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Journal of South American Earth Sciences 84 (2018) 184–200

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Journal of South American Earth Sciences

journal homepage: www.elsevier.com/locate/jsames

Geological evolution of , Central , northern 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, , Chile b Departamento de Ciencias Geológicas, Facultad de Ingeniería y Ciencias Geológicas, Universidad Católica del Norte. Avenida Angamos 0610, , 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., 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 fractionation stages occurring over more than 1 Myr: 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). flows from Paniri show abundant plagioclase together with subordinate ortho-, and clino-, and as main . Moreover, although true are scarce in the Central Andes, -bearing were erupted at Paniri at ∼400 ka. Also, scarce phenocrysts of , , rutile, and opaque (Fe-Ti ) 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 clasts up to 5 cm in diameter. Both pyroclastic deposits are composed of glassy groundmass (up to 80% vol.), and subordinated plagioclase, , 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-) to 71% () vol. SiO2, with significant linear correlations between major element- and trace-element concentrations. 87Sr/86Sr ratios range from 0.7070 to 0.7075, in- dicating that Paniri, similar to other volcanoes of the San Pedro – volcanic chain, have undergone sig- nificant crustal contamination of its parental . 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 The Central Andean (hereafter Central Andes) is lo- angle of the during the last 200 Ma (Coira et al., 1982; cated at the western margin of from 14ºS to 27ºS. The Scheuber and Reutter, 1992); and, (b) subduction 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 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 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. , Ollagüe, Paniri, , and volcanoes, and Lípez- Coranzuli and Calama-Olacapato-El Toro lineaments are shown as reference. Dotted blue line represents extend of the -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 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 which is up to 70 km thick (Beck et al., 1996; Yuan et al., 2002). A 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 decreases from less than 30 km below the Altiplano, to less than 25 km rhyodacitic-to-rhyolitic 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 - 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 (Samaniego et al., 2016), (Thouret et al., lavas flowing from its summit (Fig. 1). The below Parini 2005; Rivera et al., 2014) and Lascar (Matthews et al., belongs to the 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; , et al., 2008; Ramos, 2008, and references therein). This terrain makes 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. , 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 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- 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 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 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 basaltic-andesite scoria cone with available 40Ar/39Ar and K/Ar ages of different volcanic units, and related lava flows (O'Callaghan and Francis, 1986; Wörner et al., which allow us to characterize the different stages that generated Paniri 2000; Godoy et al., 2014; Bertin and Amigo, 2015; Marín et al., 2015). volcano. We also present the volume of erupted material to determine Additionally, El Rojo III, a small of deeply weathered and the eruptive rate at which this material was delivered to the surface. oxidized basaltic-andesite scoria (Godoy et al., 2014), occurs at the base Although new geochemical and Sr isotope data are presented, they are of a deeply dissected Cerro Carcanal volcanic structure of Miocene age used for better constraint the volcanological evolution of Paniri. Thus, a (de Silva, 1989b)(Fig. 1). The San Pedro – Linzor volcanic chain has

185 B. Godoy et al. Journal of South American Earth Sciences 84 (2018) 184–200 been identified as an off-set to the N-S trending volcanism of the Central obtained by Mass Spec software ( 1). Crushing, groundmass and Andes. Godoy et al. (2014) suggested that eruption of the volcanic separation, sample preparation, and analysis were carried out chain is probably controlled by the presence of extensional NNW-SSE following the procedures and parameters established in Arancibia et al. faults (i.e. , Giambiagi et al., 2015), as well as the Lípez- (2006). Coranzuli and Calama-Olacapato-El Toro regional lineaments affecting rocks (Salfity, 1985; Marrett et al., 1994; Riller et al., 2001; 3.3. vol estimates Tibaldi et al., 2009). The mentioned extensional regime would have been generated by a change in the orientation of the greatest and least To calculate the total volume of the volcanic edifice, the principal stress directions since Late Miocene (Marrett and Emerman, Triangulated Surface (3D Analyst Tools) tool of the Arc Toolbox catalog 1992; Riller et al., 2001; Zandt et al., 2003; Tibaldi et al., 2009; (ArcGIS™ software) was used in conjuction with ASTER Global Digital Giambiagi et al., 2015). Elevation Model (GDEM) data, a product of NASA and METI, freely distributed by USGS EarthExplorer (http://earthexplorer.usgs.gov). 3. Analytical work This image presents a 70 ± 6 m pixel resolution, and a topographic coverage with 15 m elevation error (Tachikawa et al., 2011). The de- 3.1. Geochemical and isotopic analyses fault nearest-neighbor interpolation of the program was used, which yields results with calculated error of 5%, as obtained for another GIS- New geochemical (twenty-two) and isotope (fourteen) analyses based volume at Central Andes (e.g. Rodríguez et al., 2015). For volume were carried out at the Department of Geological Sciences, University of calculations the surface boundaries to analyze were manually defined, Cape Town (UCT), South Africa. These unaltered samples were col- and not by computer-based code and/or algorithm (e.g. Grosse et al., lected, crushed in a jaw crusher and powdered in agate mill. Analyses of 2012; Euillades et al., 2013), considering i) the mor- major element oxides at UCT were made by X-Ray Fluorescence spec- phology (complex massif sensu Grosse et al., 2012), including slope troscopy (XRF) and trace element abundances by Inductively Coupled changes and proximities of another volcano structures (e.g. Chao Da- Plasma Mass Spectrometry (ICP-MS), following procedures, standards cite, Cerro del León volcano); ii) the geological information obtained and parameters detailed in Frimmel et al. (2001). Analysis of Sr-iso- during field trip campaigns; and iii) the remote sensing information, topes of six samples were measured at UCT by Multi Collector (MC)- using ASTER DEM and Landsat Satellite images (e.g. Google EarthTM). ICP-MS. Sample preparation and equipment conditions for these ana- Different surface boundaries, and the generated TIN model by Data lyses are detailed in Harris et al. (2015). Analytical errors (2 S.D.) Management (3D Analyst Tools) tool of the Arc Toolbox catalog are were < 2% for XRF, < 3% for ICP-MS and < 0.003% for 87Sr/86Sr ra- shown on Fig. 2a. Volumes of the TIN model over the geological extent tios. and the DEM-based surface boundaries (Fig. 2a) were calculated using Additionally, two geochemical and one isotopic analyses were car- minimum (H min), maximum (H max), and average (H mean) heights ried out at Activation Laboratories Ltda. (Actlabs; Canada) by in- (Table 2) considering the minimum, maximum and average altitude ductively coupled plasma-optical emission spectrometry (ICP-OES; values of selected points using the nearest topographic contour lines. major oxides), ICP-MS (trace elements), and TIMS (Sr- and Nd-) For volume estimation of different units of Paniri volcano we use a with equipment and procedures as described in Godoy et al. (2017). similar geometric approach as for calculating volume in another vol- Analytical errors (2 SD) are < 2% for ICP-OES and ICP-MS, and < canic edifices (e.g. Samaniego et al., 2016). In this case, we use the 0.004% for TIMS. Further information about analytical procedure, formula for the volume for an elliptical cone equipment and uncertainties are available at: http://www.actlabs.com. V=(π*h*R *r )/3, a truncated elliptical cone Results of new and previous published geochemical and isotopic 1 1 analyses are shown in Supplementary Table 1. V=π*h*[(2*R1-R2)*r1+(2*R2-R1)*r2]/6, and an elliptical cylinder

