Composition of some components in gas collected during the 1977 eruption at Kilauea, Hawaii

Journal of Volcanology and Geothermal Research, 7 (1980) 319--322

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© Elsevier Scientific Publishing Company, Amsterdam -- Printed in Belgium

COMPOSITION OF SOME COMPONENTS IN GAS COLLECTED DURING THE 1977 ERUPTION AT KILAUEA, HAWAII

J O H N J. N A U G H T O N

Chemistry Department and Hawaii Institute of Geophysics, University of Hawaii, Honolulu, HI 96822 (U.S.A.) (Received August 25, 1978; revised and accepted March 28, 1979)

ABSTRACT Naughton, J.J., 1980. Composition of some components in gas collected during the 1977 eruption at Kilauea, Hawaii. J. Volcanol. Geotherm. Res., 7: 319--322. Gas and condensate samples were collected from a site along the primary fissure zone of the September, 1977, eruption on the SE rift o f Kilauea volcano, Hawaii. The gas samples showed a reduced composition that was little affected by contaminant air, and was comparable with collections made from other high-temperature Hawaiian volcanic sites. The condensate was characterized by a comparatively high content of fluoride and chloride in an acid medium. INTRODUCTION

An understanding of the important role of the gaseous c o m p o n e n t in volcanic eruptions has been limited by the few collections that have been made. This paucity of collections has been due mainly to the lack of accessibility and the very real danger at eruption sites. Recently, however, an unexpected o p p o r t u n i t y for such a collection was made possible during the September 13--30, 1977, flank eruption at Kilauea. Physical, geological and temporal details of the eruption are available in Moore et al. (1979). SAMPLING AND ANALYSIS

The samples were taken on September 19 along the main eruption fissure. At the time of sampling the only eruption center was about 100 m away from the collection site, and spatter was being ejected to a height of about 20 m. Collections were made through a well-seasoned stainless steel tube 5 mm in diameter and approximately 4 m long. This was inserted about one meter into the incandescent zone (~900°C) of the small rift fissure along which there was a visible emission of gas but no evidence of concurrent lava spattering. The tube led to a condensate collection bottle, and then through a Y-tube to a hand-operated pump and to an evacuated stainless steel sampling tube with a teflon-seated stainless steel close-off valve. This tube was

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partially filled with activated silica gel. The collecting tube and condensate bottle were purged b y pumping, and thereby heated to such a degree that no condensation occurred within the tube. After this the sampling tube valve was opened to receive the gas sample. In the laboratory the gas was analyzed b y gas chromatography, with the results shown in Table 1. The condensate was analyzed with atomic absorption spectrometry and with specific ion electrodes. Collected water was not determined. This was believed to be diluted b y meteoric sources in the high rainfall region of the eruption, so no meaningful analysis could be made in any a t t e m p t to measure the volcanic contribution of this component. Helium was of particular interest since it has been found in relatively high concentrations in certain fumaroles around Kilauea. It was separated b y gas chromatography and measured by means of a small mass spectrometer specifically sensitive to this gas. RESULTS

The sample analyses are listed in Table 1, and have been reduced to a common basis for comparison of the active gases b y the elimination o f components contributed b y atmospheric contamination with the results shown in Table 2. Details of the c o m p u t a t i o n methods used to calculate the equilibriTABLE 1 C o m p o s i t i o n o f t h e a n a l y z e d p o r t i o n s o f the gas samples c o l l e c t e d f r o m S e p t e m b e r 1977 f l a n k e r u p t i o n o f K i l a u e a n e a r K a l a p a n a . Samples w e r e c o l l e c t e d o n S e p t e m b e r 19 f r o m a fissure o n t h e line o f the e r u p t i o n rift Gas c o m p o s i t i o n ~ (vol. or tool.%)

Sample

1 2

(1977) (1977)

