What question did this study set out to answer?

Determine the thermodynamic effects of titanium dioxide (TiO2) and ferric iron (Fe2O3) on greenschist- and amphibolite-facies mineral equilibria in metapelitic rocks.

September 1, 2000Journal of Metamorphic Geology

The effect of TiO2 and Fe2O3 on metapelitic assemblages at greenschist and amphibolite facies conditions: mineral equilibria calculations in the system K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3

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Authors

RWR. W. WhiteUniversity of St Andrews PPowellWestern University HHollandUniversity of Cambridge

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Implication

Thermodynamic modeling demonstrates minimal titanium impact but major ferric iron disruptions in metapelites, indicating that oxidation state strongly shifts staurolite and garnet stability.

Key Points

Determine the thermodynamic effects of titanium dioxide (TiO2) and ferric iron (Fe2O3) on greenschist- and amphibolite-facies mineral equilibria in metapelitic rocks.
Conducted mineral equilibria calculations in the KFMASHTO system using THERMOCALC and its internally consistent thermodynamic dataset.
Calibrated activity–composition relationships for biotite and chloritoid using natural rock data, and for garnet using experimental data.
Incorporated order–disorder thermodynamic models for ilmenite–hematite and magnetite–ulvospinel solid solutions to calculate Ti–Fe partitioning between oxides and silicates.
Small to moderate amounts of TiO2 and Fe2O3 typical of pelitic compositions exert negligible effects on silicate mineral equilibria compared to standard KFMASH calculations.
High concentrations of TiO2 do not significantly modify silicate assemblage stability, whereas Fe2O3-rich metapelites deviate substantially from classical Barrovian metamorphic sequences.
Elevated Fe2O3 substantially contracts the stability fields of staurolite and garnet, restricting their formation to significantly higher pressures.

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White et al. (2000) studied this question.

synapsesocial.com/papers/69d98e7e387cf706986847ef https://doi.org/10.1046/j.1525-1314.2000.00269.x

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Implication

Thermodynamic modeling demonstrates minimal titanium impact but major ferric iron disruptions in metapelites, indicating that oxidation state strongly shifts staurolite and garnet stability.

The effect of TiO2 and Fe2O3 on metapelitic assemblages at greenschist and amphibolite facies conditions: mineral equilibria calculations in the system K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3

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Cite This Study

The effect of TiO2 and Fe2O3 on metapelitic assemblages at greenschist and amphibolite facies conditions: mineral equilibria calculations in the system K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3

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Implication

Key Points

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