Low-Grade Sedimentary Rocks on Vanna, North Norway: a New Occurrence 301
NORWEGIAN JOURNAL OF GEOLOGY Low-grade sedimentary rocks on Vanna, North Norway: a new occurrence 301 Low-grade sedimentary rocks on Vanna, North Norway: a new occurrence of a Palaeoproterozoic (2.4-2.2 Ga) cover succession in northern Fennoscandia Steffen G. Bergh, Kåre Kullerud, Fernando Corfu, Paul E.B. Armitage, Børre Davidsen, Helge W. Johansen, Trine Pettersen & Stian Knudsen Steffen G. Bergh, Kåre Kullerud, Fernando Corfu, Paul E.B. Armitage, Børre Davidsen, Helge W. Johansen, Trine Pettersen & Stian Knudsen: Low- grade sedimentary rocks on Vanna, North Norway: a new occurrence of a Palaeoproterozoic (2.4-2.2 Ga) cover succession in northern Fennos- candia. Norwegian Journal of Geology, vol. 87, pp. 301-318.Trondheim 2007. ISSN 029-196X. The Archaean to Palaeoproterozoic West Troms Basement Complex comprises various tonalitic gneisses, felsic and mafic intrusive rocks and inter- vening narrow NW-SE-trending belts with partly mylonitised, low- to medium-grade, metavolcanic and metasedimentary rocks. The low-grade, parautochthonous Vanna group unconformably overlies 2885 ± 20 Ma tonalitic basement on the island of Vanna. It is composed of siliciclastic sedi- mentary rocks and intercalated mudstones with well-preserved shallow-water sedimentary structures and internal erosional surfaces. A major dio- rite body intruded soon after consolidation of the sediments. The stack of sedimentary rocks is tilted and complexly folded and deformed by crustal transpression. Previous workers considered the rocks to be either part of the Neoproterozoic to Cambrian autochthonous cover or a part of the Middle Allochthon, and deformed during the Caledonian orogeny. New U-Pb ages for magmatic zircon and titanite of the diorite sill, however, yield a crystallization age of 2221 ± 3 Ma.
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