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Structural divergence and transpression in the Teslin tectonic zone, southern Yukon Territory
Author(s) -
Stevens Robert A.,
Erdmer Philippe
Publication year - 1996
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/96tc01134
Subject(s) - geology , transpression , shear zone , terrane , greenschist , paleontology , lineation , craton , seismology , subduction , tectonics , geochemistry
The structural and tectonic evolution of the Teslin tectonic zone, a complex belt of ductilely deformed rocks forming the southern extension of the Yukon‐Tanana terrane in the northern Canadian Cordillera, is elucidated with new field data and by the reinterpretation of existing data. The zone includes greenschist to amphibolite facies metasedimentary and metaplutonic rocks of the Nisutlin and Anvil assemblages characterized by S and L ‐ S tectonite fabrics. Primary contact relationships and ages show that most rocks in the zone were contiguous by Mississippian time. Mapping identified a number of strain domains which preserve S fabrics dipping northeasterly or southwesterly, variable mineral lineation orientations, and a variety of shear directions including easterly and westerly vergent thrust shear, down‐to‐the‐east and down‐to‐the‐west normal shear, and dextral strike‐slip shear. Regional constraints and microstructures suggest that latest ductile deformation was Late Triassic to Early Jurassic in age. Structural characteristics are explained most effectively by convergent‐dominated transpression in combination with tectonic wedging and associated back thrusting above a low‐angle west dipping detachment. Oblique eastward and upward movement of the rocks over the detachment, which may have coincided with the top of thinned North American continental crust, produced easterly vergent shear, and localized or widespread tectonic wedging and back thrusting produced westerly vergent shear. The transpressive deformation postdates formation of the Nisutlin assemblage by Mississippian time and subduction of the Slide Mountain Ocean beneath the Nisutlin assemblage in Permian to Early Triassic time. The western margin of the Teslin tectonic zone was truncated by Cretaceous strike‐slip faults and translated northward. Rocks of the peraluminous orthogneiss assemblage of the Yukon‐Tanana terrane in central Yukon acted as the tectonic wedge and were overthrust by rocks of the Nisutlin and Anvil assemblages in Early Jurassic time before unroofing by local extension in Cretaceous time.