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Table 6 Bulk volatile contents of magmas and amounts of degassed magma estimated from the chemical composition of the volcanic gas, emission rate of SO2, and volatile content of the melt inclusions and the groundmass

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

Magma Volcanic gasa Bulk volatile content of magmab Averaged emission rate of sulfur in 2014–2017c Degassing rate Magma degassed in 2014–2017d Tephra in 2014–2016e Magma degassed in 1979–2017f
CO2/SO2 H2O/SO2 Degassed magma Magma before degassing
H2O CO2 S H2O CO2 S Mass Volume Mass Volume Mass Volume
(mol mol−1) (mol mol−1) (wt%) (wt%) (wt%) (wt%) (wt%) (wt%) (kg s−1) (103 kg s−1) (109 kg) (109m3 DRE) (109 kg) (109m3 DRE) (109 kg) (109m3 DRE)
A1 1 25 0.12 0 0.004 1 0.09 0.07 8.7 (± 7.2) 13 1700 0.62 2.8 0.0010 3000 1.1
A2       2 0.18 0.14   6.4 810 0.30    1400 0.53
A3       0.5 0.04 0.03   33 4200 1.6    7500 2.8
B1 10 45     1 0.5 0.04   24 3000 1.1    5400 2.0
B2       2 1 0.08   11 1400 0.53    2600 0.96
B3       0.5 0.2 0.02   54 6900 2.5    12,000 4.5
  1. Detail information on time of eruptions and SO2 emission rates as follows: The 1979 eruption series started in June 13, 1979, and continued until December 1979 (Kyoto Univ 1980), accompanied by intense SO2 emission (12 kg s−1 in September and 30 kg s−1 in November; Kyushu Univ 1980). The 1989 eruption started in June and continued until February 1991 (Kyoto Univ 1992; Ikebe et al. 2008), and the emission rate of SO2 was more than 12 kg s−1 during most of that period (Kyushu Univ 1990, 2004). In the periods from December 1992 to February 1993 and from July 2003 to January 2004, a large SO2 emission rate of more than 12 kg s−1 was observed (Kyushu Univ 2004)
  2. aChemical composition of the volcanic gas emitted from Nakadake crater on January 12, 2015, from GSJ (2015a)
  3. bWater and sulfur content of degassed magma (0.12 wt% H2O and 0.004 wt% S) was calculated from average water content of the groundmass glass (0.2 wt%) and average sulfur content of the groundmass bulk (0.006 wt%) in the 2014 scoria (Table 4) and content of groundmass in the scoria (60 wt%)
  4. cThe average and one standard deviation (in parenthesis) of emission rate of sulfur was calculated from averaged SO2 flux of 157 observations in January 2014–December 2017 (1500 ± 1250 t d−1 SO2; JMA 2018b), assuming that all sulfur in volcanic gas is SO2
  5. dMass of the degassed magma was calculated for the periods from January 2014 to December 2017. The volume (m3 DRE) was calculated from the mass, assuming a rock density of 2700 kg m−3
  6. eMass of tephra in 2014–2016 was calculated from mass of tephra from November 25, 2014, to May 11, 2015 (2.1 × 109 kg; Kumamoto Univ 2015a), that of tephra on September 14, 2015, eruption (4 × 107 kg; Kumamoto Univ 2015b) and that of October 8, 2016, eruption (6.3 × 108 kg; Kumamoto Univ et al. 2016). The volume was calculated using a rock density of 2700 kg m−3. Assuming all component of the tephra is essential, mass and volume of the tephra are equal to maximum estimates of the erupted magma
  7. fVolume of the degassed magma in 1979–2017 was calculated from the 0.09–0.37 × 109 m3 DRE the periods from June to December in 1979, 0.27–1.1 × 109 m3 DRE from June 1989 to February 1991, 0.27–1.1 × 109 m3 DRE from December 1992 to February 1993, 0.09–0.37 × 109 m3 DRE from July 2003 to January and 0.62–2.5 × 109 m3 DRE from January 2014 to December 2017. The volume of the degassed magma from June to December 1979 is more than 20 times larger than that of total tephra produced by the 1979 eruptions (0.0035 × 109 m3 DRE; Kyoto Univ 1980; Ono and Watanabe 1985)