Geothermobarametry Gibbs Duhem equation describes how T and P changes affect free energy as chemical potential Clausius Clapeyron S R P T G 0 VR Reaction with big SR change a good barometer reaction with a big VR 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 Common thermometers Exchange thermometers Minerals Elements Minerals Elements garnet biotite Fe Mg quartz rutile Ti in quartz garnet cordierite Fe Mg zircon rutile garnet clinopyroxene Fe Mg 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 Al2SiO5 quartz plagioclase GASP GPAQ garnet rutile Al2SiO5 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 Biotite Geothermometer From Selverstone http serc carleton edu files NAGTWorkshops petrology teaching examples Selverstone thermobarometry pdf Garnet Plagioclase Kyanite Quartz barometer
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