Contributions to Mineralogy and Petrology

, Volume 76, Issue 1, pp 92–97 | Cite as

Geobarometry and geothermometry of plagioclase-biotite-garnet-muscovite assemblages

  • Edward D. Ghent
  • Mavis Z. Stout


The assemblage, plagioclase-biotite-garnet-muscovite is widespread in garnet to lower sillimanite zone metasedimentary rocks. The equilibria, (1) pyr+gr+mu=3an+phl and (2) alm+gr+mu=3an+ann, involve a change in Al coordination from 6 to 4 and in Mg-Fe coordination from 8 to 6 and should be strongly pressure dependent. Using an ionic solution model we can define solid activity products for (1) and (2). Using a linear least squares analysis of activity products and estimated P-T from natural assemblages we can derive equilibrium constant equations for (1) and (2). Combining either of these equations with that for Mg-Fe exchange for garnet-biotite from Ferry and Spear (1978) allows estimation of P and T of metamorphism. Pressures estimated from these equilibria compare favorably to pressures estimated from garnet-plagioclase-Al2SiO5-quartz equilibria.


Mineral Resource Activity Product Solution Model Ionic Solution Sillimanite 
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  1. Anderson GM (1977) Uncertainties in calculations involving thermodynamic data in Greenwood HJ ed Short course in application of thermodynamics to petrology and ore deposits. Mineral Assoc Canada short course handbook 2, pp 199–215Google Scholar
  2. Carmichael DM (1978) Metamorphic bathozones and bathograds: a measure of the depth of post-metamorphic uplift and erosion on a regional scale. Am J Sci 278:769–797Google Scholar
  3. Chatterjee ND, Johannes W (1974) Thermal stability and standard thermodynamic properties of synthetic 2M muscovite, KAl2AlSi3O10(OH)2. Contrib Mineral Petrol 48:89–114Google Scholar
  4. Cressey G, Schmid R, Wood BJ (1978) Thermodynamic properties of almandine-grossular solid solutions. Contrib Mineral Petrol 67:379–404Google Scholar
  5. Eugster HP, Albee AL, Bence AE, Thompson JB jr, Waldbaum DR (1972) The two phase region and excess mixing properties of paragonite-muscovite crystalline solutions. J Petrol 13:147–179Google Scholar
  6. Ferry J (1976) P, T, \(f_{{\text{CO}}_{\text{2}} } \) and \({\text{f}}_{{\text{H}}_{\text{2}} {\text{O}}} \)during metamorphism of calcareous sediments in the Waterville-Vassalboro area, South-central Maine. Contrib Mineral Petrol 57:119–143Google Scholar
  7. Ferry J (1980) A comparative study of geothermometers and geobarometers in pelitic schists from south-central Maine. Am Mineral 65:720–732Google Scholar
  8. Ferry JM, Spear FS (1978) Experimental calibration of the partitioning of Fe and Mg between biotite and garnet. Contrib Mineral Petrol 66:113–117Google Scholar
  9. Ganguly J (1979) Garnet and clinopyroxene solid solutions, and geothermometry based on Fe-Mg distribution coefficient. Geochim Cosmochim Acta 43:1021–1029Google Scholar
  10. Ganguly J, Kennedy GC (1974) The energetics of natural garnet solid solution. I. Mixing of the aluminosilicate end-members. Contrib Mineral Petrol 48:137–148Google Scholar
  11. Ghent ED (1975) Temperature, pressure, and mixed-volatile equilibria attending metamorphism of staurolite-kyanite-bearing assemblages, Esplanade Range, British Columbia. Geol Soc Am Bull 86:1654–1660Google Scholar
  12. Ghent ED (1976) Plagioclase-garnet-Al2SiO5-quartz: a potential geobarometer-geothermometer. Am Mineral 61:710–714Google Scholar
  13. Ghent ED, Robbins DB, Stout MZ (1979) Geothermometry, geobarometry, and fluid compositions of metamorphosed calc-silicates and pelites, Mica Creek, British Columbia. Am Mineral 64:874–885Google Scholar
  14. Ghent ED, Simony PS, Knitter CC (1980) Geometry and pressuretemperature significance of the kyanite-sillimanite isograd in the Mica Creek area, British Columbia. Contrib Mineral Petrol 74:67–73Google Scholar
  15. Helgeson HC, Delany JM, Nesbitt HW, Bird DK (1978) Summary and critique of the thermodynamic properties of rock-forming minerals. Am J Sci 278AGoogle Scholar
  16. Holdaway MJ (1971) Stability of andalusite and the aluminum silicate phase diagram. Am J Sci 271:97–131Google Scholar
  17. Kerrick DM, Darken LS (1975) Statistical thermodynamic models for ideal oxide and silicate solid solutions. Geochim Cosmochim Acta 39:1431–1442Google Scholar
  18. Newton RC, Haselton HT (1980) Thermodynamics of the garnetplagioclase-Al2SiO5-quartz geobarometer. In: Thermodynamics of minerals, Springer Verlag (in press)Google Scholar
  19. Orville PM (1972) Plagioclase cation exchange equilibria with aqueous chloride solution: results at 700° C and 2,000 bars in the presence of quartz. Am J Sci 272:234–272Google Scholar
  20. Pigage LC (1976) Metamorphism of the Settler schist, southwest of Yale, British Columbia. Can J Earth Sci 13:405–421Google Scholar
  21. Richardson S, Powell R (1976) Thermal causes of the Dalradian metamorphism in the Central Highlands of Scotland. Scott J Geol 12:237–268Google Scholar
  22. Robie RA, Hemingway BS, Fisher JR (1978) Thermodynamic properties of minerals and related substances at 298.15° K and one bar (105 pascals) pressure and at higher temperatures. US Geol Surv Bull 1452Google Scholar
  23. Schmid R, Wood BJ (1976) Phase relationships in granulitic metapelites from the Ivrea-Verbano Zone (northern Italy). Contrib Mineral Petrol 54:255–279Google Scholar
  24. Thompson AB (1976) Mineral reactions in pelitic rocks: II. Calculation of some P-T-X (Fe-Mg) phase relations. Am J Sci 276:401–454Google Scholar
  25. Tracy RJ (1978) High grade metamorphic reactions and partial melting in pelitic schist, west-central Massachusetts. Am J Sci 278: 150–178Google Scholar
  26. Wones DR (1972) Stability of biotite; a reply. Am Mineral 57:316–316Google Scholar
  27. Woodsworth GJ (1979) Metamorphism, deformation and plutonism in the Mount Raleigh pendant, Coast Mountains, British Columbia. Geol Surv Canada Bull 295:58 pGoogle Scholar
  28. Zen E-an (1973) Thermochemical parameters of minerals from oxygen-buffered hydrothermal equilibrium data: method, application to annite and almandine. Contrib Mineral Petrol 39:65–80Google Scholar

Copyright information

© Springer-Verlag 1981

Authors and Affiliations

  • Edward D. Ghent
    • 1
  • Mavis Z. Stout
    • 1
  1. 1.Department of Geology and GeophysicsUniversity of CalgaryCalgaryCanada

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