Work

Fe 3+ ∕ΣFe variation in lawsonite and epidote in subducted oceanic crust

Year: 2025

Type: article

Abstract: The hydrous Ca–Al silicates lawsonite and epidote group minerals (EGMs) are key phases in subduction-zone H 2 O and element cycling. In high-pressure–low-temperature metamorphic rocks, Fe in both minerals is typically assumed to be entirely Fe 3+ , which substitutes for Al in octahedral sites as a major component in most EGMs and as a minor component in lawsonite and zoisite. New Fe micro-X-ray absorption near-edge spectroscopy ( μ -XANES) analyses show substantial Fe 2+ in lawsonite in blueschist from New Caledonia and zoisite from an unknown locality. Analysed Fe-rich EGMs (epidote, clinozoisite) contain primarily Fe 3+ . Lawsonite and some EGMs in subducted oceanic crust may contain more Fe 2+ than is currently known, with possible implications for understanding subduction redox processes and conditions and why they vary in different subduction zones.

Source: European Journal of Mineralogy

DOI: 10.5194/ejm-37-143-2025

Authors: Donna L. Whitney, Max Wilke, Sara E. Hanel, Florian Heidelbach, Olivier Mathon, Angelika D. Rosa

Institutions: University of Minnesota, University of Potsdam, University of Bayreuth, European Synchrotron Radiation Facility

Language: English

Topic: Geological and Geochemical Analysis

Subfield: Geophysics

Field: Earth and Planetary Sciences

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $1,024

Funder: National Science Foundation