Mita, a Newly Discovered Geothermal System in Guatemala

Abstract

Mita is a moderate temperature geothermal system that was discovered in 1997 during gold exploration in southeastern Guatemala. This system is associated with bimodal basalt-rhyolite volcanism, and occurs alongside (and overlapping with) the Cerro Blanco 2 million ounce epithermal gold deposit. Fluids at temperatures up to 180°C were encountered in 150-400m deep gold exploration drillholes. Geothermometry on hot springs and well fluids indicated that most fluids were derived from the shallow 180°C reservoir, but that deep temperatures were at least 220°C.
The shallow reservoir appears to be a localized outflow from a deeper hotter system. A comprehensive MT resistivity survey suggested that the deeper reservoir was to the northeast of Cerro Blanco, and gravity surveys indicated some very strong structural control on deep permeability. Four 1000-1500m deep slimholes were drilled in 2008-09 to confirm the nature of the deep reservoir. It is planned to develop the geothermal system to provide geothermal power for the proposed gold mine and surplus power for the national grid to reduce Guatemala’s dependence on carbon fuels.