Volcanic Gases

CONDOR – Applications

Extensive research demonstrates that terrestrial volcanic gases clearly apporach chemical equilibrium (Symonds et al. 1994). The Kilauea volcano on the big island of Hawaii is probably the best studied volcano in the world, and volcanic gas collections date back to the pioneering work by Day, Jaggar, and Shepard during 1912-1919. During this period, there was a lava lake in the Halemaumau crater at Kilauea’s summit. Some of the best (i.e., least contaminated by air, pyrolyzed vegetation, and/ or meteoric water) volcanic gas samples are the “J-series” collected by Jaggar in March 1918 and March 1919 from several sites around the lava lake. Below are some comparisons of Jaggar’s collected samples with calculated equilibrium compositions from the CONDOR code and with equilibrium calculations by Gerlach (1980). All analyses of Jaggar’s samples were corrected by Gerlach (1980) by removal of N2 and Ar and conversion of reported Cl2 to HCl.

Gerlach’s equilibrium calculations also involve a restoration procedure, which alters the gas composition. This procedure is described in his papers. No restoration step is done in the CONDOR code calculations which have the same bulk elemental abundances as Jaggar’s samples listed in Gerlach’s Table 1.


Sample J8 (25 March 1918)
Halemaumau lava lake, Kilauea volcano, Hawaii

Volume %
Gas CONDOR* Sample J8 Gerlach (1980)*
CO 1.46 1.50 1.51
CO2 48.96 48.91 48.90
H2 0.47 0.49 0.49
H2O 37.10 37.11 37.09
SO2 11.85 11.87 11.84
S2 0.02 0.04 0.02
HCl 0.08 0.08 0.08
H2S 0.03 0.04
*Calculated for 1170 ºC and 1 atmosphere.


Sample J11 (13 March 1919)
Halemaumau lava lake, Kilauea volcano, Hawaii

Volume %
Gas CONDOR* Sample J11 Gerlach (1980)*
CO 0.54 0.62 1.03
CO2 21.95 21.89 36.69
H2 0.76 0.33 0.55
H2O 63.77 64.38 40.14
SO2 12.75 12.52 21.06
S2 0.06 0.26 0.25
H2S 0.13 0.20
*Calculated for 1100 ºC and 1 atmosphere.


Sample J13 (15 March 1919)
Halemaumau lava lake, Kilauea volcano, Hawaii

Volume %
Gas CONDOR* Sample J13 Gerlach (1980)*
CO 0.59 0.60 0.62
CO2 17.55 17.54 17.82
H2 1.00 0.99 1.01
H2O 69.78 69.84 69.29
SO2 10.76 10.73 10.93
S2 0.02 0.09 0.03
HCl 0.21 0.21 0.21
H2S 0.07 0.08
*Calculated for 1175 ºC and 1 atmosphere.


References

  1. Gerlach, T. M. 1980. Evaluation of volcanic gas analyses from Kilauea volcano. J. Volcanol. Geotherm. Res. 7, 295-317.
  2. R. B. Symonds et al. 1994. Volcanic gas studies: Methods, results, and applications. In Volatiles in Magmas (M. R. Carroll and J. R. Holloway, Eds.), pp. 1-66, Mineralogical Society of America, Washington, D. C.