The central White-Inyo Range in eastern California is a deformed section of Neoproterozoic through Cambrian sedimentary rocks which has been intruded by granitic plutons associated with the Mesozoic Sierra Nevada intrusive suites to the west. My dissertation involves a characterization of the pre-plutonic regional deformation within the central White-Inyo Range and an understanding of the deformation of the wall rocks and magmas associated with pluton emplacement. The four chapters in this dissertation are a compilation of three published articles (two in journals, one in a field guide-book) and one manuscript.
The regional deformation was characterized by measuring the orientation of folds, bedding, and cleavage throughout the range, as well as utilizing these data from other authors and from published geologic maps. Synthesis of the data indicate that all regional structures pre-date the intrusions. The transition from regional structures to aureole structures reveals components of horizontal and vertical translation and rotation of bedding associated with forceful emplacement.
The Jurassic Eureka Valley-Joshua Flat-Beer Creek (EJB) composite pluton and Cretaceous Papoose Flat pluton, as well as the deformed metasedimentary rocks surrounding these plutons, have been examined in detail. Penetrative shortening of the wall rocks was studied in detail along three traverses across the aureole of the EJB pluton and from specific outcrops throughout the aureole. Sedimentary formations have been attenuated to approximately one third of their regional stratigraphic thicknesses. Strain is characterized by flattening and plane strain. Deformation mechanisms vary, but are dominated by intracrystalline slip and climb and by grain boundary sliding. Contact metamorphism is characterized by andalusite followed by sillimanite.
The internal fabric of the EJB pluton has been analyzed through the study of the anisotropy of magnetic susceptibility (AMS). Samples were collected at 210 locations ( 420 drill cores, approximately 1000 samples) throughout the pluton. Maps of the fabric and magnetic parameters reveal that magnetic fabrics cross-cut some compositional boundaries and parallel others. Comparison between the magnetic fabrics and the aureole structures indicate that the magma and surrounding plastic aureole deformed as a single unit during emplacement.
Detailed porphyroblast-matrix analysis within the concordant metasedimentary aureole rocks surrounding the Papoose Flat pluton indicates that inclusion trails within porphyroblasts can be used as strain markers to restore the aureole rocks to their prepluton emplacement position. The kinematics of rotation, the change in thickness and volume, and the amount of translation of the metasedimentary formations within the aureole have been determined using porphyroblast-matrix relationships, in combination with measurement of stratigraphic sections and whole-rock geochemical analyses.
The emplacement of the EJB and Papoose Flat plutons is modeled as occurring in two stages. The first stage is sill-like, producing a thermal aureole which lowers the viscosity of the surrounding sedimentary rocks. The second stage is forceful, causing upward and outward translation and rotation of the surrounding aureole. Porphyroblastmatrix relationships from the EJB and Papoose Flat pluton, and from the literature on the Ardara pluton, Ireland, and the Cannibal Creek pluton, Australia, support this two stage emplacement model for concordant plutons. / Ph. D.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/39677 |
| Date | 05 October 2007 |
| Creators | Morgan, Sven Soren |
| Contributors | Geology, Law, Richard D., Glazner, Allen, Tracy, Robert J., Sylvester, Arthur G., Sinha, Krishna |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation, Text |
| Format | viii, 172 leaves, BTD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 41994211, LD5655.V856_1998.M674.pdf |
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