Hydrothermal Alteration Minerals in Los Azufres Geothermal Field, Michoacan, Mexico

Abstract

X-ray powder difiaction, electron microprobe analyses and classical optical methods were used to identify hydrothermal minerals in Los Azufies geothennalfield. n e information obtainedfiom individual welh was used to integrate a distribution map of aheration minerals. Observedpattems of alteration have been correlated with homogenization temperatures. According to their formation conditions, authigenic minerals in Los Azuji-es may define three them1 zones. Ihe low thermal zone defined by: Amorphous silica + native sulphur + smectite + gypsum + alunite + kaolinite. 2he intermediate zone represented by: Calcite + wairakite + quartz + chlorite + anhydrite. Ihe high temperature zone is represented by: Quartz + microcline + prehnite + epidote. A brief description of main characteristics of the most common hydrothermal minerals is presented below.