HYDROGEOCHEMISTRY OF THERMAL WATERS FROM EJIDO PIEDRAS DE LUMBRE, CHIHUAHUA, MEXICO

Ejido Piedras de Lumbre, Maguarichi, is located in the southwestern part of the mexican state of Chihuahua, within the Sierra Madre Occidental (SMO) physiographic province, approximately 350 km southwest from Chihuahua City. The Piedras de Lumbre Geothermal Zone (PLGZ) is characterized by the appearance of 96 fumaroles, hot springs of sodium-chloride composition and wide alteration zones (kaolin). The area has a rich mining history, with mining activities (Ag–Pb–Zn–Cu–Au) active for the last 200 years. The reservoir rock of the PLGZ is a fractured rhyolitic rock covered by shallow coluvial sediments. From 2001 to 2007, a small geothermal power plant gave electricity to the Maguarichi town. Nowadays, a proposal to make it a tourist attraction is being considered by federal and local authorities. Major and trace elements including Li, B and Sr and isotopic data (delta²H and delta¹⁸O) for geothermal water samples, collected in the Piedras de Lumbre Gothermal Zone in October 2011 and May 2012 are reported. Temperatures range from 80°C to 98°C, with major ion and heavy element concentrations below the mexican drinking water normative values (NOM-127-SSA1-1994). A delta²H vs. delta¹⁸O plot show the samples close to the Meteoric Water Line, indicating that the PLGZ sampled waters have a local meteoric origin, and show no signs of mixing between meteoric and magmatic water.