The effect of fault systems on volcanic activity: Insights from the subduction-related, Quaternary Villamaría-Termales monogenetic volcanic field in Colombia

Abstract

Structural control of volcanic activity is a topic of great significance around volcanic fields, mostly associated with risk management near cities. Structural geology provides valuable information for understanding the magmatic processes associated with the rise of magma and the presence of volcanoes. The Villamaría-Termales Monogenetic Volcanic Field (VTMVF) is a group of Quaternary monogenetic volcanoes settled in an active fault system, which allows us to propose the role that these faults play in the volcanic activity. The field is located near the city of Manizales (∼475.000 inhabitants), Colombia, on an active fault system at the western flank of the Cordillera Central in the northern Andes. The VTMVF is characterized by andesitic lava domes and flows, which individually reach volumes of up to 2.5 km3. This work uses 1) geometry and kinematics of the faults that affect the VTMVF to define the structural features associated with the emplacement of the volcanoes, and 2) new and published ages to evaluate periods of volcanic activity. Three trends of fault systems associated with the location of the volcanoes were identified: 1) NW-SE (Villamaría-Termales), 2) NE-SW (Sancancio, El Perrillo, Santa Rosa and Palestina), and 3) N-S to NNE-SSW (San Jerónimo and Samaná-sur). The fault kinematics are dominantly normal, with dextral (NE) and sinistral (NW) movements. Analysis of ages shows that the field has temporally evolved since 2 Ma in different time intervals (2.0–1.2 Ma, 0.18–0.045 Ma, and 0.045 Ma – Present). This supports the presence of different emplacement mechanisms related to both the movement in the strike of some faults and the intersection between faults. The pauses of volcanic activity could coincide with the absence of structural conditions (interseismic cycles for faults, where the sealing of the faults is generated) to facilitate the rise of magma; this is related to temporary compressive conditions. Despite the apparent structural controls, there is no clear spatial or temporal pattern of volcano distribution within the field. There is evidence of seismic activity in the area. Thus, the future formation of dilatating zones that allow the magma to rise and the emplacement of new monogenetic volcanoes is feasible not only in the area defined for the volcanic field but also in the continuation of the fault lines around it.