Near-Surface Geochemical Investigations in the Las Hornillas Fumarolic Area, Miravalles Volcano, Costa Rica

Abstract

Preliminary investigations of out-gassing patterns associated with surface hydrothermal manifestations in the Las Hornillas area are here reported. These patterns have been resolved by using measurements of near surface concentrations of radon in ground gas, total mercury in soils, and of these soil s obtained from sample locations systematically distributed within an area of approximately 2.5 X 1.5 km. Results from these investigations indicate the existance of two distinct systems through which gases separated from a deep thermal aquifer circualte. A t the point on the surface where these systems intersect, the greatest amount of out-gassing is seen to occur. Soil mercury concentrations correlate well with shallow ground temperatures, yet appear to be more effected by near surface influences degree of hydrothermal teration) than do radon concentrations.