Thermodynamic modelling of sodic pyroxene solid-solution and its application in a garnet-omphacite-kyanite-coesite geothermobarometer for UHP metamorphic rocks. (ultrahigh-pressure)

Article Abstract:

A thermodynamic model for sodic pyroxene solid-solution was developed and applied to natural ultrahigh-pressure eclogite samples taken from Rongcheng County in the Su-Lu region of eastern China and the Dora Maira Massif in the Western Alps. The model includes quantitatively derived values from data obtained from other experiments for overall excess interaction variables. Results of the application of the geothermobarometer yielded metamorphic conditions of 3.4 GPa and 800 degrees C for the two sets of samples analyzed.

Models, China, Thermodynamics, Pyroxene, Western Alps

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Phase equilibrium and stable isotope constraints on the formation of metasomatic garnet-vesuvianite veins (SW Adamello, N Italy)

Article Abstract:

Isotope transport and mineral-fluid exchange mechanisms affect the formation of metasomatic garnet-vesuvianite veins in the Adamello, Italy, intrusive marble-granodiorite contact. Precipitation of vein garnet occurs in isotopic equilibrium with the metasomatic fluid. The calcite-fluid isotopic exchange during calcite recrystallisation causes the equilibrium between preexisting calcite and the vein-forming fluid. The carbon and oxygen transport, and mineral-fluid exchange are discussed.

Italy

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Ion microprobe evidence for the mechanisms of stable isotope retrogression in high-grade metamorphic rocks

Article Abstract:

A study of high-grade metamorphic rocks by a combined ion microprobe and bulk mineral analysis with diffusion modeling revealed the significant influence exerted by interdiffusion in stabilizing the nature of arrangement of stable isotopes in gradually cooling rocks. Assessment of multiple fractionations in rocks is essential in predicting the nature of retrogression in the rocks.

Analysis, Diffusion, Diffusion (Physics), Fractionation, Fractional distillation

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