Rapid transport pathways for geothermal fluids in an active Great Basin fault zone

We present an analysis of fault hydraulic architecture, based on >700 spatially distributed ground and geothermal spring temperature measurements taken in an active fault zone. Geostatistical simulations were used to extrapolate the measured data over an 800 × 100 m area and develop a high-resolu...

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Bibliographic Details
Published in:Geology (Boulder) 2004-09, Vol.32 (9), p.825-828
Main Authors: Fairley, Jerry P, Hinds, Jennifer J
Format: Article
Language:English
Subjects:
active faults
Basin and Range Province
Basins
Borax Lake
fault zones
faults
fluid dynamics
geostatistics
Geothermal power
geothermal systems
Great Basin
ground water
Harney County Oregon
heat transfer
hot springs
hydraulic conductivity
Hydrogeology
mapping
measurement
North America
Oregon
permeability
Sediment transport
southeastern Oregon
springs
statistical analysis
Structural geology
temperature
thermal waters
United States
water-rock interaction
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Summary:We present an analysis of fault hydraulic architecture, based on >700 spatially distributed ground and geothermal spring temperature measurements taken in an active fault zone. Geostatistical simulations were used to extrapolate the measured data over an 800 × 100 m area and develop a high-resolution image of temperatures in the fault. On the basis of the modeled temperatures, a simple analytical model of convective heat transport was used to infer a probability distribution function for hydraulic conductivities in a two-dimensional plane parallel to the land surface, and the partitioning of flow between flow paths of different conductivities was calculated as a fraction of the total flux. The analysis demonstrates the existence of spatially discrete, high-permeability flow paths within the predominantly lower-permeability fault materials. Although the existence of fast-flow paths in faults has been hypothesized for >10 yr, their prevalence and contribution to the total flow of fluid in a fault zone are debated. On the basis of our findings, we conclude that the flux transmitted by an individual fast-flow path is significantly greater than that of an average flow path, but the total flux transported in fast-flow paths is a negligible fraction of the total flux transmitted by the fault.
ISSN:0091-7613
1943-2682
DOI:10.1130/G20617.1