The composition of Earth's oldest iron formations: The Nuvvuagittuq Supracrustal Belt (Québec, Canada)

Aleksandra M. Mloszewska, Ernesto Pecoits, Nicole L. Cates, S. Mojzsis, Jonathan O'Neil, Leslie J. Robbins, Kurt O. Konhauser

Research output: Contribution to journalArticle

61 Citations (Scopus)

Abstract

The composition of iron formations in the ≥3.75Gayr old Nuvvuagittuq Supracrustal Belt in northern Québec provides a proxy for seawater composition of the Eoarchean, and perhaps Hadean oceans, as well as constraints on the types of nutrients available to Earth's earliest life forms. Integrated petrologic and geochemical relationships, mapped between mineral phases in thin section and whole-rock chemistry, provide a framework for interpreting bulk and micro-scale variations in these chemical sedimentary precipitates. Results show that there are two distinct chemical sedimentary units in the Nuvvuagittuq belt: i) a banded iron formation (BIF) consisting of alternating micro-bands of magnetite, Ca-Mg-Fe-silicates and quartz, and ii) a more silicate-rich (Fe-poor) unit, the banded silicate-formation (BSF), of alternating micro-bands of quartz and Ca-Mg-Fe silicates. Precursor BIF and BSF deposits were likely layered amorphous silica and ferric-oxyhydroxides, fine-grained carbonate oozes and/or Ca-Mg-Fe rich silicate gels deposited in a marine setting. Low Al 2O 3, TiO 2 and HFSE concentrations show that they are relatively detritus-free, with distinctively seawater-like REE+Y profiles and consistently positive Eu anomalies. These features suggest that the rocks preserved their seawater-like compositions despite metamorphic overprinting. The most significant trace elements in the sediments are Ni and Zn. Experimentally-derived partitioning coefficients show that Ni was enriched in Eoarchean seawater as compared to today (up to 300nM), while Zn was fairly similar (up to 20nM). Compositional resemblances between the Nuvvuagittuq sediments and those documented in the ca. 3.8Ga Isua supracrustals (West Greenland) provide a plausible case that global ocean processes - in terms of trace metal abundances - had reached steady-state by the Eoarchean.

Original languageEnglish
Pages (from-to)331-342
Number of pages12
JournalEarth and Planetary Science Letters
Volume317-318
DOIs
Publication statusPublished - Feb 1 2012

Fingerprint

Silicates
Canada
silicates
Iron
silicate
Earth (planet)
Seawater
iron
Chemical analysis
seawater
banded iron formation
Quartz
oceans
Sediments
sediments
quartz
Rocks
Hadean
rocks
Ferrosoferric Oxide

Keywords

  • Banded iron formation
  • Eoarchean
  • Hadean
  • Nuvvuagittuq Supracrustal Belt
  • Seawater
  • Trace element geochemistry

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

The composition of Earth's oldest iron formations : The Nuvvuagittuq Supracrustal Belt (Québec, Canada). / Mloszewska, Aleksandra M.; Pecoits, Ernesto; Cates, Nicole L.; Mojzsis, S.; O'Neil, Jonathan; Robbins, Leslie J.; Konhauser, Kurt O.

In: Earth and Planetary Science Letters, Vol. 317-318, 01.02.2012, p. 331-342.

Research output: Contribution to journalArticle

Mloszewska, Aleksandra M. ; Pecoits, Ernesto ; Cates, Nicole L. ; Mojzsis, S. ; O'Neil, Jonathan ; Robbins, Leslie J. ; Konhauser, Kurt O. / The composition of Earth's oldest iron formations : The Nuvvuagittuq Supracrustal Belt (Québec, Canada). In: Earth and Planetary Science Letters. 2012 ; Vol. 317-318. pp. 331-342.
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