The tectonic and metamorphic history of UHP basal gneisses and Blåhø- Surna cover complexes on Otrøy, Moldefjord, northern Western Gneiss Region, Norway

The tectonic and metamorphic history of UHP basal gneisses and Blåhø- Surna cover complexes on Otrøy, Moldefjord, northern Western Gneiss Region, Norway: New insights into the pre-Scandian evolution of Iapetus and exhumation of (U)HP metamorphic terranes

Smit, M.A.

Molengraaff Fonds

2006-05

This MSc research is focussed upon two aspects. The first focus is to identify and classify tectonometamorphic signals and to establish their significance with respect to the dynamics of the Iapetus Ocean before late-Caledonian (Scandian) closure and concurrent (ultra-) high pressure ((U)HP) metamorphism. The second focus is to monitor mechanisms and processes that account for the exhumation of the (U)HP gneisses of the Western Gneiss Region. The island of Otrøy, Moldefjord, in the northern (UHP part) of the Western Gneiss Region, was chosen as the research area. On this island (U)HP gneisses, grt-peridotites and eclogites are exposed, that are overlain by a stack of unidentified allochthonous metapelites and metabasites. Correlative field studies indicate that the latter rocks (addressed in this study as the GK-Nappe) are part of the Blåhø-Surna nappe complex, a Norwegian equivalent of the Seve Nappe Complex in Sweden. The multidisciplinary research includes: (1) a field study into lithologies and structures, (2) light-microscopic analysis into microstructures and mineralogy, (3) quantitative Electron Microprobe (EMP) analysis into major element chemistry and (4) EMP U-Pb monazite geochronology. These data provide relevant information on the evolution of the nappe before Scandian collision. Furthermore, Comparison of these data to information on the UHP basal gneisses provides insight into the physical processes in both foot- and hanging wall complexes as a consequence to exhumation.

http://resolver.tudelft.nl/uuid:10c917e6-b423-44f5-8e28-565786c2cf19

Utrecht University

Geoscience Reports

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(c) M.A. Smit