Petrology and tectonic setting of relatively low temperature eclogites and related rocks in the Dalsfjord area, Sunnfjord, West Norway.

An area to the south of Dalsfjord has been mapped and four lithological units
differentiated. These are (from the top downwards) the Vardheia unit,
consisting of heterogeneous paragneisses; the Flekke unit, consisting of
metabasic, ultrabasic and oxide-rich rocks, frequently with corona structures;
the Gjorlanger unit, consisting of dioritic to granodioritic orthogneisses
with common metabasic bodies and websterites, and the Basal Gneisses, with
pink granodioritic to monzonitic orthogneisses, paragneisses and pegmatites.
The latter is separated from the overlying unit by a zone of protomylonites.
Eclogites are found in all the units.
Gradational or intrusive relationships show that all the units are mutually
autochthonous. Many eclogites had demonstrable low-pressure igneous
protoliths and/or intrusive relationships with the gneisses, indicating a
crustal, eclogite-facies metamorphism of all the lithologies mapped. Relics
of early granulite-facies assemblages occur in most lithologies.
Bulk-rock geochemistry of Gjorlanger unit lithologies indicates calc-alkaline
affinities, resembling magmatic arc rocks but possibly modified during
granulite-facies metamorphism. Associated eclogites have been metasomatically
altered but retain some tholeiitic characteristics. Websterites are
tentatively related to the orthopyroxene eclogites of More and Romsdal. The
Flekke unit rocks have affinities with some layered basic intrusions typical
of mid-Proterozoic anorthosite suites.