3.2. Geochronology V=π*h*R1*r1

40 39 A new Ar/ Ar step-heating plateau age was obtained by step- Where π corresponds to Pi number (3.14159), and h is the height, R1 is heating geochronological analysis by Argus VI multi-collector noble gas the longest basal and r1 the shortest basal radius, and R2 the longest top mass spectrometer at Servicio Nacional de Geología y Minería, Chile and r2 the shortest top radius of the figure. Calculations were made with (SERNAGEOMIN) on unaltered groundmass, using plateau ages radii horizontally measured using remote sensing (e.g. ASTER DEM and

Table 1 Summary of the PANI 16 04 40Ar/39Ar step-heating data, and plateau ages obtained from Servicio Nacional de Geología y Minería (Chile).

Watts 40Ar/39Ar 36Ar/39Ar 40Ar (%) Ca/K 39Ar (%) Age (ka) error (1σ)

A 0.3 0.22238 0.005751 11.8 0.63412 2.5 557.45 46.75 B 0 0.07048 0.001707 12.5 0.23244 5.2 176.69 10.6 C 0.7 0.06915 0.000912 21.7 0.40813 11.8 173.36 5.05 D 0.9 0.06626 0.003849 5.6 0.54064 8.5 166.11 10.91 E 1.2 0.06996 0.003221 7 0.55661 14.7 175.38 8.07 F 1.5 0.06563 0.002 10.4 0.5556 14.7 164.53 6.04 G 1.9 0.06682 0.001585 13.2 0.57505 20.3 167.51 4.68 H 2.3 0.06452 0.002166 9.6 0.63714 14.7 161.76 6.52 I 2.8 0.06633 0.005653 3.9 0.72931 7.6 166.29 18.24

Integrated Age Age Spectrum (Plateau)

Age (ka) Error (1σ) Age (ka) Error (1σ) 39Ar (%) n## (*)

176.3 6.5 168.7 4.8 97.5 8 0.55 (*) MSWD - mean square of weighted deviates. ## Number of data points used in plateau and isochron calculations; each step heating represents one data point.