He 2

~

N2

02

CO2

SOs

0 . 9 5 × 10 -4 3.5 × 10 -4

1.4 2.2

73.5 70.9

4.2 0.29

19.9 25.9

1.0 0.78

Condensate composition (~g/ml)

(1) 3 (2) 4

pH

Na

K

Ca

Mg

Cu

F

CI

1.50 2.07

4.6 0.43

2.8 4.5

1.6 0.30

3.3 0.11

0.89 nil

280 2.2

340 20

1 Also a n a l y z e d , b u t not detected - - 0 . 0 0 3 > H2S, CH 4 ; 0 . 0 2 > C O - - w i t h p e r c e n t detec.tion limits indicated. 2 H e l i u m c o n t e n t c o r r e c t e d for atmospheric helium based o n N 2 c o n t e n t . All N~ a n d 02 is assumed to b e derived f r o m i n f i l t r a t e d air. 3 C o m b i n e d c o n d e n s a t e f r o m s a m p l e s 1 a n d 2. 4 C o n d e n s a t e f r o m t h e p e r s i s t e n t f u m a r o l e , S u l p h u r B a n k , near the Kilauea caidera rim. Collected o n S e p t e m b e r 20, 1977.

321 TABLE2 Composition of active gases in September 1977 Kilauea gas samples recalculated to an air-free condition. 1 Comparison is made to calculated equilibrium compositions. Also listed are compositions of other gas collections made in Hawaii from high-temperature vents (above - 800°C) Sample

1 (1977) 2 (1977) Calc. reduced 3, 900 ° C Calc. oxidized 3, 900°C KI-F (Heald et al., 1963) IR 4 (Naughton et al., 1969) MU-2 (Naugton, 1973)

Composition (vol. %) H2

CO 2

SO:

air 2 (%)

6.5 7.6 3.3 5.9 x 10 -14 4.9 -32.4

89.0 89.7 77.4 99.99 82.4 80 67.5

4.6 2.7 19.4 9.3 x l 0 -3 12.7 20 0

77.6 71.2 -50 99 -96

1"Air-free": all N2 , 02 and water eliminated in calculation of composition. 2 Calculated from sum of 02 and N2 in original collection. 3"Reduced" refers to the calculated composition at a condition of equilibrium with Hawaiian lava, with an oxygen partial pressure (fugacity) equal to 5 × 10 -11 atm at 900°C. "Oxidized" refers to the calculated composition for a mixture with atmospheric oxygen, with the oxygen content assumed to be reduced to about 10% by dilution of the total gas by the predominant water vapor and other gases in the fume. 4 "IR": measurements made by adsorption of infrared radiation from the lava fountain by the gaseous components released during fountaining. u m c o n c e n t r a t i o n o f the m o l e c u l a r c o m p o n e n t s in a h i g h - t e m p e r a t u r e a t o m i c m i x t u r e o f volcanic c o m p o s i t i o n are given b y N a u g h t o n et al. (1974). T h e analyses results m o r e closely resemble t h o s e calculated f o r a " r e d u c e d " c o n d i t i o n (Table 2) t h a n t h o s e e x p e c t e d for the " o x i d i z e d " c o n d i t i o n t h a t w o u l d b e p r e d i c t e d f r o m the high air c o n t e n t . This w o u l d indicate t h a t air e n t e r e d in the u p p e r reaches o f t h e sampling site o r during c o l l e c t i o n and did n o t achieve e q u i l i b r i u m b e f o r e being q u e n c h e d b y the sampling p r o c e d u r e . S o m e h y d r o g e n m a y have b e e n p r o d u c e d b y r e a c t i o n o f w a t e r with the stainless steel t u b e inserted i n t o the vent, b u t this is believed t o be u n l i k e l y because the t u b e was " w e l l - s e a s o n e d " and h a d been used in o t h e r c o l l e c t i o n s and equilibrated b y t h e pre-sampling p u m p - t h r o u g h , and thus was p r o t e c t e d b y a c o a t i n g o f r e a c t i o n p r o d u c t s . Sigvaldason a n d Elisson ( 1 9 6 8 ) have discussed this process for such collecting proced.ures. T h e stainless steel sampling t u b e s used t o c o n t a i n and t r a n s p o r t t h e samples s h o w e d n o evidence o f react i o n with t h e gases as j u d g e d b y t h e u n b l e m i s h e d polish o f t h e interior surfaces w i t h no i n d i c a t i o n o f t h e r e a c t i o n p r o d u c t s n o r m a l l y f o u n d . This also has been f o u n d t o be t r u e in previous use of these tubes f o r h i g h - t e m p e r a t u r e collections. O u r e x p e r i e n c e has b e e n t h a t t h e reactive gases (sulfur and halogen c o m p o u n d s ) are i m m o b i l i z e d b y the a c t i v a t e d silica gel in t h e tubes. The high c o n t e n t o f N2 relative t o 02 for t h e samples (Table 1), w h e n c o m p a r e d to air, is f o u n d f r e q u e n t l y in o u r e x p e r i e n c e in Hawaii (Heald et al., 1 9 6 3 )

