Geothermobarametry GibbsDuhem equation describes how T and P

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

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 (KD changes with T and P!) • Isotope distributions in minerals are also T/P dependent

Exchange thermometers Common thermometers Minerals Elements garnet-biotite Fe-Mg quartz-rutile Ti (in quartz) garnet-cordierite Fe-Mg garnet-clinopyroxene Fe-Mg zircon-rutile Ti (in zircon), Zr (in rutile) garnet-orthopyroxene Fe-Mg Na-Ca garnet-hornblende Fe-Mg hornblendeplagioclase oxygen isotopic ratio carbon isotopic ratio garnet-olivine Fe-Mg quartz-magnetite olivine-spinel Fe-Mg two Fe-Ti oxides (e. g. , ilmenite-magnetite) Fe-Ti calcite-quartz, calcitegraphite Solvus thermometers Minerals Elements calcite-dolomite Ca-Mg clinopyroxene-orthopyroxene Ca-Mg/Fe plagioclase-alkali feldspar K-Na muscovite-paragonite K-Na monazite-xenotime Ce-Y

Barometers Net transfer barometers Assemblage Acronym(s) garnet-Al 2 Si. O 5 -quartz-plagioclase GASP, GPAQ garnet-rutile-Al 2 Si. O 5 -ilmenite-quartz GRAIL garnet-rutile-ilmenite-plagioclase-quartz GRIPS garnet-plagioclase-muscovite-biotite* GPMB garnet-plagioclase-hornblende-quartz GPHQ garnet-plagioclase-orthopyroxene-quartz garnet-plagioclase-clinopyroxene-quartz garnet-omphacite-kyanite-quartz/coesite (+/- phengite) K-feldspar-jadeite-quartz garnet-cordierite-sillimanite-quartz

Garnet-Plagioclase-Kyanite-Quartz barometer

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