Yan Hu1, Fang-Zhen Teng1, Terry Plank2, Catherine Chauvel3,4. 1. Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA. yanhu@uw.edu fteng@uw.edu. 2. Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964-8000, USA. 3. Université de Paris, Institut de Physique du Globe de Paris, CNRS, F-75005 Paris, France. 4. Université Grenoble Alpes, ISTerre, CNRS, F-38041 Grenoble, France.
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 δ41K 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 δ41K 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-δ41K signature of seawater. These regionally varying subducting components are heterogeneous K inputs to the mantle.
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 δ41K 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 δ41K 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-δ41K signature of seawater. These regionally varying subducting components are heterogeneous K inputs to the mantle.