Isotopic Analysis- Gas At Long Valley Caldera Geothermal Area (Welhan, Et Al., 1988)

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Exploration Activity: Isotopic Analysis- Gas At Long Valley Caldera Geothermal Area (Welhan, Et Al., 1988)

Exploration Activity Details
Location Long Valley Caldera Geothermal Area
Exploration Technique Isotopic Analysis- Fluid
Activity Date 1988 - 1990

Usefulness useful
DOE-funding Unknown

 
Notes
Hot spring waters and steam analyzed for their 3He/4He isotopic contents yielded values that ranged from 4.5 x Ra in the west moat and at Casa Diablo to 6.0-6.5 x Ra in Hot Creek gorge and at Little Hot Creek (Welhan et al., 1988). Significant changes in 3He/4He content were also measured in a fumarole on the north side of Mammoth Mountain from 1989-1990, during which time helium isotope values increased from 3.6 x Ra to 5.5 x Ra from July to October 1989, and then stabilized at 6 x Ra from January to November 1990 (Sorey et al., 1990). This shift exceeds the measured seasonal variation in 3He/4He content, and is suggestive of the addition of magmatic helium to the hydrothermal system. The increase in x Ra coincides with an intense period of seismic activity beneath Mammoth Mountain from May to October 1989 that was accompanied by a magmatic intrusion, as indicated by earthquake hypocenters and deformation data (Hill et al., 1990). These data suggest that recent magmatic activity may contribute to the thermal high beneath the caldera's western margin. Gas isotope data from these and previous studies have been tabulated by Winnett and Janik (1986) and Sorey et al. (1993), and are discussed in comparison with gas isotope data from the [Yellowstone Caldera Geothermal Region

 
References

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Additional References