Applying any thermobarometric calibration to assess equilibration conditions of assemblages necessarily involves uncertainties and errors. Some errors are inherent in the thermodynamic derivation, others are related to analytical problems, and these are additional to the possible errors due to the textural assessment of selecting minerals (ie, analytical points) to use as input data.

In these calibrations errors arising purely from fitting statistics, without propagating additional analytical errors, are as follows:

• Gnt-Spl, Pressure, MAS ± 1.1 kbar, FAS ± 0.8 kbar
• Spl-Crd, Pressure, MAS ± 0.6 kbar, FAS ± 1.0 kbar, Temperature ± 112°C
• Gnt-Crd, Pressure, MAS ± 0.6 kbar, FAS ± 0.6 kbar, Temperature ± 50°C

see Nichols et al. (1992) for a detailed discussion of thermodynamic modelling and consideration of errors.

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