Kinematic analysis and field mapping of the Homestake shear zone (HSZ) and Slide Lake shear zone (SLSZ) in central Colorado provide new evidence for strain partitioning in the mid-crust at ~1.4 Ga. The northeast-striking, steeply dipping HSZ comprises a ~10-km-wide set of anastomosing ductile shear zones and pseudotachylyte-bearing faults. Approximately 3-km south of the HSZ, the north-northeast-striking, shallowly dipping mylonites of the SLSZ form three 1-10-m-thick shear zone splays. Both top-up-to-the-northwest and top-down-to-the-southeast shear sense are recorded in the SLSZ and HSZ. Oblique stretching lineations in both shear zones show vertical (top-down-to-the-southeast and top-up-to-the-northwest) and dextral movement occurred during mylonite development. Quartz and feldspar deformation mechanisms and quartz [c] axis lattice preferred orientation (LPO) patterns are consistent with deformation temperatures ranging from ~280-500°C in the HSZ to ~280-600°C in the SLSZ. Mean kinematic vorticity and quartz [c] axis LPOs for parts of each shear zone suggest plane and non-plane strain general shear with contributions of 47-69% pure shear and 31-53% simple shear. Based on micro- and mesoscale kinematics along with mean kinematic vorticity values and deformation temperature estimates, we propose that HSZ and SLSZ formed during strain localization and partitioning within a mid-crustal transpressional shear zone system that involved subvertical shuffling at ~1.4 Ga.
| Identifer | oai:union.ndltd.org:UTENN/oai:trace.tennessee.edu:utk_gradthes-1962 |
| Date | 01 May 2011 |
| Creators | Lee, Patricia Elizabeth |
| Publisher | Trace: Tennessee Research and Creative Exchange |
| Source Sets | University of Tennessee Libraries |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Masters Theses |
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