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Earth and Space Sciences · 术语表

什么是 Banded iron formation？

Definition 26.7 High School Earth and Space Sciences · 第 26 章 — The Early Earth and Its Atmosphere

A banded iron formation is a sedimentary rock of thin alternating layers of iron oxides, such as hematite, and of chert, a fine-grained silica poor in iron. Almost all are older than 1.8 billion years.

How a banded iron formation forms (schematic, not to scale): iron dissolved in the deep water, which holds no oxygen, rises into the sunlit sea, where the oxygen made by cyanobacteria turns it into iron(III), which settles. Layers rich in iron alternate with layers of chert.
How a banded iron formation forms (schematic, not to scale): iron dissolved in the deep water, which holds no oxygen, rises into the sunlit sea, where the oxygen made by cyanobacteria turns it into iron(III), which settles. Layers rich in iron alternate with layers of chert.
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Definition 18.6 University Earth and Space Sciences — Year 2 · 第 18 章 — The Precambrian Earth

A banded iron formation (BIF) is a chemical sediment of thin alternating layers of iron oxides — hematite, magnetite — and of chert. It precipitates from sea water that carries dissolved iron(II), when that iron is oxidised to insoluble iron(III); it therefore needs a deep ocean without oxygen, a supply of iron, and an oxidant where the iron is deposited.

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