Oxygen buffering of Kilauea volcanic gases and the oxygen fugacity of Kilauea basalt

Journal Article · Mon Feb 01 00:00:00 EST 1993 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(93)90169-W· OSTI ID:6648149

Gerlach, T M ^[1]

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1. Geological Survey, Vancouver, WA (United States)

Volcanic gases collected during episode 1 of the Puu Oo eruption along the east rift zone of Kilauea Volcano, Hawaii, have uniform C-O-H-S-Cl-F compositions that are sharply depleted in CO[sub 2]. The CO[sub 2]-poor gases are typical of Type II volcanic gases (GERLACH and GRAEBER, 1985) and were emitted from evolved magma stored for a prolonged period of time in the east rift zone after releasing CO[sub 2]-rich gases during an earlier period of temporary residence in the summit magma chamber. The samples are remarkably free of contamination by atmospheric gases and meteoric water. Thermodynamic evaluation of the analytical data shows that the episode 1 gases have equilibrium compositions appropriate for temperatures between 935 and 1032[degrees]C. Open- and closed-system equilibrium models of species distributions for the episode 1 gases show unequivocally that coexisting lavas buffered the gas oxygen fugacities during cooling. These models indicate that the F[sub o[sub 2]] buffering process occurs by transfer of oxygen from the major species in the gas phase (H[sub 2]O, CO[sub 2], SO[sub 2]) to the lava during cooling and that the transfer of oxygen also controls the fugacities of several minor and trace species (H[sub 2], CO, H[sub 2]S, S[sub 2], Cl[sub 2], F[sub 2]), in addition to O[sub 2] during cooling. Gas/lava exchanges of other components are apparently insignificant and exert little influence, compared to oxygen exchange, during cooling. Oxygen transfer during cooling is variable, presumably reflecting short-term fluctuations in gas flow rates. Higher flow rates restrict the time available for gas/lava oxygen transfer and result in gases with higher equilibrium temperatures. Kilauea basalt either arrives in the crust with an oxygen fugacity between NNO and FMQ, or it develops an oxygen fugacity in this range immediately upon arrival in the summit chamber.

• OSTI ID: 6648149
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 57:4; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
OXYGEN
PRESSURE MEASUREMENT
VOLCANIC GASES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
BASALT
BUFFERS
CONTAMINATION
COOLING
EQUILIBRIUM
ERUPTION
FLUCTUATIONS
GAS FLOW
HAWAII
KILAUEA VOLCANO
LAVA
MAGMA
METEORIC WATER
RANGE
DEVELOPED COUNTRIES
ELEMENTS
FLUID FLOW
FLUIDS
GASES
GROUND WATER
HYDROGEN COMPOUNDS
IGNEOUS ROCKS
NONMETALS
NORTH AMERICA
OXYGEN COMPOUNDS
ROCKS
USA
VARIATIONS
VOLCANIC ROCKS
VOLCANOES
WATER
580000* - Geosciences