Morphostructural controls on heat flow and fluid circulation in the Valle de Nereidas geothermal field, Nevado del Ruiz, Northern Andes, Colombia

• Morphostructural features are essential for geothermal resource evaluation. • Heat contribution is primarily associated with volcanic emission centers and units younger than 2 Ma • Fluid circulation and recharge zones correspond to fractured lava flows • Thermal contraction in the lava flows facilitates the infiltration and movement of regional groundwater Morphostructural features are essential for geothermal resource evaluation. They provide insights into geological structures and surface features that are linked to geothermal activity, thus enhancing exploration and resource characterization efficiency. This study assesses a place with recognized geothermal energy via structural lineaments, and morphological environments and geological units using diverse satellite images information and fieldwork resources to define the morphostructural framework of the Valle de Nereidas geothermal field. The results indicate that: 1) heat contribution in the study area is primarily associated with volcanic emission centers and units younger than 2 Ma, extending beyond the Nevado del Ruiz volcanic complex; and 2) fluid circulation and recharge zones correspond to fractured lava flows, where thermal contraction facilitates the infiltration and movement of regional groundwater. These findings suggest that the geothermal system in the Valle de Nereidas is controlled by both volcanic and structural features, where young volcanic edifices act as heat sources, and faulted and fractured zones enhance fluid circulation. Data from the drilled well Nereidas-1, including lithological descriptions, helped to establish relationships between subsurface geology and surface expressions of geothermal activity. These results help to define the spatial distribution of thermal anomalies and recharge areas, which directly impact resource sustainability and reservoir management. Furthermore, they provide valuable information for improving geothermal exploration strategies in the area by refining the model of subsurface heat transport and fluid dynamics.