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Mixed, silicate–carbonate–sulfide facies, banded iron formations with elevated detrital components were deposited in the Northern Black Hills during middle Paleoproterozoic time, between 2.012 and 1.974Ga (Homestake Iron Formation and equivalents) and at ≤1.887Ga (Rochford Iron Formation). These iron formations, deposited atop shales and basalts in intracontinental rifted basins separated in time...
Banded iron formations (BIFs) were deposited in the Black Hills, South Dakota, prior to and after the first main oxygenation of the atmosphere at ∼2.4–2.2Ga. The oldest, Neoarchean horizon (Nemo Iron Formation) is an oxide-facies, detritus-free BIF deposited at ∼2.9–2.6Ga, in association with mafic phyllite. These BIFs show rare earth and yttrium elemental (REY) signatures typical of ambient seawater,...
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