186 B. Godoy et al. Journal of South American Earth Sciences 84 (2018) 184–200

Fig. 2. a) ASTER Global Digital Elevation Model (GDEM) image of Paniri volcano and neighboring volcanic structures from which the estimated GIS-based volumeof the volcano was calculated. Irregular contours indicate baseline for volume calculations (Table 2). Blue elliptical contour as reference for figure b. b) Satellite Image (Google Earth™) of the same location indicating extend of the main volcanic units of Paniri volcano for volume calculation by geometric approach (Table 3). Length of maximum and minimum axes on kilometers (km). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Landsat Satellite) (Fig. 2b) and heights accordingly to data obtained Table 3 during field campaigns and profile sections (Table 3). Volume estimated by geometric approach for each unit of Paniri volcano. Also, we performed volume calculations for different isolated lava V4500 indicates volume over the 4500 m a.s.l. contour line. fl ows at the volcano using the formula for the volume of a triangular Unit Geometric approach H (km) Volume (km3) V 4500 prism Malku Truncated elliptical cone 0.05 14.67 – V = b*h*l/2 Los Gordos Truncated elliptical cone 0.2 32.39 – Las Lenguas Truncated elliptical cone 0.1 7.62 – Where b is the widest extent of the flow (base), l is the length of the Las Negras Triangular prism 0.03 0.18 – flow perpendicularly measured from the estimated eruptive vent to b, Viscacha Truncated elliptical cone 0.9 10.45 10.45 and h is the average thickness of the flow (Table 3). Laguna Elliptical cone (half) 0.9 2.94 2.94 Elliptical cylinder 0.9 6.61 6.61 Llareta Triangular prism 0.2 3.88 1.72 Triangular prism 0.2 1.14 0.49 4. Results Total Volume 79.71 22.21 4.1. General Calculated GIS-based calculated volume 4500 (Table 2) 21.36 RSE (%) 3.98 The geological map of Paniri volcano is presented in Fig. 3. Similar to other volcanic edifices in the Central Andes of northern Chile (e.g. San Pedro, O'Callaghan and Francis, 1986; Lascar, Gardeweg et al., the volcano, between both previous generated craters (Fig. 4a). More- 1998), Paniri volcano is composed of two distinct structural units over, Crater II and III are covered by extensive lava flows erupted from showing a NW-SE orientation (Lazcano et al., 2012, Fig. 4a). The lower a volcanic vent (Fig. 4a). This vent, as well as Crater III, forms a small flows of Paniri volcano are highly eroded (Fig. 4b), with where Branchinecta brushi n. sp. was identified (Hegna and Lazo- deposits towards the northern part (Fig. 4a). The upper flows contain Wasem, 2010). The flows erupted from the volcanic vent exhibit levées deep gorges, generated by alluvial and glacial erosion (Fig. 4c). Paniri and ogives structures. volcano has three main craters on its summits (Fig. 4a). The SE crater (Crater I) is the oldest crater, showing deep glacial and alluvial erosion. Towards the NW, a second crater (Crater II) shows significant hydro- thermal alteration (Fig. 4b). A new crater (Crater III) was built on top of

Table 2 GIS-based volume estimate for Paniri volcano. Hmin, Hmean and Hmax refers to minimum, average and maximum heights of the surface boundary, respectively.

Surface Boundary Hmin (m) Hmean (m) Hmax (m) Average Slope (%) Hmin volume (km3) Hmean volume (km3) Hmax volume (km3)

Geological extent 3100 3567 3800 2.14 300.09 179.81 125.56 DEM-based 3500 3768 3950 4.6 165.83 114.83 82.84 4000 contour level – 4000 – 0 – 70.74 – 4500 contour level – 4500 – 0 – 21.36 –

187 B. Godoy et al. Journal of South American Earth Sciences 84 (2018) 184–200

Fig. 3. Geological map from Paniri volcano and surrounding areas (after Lazcano, 2016). Geochronological data from this work (white triangles), Seelenfreund et al. (2009) (white squares), and Godoy et al. (2017) (white circles).

4.2. vol petrographic characteristics of the lava and pyroclastic flows from the different volcanic units, and Fig. 6 shows representative photo- Results of the obtained volume by the Triangulated Surface calcu- micrographies of selected lava samples of each unit of the volcano. lations are listed in Table 2. Except for data obtained using the 4500 m a.s.l. topographic contour baseline (Fig. 2a), all volumes include part of 4.3.1. Malku Unit (Pm) Chao Dacite (Fig. 2a). We calculated volumes by geometric approach of This unit is exposed to the NW of the volcanic edifice (Fig. 3), and is all the units of Paniri volcano (Table 3). When comparing the sum of composed mainly of eroded lava flows up to 6 m thick, reaching a total volume above the 4500 m a.s.l. topographic contour baseline with that thickness of 50 m. This unit is considered almost radially distributed obtained by the Triangulated Surface tool, a difference of ∼4% is ob- above the ignimbrite basement, with a maximum length of ∼12 km served (Table 3). Thus, we consider our geometrical approach as ac- from the volcanic vent (Fig. 2b). Malku Unit is covered by younger curate in determining the volume of each unit, and the total edifice, products of Paniri and by evaporite deposits (Fig. 4a). A thin layer avoiding GIS-generated overestimation due to the presence of older and (< 1 m) of an undifferentiated pyroclastic deposit is recognized within younger volcanic material within the area. this unit, thinning as this deposit moves away from the volcano. Bases on its probably distribution within the area (Fig. 2b), and the measured 4.3. Units from Paniri volcano thickness, a maximum volume of ∼14.7 km3 was calculated for this unit (Table 3). No geochronological dating has been performed on Based on field mapping, and remote sensing interpretation, seven Malku Unit. However, an age of 1.39 ± 0.28 Ma has been obtained for different units (described below) have been identified at Paniri volcano the Los Gordos Unit erupted after Malku Unit (Godoy et al., 2017). (Fig. 3). Geochemically, lavas from these units vary from basaltic-an- Thus, a minimum age of 1.39 ± 0.28 Ma is suggested for Malku Unit desite to rhyolite (Fig. 5a), with a main calc-alkaline trend (Fig. 5b). (Figs. 3 and 4) considered the first eruptive event of Paniri volcano. Ages for these units were obtained from published data in Seelenfreund Geochemically, Malku Unit vary from andesitic to trachy-dacitic et al. (2009) and Godoy et al. (2017), and the newly obtained 40Ar/39Ar composition (Fig. 5a, Supplementary Table 1). Lava flows show hypo- age for this volcano (Table 1). Table 4 summarizes all the main crystalline, microcrystalline, hypidiomorphic, porphyric, sieve,

