Timing of magmatism and migmatization in the 2.0–1.8 Ga accretionary Svecokarelian orogen, south-central Sweden

Johansson, Åke; Stephens, Michael B.

doi:10.1007/s00531-016-1359-3

Cited by 12 publications

(12 citation statements)

References 52 publications

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“…The location of E6-1 and other drill sites of interest for this study are marked with red dots. Drill sites: Fr Frigsarve, N När from 1.84 to 1.75 Ga (Öhlander and Zuber 1988;Stephens and Andersson 2015;Johansson and Stephens 2017). The granites occur as two principal types: large homogeneous massifs of coarse-grained porphyritic K-feldspar granites (e.g.…”

Section: Fennoscandian Frameworkmentioning

confidence: 99%

“…However, amphibolite is the dominating supracrustal rock in the southernmost segment (Valdemarsvik area). Subsequent igneous activity related to mafic underplating and anatexis took place at 1.87-1.85 Ga and 1.84-1.81 Ga and partly overlaps in space and time with the emplacement of the TIB felsic intrusive rocks (Stephens and Andersson 2015;Johansson and Stephens 2017). Late Svecofennian migmatites and pegmatites are mostly observed in the southeastern and northern parts of the Bergslagen area (Andersson 1997;Hermansson et al 2007;Stephens et al 2009).…”

Section: Bergslagen Lithotectonic Unitmentioning

confidence: 99%

“…The southern parts of the Bergslagen lithotectonic unit were also subject to high-grade metamorphism involving partial melting with development of migmatites. Mineral parageneses with andalusite (or sillimanite), cordierite and garnet in aluminous rocks, as well as geobarometric and geothermometric data indicate metamorphism under low-P conditions at 4-6 kbar (Stephens et al 2009;Johansson and Stephens 2017). Stephens and Andersson (2015) and Andersson et al (2006) showed that two metamorphic events, associated with anatexis under low-pressure conditions in the central and southern parts of the Bergslagen lithotectonic unit, took place at ≤ 1.87 Ga (M1) and 1.84-1.81 Ga (M2) intimately associated with the D1 and D2 deformation events (accordingly).…”

Section: Bergslagen Lithotectonic Unitmentioning

confidence: 99%

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Tracing the SW border of the Svecofennian Domain in the Baltic Sea region: evidence from petrology and geochronology from a granodioritic migmatite

Salin

Woodard

Sundblad³

2021

Int J Earth Sci (Geol Rundsch)

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Geological investigations of a part of the crystalline basement in the Baltic Sea have been performed on a drill core collected from the depth of 1092–1093 m beneath the Phanerozoic sedimentary cover offshore the Latvian/Lithuanian border. The sample was analyzed for geochemistry and dated with the SIMS U–Pb zircon method. Inherited zircon cores from this migmatized granodioritic orthogneiss have an age of 1854 ± 15 Ma. Its chemical composition and age are correlated with the oldest generation of granitoids of the Transscandinavian Igneous Belt (TIB), which occur along the southwestern margin of the Svecofennian Domain in the Fennoscandian Shield and beneath the Phanerozoic sedimentary cover on southern Gotland and in northwestern Lithuania. It is suggested that the southwestern border of the Svecofennian Domain is located at a short distance to the SW of the investigated drill site. The majority of the zircon population shows that migmatization occurred at 1812 ± 5 Ma, with possible evidence of disturbance during the Sveconorwegian orogeny.

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Section: Fennoscandian Frameworkmentioning

confidence: 99%

Section: Bergslagen Lithotectonic Unitmentioning

confidence: 99%

Section: Bergslagen Lithotectonic Unitmentioning

confidence: 99%

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Tracing the SW border of the Svecofennian Domain in the Baltic Sea region: evidence from petrology and geochronology from a granodioritic migmatite

Salin

Woodard

Sundblad³

2021

Int J Earth Sci (Geol Rundsch)

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“…1.84 to 1.79 Ga (D2 and M2; Fig. 1; Stephens and Andersson, 2015;Johansson and Stephens, 2017). The early plutonic rocks intruded a thick succession of supracrustal rocks, deposited at different stages during the evolution of a back-arc basin developed on continental crust (Allen et al, 1996).…”

Section: Regional Geologymentioning

confidence: 99%

The Lovisa Stratiform Zn-Pb Deposit, Bergslagen, Sweden: Structure, Stratigraphy, and Ore Genesis

