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Seve terranes of the Kebnekaise Mts., Swedish Caledonides, and their amalgamation, accretion and affinity

Andréasson, Per Gunnar LU ; Allen, Ann; Aurell, Oskar; Boman, Daniel; Ekestubbe, Jonas; Goerke, Ute; Lundgren, Anders; Nilsson, Patrik and Sandelin, Stefan (2018) In GFF p.1-28
Abstract

A major allochthon of the Scandinavian Caledonides, the Seve belt has traditionally been considered to be derived from the rifted margin and continent-ocean transition (COT) of Baltica. However, geochronological results obtained from its inferred northern equivalent, the Kalak Nappe Complex (KNC), have been taken to indicate an exotic affinity of this complex and of also Seve terranes, an interpretation adopted in recent palaeogeographic models. In the Kebnekaise Mts., the COT is represented by the Kebnekaise terrane composed of amphibolitized dykes of gabbro and dolerite of depleted magma source and rare felsic and ultramafic rocks. Coronitic dolerite and gabbro with abundant rutile suggest high pressures before or during amalgamation... (More)

A major allochthon of the Scandinavian Caledonides, the Seve belt has traditionally been considered to be derived from the rifted margin and continent-ocean transition (COT) of Baltica. However, geochronological results obtained from its inferred northern equivalent, the Kalak Nappe Complex (KNC), have been taken to indicate an exotic affinity of this complex and of also Seve terranes, an interpretation adopted in recent palaeogeographic models. In the Kebnekaise Mts., the COT is represented by the Kebnekaise terrane composed of amphibolitized dykes of gabbro and dolerite of depleted magma source and rare felsic and ultramafic rocks. Coronitic dolerite and gabbro with abundant rutile suggest high pressures before or during amalgamation with the underlying Mårma terrane, composed of quartzofeldspathic gneisses intruded by mafic and granitic rocks, the latter including a previously dated c. 845 Ma-old granite. The granite mingled with mildly alkaline dolerites chemically similar to transitional basalts of continental rifts. Following emplacement at shallow (andalusite stability) crustal levels, the igneous complex and host rocks underwent extensive deformation, metamorphism within the sillimanite-kyanite stability field and local migmatization. The Kebnekaise and Mårma terranes amalgamated in early Ordovician as indicated by the U-Pb age of 487±7 Ma obtained from titanite fabrics of deformed granite in thrust vicinity, and by 40Ar-39Ar results. The pressure increase in both terranes suggests that amalgamation occurred during initial subduction and imbrication. Correlation of the Mårma terrane with the KNC is discussed. Results obtained in this study give no reason to ascribe an exotic affinity to the Seve terranes of the Kebnekaise Mts.

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Contribution to journal
publication status
epub
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in
GFF
pages
28 pages
publisher
Taylor & Francis
external identifiers
  • scopus:85048009744
ISSN
1103-5897
DOI
10.1080/11035897.2018.1470200
language
English
LU publication?
yes
id
ba04befc-84b3-484e-89ba-8c102c7bab13
date added to LUP
2018-06-13 13:24:12
date last changed
2018-10-03 10:57:16
@article{ba04befc-84b3-484e-89ba-8c102c7bab13,
  abstract     = {<p>A major allochthon of the Scandinavian Caledonides, the Seve belt has traditionally been considered to be derived from the rifted margin and continent-ocean transition (COT) of Baltica. However, geochronological results obtained from its inferred northern equivalent, the Kalak Nappe Complex (KNC), have been taken to indicate an exotic affinity of this complex and of also Seve terranes, an interpretation adopted in recent palaeogeographic models. In the Kebnekaise Mts., the COT is represented by the Kebnekaise terrane composed of amphibolitized dykes of gabbro and dolerite of depleted magma source and rare felsic and ultramafic rocks. Coronitic dolerite and gabbro with abundant rutile suggest high pressures before or during amalgamation with the underlying Mårma terrane, composed of quartzofeldspathic gneisses intruded by mafic and granitic rocks, the latter including a previously dated c. 845 Ma-old granite. The granite mingled with mildly alkaline dolerites chemically similar to transitional basalts of continental rifts. Following emplacement at shallow (andalusite stability) crustal levels, the igneous complex and host rocks underwent extensive deformation, metamorphism within the sillimanite-kyanite stability field and local migmatization. The Kebnekaise and Mårma terranes amalgamated in early Ordovician as indicated by the U-Pb age of 487±7 Ma obtained from titanite fabrics of deformed granite in thrust vicinity, and by <sup>40</sup>Ar-<sup>39</sup>Ar results. The pressure increase in both terranes suggests that amalgamation occurred during initial subduction and imbrication. Correlation of the Mårma terrane with the KNC is discussed. Results obtained in this study give no reason to ascribe an exotic affinity to the Seve terranes of the Kebnekaise Mts.</p>},
  author       = {Andréasson, Per Gunnar and Allen, Ann and Aurell, Oskar and Boman, Daniel and Ekestubbe, Jonas and Goerke, Ute and Lundgren, Anders and Nilsson, Patrik and Sandelin, Stefan},
  issn         = {1103-5897},
  language     = {eng},
  month        = {06},
  pages        = {1--28},
  publisher    = {Taylor & Francis},
  series       = {GFF},
  title        = {Seve terranes of the Kebnekaise Mts., Swedish Caledonides, and their amalgamation, accretion and affinity},
  url          = {http://dx.doi.org/10.1080/11035897.2018.1470200},
  year         = {2018},
}