Convective geothermal systems in Trans-Pecos Texas, and Chihuahua and Coahuila, Mexico, are potential energy resources. The geothermal systems, which lie along a narrow belt near the Rio Grande River, are characterized by hot springs and shallow hot wells located along normal faults. The hot water is meteoric water that has circulated to depths of 2-3 km (1-2 mi), been heated, and risen to the surface through fractures along fault zones. The heat source is the Earth's normal thermal gradient, which is as high as 40°C/km (202°F/100 ft); no young magma bodies are involved. Maximum measured temperatures are 90°C (194°F) at a hot spring in Chihuahua, about 80°C (176°F) in 2 wells in the Sierra Vieja, and about 75°C (167°F) in several we ls east of El Paso. Many springs have temperatures in the range 35-50°C (95-122°F). Maximum subsurface temperatures estimated from chemical geothermometers are 100-160°C (212-320°F); most are considerably lower. Chemical constraints on use should be negligible except for the El Paso-area waters, which have moderately high dissolved solids (10,000 mg/L). Hydrologic data to evaluate possible production rates are generally sparse. None of the waters are hot enough to generate electricity by currently available technology. The highest temperature waters could be used for industrial or space heating, but, except for the area near El Paso, they are too far from population centers.

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