Fig. 2
From: Metamorphic pressure variation in a coherent Alpine nappe challenges lithostatic pressure paradigm
Equilibrium phase diagram of whiteschist and phengite composition in whiteschist and metagranite samples. a Whiteschist thermodynamic calculation in the system KFMASH, using DOMINO software and the Berman database20 (1988, 92 update), with the peak-pressure–temperature field in blue. H2O-saturated conditions were used with the following composition in moles: Si (61.79), Al (20), Fe (2.23), Mg (12.17), and K (3.82). Mineral abreviations are as follows: bt: biotite; car: carpholite; chl: chlorite; crd: cordierite; cld: chloritoid; grt: garnet; ky: kyanite; opx: orthopyroxene; tlc: talc; wm: white mica. Bold lines labelled with (1) and (2) indicate dehydration reactions considered in the discussion. b OH− content in phengites in two whiteschist samples vs. silica (Si) content per formula unit (p.f.u.). Error bars represent the propagated uncertainty (1 SE) of the SE of the SIMS analyses, the SE of the reference material used for SIMS analyses, and the uncertainty on the electron microprobe measurements. c Silica (Si) content of white mica per formula unit (p.f.u.) in metagranite is plotted vs. the distance of the corresponding metagranite from the whiteschist body. The maximum pressure for the corresponding silica content is indicated assuming a temperature of 550 °C and a H2O activity (aH2O) of 1. d OH− content in phengites in metagranites vs. the distance of the corresponding metagranite from the whiteschist body. Error bars represent the propagated uncertainty (1 SE) of the SE of the SIMS analyses, the SE of the reference material used for SIMS analyses, and the uncertainty on the electron microprobe measurements. Note that H2O activities >1 in b and d result from the accumulated uncertainty related to SIMS H2O content measurement and electron microprobe major elements measurement
