A Geological and Hydro-Geochemical Study of the La Grande area, Union County, Oregon

Abstract

Several thermal springs and wells are in the Grande Ronde Valley of northeastern Oregon. The valley is a complexly faulted graben. The hottest waters are closely associated with faults and fault intersections. The youngest rocks in the area are Miocene and sites. Thermal waters contain approximately 500 mg/1 of dissolved solids. The hottest waters contain sodium and chloride as principle ions while sodium and bicarbonate predominate in the cooler waters. All thermal waters appear to have equilibrated below 100°C and generally within 25°C of their surface temperature. Data thus far indicate that the La Grande area is not suitable for geothermal electric production. The area holds great promise however, for lower temperature usage based on the availability of hot water and current industrial demand for the resource.