Chemical hierarchy of hydrothermal signals at surface and hierarchy of eventual geophysical investigations in geothermal exploration

In this paper a strategy is presented for geothermal prospecting in developing countries that brings to locate the first exploratory geothermal well by using only geochemical parameters in fluid phase in natural thermal emergences. The paper suggests a hierarchy of natural thermal manifestations, briefly describing how to interpret the most relevant chemical parameters. Once the selection of the most promising area on a country, or a regional scale has been done, local investigation of the aquifer(s), especially in flat areas, in terms of: temperature and pH, and eventual tele-thermal parameters that can be analyzed in the field (e.g. NH4, SiO2, Hg) should bring to the delimitations of closed anomalies. If more parameters will converge to the same area(s), it is very likely that that place is the top of a buried thermal fluid convective high and likely the best place to drill the first exploratory well.