Collaborative Research: Calibration and Application of Trace Element Thermobarometry in Metamorphic Rocks

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9706349 Essene This is a collaborative project between Essene, Manning and Riciputi. Key chemical reactions involving Zr and Ti in garnets will be calibrated both empirically and experimentally as thermobarometers and applied to zoned garnets in various metamorphic terranes. Empirical calibration of GZQ and GRQ using measured Zr and Ti levels from SIMS data for buffered New England garnets will be combined with thermodynamic estimations and calculations to yield provisional phase diagrams. The GZQ reaction will be calibrated experimentally with a piston-cylinder apparatus at UCLA (Manning) with compositional reversals and analysis of run products by Oak Ridge SIMS (Riciputi). Experiments on garnet-rutile-quartz and garnet-rutile-corumdum-sillimanite that have already been conducted by Manning, Bohlen and coworkers will be evaluated with the electron microprobe for their applicability to calibration of GRQ. Empirical calibration of KD thermometry for REE's and Y will be undertaken for selected garnet-monazite and garnet-epidote pairs from Greenville terrane and from New England using SIMS and EMP data. Combination of GZQ and GRQ barometry with REE KD thermometry offers a strong potential for obtaining more complete P-T-t paths experienced by granulite terranes and should elucidate mechanisms responsible for granulite facies genesis.