Clark, Andrew David - Tectonometamorphic history of mid-crustal rocks at Aishihik Lake, southwest Yukon...

View the thesis

This thesis has been submitted to the Library for purposes of graduation, but needs to be audited for technical details related to publication in order to be approved for inclusion in the Library collection.
Term: 
Spring 2017
Degree: 
M.Sc.
Degree type: 
Thesis
Department: 
Department of Earth Sciences
Faculty: 
Science
Senior supervisor: 
Dan Gibson
Thesis title: 
Tectonometamorphic history of mid-crustal rocks at Aishihik Lake, southwest Yukon
Given Names: 
Andrew David
Surname: 
Clark
Abstract: 
Field mapping, petrography, thermodynamic modelling, and U-Pb (monazite and zircon) and 40Ar/39Ar geochronology reveal the tectonometamorphic history of polydeformed, amphibolite-facies rocks near Aishihik Lake, Yukon. Detrital zircon U-Pb ages suggest that these rocks are correlative to the Snowcap assemblage of the Yukon Tanana terrane. A penetrative regional foliation (S1) developed during the late Paleozoic, as S1 is cross-cut by a late Permian pluton. Permian plutons also exhibit less strain than Mississippian plutons near Aishihik Lake. The main foliation (S2) reflects west-verging, ductile shear (D2) during amphibolite facies metamorphism. Dating of Low-Y metamorphic monazite constrains the timing of D2 to 200-190 Ma. Peak T and P during D2 were 640-650 °C and ~7 kbar, respectively. High-Y monazite ages date regional decompression at ca. 188 Ma. 40Ar/39Ar thermochronology results indicate regional cooling through muscovite closure at ca. 175 Ma, whereas ca. 126 Ma biotite may reflect cooling following east-verging Jura-Cretaceous deformation (D3).
Keywords: 
Yukon-Tanana terrane; Monazite geochronology; Canadian Cordillera; Garnet isopleth thermobarometry; Petrochronology
Total pages: 
162