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Character and timing of Svecokarelian, late-orogenic ductile deformation zones in Jämtland, west central sweden
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology. (Berg)
2001 (English)In: GFF, ISSN 1103-5897, Vol. 123, no 4, 225-236 p.Article in journal (Refereed) Published
Abstract [en]

An anastomosing pattern of NW-SE to NNW-SSE trending, ductile shear zones have affected the Precambrian bedrock in central Jämtland. Spatially these structures are related to two major shear zone systems, the Storsjön-Edsbyn Deformation Zone (SEDZ) and the Hassela Shear Zone (HSZ). Several of the local zones occur between Lake Näkten and Lake Locknesjön and coincide with linear magnetic anomalies. The dextral kinematics recorded are emphasised by clockwise rotation of early Svecofennian rocks, that partly are arranged in a large-scale C/S pattern. Three different, ductile shear zones yield U-Pb titanite ages of 1801±1, 1799±7, and 1794±3 Ma, interpreted to date the deformation. Pale titanite overgrowths, colourless titanite, and apatite yield younger U-Pb ages (c. 1.75 Ga) which argue for a tectonic reactivation of the zones, or a later thermal and/or hydrothermal event, as indicated by intrusions of cross-cutting pegmatites and felsic dykes. A hydrothermal activity during the Caledonian orogeny is recorded in one of the deformation zones. This is shown by an altered fabric containing titanites with pale outer parts which are severely discordant in a U-Pb concordia diagram with a Palaeozoic lower intercept. Sm-Nd analyses on re-precipitated zircon grains also deviate considerably from a Palaeoproterozoic trend given by other minerals in the assemblage.

Place, publisher, year, edition, pages
2001. Vol. 123, no 4, 225-236 p.
Keyword [en]
Palaeoproterozoic, Svecofennian, shear zone, U-Pb, titanite, Jämtland, Sweden
National Category
Earth and Related Environmental Sciences
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
URN: urn:nbn:se:uu:diva-144286DOI: 10.1080/11035890101234225OAI: oai:DiVA.org:uu-144286DiVA: diva2:392922
Available from: 2011-01-28 Created: 2011-01-28 Last updated: 2013-09-10Bibliographically approved

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Högdahl, KarinSjöström, Håkan
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