Metamorphism and migmatization in the Västervik area, Se Sweden
Kresten, Peter; Kresten, Peter; Department of Mineralogy and Petrology, University of Stockholm
Журнал:
Geologiska Föreningen i Stockholm Förhandlingar
Дата:
1971
Аннотация:
AbstractDetailed investigations of metamorphism and migmatization in the northern archipelago of Misterhult, south of Västervik, 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 fH<sub>2</sub>O 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 phase connected with diffusion of mainly plagioclase from the host rock (amphibolite). It can be stated that retrograde metamorphism affected the entire area, more or less intensively.
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