Hydrothermally Altered Rocks and Their Implications for Debris Flow Generation in the Monarch Butterfly Biosphere Reserve, Mexico

Hydrothermally altered andesitic breccia with significantly weakened geomechanical properties—exhibiting a compressive strength of just 0.47 ± 0.05 MPa—was identified as the critical factor triggering debris flows in the Canoas microbasin within Mexico's Monarch Butterfly Biosphere Reserve. Unlike unaltered andesite (36.26 ± 18.62 MPa), the altered rock displays soil-like characteristics, high clay and silt content, and susceptibility to saturation collapse during heavy rainfall. Fieldwork and petrographic analysis revealed extensive replacement of phenocrysts by sericite, kaolin, iron oxides, and clays, underscoring hydrothermal alteration as a key control for slope instability in volcanic regions. These findings provide critical insights for geological risk management in mountainous areas.

Jiménez López, L. Á., Sánchez Núñez, J. M., Pola, A., Escamilla Casas, J. C., Sereno, H. I., Rodríguez Contreras, P., & Serrano Flores, M. E. (2025). Hydrothermally Altered Rocks and Their Implications for Debris Flow Generation in the Monarch Butterfly Biosphere Reserve, Mexico. GeoHazards, 6(4), 62. https://doi.org/10.3390/geohazards6040062