188 B. Godoy et al. Journal of South American Earth Sciences 84 (2018) 184–200

Fig. 4. Photographies showing selected views of Paniri volcano. a) Panoramic view from the NE flank of Paniri. Location of the Old and New Cone, as well as the different craters and the eruptive vent is shown. Also, different units of the volcano, and hydrothermal alteration (Hy) are indicated. b) Panoramic view of the northern flank of Paniri volcano. In this photography, the thickness and high erosional features of Los Gordos Unit can be noticed. c) Panoramic view of the north- eastern flank of Paniri volcano where glacial erosion and deposits are shown. d-f) Different panoramic views showing stratigraphic sequence of the volcanic units of Paniri volcano. Pm –Malku, Pg – Los Gordos, Ple – Las Lenguas, Pn – Las Negras, Pv – Viscacha, Pla – Laguna, and Pll – Llareta units, respectively. trachytic, intergranular, and vesicular textures. Plagioclase is the main ∼32.4 km3 for this unit (Table 3). This unit is exposed towards the N phase, reaching up to 24% vol. of the analyzed lavas and NW flanks of the volcano, overlying the Sifón Ignimbrite (9.0 Ma, (Table 4), showing argillaceous alteration, and sieve textures (Fig. 6a). Marinovic and Lahsen, 1984; de Silva, 1989b) and the Malku Unit Clinopyroxene, orthopyroxene, and opaque minerals are also present as (Figs. 3 and 4b). An age of 1.39 ± 0.28 Ma was obtained by the phenocrysts (Fig. 6a; Table 4). Groundmass comprises up to 65% vol. of 40Ar/39Ar method on amphibole minerals from a lava flow of this unit the lavas, and it is composed of plagioclase, clinopyroxene and glass (Godoy et al., 2017). Moreover, a minimum age of 0.8 Ma is assigned to (Fig. 6a; Table 4). The undifferentiated pyroclastic deposit is made up this unit, based on ages obtained for the subsequently erupted Las of pumiceous material. This material is moderately sorted, with clast Lenguas Unit (Figs. 3 and 4). diameters between 2 and 5 cm. Pumice are scarcely vesiculated, Lava flows from Los Gordos Unit are dacitic in composition (Fig. 5a, showing a vitreous groundmass (up to 85% vol.; Fig. 6b). Plagioclase Supplementary Table 1), with porphyric, hypocrystalline, hypidio- and hornblende are observed as phenocrysts and microlites in the pu- morphic, vesicular, and vitrophyric textures. These lava flows contain miceous material (Table 4; Fig. 6b). up to 15% vol. of plagioclase phenocrysts (Table 4). These phenocrysts show disequilibrium textures (reabsorption and sieve; Fig. 6c), as well 4.3.2. Los Gordos unit (Pg) as scarce argillaceous and chlorite-epidote alterations (Fig. 6c). Horn- Los Gordos Unit is made up of blocky and autobrecciated lava flows, blende, orthopyroxene, clinopyroxene, and opaque minerals are also and pyroclastic deposits. The lava flows are thick (up to 70 m; Fig. 4d), recognized as phenocrysts (Table 4). Groundmass (up to 75% vol.) is resulting in a maximum thickness of 300 m, with an average thickness composed of glass, and plagioclase and pyroxene microlites (Table 4). of 200 m for this unit. These flows extend almost radially up to ∼9km Andesitic inclusions (< 2% vol.) have been identified in some lava from the volcanic vent (Fig. 2b), giving a maximum volume of samples from this unit. Pyroclastic deposits are composed of -

189 B. Godoy et al. Journal of South American Earth Sciences 84 (2018) 184–200

Fig. 5. a) Total Alkali vs Silica (TAS) and b) AFM diagrams for analyzed samples of Paniri volcano (after Irvine and Baragar, 1971). In a) grey area indicates the main distribution of lavas at Central Volcanic Zone (after Mamani et al., 2010). sized fragments. As on Malku Unit, these fragments are made up of a is composed of glass, and plagioclase and clinopyroxene microlites glassy groundmass, with plagioclase and hornblende phenocrysts and (Table 4). Pyroclastic deposits are glass-rich (> 80% vol.) consolidated microlites (Table 4). dacitic , with plagioclase, hornblende, and biotite (Table 4).

