Internally consistent estimates of pressure and temperature: the staurolite problem.

Abstract

Reconciliation of mutually consistent data on staurolite equilibria from different laboratories with an internally consistent thermodynamic base was found to be impossible. Application of experimental equilibrium calibrations to phases of the Shuswap metamorphic complex near Azure Lake, British Columbia, resulted in T that are too high or H2O activities that are too low to account for the P and T that prevailed during crystallization and deformation. No systematic error was identified in any of the experimental data. Additional experimental data or more refined solid-solution models may solve the problem. Thermodynamic equations, activity-composition relations, and solid-solution models are appended.-M.S.