Contact Aureole Rheology

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0106557 YoshinobuRates of processes control a wide variety of geologic phenomena. With the development of more precise and refined radiometric age dating techniques, it is becoming increasingly apparent that processes in magmatic arcs such as magma generation and ascent may occur at relatively fast rates and over a wide range of durations. In contrast, existing data sets for regional deformation suggest that rates of various processes such as faulting, shearing, and folding are several orders of magnitude slower than rates of magma generation, migration, and emplacement. This research is utilizing field, microstructural, and experimental rock deformation data sets to address the following questions: (1) What micro- and macro-scale deformation mechanisms accommodate deformation in contact aureoles? (2) What are the magnitudes of stress in the host rocks during plastic deformation associated with chamber construction? (3) What are the host rock strain rates during plastic deformation associated with chamber construction? And (4) What are "typical" viscosities in contact aureoles? Detailed mapping and microstructural analysis conducted on two pluton-host rock systems, exposed in the Clark Mountains of eastern California, as well as application of experimentally-derived flow laws and paleo-piezometers (paleo-stress gauges) to deformed contact aureole rocks are currently being carried out to evaluate these questions and provide constraints on contact aureole stresses, strain rates and viscosities.