4.3.3. Las Lenguas unit (Ple) Las Lenguas Unit occurs widely in the study area, reaching distances 4.3.4. Las Negras unit (Pn) between 5 and 12 km from the volcanic vent (Fig. 2b). This unit covers This unit appears as isolated lava flows at the northwestern flank of essentially mostly all the flows from the Malku and Los Gordos units Crater II of Paniri volcano (Figs. 3 and 4). These flows show levées (Figs. 3 and 4). Las Lenguas Unit is composed of several blocky lava structures, and have an average thickness of 30 m, reaching a maximum flows, with flow-banding textures, up to 50 m thick, and scarce thin extent of 5.5 km from the volcano. An estimated total volume of (< 1 m) bedded tephra pyroclastic deposits, generating a maximum 0.18 km3 has been calculated for this unit (Table 4). These flows have volume of 7.6 km3 (Table 3). This unit is partially covered by the Vis- compositions that vary from basaltic-andesite to andesite (Fig. 5a, cachas, Laguna, and Llareta units (Figs. 3 and 4). 40Ar/39Ar dating on Supplementary Table 1). An 40Ar/39Ar age of 402 ± 46 ka was ob- from lavas of this unit give ages of 640 ± 140 ka and tained from one lava flow from this unit (Godoy et al., 2017)(Fig. 3). 620 ± 90 ka (Godoy et al., 2017), while K/Ar ages of 400 ± 100 ka Petrographically, these flows are olivine-bearing basalts to two- and 500 ± 100 ka have also been obtained (Seelenfreund et al., 2009). pyroxene with porphyric, hypocrystalline, and glomer- Lava flows of Las Lenguas Unit have andesitic to dacitic composi- oporphyric textures. , showing skeletal and reabsorption tex- tions (Fig. 5a; Supplementary Table 1). Petrographically, lava flows tures (Fig. 6e), and plagioclase, with sieve and reabsorption textures, show porphyric, hypocrystalline, and glomeroporphyric textures. Phe- are the main phenocrysts phases (Table 4). Also, ortho- and clino-pyr- nocrysts phases are mainly plagioclase, and ortho- and clino-pyroxene oxenes, biotite with oxidized rims, hornblende, rutile, and opaque mi- (Fig. 6d; Table 4). Also, biotite, and hornblende with oxidized rims are nerals are identified as phenocrysts in lava flows from this unit recognized in some lava flows (Table 4). Groundmass (up to 60% vol.) (Table 4). These minerals occur in a groundmass made up of glass, and

Table 4 Modal mineralogical composition (% vol.) of analyzed samples at Paniri volcano. Ol – Olivine, Plg – Plagioclase, Opx – Orthopyroxene, Cpx – Clinopyroxene, Qz – Quartz, Bt – Biotite, Hbl – Hornblende, Rut – Rutile, Op – Opaque minerals, Inc – Andesitic inclusions.

Unit Volcanic Phase Groundmass Phenocrysts Inc

Crysts Glass Ol Plg Opx Cpx Qz Bt Hbl Rut Op

Malku (Pm) Lava flows 15–20 40–50 < 24 2 6–8 Pyroclastic flows 5 < 85 6–8<5

Los Gordos (Pg) Lava flows 23 < 40 15–20 <5 <2 <12 1 <2 Pyroclastic flows 5–10 < 80 8–10 2

Las Lenguas (Ple) Lava flows 20–25 < 40 < 20 6–83–5<3<5 <1 Pyroclastic flows 3–5 > 80 5–7<2<5

Las Negras Lava flows < 44 < 15 < 5 20–25 3–52–4<31<1<11

Viscacha (Pv) Lava flows < 20 < 44 20–25 5–82–5<21 2 1 1 1

Laguna (Pla) Lava flows < 35 < 40 15–20 2–62 Pyroclastic flows > 5 > 70 15 5 5

Llareta (Pll) Lava flows < 28 25–30 < 28 8–10 2–5<21 Andesitic bombs 15–20 < 65 5–85 3

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(caption on next page)

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Fig. 6. Photomicrographies showing distinctive characteristics of lavas and pyroclastic flows at Paniri Volcano. Plagioclase (plg) constitutes the main mineralogical phase, showing sieve and reabsorption textures, and scarce epidote (ep) alteration. Ortho- (opx) and clino-pyroxene (cpx) are the main mafic phases. Also hornblende (hbl) with reaction rims, and skeletal and reabsorbed olivine (ol) phenocrysts are recognized in different units of the volcano. The groundmass is mostly glassy, with plagioclase and pyroxene microlites. a-b) Lava and pyroclastic flows from Malku Unit, respectively. c) Representative dacitic lava sample form Los Gordos Unit. d) Lava flow from Las Lenguas Unit. e-f) Representative sample of basaltic-andesite and dacitic lava flows from Las Negras and Viscacha units, respectively. g-h) Representative lava samples from Laguna and Llareta units, respectively. plagioclase and pyroxene microlites (Fig. 6e; Table 4). In addition, dacite (Fig. 5, Supplementary Table 1). Petrographically, they show andesitic inclusions have been recognized in lavas from this unit hypocrystalline, hypidiomorphic, porphyric, and glomeroporphyric (Table 4). textures. Fractured, sieved, and argillaceous plagioclase are the main phenocryst phase (< 28% vol.) (Fig. 6h; Table 4). Also, ortho-, and fi 4.3.5. Viscachas unit (Pv) clino-pyroxene and hornblende are identi ed as phenocrysts (Fig. 6h; This unit corresponds to lava flows that make up the southeastern Table 4). Glass, plagioclase, and constitute the groundmass volcanic edifice, overlying the Las Lenguas and Las Negras units (Figs. 3 (< 60% vol.) (Fig. 6h; Table 4). Andesitic pyroclastic bombs are vesi- and 4). The lava flows of this unit have a maximum thickness of 20 m. cular and more aphanitic, with plagioclase, and ortho- and clino-pyr- The bulk thickness, and the estimated extend (Fig. 2b), give to this unit oxene phenocrysts, and a glassy groundmass (< 85% vol.) with plagi- a maximum volume of 10.5 km3 (Table 3). Results of 40Ar/39Ar and K/ oclase, clinopyroxene and apatite microlites (Table 4). Ar dating of lavas from this unit gave ages of 325 ± 8 ka (Godoy et al., 2017) and 300 ± 100 ka (Seelenfreund et al., 2009), respectively (Fig. 3). 4.3.8. (Hmo) Analyzed lava flows have dacitic to rhyolitic compositions (Fig. 5; These correspond to chaotic unconsolidated deposits located on the fl Supplementary Table 1) with flow banding textures and andesitic in- upper anks of Paniri volcano (Fig. 4c), and were generated by glacial clusions. Analyzed samples of this unit exhibit hypidiomorphic, hypo- erosion of lavas from Viscacha, Laguna, and Llareta units. An estimated 3 crystalline, porphyric, and glomeroporphyric textures. Plagioclase, volume of 0.2 km has been obtained for moraines deposits at Paniri ortho- and clino-pyroxene, and hornblende are recognized as dominant volcano. phenocryst phases (Fig. 6f; Table 4). Scarce quartz, rutile and biotite are also identified (Table 4). Plagioclase and clinopyroxene microlites, and glass constitute the groundmass of the samples (Table 4). 4.4. Whole rock

