UBC Theses and Dissertations

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UBC Theses and Dissertations

Timing and kinematics of the Duke River fault : insights into the evolution of the Insular Terrane, southwest Yukon Cobbett, Rose Natalie


The Duke River fault is a terrane-bounding structure that separates the Alexander terrane from Wrangellia in southwest Yukon. Detailed geological mapping and sampling of six key areas along the fault were completed in order to determine the history of movement on the fault. In these areas, the Duke River fault juxtaposes pervasively foliated and folded greenschist facies rocks of the Alexander terrane against low-grade, less deformed Wrangellian rocks. Multiple lines of evidence indicate the Alexander terrane has been thrust over Wrangellia. ⁴⁰Ar/³⁹Ar ages from muscovite grains, which are interpreted to have grown during faulting or have been reset by motions along the Duke River fault, range in age from 82-104 Ma, suggesting that movement along the fault is at least as old as Cretaceous. This mid-to Late Cretaceous event along the Duke River fault is overprinted by brittle deformation that affects rocks as young as Miocene to Pliocene in age and suggests that fault movement has occurred as recently as the Pliocene.

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