New Areas of Geothermic Interest in the Central Cordillera of the Colombian Andes: Santa Rosa and Cerro Machín

Abstract

Colombia is part of the Pacific Ring of Fire, because of this has a privileged location to explore geothermal systems. Colombia has three cordilleras with trend N-NE. Recently volcanic activity and high enthalpy geothermal systems are recorded in the Central Cordillera. Colombian Geological Survey has begun the exploration of new areas with geothermal potential in this Cordillera, such is the case of Santa Rosa and Cerro Machín areas, which have been found geothermal superficial evidence. The Santa Rosa geothermal area is located in the western flank of Paramillo de Santa Rosa stratovolcano. It is compound by Paleozoic-Mesozoic metamorphic rocks, Cretaceous metavolcanics-metasedimentaries rocks and Quaternary volcanic deposits. Exits two regional fault systems are approximately perpendicular to each other. The first one in directions NNE-SSW and NE-SW, coincidences with the directions that are generally found in the tectonic systems of the Andean chain. The second system direction NW-SE to EW. In the area have been evidenced the thermal manifestations such as hot springs until to 90 ° C with marked structural control and rocks with phyllic-propylitic alteration has been recognized. The Cerro Machín volcano geothermal area is located to 35 km to SE of Santa Rosa area. It has a very high explosive behavior. Geology consists in Triassic schists, green schists, phyllites and volcanic deposits with ages less than 50.000 years and dacite domes. The alteration rocks are almost restricted to the intercalderic domes result of the interaction between rocks with superficial steam, besides some volcanic lithics into volcanic deposits (less 10.000 years) have hydrothermal alteration. Locally, the structural trend is N-NE. Hot springs are restricted to the proximal crater area and controlled by main rivers and streams with northeast orientation, they are bicarbonate waters with temperature from 20°C to 90°C. In the other hand, gases emanations in the top of the intracalderic domes are found. New evidence of H2S were found in a stream near to the volcano and 5 km to east of main crater, indicating probably another magmatic chamber or a strong structural control which get these gases away to far of the crater. In order to enhance the exploration, structural geology characterization, geochemistry analysis in gases and potential methods acquisition will be applied.