Preliminary Geothermal Assessment of the Macizo Volcanico Del Ruiz, Colombia

Abstract

The Macizo Volcanico del Ruiz is a chain of Quaternary strato-volcanoes, aligned in a NNE-SSW direction, that is part of the Central Colombian Ridge. This is, in turn, part of the northern portion of Los Andes, and its volcanic activity can be explained by the subduction of the Nazca Plate beneath the South American Plate. Rocks forming the volcanoes are mainly andesites of calc-alkaline type, with minor basaltic to dacitic variations and some pyroclastics deposits. The Quaternary andesites are underlain by Miocenic andesites, Paleozoic schists and Paleocenic-Eocenic granodioritic intrusives. All these rocks are affected by four main structural trends: NNE-SSW, N-S; although faults of the NNE-SSW trend are the oldest, there is seismic activity related to some of them. The superficial hot springs, hot soils and fumaroles were grouped into 16 geothermal zones, most of them being hot springs with related gases. Liquid geothermometry results in deep temperatures, in some cases, of about 220 to 260?C. A high geothermal potential was assessed in the Macizo Volcanico del Ruiz. The most important area is named Nereidas-Botero Londoiio, Volcan Machin being second and Laguna del third. In the latter, as in another geothermal interest zones, studies are recommendable, while the Las Nereidas-Botero Londoiio and Volcan Machin areas can be drilled with a high probability of success.