Slide 1Slide 2Thermobarometry reactionsSlide 4BarometersGarnet-Biotite GeothermometerGarnet-Plagioclase-Kyanite-Quartz barometer•Gibbs-Duhem equation describes how T and P changes affect free energy (as chemical potential)Geothermobarame tryRRGVSTP 0Clausius-ClapeyronReaction 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 dependentCommon thermometersExchange thermometers Minerals Elementsgarnet-biotite Fe-Mggarnet-cordierite Fe-Mggarnet-clinopyroxene Fe-Mggarnet-orthopyroxene Fe-Mggarnet-hornblende Fe-Mggarnet-olivine Fe-Mgolivine-spinel Fe-Mgtwo Fe-Ti oxides (e.g., ilmenite-magnetite) Fe-TiSolvus thermometers Minerals Elementscalcite-dolomite Ca-Mgclinopyroxene-orthopyroxene Ca-Mg/Feplagioclase-alkali feldspar K-Namuscovite-paragonite K-Namonazite-xenotime Ce-YMinerals Elementsquartz-rutile Ti (in quartz) zircon-rutileTi (in zircon), Zr (in rutile) hornblende-plagioclaseNa-Caquartz-magnetiteoxygen isotopic ratio calcite-quartz, calcite-graphitecarbon isotopic ratioBarometersNet transfer barometers Assemblage Acronym(s)garnet-Al2SiO5-quartz-plagioclase GASP, GPAQ garnet-rutile-Al2SiO5-ilmenite-quartz GRAILgarnet-rutile-ilmenite-plagioclase-quartz GRIPSgarnet-plagioclase-muscovite-biotite* GPMBgarnet-plagioclase-hornblende-quartz GPHQgarnet-plagioclase-orthopyroxene-quartz garnet-plagioclase-clinopyroxene-quartz garnet-omphacite-kyanite-quartz/coesite (+/- phengite) K-feldspar-jadeite-quartz garnet-cordierite-sillimanite-quartzGarnet-Biotite GeothermometerFrom Selverstone,:http://serc.carleton.edu/files/NAGTWorkshops/petrology/teaching_examples/Selverstone_thermobarometry.pdfGarnet-Plagioclase-Kyanite-Quartz
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