Soil Sampling At Long Valley Caldera Geothermal Area (Klusman & Landress, 1979)

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Exploration Activity: Soil Sampling At Long Valley Caldera Geothermal Area (Klusman & Landress, 1979)

Exploration Activity Details
Location Long Valley Caldera Geothermal Area
Exploration Technique Soil Sampling
Activity Date - 1979

Usefulness useful
DOE-funding Unknown

Exploration Basis
A1-horizon soil samples collected in the vicinity of the resurgent dome and a known geothermal source at Long Valley were analyzed in order to evaluate the application of anomalously high Hg concentration in soils in geothermal exploration and to improve understanding of secondary controls on the Hg content of soils above a known geothermal system
Two primary sets of soil samples were collected, the first using a grid system around the resurgent dome, and the second along nine traverses across three fault systems (five traverses) and across east-west-oriented gullies (four traverses) to evaluate the importance of aspect. The samples were analyzed for their Hg contents, as well as for pH, hydrous Fe and Mn, and organic carbon, all of which are known to have influence on Hg retention in soils. The data compiled for these secondary parameters and the field-determined parameters of geology, soil development, A0-horizon thickness, and aspect were then analyzed using various statistical methods. Samples from the resurgent dome were statistically different from those collected in Long Valley proper with respect to Hg, organic carbon, and pH, suggesting that secondary influences may place important controls on the distribution of Hg in soils across the geothermal field. Organic carbon in the soils was shown to pose the most significant secondary effects on Hg concentration. For the most part, the secondary controls of Hg are overwhelmed in areas of prominent geothermal activity. Select faults exhibit prominent anomalies in total Hg soil content, indicating that low levels of hydrothermal activity or effective sealing of faults to gas leakage may occur in some locations.


Additional References