Continental margin magmatism and migmatisation in the west-central Fennoscandian Shield
(2008) In Lithos 102(3-4). p.435-459- Abstract
- The Ljusdal Batholith (LjB) is a major component of the central Svecofennian Domain in Sweden. It is separated from the Bothnian Basin to the north by the 1.82-1.80 Cia crustal-scale Hassela Shear Zone (HSZ). The LjB has emplacement ages of 1.86-1.84 Cia, is mainly alkali-calcic, metaluminous, has epsilon(Nd) values between -0.3 and + 1.2 and was formed in a magmatic arc setting. During the Svecokarelian orogeny the LjB was affected by at least three fold episodes. Large-scale folded screens of migmatised metasedimentary rocks occur in the eastern part of the batholith, and to the north of the HSZ, there is a 50 km wide diatexite belt. The Transition Belt (TrB), consisting of 1.88-1.85 Ga granitoids, is located at the northwestern... (More)
- The Ljusdal Batholith (LjB) is a major component of the central Svecofennian Domain in Sweden. It is separated from the Bothnian Basin to the north by the 1.82-1.80 Cia crustal-scale Hassela Shear Zone (HSZ). The LjB has emplacement ages of 1.86-1.84 Cia, is mainly alkali-calcic, metaluminous, has epsilon(Nd) values between -0.3 and + 1.2 and was formed in a magmatic arc setting. During the Svecokarelian orogeny the LjB was affected by at least three fold episodes. Large-scale folded screens of migmatised metasedimentary rocks occur in the eastern part of the batholith, and to the north of the HSZ, there is a 50 km wide diatexite belt. The Transition Belt (TrB), consisting of 1.88-1.85 Ga granitoids, is located at the northwestern extension of this belt. A calc-alkaline and peraluminous composition combined with negative epsilon(Nd) values (- 1.7 to -0.8) indicates a large proportion of metasediments in the source for these granitoids. U-Pb SIMS data on zircon rims from migmatites and leucogranites to the north and east of LjB yield ages of 1.87-1.86 Ga, i.e. coeval with the granitoids of the LjB and the TrB. There is thus a close relationship between the LjB, the TrB and the migmatites in both space and time. Syn-migmatitic shearing along the HSZ indicates that a proto-HSZ was initiated already at c. 1.86 Ga, and the location of the proto-HSZ is inferred to be controlled by two older nuclei present in the lower parts of the crust. As crustal-scale shear zone systems are known to act as ascent pathways for sheet-like flow in active orogenies the TrB may represents accumulations of melts that were attracted and extracted by the proto-HSZ and intruded in a block that was not pervasively affected by subsequent shear along the HSZ. An active continental margin setting for the LjB implies subduction at c. 1.86 Ga, and provides a heat source for both the migmatites and the TrB. A later migmatisation at 1.82 Ga has been recorded to the south of the HSZ. Within the LjB the 1.82 Ga stromatic migmatites are folded by F-2 folds, and the fabric is truncated by 1.80 Cia pegmatites. (Less)
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https://lup.lub.lu.se/record/1190602
- author
- Högdahl, Karin LU ; Sjöstrom, Håkan ; Andersson, Ulf B and Ahl, Martin
- organization
- publishing date
- 2008
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- migmatite, granitoid, Sm-Nd-Sr isotopes, geochemistry, Svecokarelian orogeny, U-PbSIMS and TIMS zircon geochronology
- in
- Lithos
- volume
- 102
- issue
- 3-4
- pages
- 435 - 459
- publisher
- Elsevier
- external identifiers
-
- wos:000256823100003
- scopus:42949126717
- ISSN
- 0024-4937
- DOI
- 10.1016/j.lithos.2007.07.019
- language
- English
- LU publication?
- yes
- id
- e4017642-92a7-445f-ba78-f30f32681138 (old id 1190602)
- date added to LUP
- 2016-04-01 12:12:03
- date last changed
- 2022-03-28 21:40:24
@article{e4017642-92a7-445f-ba78-f30f32681138,
abstract = {{The Ljusdal Batholith (LjB) is a major component of the central Svecofennian Domain in Sweden. It is separated from the Bothnian Basin to the north by the 1.82-1.80 Cia crustal-scale Hassela Shear Zone (HSZ). The LjB has emplacement ages of 1.86-1.84 Cia, is mainly alkali-calcic, metaluminous, has epsilon(Nd) values between -0.3 and + 1.2 and was formed in a magmatic arc setting. During the Svecokarelian orogeny the LjB was affected by at least three fold episodes. Large-scale folded screens of migmatised metasedimentary rocks occur in the eastern part of the batholith, and to the north of the HSZ, there is a 50 km wide diatexite belt. The Transition Belt (TrB), consisting of 1.88-1.85 Ga granitoids, is located at the northwestern extension of this belt. A calc-alkaline and peraluminous composition combined with negative epsilon(Nd) values (- 1.7 to -0.8) indicates a large proportion of metasediments in the source for these granitoids. U-Pb SIMS data on zircon rims from migmatites and leucogranites to the north and east of LjB yield ages of 1.87-1.86 Ga, i.e. coeval with the granitoids of the LjB and the TrB. There is thus a close relationship between the LjB, the TrB and the migmatites in both space and time. Syn-migmatitic shearing along the HSZ indicates that a proto-HSZ was initiated already at c. 1.86 Ga, and the location of the proto-HSZ is inferred to be controlled by two older nuclei present in the lower parts of the crust. As crustal-scale shear zone systems are known to act as ascent pathways for sheet-like flow in active orogenies the TrB may represents accumulations of melts that were attracted and extracted by the proto-HSZ and intruded in a block that was not pervasively affected by subsequent shear along the HSZ. An active continental margin setting for the LjB implies subduction at c. 1.86 Ga, and provides a heat source for both the migmatites and the TrB. A later migmatisation at 1.82 Ga has been recorded to the south of the HSZ. Within the LjB the 1.82 Ga stromatic migmatites are folded by F-2 folds, and the fabric is truncated by 1.80 Cia pegmatites.}},
author = {{Högdahl, Karin and Sjöstrom, Håkan and Andersson, Ulf B and Ahl, Martin}},
issn = {{0024-4937}},
keywords = {{migmatite; granitoid; Sm-Nd-Sr isotopes; geochemistry; Svecokarelian orogeny; U-PbSIMS and TIMS zircon geochronology}},
language = {{eng}},
number = {{3-4}},
pages = {{435--459}},
publisher = {{Elsevier}},
series = {{Lithos}},
title = {{Continental margin magmatism and migmatisation in the west-central Fennoscandian Shield}},
url = {{http://dx.doi.org/10.1016/j.lithos.2007.07.019}},
doi = {{10.1016/j.lithos.2007.07.019}},
volume = {{102}},
year = {{2008}},
}