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142
Buck, W. R. (1988), Flexural rotation of normal faults, Tectonics, 7(5), 959–973.
Cathelineau, M., and D. Nieva (1985), A chlorite solid solution geothermometer; the
Los Azufres (Mexico) geothermal system, Contributions to Mineralogy and
Petrology, 91(3), 235–244.
Cathelineau, M., and G. Izquierdo (1988), Temperature–composition relationships
of authigenic micaceous minerals in the Los Azufres geothermal system,
Contributions to Mineralogy and Petrology, 100(4), 418–428.
Coney, P. J. (1974), Structural Analysis of the Snake Range ‘Decollement,’ East-Central
Nevada, Geological Society of America Bulletin, 85(6), 973–978.
Coney, P. J. (1980), Cordilleran metamorphic core complexes; an overview, Cordilleran
metamorphic core complexes, no. 153(153), 7–31.
Connolly, J. A. D. (2005), Computation of phase equilibria by linear programming; a tool
for geodynamic modeling and its application to subduction zone decarbonation,
Earth and Planetary Science Letters, 236(1–2), 524–541.
Cooper, F. J., J. P. Platt, R. Anczkiewicz, and M. J. Whitehouse (in preparation),
Footwall dip of a core complex detachment fault: thermobarometric constraints
from the northern Snake Range (Basin and Range, USA).
Cooper, F. J., J. P. Platt, E. S. Platzman, M. J. Grove, B. R. Hacker, and G. Seward (in
review), Opposing shear senses in a sub-detachment mylonite zone: implications
for core complex mechanics, Tectonics, doi: 10.1029/2008TC002350.
Cosca, M. A., J. C. Hunziker, S. Huon, and H. Masson (1992), Radiometric age
constraints on mineral growth, metamorphism and tectonism of the Gummfluh
Klippe, Brianconnais domain of the Prealpes, Switzerland, Contributions to
Mineralogy and Petrology, 112(4), 439–449.
Dalmasso, J., G. Barci-Funel, and G. J. Ardison (1992), Reinvestigation of the decay
of the long-lived odd-odd 176Lu nucleus, Applied Radiation and Isotopes, 43,
69–76.
Davis, G. A. (1988), Rapid upward transport of mid-crustal mylonitic gneisses in the
footwall of a Miocene detachment fault, Whipple Mountains, southeastern
California, Geologische Rundschau, 77, 191–209.
Object Description
| Title | Structural and thermobarometric constraints on the exhumation of the northern Snake Range metamorphic core complex, Nevada |
| Author | Cooper, Frances Jacqueline |
| Author email | fcooper@usc.edu; fcooper@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Geological Sciences |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2008-08-27 |
| Date submitted | 2008 |
| Restricted until | Unrestricted |
| Date published | 2008-10-22 |
| Advisor (committee chair) | Platt, John P. |
| Advisor (committee member) |
Davis, Gregory A. Morrison, Jean Platzman, Ellen Thompson, Mark E. |
| Abstract | Observations from areas of large-scale continental extension, including the Basin and Range Province in western North America, have revealed the presence of regionally subhorizontal normal faults that appear to have exhumed rocks from mid- to lower-crustal levels. These detachment faults separate upper plate rocks extended on arrays of high-angle brittle normal faults from lower plate rocks exhibiting ductile mylonitic stretching and medium- to high-grade metamorphism. The origin and evolution of these detachments has been a matter of debate for decades, and yet a number of issues remain unresolved: (1) the dip of the faults when they were initiated and were active; (2) their penetration depth into the crust; (3) their role in exhuming high-grade metamorphic rocks; and (4) the origin and significance of the mylonitic deformation in their footwalls.; I explored these issues in the footwall to a classic detachment fault -- the northern Snake Range décollement (NSRD) in eastern Nevada -- using a combination of structural geology, geothermobarometry, paleomagnetism, isotope geochronology, and electron backscatter diffraction (EBSD) analysis. Garnet-biotite-muscovite-plagioclase thermobarometry