Contributions to Mineralogy and Petrology

, Volume 110, Issue 2–3, pp 304–310 | Cite as

Amphibole composition in tonalite as a function of pressure: an experimental calibration of the Al-in-hornblende barometer

  • Max W. Schmidt


The Al-in-hornblende barometer, which correlates Altot content of magmatic hornblende linearly with crystallization pressure of intrusion (Hammarstrom and Zen 1986), has been calibrated experimentally under water-saturated conditions at pressures of 2.5–13 kbar and temperatures of 700–655°C. Equilibration of the assemblage hornlende-biotite-plagioclase-orthoclasequartz-sphene-Fe-Ti-oxide-melt-vapor from a natural tonalite 15–20° above its wet solidus results in hornblende compositions which can be fit by the equation: P(±0.6 kbar) = −3.01 + 4.76 Al hbl tot r2=0.99, where Altot is the total Al content of hornblende in atoms per formula unit (apfu). Altot increase with pressure can be ascribed mainly to a tschermak-exchange (\(t\vec k,{\text{ Mg}}_{{\text{ - 1 }}} {\text{Al}}^{{\text{VI}}} {\text{Si}}_{{\text{ - 1}}} {\text{ Al}}^{{\text{IV}}}\)) accompanied by minor plagioclase-substitution (\(\vec pl,{\text{ Ca}}_{{\text{ - 1 }}} {\text{Na}}^{{\text{M(4)}}} {\text{ Al}}_{{\text{ - 1}}}^{{\text{IV}}} {\text{ Si}}\)). This experimental calibration agrees well with empirical field calibrations, wherein pressures are estimated by contact-aureole barometry, confirming that contact-aureole pressures and pressures calculated by the Al-in-hornblende barometer are essentially identical. This calibration is also consistent with the previous experimental calibration by Johnson and Rutherford (1989b) which was accomplished at higher temperatures, stabilizing the required buffer assemblage by use of mixed H2O-CO2 fluids. The latter calibration yields higher Altot content in hornblendes at corresponding pressures, this can be ascribed to increased edenite-exchange (\(\vec ed,{\text{ }}\square _{{\text{ }} - {\text{ }}1}^{ A} {\text{ Na}}^{\text{A}} {\text{Si }}_{ - {\text{ }}1} {\text{Al}}^{{\text{IV}}}\)) at elevated temperatures. The comparison of both experimental calibrations shows the important influence of the fluid composition, which affects the solidus temperature, on equilibration of hornblende in the buffering phase assemblage.


