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Multistage growth and reworking of the Palaeoproterozoic crust in the Bergslagen area, southern Sweden: evidence from U-Pb geochronology

Andersson, Ulf B. ; Högdahl, Karin LU ; Sjostrom, Hakan and Bergman, Stefan (2006) In Geological Magazine 143(5). p.679-697
Abstract
The Svecofennian Domain of the Fennoscandian Shield constitutes a considerable volume of Palaeoproterozoic crustal growth, 2.1-1.86 Ga ago, in between the Archaean craton in the NE and the 1.85-1.65 Ga Transscandinavian Igneous Belt (TIB) in the south and west. The Bergslagen area is a classical ore province located in the southwestern part of the Svecofennian Domain of southcentral Sweden. Its northern part is dominated by volcanic and plutonic rocks of a magmatic are with continental affinity, while the SE part is made up by a sedimentary basin. The Bergslagen area shows a metamorphic zonation from lower to middle amphibolite facies in the north to upper amphibolite facies and locally granulite facies in the south; a small greenschist... (More)
The Svecofennian Domain of the Fennoscandian Shield constitutes a considerable volume of Palaeoproterozoic crustal growth, 2.1-1.86 Ga ago, in between the Archaean craton in the NE and the 1.85-1.65 Ga Transscandinavian Igneous Belt (TIB) in the south and west. The Bergslagen area is a classical ore province located in the southwestern part of the Svecofennian Domain of southcentral Sweden. Its northern part is dominated by volcanic and plutonic rocks of a magmatic are with continental affinity, while the SE part is made up by a sedimentary basin. The Bergslagen area shows a metamorphic zonation from lower to middle amphibolite facies in the north to upper amphibolite facies and locally granulite facies in the south; a small greenschist area exists in the west. Identifying the age spectra of inherited components, magmatic crystallization, as well as metamorphic episodes, provide important constraints on the geodynamic evolution of this centrally located piece of the Shield. U-Pb zircon SIMS data presented in this paper complement the previous, regionally scattered TIMS data from this area. Magmatic zircons from two felsic metavolcanic rocks and two amphibolites (metagabbros) yield 1888 +/- 12, 1892 +/- 7 and 1887 +/- 5, 1895 +/- 5 Ma, respectively; i.e. within the 1.91-1.86 Ga range previously obtained for Early Svecofennian magmatism in Bergslagen. An augen gneiss from southern Bergslagen, assigned to the earliest TIB generation, yield an intrusive age of 1855 6 Ma. Metamorphic monazites from the same rock indicate that deformation and elevated thermal activity prevailed 1.83-1.82 Ga ago (TIMS). Metamorphic zircons in high-grade metasedimentary rocks from the south and west yield ages of 1793 5 and 1804 10 Ma, in accordance with ages for regional peak metamorphism and migmatite formation found elsewhere in the southern Svecofennian province of Sweden. More importantly, a few zircon crystals and overgrowths in rocks from the north indicate an early metamorphic episode at c. 1.87 Ga, indicating that Bergslagen has experienced two major metamorphic events. Detrital and inherited zircons span the range 2.78-1.90 Ga, with an apparent gap at 2.45-2.1 Ga, which further emphasize previous observations of a major juvenile (< 2.1 Ga) and a minor Archaean provenance. This, and in particular the 1.94-1.91 Ga crystals present in the c. 1.89 Ga amphibolites, support the suggestion of a former Palaeoproterozoic pre-1.91 Ga crust in the Bergslagen area. (Less)
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Contribution to journal
publication status
published
subject
keywords
Svecofennian, Bergslagen, TIMS, SIMS, geochronology, zircon, metamorphic, inherited, magmatic
in
Geological Magazine
volume
143
issue
5
pages
679 - 697
publisher
Cambridge University Press
external identifiers
  • wos:000241142600006
  • scopus:33748470344
ISSN
0016-7568
DOI
10.1017/S0016756806002494
language
English
LU publication?
yes
id
79be4a8d-02ce-406c-86eb-63a008f490f8 (old id 388444)
date added to LUP
2016-04-01 11:51:10
date last changed
2021-08-18 04:18:46
@article{79be4a8d-02ce-406c-86eb-63a008f490f8,
  abstract     = {The Svecofennian Domain of the Fennoscandian Shield constitutes a considerable volume of Palaeoproterozoic crustal growth, 2.1-1.86 Ga ago, in between the Archaean craton in the NE and the 1.85-1.65 Ga Transscandinavian Igneous Belt (TIB) in the south and west. The Bergslagen area is a classical ore province located in the southwestern part of the Svecofennian Domain of southcentral Sweden. Its northern part is dominated by volcanic and plutonic rocks of a magmatic are with continental affinity, while the SE part is made up by a sedimentary basin. The Bergslagen area shows a metamorphic zonation from lower to middle amphibolite facies in the north to upper amphibolite facies and locally granulite facies in the south; a small greenschist area exists in the west. Identifying the age spectra of inherited components, magmatic crystallization, as well as metamorphic episodes, provide important constraints on the geodynamic evolution of this centrally located piece of the Shield. U-Pb zircon SIMS data presented in this paper complement the previous, regionally scattered TIMS data from this area. Magmatic zircons from two felsic metavolcanic rocks and two amphibolites (metagabbros) yield 1888 +/- 12, 1892 +/- 7 and 1887 +/- 5, 1895 +/- 5 Ma, respectively; i.e. within the 1.91-1.86 Ga range previously obtained for Early Svecofennian magmatism in Bergslagen. An augen gneiss from southern Bergslagen, assigned to the earliest TIB generation, yield an intrusive age of 1855 6 Ma. Metamorphic monazites from the same rock indicate that deformation and elevated thermal activity prevailed 1.83-1.82 Ga ago (TIMS). Metamorphic zircons in high-grade metasedimentary rocks from the south and west yield ages of 1793 5 and 1804 10 Ma, in accordance with ages for regional peak metamorphism and migmatite formation found elsewhere in the southern Svecofennian province of Sweden. More importantly, a few zircon crystals and overgrowths in rocks from the north indicate an early metamorphic episode at c. 1.87 Ga, indicating that Bergslagen has experienced two major metamorphic events. Detrital and inherited zircons span the range 2.78-1.90 Ga, with an apparent gap at 2.45-2.1 Ga, which further emphasize previous observations of a major juvenile (&lt; 2.1 Ga) and a minor Archaean provenance. This, and in particular the 1.94-1.91 Ga crystals present in the c. 1.89 Ga amphibolites, support the suggestion of a former Palaeoproterozoic pre-1.91 Ga crust in the Bergslagen area.},
  author       = {Andersson, Ulf B. and Högdahl, Karin and Sjostrom, Hakan and Bergman, Stefan},
  issn         = {0016-7568},
  language     = {eng},
  number       = {5},
  pages        = {679--697},
  publisher    = {Cambridge University Press},
  series       = {Geological Magazine},
  title        = {Multistage growth and reworking of the Palaeoproterozoic crust in the Bergslagen area, southern Sweden: evidence from U-Pb geochronology},
  url          = {http://dx.doi.org/10.1017/S0016756806002494},
  doi          = {10.1017/S0016756806002494},
  volume       = {143},
  year         = {2006},
}