Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8959576 | Geochimica et Cosmochimica Acta | 2018 | 29 Pages |
Abstract
Our results reveal that many primary biogenic carbonates indeed fractionate U isotopes during U incorporation, and that this fractionation is in the same direction as observed in abiotic CaCO3 coprecipitation experiments. However, the magnitude of isotope fractionation in biogenic carbonates is often smaller than that predicted by abiotic CaCO3 coprecipitation experiments (0.00-0.09â° vs. 0.11â¯Â±â¯0.02â°), suggesting that one or more processes suppress U isotope fractionation during U incorporation into biogenic carbonates. We propose that closed-system behavior due to the isolation of the local calcificiation sites from ambient seawater, and/or kinetic/disequilibrium isotope fractionation caused by carbonate growth kinetics, explains this observation. Our results indicate that U isotope fractionation between biogenic carbonates and seawater might help to constrain U partition coefficients, carbonate growth rates, or seawater chemistry during coprecipitation.
Keywords
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geochemistry and Petrology
Authors
Xinming Chen, Stephen J. Romaniello, Achim D. Herrmann, Elias Samankassou, Ariel D. Anbar,