Hydrothermal alteration of basalts from Hawaii Geothermal Project Well-A, Kilauea, Hawaii
Mineralogical examination of basaltic rocks obtained during drilling of a successful 1,962-m-deep geothermal well (HGP-A) in the east rift zone of Kilauea Volcano, Hawaii, reveals three zones of hydrothermal alteration beneath a zone of unaltered lavas. Each alteration zone is characterized by the dominance of a particular mineral: zone 1, montmorillonite; zone 2, chlorite; zone 3, actinolite. Three zones of relative permeability can be tentatively identified on the basis of filled versus partly filled vesicles and fractures. Because the well has not returned to thermal equilibrium as of this writing, stability relations between secondary minerals and temperatures cannot be calculated with accuracy. However, the latest downhole temperatures measured at the boundaries of alteration zones, compared with similar data from high-temperature geothermal areas in Iceland, indicate that HGP-A temperatures are considerably higher than those encountered for the same alteration-zone boundaries in Icelandic wells. This indicates that the present-day thermal regime in HGP-A is relatively young and that the hydrothermal minerals probably have not reached equilibrium with existing conditions.
- Research Organization:
- Hawaii Inst. of Geophysics, Honolulu
- OSTI ID:
- 6723160
- Journal Information:
- Geology; (United States), Vol. 6:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BASALT
HYDROTHERMAL ALTERATION
KILAUEA VOLCANO
GEOTHERMAL WELLS
MINERALOGY
AMPHIBOLE
CHLORITE MINERALS
HAWAII
LAVA
MONTMORILLONITE
PERMEABILITY
RIFT ZONES
STABILITY
TEMPERATURE MEASUREMENT
VOLCANOES
WELL DRILLING
ZONES
CLAYS
DRILLING
GEOLOGIC STRUCTURES
IGNEOUS ROCKS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MINERALS
NORTH AMERICA
ROCKS
USA
VOLCANIC ROCKS
WELLS
WESTERN REGION
152003* - Geothermal Data & Theory- Rock-Water-Gas Interactions
150201 - Geology & Hydrology of Geothermal Systems- USA- (-1989)