ABSTRACT
The hydrothermal deposits of the Ixtacamaxtitlán area are hosted by volcanic and intrusive rocks of the Mexican Ignimbritic belt. These deposits show quartz-chalcedony-sulfide banded veins and stockworks, kaolinite formation, and silica caps on top, interpreted as hydrothermal sinter. The occurrence of kaolinite is due to acid-sulfate alteration, possibly derived from boiling at shallow depths. The alteration assemblage ranges from clorite-sericite to acid-sulfate from the deepest parts. The characteristics of the ensemble, plus the geochemical anomalies in Au and Ag in the stockworks, may indicate the presence of economic mineralisation at depth. The deposits are interpreted as hot spring-type low-sulphidation epithermal deposits.
