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147
Kohlstedt, D. L., B. Evans, and S. J. Mackwell (1995), Strength of the lithosphere:
Constraints imposed by laboratory experiments, Journal of Geophysical
Research, 100(B9), 17,587–17,602.
Kranidiotis, P., and W. H. MacLean (1987), Systematics of chlorite alteration at the
Phelps Dodge massive sulfide deposit, Matagami, Quebec, Economic Geology
and the Bulletin of the Society of Economic Geologists, 82(7), 1,898–1,911.
Lee, D. E., and L. B. Fischer (1985), Cretaceous metamorphism in the northern Snake
Range, Nevada, a metamorphic core complex, Isochron West, 42, 3–7.
Lee, J., E. L. Miller, and J. F. Sutter (1987), Ductile strain and metamorphism in an
extensional tectonic setting: a case study from the northern Snake Range,
Nevada, USA, in Continental extensional tectonics, edited by M. P. Coward,
J. F. Dewey and P. L. Hancock, pp. 267–298, Geological Society Special
Publication.
Lee, J., and J. F. Sutter (1991), Incremental 40Ar/39Ar thermochronology of mylonitic
rocks from the northern Snake Range, Nevada, Tectonics, 10, 77–100.
Lee, J. (1995), Rapid uplift and rotation of mylonitic rocks from beneath a detachment
fault; insights from potassium feldspar 40Ar/39Ar thermochronology, northern
Snake Range, Nevada, Tectonics, 14(1), 54–77.
Lee, J., P. B. Gans, and E. L. Miller (1999a), Geologic map of the Third Butte East
Quadrangle, Nevada, Field Studies Map 16, Nevada Bureau of Mines and
Geology, Reno, NV.
Lee, J., P. B. Gans, and E. L. Miller (1999b), Geologic map of the Mormon Jack Pass
Quadrangle, Nevada, Field Studies Map 17, Nevada Bureau of Mines and
Geology, Reno, NV.
Lee, J., E. L. Miller, P. B. Gans, and C. C. Huggins (1999c), Geologic map of the
Mount Moriah Quadrangle, Nevada, Field Studies Map 19, Nevada Bureau of
Mines and Geology, Reno, NV.
Leoni, L., F. Sartori, and M. Tamponi (1998), Composition variation in K-white micas
and chlorites coexisting in Al- saturated metapelites under late diagenetic to low-grade
metamorphic conditions (Internal Liguride Units, Northern Apennines,
Italy), European Journal of Mineralogy, 10(6), 1,321–1,339.
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 162 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 147 Kohlstedt, D. L., B. Evans, and S. J. Mackwell (1995), Strength of the lithosphere: Constraints imposed by laboratory experiments, Journal of Geophysical Research, 100(B9), 17,587–17,602. Kranidiotis, P., and W. H. MacLean (1987), Systematics of chlorite alteration at the Phelps Dodge massive sulfide deposit, Matagami, Quebec, Economic Geology and the Bulletin of the Society of Economic Geologists, 82(7), 1,898–1,911. Lee, D. E., and L. B. Fischer (1985), Cretaceous metamorphism in the northern Snake Range, Nevada, a metamorphic core complex, Isochron West, 42, 3–7. Lee, J., E. L. Miller, and J. F. Sutter (1987), Ductile strain and metamorphism in an extensional tectonic setting: a case study from the northern Snake Range, Nevada, USA, in Continental extensional tectonics, edited by M. P. Coward, J. F. Dewey and P. L. Hancock, pp. 267–298, Geological Society Special Publication. Lee, J., and J. F. Sutter (1991), Incremental 40Ar/39Ar thermochronology of mylonitic rocks from the northern Snake Range, Nevada, Tectonics, 10, 77–100. Lee, J. (1995), Rapid uplift and rotation of mylonitic rocks from beneath a detachment fault; insights from potassium feldspar 40Ar/39Ar thermochronology, northern Snake Range, Nevada, Tectonics, 14(1), 54–77. Lee, J., P. B. Gans, and E. L. Miller (1999a), Geologic map of the Third Butte East Quadrangle, Nevada, Field Studies Map 16, Nevada Bureau of Mines and Geology, Reno, NV. Lee, J., P. B. Gans, and E. L. Miller (1999b), Geologic map of the Mormon Jack Pass Quadrangle, Nevada, Field Studies Map 17, Nevada Bureau of Mines and Geology, Reno, NV. Lee, J., E. L. Miller, P. B. Gans, and C. C. Huggins (1999c), Geologic map of the Mount Moriah Quadrangle, Nevada, Field Studies Map 19, Nevada Bureau of Mines and Geology, Reno, NV. Leoni, L., F. Sartori, and M. Tamponi (1998), Composition variation in K-white micas and chlorites coexisting in Al- saturated metapelites under late diagenetic to low-grade metamorphic conditions (Internal Liguride Units, Northern Apennines, Italy), European Journal of Mineralogy, 10(6), 1,321–1,339. |
