Error propagation for barometers: 1. Accuracy and precision of experimentally located end-member reactions

A new procedure for calculating the precision and accuracy of end-member reactions is presented that accounts for the kinetics of reaction progress and possible displacements between the experimental and true P-T reference frames. Application to recently collected experimental data indicates that the estimated precision (1σ) of the position of an end-member reaction at metamorphic temperatures (~900 K) using a single set of experimental data may be ± 100 to ± 310 bars and that a minimum estimate of accuracy (1σ) may be on the order of ± 270 to ± 410 bars, depending on how precisely the reaction is bracketed and assuming 1σ potential systematic errors in pressure and temperature of ± 250 bars and ± 5°C, respectively. The accuracy of the grossular-anorthite-kyanite-quartz (GASP) reaction position using five different studies is estimated to be between ± 350 and ± 380 bars (1σ) at 900 K, depending on whether the individual studies were calibrated using independent standards. -Authors