1. Gibbs-Duhem equation describes how T and P changes affect free energy (as chemical potential) Geothermobarametry Clausius-Clapeyron Reaction with big  S R change a good barometer, reaction with a big  V R change a good thermometer….

3. Thermobarometry reactions Exchange Reactions - For solid solution series (Fe-Mg in olivine or pyroxene for example) T and P control the equilibrium distribution Solvus thermometry – For minerals that exsolve, T at which 1 phase splits to 2 components dtermined by chemistry of the 2 components Trace element substitution into a certain mineral is T/P dependent (K D changes with T and P!) Isotope distributions in minerals are also T/P dependent

4. Common thermometers Exchange thermometers MineralsElements garnet-biotiteFe-Mg garnet-cordieriteFe-Mg garnet-clinopyroxeneFe-Mg garnet-orthopyroxeneFe-Mg garnet-hornblendeFe-Mg garnet-olivineFe-Mg olivine-spinelFe-Mg two Fe-Ti oxides (e.g., ilmenite-magnetite) Fe-Ti Solvus thermometers MineralsElements calcite-dolomiteCa-Mg clinopyroxene-orthopyroxeneCa-Mg/Fe plagioclase-alkali feldsparK-Na muscovite-paragoniteK-Na monazite-xenotimeCe-Y MineralsElements quartz-rutileTi (in quartz) zircon-rutile Ti (in zircon), Zr (in rutile) hornblende- plagioclase Na-Ca quartz-magnetite oxygen isotopic ratio calcite-quartz, calcite- graphite carbon isotopic ratio

5. Barometers Net transfer barometers AssemblageAcronym(s) garnet-Al2SiO5-quartz-plagioclaseGASP, GPAQ garnet-rutile-Al2SiO5-ilmenite-quartzGRAIL garnet-rutile-ilmenite-plagioclase-quartzGRIPS garnet-plagioclase-muscovite-biotite*GPMB garnet-plagioclase-hornblende-quartzGPHQ garnet-plagioclase-orthopyroxene-quartz garnet-plagioclase-clinopyroxene-quartz garnet-omphacite-kyanite-quartz/coesite (+/- phengite) K-feldspar-jadeite-quartz garnet-cordierite-sillimanite-quartz

6. Garnet-Plagioclase-Kyanite-Quartz barometer

7. Garnet-Biotite Geothermometer From Selverstone,: http://serc.carleton.edu/files/NAGTWorkshops/petrology/teaching_examples/Selverstone_thermobarometry.pdf