This section presents new geochemical and isotopic data for Paniri 4.3.6. Laguna Unit (Pla) volcano (Supplementary Table 1), within the context of previous geo- Laguna Unit is made up of lava and pyroclastic deposits. These flows chemical and isotopic studies from the San Pedro – Linzor volcanic are distributed mainly along the northwestern flank of the volcano, chain (Polanco et al., 2012; Godoy et al., 2014, 2017). overlying the Malku, Los Gordos, Las Lenguas, Las Negras, and Viscacha Lavas from Paniri volcano correspond to a high-K calc-alkaline units (Figs. 3 and 4). This unit has scarce hydrothermal alteration series (after Gill, 1981), with increasing K O from ∼1.5 to ∼3.8 wt. % (Fig. 5c), with clay minerals () replacing . Juvenile 2 with differentiation (Fig. 7a). Na O contents of the samples, which fragments of pyroclastic deposits show breadcrust textures whilst au- 2 show little variation with differentiation, are in the range 3.3–4.0 wt. % tobreccia textures are recognized in lava flows. Based on its mor- (Fig. 7b). The analyzed lavas also show decreasing FeOt, MgO, CaO and phology and extent (Fig. 2b), a maximum volume of 9.6 km3 is sug- Al O with increasing SiO content (Fig. 7). The Mg# of the samples gested for this unit (Table 3). A new geochronological analysis of one 2 3 2 vary from 36 to 65, with the Malku, Laguna and Llareta Units showing lava from this unit gave an age of 169 ± 5 ka (Table 1). greater variability in Mg# content (Table 1). The Las Negras Unit Lavas of this unit have dacitic compositions (Fig. 5; Supplementary (sample PANI-12-13) shows the highest MgO and FeOt content Table 1) with hypocrystalline, hypidiomorphic, porphyric, glomer- (Supplementary Table 1; Fig. 7), together with the highest Ni and Cr, oporphyric and hyalopilitic textures. The samples are mainly made up and lowest Rb and Ba content (Supplementary Table 1; Fig. 8). of groundmass (up to 75% vol.) with plagioclase microlites and glass Trace element compositions of each unit of the Paniri volcano show (Fig. 6g; Table 4). Plagioclase, and ortho- and clino-pyroxene are the the following: i) an increase of Rb (41–199 ppm) with differentiation main phenocryst phases (Table 4). Andesitic inclusions (< 2% vol.) (increasing SiO )(Fig. 8b); ii) except for one sample from Las Negras were also recognized in analyzed lava samples. Pyroclastic dacitic de- 2 Unit, Sr decrease (663–310 ppm) with increasing SiO (Fig. 8c); and iii) posits are composed of ash-to-lapilli sized fragments made up of glass 2 Cr has a single behavior decreasing from 102 to 5 ppm with increasing (> 70% vol.), with plagioclase, amphibole, and biotite crystals SiO content (wt. %) (Fig. 8d). Sampled lavas show an increase in Zr (Table 4). 2 content, in the first stages of differentiation, but lavas with

SiO2 > 64 wt. % show no correlation between both these components 4.3.7. Llareta Unit (Pll) (Fig. 8f). Sr/Y and Sm/Yb ratios of the sampled lavas vary from 14.3 to This unit refers to lobate lavas erupted from the last active volcanic 50, and 2.01 to 3.61, respectively (Supplementary Table 1). vent, flowing to the northeastern and southwestern flanks of the vol- Fig. 9 shows the variation of Sr isotope ratios with SiO2. The cano (Figs. 3 and 4). The northeastern flow extends over 8 km, while 87Sr/86Sr ratios vary from 0.7066 to ca. 0.708, with a main linear trend the southwestern flow reaches distances of up to 10 km (Fig. 3). Both in 87Sr/86Sr between 0.7070 and 0.7075 with silica content between 60 flows overlie the Las Lenguas, Las Negras, Viscacha, and Laguna units 87 86 and 68 wt. % (Fig. 9). However, an increas in Sr/ Sr with SiO2 (Fig. 3), and are up to 40 m thick, showing autobrecciated textures. A composition is observed in lavas from Viscacha and Las Lenguas units, maximum volume of 5.0 km3 has been estimated for this unit (Table 3). 87 86 whilst Las Negras Unit has the lowest Sr/ Sr and SiO2 values (Fig. 9). In addition, pyroclastic bombs, up to 2 m in length, cover these thick 143Nd/144Nd ratios vary from 0.512268 to 0.512366 (Supplementary lobate flows, constituting the last activity of Paniri volcano (Francis and Table 1). An inverse correlation is recognized when comparing de Silva, 1989; de Silva and Francis, 1991). Published geochronological 143Nd/144Nd with 87Sr/86Sr ratios, i.e. increasing Sr-isotope ratios with 40 39 data for this unit indicate Ar/ Ar ages of 150 ± 6, 164 ± 3 ka, and decreasing 143Nd/144Nd composition of the analyzed samples (Fig. 10). 264 ± 99 ka (Godoy et al., 2017). The lavas of this unit have compositions varying from andesite to

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Fig. 7. Selected Harker diagrams for major oxides from sampled lavas of Paniri volcano. For a) lines and nomenclature after Rickwood (1989).

