Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains viii, 83 p. : ill. (some col.), maps (part col.). Vita. Includes abstract. Includes bibliographical references (p. 74-78).

Thesis (doctoral)--Freie Universität Berlin, 2005. / "April 2006"--P. [2] of cover. Vita. DVD in pocket contains supplementary data. Includes bibliographical references (p. 115-127). Text is also available via the World Wide Web.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (p. 131-141).

Ph.D.

No description available.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN. / Vita. / Bibliography: leaves 164-168. / by Teng-Fong Wong. / Ph.D.

Shear zones which deform margins of amphibolite boudins in the Cheyenne Belt, SE Wyoming, record a full strain transition from relatively undeformed amphibolite which has relict igneous textures to mylonitic amphibolite with a strongly developed L-S tectonic fabric. The strain transition is marked by the rotation of amphibole and plagioclase aggregates into parallelism with the shear zone boundary and progressive grain size reduction. These observations indicate that strain magnitude increases across the shear zone. Detailed petrologic and microstructural analysis of a single amphibolite shear zone has been conducted in order to: 1) document the petrologic and microstructural evolution of the shear zone and 2) investigate the interrelationships between mechanical and chemical processes associated with shear zone formation. Amphibolites throughout the shear zone consist of amphibole + plagioclase with only minor amounts of quartz + chlorite + epidote + sphene + ilmenite. Within the relatively undeformed amphibolite, amphibole and, to a lesser extent, plagioclase has wide compositional variation. Amphibole compositions vary from actinolitic hornblende to magnesio-hornblende which involves increases in Al, Fe, Na and K contents and decreases in Si and Mg. Plagioclase compositions vary from Angp in cores of plagioclase grains to Anjo within grain boundary domains. With increasing strain magnitude across the shear zone variation of amphibole composition decreases and become predominantly magnesio-hornblende. Plagioclase compositions also decrease in range although grain boundary domains still have higher albite content. The observed variation of amphibole compositions indicate that shear zone formation occurred during prograde metamorphism although compositional changes may also be a function of changing grain boundary fluid composition. These petrologic data indicate that shear zone metamorphism was in part controlled by the magnitude of strain during deformation. Scanning electron microscope back-scattered images and color enhanced X-ray compositional maps indicate that compositional variation in plagioclase and amphibole occurs along margins of highly angular grains of various sizes. These textural observations have been interpreted to indicate that chemical reactions occurred by a dissolution and reprecipitation processes following or during cataclastic deformation. Transmission electron microscope (TEM) images show local zones of high dislocation density adjacent to microcracks suggesting that work hardening may have been an important processes during cataclasis. Alternatively, microcracks may have acted as source for development of dislocations. The importance of deformation in assisting shear zone chemical processes is evidenced by: 1) the observation of new mineral overgrowth along grain boundaries and 2) TEM images of amphibole which show that actinolitic hornblende has a high defect density whereas magnesio-hornblende overgrowths are relatively defect free. This observation suggests that strain energy associated with dislocations may have contributed to the chemical process. Thermodynamic modelling of reaction progress within the shear zone using the Gibbs Method indicates that observed modal and compositional changes can occur isothermally if strain energy is added to the system. Increases in reaction progress with deformation may have also been due to increases in fluid infiltration or diffusion due to grain size reduction. The general conclusion of this study is that in order to apply petrologic, geochemical and isotopic data to understanding geochemical and tectonic processes, microstructural information on the magnitude of strain and the type of deformation mechanism must be evaluated, quantitatively if possible. / Ph. D.

The Pine Mountain window of Georgia and Alabama hosts the southernmost exposed Grenville aged basement terrane in the Appalachians. The window Is bounded on the east by the Box Ankle thrust fault which juxtaposes basement lithologies from hanging wall paragneiss, schist, and metavolcanic rocks of the Piedmont terrane. The Ocmulgee strike-slip fault separates Piedmont Terrane rocks from Avalon Terrane lithologies to the south and east of the Pine Mountain window. U-Pb ages of zircons constrain the timing of deformation along the Box Ankle and Ocmulgee faults at 304 ± 144 and 335 ± 7 Ma respectively. A contrast in zircon response to high grade deformation from both fault zones is observed. The response of zircon U-Pb systematics in these fault zones provides data on the effects of Pb loss versus U gain models, dissolution processes, and overgrowth binary mixing models from within selected mylonitized bulk rock chemistries. In the Ocmulgee fault, zircon overgrowth associated with deformation dominates U/Pb age discordancy. Isotopic re-equilibration of Sr Isotopes did not occur on a cm whole rock scale during deformation. Porphyroclasts In the Ocmulgee shear zone retained partial Sr Isotopic signatures of the shear zone protolith. In contrast, Rb-Sr Isotope systems In the Box Ankle fault were re-equilibrated during ductile deformation. Zircons from the Box Ankle fault show evidence of dissolution with no apparent overgrowth. A regional tectonic model proposed from ages obtained in this study Include transpression and doming of the basement and Piedmont cover as seen In the Box Ankle fault trace. Dextral strike-slip with right stepover displacement between the Ocmulgee-Goat Rock fault system and the Towaliga system provide a transpressional environment at the eastern end of the Pine Mountain window. / Master of Science

