From ductile to brittle deformation: Structural development and strain distribution along a crustal-scale shear zone in SW Finland

Taija Torvela, Carl Ehlers

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

This study demonstrates the impact of variations in overall crustal rheology on crustal strength in relatively high P–T conditions at mid- to lower mid-crustal levels. In a crustal-scale shear zone, along-strike variations in the rheological competence result in large-scale deformation partitioning and differences in the deformation style and strain distribution. The structural behaviour of the crustal-scale Sottunga–Jurmo shear zone (SJSZ) in SW Finland is described. The shear zone represents a discontinuity between the amphibolite-to-granulite facies, dome-and-basin style crustal block to the north and the amphibolite facies rocks with dominantly steeply dipping structures to the south. The overall deformation style and resulting strains along the shear zone are greatly affected by the local lithology. The results of this study also have implications for the current tectonic models of the Palaeoproterozoic Fennoscandia. The most important implication is that the SJSZ, together with other structurally related shear zones, compartmentalised the far-field stresses, so that the late ductile structures within and south of the SJSZ can be allocated to a convergence from the south as late as ~1.79 Ga rather than to the Nordic orogeny from the west-northwest. It is further suggested that at ~1.79 Ga the stress regime was still compressive/transpressive and that the ~1.79 Ga magmatism in Åland at least initiated in a compressive setting. No extension or orogenic collapse, therefore, occurred in the Åland area while the rocks still were within the ductile regime.
Original languageEnglish
Pages (from-to)1133-1152
Number of pages20
JournalInternational Journal of Earth Sciences
Volume99
Issue number5
Early online date27 May 2009
DOIs
Publication statusPublished - Jul 2010

Fingerprint

brittle deformation
shear zone
granulite facies
amphibolite
distribution
rheology
amphibolite facies
orogeny
rock
stress field
dome
magmatism
discontinuity
lithology
partitioning
tectonics
basin

Keywords

  • shear zone
  • deformation
  • rheology
  • strain partitioning
  • Finland
  • Åland
  • palaeoproterozoic

Cite this

From ductile to brittle deformation : Structural development and strain distribution along a crustal-scale shear zone in SW Finland. / Torvela, Taija; Ehlers, Carl.

In: International Journal of Earth Sciences, Vol. 99, No. 5, 07.2010, p. 1133-1152.

Research output: Contribution to journalArticle

@article{f9676cc0f5ba47cbbbdbe786be759060,
title = "From ductile to brittle deformation: Structural development and strain distribution along a crustal-scale shear zone in SW Finland",
abstract = "This study demonstrates the impact of variations in overall crustal rheology on crustal strength in relatively high P–T conditions at mid- to lower mid-crustal levels. In a crustal-scale shear zone, along-strike variations in the rheological competence result in large-scale deformation partitioning and differences in the deformation style and strain distribution. The structural behaviour of the crustal-scale Sottunga–Jurmo shear zone (SJSZ) in SW Finland is described. The shear zone represents a discontinuity between the amphibolite-to-granulite facies, dome-and-basin style crustal block to the north and the amphibolite facies rocks with dominantly steeply dipping structures to the south. The overall deformation style and resulting strains along the shear zone are greatly affected by the local lithology. The results of this study also have implications for the current tectonic models of the Palaeoproterozoic Fennoscandia. The most important implication is that the SJSZ, together with other structurally related shear zones, compartmentalised the far-field stresses, so that the late ductile structures within and south of the SJSZ can be allocated to a convergence from the south as late as ~1.79 Ga rather than to the Nordic orogeny from the west-northwest. It is further suggested that at ~1.79 Ga the stress regime was still compressive/transpressive and that the ~1.79 Ga magmatism in {\AA}land at least initiated in a compressive setting. No extension or orogenic collapse, therefore, occurred in the {\AA}land area while the rocks still were within the ductile regime.",
keywords = "shear zone, deformation, rheology, strain partitioning, Finland, {\AA}land, palaeoproterozoic",
author = "Taija Torvela and Carl Ehlers",
year = "2010",
month = "7",
doi = "10.1007/s00531-009-0451-3",
language = "English",
volume = "99",
pages = "1133--1152",
journal = "International Journal of Earth Sciences",
issn = "1437-3254",
publisher = "Springer-Verlag",
number = "5",

}

TY - JOUR

T1 - From ductile to brittle deformation

T2 - Structural development and strain distribution along a crustal-scale shear zone in SW Finland

AU - Torvela, Taija

AU - Ehlers, Carl

PY - 2010/7

Y1 - 2010/7

N2 - This study demonstrates the impact of variations in overall crustal rheology on crustal strength in relatively high P–T conditions at mid- to lower mid-crustal levels. In a crustal-scale shear zone, along-strike variations in the rheological competence result in large-scale deformation partitioning and differences in the deformation style and strain distribution. The structural behaviour of the crustal-scale Sottunga–Jurmo shear zone (SJSZ) in SW Finland is described. The shear zone represents a discontinuity between the amphibolite-to-granulite facies, dome-and-basin style crustal block to the north and the amphibolite facies rocks with dominantly steeply dipping structures to the south. The overall deformation style and resulting strains along the shear zone are greatly affected by the local lithology. The results of this study also have implications for the current tectonic models of the Palaeoproterozoic Fennoscandia. The most important implication is that the SJSZ, together with other structurally related shear zones, compartmentalised the far-field stresses, so that the late ductile structures within and south of the SJSZ can be allocated to a convergence from the south as late as ~1.79 Ga rather than to the Nordic orogeny from the west-northwest. It is further suggested that at ~1.79 Ga the stress regime was still compressive/transpressive and that the ~1.79 Ga magmatism in Åland at least initiated in a compressive setting. No extension or orogenic collapse, therefore, occurred in the Åland area while the rocks still were within the ductile regime.

AB - This study demonstrates the impact of variations in overall crustal rheology on crustal strength in relatively high P–T conditions at mid- to lower mid-crustal levels. In a crustal-scale shear zone, along-strike variations in the rheological competence result in large-scale deformation partitioning and differences in the deformation style and strain distribution. The structural behaviour of the crustal-scale Sottunga–Jurmo shear zone (SJSZ) in SW Finland is described. The shear zone represents a discontinuity between the amphibolite-to-granulite facies, dome-and-basin style crustal block to the north and the amphibolite facies rocks with dominantly steeply dipping structures to the south. The overall deformation style and resulting strains along the shear zone are greatly affected by the local lithology. The results of this study also have implications for the current tectonic models of the Palaeoproterozoic Fennoscandia. The most important implication is that the SJSZ, together with other structurally related shear zones, compartmentalised the far-field stresses, so that the late ductile structures within and south of the SJSZ can be allocated to a convergence from the south as late as ~1.79 Ga rather than to the Nordic orogeny from the west-northwest. It is further suggested that at ~1.79 Ga the stress regime was still compressive/transpressive and that the ~1.79 Ga magmatism in Åland at least initiated in a compressive setting. No extension or orogenic collapse, therefore, occurred in the Åland area while the rocks still were within the ductile regime.

KW - shear zone

KW - deformation

KW - rheology

KW - strain partitioning

KW - Finland

KW - Åland

KW - palaeoproterozoic

U2 - 10.1007/s00531-009-0451-3

DO - 10.1007/s00531-009-0451-3

M3 - Article

VL - 99

SP - 1133

EP - 1152

JO - International Journal of Earth Sciences

JF - International Journal of Earth Sciences

SN - 1437-3254

IS - 5

ER -