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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. B1, 2028, doi:10.1029/2001JB001594, 2003

Mixing of magmatic volatiles with groundwater and interaction with basalt on the summit of Kilauea Volcano, Hawaii

Shaul Hurwitz

U.S. Geological Survey, Menlo Park, California, USA


Fraser Goff

Geology/Geochemistry Group, Los Alamos National Laboratory, Los Alamos, New Mexico, USA


Cathy J. Janik

U.S. Geological Survey, Menlo Park, California, USA


William C. Evans

U.S. Geological Survey, Menlo Park, California, USA


Dale A. Counce

Geology/Geochemistry Group, Los Alamos National Laboratory, Los Alamos, New Mexico, USA


Michael L. Sorey

U.S. Geological Survey, Menlo Park, California, USA


Steven E. Ingebritsen

U.S. Geological Survey, Menlo Park, California, USA


Abstract

We interpret new chemical and isotopic data from samples collected between October 1998 and March 2002 from the NSF well (also called the Keller well), the only deep well on the summit of Kilauea Volcano, Hawaii. Sample collection followed cleaning of the well, which renewed access to the hydrothermal system very close to the loci of magmatic and fumarolic activity. The chemical and isotopic compositions of the new samples differ remarkably from data published previously. On the basis of the S/Cl ratio and carbon and helium isotopes we conclude that the thermal fluids formed by condensation of magmatic gas into shallow meteoric groundwater. Gas condensation was followed by a complex pattern of basalt dissolution accompanied by an increase of fluid pH and precipitation of secondary minerals. Geochemical modeling and geothermometry imply that the fluids equilibrated with an assemblage of secondary minerals at temperatures between 90 and 140°C. The significantly different chemical composition of the NSF well fluids from that of springs along the southern coast of the island indicates that mass transport from the summit region toward the lower flanks of the volcano is limited.

Published 18 January 2003.

Index Terms: 1040 Geochemistry: Isotopic composition/chemistry; 1832 Hydrology: Groundwater transport; 1829 Hydrology: Groundwater hydrology; 8424 Volcanology: Hydrothermal systems (8135).

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 417277 bytes)

Citation: Hurwitz, S., F. Goff, C. J. Janik, W. C. Evans, D. A. Counce, M. L. Sorey, and S. E. Ingebritsen (2003), Mixing of magmatic volatiles with groundwater and interaction with basalt on the summit of Kilauea Volcano, Hawaii, J. Geophys. Res., 108(B1), 2028, doi:10.1029/2001JB001594.