GSJ Open-file Report no.534

Contour maps of some useful petrological parameters on P-T plane: A case of Hijiori volcano, NE Japan

by Isoji MIAYGI (GSJ)

Hijiori volcano (N38 36'35'', E140 9'20'') is a small caldera with approximately 2 km in diameter erupted at about 12 ky (Miyagi, 2004) on the place where no volcanic body had existed before. To understand how a new felsic volcano commences the activity, the magma process of Hijiori volcano is studied (and reported elsewhere). Here I report some useful petrological parameters for bulk rock composition of the essential ejecta (Table 1).

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表 1:
Chemical composition of the starting material.
(a representative bulk rock composition of
Hijiori stage 3-3a pumice, Miyagi (2007))

Sample ID	Hj_j-Q
Loc. N	38 39'24.8''
Loc. E	140 12'19.3''
SiO₂	60.71
TiO₂	0.71
Al₂O₃	15.85
tFeO	6.6
MnO	0.11
MgO	3.9
CaO	6.62
Na₂O	3.03
K₂O	1.28
P₂O₅	0.12
Total	98.93

All the analytical figures are described in wt.%.

The parameters include the amount and chemical compositions of minerals and melt in equilibrium at some P, T, fO₂, and H₂O concentrations. These parameters were obtained using the MELTS program (Asimow and Ghiorso, 1998; Ghiorso and Sack, 1995) over the range of pressure from 1 atmosphere to 16 k bar with 0.1 k bar step, temperature from 700 to 1400 deg-C with 1 deg-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. Since the MELTS program outputs huge quantities of numerical values (combination of P, T, H₂O, and fO₂ is about 4.7 million), I summarized them into a suite of contour maps on pressure-temperature plane using the GMT program (Wessel and Smith, 1998), and htmlized them cross-linked to develop a convenient tool.

This research project has been conducted under the research contract with Nuclear and Industrial Safety Agency (NISA).

An example of citation:

Miaygi (2011) Contour maps of some useful petrological parameters on P-T plane: A case of Hijiori volcano, NE Japan. Open File Report of GSJ, no.534, Geological Survey of Japan, AIST.

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.
Miyagi, I., 2004. On the eruption age of the hijiori caldera, based on more accurate and reliable radiocarbon data. Bull. Volcanol. Soc. Japan 49 (4), 201-205.
Miyagi, I., 2007. Stratigraphy and volcanic activities of hijiori volcano, northeastern japan arc. Bull. Volcanol. Soc. Japan 52 (6), 311-333 (in Japanese with English abstract).
Wessel, P., Smith, W., 1998. New, improved version of generic mapping tools released. EOS Trans. Amer. Geophys. U. 79 (47), 579.

If you have questions about this page, contact Isoji MIYAGI