By Yousif K. Kharaka, James J. Thordsen and Lloyd D. White
The full report is available in pdf. Links to the pdf.
An intensive hydrogeologic investigation, mandated by U.S. Congress and centered on the Norris-Mammoth corridor was conducted by USGS and other scientists during 1988-90 to determine the effects of using thermal water from a private well located in the Corwin Springs Known Geothermal Resources Area, Montana, on the thermal springs of Yellowstone National Park (YNP), especially Mammoth Hot Springs. As part of this investigation, we carried out a detailed study of the isotopic and chemical compositions of meteoric water from cold springs and wells, of thermal water, especially from the Norris-Mammoth corridor and of snow. Additional sampling of meteoric and thermal waters from YNP and surrounding region in northwest Wyoming, southwest Montana and southeast Idaho was carried out in 1991-92 to characterize the distribution of water isotopes in this mountainous region and to determine the origin and possible recharge locations of thermal waters in and adjacent to the Park.
The 
D and 18O
values for 40 snow samples range from –88 to –178‰ and –12.5
to –23.9‰, respectively, and define a well constrained line given by D
= 8.2 18O + 14.7 (r2
= 0.99) that is nearly identical to the Global Meteoric Water Line. The D
and 18O values of 173 cold water
samples range from –115 to –153‰ and –15.2 to –20.2‰, respectively,
and exhibit a similar relationship although with more scatter and with some
shift to heavier isotopes, most likely due to evaporation effects. The spatial
distribution of cold-water isotopes shows a roughly circular pattern with isotopically
lightest waters centered on the mountains and high plateau in the northwest
corner of Yellowstone National Park and becoming heavier in all directions.
The temperature effect due to altitude is the dominant control on stable water
isotopes throughout the region; however, this effect is obscured in narrow 'canyons'
and areas of high topographic relief. The effects due to distance (i.e. "continental")
and latitude on water isotopes probably are relatively minor and difficult to
resolve from the major controls. The data indicate that the groundwater are
derived predominantly from cold, isotopically light winter precipitation, and
that the isotope values of groundwater from elevations above about 2.5-3.0 km
in the Gallatin and northern Absaroka Ranges are light enough (The D
–149‰) to be the presumed recharge water
for the hydrothermal system in the Park. However, estimation of the present-day
volume of this recharged, isotopically light water indicates that it is not
adequate to supply the high (3-4 m3/s) thermal water discharges from
YNP, and cooler temperatures at the time of recharge would be required. The
volume of meteoric water with D values lighter
than –145‰ may be adequate for recharging the hydrothermal system, and this
may be a more plausible value than the –149‰ originally calculated from
data that are subject to moderate uncertainties.
ABSTRACT
INTRODUCTION
Description of Study Area
Regional Geology
Climate
METHODS AND PROCEDURES
Snow Samples
Field Procedures
Laboratory Measurement
Water Isotopes
RESULTS AND DISCUSSION
Chemical Composition of Cold Water and Snow
Isotope Composition of Cold Water and Snow
Controls on Cold Water Isotopes
Hydrothermal Fluid Discharges
Thermal Water and Gas Compositions
Origin and Evolution of Thermal Fluids
Hydrothermal fluids from the Mammoth system
CONCLUSIONS
ACKNOWLEDGEMENTS
REFERENCES
CITED
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Yousif K. Kharaka
U.S. Geological Survey
345 Middlefield Road, MS 427
Menlo Park, CA 94025
Email: ykharaka@usgs.gov
U.S. Geological Survey
Information Services
Building 810
Box 25286 Federal Center
Denver, CO 80225
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