Journal of South American Earth Sciences 84 (2018) 184–200 Contents lists available at ScienceDirect Journal of South American Earth Sciences journal homepage: www.elsevier.com/locate/jsames Geological evolution of Paniri volcano, Central Andes, northern Chile T ∗ Benigno Godoya, , José Lazcanob,1, Inés Rodríguezc, Paula Martíneza,2, Miguel Angel Paradaa, Petrus Le Rouxd, Hans-Gerhard Wilkeb, Edmundo Polancoe,3 a Departamento de Geología y Centro de Excelencia en Geotermia de los Andes (CEGA), Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Plaza Ercilla 803, Santiago, Chile b Departamento de Ciencias Geológicas, Facultad de Ingeniería y Ciencias Geológicas, Universidad Católica del Norte. Avenida Angamos 0610, Antofagasta, Chile c Red Nacional de Vigilancia Volcánica, Servicio Nacional de Geología y Minería, Avenida Santa María 0104, Providencia, Santiago, Chile d Department of Geological Sciences, University of Cape Town, Rondebosch 7701, South Africa e Energía Andina S.A., Cerro El Plomo 5630, Las Condes, Santiago, Chile ARTICLE INFO ABSTRACT Keywords: Paniri volcano, in northern Chile, belongs to a volcanic chain trending across the main orientation of the Central Central Andes Andean volcanic province. Field work mapping, stratigraphic sequences, and one new 40Ar/39Ar and eleven Paniri volcano previous published 40Ar/39Ar, and K/Ar ages, indicate that the evolution of Paniri involved eruption of seven AFC-Like evolution volcanic units (Malku, Los Gordos, Las Lenguas, Las Negras, Viscacha, Laguna, and Llareta) during four main Plagioclase fractionation stages occurring over more than 1 Myr: Plateau Shield (> 800 ka); Main Edifice (800–400 ka); Old Cone Physical volcanology (400–250 ka); and New Cone (250–100 ka). Considering glacial and fluvial action, an estimated 85.3 km3 of volcanic material were erupted during the eruptive history of Paniri volcano, giving a bulk eruption rate of 0.061 km3/ka, with major activity in the last 150 kyr (eruption rate of 0.101 km3/ka). Lava flows from Paniri show abundant plagioclase together with subordinate ortho-, and clino-pyroxene, and amphibole as main phenocrysts. Moreover, although true basalts are scarce in the Central Andes, olivine-bearing lavas were erupted at Paniri at ∼400 ka. Also, scarce phenocrysts of biotite, quartz, rutile, and opaque minerals (Fe-Ti oxides) were identified. The groundmass of these flows is composed mainly of glass along with pyroxene and plagioclase microlites. Consolidated and unconsolidated pyroclastic deposits of dacitic composition are also present. The consolidated deposits correspond to vitreous tuffs, whilst unconsolidated deposits are composed of pumice clasts up to 5 cm in diameter. Both pyroclastic deposits are composed of glassy groundmass (up to 80% vol.), and subordinated plagioclase, hornblende, and biotite phenocrysts up to 1 cm in length. Results of twenty- four new, coupled with previous published compositional analyses show that volcanic products of Paniri vary from 57% (basaltic-andesite) to 71% (rhyolite) vol. SiO2, with significant linear correlations between major element-oxide and trace-element concentrations. 87Sr/86Sr isotope ratios range from 0.7070 to 0.7075, in- dicating that Paniri, similar to other volcanoes of the San Pedro – Linzor volcanic chain, have undergone sig- nificant crustal contamination of its parental magmas. However, the almost constant Sr-isotope compositions of the different volcanic units defined for Paniri volcano, suggested later fractional crystallization of magmas at upper crustal levels. 1. Introduction migration of the associated volcanic front occurred. Migration of this volcanic front has been attributed to: (a) changes in the subduction The Central Andean volcanic arc (hereafter Central Andes) is lo- angle of the Nazca Plate during the last 200 Ma (Coira et al., 1982; cated at the western margin of South America from 14ºS to 27ºS. The Scheuber and Reutter, 1992); and, (b) subduction erosion that affected Central Andes was constructed through the eastward subduction of the the leading edge of the upper plate in this zone (Stern, 1991; Ranero Nazca Plate underneath South America Plate since Jurassic times (Coira et al., 2006; Goss and Kay, 2009). This has generated four distinctive et al., 1982). During the evolution of the Central Andes, an eastwards main magmatic arcs, within which the actual volcanic front - coined the ∗ Corresponding author. E-mail address: [email protected] (B. Godoy). 1 Present address: Amec Foster Wheeler. Apoquindo 3846, piso 11, Las Condes, Chile. 2 Present address: Advanced Mining Technology Center, Avenida Tupper 2007, Santiago, Chile. 