et al. 2018

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Medium-to high-grade metamorphosed, 1.9 Ga, stratiform, syngenetic Zn-Pb ± Ag sulfide deposits constitute an economically important type of ore deposit in the Bergslagen lithotectonic unit of the Fennoscandian Shield. The Lovisa Zn-Pb deposit occurs in a metamorphosed succession of rhyolitic ash-siltstone, rhyolitic mass flow deposits, limestone, and Fe formation, deposited at a stage of waning volcanism in Bergslagen. Accessory graphite, absence of Ce anomalies in shale-normalized rare earth element (REE) data, and absence of hematite in Mn-rich Fe formations stratigraphically below the Lovisa Zn-Pb deposit indicate a suboxic-anoxic depositional environment. The uppermost Mn-rich Fe formation contains disseminated, inferred syngenetic Pb-Ag mineralization with mainly negative δ 34 S values in sphalerite and galena (-6.1 to-1.9‰). Deposition of this Fe formation terminated during a pulse of explosive felsic volcanism. The Lovisa Zn-Pb deposit is interpreted to have formed in an alkali-rich brine pool developed immediately after this volcanic event, based on lithogeochemical and stratigraphic evidence. The first stage of mineralization deposited stratiform sphalerite mineralization with mainly positive δ 34 S values (-0.9 to 4.7‰). This was succeeded by deposition of more sphalerite-galena stratiform mineralization with δ 34 S values close to 0‰ (-2.1 to 1.5‰). The more galena-rich mineralization partitioned strain and was partly remobilized during later ductile deformation. The stratigraphic context, sulfide mineralogy, S isotopes, and alteration geochemistry suggest that the metalliferous fluids and the depositional environment were H2S deficient (S poor or SO 4 2dominant). The source of S is interpreted to have been a mixture of H2S derived from bacterial and thermochemical seawater sulfate reduction and S derived from leaching of volcanic rocks, with the latter becoming more important over time. Lovisa formed in a setting where basin subsidence was periodically punctuated by the deposition of thick, syneruptive felsic volcaniclastic mass flow deposits. Coeval volcanism was likely important for driving hydrothermal activity and supplying a reservoir of metals and S. However, the high rate of deposition of volcaniclastic sediment in Bergslagen also precluded the establishment of long-lived, deep, and anoxic environments favorable for accumulation of organic matter and H2S. This stratigraphic pattern is common in Bergslagen and may explain why large stratiform Zn-Pb deposits are uncommon in the region and restricted to the uppermost part of the metavolcanic succession, directly stratigraphically beneath postvolcanic pelitic rocks.

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“…Most of the currently exposed crust formed in connection with subductionrelated magmatism at 1.91-1.87 Ga, including ore-bearing felsic to intermediate metavolcanic rocks and associated metasediments, as well as early-orogenic intrusive rocks [the 1.91-1.87 Ga Granitoid-Dioritoid-Gabbroid (GDG) suite of Stephens et al (2009)]. This was followed closely by pervasive deformation and low-pressure metamorphism, dominantly in amphibolite facies, with associated migmatization at 1.87-1.85 Ga (Stephens et al 2009;Stephens and Andersson 2015;Johansson and Stephens 2017;Stephens and Jansson 2020). After an apparently quieter 'intra-orogenic' period, there was a second period of metamorphism at 1.82-1.75 Ga, more prevalent further south than in the Hedesunda area (Stephens and Andersson 2015), and intrusion of late-orogenic granites [Granite-Pegmatite (GP) suite Fig.…”

Section: Introduction and Geological Backgroundmentioning

confidence: 99%

The Paleoproterozoic Hedesunda granite complex, east-central Sweden, a composite intrusion

Johansson

2020

Int J Earth Sci (Geol Rundsch)

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The Hedesunda granite complex covers a rectangular area of ca 800 km2 within the Bergslagen lithotectonic unit of the Paleoproterozoic Svecofennian orogen in east-central Sweden. It is dominated by coarse porphyritic and generally undeformed granitoids whose position within the Svecofennian orogenic evolution has been controversial. New U–Pb SIMS dating of zircon confirms earlier TIMS results, showing that it is a composite intrusion made up of an older phase at ca 1865 Ma, forming the bulk of the massif, and a younger phase at ca 1785 Ma, forming a circular intrusion in the north-central area and an elongated body further west. The two generations have very different geochemistry. The older Hedesunda I intrusion ranges from diorite through tonalite and granodiorite to granite in composition, is dominantly metaluminous, calc-alkaline, magnesian, I-type and volcanic arc-related, and probably formed by melting of juvenile Svecofennian lower crust due to basaltic underplating during an extensional ‘intra-orogenic’ phase shortly after the main subduction-related early-orogenic Svecofennian magmatism. The younger Hedesunda II intrusions are purely granitic, dominantly peraluminous, alkali-calcic, K-rich, and ferroan, with A-type and within-plate-type characteristics, and formed penecontemporaneously with post-collisional shoshonitic intrusions in southern Finland, again presumably by crustal melting due to basaltic underplating in an extensional setting towards the end of the Svecofennian orogeny.

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Timing of magmatism and migmatization in the 2.0–1.8 Ga accretionary Svecokarelian orogen, south-central Sweden

Cited by 12 publications

References 52 publications

Tracing the SW border of the Svecofennian Domain in the Baltic Sea region: evidence from petrology and geochronology from a granodioritic migmatite

Tracing the SW border of the Svecofennian Domain in the Baltic Sea region: evidence from petrology and geochronology from a granodioritic migmatite

The Lovisa Stratiform Zn-Pb Deposit, Bergslagen, Sweden: Structure, Stratigraphy, and Ore Genesis

The Paleoproterozoic Hedesunda granite complex, east-central Sweden, a composite intrusion

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