Chapman, T, Clarke, GL, Piazolo, S orcid.org/0000-0001-7723-8170 et al. (2 more authors) (2019) Grain‐scale dependency of metamorphic reaction on crystal plastic strain. Journal of Metamorphic Geology, 37 (7). pp. 1021-1036. ISSN 0263-4929
Abstract
The Breaksea Orthogneiss in Fiordland, New Zealand preserves water‐poor intermediate and mafic igneous rocks that were partially recrystallized to omphacite granulite and eclogite, respectively, at P ≈ 1.8 GPa and T ≈ 850°C. Metamorphic reaction consumed plagioclase and produced grossular‐rich garnet, jadeite‐rich omphacite, clinozoisite and kyanite. The extent of metamorphic reaction, identified by major and trace element composition and microstructural features, is patchy on the grain and outcrop scale. Domains of re‐equilibration coincide with areas that exhibit higher strain suggesting a causal link between crystal plastic strain and metamorphic reaction. Quantitative orientation analysis (EBSD) identifies gradual and stepped changes in crystal lattice orientations of igneous phenocrysts that are surrounded by homophase areas of neoblasts, characterized by high grain boundary to volume ratios and little to no internal lattice distortion. The narrow, peripheral compositional modification of less deformed garnet and omphacite phenocrysts reflects limited lattice diffusion in areas that lacked three‐dimensional networks of interconnected low‐angle boundaries. Low‐angle boundaries acted as elemental pathways (pipe diffusion) that enhanced in‐grain element diffusion. The scale of pipe diffusion is pronounced in garnet relatively to clinopyroxene. Strain‐induced mineral transformation largely controlled the extent of high‐T metamorphic reaction under relatively fluid‐poor conditions.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2019 John Wiley & Sons Ltd. This is the peer reviewed version of the following article: Chapman, T, Clarke, GL, Piazolo, S, Robbins, VA, Trimby, PW. Grain‐scale dependency of metamorphic reaction on crystal plastic strain. J Metamorph Geol. 2019; 37: 1021– 1036, which has been published in final form at https://doi.org/10.1111/jmg.12473. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. |
Keywords: | crystal plastic strain; deformation; element diffusion; metamorphic equilibration; microstructures; recrystallization |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 16 Oct 2019 10:17 |
Last Modified: | 23 Jan 2020 01:39 |
Status: | Published |
Publisher: | Wiley |
Identification Number: | 10.1111/jmg.12473 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:152120 |