Editing Banded iron formation (section)

==Occurrence==
[[File:Bif in time.jpg|thumb|Abundance of banded iron formation in the geologic record. Color indicates dominant type. Red = older Archean formations; green = Greater Gondwana formations; blue = granular iron formations; black = [[Snowball Earth]] formations. Adapted from Trendall 2002.]]
{{Location map many
| Earth
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| caption     = Location of occurrences. Color indicates dominant type. Light yellow = older Archean formations; dark yellow = Greater Gondwana formations; brown = granular iron formations; red = Snowball Earth formations.
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| link11       =  Hamersley Range
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| link17       =  Isua Iron Mine
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Banded iron formations are almost exclusively [[Precambrian]] in age, with most deposits dating to the late Archean (2800–2500 Ma) with a secondary peak of deposition in the [[Orosirian]] [[Period (geology)|period]] of the [[Paleoproterozoic]] (1850 Ma). Minor amounts were deposited in the early Archean and in the [[Neoproterozoic]] (750 Ma).<ref name="trendall-blockley-2004"/><ref name="condie-2015"/> The youngest known banded iron formation is an [[Early Cambrian]] formation in western China.<ref name="li-etal-2018"/> Because the processes by which BIFs are formed appear to be restricted to early geologic time, and may reflect unique conditions of the Precambrian world, they have been intensively studied by geologists.<ref name="trendall-blockley-2004"/><ref name="condie-2015"/>

Banded iron formations are found worldwide, in every [[Continental Shield|continental shield]] of every continent. The oldest BIFs are associated with [[greenstone belt]]s and include the BIFs of the [[Isua Greenstone Belt]], the oldest known, which have an estimated age of 3700 to 3800 Ma.<ref name="trendall-blockley-2004"/><ref name="czaja-etal-2013">{{cite journal |last1=Czaja |first1=Andrew D. |last2=Johnson |first2=Clark M. |last3=Beard |first3=Brian L. |last4=Roden |first4=Eric E. |last5=Li |first5=Weiqiang |last6=Moorbath |first6=Stephen |title=Biological Fe oxidation controlled deposition of banded iron formation in the ca. 3770Ma Isua Supracrustal Belt (West Greenland) |journal=Earth and Planetary Science Letters |date=February 2013 |volume=363 |pages=192–203 |doi=10.1016/j.epsl.2012.12.025|bibcode=2013E&PSL.363..192C }}</ref> The [[Temagami Greenstone Belt|Temagami]]<ref name="AHI">{{cite journal|id=AFRI 31M04SW0091|title=Geological and electromagnetic (VLP) surveys on part of Strathy-Cassels Group|last=Alexander|first=D.R.|publisher=[[Hollinger Mines Limited]]|location=[[Timmins]], [[Ontario]]|pages=3, 4, 9|date=1977-11-21}}</ref> banded iron deposits formed over a 50-million-year period, from 2736 to 2687 Ma, and reached a thickness of {{convert|60|meters|feet|abbr=off}}.<ref name="amnh-2020">{{cite web |title=Ontario banded iron formation |url=https://www.amnh.org/exhibitions/permanent/planet-earth/how-has-the-earth-evolved/a-special-planet/how-do-we-know-about-the-early-atmosphere/ontario-banded-iron-formation |website=American Museum of Natural History |access-date=17 June 2020}}</ref> Other examples of early Archean BIFs are found in the [[Abitibi greenstone belt]]s, the greenstone belts of the [[Yilgarn]] and [[Pilbara craton]]s, the [[Baltic shield]], and the cratons of the [[Amazonian craton|Amazon]], [[North China craton|north China]], and [[Kalahari craton|south]] and [[West African craton|west]] Africa.<ref name="trendall-blockley-2004"/>

The most extensive banded iron formations belong to what A.F. Trendall calls the Great [[Gondwana]] BIFs. These are late Archean in age and are not associated with greenstone belts. They are relatively undeformed and form extensive topographic plateaus,<ref name="trendall-2002"/> such as the [[Hamersley Range]].<ref name="henrietta.liswa.wa.gov.au">MacLeod, W. N. (1966) [http://henrietta.liswa.wa.gov.au/record=b2251313~S2 The geology and iron deposits of the Hamersley Range area. Bulletin] {{Webarchive|url=https://web.archive.org/web/20160304040152/http://henrietta.liswa.wa.gov.au/record=b2251313~S2 |date=4 March 2016 }} (Geological Survey of Western Australia), No. 117</ref><ref name="Geology">{{cite web |url=http://www.riotintoironore.com/ENG/operations/497_geology.asp |title=Geology |publisher=Rio Tinto Iron Ore |access-date=2012-08-07 |url-status=dead |archive-url=https://web.archive.org/web/20121023034150/http://www.riotintoironore.com/ENG/operations/497_geology.asp |archive-date=2012-10-23 }}</ref><ref name="Iron2002" /> The banded iron formations here were deposited from 2470 to 2450 Ma and are the thickest and most extensive in the world,<ref name="condie-2015"/><ref name="wam-2014">{{cite web |title=Banded Iron Formation |url=http://museum.wa.gov.au/research/collections/earth-and-planetary-sciences/rock-collection/banded-iron-formation |publisher=Western Australian Museum |access-date=17 June 2020}}</ref> with a maximum thickness in excess of {{convert|900|meters|feet|abbr=off}}.<ref name="gole-klein-1981"/> Similar BIFs are found in the [[Carajás Formation]] of the Amazon craton, the [[Cauê Itabirite]] of the [[São Francisco craton]], the [[Kuruman Iron Formation]] and [[Penge Iron Formation]] of South Africa, and the [[Mulaingiri Formation]] of [[Indian Shield|India]].<ref name="trendall-blockley-2004"/>

Paleoproterozoic banded iron formations are found in the [[Iron Range]] and other parts of the [[Canadian Shield]].<ref name="trendall-blockley-2004"/>  The Iron Range is a group of four major deposits: the [[Mesabi Range]], the [[Vermilion Range (Minnesota)|Vermilion Range]], the [[Gunflint Range]], and the [[Cuyuna Range]]. All are part of the [[Animikie Group]] and were deposited between 2500 and 1800 Ma.<ref name=af>{{cite journal|title=Three Great Basins of Precambrian Banded Iron Formation Deposition: A Systematic Comparison|author=Trendall, A. F|journal=Geological Society of America Bulletin|
doi=10.1130/0016-7606(1968)79[1527:TGBOPB]2.0.CO;2|year=1968|volume=79|issue=11|page=1527|bibcode = 1968GSAB...79.1527T }}</ref> These BIFs are predominantly granular iron formations.<ref name="trendall-blockley-2004"/>

Neoproterozoic banded iron formations include the Urucum in Brazil, Rapitan in the [[Yukon]], and the Damara Belt in southern Africa.<ref name="trendall-blockley-2004"/> They are relatively limited in size, with horizontal extents not more than a few tens of kilometers and thicknesses not more than about {{convert|10|meters|feet|abbr=off}}.<ref name="ilyin-2009"/> These are widely thought to have been deposited under unusual anoxic oceanic conditions associated with the "[[Snowball Earth]]."<ref name="trendall-2002"/>