Volcán Tancítaro, Michoacán, Mexico, 40Ar/39Ar constraints on its history of sector collapse

Volcán Tancítaro is a 97 ± 3 km3 stratovolcano located in the Michoacán Guanajuato volcanic field (MGVF), part of the Trans Mexican Volcanic Belt. Prior to this study, there was only one K–Ar date (530 ± 60 ka; [Ban, M., Hasenaka, T., Delgado-Granados, H., Takaoka, N., 1992. K–Ar ages of lavas from shield volcanoes in the Michoacán–Guanajuato volcanic field, Mexico. Geofisica Internacional 31 (4), 467–473.] and one sector-collapse event reported for this volcano in the literature [Garduño-Monroy V.H., Corona-Chavéz, P., Israde-Alcantara, I., Mennella, L., Arreygue, E., Bigioggero, B., Chiesa, S., 1999. Carta Geológica de Michoacán, scale 1:250,000. Universidad Michoacana de San Nicolás de Hidalgo.; Capra, L., Macías, J.L., Scott, K.M., Abrams, M., Garduño-Monroy, V.H., 2002. Debris avalanches and debris flows transformed from collapses in the Trans-Mexican Volcanic Belt, Mexico — Behavior, and implications for hazard assessment. Journal of Volcanology and Geothermal Research 113, 81–110.]. Twenty-six new 40Ar/39Ar ages indicate that Volcán Tancítaro became active ≥ 793 ± 22 ka and that the most recent effusive activity occurred at 237 ± 34 ka. Two catastrophic sector-collapse events are identified and dated; the first one occurred on the west side between 694 and 571 ka, whereas the second one occurred on the east side between 261 and 238 ka. The older collapse produced a 2.3–3.4 km3 debris-avalanche and laharic deposit spread over ∼ 567 km2, whereas the more recent collapse left a 3-km wide, horseshoe-shaped scar on the eastern flank and produced a 3.6–7.0 km3 debris-avalanche and laharic deposit that covers ∼ 654 km2. Reconstruction of the main edifice of Volcán Tancítaro using ArcGIS software and digital elevation models indicates that the volume removed during the eastern sector collapse was ∼ 4.7 km3.