Metamorphism and migmatization in the Västervik area, Se Sweden

Abstract

Abstract Detailed investigations of metamorphism and migmatization in the northern archipelago of Misterhult, south of Vastervik, SE Sweden, show that two main events can be distinguished: 1. Period of prograde metamorphism: the maximum phase being a high-stage paragenesis with K-feldspar and sillimanite. Fleck and veined gneisses are formed, the former due to porphyroblastic growth (e. g. cordierite, andalusite) and/or metamorphic differentiation, the latter most likely due to metamorphic differentiation. A rise in fH2O and aK+ occurred, connected with the prograde metamorphism of argillaceous rocks (i.e. the breakdown of muscovite). 2. Period of retrograde metamorphism: the most intense stage being equal to “greenschist facies”. Raft migmatites and probably the major part of the agmatites form; the former by introduction of a K-rich volatile phase (from the younger granites) into a metasediment-metabasise-sequence, the latter due to the effect of non-hydrostatic pressure and the intrusion of a K-rich ph...