Paleoproterozoic (2.0–1.8 Ga) syn-orogenic sedimentation, magmatism and mineralization in the Bothnia–Skellefteå lithotectonic unit, Svecokarelian orogen

Lithotectonic framework, tectonic evolution and mineral resources.

Document identifier: oai:DiVA.org:ltu-77983
Access full text here:10.1144/M50-2017-10
Keyword: Natural Sciences, Earth and Related Environmental Sciences, Geology, Naturvetenskap, Geovetenskap och miljövetenskap, Geologi, Ore Geology, Malmgeologi
Publication year: 2020
Abstract:

The Bothnia–Skellefteå lithotectonic unit is dominated by turbiditic wacke and argillite (Bothnian basin), deposited at 1.96 (or older)–1.86 Ga, metamorphosed generally under high-grade conditions and intruded by successive plutonic suites at 1.95–1.93, 1.90–1.88, 1.87–1.85 and 1.81–1.76 Ga. In the northern part, low-grade and low-strain, 1.90–1.86 Ga predominantly magmatic rocks (the Skellefte–Arvidsjaur magmatic province) are enclosed by the basinal components. Subduction-related processes in intra-arc basin and magmatic arc settings, respectively, are inferred. Changes in the metamorphic grade and the relative timing of deformation and structural style across the magmatic province are linked to major shear zones trending roughly north–south and, close to the southern margin, WNW–ESE. Zones trending WNW–ESE and ENE–WSW dominate southwards. Slip along the north–south zones in an extensional setting initiated synchronously with magmatic activity at 1.90–1.88 Ga. Tectonic inversion steered by accretion to a craton to the east, involving crustal shortening, ductile strain and crustal melting, occurred at 1.88–1.85 Ga. Deformation along shear zones under lower-grade conditions continued at c. 1.8 Ga. Felsic volcanic rocks (1.90–1.88 Ga) host exhalative and replacement-type volcanogenic massive sulphide deposits (the metallogenic Skellefte district). Other deposits include orogenic Au, particularly along the ‘gold line’ SW of this district, porphyry Cu–Au–Mo, and magmatic Ni–Cu along the ‘nickel line’ SE of the ‘gold line’.

Authors

Pietari Skyttä

Department of Geography and Geology, University of Turku
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Pär Weihed

Luleå tekniska universitet; Geovetenskap och miljöteknik
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Karin Högdahl

Department of Earth Sciences, Uppsala University. Department of Geology and Mineralogy, Åbo Akademi University
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Stefan Bergman

Geological Survey of Sweden
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Michael B. Stephens

Luleå tekniska universitet; Geovetenskap och miljöteknik
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