Numerical recognition of alignments in monogenetic volcanic areas: Examples from the Michoacan-Guanajuato Volcanic Field in Mexico and Calatrava in Spain

Identification of geological lineaments using numerical methods is a useful tool to reveal structures that may not be evident to the naked eye. In this sense, monogenetic volcanic fields represent an especially suitable case for the application of such techniques, since eruptive vents can be considered as point-like features. Application of a two-point azimuth method to the Michoacan-Guanajuato Volcanic Field (Mexico) and the Calatrava Volcanic Province (Spain) demonstrates that the main lineaments controlling the distributions of volcanic vents (similar to 322 degrees in Calatrava and similar to 30 degrees in Michoacan) approach the respective main compressional axes that dominate in the area (i.e. the Cocos-North America plates convergence and the main Betics compressional direction, respectively). Considering the stress fields that are present in each volcanic area and their respective geodynamic history, it seems that although volcanism may be a consequence of contemporaneous extensional regimes, the distribution of the volcanic vents in these kinds of monogenetic fields is actually controlled by reactivation of older fractures which then become more favourable for producing space for magma ascent at near-surface levels. (C) 2010 Elsevier B.V. All rights reserved.