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Attempted break-up of Rodinia at 850 Ma: geochronological evidence from the Seve-Kalak Superterrane, Scandinavian Caledonides

Paulsson, Oskar LU and Andréasson, Per-Gunnar LU (2002) In Journal of the Geological Society 159(6). p.751-761
Abstract
Lower thrust sheets of the Scandinavian Caledonides derive from the margin of Baltica, which was imbricated during Early Palaeozoic closure of oceans formed during separation of the Baltica, Laurentia and Siberia cratons. At Vistas (Kebnekaise Mts), the Seve Nappe Complex preserves rare lenses of a dolerite-intruded granite formed by anatexis during emplacement of gabbro into metasedimentary rocks. Ion microprobe U-Pb dating of prismatic zircons from the granite yielded an age of 845 +/- 14 Ma (mean square weighed deviation (MSWD) 1.15), interpreted to date magmatic crystallization. Cores of complex crystals indicate protolith ages of 1778 +/- 11 Ma (MSWD 0.86); one core yielded an Archaean age. From narrow rims, a 605 +/- 42 Ma... (More)
Lower thrust sheets of the Scandinavian Caledonides derive from the margin of Baltica, which was imbricated during Early Palaeozoic closure of oceans formed during separation of the Baltica, Laurentia and Siberia cratons. At Vistas (Kebnekaise Mts), the Seve Nappe Complex preserves rare lenses of a dolerite-intruded granite formed by anatexis during emplacement of gabbro into metasedimentary rocks. Ion microprobe U-Pb dating of prismatic zircons from the granite yielded an age of 845 +/- 14 Ma (mean square weighed deviation (MSWD) 1.15), interpreted to date magmatic crystallization. Cores of complex crystals indicate protolith ages of 1778 +/- 11 Ma (MSWD 0.86); one core yielded an Archaean age. From narrow rims, a 605 +/- 42 Ma metamorphic age is obtained, and is interpreted to reflect the emplacement of the extensive Vendian rift magmatic dolerite dyke swarm. The age pattern allows correlation with a previously dated magmatic complex within the equivalent Kalak Nappe Complex 300 km to the north. Bimodal magmatic complexes with this age pattern do not occur within the basement of the Caledonide foreland, nor elsewhere within the Baltic Shield. However, recent reinterpretations of the Knoydartian event in Scotland as rift related invites correlation with the West Highland Granite Gneiss, which intruded Moine metasedimentary rocks at c. 870 Ma. In Central Taimyr, 850-900 Ma granites of continental crustal derivation and with 1800-1900 Ma Sm-Nd model age occur associated with c. 740 Ma plagiogranites. Using recent palaeogeographical reconstructions, we interpret the evidence of 850-900 Ma magmatism, in Scandinavia, Scotland and Taimyr as bimodal rift magmatism in connected arms during an attempted break-up of Rodinia. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Neoproterozoic, Scandinavia, Caledonides, Rodinia, rifting, ion probe
in
Journal of the Geological Society
volume
159
issue
6
pages
751 - 761
publisher
The Geological Society Publishing House
external identifiers
  • wos:000179092700012
  • scopus:84862762756
ISSN
2041-479X
language
English
LU publication?
yes
id
18aa9a66-8bb1-4e57-b1e0-27469e5f09ef (old id 324184)
alternative location
http://jgs.geoscienceworld.org/cgi/content/abstract/159/6/751
date added to LUP
2007-11-08 12:30:47
date last changed
2017-05-28 03:42:20
@article{18aa9a66-8bb1-4e57-b1e0-27469e5f09ef,
  abstract     = {Lower thrust sheets of the Scandinavian Caledonides derive from the margin of Baltica, which was imbricated during Early Palaeozoic closure of oceans formed during separation of the Baltica, Laurentia and Siberia cratons. At Vistas (Kebnekaise Mts), the Seve Nappe Complex preserves rare lenses of a dolerite-intruded granite formed by anatexis during emplacement of gabbro into metasedimentary rocks. Ion microprobe U-Pb dating of prismatic zircons from the granite yielded an age of 845 +/- 14 Ma (mean square weighed deviation (MSWD) 1.15), interpreted to date magmatic crystallization. Cores of complex crystals indicate protolith ages of 1778 +/- 11 Ma (MSWD 0.86); one core yielded an Archaean age. From narrow rims, a 605 +/- 42 Ma metamorphic age is obtained, and is interpreted to reflect the emplacement of the extensive Vendian rift magmatic dolerite dyke swarm. The age pattern allows correlation with a previously dated magmatic complex within the equivalent Kalak Nappe Complex 300 km to the north. Bimodal magmatic complexes with this age pattern do not occur within the basement of the Caledonide foreland, nor elsewhere within the Baltic Shield. However, recent reinterpretations of the Knoydartian event in Scotland as rift related invites correlation with the West Highland Granite Gneiss, which intruded Moine metasedimentary rocks at c. 870 Ma. In Central Taimyr, 850-900 Ma granites of continental crustal derivation and with 1800-1900 Ma Sm-Nd model age occur associated with c. 740 Ma plagiogranites. Using recent palaeogeographical reconstructions, we interpret the evidence of 850-900 Ma magmatism, in Scandinavia, Scotland and Taimyr as bimodal rift magmatism in connected arms during an attempted break-up of Rodinia.},
  author       = {Paulsson, Oskar and Andréasson, Per-Gunnar},
  issn         = {2041-479X},
  keyword      = {Neoproterozoic,Scandinavia,Caledonides,Rodinia,rifting,ion probe},
  language     = {eng},
  number       = {6},
  pages        = {751--761},
  publisher    = {The Geological Society Publishing House},
  series       = {Journal of the Geological Society},
  title        = {Attempted break-up of Rodinia at 850 Ma: geochronological evidence from the Seve-Kalak Superterrane, Scandinavian Caledonides},
  volume       = {159},
  year         = {2002},
}