Sedimentary units in the Inyo Mountains of eastern California can be traced into the aureole of the Papoose Flat pluton where, due to intense crystal-plastic deformation, they are thinned to less than 10% of their original stratigraphic thickness. This deformation is constrained by textural relationships to have occurred during contact metamorphism. The strain within the dominantly S>L tectonites is partitioned by lithology. The deformation is in bulk, noncoaxial, but examination of individual lithologic units reveals large components of either pure shear or simple shear deformation. C-axis fabric analysis of quartz tectonites within veins in the gneissic border of the pluton, and quartzites within the pluton aureole, indicate that quartz tectonites deformed under approximately simple shear deformation, and suggest that the pluton/wall rock contact is the zone of highest strain. C-axis fabrics measured from the quartz tectonites are distinctly different between the veins and the quartzites. Veins display a higher maximum concentration of c-axes per uniform distribution and fabrics are characterized by single girdles. Quartzites display decreasing maximum concentrations of c-axes with increasing distance from the pluton/wall rock contact and fabrics are characterized by asymmetric cross girdles. Structural and field relationships indicate that; 1) pure shear deformation was dominant within the deformed border of the pluton, 2) flattening (chocolate tablet boudinage) occurred locally at the pluton/wall rock contact, 3) dominantly pure shear deformation produced the porphyroblast-matrix relationships within the aureole schists and, 4) pure shear plane strain (symmetrical boudinage) occurred locally within the aureole marbles. The direction of maximum extension within the boudinaged marbles is parallel to a stretching lineation which is well developed throughout the deformed western margin of the pluton, and is associated with the simple shear deformation observed in the quartz tectonites. Both pure shear and simple shear deformation are believed to be occurring concurrently with intrusion. Porphyroblast-matrix relationships within the aureole schists indicate that andalusite porphyroblasts have not rotated with respect to compositional layering. In sections viewed parallel to lineation and perpendicular to foliation, a constant angular relationship is observed between planar porphyroblast inclusion trails and matrix foliation traced around the western margin of the pluton. Unwrapping of the matrix foliation, from concordancy with the pluton margin into a planar reference frame, "unspins" the planar inclusion trails into a parallel and constant geographic orientation. This relationship, along with inclusion trail geometry, suggests that initial metamorphism was static, and that penetrative deformation did not occur until late in the growth history of andalusite. Deformation is recorded in the rims of andalusite porphyroblasts as a curvature of inclusion trails into parallelism with the matrix foliation. Inclusion trails begin curving at the same point in porphyroblast rims where inclusions coarsen in grain size and decrease in abundance, therefore a second ‘stage’ of metamorphism is believed to be synchronous with deformation. The strong component of pure shear deformation (plane strain and flattening) observed within various lithologic units, the variation in strain around the pluton/wall rock contact, and the synchroneity of the second stage of metamorphism with deformation suggest that the Papoose Flat pluton was forcefully emplaced. The deformation is believed to be a result of a complex path of forceful inflation, where inflation is not symmetrical as a balloon, but is heterogeneously developed and possibly directed more in the orientation of the lineation. A regional deformational event may, or may not, have occurred synchronously with forceful emplacement. / Master of Science

The Olympic Mountains in northwestern Washington, USA are defined by the arcuate shape of the basaltic Crescent Formation (Fm.) that wraps a faulted and folded meta-sedimentary core. This area was developed through accretion and exhumation by subduction-related processes, but how this relates to the deformational history of the area is not fully understood. The region has been mapped geologically, however little focus has been placed on interpreting meso-scale structures. This study investigates structures along a transect where the Hamma Hamma River crosses the Hurricane Ridge Fault, which juxtaposes the meta-sedimentary core (west) and the basaltic Crescent Fm. (east). In the study area, the meta-sedimentary unit is characterized by outcrop scale folding with a calculated fold axis of 69-->342 and a penetrative foliation with a representative orientation of (178, 75). The folds and foliation are crosscut by two fracture populations with representative orientations of (115, 61) and (303, 76). The pillow basalts of the Crescent Fm. are near vertical, N-S striking beds that are cut by four fault groups. Fault Groups A and B have representative orientations of (304, 37) and (207, 59), respectively, and are associated with similarly oriented fracture populations. Fault Group C crosscuts Groups A and B and has a representative orientation of (031, 61). Fault Group D runs subparallel to the outcrop, cuts all other faults, and has a representative orientation of (087, 50). From an interpretation of this data, a deformation model is presented that proposes three distinct periods of deformation under three different states of stress. The first period was dominated by E-W or ENE-WSW oriented compression, followed by a period of N-S or NNW-SSE oriented compression, followed by vertical compression.