Geochemistry of Sveconorwegian augen gneisses from SW Norway at the amphibolite-granulite facies transition

The augen gneisses of Rogaland-Vest-Agder were emplaced as amphibole-biotite granodiorites rich in K-feldspar phenocrysts. They were probably pre- or syntectonically emplaced and were metamorphosed under lower amphibole to granulite facies conditions after their emplacement. Three metamorphic zones defined by two isograds (Cpx-in and Opx-in) can be established in the augen gneisses using ferromagnesian minerals: zone 1 = Bt ± Am zone; zone 2 = Bt ± Am ± Cpx zone and zone 3, close to the Rogaland anorthosite complex, in granulite facies = Bt ± Am ± Cpx ± Opx zone. Pyroxene forming reactions occur in two stages in the augen gneisses (first producting Cpx and then Opx); amphibole appears to be an important reactant in the pyroxene-forming reactions while biotite is not. -from AuthorSCOPUS: NotDefined.j