Characterization of Fractured Basement Rocks from Two Geothermal Areas: Charlevoix Meteorite Impact Crater (Canada) and Nevado del Ruiz Volcano (Colombia)

Abstract

The Nevado del Ruiz Volcano (NRV) in Caldas Department (Colombia) and the Charlevoix region in Quebec Province (Canada) are areas of interest for geothermal development with potential resources located in fractured basement rocks. The NRV is an active andesitic stratovolcano characterized by a hydrothermal system associated with several hot springs and fault systems. The volcanism in the study area is caused by the subduction of the Nazca Plate below the South American continent. The fractured basement is characterized by the Cajamarca metamorphic complex, which is the formation of most interest for geothermal exploration. The Charlevoix region, located northeast of Quebec City, is an area that was affected by a Paleozoic meteorite impact known as the Astroblème de Charlevoix. Inside the crater, high fracture density is expected due to the energy released by the meteorite impact. The network of fractures generated can be favorable for groundwater flow. In addition, the presence of insulating rocks, such as the Saint-Urbain Anorthosite, may provide a steeper geothermal gradient that other areas in the Charlevoix region. Heat transfer and groundwater flow numerical simulations can be used as a tool to assess geothermal potential of reservoirs. This can be challenging for fractured basement rocks where equivalent thermal and hydraulic rock properties are hard to define. Models can be further constrained with hydrogeochemical data for robust numerical simulations. The objective of this study is to evaluate equivalent thermal and hydraulic properties of fractured rock masses based on samples and field observations collected in both areas of study, which are at an early geothermal exploration stage, and to analyze hot spring water samples collected in the NRV area. The laboratory and field characterization of the two areas of interest will be used as a basis for numerical simulations of heat transfer, groundwater flow, and production wells for direct geothermal use in the Charlevoix region and electricity production at the Nevado del Ruiz Volcano.