On the hydration of olivine in ultramafic rocks: Implications from Fe isotopes in serpentinites
Access Status
Authors
Date
2017Type
Metadata
Show full item recordCitation
Source Title
ISSN
School
Collection
Abstract
© 2017 The behavior of Fe during serpentinization largely controls the potential for oxidation-reduction reactions and energy budget for serpentinite-hosted microbial communities. We present Fe isotope data for mineral separates from a partially serpentinized dunite from New Caledonia to understand the behavior of Fe during serpentinization processes. Our new Fe isotope data in mineral separates is compared to existing data from whole rock studies of serpentinites, which have generally concluded that Fe mobility during serpentinization is restricted to the highest temperatures of serpentinization in subduction zones. Measurements of mineral separates from New Caledonia show significant Fe isotope fractionations, with serpentine-brucite mixtures having the lowest d 56 Fe ~ -0.35‰ and magnetite having the highest d 56 Fe ~ +0.75‰. Olivine, orthopyroxene, and the whole rock composition are all within error of d 56 Fe = 0.00‰. Fe isotope thermometry between mineral phases reveals two distinct temperatures of equilibration, one for the mantle olivine and pyroxene (~1325 °C), and a second, much lower temperature (~335 °C) for the serpentinite assemblage. The combined isotopic, mineralogical and geochemical data indicate that during the magnetite-forming stage of serpentinization, a pore fluid in equilibrium with the mineralogical assemblage evolves to higher Fe concentrations as serpentinization proceeds. When this pore fluid is removed from the serpentinizing environment, the total abundance of Fe removed from the rock in the pore fluid is much less than the bulk rock Fe and has a minimal effect on the overall rock composition.
Related items
Showing items related by title, author, creator and subject.
-
Crossley, R.J.; Evans, Katy ; Evans, Noreen ; Bragagni, A.; McDonald, B.J.; Reddy, Steven ; Speelmanns, I.M. (2020)The highly siderophile elements (HSE) include the economically critical platinum group elements (PGE; Os, Ir, Ru, Rh, Pt, Pd, Au and Re), gold and rhenium. The HSE are redox sensitive in mantle and seafloor environments ...
-
Beinlich, Andreas; Plümper, O.; Hövelmann, J.; Austrheim, H.; Jamtveit, B. (2012)Carbonation of ultramafic rocks is being considered as an in situ disposal strategy for anthropogenic CO 2. We present observations from massively carbonated serpentinites at Linnajavri, N-Norway, where serpentinized ...
-
Crossley, R.; Evans, Katy; Jeon, H.; Kilburn, M. (2018)Devolatilisation of serpentinites at depth in subduction zones contributes significant quantities of sulfur and other redox sensitive elements to the sub-arc mantle. However, the fate of sulfur in subducted serpentinites ...