Mantle Hg isotopic heterogeneity and evidence of oceanic Hg recycling into the mantle.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 35177593.
- Also identified by DOI 10.1038/s41467-022-28577-1 and PMC identifier 8854601.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The geochemical cycle of mercury in Earth's surface environment (atmosphere, hydrosphere, biosphere) has been extensively studied; however, the deep geological cycling of this element is less well known. Here we document distinct mass-independent mercury isotope fractionation (expressed as Δ199Hg) in island arc basalts and mid-ocean ridge basalts. Both rock groups show positive Δ199Hg values up to 0.34‰ and 0.22‰, respectively, which deviate from recent estimates of the primitive mantle (Δ199Hg: 0.00 ± 0.10‰, 2 SD)1. The positive Δ199Hg values indicate recycling of marine Hg into the asthenospheric mantle. Such a crustal Hg isotope signature was not observed in our samples of ocean island basalts and continental flood basalts, but has recently been identified in canonical end-member samples of the deep mantle1, therefore demonstrating that recycling of mercury can affect both the upper and lower mantle. Our study reveals large-scale translithospheric Hg recycling via plate tectonics.