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Ductile shear zones related to crustal shortening and domain boundary evolution in the central Fennoscandian Shield
Author(s) -
Högdahl Karin,
Sjöström Håkan,
Bergman Stefan
Publication year - 2009
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/2008tc002277
Subject(s) - geology , sinistral and dextral , shear zone , terrane , shear (geology) , crust , gneiss , shield , tectonics , baltic shield , geochronology , seismology , transpression , indian shield , metamorphic rock , geophysics , petrology , paleontology , craton
The Paleoproterozoic part of the Fennoscandian Shield is composed of crustal components formed in different tectonic settings and generally separated by well‐defined shear zone systems. An anomalous transitional boundary has been investigated by integrating structural analysis and geochronology with published geophysical data. The nature of this boundary is interpreted to be a consequence of an apparent stacking in the lower and middle crust initiating 1.87–1.86 Ga dextral shear along the Gävle‐Rättvik Zone (GRZ) and adjacent shear zones, resulting in an arcuate northern boundary of the Bergslagen province. This boundary coincides with geophysical anomalies and temporal and metamorphic breaks. Owing to continuous convergence the pure‐shear overprint component increased on the GRZ and caused a shift of dextral shear to the Hagsta Gneiss Zone with recorded shear at 1809 ± 2 Ma. Most likely, both these structures are related to coeval shear zones farther to the east as a part of an ∼1500 km long crustal, or possibly terrane, boundary.