5. Discussion of 8% for the lower parts of Paniri (4.4 km3) and erosion of a maximum of 1 km3 (degree of denudation of 4%), including glacial action, for the 5.1. Volume estimation and eruption rates upper units of the volcano. Thus, a maximum of 85.3 km3 is proposed to have been erupted by Paniri volcano during its evolution. This value is A total volume of 79.9 km3 has been calculated by geometric ap- similar to the volume estimated for Ollagüe volcano (Feeley and proach for Paniri volcano (Table 3). Compared to the whole edifice, the Davidson, 1994), located further north (Fig. 11a). When using the total volume of glacial deposits (0.2 km3) is minimal, affecting only the oldest obtained age (1.39 ± 0.28 Ma), Paniri volcano had a bulk upper parts of the volcano (Fig. 4c). eruption rate of 0.061 km3/ka (Fig. 11b). This value is similar to that Karátson et al. (2012) had estimated an erosion volume of ca. 4 km³ obtained for the -Sabancaya volcanic complex (Samaniego for volcanoes with ages < 400 ka (Ollagüe and Tacora). Moreover, a et al., 2016), and comparable with those from another silicic volcanic volume of erosion of 3.8 km³ was estimated by the same authors for systems in continental arc settings (0.04–0.2 km3/ka) (Samaniego et al., Araral volcano (2.75 ± 0.04 Ma, Sellés and Gardeweg, 2017), located 2016, and references therein). to the north of Paniri volcano. However, the degree of denudation is different for each volcano at Central Andes, increasing with time from < 1% (Aracar volcano; < 1 ka) to ∼50% (Jatunpunco; 5.2. Magmatic processes 14.35 ± 0.7 Ma) (Karátson et al., 2012). As recognized at Paniri, the lower, and older (> 600 ka), units show higher degrees of denudation The main petrological-geochemical results, and the local petrolo- than the upper parts of the volcano (Fig. 4b). Taking this into account, gical context related to this volcano build on previous detailed geo- – and the ages of the different units, we propose a degree of denudation chemical studies related to evolution of the San Pedro Linzor volcanic chain (Polanco et al., 2012; Godoy et al., 2014, 2017). For this volcanic

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Fig. 8. Selected Harker diagrams for trace elements of analyzed lavas from Paniri volcano.

chain, a low pressure evolution has been established, indicating con- tamination of primary mafic magmas with a partially molten layer at shallow crustal levels (Godoy et al., 2014, 2017). Godoy et al. (2017) indicated that the primary mafic magmas are related to the basaltic- andesite (BA), and the upper crustal partially molten material corre- sponds to the shallow rhyodacitic (RD) end-members of Blum-Oeste and Wörner (2016). Lavas from Paniri volcano show almost linear trends between

major- and trace-element versus SiO2 content (Figs. 7 and 8). This suggests a co-magmatic suite during differentiation of erupted lavas. Moreover, analyzed samples of Paniri volcano show low 87Sr/86Sr ratios relative to other volcanoes from the San Pedro – Linzor volcanic chain, and other volcanoes erupted at the Altiplano – Puna Volcanic Complex (Fig. 10)(Godoy et al., 2017). Using AFC models (DePaolo, 1981) 87 86 ff Fig. 9. Sr/ Sr vs. SiO2 (wt. %) diagram of lavas from di erent units of Paniri (Table 5) Godoy et al. (2017) suggested that assimilation of 12–23% of Volcano. Grey area represents the compositional variations of Central Volcanic crustal material in a -free crustal environment formed part of the Zone lavas (data from Mamani et al., 2010). magmatic evolution of Paniri volcano. After this, fractional - lization with plagioclase as the main crystallizing phase (Fig. 12), to- gether with crystallization of pyroxene ± olivine ± hornblende - as observed in the petrographic characteristics of erupted volcanic

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Fig. 10. 144Nd/143Nd vs. 87Sr/86Sr diagram showing (a) the decreasing on Nd-isotopes ratios with in- creasing Sr-isotopes ratios for different units of Paniri volcano. Inset (b) shows relationship of isotopic composition for Paniri with Central Andean lavas erupted within the Altiplano Puna Volcanic Complex (after Godoy et al., 2017). Data in inset: San Pedro – Linzor volcanic chain - Godoy et al. (2017); Au- canquilcha – Mamani et al. (2010), Walker (2011); Ollagüe – Feeley and Davidson (1994), Mamani et al. (2010); Uturuncu – Michelfelder et al. (2013); Lascar - Matthews et al. (1994), Mamani et al. (2010); Li- cancabur – Figueroa et al. (2009), Mamani et al. (2010).

