96NC67: Garnet Core and Rim ThermobarometryTemperature (oC)Pressure (kbars)450550500700650600246810125.0 kbars640 oCGarnet Core P-T (from pseudosection method)Garnet Rim EquilibriaUncertainty EllipsePeak AssemblageGarnet P-T TrajectoryPressure- Temperature PseudosectionsP-T Path Determination with Pseudosections and Garnet ChemistryP-T pseudosection: A P-T phase diagram portraying the theoretical distribution of equilibrium mineral assemblages in P-T space for a single bulk-rock composition.An important distinction should be made between the concept of a P-T pseudosection and the prominently used P-T projection (petrogenetic grid). Lines on a P-T projection represent possible chemical reactions a particular rock may experience. However, all the reactions on a P-T projection are never experienced by a single bulk rock composition; only a subset of the possible reactions are experienced.In contrast, lines on a P-T pseudosection represent the P-T conditions at which the mode of a particular phase goes to zero for a specified bulk composition, and rarely represent any single reaction which appears on a simplified petrogenetic grid. If the bulk composition of a rock changes, than the positions of mode = 0 lines on a pseudosection will change, but the positions of reactions on a petrogenetic grid will not change. Therefore, pseudosections are a useful tool for showing the
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Chemical reaction, Silicate minerals, Garnet Rim Thermobarometry, garnet rim, garnet core