Deformation Mechanisms, Microstructures, and Flow Laws for Quartzo-Feldspathic Aggregates

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Tullis0106859This research will investigate deformation mechanisms in quartzo-feldspathic rocks with the aim of enhancing our understanding of deformation history of the crust as well as to facilitate accurate modeling of the stress levels and stain partitioning in different tectonic settings. The investigators will work on 3 research projects. First they will complete an experimental calibration of the recrystallized grain size piezometer for the 3 recrystallization mechanisms and corresponding dislocation creep regimes previously identified in quartz, and will test them with application to a natural shear zone which spanned a wide temperature range including all 3 regimes. Second, they will complete an experimental study of the processes by which a relatively small amount of weak mica in a quartza-feldspathic aggregate becomes interconnected and dispersed, leading to profound strain weakening and localization into ductile shear zones. Third, they will complete a reconnaissance experimental study of the variation in deformation mechanisms and strength across the plagioclase solid solution series. Based on that study the investigators will choose 2 or 3 key compositions for further stepping experiments in a molten salt assembly to determine flow law parameters.