Petrological characteristics and volatile content of magma of the 1979, 1989, and 2014 eruptions of Nakadake, Aso volcano, Japan

Saito, Genji; Ishizuka, Osamu; Ishizuka, Yoshihiro; Hoshizumi, Hideo; Miyagi, Isoji

doi:10.1186/s40623-018-0970-x

Earth, Planets and Space

Table 5 Representative results of calculations of MELTS, densities, and volumes of bubbles of the magmas. The calculations were done for six types of magmas (A1, A2, A3, B1, B2, and B3) at a temperature of 1079 °C

From: Petrological characteristics and volatile content of magma of the 1979, 1989, and 2014 eruptions of Nakadake, Aso volcano, Japan

Magma	A1	A1	A1	A1	A1	A2	A2	A2	A2	A2	A3	A3	A3	A3	A3
Bulk H₂O (wt%)	1	1	1	1	1	2	2	2	2	2	0.5	0.5	0.5	0.5	0.5
Temperature (°C)	1079	1079	1079	1079	1079	1079	1079	1079	1079	1079	1079	1079	1079	1079	1079
Pressure (MPa)	400	200	100	50	25	400	200	100	50	25	400	200	100	50	25
Phase (vol%)^b
Melt	65.6	72.3	76.9	79.2	80.4	87.0	92.5	96.1	98.2	88.3	48.9	55.5	59.8	62.4	63.7
Plagioclase (An)	17.9 (63)	15.8 (68)	14.1 (71)	13.4 (72)	13.2 (73)	0.2 (74)	0.6 (79)	0.4 (81)	0.2 (82)	7.7 (77)	31.8 (56)	29.0 (60)	26.8 (63)	25.5 (64)	24.9 (65)
Olivine (Fo)	0.0	0.0	0.0	0.2 (73)	0.5 (74)	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Clinopyroxene (Mg#)	15.8 (64)	10.8 (69)	8.0 (71)	6.2 (72)	5.1 (73)	12.8 (67)	6.9 (70)	3.5 (73)	1.6 (73)	3.7 (74)	18.1 (62)	13.8 (67)	11.5 (69)	10.2 (70)	9.6 (71)
Orthopyroxene (Mg#)	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Spinel	0.7	1.0	1.1	1.0	0.9	0.0	0.0	0.0	0.0	0.3	1.3	1.7	1.8	1.8	1.8
Chemical composition of melt (wt%)
SiO₂	57.8	57.4	57.0	56.8	56.7	55.7	55.0	54.6	54.5	55.5	59.7	59.5	59.2	59.0	58.9
TiO₂	1.1	1.0	1.0	1.0	1.0	0.9	0.9	0.9	0.9	1.0	1.3	1.1	1.1	1.1	1.1
Al₂O₃	18.3	17.6	17.3	17.0	16.9	20.0	19.0	18.4	18.2	17.3	17.1	16.5	16.2	16.0	16.0
FeOt	7.7	8.0	8.2	8.3	8.4	8.0	8.5	8.6	8.6	8.8	6.7	7.1	7.3	7.4	7.5
MnO	0.3	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.4	0.3	0.3	0.3	0.3
MgO	1.9	2.6	3.1	3.4	3.4	2.2	3.0	3.5	3.7	3.7	1.5	2.1	2.5	2.7	2.9
CaO	5.7	6.3	6.7	7.0	7.2	6.6	7.6	8.2	8.6	7.7	5.4	5.9	6.2	6.4	6.4
Na₂O	3.6	3.5	3.4	3.4	3.3	3.5	3.3	3.2	3.1	3.2	3.2	3.3	3.4	3.4	3.4
K₂O	3.1	2.8	2.6	2.5	2.5	2.4	2.2	2.1	2.0	2.3	4.1	3.6	3.4	3.2	3.2
P₂O₅	0.5	0.4	0.4	0.4	0.4	0.3	0.3	0.3	0.3	0.3	0.6	0.5	0.5	0.5	0.5
H₂O^c	1.6	1.5	1.3	1.3	1.2	2.4	2.2	2.1	1.9	1.5	1.1	1.0	0.9	0.8	0.8
CO ^c₂	0.146	0.098	0.040	0.015	0.004	0.215	0.113	0.043	0.012	0.001	0.089	0.078	0.039	0.016	0.006
Gas (wt%)^d	0.00	0.04	0.09	0.13	0.20	0.00	0.10	0.19	0.31	1.00	0.00	0.00	0.04	0.06	0.08
H₂O in gas (in mol)^d		0.15	0.24	0.39	0.67		0.27	0.42	0.67	0.90			0.14	0.24	0.43
Volume of bubbles (vol%)^d	0.00	0.13	0.64	1.85	6.67	0.00	0.50	1.81	6.51	33.48	0.00	0.00	0.18	0.60	1.78
Density (kg m⁻³)^d	2696	2632	2586	2531	2400	2623	2536	2458	2320	1704	2743	2692	2662	2633	2594