Solidus Temperature Experimental Calibration Fluid Composition Phase Assemblage Crystallization Pressure 
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.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Apted MJ, Liou JG (1983) Phase relations among greeschist, epidote-amphibolite, and amphibolite in a basaltic system. Am J Sci 283-A:328–354Google Scholar
  2. Blundy JD, Holland TJB (1990) Calcic amphibole equilibria and a new amphibole-plagioclase geothermometer. Contrib Mineral Petrol 104:208–224Google Scholar
  3. Bohlen SR, Boettcher AL, Wall VJ (1982) The system albite-H2O-CO2: a model for melting and activities of water at high pressures. Am Mineral 67:451–462Google Scholar
  4. Brown EH (1977) The crossite content of Ca amphibole as a guide to pressure of metamorphism. J Petrol 18:53–77Google Scholar
  5. Clowe CA, Popp RK, Fritz SJ (1988) Experimental investigation of the effect of oxygen fugacity on the ferric-ferrous ratios and unit cell parameters of four natural clinoamphiboles. Am Mineral 73:500–506Google Scholar
  6. Engel AE, Engel CG (1962) Hornblendes formed during progressive metamorphism of amphibolites, Northwest Adirondack Mountains, New York. Geol Soc Am Bull 73:1499–1514Google Scholar
  7. Graham CM, Navrotsky A (1986): Thermochemistry of the tremolite-edenite amphiboles using flourine analogues, and applications to amphibole-plagioclase-quartz equilibria. Contrib Mineral Petrol 93:18–32Google Scholar
  8. Green TH (1982) Anatexis of mafic crust and high pressure crystallization of andesite. In: Thorpe RS (ed) Andesites. Wiley and Sons, pp 465–487Google Scholar
  9. Hammarstrom JM, Zen E-an (1986) Aluminium in hornblende: an empirical igneous geobarometer. Am Mineral 71:1297–1313Google Scholar
  10. Hammarstrom JM, Zen E-an (1992) Discussion of Blundy and Holland's (1990) “Calcic amphibole equilibria and a new amphibole-plagioclase geothermometer”. Contrib Mineral Petrol (in press)Google Scholar
  11. Hays JF, Bell PM (1973) Albite-jadeite-quartz equilibrium: a hydrostatic. determination. Carnegie Inst Washington Year 72:706–708Google Scholar
  12. Holland TJB (1980) The reaction albite=jadeite+quartz determined experimentally in the range 600–1200°C. Am Min 65:214–220Google Scholar
  13. Hollister LS, Grissom GC, Peters EK, Stowell HH, Sisson VB (1987) Confirmation of the empirical correlation of Al in hornblende with pressure of solidification of calc-alkaline plutons. Am Mineral 72:231–239Google Scholar
  14. Huang WL, Wyllie PJ (1986) Phase relationships of gabbro-tonalite-water at 15 kbar with applications to differentiation and anatexis. Am Mineral 71:301–316Google Scholar
  15. Jenkins DM, Newton RC, Goldsmith JR (1985) Relative stability of Fe-free zoisite and clinozoisite. J Geol 93:663–672Google Scholar
  16. Johnson MC, Rutherford MJ (1989a) Experimentally determined conditions in the Fish Canyon tuff, Colorado, magma chamber. J Petrol 30:711–737Google Scholar
  17. Johnson MC, Rutherford MJ (1989b) Experimental calibration of the aluminium-in-hornblende geobarometer with application to Long Valley caldera (California) volcanic rocks. Geology 17:837–841Google Scholar
  18. Johnson MC, Rutherford MJ (1992) Comment to Blundy and Holland's (1990) “Calcic amphibole equilibria and a new amphiboleplagioclase geothermometer”. Contrib Mineral Petrol (in press)Google Scholar
  19. Lambert IB, Wyllie PJ (1974) Melting of tonalite and crystallization of andesite liquid with excess water to 30 kbars. J Geol 82:88–97Google Scholar
  20. Leake BE (1978) Nomenclature of amphiboles. Can Mineral 16:501–520Google Scholar
  21. Leistner H (1979) Temperaturgradienten-Messungen in Piston-Zylinder Pressen. Fortschr. Mineral 57:Beih 1, 81–82Google Scholar
  22. Mirwald PW, Getting IC, Kennedy GC (1975) Low-friction cell for piston-cylinder high-pressure apparatus. J Geophys Res 80:1519–1525Google Scholar
  23. Naney MT (1983) Phase equilibria of rock-forming ferromagnesian silicates in granitic systems. Am J Sci 283:993–1033Google Scholar
  24. Piwinskii AJ (1968) Experimental studies of igneous rock series: a zoned pluton in the Wallowa batholith, Oregon. J Geol 76:548–570Google Scholar
  25. Poli S, Schmidt MW (1992) A comment on “Calcic amphibole equibria and a new amphibole-plagioclase geothermometer” by JD Blundy and TJB Holland [Contrib Mineral Petrol (1990) 104:208–224]. Contrib Mineral Petrol (in press)Google Scholar
  26. Pouchou JL, Pichoir F (1984) Un nouveau modèle de calcul pour la microanalyse quantitative par spectrométric de rayon X, partie I: application a l'analyse d'échantillons homogènes. Rech Aéros 3:167–192Google Scholar
  27. Reusser CE (1987) Phasenbeziehungen im Tonalit der Bergeller Intrusion (GR/Schweiz; Provinz Sondrio/Italien). Unpubl Diss. No 8329, ETH ZürichGoogle Scholar
  28. Shido F, Miyashiro A (1959) Hornblendes of basic metamorphic rocks. J Fac Sci Univ Tokio Sect 2, 12:85–102Google Scholar
  29. Spear FS (1980) NaSi⇌CaAl exchange equilibrium between plagioclase amphibole. Contrib Mineral Petrol 72:33–41Google Scholar
  30. Spear FS (1981a) Amphibole-plagioclase equilibria: an empirical model for the relation albite+trmolite=edenite+quartz. Contrib Mineral Petrol 77:355–364Google Scholar
  31. Spear FS (1981b) An experimental study of hornblende stability and compositional variability in amphibolite. Am J Sci 281:697–734Google Scholar
  32. Swanson SE (1979) The effect of CO2 on phase equilibria and crystal growth in the system Kspar-Ab-An-Q-H2O-CO2. Am J Sci 279:703–720Google Scholar
  33. Thomas WM, Ernst WG (1990) The aluminium content of hornblende in cell-alkaline granitic rocks: a mineralogic barometer calibrated experimentally to 12 kbar. In: RJ Spencer, I-Ming Chou (eds) Fluid-mineral interactions: a tribute to H.P. Eugster. Geochem Soc Spec Pub 2: 59–63Google Scholar
  34. Ulmer P (1982) Geologie und Petrographie des südlichen Adamello. Diplomarbeit No 260, Geol Inst ETH ZürichGoogle Scholar
  35. Whitney JA (1975) The effects of pressure, temperature and \(X_{{\text{H}}_{\text{2}} {\text{O}}}\) on phase assemblage in four synthetic rock compositions. J Geol 83:1–31Google Scholar
  36. Wyllie PJ (1977) Crustal anatexis: an experimental review. Tectonophysics 43:41–71Google Scholar

Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • Max W. Schmidt
    • 1
  1. 1.Institut für Mineralogie und PetrographieETH ZentrumZürichSwitzerland

Personalised recommendations