Eruptive parameters of volcanoes Melón, Mina, Tzinzimacato Grande, Tzinzimacato Chico (Mexico) from morphology and petrographic studies

Four monogenetic volcanoes were formed during the last 100 ka (Late Pleistocene), west of the city of Morelia (Mexico), in the central-eastern part of the Michoacán-Guanajuato Volcanic Field, located in the central region of the Trans-Mexican Volcanic Belt. These include four scoria cones (Melón, Mina, Tzinzimacato Grande, and Tzinzimacato Chico) and some lava flow deposits associated with the material emitted during the effusive phase of the volcanoes. From the study of stratigraphic relationships in the field and geological mapping, the eruptive chronology of the monogenetic volcanoes was determined. Subsequently, based on the analysis of the morphological (flow dimensions) and petrographic characteristics, the eruptive parameters (effusion rate and emplacement time) and the rheology of the lavas were estimated. The flow units of the effusive phase of the volcanoes present different morphological and mineralogical characteristics. The flows with greater slopes have average viscosities of 2.7x10⁸ P and a higher volume content of phenocrysts; the value of this property decreases in the flows with lower slopes, 1.7x10⁸ P as respectively. The results indicate that the most voluminous eruption corresponds to that emitted by the Mina volcano, with an effusion rate of 2.3 m³/s and a total duration of 239 days. The Tzinzimacato Chico volcano emitted a smaller volume of lava during its eruption, with an effusion rate of 0.9 m³/s and a total duration of 117 days, which is considered the most recent.