Fluid-induced retrogression of granulites in the Bergen Arcs, Caledonides of W. Norway

fluid inclusion evidence from amphibolite-facies shear zones

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

*Corresponding author for this work

    Research output: Contribution to journalArticle

    41 Citations (Scopus)


    At Holsnøy Island, Bergen Arcs (Caledonides of W. Norway), amphibolite-facies shear zones transect Grenvillian granulite-facies rocks. Within the shear zones, the orthopyroxene bearing mineral assemblages of the protolith are replaced by biotite- and amphibolite-bearing parageneses. The shear zones are assumed to have formed at T=600±75°C and within the kyanite field, but below the stability of omphacite. Quartz veins central in the shear zones contain saline aqueous fluid inclusions, representing a fluid phase with 2-16 wt,% NaCl and a variable Na Ca ratio. In areas with only static retrogression, aqueous fluid inclusions with variable salinity (from 5 to ca. 50 wt.% NaCl) are associated with CO2-inclusions with minor N2-contents (XN2=4-6 mole%). The aqueous fluid was introduced during amphibolite-facies metamorphism, the carbonic fluid was inherited from the protolith. The composition and density properties of the aqueous fluids are compatible with introduction at the assumed amphibolite-facies conditions and suggest an uplift path (sub) parallel to their isochores. The carbonic fluid inclusions have been re-equilibrated during late stages of post-metamorphic uplift. The data presented highlight the differences between the fluid regimes in the granulite-facies (CO2), eclogite-facies (N2-rich fluids) and amphibolite-facies (H2O-salt) metamorphic events at Holsnøy.

    Original languageEnglish
    Pages (from-to)29-42
    Number of pages14
    Issue number1
    Publication statusPublished - 1991

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