Granulitic inliers amidst a gneissic/migmatitic complex of the Owl Mts, Sudetes

Abstract

In NW part of the Owl Mts, Sudetes, the granulites are characteristically accompanied by serpentinized ultramafic and pyriboIitic rocks, including gametiferous peridotite and websterite of an upper mantle provenance. The ultrabasites display irregular intrusive contacts against the granuIites which pass diaphtoretica1ly into their migmatitic surroundings through a zone of transitional gneissic rock in which the retrogressive replacement of Gr + Ksp by Bio + PIg has been extensively accomplishing. Along the granulite/gneiss contact a belt of strongly recrystallized blastomylonite developed. Both the granulites and serpentinites are foliated and lineated, having received a distinct imprint from the F₂ + M₂tectonometamorphic episode that affected the gneissic/migmatiti complex. Hence interpretation that the upper mantle ultrabasites had intruded a deep-seated granulitic domain, localized outside the actual Moldanubian Sowie Mts complex, in another level or portion ()f the earth's crust. Then, during the pre-F₂ movements, some indetermined slices were tectonically cut from the parent granulitic domain and after undefined vertical or lateral transport (or both) became upthrust along the ductile shear zones, or otherwise inlaid, into the gneisses just undergoing intense regional folding, metamorphism, and migmatization. Since F₂ + M₂ episode the granulites and accompanying ultramafites have had their further tectonothermal history in common with the Owl Mts gneisses and migmatites.