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.

This study documents the deformation history of the Santa Rita Flat pluton, eastern California, from the time of emplacement to post-emplacement transpressional shearing, and consists of manuscripts that make up three chapters. The first chapter addresses the emplacement of the Santa Rita Flat pluton using anisotropy of magnetic susceptibility (AMS). The second chapter describes the kinematic analysis of cross-cutting shear zones within the western margin of the pluton. The third chapter is an informal paper on the U/Pb dating of two sheared felsic dikes from the pluton. AMS of the Santa Rita Flat pluton indicates that the paramagnetic and ferromagnetic minerals define a foliation which is arched into an antiformal structure in the central to southern parts of the pluton. The northern part of the pluton displays an east-west striking magnetic foliation which lacks a fold-like geometry. Previously published field mapping and petrologic surveys of the pluton and surrounding wall rocks indicate that the southern margin and northern part of the Santa Rita Flat pluton represents the roof and core of the pluton, respectively. Integration of our analysis of the internal structure of the pluton with previously published work on the regional structure of the surrounding metasedimentary wall rocks, suggests that the pluton may have initially been intruded as a sill-like or "saddle reef" structure along a stratigraphically controlled mechanical discontinuity in the hinge zone of an enveloping regional-scale synform. Subsequent vertical inflation of this sill resulted in local upward doming of the overlying pluton roof and formation of the antiformal structure now observed at the current erosion level in the central-southern part of the pluton and overlying locally preserved roof rocks. No corresponding fold structure is indicated by AMS analysis in the northern part of the pluton, which is exposed at a deeper level, and represents a section closer to the pluton core. Emplacement of the Santa Rita Flat pluton at 164 Ma overlaps in time with regional deformation at ~185 - ~148 Ma (Middle - Late Jurassic) recognized in the southern Inyo Mountains. Northwest trending folds are pervasive along the western flank of the Inyo and White Mountains, and may have accommodated strains at the lateral tips of thrust faults which crop out in the southern Inyo Mountains. We speculate that space for initial emplacement of the Santa Rita Flat pluton may have been produced by layer-parallel slip and hinge-zone dilation, accompanied by axis-parallel slip during formation of a regional scale thrust-related synform. The Santa Rita shear system (SRSS) is composed of a series of discrete NW-SE striking steeply dipping shear zones that cut and plastically deform granitic rocks of the Santa Rita Flat pluton. The shear zones exhibit a domainal distribution of gently and steeply plunging stretching lineations, and are located at planar mechanical discontinuities between the granite and a series of felsic/mafic dikes which intrude the pluton. Mylonitized dikes within the shear zones contain syntectonic mineral assemblages not observed in dikes outside the shear zones, indicating that the dikes were intruded prior to shear zone development. Correlation with geometrically similar shear zones in the Sierra Nevada batholith to the west, suggests that the SRSS probably nucleated from a regional stress field in Cretaceous times (~90-78 Ma). Strain is heterogeneous within the shear zones, with local development of protomylonite, mylonite, ultramylonite and phyllonite. Strain heterogeneity within the granite is attributed to fluid infiltration and chemical reaction and alteration of feldspar to fine-grained mica. These deformation-induced mineral changes would have resulted in progressive mechanical weakening over time of rocks within the SRSS. The phyllonites occur predominantly within steeply lineated shear zones and contain mylonitized foliation-parallel quartz veins. The pattern of c-axis preferred orientation in these quartz veins indicates that deformation within the shear zones occurred under plane strain conditions. Locally, quartz veins also cut the foliation planes, reflecting high pore fluid pressures during evolution of the SRSS. These cross-cutting quartz veins are also plastically deformed, and their c-axis patterns indicate weak constrictional strains. The orientation of the shear zones, together with their strain paths, are used to develop a transpressional kinematic model for development of the SRSS within a progressively rotating stress field. / Master of Science