Nitrogen-bearing, aqueous fluid inclusions in some eclogites from the Western Gneiss Region of the Norwegian Caledonides

T. Andersen*, E. A J Burke, H. Austrheim

*Corresponding author for this work

    Research output: Contribution to journalArticle

    98 Citations (Scopus)

    Abstract

    Minerals in eclogites from different localities in the Western Gneiss Region of the Norwegian Caledonides (age ≈425 Ma) contain a variety of fluid inclusions. The earliest inclusions recognized are contained in undeformed quartz grains, protected by garnet, and consist of H2O+N2 (with {Mathematical expression}). The reconstructed P-V-T-X properties of these fluid inclusions are compatible with peak or early-retrograde metamorphic conditions. Matrix minerals (quartz, garnet, apatite, plagioclase) contain a complex pattern of mostly truly secondary inclusions, dominated by CO2 and N2. The textural patterns and P-V-T-X properties of these inclusions are incompatible with the high pressures of the eclogite-forming metamorphic event, but suggest that they were formed during uplift, by a combination of remobilization of preexisting inclusions and influx of external fluids. The fluid introduced at a late stage was dominated by CO2, and did not contain N2. The present data agree with theoretical predictions of eclogite fluids from mineral equilibria, and highlight the differences between granulite (CO2) and eclogite (H2O+N2) fluid regimes. The provenance of the nitrogen in the eclogite fluid inclusions represents an important, but unsolved question in the petrology of high-pressure metamorphic rocks.

    Original languageEnglish
    Pages (from-to)153-165
    Number of pages13
    JournalContributions to Mineralogy and Petrology
    Volume103
    Issue number2
    DOIs
    Publication statusPublished - Oct 1989

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