Geothermal investigations in Idaho. Part 1. Geochemistry and geologic setting of selected thermal waters

Abstract

At least 380 hot springs and wells are known to occur throughout the central and southern parts of Idaho. One hundred twenty-four of these were inventoried as a part of the study reported on herein. At the spring vents and wells visited, the thermal waters flow from rocks ranging in age from Precambrian to Holocene and from a wide range of rock types-igneous, metamorphic, and both consolidated and unconsolidated sediments. Twenty-eight of the sites visited occur on or near fault zones while a greater number were thought to be related to faulting. Measured water temperatures at the 124 wells and springs inventoried ranged from 12/sup 0/ to 93/sup 0/C (degrees Celsius) and averaged 50/sup 0/C. Estimated aquifer temperatures, calculated using the silica and the sodium-potassium-calcium geochemical thermometers, range from 5/sup 0/ to 370/sup 0/C and averaged 110/sup 0/C. Estimated aquifer temperatures in excess of 140/sup 0/C were found at 42 sites. No areal patterns to the distribution of temperatures either at the surface or subsurface were found. Generally, the quality of the waters sampled was good. Dissolved-solids concentrations range from 14 to 13,700 mg/l (milligrams per liter) and averaged 812 mg/l, with higher values occurring in the southeastern part ofmore » the State. Twenty-five areas were selected for future study. Of these areas, 23 were selected on the basis of estimated aquifer temperatures of 140/sup 0/C or higher and two on the basis of geologic considerations.« less