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30 August 2013

Friday fold: Archean BIF from Montana

My NOVA colleague Shelley Jaye brought this gorgeous banded iron formation fold back from the Archean of Montana: Gorgeous to think about what this rock represents: (1) an anoxic atmosphere, a world where iron was able to dissolve in seawater; (2) some addition of oxygen, causing the iron to precipitate out as iron oxide minerals, (3) burial to some enormous depth where rocks behave gooey-like, (4) tectonic stresses that caused …


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