Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Intersecting Isograds at Whetstone Lake Dugald Carmichael (1970) Journal of Petrology, 11, 147-181. Pelitic and calcareous rocks Wide range of chemical compositions Textures indicate 1 metamorphic episode Lowest grade rocks in the area are already in the garnet zone metagabbro metasediments E. pluton is pre-met (has sl. phengite S1 || regional S & across contact) Central pluton is syn-met Components = K2O-Al2O3-MgO-FeO-SiO2-H2O How many? 5 (H2O is mobile) nice AKFM diagram (proj. from Q and Mu) Expect 5-phase assemblages (6 phases = univariant if eqm), but will see only 3 in projection Extra components: Phase-makers TiO2 & P2O5 can be ignored as add 1 component and only 1 phase (Il & Ap) Partitioners- instead of new phase will act as solute and make solid solutions 5 reactions occur in the area: 1. Chl + Ms + Grt = St + Bt + Qtz + H2O 2. Chl + Ms + St + Qtz = Ky + Bt + H2O 3. Ky = Sill 4. St + Ms + Qtz = Sill + Grt + Bt + H2O 5. Bt + Cal + Qtz = Ca-amphibole + Kfs + CO2 + H2O These can be documented texturally across each isograd 1. Chl + Ms + Grt = St + Bt + Qtz + H2O f = 6, so univariant in KFMAS-H Below the isograd Above the isograd What isograd would you call this? What minerals appear and disappear? At A, B, C, D, E? Within the "St-Bi" zone get a Continuous Reaction: Chl + Ms = St + Bt + Qtz + H2O f = 5 (divariant in KFMAS-H) 2. Chl + Ms + St + Qtz = Ky + Bt + H2O f = 6, so univariant in KFMAS-H Below the isograd Above the isograd 3. Ky = Sill Polymorphic transformation- univariant in Al2SiO5 Above the isograd 4. St + Ms + Qtz = Sill + Grt + Bt + H2O f = 6, so univariant in KFMAS-H 5. Bt + Cal + Qtz = Ca-amphibole + Kfs + CO2 + H2O This reaction is not a pelitic one, but occurs in more calcic rocks