FORO: A new type of maar volcano from the State of Durango-the El Jagüey-La Breña complex reinterpreted; a discussion

Resumen

In the past four years, we have been studying the geology and petrology of the Durango volcanic field (DVF) (Aranda-Gómez et al., 1988, 1989, 1991; Smith et al., 1989; Pier et al., 1991). We paid special attention to the La Breña-El Jagüey volcanic complex (LBEJVC), because it is one of the few places in the DVF in which the detailed evolution of a volcanic center can be unraveled, and where a collection of volcanic rocks, whose relative ages could be inferred, can be obtained. According to our interpretation, the LBEJVC consists of two intersecting maars-La Breña (LB) and El Jagüey (EJ)-at least two pre-maar scoria cones and associated lavas, and a series of nested post-maar lava and scoria cones that erupted within LB and flooded its floor with lava (Figures 1 and 2, a). A completely different model for the evolution of LBEJVC was recently proposed by Swanson (1989). In this communication, we will briefly summarize the two models and then review key field and laboratory observations that, we believe, support our model and contradict the model of Swanson (1989). Our field observations led us to propose a model for the geological evolution of the complex (Aranda-Gómez et al., 1988, in press), which forms the basis of our petrogenetic model (Pier et al., 1991).

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