltic unit (Heubeck and Lowe, 1994).…”

Section: Paleoarchean Bifsmentioning

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

832

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: Paleoarchean Bifsmentioning

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

832

494

View full text Add to dashboard Cite

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“…While it is certainly possible that some smaller iron formations were deposited in lacustrine settings (Eriksson, 1983;Beukes, 1984), multiple lines of evidence indicate that the Superior-type iron formations were deposited in open marine settings, primarily on continental margins. One line of evidence is their close association with shallow marine deposits such as tidally influenced quartzarenites (Ojakangas, 1983;Simonson, 1984).…”

Section: Lacustrine/nonmarine Depositsmentioning

confidence: 97%

“…Eriksson (1983) suggested that iron formations were deposited wherever nothing else was accumulating fast enough to dilute it. This is consistent with the fact that many iron formations appear to have accumulated in sediment-starved settings (Simonson and Hassler, 1996).…”

Section: High Primary Silica Contentmentioning

confidence: 98%

Origin and evolution of large Precambrian iron formations

Simonson¹

2003

Extreme Depositional Environments: Mega End Members in Geologic Time

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Collectively, iron formations represent Earth's preeminent supracrustal repository of iron. The largest iron formations were deposited in the Late Archean and Paleoproterozoic via a unique confluence of atmospheric, hydrospheric, lithospheric, and biospheric conditions. Understanding these conditions better requires a deeper appreciation of the sedimentary features of iron formations. Many researchers refer to them collectively as banded iron formations or the acronym BIF, but banding is not always well developed. Iron formations that lack thin banding consist of sand-sized detritus and are cross-bedded, and should be referred to as granular iron formations or the acronym GIF. The mineralogical and textural heterogeneity of iron formations is also underappreciated. The iron in many iron formations resides in siderite or iron-rich silicates rather than oxides. This implies that iron formations did not all form from local releases of oxygen by photosynthetic microbes. Both the heterogeneity of iron formations and the variety of different rock types with which they are associated indicate that large iron formations are not products of a particular depositional setting, such as evaporites. They owe their existence to a combination of: (1) copious masses of dissolved iron supplied by deep-sea hydrothermal systems, (2) the appearance of large continental shelves to serve as depositional repositories, and (3) a stratified ocean with a chemistry suitable for connecting the two. The mechanisms of precipitation are still unclear, but it probably took place along regional chemoclines. Evidence of microbial involvement is increasing. The largest iron formations of all are those of the Hamersley and Transvaal Basins in western Australia and South Africa, respectively, and they may have originally formed a single huge unit.

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“…Seafloor hydrothermal systems (fumaroles) probably enriched Archaean seawater in iron, with sulphidic ironformations forming beneath the pycnocline (Veizer, 1983) and oxidic iron-formations above this level where photosynthetic productivity was applied (Eriksson et al, 1997). In the absence of planktonic sediment particles, Archaean brain-outQ of iron minerals probably provided an equivalent to PhanerozoicModern pelagic starved basin deposits (Eriksson, 1983).…”

Section: Greenstone Belt-type Sedimentation Patterns (C 37-27 Ga)mentioning

confidence: 99%