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

ABSTRACT: 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 ¹⁸²Hf-¹⁸²W isotope system can serve as key instrument to decipher Earth's geodynamic evolution. Here we show high-precision ¹⁸²W isotope data of the 2.7 Ga old banded iron formation from the Temagami Greenstone Belt, NE Canada, that reveal distinct ¹⁸²W 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 ¹⁸²W 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 ¹⁸²W signature. The distinct intra-band differences highlight the potential of ¹⁸²W isotope signatures in banded iron formations to simultaneously track the evolution of crust and upper mantle through deep time.

SUBMITTER: Mundl-Petermeier A

PROVIDER: S-EPMC9110358 | biostudies-literature | 2022 May

REPOSITORIES: biostudies-literature

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

Mundl-Petermeier A A Viehmann S S Tusch J J Bau M M Kurzweil F F Münker C C

Nature communications 20220516 1

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 182Hf-182W isotope system can serve as key instrument to decipher Earth's geodynamic evolution. Here we show high-precision 182W isotope data of the 2.7 Ga old banded iron formation from the Temagami Greenstone Belt, NE Canada, that reveal distinct 182W differen ...[more]

PMID: 35577795

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Project description:The geodynamic evolution of the Dinaride Mountains of southeastern Europe is relatively poorly understood, especially in comparison with the neighboring Alps and Carpathians. Here, we construct a new chronostratigraphy for the post-orogenic intra-montane basins of the Central Dinarides based on paleomagnetic and 40Ar/39Ar age data. A first phase of basin formation occurred in the late Oligocene. A second phase of basin formation took place between 18 and 13 Ma, concurrent with profound extension in the neighboring Pannonian Basin. Our paleomagnetic results further indicate that the Dinarides have not experienced any significant tectonic rotation since the late Oligocene. This implies that the Dinarides were decoupled from the adjacent Adria and the Tisza-Dacia Mega-Units that both underwent major rotation during the Miocene. The Dinaride orogen must consequently have accommodated significant shortening. This is corroborated by our AMS data that indicate post-Middle Miocene shortening in the frontal zone, wrenching in the central part of the orogen, and compression in the hinterland. A review of paleomagnetic data from the Adria plate, which plays a major role in the evolution of the Dinarides as well as the Alps, constrains rotation since the Early Cretaceous to 48 ± 10° counterclockwise and indicates 20° of this rotation took place since the Miocene. It also shows that Adria behaved as an independent plate from the Late Jurassic to the Eocene. From the Eocene onwards, coupling between Adria and Africa was stronger than between Adria and Europe. Adria continued to behave as an independent plate. The amount of rotation within the Adria-Dinarides collision zone increases with age and proximity of the sampled sediments to undeformed Adria. These results significantly improve our insight in the post-orogenic evolution of the Dinarides and resolve an apparent controversy between structural geological and paleomagnetic rotation estimates for the Dinarides as well as Adria.

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

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Earth's geodynamic evolution constrained by <sup>182</sup>W in Archean seawater.

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