Geothermal investigations in Idaho. Part 3. An evaluation of thermal water in the Weiser area, Idaho

Abstract

The Weiser area encompasses about 200 square miles in southwest Idaho and contains two thermal water areas: (1) the Crane Creek subarea, which is 12 miles east of Weiser, Idaho, and (2) the Weiser Hot Springs subarea, which is 5 miles northwest of Weiser. Volcanic and sedimentary rocks of Miocene to Pleistocene age have been faulted and folded to form the northwest-trending anticlines present in much of the area. Basalt of the Columbia River Group or underlying rocks are believed to constitute the reservoir for the hot water. Gravity and magnetic anomalies are present in both subareas. A preliminary audio-magnetotelluric survey indicates that a shallow conductive zone is associated with each thermal site. Above-normal ground temperatures measured at a depth of 1 metre below the land surface in the Weiser Hot Springs subarea correlate with relatively high concentrations of boron in underlying ground waters, which, in turn, are usually associated with thermal waters in the study area. Sampled thermal waters are of a sodium chloride sulfate or sodium sulfate type, having dissolved-solids concentrations that range from 225 to 1,140 milligrams per litre. Temperatures of sampled waters ranged from 13/sup 0/ to 92.0/sup 0/C. Minimum aquifer temperatures calculated from chemical analysismore » of water, using geochemical thermometers, were 170/sup 0/ and 150/sup 0/C in the Crane Creek and Weiser Hot Springs subareas, respectively. Estimated maximum temperatures ranged from 212/sup 0/ to 270/sup 0/C and 200/sup 0/ to 242/sup 0/C, respectively, in these subareas. The probable heat sources for both subareas are (1) young magmatic intrusive rocks underlying the basalt or (2) above-normal temperatures resulting from thinning of the earth's crust. Maps are included.« less