3 Present address: Servicio Nacional de Geología y Minería. Avenida Santa María 0104, Providencia, Santiago, Chile. https://doi.org/10.1016/j.jsames.2018.03.013 Received 3 November 2017; Received in revised form 14 March 2018; Accepted 19 March 2018 Available online 22 March 2018 0895-9811/ © 2018 Elsevier Ltd. All rights reserved. B. Godoy et al. Journal of South American Earth Sciences 84 (2018) 184–200 Fig. 1. Satellite image (Google Earth™) showing distribution of the main volcanic and structural features of the San Pedro – Linzor volcanic chain. Inset shows Global Multi-Resolution Topography image showing location of the satellite image. Aucanquilcha, Ollagüe, Paniri, Uturuncu, Licancabur and Lascar volcanoes, and Lípez- Coranzuli and Calama-Olacapato-El Toro lineaments are shown as reference. Dotted blue line represents extend of the Altiplano-Puna Volcanic Complex (APVC; de Silva, 1989a) in the area. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.) Andean Central Volcanic Zone – has been active since the Upper Oli- detailed discussion on processes of magma generation, storage condi- gocene (Coira et al., 1982). tions, and eruption dynamics is beyond the scope of this paper. The Central Volcanic Zone has been built on continental crust which is up to 70 km thick (Beck et al., 1996; Yuan et al., 2002). A felsic upper 2. Geological background crust (Lucassen et al., 2001) is proposed to exist up to a depth of 50 km below the Altiplano region, underlain by a mafic lower crust (Yuan Paniri (22º03′S 68º14′W) is a NW-SE aligned volcano located within et al., 2002). The thickness of the mafic lower crust in the Central Andes the Altiplano-Puna volcanic complex (Fig. 1), overlying Miocene decreases from less than 30 km below the Altiplano, to less than 25 km rhyodacitic-to-rhyolitic ignimbrite fields (Ramírez and Huete, 1981; below the northern Puna, and less than 20 km below the southern Puna Marinovic and Lahsen, 1984; O'Callaghan and Francis, 1986; de Silva, (Prezzi et al., 2009). 1989b; Salisbury et al., 2011) and Oligocene - Lower Miocene volcano- The Central Volcanic Zone is an active volcano-tectonic province of sedimentary sequence (San Pedro Formation) that outcrops further the Central Andes containing at least 15 active volcanoes (Simkin and south (Dingman, 1967; Marinovic and Lahsen, 1984). Paniri volcano Siebert, 1984; Francis and de Silva, 1989; de Silva and Francis, 1991), shows lobate thick lava flows at its base, and NE-SW oriented lobate for example Sabancaya (Samaniego et al., 2016), Ubinas (Thouret et al., lavas flowing from its summit (Fig. 1). The basement below Parini 2005; Rivera et al., 2014) and Lascar stratovolcano (Matthews et al., belongs to the Antofalla Domain, which corresponds to one of the Pa- 1997)(Fig. 1), as well as volcanoes with fumarolic activity (e.g. Ol- leozoic terrains accreted during Central Andean evolution (Mamani lagüe, Feeley et al., 1993; San Pedro, Francis et al., 1974; Lastarria, et al., 2008; Ramos, 2008, and references therein). This terrain makes Aguilera et al., 2011). Additionally, important geothermal fields are up the felsic upper crust basement of the Central Volcanic Zone, with present in this zone (e.g. El Tatio, Sol de Mañana, Apacheta; Delgadillo characteristic radiogenic 206Pb/204Pb values > 18.551 (Aitcheson Terceros, 2000; Urzua et al., 2002; Lahsen et al., 2010; Lahsen et al., et al., 1995; Mamani et al., 2008). 2015). Paniri volcano is part of the NW-SE oriented San Pedro – Linzor Paniri is a Pleistocene stratovolcano (Marinovic and Lahsen, 1984; volcanic chain (Fig. 1; Godoy et al., 2014), which is made of basaltic- Godoy et al., 2017) located within the Altiplano-Puna Volcanic Com- andesite, hornblende-dacite lava flows, dacitic pyroclastic flows, and plex (sensu de Silva, 1989a)(Fig. 1). It forms part of a NNW-SSE volcanic basaltic-andesite to andesitic scoria flows (Ramírez and Huete, 1981; chain, oblique to the Andean trending direction. Paniri is a potentially Marinovic and Lahsen, 1984; O'Callaghan and Francis, 1986; Lazcano active volcano (Francis and de Silva, 1989), as indicated by the pre- et al., 2012; López et al., 2012; Polanco et al., 2012; Silva et al., 2012; sence of uneroded lavas, a small scoria cone on the extreme summit, López, 2014; Martínez, 2014; Silva, 2015; Lazcano, 2016; Sellés and and a well-preserved summit crater. Gardeweg, 2017). The volcanic chain also includes the Holocene Chil- The aim of this work is to present the volcanological evolution of lahuita and Chao Dacite domes of dacitic to rhyodacitic composition Paniri, focusing on the sequence of the main eruptive events of the (de Silva and Francis, 1991; de Silva et al., 1994; Tierney et al., 2016), volcano. Thus, we present new petrographic, stratigraphic, together and the isolated ∼ 100 ka old La Poruña