| In this dissertation I combine three detailed case studies of naturally deformed rocks with data and theories from the literature to improve our understanding of L tectonites. The case-study localities include: (1) granitic rocks, exposed in the Laramie Mountains (Wyoming), that experienced contractional deformation during continental assembly during Paleoproterozoic time; (2) mafic metavolcanic rocks and siliceous metasedimentary rocks, exposed in the Klamath Mountains (California), that were deformed during thrust faulting and accretion of oceanic rocks during Jurassic time; and (3) quartzite, granite, and schist, cut by a Tertiary shear zone that was fundamental in the tectonic exhumation of the Raft River Mountains metamorphic core complex (Utah). In the Laramie Mountains locality, L tectonites are localized in the hinge zone of a km-scale synform. The domain of L and L>S tectonites accommodates oblique extrusion of material parallel with the axis of folding between two relatively rigid crustal blocks. In the Klamath Mountains locality, zone-normal shortening and transport-parallel elongation enabled localization of constrictional strain in the apex of a convex-upward, lens-shaped, high-strain zone. Rheologic and metamorphic transitions did not affect the localization of constrictional strain in this area. In the Raft River Mountains locality zone-normal shortening and transport-parallel elongation coupled with a rheologic transition in rocks cut by a stretching fault at the base of the shear zone enabled strike-parallel flow into a domain of extreme transport-parallel extension. L>>S tectonites developed because rheology-driven strain-path partitioning localized the component of coaxial constrictional deformation.; Combining observations of numerical, theoretical, and analogue models that predict constrictional strain with case studies of natural high-strain zones indicate that there are three important factors that can lead to the development of L tectonites. These are: (1) the bulk kinematic framework, (2) local variations in external boundary conditions, and (3) internal variations in structural setting and rheology. My case studies and literature synthesis indicate that the bulk kinematic framework is the most important factor in developing L tectonites. However, in most cases, local variations in external boundary conditions, structural setting, and/or rheology are commonly required to form domains of L tectonites under bulk non-constrictional deformation conditions. |
