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Potassium isotopic heterogeneity in subducting oceanic plates.

ABSTRACT: Oceanic crust and sediments are the primary K sinks for seawater, and they deliver considerable amounts of K to the mantle via subduction. Historically, these crustal components were not studied for K isotopes because of the lack of analytical precision to differentiate terrestrial variations. Here, we report a high-precision dataset that reveals substantial variability in oceanic plates and provides further insights into the oceanic K cycle. Sixty-nine sediments worldwide yield a broad ?⁴¹K range from -1.3 to -0.02‰. The unusually low values are indicative of release of heavy K during continental weathering and uptake of light K during submarine diagenetic alteration. Twenty samples of altered western Pacific crust from ODP Site 801 display ?⁴¹K from -0.60 to -0.05‰, averaging at -0.32‰. Our results indicate that submarine alteration of oceanic plates is essential for generating the high-?⁴¹K signature of seawater. These regionally varying subducting components are heterogeneous K inputs to the mantle.

SUBMITTER: Hu Y

PROVIDER: S-EPMC7821876 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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Potassium isotopic heterogeneity in subducting oceanic plates.

Hu Yan Y Teng Fang-Zhen FZ Plank Terry T Chauvel Catherine C

Science advances 20201202 49

Oceanic crust and sediments are the primary K sinks for seawater, and they deliver considerable amounts of K to the mantle via subduction. Historically, these crustal components were not studied for K isotopes because of the lack of analytical precision to differentiate terrestrial variations. Here, we report a high-precision dataset that reveals substantial variability in oceanic plates and provides further insights into the oceanic K cycle. Sixty-nine sediments worldwide yield a broad δ<sup>41 ...[more]

PMID: 33268367

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