The Salar de Antofalla field covers a huge area of rather widely dispersed minor monogenetic mafic volcanism located wholly in Argentina between about 25° 30' and 26° 45'S and 67° 15' and 68° 15'W. This field includes centers in the Pasto-Ventura-El Penon area (Allmendinger et al. 1989), the Antofagasta de la Sierra field to the south and west of the Cerro Galan Caldera (Acenolaza et al., 1976; Thorpe et al., 1984; Francis et al., 1989), as well as larger centers such as Cerro El Condor and Cerro Peinado. E. Fielding has mapped many of these centers (Unpub. PhD thesis, Cornell University, 1989).
This collection of scoria cones and associated lavas and pyroclastics is the product of basaltic andesite volcanism which occurred sporadically since about ~11Ma, beginning with the eruption of rhyolites and progressing to basaltic andesite-andesite-dacite in the last 9 Ma (Richards et al., 2006). The vents are clearly related to young north-south trending fault systems, which appear to have acted as the upper crustal conduits for the relatively primitive magmas during a young episode of extension (Allmendinger et al., 1989). The lavas commonly contain partially fused xenoliths of metamorphic basement rocks and partially reacted xenocrysts of quartz and sodic plagioclase (Francis et al., 1989). These observations and their chemical characteristics argue for extensive interaction with the crust through which the magmas ascended (see section on Cerro Galan Caldera).
Acenolaza, F.G., Toselli, A.J., & Gonzalez, O., 1976. Geologia de la region comprendida entre el Salar del Hombre Muerto y Antofagasta de la Sierra, Provincia Catamarca. Rev. Assoc. Geol. Argent. 31, p127-315.
Allmendinger, R.W., Eremchuk, J.E., Sosa-Gomez, J., Ojeda, J., & Francis, P.W., 1989. The Pasto-Ventura pull-apart and the southward collapse of the southern Puna plateau. J. Latin. Amer. Earth Sci. 2, no. 2, p111-130.
Francis, P.W., Sparks, R.S.J., Hawkesworth, C.J., Thorpe, R.S, Pyle, D.M. Tait, S.R. Mantovani, M.S. and McDermott, F., 1989. Petrology and geochemistry of volcanic rocks of the Cerro Galan caldera, north west Argentina. Geol Mag. 126, p515-547.
Richards, J.P., Ullrich, T., Kerrich, R., 2006. The Late Miocene-Quaternary Antofalla volcanic complex, southern Puna, NW Argentina: Protracted history, diverse petrology, and economic potential. Journal of Volcanology and Geothermal Research, 152(3-4): 197-239.
Thorpe, R.S., O' Callaghan, L.J. and Francis, P.W. 1984. Relaticve roles of source composition, fractional crystallization and crustal contamination in the petrogenesis of Andean volcanic rocks. Phil. Trans. Roy. Soc. London A310, p675 - 692.