File:Faulted jaspilite banded iron formation (BIF) (Hamersely Group, Neoarchean to Paleoproterozoic, ~2.47-2.55 Ga; Hamersley Range, Western Australia) 2 (14872822457).jpg
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[edit]_(Hamersely_Group,_Neoarchean_to_Paleoproterozoic,_~2.47-2.55_Ga;_Hamersley_Range,_Western_Australia)_2_(14872822457).jpg&action=edit§ion=1){kind=link}
| Description |
Folded & faulted jaspilite ("tiger iron") from the Precambrian of Australia. Banded iron formations, or BIFs, are unusual, dense sedimentary rocks consisting of alternating layers of iron-rich oxides and iron-rich silicates. Most BIFs are Proterozoic in age (although some are Late Archean), and do not form today - they're “extinct”! Many specific varieties of iron formation are known, and some are given special rock names. For example, jaspilite is an attractive reddish & silvery gray banded rock consisting of hematite, red chert (“jasper”), and specular hematite or magnetite. Because of their age, most BIFs have been around long enough to have been subjected to one or more orogenic (mountain-building) events. As such, most BIFs are folded and/or metamorphosed to varying degrees. BIFs are known from around the world, but some of the most famous & extensive BIF deposits are found in the vicinity of North America’s Lake Superior Basin. Many BIFs have economic concentrations of iron and are mined. BIFs are the most important variety of iron ore on Earth. The attractive BIF shown here is from Western Australia's Hamersley Range, an area famous for its “tiger iron” BIFs. Several stratigraphic units in the Hamersley Group contain banded iron formation (e.g., the Marra Mamba Fe-Fm. & the Brockman Fe-Fm.). The sample here is faulted and folded jaspilite with bands of yellowish-brown “tiger-eye” (= asbestiform quartz having chatoyancy). The Hamersley Group is an upper Neoarchean to lower Paleoproterozoic unit (~2.47 to 2.55 billion years) that outcrops in parts of the Hamersley Range (Pilbara Craton) of Western Australia. |
| Date | |
| Source | Faulted jaspilite banded iron formation (BIF) (Hamersely Group, Neoarchean to Paleoproterozoic, ~2.47-2.55 Ga; Hamersley Range, Western Australia) 2 |
| Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/14872822457 (archive). It was reviewed on 10 October 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| current | 00:33, 10 October 2019 | | 3,008 × 1,921 (5.12 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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