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Contributions to Mineralogy and Petrology

, Volume 140, Issue 3, pp 353–362 | Cite as

Hornblende–garnet–plagioclase thermobarometry: a natural assemblage calibration of the thermodynamics of hornblende

  • Jonathon Dale
  • Tim Holland
  • Roger Powell
Article

Abstract

Calibrations are presented for an independent set of four equilibria between end-members of garnet, hornblende, plagioclase and quartz. Thermodynamic data from a large internally-consistent thermodynamic dataset are used to determine the ΔG° of the equilibria. Then, with the known mixing properties of garnet and plagioclase, the non-ideal mixing in amphibole is derived from a set of 74 natural garnet–amphibole–plagioclase–quartz assemblages crystallised in the range 4–13 kbar and 500–800 °C. The advantage of using known thermodynamic data to calculate ΔG° is that correlated variations of composition with temperature and pressure are not manifested in fictive derived entropies and volumes, but are accounted for with non-ideal mixing terms. The amphibole is modelled using a set of ten independent end-members whose mixing parameters are in good agreement with the small amount of data available in the literature. The equilibria used to calibrate the amphibole non-ideal mixing reproduce pressures and temperatures with average absolute deviations of 1.1 kbar and 35 °C using an average pressure–temperature approach, and 0.8 kbar with an average pressure approach. The mixing data provide not only a basis for thermobarometry involving additional phases, but also for calculation of phase diagrams in complex amphibole-bearing systems.

Keywords

Contrib Mineral Petrol Garnet Granulite Scandinavian Caledonides Willyama Complex Panamint Mountain 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • Jonathon Dale
    • 1
  • Tim Holland
    • 1
  • Roger Powell
    • 2
  1. 1.Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UKUK
  2. 2.School of Earth Sciences, The University of Melbourne, Parkville, Victoria 3052, AustraliaAustralia

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