Calibration of the garnet–biotite–Al2SiO5–quartz geobarometer for metapelites. (8th September 2017)

• Record Type: Journal Article
• Authors: Wu, Chun‐Ming
• Is Part Of: Journal of metamorphic geology. Volume 35:Number 9(2017:Dec.)
• Page Start: 983
• Page End: 998
• Publication Date: 2017-09-08
• Subjects: Application -- biotite -- calibration -- garnet -- geobarometer; Metamorphism (Geology) -- Periodicals; 552.4
• DOI: 10.1111/jmg.12264
• Languages: English
• ISSNs: 0263-4929

Abstract

Abstract: A garnet–biotite–Al2 SiO5 –quartz (GBAQ) geobarometer was empirically calibrated using more than 700 natural metapelites with a broad compositional range of garnet and biotite under P–T conditions of 450–950°C and 1–17 kbar. In the calibration, activity models of garnet and biotite identical to those in the garnet–biotite (GB) geothermometer of Holdaway [ American Mineralogist 2000, 85: 881–892] were used. Therefore, the GBAQ geobarometer and the GB geothermometer can be simultaneously applied to iteratively estimate metamorphic P–T conditions. Successful applications of the GBAQ geobarometer to natural metapelites certify its validity. Most importantly, when plagioclase is absent or CaO components in garnet and/or plagioclase are deficient, this geobarometer may prove useful for estimating metamorphic pressures. The random error of the present GBAQ geobarometer is inferred to be around ±1.8 kbar. An electronic spreadsheet is available as Table S4 to apply the GBAQ geobarometer in combination with the GB geothermometer.