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Incomplete high P–T metamorphic transitions within the Kvamsøy pyroxenite complex, west Norway: a case study of disequilibrium
Author(s) -
MØRK MAI BRITT E.
Publication year - 1985
Publication title -
journal of metamorphic geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.639
H-Index - 114
eISSN - 1525-1314
pISSN - 0263-4929
DOI - 10.1111/j.1525-1314.1985.tb00320.x
Subject(s) - geology , geochemistry , plagioclase , gabbro , olivine , metamorphism , anorthosite , geothermobarometry , mafic , petrology , igneous rock , quartz , paleontology
The Kvamsøy pyroxenite complex consists of olivine websterite, olivine gabbro and leucogabbro‐norite which have been subjected to regional high P‐T (HPT) metamorphism. The metamorphism has resulted in a range of disequilibrium textures with the development of coronas and pseudomorphism of the igneous phases. Reactions between felsic and mafic mineral domains have been controlled by variable and selective diffusion of elements, resulting in a variety of local plagioclase‐breakdown reactions and in significant compositional variations for the product garnet. Restricted diffusion favours transient reaction stages with garnet ± spinel ± corundum ± zoisite after calcic plagioclase in olivine gabbro and olivine websterite and garnet ± spinel ± kyanite ± quartz + sodic plagioclase in leucogabbro‐norite. Complete HPT reaction has produced garnet pyroxenite which consists of garnet + diopside + hornblende + zoisite in gabbroic rocks, while amphibolitization continued during the cooling and uplift history. Grt + Ky + Pl + Qtz geobarometry suggests pressures in the range 13‐16 kbar for T = 750°C, comparable with the regional eclogite‐forming metamorphism.