Estilos eruptivos asociados al volcanismo monogenético máfico de la región de Pasto Ventura, Puna Austral, Argentina

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.

Features That Favor the Prediction of the Emplacement Location of Maar Volcanoes: A Case Study in the Central Andes, Northern Chile

“…Nevertheless, if the location of the vent is closer to lakes or salars the magma-water ratios can increase, generating Surtseyan eruptions building tuff rings or tuff cones [94]. This set of features deployed to recognize the location of growth and fragmentation of phreatomagmatic eruptions that form maar volcanoes is supported by the maars reported by Filipovich, et al [141] in the Pasto Ventura monogenetic volcanic field, Puna Austral (Figure 11). Pasto Ventura's maars are located on the ridges (compressive tectonic setting), associated with water-saturated areas, endorheic basins such as lakes, groundwater recharge related to stratovolcanoes with snow, and rainfall by the Altiplanic winter (Figure 11).…”

The composition of amphibole phenocrysts in Neogene mafic volcanic rocks from the Puna plateau: Insights on the evolution of hydrous back-arc magmas

“…Domes are flat-topped and roughly circular (commonly named tortas) or coulèes. All the volcanic products have slight compositional difference from basaltic andesite to basaltic trachyandesite to trachyandesite (Filipovich et al, 2019). In thin section, lavas associated with scoria cones have a porphyritic vesicular texture with phenocrysts of anhydrous minerals only, whereas the lava domes show porphyritic texture with ubiquitous clinopyroxene and variable amounts of orthopyroxene, olivine and amphibole phenocrysts embedded in an intersertal to pilotaxitic groundmass.…”

“…The Neogene mafic volcanism in the Puna region comprises monogenetic volcanoes of small size that occur either as isolated centers or as clusters which form larger volcanic fields, the latter type being more numerous in the Southern Puna than in the north (Maro and Caffe, 2017;Báez et al, 2017;Maro et al, 2017b;Filipovich et al, 2019). Another contrast between these two regions is that the age of volcanism is somewhat younger in the south than in the north (Pliocene-Holocene vs. Upper Miocene-Lower Pliocene, respectively) (Kay et al, 1994;Risse et al, 2008;Maro and Caffe, 2017), where centers are notably more eroded (Maro and Caffe, 2017).…”

“…The Pasto Ventura volcanic field (26°43.7'S-67°12.5'W) is represented mainly by clustered small-volume, basaltic (basaltic andesite) J o u r n a l P r e -p r o o f features including scoria cones, domes, maars and tuff rings (Fig. 1) (Filipovich et al, 2019). The Carachipampa complex (26°34.3'S-67°26.5'W) consists of a cluster of lava flows, lava domes and superimposed, eroded scoria cones (Fig.…”

“…1). These volcanic structures are associated with a variability of eruptive styles such as effusive, Hawaiian, Strombolian, violent Strombolian and phreatomagmatic (Filipovich et al, 2019). Domes are flat-topped and roughly circular (commonly named tortas) or coulèes.…”