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Intersecting Isograds at Whetstone Lake Dugald Carmichael (1970) Journal of Petrology, 11, 147-181.

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. metasediments.

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Intersecting Isograds at Whetstone Lake Dugald Carmichael (1970) Journal of Petrology, 11, 147-181.

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  1. Intersecting Isograds at Whetstone LakeDugald 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

  2. metasediments metagabbro E. pluton is pre-met (has sl. phengite S1 || regional S & across contact) Central pluton is syn-met

  3. 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

  4. 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 5 reactions occur in the area: These can be documented texturally across each isograd

  5. 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?

  6. Within the "St-Bi" zone get a Continuous Reaction: Chl + Ms = St + Bt + Qtz + H2O f = 5 (divariant in KFMAS-H)

  7. Below the isograd 2. Chl + Ms + St + Qtz = Ky + Bt + H2O f = 6, so univariant in KFMAS-H Above the isograd

  8. 3. Ky = Sill Polymorphic transformation- univariant in Al2SiO5 Above the isograd

  9. 4. St + Ms + Qtz = Sill + Grt + Bt + H2O f = 6, so univariant in KFMAS-H

  10. 5. Bt + Cal + Qtz = Ca-amphibole + Kfs + CO2 + H2O This reaction is not a pelitic one, but occurs in more calcic rocks

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