Geochemical Exploration of the Calistoga Geothermal Resource Area, Napa Valley California

Abstract

Chemical analysis of well waters in he upper Napa Valley, near the cit of Calistoga, California suggest that the upwelling and localization of fluids with temperatures up to 135°C may be related to faulting or fracturing along the geographic axis of the Napa Valley. Calculated temperatures from chemical geothermometers are always higher than measured temperatures, with maximum values often 50°C higher than sampling temperature at well point. Two shallow, subsurface systems of moderate high temperatures were detected using waters with locally high chloride values (Ca 180ppm). Maximum reservoir temperatures may exceed 150°C. Mixing of the geothermal water with shallow, cool groundwater's is indicated by intermediate concentrations of C1, F an B by ternary molality plots of Ca, B and HC3 and by a trillinear diagram of major cations and anions.