Mineral Reactions Mineral reactions are the basis for much of our understanding of metamorphism. Our estimates of pressures and temperatures experienced.

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Presentation transcript:

Mineral Reactions Mineral reactions are the basis for much of our understanding of metamorphism. Our estimates of pressures and temperatures experienced by rocks during metamorphism are based on metamorphic reactions.

Mineral Reactions There are two basic types of mineral reactions: Continuous Discontinuous

Discontinuous Reactions (after Liou, 1987) Minerals that are the products of reaction are different from the reactants Ex: Albite -> Jadeite + Quartz NaAlSi3O8 -> NaAlSi2O6 + SiO2 Jadeite and Quartz are different from Albite Generally make good geobarometers because they have a gentle slope on a P-T graph

(after Liou, 1987) Albite -> Jadeite + Quartz Geobarometer A good geobarometer has a gentle slope

Continuous Reactions Minerals that are the products of reaction are the same as the reactants. Elements are exchanged between different minerals Ex: Fe-Mg exchange between garnet and pyroxene Fe-garnet + Mg-pyroxene -> Mg-garnet + Fe-pyroxene Fe3Al2Si3O12 + 3CaMgSi2O6 -> Mg3Al2Si3O12 + 3CaFeSi2O6 Generally make good geothermometers

Garnet-clinopyroxene geothermometer A good geothermometer has a steep slope after Krogh Ravna 2000