Convective isolation of hadean mantle reservoirs through archean time

Jonas Tusch, Carsten Münker, Eric Hasenstab, Mike Jansen, Chris S. Marien, Florian Kurzweil, Martin J. van Kranendonk, Hugh Smithies, Wolfgang Maier, Dieter Garbe-Schönberg

Research output: Contribution to journalArticlepeer-review

Abstract

Although Earth has a convecting mantle, ancient mantle reservoirs that formed within the first 100 Ma of Earth’s history (Hadean Eon) appear to have been preserved through geologic time. Evidence for this is based on small anomalies of isotopes such as 182W, 142Nd, and 129Xe that are decay products of short-lived nuclide systems. Studies of such short-lived isotopes have typically focused on geological units with a limited age range and therefore only provide snapshots of regional mantle heterogeneities. Here we present a dataset for short-lived 182Hf−182W (half-life 9 Ma) in a comprehensive rock suite from the Pilbara Craton, Western Australia. The samples analyzed preserve a unique geological archive covering 800 Ma of Archean history. Pristine 182W signatures that directly reflect the W isotopic composition of parental sources are only preserved in unaltered mafic samples with near canonical W/Th (0.07 to 0.26). Early Paleoarchean, mafic igneous rocks from the East Pilbara Terrane display a uniform pristine μ182W excess of 12.6 ± 1.4 ppm. From ca. 3.3Ga onward, the pristine 182W signatures progressively vanish and are only preserved in younger rocks of the craton that tap stabilized ancient lithosphere. Given that the anomalous 182W signature must have formed by ca. 4.5 Ga, the mantle domain that was tapped by magmatism in the Pilbara Craton must have been convectively isolated for nearly 1.2 Ga. This finding puts lower bounds on timescale estimates for localized convective homogenization in early Earth’s interior and on the widespread emergence of plate tectonics that are both important input parameters in many physical models.

Original languageEnglish
Article numbere2012626118
JournalProceedings of the National Academy of Sciences of the United States of America
Volume118
Issue number2
DOIs
Publication statusPublished - Jan 12 2021
Externally publishedYes

Keywords

  • Early earth
  • Late veneer
  • Mantle convection
  • Pilbara craton
  • Tungsten isotopes

ASJC Scopus subject areas

  • General

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