Structural Control on Thermal Anomalies and Diffuse Surficial Degassing at Berlin Geothermal Field, El Salvador

摘要

Concentrations of soil gases (O_(2), CO_(2), N_(2), H_(2), He, Ar, Rn, CH_(4) and H_(2)S) and the efflux of carbon dioxide at the Berlin Geothermal Field, El Salvador has been investigated. Soil pressure gradient and temperature were also measured. A grid of 157 points was sampled. Results of this investigation suggests that the occurrence of hydrothermal manifestations, the release of hot gases and vapor, and the transfer of heat at the Berlin Geothermal Field are coupled processes that are related to the fault systems in the area. Soil gas anomalies occur aligned with the NW-SE, NNE-SSW and WNW-ESE fault systems. As in the Ahuachapan Geothermal Field, (DELTA)He anomalies allow the identification of spatial trends associated with buried WNW-ESE faults related to the formation of the Central American Graben. ~(220)Rn/~(222)Rn anomalies located along a circle suggest the existence of a buried caldera. The study of soil gas composition and fluxes of CO_(2) has shown to be an important geochemical method to identify vertical zones of high permeability.