Collaborative Research: Testing Three-Dimensional Kinematic Analysis of Mid-Crustal Ductile Shear Zones: Deformation within the Western Idaho Shear Zone

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0001092 Tikoff0003007 McClellandTectonic models for orogenic belts rely on various kinematic indicators to determine such things as maximum and minimum stress directions, "stretching directions" and sense of shear. One fundamental assumption has been that tectonic transport directions parallel mineral or extension lineation directions, however three-dimensional numeric modeling of shear zones indicates that this is not always a valid assumption. This project will address this issue using the western Idaho shear zone that marks the accretion of allochthonous terranes to the west to the north American plate during the Late Cretaceous. The kinematic and geologic data have resulted in several, disparate models for this accretion. This study is an integrated structural, microstructural and U/Pb geochronologic project designed to determine the kinematic history of the late Cretaceous western Idaho shear zone that will employ three-dimensional techniques to test the validity of the assumption that tectonic transport is parallel to lineation. Results should help clarify the kinematics of this suture and evaluate one of the important kinematic assumptions used in interpretations of many orogens elsewhere.