322 and is ascribed to some consumption of air O2 by oxidation of reduced species in the lava (Fe 2÷) or in the gas (H2, CH4, CO, H2S). The sulfur content (SO~) of gases has been found to be highly variable even from a single vent, and may be related to the time since the onset of eruption (Naughton et al., 1975), so the differences between these results and those from other sampled vents are not surprising. Save for this SO2 variation, the air free composition is within the range of other high-temperature collections made in Hawaii (Table 2). The high content of halogens in the condensate is noteworthy (Table 1). ACKNOWLEDGEMENTS I express appreciation to the staff of the Hawaiian Volcano Observatory, U.S. Geological Survey, who provided help in the hasty assembling of equipment for the impromptu collections and the helicopter transportation to the inaccessible eruption area. One member, H. Protska, provided most essential aid during the collection. Gases were analyzed by D. Thomas and G. Powell, and the condensate by V.A. Greenberg, all of the Hawaii Institute of Geophysics, whose help I gratefully acknowledge. Support was received from the Hawaii Natural Energy Institute. Contribution number 1037 of the Hawaii Institute of Geophysics, University of Hawaii at Manoa, 2525 Correa Rd., Honolulu, Hawaii.

REFERENCES Heald, E.F., Naughton, J.J. and Barnes, I.L., 1963. The use of e~_~ilibrium calculations in the interpretation of volcanic gm samples. J. Geophys. Res., 68: 545--557. Moore, R.B., Dzurisin, D., Eaton, G.P., Koyanagi, R.Y., Lipman, P., Lockwood, J., Puniwai, G.S. and Helz, R.T., 1979. The 1977 eruption of Kilauea volcano, Hawaii. In: Abstract Volume: Hawaii Symposium on Intraplate and Submarine Volcanism. Hilo, Hawaii, p. 171. Naughton, J.J., 1973. Volcanic flame: source of fuel and relation to volcanic gas-lava equilibrium. Geochim. Cosmochim. Acta, 37: 1163--1169. Naughton, J.J., Derby, J.V. and Glover, R.B., 1969. Infrared me~urements on volcanic gas and fume: Kilauea eruption, 1968. J. Geophys. Ru., 74: 3273--3277. Naughton, J.J., Finlayson, J.B. and Lewis, V.A., 1975. Some results from recent chemical studies at Kilaues volcano, Hawaii. Bull Volcanol., 39: 64--69. Naughton, J.J., Lewis, V.A., Hammond, D. and Nishimoto, D., 1974. The chemistry of sublimates collected directly from lava fountains at Kilauea volcano, Hawaii. Geochim.

Cosmochim. Actaj38: 1679--1690. Sigvaldason, G.E. and Eli~on, G., 1968. Collection and analysis of volcanic gases at Surtsey, Iceland. Geochim. Cosmochim. Acta, 32: 797--805.