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Extreme Magnesium Isotope Fractionation at Outcrop Scale Records the Mechanism and Rate at which Reaction Fronts Advance

von Strandmann, PAEP; Dohmen, R; Marschall, HR; Schumacher, JC; Elliott, T; (2015) Extreme Magnesium Isotope Fractionation at Outcrop Scale Records the Mechanism and Rate at which Reaction Fronts Advance. Journal of Petrology , 56 (1) 33 - 58. 10.1093/petrology/egu070. Green open access

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Abstract

Isotopic fractionation of cationic species during diffusive transport provides a novel means of constraining the style and timing of metamorphic transformations. Here we document a major (∼1‰) decrease in the Mg isotopic composition of the reaction front of an exhumed contact between rocks of subducted crust and serpentinite in the Syros mélange zone. This isotopic perturbation extends over a notable length scale (∼1 m), implicating diffusion of Mg through an intergranular fluid network over a period of ∼100 kyr. These novel observations confirm models of diffusion-controlled growth of reaction zones formed between rocks of contrasting compositions, such as found at the slab–mantle interface in subduction zones. The results also demonstrate that diffusive processes can result in exotic stable isotope compositions of major elements with implications for mantle xenoliths and complex intrusions.

Type: Article
Title: Extreme Magnesium Isotope Fractionation at Outcrop Scale Records the Mechanism and Rate at which Reaction Fronts Advance
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/petrology/egu070
Publisher version: http://dx.doi.org/10.1093/petrology/egu070
Language: English
Additional information: This is a pre-copyedited, author-produced PDF of an article accepted for publication in von Strandmann, PAEP; Dohmen, R; Marschall, HR; Schumacher, JC; Elliott, T; (2015) Extreme Magnesium Isotope Fractionation at Outcrop Scale Records the Mechanism and Rate at which Reaction Fronts Advance. Journal of Petrology, 56 (1) 33 - 58. 10.1093/petrology/egu070, following peer review. The version of record [insert complete citation information here] is available online at: http://dx.doi.org/10.1093/petrology/egu070
Keywords: diffusion, isotope, metasomatism, monomineralic
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/1462110
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