Tungsten Isotope Composition of Archean Crustal Reservoirs and Implications for Terrestrial μ182W Evolution

Jesse R. Reimink, Andrea Mundl-Petermeier, Richard W. Carlson, Steven B. Shirey, Richard J. Walker, D. Graham Pearson

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

The evolution of Earth's major geochemical reservoirs over ~4.5 × 109 years remains a matter of intense study. Geochemical tools in the form of short-lived radionuclide isotope ratios (142Nd/144Nd and 182W/184W) have expanded our understanding of the geochemical variability in both the modern and ancient Earth. Here, we present 142Nd/144Nd and 182W/184W data from a suite of rocks from the Slave craton that formed over a 1.1 × 109 year time span in the Archean. The rocks have consistently high 182W/184W, yet 142Nd/144Nd that is lower than bulk mantle and increased over time. The declining variability in 142Nd/144Nd with time likely reflects the homogenization of compositional heterogeneities in the silicate Earth that were initially created by differentiation events that occurred prior to 4.2 Ga. The elevated 182W/184W recorded in the Slave samples help refine models for the broader W-isotope evolution of the silicate Earth. Globally, the Archean mantle that formed continental crust was dominated by 182W/184W elevated by some 10–15 ppm compared to the value for the modern upper mantle. The Slave craton lacks significant volumes of komatiite yet has elevated 182W/184W until 2.9 Ga. This observation, combined with the presence of other komatiite suites that have low 182W/184W, suggests that deep-seated sources contributed low 182W/184W in the Archean Earth. The regional variability in 182W/184W may be explained by invoking chemical and/or isotopic exchange between a well-mixed silicate Earth and the core or a portion of the lower mantle whose W-isotope composition has been influenced by interaction with the core.

Original languageEnglish (US)
Article numbere2020GC009155
JournalGeochemistry, Geophysics, Geosystems
Volume21
Issue number7
DOIs
StatePublished - Jul 1 2020

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

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