COLLABORATIVE RESEARCH: Interactions in Time and Space of Thermal and Mechanical Processes During Orogeny, Old Woman Mountains Area, SE California

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Southeastern California preserves a record of 2 billion years of tectonic history that occurred along the continental margin of the United States. Previous work on this consortium project has provided considerable information about Precambrian structural evolution, Mesozoic compression and Cenozoic exten- sional events in the Old Woman Mountains. This renewal will build on this information to address Mesozoic orogenic processes in continental crust, particularly on the typically obscure early stages of orogeny. The Mesozoic upper crust in this area was first tectonically buried to depths ranging from near zero to more than 20 kilometers, then exhumed rapidly at the end of the Mesozoic, and subsequently preserved largely intact through the mid-Tertiary extension that strongly overprinted adjacent regions. Work will focus on developing prograde thermochrono- metry for the region, the thermal and kinematic history of ductile shear zones, on refinement of thermobarometry and its application to rapidly evolving orogen, the linkage between pluton emplacement and tectonism and attempting to characterize the lower continental crust through high-pressure xenoliths. Results will be integrated in an attempt to discover in some detail the interactions of thermal and mechanical processes active in continental margin dynamics.