Exploration in the Cordon Caulle Geothermal Area, Southern Chile: Comparison with Other Geothermal Systems Based on Gas Geothermometry

Abstract

The CordÛn Caulle geothermal area, Southern Chile, hosts an active geothermal system expressed at surface in multiple fumaroles and boiling hot springs. The latter correspond essentially to dilute (TDS < 600 ppm), low chloride (< 50 ppm)-bicarbonate thermal waters, where solute geothermometers yield subsurface temperatures in the range of 150?-170?C. Using CO2/Ar-H2/Ar, CO/CO2-CH4/CO2 and CO/CO2-H2/H2O gas ratio plots, subsurface temperatures greater than 300?C are estimated for fumaroles and on the order of 160?C for hot spring gases. Fumaroles also match the expected compositions of vapours separated at low temperature (< 200?C), supporting a model of a deep boiling liquid-dominated geothermal reservoir overlain by shallow steam-heated layers. In order to test these findings, gas chemistry data from selected liquid-dominated and vapour-dominated systems are also incorporated for comparison.