Abstract
One of the most outstanding features of the Southern Puna is the occurrence of a widespread monogenetic mafic volcanism during Neogene-Quaternary. Despite a number of published papers focusing on the petrogenesis of this back-arc volcanism, works aimed on its physical volcanology are scarce. This paper presents the characterization of the monogenetic mafic volcanism in the Pasto Ventura region, located in the southeast edge of the Southern Puna. The results show that in the Pasto Ventura region there is a low density of small-volume eruptive centers aligned with regional tectonic structures and a significant variability in eruptive styles (effusive, strombolian, hawaiian, violent strombolian and phreatomagmatic) and typology of volcanic structures (domes, scoria cones, maars and tuff rings). The first of these features is explained by a limited magma flow rate from the deep source and the use of favorable tectonic structures (oriented obliquely to the regional maximum compression direction) for the ascent of small volumes of magma through the upper crust. The variability of eruptive styles responds to the complex interaction of different endogenous and exogenous factors. The occurrence of effusive or explosive eruptions depends on the differences in magma ascent rates including periods of stagnation in the upper crust, which in turn control the efficiency of degassing and ultimately the occurrence of fragmentation. On the other hand, the more humid local climatic conditions (~150 mm/year), which are related to the geographical position of the Pasto Ventura region in the eastern edge of the Puna, favor the occurrence of phreatomagmatic activity. Phreatomagmatic activity also varies according to the topography, substrate typology and depth at which water-magma interaction occurs.
Highlights
El volcanismo monogenético produce, en general, volcanes de pequeño volumen con un amplio rango de estilos eruptivos, incluyendo estilos estrombolianos, hawaianos, estrombolianos violentos y freatomagmáticos (Valentine y Connor, 2015)
Eruptive styles related to the monogenetic mafic volcanism of Pasto Ventura region, Southern Puna, Argentina
One of the most outstanding features of the Southern Puna is the occurrence of a widespread monogenetic mafic volcanism during Neogene-Quaternary
Summary
En general, volcanes de pequeño volumen con un amplio rango de estilos eruptivos, incluyendo estilos estrombolianos, hawaianos, estrombolianos violentos y freatomagmáticos (Valentine y Connor, 2015). Esta variabilidad en los estilos eruptivos se refleja en el desarrollo de diferentes tipologías de estructuras volcánicas, que incluyen conos de escoria, flujos de lavas fisurales, domos, pequeños volcanes en escudo, anillos de tobas (tuff rings), conos de tobas (tuff cones) y maares (Valentine y Connor, 2015). Uno de los rasgos más sobresalientes de la Puna Austral es el desarrollo de un volcanismo monogenético máfico durante el Neógeno-Cuaternario (Deruelle, 1978, 1982, 1991; Viramonte et al, 1984; Alonso et al, 1984; Allmendinger et al, 1989; Knox et al, 1989; Kay et al, 1994; Krallmann, 1994; Guzmán et al, 2006; Fig. 1) representado por una serie de agrupaciones o campos volcánicos (clusters) formados por domos, conos de escoria, anillos de tobas y maares. Mediante la comparación del volcanismo de la región de Pasto Ventura con otras agrupaciones de volcanes monogenéticos máficos de la Puna Austral, se propone un modelo conceptual integrado que explica la ocurrencia de este volcanismo en el contexto geodinámico del extremo sur de los Andes Centrales
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