Magma	B1	B1	B1	B1	B1	B2	B2	B2	B2	B2	B3	B3	B3	B3	B3
Bulk H₂O (wt%)	1	1	1	1	1	2	2	2	2	2	0.5	0.5	0.5	0.5	0.5
Temperature (°C)	1079	1079	1079	1079	1079	1079	1079	1079	1079	1079	1079	1079	1079	1079	1079
Pressure (MPa)	400	200	100	50	25	400	200	100	50	25	400	200	100	50	25
Phase (vol%)^b
Melt	66.3	73.3	78.0	80.3	81.5	87.7	93.9	97.5	99.4	93.1	49.2	56.0	60.4	63.0	64.3
Plagioclase (An)	17.4 (63)	15.2 (68)	13.3 (71)	12.7 (72)	12.5 (73)	0.0	0.0	0.0	0.0	4.7 (78)	31.5 (56)	28.6 (60)	26.4 (63)	25.2 (64)	24.5 (65)
Olivine (Fo)	0.0	0.0	0.0	0.2 (73)	0.4 (74)	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Clinopyroxene (Mg#)	15.5 (63)	10.5 (69)	7.6 (71)	5.8 (72)	4.6 (73)	12.3 (65)	6.1 (70)	2.5 (73)	0.6 (74)	2.0 (72)	18.0 (61)	13.7 (66)	11.4 (69)	10.0 (70)	9.4 (71)
Orthopyroxene (Mg#)	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Spinel	0.8	1.1	1.1	1.0	0.9	0.0	0.0	0.0	0.0	0.2	1.3	1.7	1.8	1.9	1.9
Chemical composition of melt (wt%)
SiO₂	57.8	57.4	57.0	56.8	56.6	55.6	54.8	54.5	54.4	55.0	59.6	59.4	59.2	58.9	58.8
TiO₂	1.1	1.0	1.0	1.0	1.0	1.0	1.0	0.9	0.9	1.0	1.3	1.2	1.1	1.1	1.1
Al₂O₃	18.4	17.7	17.3	17.1	16.9	20.0	19.0	18.4	18.0	17.5	17.2	16.5	16.2	16.1	16.0
FeOt	7.5	7.8	8.0	8.2	8.3	8.0	8.4	8.5	8.5	8.7	6.6	7.0	7.2	7.4	7.4
MnO	0.3	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.4	0.3	0.3	0.3	0.3
MgO	1.9	2.7	3.2	3.4	3.5	2.3	3.1	3.6	3.9	3.9	1.5	2.1	2.5	2.8	2.9
CaO	5.9	6.5	6.8	7.1	7.3	6.8	7.8	8.4	8.8	8.2	5.5	6.0	6.3	6.4	6.5
Na₂O	3.6	3.5	3.4	3.3	3.3	3.5	3.3	3.1	3.0	3.1	3.2	3.3	3.4	3.4	3.4
K₂O	3.1	2.8	2.6	2.5	2.5	2.3	2.1	2.0	2.0	2.1	4.0	3.6	3.4	3.2	3.1
P₂O₅	0.5	0.4	0.4	0.4	0.4	0.3	0.3	0.3	0.3	0.3	0.6	0.5	0.5	0.5	0.5
H₂O^c	1.6	1.4	1.3	1.2	1.0	2.3	2.1	1.9	1.6	1.2	1.1	1.0	0.9	0.8	0.7
CO ^c₂	0.245	0.102	0.043	0.017	0.006	0.289	0.118	0.047	0.017	0.005	0.224	0.093	0.040	0.017	0.007
Gas (wt%)^d	0.59	0.66	0.70	0.77	0.91	0.97	1.10	1.22	1.43	2.04	0.22	0.30	0.34	0.36	0.41
H₂O in gas (in mol)^d	0.11	0.15	0.22	0.35	0.53	0.17	0.24	0.36	0.52	0.69	0.07	0.09	0.14	0.23	0.38
Volume of bubbles (vol%)^d	1.33	2.48	4.74	9.95	22.52	2.97	5.40	10.55	22.60	46.51	0.37	0.86	1.73	3.60	8.33
Density (kg m⁻³)^d	2676	2586	2494	2345	2007	2579	2444	2272	1959	1378	2740	2681	2630	2562	2430

See Additional file 4: Table S3 for detail calculation procedures
FeOt, total FeO
^aBulk CO₂ and S contents of the magmas before degassing are given in Table 6
^bValues in parenthesis show chemical composition of the minerals. An, anorthite content (mol%) in plagioclase (An/(An + Ab) × 100%), Fo, forsterite content (mol%) in olivine, Mg#, Mg/(Mg + Fe) × 100%
^cWater and CO₂ contents of the melt were calculated from the pressure, temperature chemical composition of the melt and the bulk H₂O and CO₂ contents using the solubility model of Papale et al. (2006)
^dGas contents (H₂O + CO₂, wt%) of the fluid (melt and gas) and mol fractions of H₂O in the gases were calculated from the pressure, temperature chemical composition of the melts, and the bulk H₂O and CO₂ contents of the fluids using the solubility model of Papale et al. (2006). The volumes of bubbles were calculated from the masses of H₂O and CO₂ gases exsolved from the melt and densities of H₂O and CO₂ gases that were calculated with Modified Redlich–Kwong equation of state (Holloway 1981) . The densities of the magmas were calculated from the bubble volumes and masses and densities of the melt and crystal calculated by MELTS, assuming that the bubbles do not separate from the magma

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