An Examination of the Nature and Timing of Pluton Emplace- ment, Northern Sierra Nevada, Calfornia

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Relationships between dated plutons and tectonic deforma- tion have been widely used to constrain timing of regional deformation. The validity of this procedure relies on the ability to determine emplacement-related structures in the plutons from super-imposed tectonic structures. Existing guide- lines are not diagnostic and therefore criteria for distinguish- ing pre-, syn-, and post- tectonic plutons are controversial. This project will carry out a detailed examination of the Merrimac pluton in the Northern Sierra Nevada, California to estimate the strain fields in and around the granitoid. Additionally, computer modeling that simulates pre-, syn-, and post- tectonic pluton emplacement under coaxial and non-coaxial deformation will be performed. By comparing planar sections through the computer generated strain fields with the strain fields obtained from the field data, it is expected that more rigorous criteria will result for recognizing pre-, syn-, and post- tectonic plutons, and therefore, provide more reliable constraints for determining the age of structures in orogenic belts.