Volcanic Gases

CONDOR – Applications

Extensive research demonstrates that terrestrial volcanic gases clearly approach 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.