Synthetic gedrite: a stable phase in the system MgO-Al 2 O 3 -SiO 2 -H 2 O (MASH) at 800 °C and 10 kbar water pressure, and the influence of FeNaCa impurities

Sapphirine-bearing assemblages in the system MgOAl2O3SiO2: a continuing ambiguity

“…Reactions involving the non-ideal sapphirine (r31) and (r61) do not intersect, either under fluid-absent condition, when reaction (r61) enters the And stability field at low temperatures, nor at P ¼ P H 2 O and P ¼ P CO 2 in the Ky stability field, because sapphirine becomes very alumina-rich and the reaction lines curve away from one another, thus excluding the existence of invariant point I 6 . While investigating the stability field of gedrite in MASH, Fischer et al (1999) observed the appearance of this phase together with Spr and Ky at 850°C and 1.1 GPa, which can be considered as evidence supporting our non-ideal sapphirine model. In MASH, Spr + Ky must have a very limited stability field due to appearance of competing assemblages involving other hydrous phases, such as chlorite (Seifert, 1974) or boronfree kornerupine (Wegge & Schreyer, 1994).…”

Fluid-assisted interaction of peraluminous metapelites with trondhjemitic magma within the Petronella shear-zone, Limpopo Complex, South Africa

“…cordierite, gedrite, staurolite, and biotite, in dependence on temperature. The diagram predicts that Na-bearing gedrite is stable within the wide temperature interval from above 850 down to 510 • C. This is consistent with the experimental and petrological facts that gedrite stability significantly increases with Na substitution (Fischer et al, 1999;Diener et al, 2008) and that Nagedrite is stable at the UHT metamorphic conditions (cf. Kanazawa et al, 2009).…”

Quantitative phase petrology of cordierite–orthoamphibole gneisses and related rocks

“…Cordierite–orthoamphibole gneisses consist mainly of FeO/Fe 2 O 3 , MgO, Al 2 O 3 and SiO 2 and their phase relations have been investigated in simple model chemical systems such as MgO–Al 2 O 3 –SiO 2 –H 2 O (MASH), FeO–MgO–Al 2 O 3 –SiO 2 –H 2 O (FMASH) and MgO–Al 2 O 3 –Fe 2 O 3 –SiO 2 –H 2 O (MASHO) through experiments (Schreyer & Seifert, 1969; Massonne, 1989; Fockenberg & Schreyer, 1994; Fischer et al. , 1999) and classical chemographic relationships (Robinson & Jaffe, 1969; Harley, 1985; Hudson & Harte, 1985; Spear & Rumble, 1986; Ouzegane et al.…”