ABSTRACT
The previous Chapter 26 provided an overview of the principal geothermal areas of Central America, their actual stages of exploration and exploitation, and their geological settings. Now, the chemical and isotopic composition of geothermal fluids, which are available from geothermal surface manifestations such as hot springs and fumaroles, or in some cases, as deep reservoir fluids from drilled geothermal wells, will be discussed. Chemical water types and their variability within the region as well as in specific sites — which reflects the influence of different environments for waterrock interaction processes — and the correlation of the water chemistry with existing geological structural features, such as volcanic ring calderas, sealing horizons, oriented faults and lithological variations, are analyzed. Furthermore, the chemical and isotopic character of surface manifestations, such as hot springs and fumaroles, are used to derive information on primary reservoir conditions and to identify secondary chemicalphysical processes which occur during the ascent of the geothermal fluids. Conceptual models of hydrogeochemical and isotopic evolution are presented for different geothermal systems. Geothermal gases will be discussed separately in Chapter 28.
