The distribution of hydrothermal minerals, common mineral assemblages and microthermometry of fluid inclusion were determined in cuttings from wells located all over the Cerro Prieto Geothermal Field. Deep samples of cuttings and fragments of cores were studied mainly from the production zone. This zone has been named as the silica epidote zone (SEZ) and it is located mainly in sandstones.The most common paragenetic associations show three ranges of temperature in this zone of the field: 200 ºC, 200-250 ºC, 250-300ºC. The first one is characterized mainly by clays, calcite and quartz; the second one by quartz, epidote, chlorite and micas, and the third one represented by epidote, amphiboles, illite and chlorites. A preliminary study of fluid inclusions in authigenic quartz showed two phase (L +V) fluid inclusions with variable salinity.