Year: 2025
Type: preprint
Abstract: The Earth's hydrogen isotope signature (D/H) is a primary tool for investigating the origins of terrestrial water and other volatiles. However, this signature is not uniform within the Earth. Whereas seawater D/H resembles that of carbonaceous chondrites and falls outside of the enstatite chondrite range, mantle water is consistent with the enstatite chondrite signature. A recently popularized interpretation is that the Earth’s surface and interior had distinct cosmochemical sources for volatiles during planetary accretion: mantle volatiles were initially sourced by enstatite chondrite-like material, followed by a relatively late shift to a carbonaceous chondrite-like source for surface volatiles. This scenario requires that initially disparate isotopic signatures of the early mantle and surface have been preserved until present day, but the likelihood of such preservation is uncertain. To explore the evolution of surface and mantle D/H throughout Earth’s history, we combine geochemical and geodynamic modeling. We find that the fractionation accompanying plate tectonic processes naturally induces the observed D/H dichotomy between Earth’s surface and interior, for a wide range of initial D/H distribution scenarios. Thus, while the bulk silicate Earth D/H, which we estimate is between \(-42‰\) and \(-30‰\) (expressed as \(\delta\)D), may be used to infer the cosmochemical origins of volatiles, the present-day distribution of D/H is likely a fingerprint of plate tectonics, and not leftover from a transition during volatile accretion.
Authors: Amy L. Ferrick, Jun Korenaga
Institution: Yale University
Language: English
Topic: Astro and Planetary Science
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
OpenAlex ID: W4414199757
Cites:
Cited by:
Related to: