The Bergslagen ore province, Sweden: Review and update of an accreted orocline, 1.9–1.8Ga BP

Beunk, F.F.; Kuipers, Gerrit

doi:10.1016/j.precamres.2012.05.007

Cited by 34 publications

(58 citation statements)

References 58 publications

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“…The D 1 and D 2 structures identified in this study fall well within this regional pattern and are inferred to have formed during the separate pulses of transpressive deformation at the closing stages of the two tectonic cycles recognized within the Bergslagen lithotectonic unit (Stephens et al 2009;Beunk and Kuipers 2012;Stephens and Andersson 2015). Beunk and Kuipers (2012) included the two phases of transtensional or extensional strain prior to and between the major phases of transpressional ductile fabric development and folding in their structural evolutionary scheme; D 1 and D 2 in this study corresponding to their D 2 and D 4 , respectively.…”

Section: Discussionsupporting

confidence: 70%

“…Polyphase ductile deformation in a regional structural and metamorphic context An early major folding event (F 1 ), locally with large-scale stratigraphic inversion of the bedrock, has been recognized in parts of the Bergslagen lithotectonic unit, but a second generation of folding (F 2 ), with deformation of the regional planar grain-shape fabric and continued development of linear structures, is the most prominent structural feature (Stephens et al 2009, Beunk andKuipers 2012). The second generation of folding is apparent on different scales, including the regional scale (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…The 2.0-1.8 Ga Svecokarelian orogeny in this lithotectonic unit involved two tectonic cycles, from 1.91-1.86 Ga and 1.86-1.82 Ga, dominated by transtensional or extensional deformation (Stephens et al 2009;Beunk and Kuipers 2012;Stephens and Andersson 2015). Transpressive deformation occurred around 1.87-1.86 Ga (Hermansson et al 2007(Hermansson et al , 2008a; Stephens et al 2009;Stephens and Andersson 2015) and 1.84-1.82 Ga (Beunk andKuipers 2012, Stephens andAndersson 2015), during the waning stages of each cycle. Subsequent ductile strain was restricted to shear zones (Hermansson et al 2008b).…”

Section: Geological Setting Regional Geological Settingmentioning

confidence: 99%

“…1a). Tight to isoclinal F 2 folds on different scales with an E-W to NE-SW axial surface trace and steeply dipping, ductile shear zones with a similar strike dominate this domain (Stephens et al 2009;Beunk and Kuipers 2012).…”

Section: Geological Setting Regional Geological Settingmentioning

confidence: 99%

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3D modelling and sheath folding at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit and implications for exploration in a 1.9 Ga ore district, Fennoscandian Shield, Sweden

2016

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Altered and mineralized rocks at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit, situated in the Palaeoproterozoic Bergslagen ore district in the southwestern part of the Fennoscandian Shield, have been metamorphosed at low-pressure, amphibolite-facies conditions and affected by ductile deformation. Using combined surface mapping of lithology and structure, drill core logging and microstructural work, the polyphase (D 1 and D 2 ) ductile deformation is demonstrated and a 3D model for the deposit created. Mineral associations include quartz, biotite, cordierite, anthophyllite, and minor almandine, andalusite and chlorite in silicate-rich altered rock, calcite or dolomite in marble and tremolite-actinolite or diopside-hedenbergite in skarn. The silicate minerals show varying growth patterns during the different phases of the tectonothermal evolution, with considerable static grain growth occurring between D 1 and D 2 , and even after D 2 . F 2 sheath folding along axes that plunge steeply to the SSE, parallel to a mineral stretching lineation and the dip direction of the S 2 foliation, is suggested as a key deformation mechanism forming steeply plunging, cone-to rod-shaped mineralized bodies. This contrasts with a previous structural model invoking fold interference. A major shear zone with talc-chlorite-(quartz-biotite) mineral association separates the northern and southern structural domains at the deposit and bounds the polymetallic massive sulphides to the north.

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Section: Discussionsupporting

confidence: 70%

Section: Discussionmentioning

confidence: 99%

Section: Geological Setting Regional Geological Settingmentioning

confidence: 99%

Section: Geological Setting Regional Geological Settingmentioning

confidence: 99%

See 2 more Smart Citations

3D modelling and sheath folding at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit and implications for exploration in a 1.9 Ga ore district, Fennoscandian Shield, Sweden

2016

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“…The tectonic setting during each cycle involved a shift between retreating and advancing arc modes along a convergent active continental margin, transtension occurred in the retreating mode throughout the larger part of each cycle. Each transtensional stage was followed by shorter periods of transpression (D 1 and D 2 , respectively) in the advancing mode, around 1.87-1.86 Ga and 1.84-1.82 Ga (Hermansson et al, 2007(Hermansson et al, , 2008aStephens et al, 2009;Beunk and Kuipers, 2012;Stephens and Andersson, 2015). This orogenic development resulted in polyphase deformation and metamorphism under low-P, greenschist-to amphiboliteand locally granulite-facies conditions (Stephens et al, 2009).…”

Section: Regional Geological Settingmentioning

confidence: 99%

Time constraints on magmatism, mineralisation and metamorphism at the Falun base metal sulphide deposit, Sweden, using U–Pb geochronology on zircon and monazite

Kampmann

Stephens

Ripa

et al. 2016

Precambrian Research

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a b s t r a c t U-Th-Pb (zircon and monazite) ion probe data have provided constraints on the timing of emplacement and metamorphism of magmatic rocks close to the Palaeoproterozoic, Falun base metal sulphide deposit in the Bergslagen lithotectonic unit, Fennoscandian Shield, Sweden, and, thereby the timing of mineralisation. Hydrothermal alteration and mineralisation at Falun are constrained to a short interval of several million years between a 207 Pb/ 206 Pb weighted average age of 1894 ± 3 Ma for a rhyolitic sub-volcanic rock in the felsic volcanic to sub-volcanic host rock suite, and a 207 Pb/ 206 Pb weighted average age of 1891 ± 3 Ma for a post-sulphide, porphyritic dacite dyke. Magmatism also included the emplacement of granite plutons with igneous crystallization ages of 1894 ± 3, 1894 ± 2 Ma and 1893 ± 3 Ma. The felsic sub-volcanic to volcanic activity and the emplacement of dacite dykes and granite plutons overlap in age within their respective analytical uncertainties, indicating hydrothermal alteration and sulphide mineralisation inside a narrow time span of intense magmatic activity, and burial of the supracrustal rocks. Two distinct patchy and homogeneous metamorphic monazite types in a felsic volcanic rock around and hydrothermally altered rocks at the Falun deposit yield 207 Pb/ 206 Pb weighted average ages of 1831 ± 8 Ma and 1822 ± 5 Ma, respectively. These ages fall well within the temporal range of a younger 1.84-1.81 Ga (M 2 ) metamorphic episode during the 2.0-1.8 Ga Svecokarelian orogeny, with the older episode (M 1 ) inside the Bergslagen lithotectonic unit at around 1.86 Ga. This shows the major influence of the M 2 event in the north-western part of this unit, leading to a complete resetting of the U-Th-Pb isotope system in monazite.

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Evidence of permafrost in the Paleoproterozoic (c. 1.9 Ga) of Central Sweden

Vandenberghe

Kuipers²,

Beunk

et al. 2020

Permafrost & Periglacial

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This paper reports on an ice‐wedge pseudomorph that formed and is preserved in metavolcanic host material that was later transformed to metamorphic solid bedrock. It has been dated to 1,895 ± 5 Ma by U–Pb geochronology of zircon in the bedrock, an Early Proterozoic age. Detailed observation of the deformation structures of the wedge points to an ice‐wedge pseudomorph based on typical downbending around the wedge and vertical lamination in the inner part of the wedge due to slumping into the wedge after the ice melted, along with a few remains of lateral pressure structures (such as folds and upturned strata) in the adjacent host sediment. The interpretation of the wedge structure as an ice‐wedge pseudomorph confirms previous work on this topic. This ice‐wedge pseudomorph demonstrates for the first time the existence of permafrost at c. 1.9 Ga. It indicates that permafrost and associated conditions were present in lowlands at low latitude at discrete time intervals early in Earth’s history. Although some caution should be applied, mean annual air temperature appears to have been slightly below the freezing point at that time.

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The Bergslagen ore province, Sweden: Review and update of an accreted orocline, 1.9–1.8Ga BP

Cited by 34 publications

References 58 publications

3D modelling and sheath folding at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit and implications for exploration in a 1.9 Ga ore district, Fennoscandian Shield, Sweden

3D modelling and sheath folding at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit and implications for exploration in a 1.9 Ga ore district, Fennoscandian Shield, Sweden

Time constraints on magmatism, mineralisation and metamorphism at the Falun base metal sulphide deposit, Sweden, using U–Pb geochronology on zircon and monazite

Evidence of permafrost in the Paleoproterozoic (c. 1.9 Ga) of Central Sweden

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