Monazite as a Thermochronometer for Prograde Metamorphism

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9316166 Harrison This project proposes experiments that will lead to a better understanding of monazite as a thermochronometer. Monazite was selected for study because its retentive nature for Pb* and its unusual (for an accessory mineral) behavior during diagenesis suggests its use as a system capable of continuously recording thermochronological information during prograde metamorphism of a pelite. Three distinct, but ultimately interconnected, studies are required to exploit this observation: development of U-Th-Pb microanalysis for monazite, the stability and reaction kinetics of LREE oxides in pelitic assemblages, and Pb diffusion in monazite. These studies will lead to utilization of the Th-Pb system to date discrete reaction events in the heating phase of orogenic terranes as well as a refined knowledge of the closure temperature for Pb in monazie.