Journal Article

Clues from Fe Isotope Variations on the Origin of Early Archean BIFs from Greenland

van Zuilen, Mark, Marty, Bernard, Janney, Philip E., Dauphas, Nicolas, Wadhwa, Meenakshi, Davis, Andrew M.

2004

Overview

Archean rocks may provide a record of early Earth environments. However, such rocks have often been metamorphosed by high pressure and temperature, which can overprint the signatures of their original formation. Here, we show that the early Archean banded rocks from Isua, Akilia, and Innersuartuut, Greenland, are enriched in heavy iron isotopes by 0.1 to 0.5 per mil per atomic mass unit relative to igneous rocks worldwide. The observed enrichments are compatible with the transport, oxidation, and subsequent precipitation of ferrous iron emanating from hydrothermal vents and thus suggest that the original rocks were banded iron formations (BIFs). These variations therefore support a sedimentary origin for the Akilia banded rocks, which represent one of the oldest known occurrences of water-laid deposits on Earth.

• Publisher: American Association for the Advancement of Science,The American Association for the Advancement of Science
• Subject: Basalt / Climate / Earth / Earth sciences / Earth, ocean, space / Exact sciences and technology / Fractionation / Fractions / Geology / Greenland / High pressure / Igneous rocks / Iron / Isotope geochemistry / Isotope geochemistry. Geochronology / Isotopes / Life / Marine / Minerals / Origin / Origin of life / Oxidation / Petrology of sedimentary rocks except quaternary rocks / Rocks / Sedimentary rocks / Signatures / temperature