suggests that the footwall to the NSRD experienced late Cretaceous peak metamorphic conditions of 6–8 kbar and 500–650°C, equivalent to a burial depth of ≤ 30 km. Calcite-dolomite thermometry indicates that Tertiary mylonitic deformation occurred under lower temperature conditions of 350–430°C, equivalent to mid-crustal levels. Structural, paleomagnetic, and EBSD data demonstrate that mylonites experienced two phases of shear (top-east and top-west), inconsistent with movement along a single throughgoing normal fault.; I conclude that exhumation of the northern Snake Range footwall was a two-step process. Initial ductile stretching and thinning of the crust exhumed footwall rocks to the middle crust beneath a discontinuity, referred to as the localized-distributed transition (LDT), that separated extension along brittle normal faults above from localized ductile shear zones below. Mylonites formed along the LDT were subsequently captured by a moderately-dipping NSRD that soled into the middle crust. The NSRD, therefore, appears to be a late-stage brittle normal fault that was responsible for only about half the total exhumation of the footwall, and is not directly related to the mylonitic deformation. |
| Keyword | continental extension; extensional tectonics; Basin and Range province; Cordillera; metamorphism; mylonite zone |
| Geographic subject | tectonic features: Snake Range décollement |
| Geographic subject (state) | Nevada |
| Geographic subject (country) | USA |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m1695 |
| Contributing entity | University of Southern California |
| Rights | Cooper, Frances Jacqueline |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-Cooper-2458 |
| Archival file | uscthesesreloadpub_Volume40/etd-Cooper-2458.pdf |
Description
| Title | Page 157 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 142 Buck, W. R. (1988), Flexural rotation of normal faults, Tectonics, 7(5), 959–973. Cathelineau, M., and D. Nieva (1985), A chlorite solid solution geothermometer; the Los Azufres (Mexico) geothermal system, Contributions to Mineralogy and Petrology, 91(3), 235–244. Cathelineau, M., and G. Izquierdo (1988), Temperature–composition relationships of authigenic micaceous minerals in the Los Azufres geothermal system, Contributions to Mineralogy and Petrology, 100(4), 418–428. Coney, P. J. (1974), Structural Analysis of the Snake Range ‘Decollement,’ East-Central Nevada, Geological Society of America Bulletin, 85(6), 973–978. Coney, P. J. (1980), Cordilleran metamorphic core complexes; an overview, Cordilleran metamorphic core complexes, no. 153(153), 7–31. Connolly, J. A. D. (2005), Computation of phase equilibria by linear programming; a tool for geodynamic modeling and its application to subduction zone decarbonation, Earth and Planetary Science Letters, 236(1–2), 524–541. Cooper, F. J., J. P. Platt, R. Anczkiewicz, and M. J. Whitehouse (in preparation), Footwall dip of a core complex detachment fault: thermobarometric constraints from the northern Snake Range (Basin and Range, USA). Cooper, F. J., J. P. Platt, E. S. Platzman, M. J. Grove, B. R. Hacker, and G. Seward (in review), Opposing shear senses in a sub-detachment mylonite zone: implications for core complex mechanics, Tectonics, doi: 10.1029/2008TC002350. Cosca, M. A., J. C. Hunziker, S. Huon, and H. Masson (1992), Radiometric age constraints on mineral growth, metamorphism and tectonism of the Gummfluh Klippe, Brianconnais domain of the Prealpes, Switzerland, Contributions to Mineralogy and Petrology, 112(4), 439–449. Dalmasso, J., G. Barci-Funel, and G. J. Ardison (1992), Reinvestigation of the decay of the long-lived odd-odd 176Lu nucleus, Applied Radiation and Isotopes, 43, 69–76. Davis, G. A. (1988), Rapid upward transport of mid-crustal mylonitic gneisses in the footwall of a Miocene detachment fault, Whipple Mountains, southeastern California, Geologische Rundschau, 77, 191–209. |
