Field and geochemical studies of continental tectonic processes

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Over the next five years, the research that I intend to undertake includes: (1) A study of the thermal history of at least two transects across the Canadian Cordillera and adjacent Western Canada Sedimentary Basin. This should improve our understanding of ties between orogenic 'events' and subsidence/depositional events in the basin; it should also help constrain the timing of petroleum generation and migration in the basin. (2) Continuation of mapping and Apatite Helium dating in the northern California Coast Ranges, in an attempt to use isochrons within the Apatite Helium fossil partial retention zone as structural markers in this large, multiply deformed terrain. This is a novel application of a new dating method as a geochemical mapping tool. If successful, this should result in significant improvements in the understanding of the kinematic evolution of transtensional basins in general, and along the Maacama Fault in particular. (3) Development of thermal models for parts of the crust in the central Basin and Range Province; this work is based on studies of the distribution of radioactive heat producing elements in the crustal exposures of the South Virgin Mts., Nevada. It should permit testing of models that call for a hot, fluid mid-crustal layer during Tertiary extension, and of suggestions that the Proterozoic anorogenic granites in the region formed by in-situ melting due to radiogenic heating of an otherwise stable crust. (4) A study of which minerals contain most of the radioactive elements in samples from the Sierra Nevada batholith, California and South Virgin Mts., Nevada. This will help determine to what extent the natural distribution of radioactive minerals is controlled by primary magmatic processes versus later hydrothermal alteration.