On I-10 between Tuscon, AZ, and Phoenix, AZ, is the Picacho Mountains Metamorphic Core Complex (MCC). The Picacho Mountains MCC represents the northwest of the Greater Catalina MCC which includes Tortolita, Santa Catalina, and Rincon Mountains. To the immediate south of I-10 is Picacho Peak, an early Miocene andesitic volcanic center, and opposite of Picacho Peak are the granitic Picacho Mountains. The detachment shear zone (DSZ) is well exposed at Hill 2437. The mylonitic DSZ is separated into an upper, middle, and lower plate by two detachment faults.
The DSZ is estimated to have undergone deformation at ~500 °C based on recrystallized quartz microstructures and a previous thermochronologic study by previous graduate student Maxwell Schaper. We obtained an average flow stress of 43 ± 9 MPa using a quartz paleopiezometer by Stipp and Tullis (2003). Using a flow law by Hirth et al. (2001), we found strain rate values between 10–13 and 10–12 s–1. Grain size analysis indicates that quartz recrystallized grains have relatively moderate aspect ratio (1.55 < Rf < 1.87) which correlates to small amount of finite strain (1.13 < Rs < 1.33). Results from vorticity analysis based on the recrystallized quartz grain shape foliation method reveals that quartz was deformed under ~60% pure shear and ~40% simple shear (0.48 < Wm < 0.70, assuming plane strain), and the DSZ experienced ~18% of shortening perpendicular to mylonitic foliation, and up to ~22% of stretching parallel to the flow plane up. We found that despite high strain rate values and evidence of high strain rate (e.g. undulose extinction in quartz, chessboard structures, cataclasites, and possible pseudotachylytes), this is not reflected in the amount of finite strain recorded by the mylonitic DSZ.
|Commitee:||Morra, Gabriele, Willis, James J.|
|School:||University of Louisiana at Lafayette|
|School Location:||United States -- Louisiana|
|Source:||MAI 58/05M(E), Masters Abstracts International|
|Keywords:||Detachment shear zone, Metamorphic core complex, Picacho Mountains, Recrystallized quartz paleopiezometry, Strain, Stress|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be