- journal_title：Geology
- Contributor：K.A. Evans ; T.C. McCuaig ; D. Leach ; T. Angerer ; S.G. Hagemann
- Publisher：Geological Society of America
- Date：2013-02-01
- Format：text/html
- Language：en
- Identifier：10.1130/G33244.1
- journal_abbrev：Geology
- issn：0091-7613
- volume：41
- issue：2
- firstpage：99
- section：Articles
d="p-1">Banded iron formations (BIF) are the protolith to most of the world’s largest iron ore deposits. Previous hypogene genetic models for Paleoproterozoic “Lake Superior” BIF-hosted deposits invoke upwards, down-temperature flow of basinal brines via complex silica and carbonate precipitation/dissolution processes. Such models are challenged by the necessary SiO2 removal. Thermodynamic and mass balance constraints are used to refine conceptual models of the formation of BIF-hosted iron ore. These constraints, plus existing isotope and halogen ratio evidence, are consistent with removal of silica by down- or up-directed infiltration of high-pH hypersaline brines, with or without a contribution from basinal brines. The proposed link to surface environments suggest that Paleoproterozoic BIF-ore upgrade may provide a record of a critical time in the evolution of the Earth’s biosphere and hydrosphere.