Stuart, CA, Daczko, NR and Piazolo, S orcid.org/0000-0001-7723-8170 (2017) Local partial melting of the lower crust triggered by hydration through melt-rock interaction: an example from Fiordland, New Zealand. Journal of Metamorphic Geology, 35 (2). pp. 213-230. ISSN 0263-4929
Abstract
We investigate a low-strain outcrop of the lower crust, the Pembroke Granulite, exposed in northern Fiordland, New Zealand, which exhibits localized partial melting. Migmatite and associated tschermakite–clinozoisite (TC) gneiss form irregular, elongate bodies that cut a two-pyroxene–pargasite (PP) gneiss. Gradational boundaries between rock types, and the progressive nature of changes in mineral assemblage, microstructure and chemistry are consistent with the TC gneiss and migmatite representing modified versions of the PP gneiss. Modification is essentially isochemical, where partial modification involves hydration of the assemblage and mineral chemistry changes, and complete modification involves additional recrystallization and in situ partial melt production. Microstructures of quartz and plagioclase, including small dihedral angles, string of beads textures and films surrounding amphibole and garnet grains are consistent with the former presence of melt in modified rock types. The documented rock modification is attributed to melt–rock interaction occurring during porous melt flow of a dominantly externally derived, hydrous silicate melt. Microstructures indicate melt flow occurred along grain boundaries and field relationships show it was focused into channels tens of metres wide, with preference for following the pre-existing foliation. Melt–rock interaction at the grain scale resulted in hydration and modification of the host PP gneiss, which resulted in localized partial melting. These relationships indicate prograde hydration during localized melt–rock interaction drove migmatization of the lower crust.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Keywords: | in situ partial melting; melt ascent; melt–rock interaction; metabasic migmatite; pervasive migration |
Dates: |
|
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: | 01 Feb 2017 11:21 |
Last Modified: | 18 Jan 2023 14:49 |
Published Version: | https://doi.org/10.1111/jmg.12229 |
Status: | Published |
Publisher: | Wiley |
Identification Number: | 10.1111/jmg.12229 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:111448 |