The eruptive history of the Pátzcuaro Lake area in the Michoacán Guanajuato Volcanic Field, central México: Field mapping, C-14 and 40Ar/39Ar geochronology

Abstract

Monogenetic volcanic fields occur in many tectonic settings representing an unpredictable and uncertain volcanic hazard. The Pátzcuaro Lake is located in the central part of the Michoacán-Guanajuato Volcanic Field (MGVF). Field mapping of an area of 560 km2, stratigraphy and new radiometric ages (40Ar/39Ar and 14C) aided in the identification of 45 individual volcanic landforms formed during the past 3.9 Ma. These landforms comprise five medium-size shield volcanoes, 25 scoria cones, 10 lava domes, two lavas associated to scoria cones, one fissural lava flow, and two volcanic complexes. These volcanic edifices erupted a minimum volume of 20 km3 since Pliocene with an output rate of 0.02 km3/ka. Chemical composition of magmas ranges from 47.6 to 65.3 wt% silica, being dominantly andesites (~76 vol%), followed by basaltic-andesites (~12 vol%), dacites (~9 vol%) and basalts (~3 vol%). Volcanic products vary from mainly andesitic during the Pliocene, basaltic to dacitic during the Pleistocene and basaltic-andesitic to andesitic during the Holocene. All these rocks are the result of low-dipping slab subduction-related magmatism. Alignment of cones and structures follow NE-SW, N-S and E-W directions. The youngest faults are associated with the E-W Morelia-Acambay Fault System, with historic earthquake activity. The volcanic complexes, El Estribo and La Muela, have cone collapses to the north that correspond with the direction of maximum regional extension associated with the E-W fault system. The 3.9 Ma history of monogenetic volcanism around the Pátzcuaro Lake demonstrates that monogenic fields can be long-lived volcanic features.