The Coastal Batholith of central Chile preserves structures that record the concentration, migration, transportation, and emplacement of magma during the progressive construction of a sheeted dike complex. This sheeted dike complex is divided into three main structural-geographic domains. The northwestern domain contains an abundance of deformed microgranitoid enclaves that host features that facilitated the concentration of melt during crystallization. The formation of interconnected dilational sites produced an array of lecocratic zones that may have formed larger dike networks that facilitated the transportation of melt-rich magma producing new magmatic units of similar mineralogy. The central domain is characterized by the presence of two tonalitic units that contain enclave swarms distinguished by their general packing arrangement and degree of elongation. Di erences in the fabric architecture of these enclave swarms are displayed by two separate three-dimensional fabric analyses using the Rf/ method, which indicates an abrupt transition from low-distortion oblate fabrics to more distorted prolate geometries. These changes are compared to the statistical alignment of feldspar phenocrysts that indicate general attening in both units with a higher degree of alignment within the XZ fabric plane for the younger tonalite. The third (southeastern) domain is distinguished by meter-scale, compositionally and texturally diverse sheeted dikes intercalated with biotite-rich migmatite screens of the host gneiss along the pluton margin. The need to process large quantities of fabric data from central Chile presented the opportunity to establish a comprehensive method for the quanti cation of three-dimensional rock fabrics following the Rf/ and Fry methods. In order to test the utility of this procedure, a three-dimensional synthetic model of known strain shape, magnitude, and orientation was processed. The results of this assessment indicate that the procedure accurately calculated the expected state of strain within a small margin of error. Finally, a natural example is presented to test the method's ability to quantify the fabrics of deformed rocks. This example is a \lineation much greater than foliation" (L>>S) metagranite augen gneiss from the Coastal Batholith of central Chile. This analysis resulted in calculated fabric ellipsoids from both the Rf/ and Fry methods that clearly display signi cantly prolate geometries at moderate distortions. The development of the three-dimensional rock fabric quanti cation procedure highlighted the need to teach analytical strain techniques in three-dimensions. To allow for this application, an interactive R script (FRY3D) was created speci cally to aid in the instruction and visualization of three-dimensional strain calculation at the advanced undergraduate and graduate levels. This tutorial was presented to a structural geology course of 20 students at the undergraduate level with a two part semi-quantitative concept assessment before and after the presentation. The results of this assessment indicate a positive increase in student's understanding of three-dimensional nite strain. Finally, a simple examination of analytical error associated with the Panozzo projection technique for strain analysis is presented and indicates relationships among population size, strain magnitude, and initial fabric. My results suggest that this method is most robust when applied to sections containing greater than approximately 125 lines. Moreover, the magnitude-dependent error indicates that the method may be better suited for rocks deformed at low to moderate strains. I recommend an adaption to the initial conditional assumptions for this method that lines exhibit an initial radial symmetry when recentered to a common point.

Partitioning of finite strains in different domains within the limb and hinge regions of a fold can be used to understand the deformation processes operative during fold formation. Samples taken from the limb and hinge regions of a gently plunging, asymmetric, tight, mesoscale fold in the Erwin formation of the Blue Ridge in North Carolina were analyzed to determine the deformation mechanisms and strains associated with the folding event. Rf/phi grain shape fabric analysis was conducted for each sample and used to calculate the orientation and magnitude of the final grain shape fabric ellipsoids. Flexural folding and passive-shear folding models predict that the highest finite strains will be recorded in the hinge of a fold. The highest grain shape magnitudes recorded in the North Carolina fold, however, lie along the overturned fold limb. The final geometry of many folds indicates that hinge plane migration processes are active during compressive deformation events. Numeric, conceptual, and analogue based studies have demonstrated the migration of fold hinges during deformation. However, documentation of these processes in field based studies is rare and limited to techniques that are frequently site specific. Methods proven successful in natural studies include the analysis of superposed folding; the migration of earlier hinge-related features such as fractures, cleavage planes, and boudinaged bedding planes; and the kinematic analysis of syntectonic pressure shadows. The magnitude and orientation of the grain shape ellipsoids calculated for the North Carolina fold indicate that rocks in the overturned limb were once located in the hinge of the fold. Subsequent noncoaxial deformation processes operative during folding resulted in the migration of the hinge to its present orientation and position. This relationship indicates that it is possible to use strain/shape fabric analysis as a test for hinge migration in folds, and that this technique may be more generally applicable in natural settings than previously proposed tests. / Master of Science