Trace Element Distribution Within, Between, and Among Metamorphic Minerals as a Monitor of Reaction History and P-T Evolution

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9903036SpearTrace element distribution between coexisting minerals have beendemonstrated to reveal aspects of the history of rocks that are notrecorded by major elements. This arises because of (1) the relatively slowdiffusivity of trace elements in minerals such as garnet, (2) the extremepartitioning behavior of many trace elements, and (3) the sensitivity oftrace element concentrations to small amounts of reaction progress or P-Tchanges. This study seeks to explore the application of trace elementgeochemistry in metamorphic rocks towards a deeper understanding of Earthhistory. Suites of rocks from several well-characterized localities will beexamined for trace element zoning in garnet and coexisting minerals.Observed zoning patterns will be correlated with the distribution andcompositions of accessory phases such as xenotime, monazite, zircon,apatite and allanite. The zoning patterns will be explained in terms of thewhole-rock reaction history and the temperature dependence of trace elementpartitioning between garnet and accessory phases will be calibrated usingP-T conditions inferred from other thermobarometers. The results of this research will provide new, detailed insightsinto the geologic evolution of the areas studied and will, more generally,provide new tools for the petrologist to apply to the unveiling of Earthhistory