File:Jaspilite banded iron formation (BIF) (Ironwood Iron-Formation, Paleoproterozoic, 1.874-1.878 Ga; Wakefield, Gogebic County, Upper Peninsula of Michigan, USA) (14872710978).jpg
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[edit]DescriptionJaspilite banded iron formation (BIF) (Ironwood Iron-Formation, Paleoproterozoic, 1.874-1.878 Ga; Wakefield, Gogebic County, Upper Peninsula of Michigan, USA) (14872710978).jpg |
Jaspilite from the Precambrian of Michigan, USA. (cut surface; field of view 9 cm across) 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 BIF shown above is from the Ironwood Iron-Formation of northern Michigan. BIFs are relatively widespread in Michigan’s Upper Peninsula (UP). The Ironwood Iron-Formation outcrops in the western UP’s Gogebic Iron Range. Its layers have been steeply tilted by the Penokean Orogeny (~1.85 billion years) and by mid-continent rifting (~1.10 billion years). The rock shown above is a classic example of jaspilite. It consists of interbedded magnetite-rich layers (gray) (Fe3O4) and hematite-rich layers (dark red) and bright red hematitic metachert layers (“jasper”). Stratigraphy: Ironwood Iron-Formation, upper Paleoproterozoic, ~1.874-1.878 Ga Locality: Wakefield, western Gogebic County, far-western Upper Peninsula of Michigan, USA |
Date | |
Source | Jaspilite banded iron formation (BIF) (Ironwood Iron-Formation, Paleoproterozoic, 1.874-1.878 Ga; Wakefield, Gogebic County, Upper Peninsula of Michigan, USA) |
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@N05/14872710978 (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. |
10 October 2019
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current | 00:33, 10 October 2019 | 1,440 × 1,060 (2.15 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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Pixel composition | RGB |
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Orientation | Normal |
Horizontal resolution | 360 dpi |
Vertical resolution | 360 dpi |
Software used | Adobe Photoshop CS2 Macintosh |
File change date and time | 23:20, 27 August 2014 |
Color space | Uncalibrated |
Image width | 1,440 px |
Image height | 1,060 px |
Date and time of digitizing | 19:19, 27 August 2014 |
Date metadata was last modified | 19:20, 27 August 2014 |