GSJ Open-file Report no.531

Contour maps of some useful petrological parameters on P-T plane: A case of the eruptive products of the Asama volcano on 1 September 2004

by Isoji MIAYGI (GSJ)

Some useful petrological parameters are summarized for bulk rock composition of the essential ejecta of Asama Volcano on 1 September 2004 (sample ID = pumice 1, Miyake et al., 2005).

The parameters include the amount and chemical compositions of minerals and melt in equilibrium at some P, T, fO₂, and H₂O concentrations. Using the MELTS program (Asimow and Ghiorso, 1998, Ghiorso and Sack, 1995), the petrological parameters were obtained over the range of pressure from 1 atmosphere to 16 k bar with 0.1 k bar step, temperature from 700 to 1400 C with 1 C step, oxygen fugacity FMQ, FMQ+1, FMQ+2 log unit, and water concentration 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0 4.5, 5.0, 6.0, 8.0, and 10 wt.% H₂O (combination of P, T, H₂O, and fO₂ is about 4.7 million).

The obtained numerical values were summarized as a thousand of contour maps on pressure-temperature plane using the GMT program (Wessel and Smith, 1998) and the maps are htmlized and cross-linked.

References:

• Asimow, P., Ghiorso, M., 1998. Algorithmic modifications extending melts to calculate subsolidus phase relations. American Mineralogist 83, 1127–1131.
• Ghiorso, M. S., Sack, R. O., 1995. Chemical mass transfer in magmatic processes iv. a revised and internally consistent thermodynamic model for the interpolation and extrapolation of liquid-solid equilibria in magmatic systems at elevated temperatures and pressures. Contributions to Mineralogy and Petrology 119, 197–212.
• Miyake, Y., Takahashi, K., Tsugane, T., Makino, K., Kakuzen, H., Nishiki, K., Fukui, T., Shinsyu University Research Group for Asama 04 Eruptions, 2005. On the essential ejecta of the september 2004 eruptions of the asama volcano, central japan. Bull. Volcanol. Soc. Japan 50 (5), 333–346.
• Wessel, P., Smith, W., 1998. New, improved version of generic mapping tools released. EOS Trans. Amer. Geophys. U. 79 (47), 579.

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