Earth's geodynamic evolution constrained by 182 W in Archean seawater

• Published in: Nature communications Vol. 13; no. 1; p. 2701
• Main Authors: Mundl-Petermeier, A, Viehmann, S, Tusch, J, Bau, M, Kurzweil, F, Münker, C
• Format: Journal Article
• Language: English
• Published: England 16-05-2022
• ISSN: 2041-1723

Radiogenic isotope systems are important geochemical tools to unravel geodynamic processes on Earth. Applied to ancient marine chemical sediments such as banded iron formations, the short-lived
Hf-
W isotope system can serve as key instrument to decipher Earth's geodynamic evolution. Here we show high-precision
W isotope data of the 2.7 Ga old banded iron formation from the Temagami Greenstone Belt, NE Canada, that reveal distinct
W differences in alternating Si-rich (7.9 ppm enrichment) and Fe-rich (5.3 ppm enrichment) bands reflecting variable flux of W from continental and hydrothermal mantle sources into ambient seawater, respectively. Greater
W excesses in Si-rich layers relative to associated shales (5.9 ppm enrichment), representing regional upper continental crust composition, suggest that the Si-rich bands record the global rather than the local seawater
W signature. The distinct intra-band differences highlight the potential of
W isotope signatures in banded iron formations to simultaneously track the evolution of crust and upper mantle through deep time.