Petrology of the Luingo caldera (SE margin of the Puna plateau): A middle Miocene window of the arc–back arc configuration

GUZMÁN, S.; PETRINOVIC, I. A.; BROD, J. A.; HONGN, F.; SEGGIARO, R.; MONTERO, C.; CARNIEL, R.; DANTAS, E.; SUDO, M.

JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH

ELSEVIER SCIENCE BV

Año: 2011 vol. 200 p. 171 - 191

0377-0273

The Central Volcanic Zone (CVZ) of the Central Andes is developed between 14-28ºS (Thorpe et al. 1984, Francis and de Silva 1991) and is characterized by the presence of abundant Miocene to Recent ignimbrites, lavas and subvolcanic bodies (e.g. Baker and Francis 1978). The CVZ hosts the Altiplano - Puna Volcanic Complex (APVC: de Silva 1989) between 21-24ºS, where the presence of large volumes of ignimbrites and abundant calderas was interpreted by de Silva (1989) as the result of an “ignimbrite flare-up” (de Silva 1989), bringing the region to the focus of various subsequent studies (e.g. de Silva 1989; Ort et al. 1993; Lindsay et al. 2001a, b; Soler et al. 2007; Petrinovic et al. 2010: Aguas Calientes no esta en el apvc creo). As a characteristic, the APVC ignimbrites are predominantly crystal-rich calc-alkaline dacites (e.g. Harmon et al. 1984; de Silva and Francis 1989; Soler et al. 2007). In contrast, the ignimbrites of the Southern CVZ (25 - 27ºS) have few detailed studies and a small number of recognized volcanic centres. A conspicuous compositional bulk differences are detected in meridional belts. Between 67 - 69ºW they are characterized by small to medium volume (< 10 km3), crystal - poor ignimbrites of felsic compositions (e.g. Siebel et al. 2001; Schnurr et al. 2007), while to the east, the large - volume Cerro Galán caldera (e.g. Sparks et al. 1985) and the recently identified Luingo Caldera (Guzmán and Petrinovic 2008; Guzmán and Petrinovic 2010), are dacitic to rhyodacitic and crystal-rich, as most of the APVC ignimbrites, Luingo is the oldest and south-easternmost caldera (13-12 Ma: Guzmán and Petrinovic, 2010) recognized in the SE Altiplano - Puna plateau margin. In the present article we describe the petrography, mineral chemistry and geochemistry of the Luingo volcanic rocks in order to characterize their composition and their magmatic evolution. As the Luingo caldera is set close to the well known Cerro Galán caldera, it allows to investigate their possible genetic relationship as early suggested by González et al. (1999) and Hongn and Seggiaro (2001). Furthermore, the Luingo caldera becomes a key area to understand possible variations of magmas before and after the major thickening event (ca. 10 Ma: e.g. Isacks 1988) of the Puna. Finally, we discuss the regional significance of the Luingo volcanic rocks in relation to other coeval ignimbrites, placed westward in the Southern CVZ, as well as a brief discussion about the possible Middle Miocene arc-backarc configuration of the southern Puna.