Recalibration of the GASP geobarometer in light of recent garnet and plagioclase activity models and versions of the garnet-biotite geothermometer

摘要: The garnet-Al silicate-plagioclase (GASP) geobarometer has been recalibrated using four recent garnet activity models, analogous garnet-biotite temperature and two plagioclase models. A typical sillimanite-bearing sample that formed at about 5.25 kbar, 575 °C shows a possible P range of ~0.7 kbar due to T error, ~1 model, ~0.9 ~5.4 experimental end-member reversals extended by one sigma. Calibrations were further constrained with the kyanite-sillimanite (K-S) phase boundary such best fit 76 pelitic schist samples from 11 localities provides an individual calibration for each eight combinations models appropriate geothermometer. Samples low grossular or anorthite component rejected. calibrations are pass through best-determined portion GASP 1230 °C, 26.6 kbar. These provide self-consistent tend compensate error in expressions. also tested on set 59 Alps. The recommended is average model Holdaway (2000), Fuhrman Lindsley (1988) H Grs = −6628521, S 258.76 combine remaining phases Berman database produce optimum curve. thermodynamic data only. Error ±0.8 absolute ±0.6 relative. Geological largest many these samples. Care should be taken sure analyzed biotite near garnet, peak- portions selected, Al silicate determined, calculated most accurate possible. represent improvement over previous published calibrations. available distribution as three programs ( , - intersection) DOS-based personal computer.