Calculated geothermal gradient for the Western Ouachita Mountains, Arkansas

Based on silica concentration of ground water for a 130 X 140 km area of the Ouachita Mountains, Arkansas a mean reservoir temperature of 44.3/sup 0/C was calculated utilizing quartz solubility. Additional calculations obtain a mean heat flow value of 46.4 mW/m/sup 2/, geothermal gradient of 20.2/sup 0/C/km and depth of water circulation of 1.4 km. This calculated geothermal gradient (20.2/sup 0/C/km) compares to other limited values ranging from 18.2 to 45.6/sup 0/C/km.