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Paleoproterozoic (1.9-1.8 Ga) syn-orogenic magmatism, sedimentation and mineralization in the Bergslagen lithotectonic unit, Svecokarelian Orogen

Michael B. Stephens and Nils F. Jansson
Paleoproterozoic (1.9-1.8 Ga) syn-orogenic magmatism, sedimentation and mineralization in the Bergslagen lithotectonic unit, Svecokarelian Orogen (in Sweden; lithotectonic framework, tectonic evolution and mineral resources, M. B. Stephens (editor) and J. Bergman Weihed (editor))
Memoirs of the Geological Society of London (2020) 50: 155-206

Abstract

Felsic volcanic rocks (c. 1.91-1.89 Ga) and interlayered limestone, hosting Zn-Pb-Ag + or - Cu + or - Au + or - Fe sulphide and Fe oxide deposits, characterize the Bergslagen lithotectonic unit, Svecokarelian orogen, south-central Sweden. Three sulphide mines are currently in operation. Siliciclastic sedimentary rocks stratigraphically envelop this volcanic succession and all the rocks are intruded by a dominant calc-alkaline, c. 1.91-1.87 Ga plutonic suite. Fabric development associated with folding and localized shear deformation followed at c. 1.87-1.86 Ga (D (sub 1) ) and was succeeded by strongly partitioned strain (D (sub 2) ). Dextral transpression along steeply dipping, WNW-ESE or NW-SE shear zones prevailed in the northern and southern domains, whereas major folding with east to northeasterly axial surface traces and shearing along limbs occurred in the central domain. Open folding (D (sub 3) ) subsequently affected the western areas. Polyphase metamorphism under low-pressure and variable temperature conditions included anatexis at c. 1.86 Ga (M (sub 1) ) and 1.84-1.80 Ga (M (sub 2) ). More alkali-calcic magmatic activity, combined with the emplacement of anatectic granite and pegmatite, overlapped and succeeded the M (sub 1) and M (sub 2) migmatization events at c. 1.87-1.83 Ga and c. 1.82-1.75 Ga, respectively. The younger granites are genetically linked in part to W skarn deposits and host Mo sulphide mineralization. Switching between retreating and advancing subduction systems during three separate tectonic cycles along a convergent, active continental plate margin is inferred.


ISSN: 0435-4052
Coden: GSLMAD
Serial Title: Memoirs of the Geological Society of London
Serial Volume: 50
Title: Paleoproterozoic (1.9-1.8 Ga) syn-orogenic magmatism, sedimentation and mineralization in the Bergslagen lithotectonic unit, Svecokarelian Orogen
Title: Sweden; lithotectonic framework, tectonic evolution and mineral resources
Author(s): Stephens, Michael B.Jansson, Nils F.
Author(s): Stephens, M. B.editor
Author(s): Bergman Weihed, J.editor
Affiliation: Lulea University of Technology, Division of Geosciences and Environmental Engineering, Lulea, Sweden
Affiliation: Lulea University of Technology, Lulea, Sweden
Pages: 155-206
Published: 2020
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 172
Accession Number: 2020-042949
Categories: Igneous and metamorphic petrologySolid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch maps
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 2020
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