banded iron formation

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banded iron formation

[¦band·əd ′ī·ərn fȯr‚mā·shən]
(geology)
A sedimentary mineral deposit consisting of alternate silica-rich (chert or quartz) and iron-rich layers formed 2.5-3.5 billion years ago; the major source of iron ore.
References in periodicals archive ?
The deposit is contained in a 2.5-mi outcrop of a banded-iron formation. The formation strikes 5.7-mi on Quest's property.
The mineralization occurs in a shear zone between the Basal Graphitic Formation, a sequence of graphitic quartz-chlorite schists, and the Itabarite banded-iron formation. The shear zone is about 35 m thick in the mine area and consists of a series of iron-rich rocks which form the host for the sulphidic, gold-mineralized horizons.
The researchers, led by Kurt Konhauser of the University of Alberta in Edmonton, analyzed the trace element composition of sedimentary rocks known as banded-iron formations, or BIFs, from dozens of different localities around the world, ranging in age from 3,800 to 550 million years.