Chemical variations in hydrothermal minerals of the Los Humeros geothermal system, Mexico

摘要

The Los Humeros geothermal system is composed of more than 2200 m of Quaternary altered volcanic rocks and an underlying Cretaceous sedimentary sequence. The low salinity of the fluids discharged at present(Na~+ and Cl~- concentrations < 500 ppm), and the excess steam, indicate that the reservoir contains a mixture of steam and dilute groundwater. Water- rock equilibrium is not attained. Hydrothermal mineral are present in veinlets, vugs, and replacing primary minerals. Three mineral zones are recognized: 1)a shallow argillic zone (<400 m depth), 2)a propylitic zone(ranging between 500 and 1800 m)and 3)a skarn zone (>1800 m).