products (Fig. 6) - controlled the magmatic evolution of Paniri volcano. 2018), and thermobarometric results (Godoy et al., 2012; Martínez, This suggests that geochemical and isotopic compositional variation of 2014). lavas at Paniri are related to magmatic evolution at low crustal pres- sures, as observed in another volcanoes located within the Altiplano- 5.3. Volcanic evolution Puna Volcanic Complex (e.g. Godoy et al., 2014; Burns et al., 2015). Thus, the first stage is crustal contamination involving the Altiplano – Paniri is a stratovolcano resulting from four main stages of evolu- Puna Magma Body (Fig. 10; Godoy et al., 2017), a partially molten layer tion. In chronological order, these stages are (I) Plateau Shield; (II) located at shallow upper crustal levels (Chmielowski et al., 1999; Ward Main Edifice; (III) Old Cone; and (IV) New Cone (Fig. 13). et al., 2014), from which dacitic domes located within the Altiplano- Puna volcanic complex (e.g. Chao Dacite) are the last eruptive products 5.3.1. Stage I – Plateau Shield (> 800ka) (Tierney et al., 2016). After that, in the second stage fractional crys- The first stage of the evolution of Paniri volcano is composed of the tallization of magmas at Paniri occurred in shallow magmatic chambers Mallku and Los Gordos Units (Fig. 13). This stage corresponds to (< 7 km depth). These shallow chambers have been identified by eruption of andesitic to dacitic lavas, and andesitic-to-dacitic pyr- magnetotelluric research (Mancini and Díaz, 2016; Mancini et al., oclastic flows (Fig. 5) forming a gently dipping highly-eroded plateau-

Fig. 11. a) Volume (km3) vs. Latitude (°) (after Rodríguez et al., 2015), and b) Cumulative Volume (km3) vs. Age (ka) diagrams. a) The diagram shows volume comparison of different volcanic edifices at Central Andes. Volume data from Feeley and Davidson (1994, Ollagüe), Matthews et al. (1994, Lascar), Richards and Villeneuve (2001, ), Clavero et al. (2004a, ; 2004b, ), Klemetti and Grunder (2008, Aucanquilcha), Naranjo (2010, Lastarria), and Rodríguez et al. (2015, ). b) The diagram shows duration of each stage determine by new and published ages of Paniri volcano. Also, an estimated bulk eruption rate for each stage is shown. For Plateau Shield Stage a maximum and minimum eruption rates are calculated accordingly to obtained age error for Los Gordos Unit (0.29 Ma).

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8) and lowest 87Sr/86Sr values (Figs. 9 and 12) for samples from Paniri volcano. The presence of olivine, and the geochemical and isotopic composition suggest decreasing crustal contamination during the magmatic evolution of Paniri volcano associated with the eruption of the Las Negras Unit (∼400 ka). Dating of lavas from this stage, and upper units (Godoy et al., 2017), gave an eruption duration of ca. 400 kyr. A minimum volume of ca. 8.4 km3 was erupted during this stage, giving a bulk eruption rate of 0.021 km3/ka during construction of the Main Edifice Stage (Fig. 11b). This corresponds to the lowest value recognized during the evolution of Paniri, related to the low volume of erupted material from the Las Negras Unit. (Table 3).

5.3.3. Stage III – Old Cone (400–250 ka) Fig. 12. 87Sr/86Sr vs Sr (ppm) diagram showing isotopic distribution of lavas This stage corresponds to the construction of the SE cone recognized from Paniri volcano. Line represents plagioclase-dominated AFC-type (DePaolo, fi 1981) evolution models from Godoy et al. (2017) taking into account samples on the volcanic edi ce (Figs. 4 and 13). It is characterized by lavas of from Sierra de Moreno basement (4/316; Lucassen et al., 2001), and Lascar dacitic to almost rhyolitic composition from the Viscacha Unit (Fig. 5). volcano (LA 123; Matthews et al., 1994) as contaminant and initial end-mem- These flows were erupted from Crater I, and are discordantly covered bers, respectively (Table 5). Mostly all analyzed samples follow a linear trend by new volcanic products from the New Cone Stage (Figs. 3 and 4). related similar to fractional crystallization (F.C.) path. Remaining melt fraction Geochemical and isotopic composition of analyzed samples from the (F) indicated by italic numbers. White arrows width is 0.0002 87Sr/86Sr ratio. D Viscacha Unit (Figs. 7–10) show an increase of Sr-isotope ratios with indicates bulk partitioning coefficient of Sr according to crystallizing mineral differentiation. This indicates that evolution of this unit was mainly assemblage of Table 5 (after Martínez, 2014; Lazcano, 2016; this work, controlled by an AFC-type process (Fig. 12). ffi Table 4), and mineral partitioning coe cients of Rollinson (1993). The Old Cone Stage construction lasted approximately 150 kyr. During this stage a minimum of ca. 10.9 km3 of material was erupted, like morphology outcropping mostly on the northern flank of the vol- giving an eruption rate of 0.073 km3/ka (Fig. 11b). cano (Figs. 3 and 4). Lavas and pyroclastic deposits of later stages of the evolution of Paniri now cover the previously formed shield-like an- 5.3.4. Stage IV – New Cone (250–100 ka) cestral cone (Fig. 13). Additionally, lavas from the Malku Unit are This stage corresponds to a north-westward migration of the erup- covered by evaporite deposits (Fig. 4b). Lavas from this tion vent and was characterized by construction of two different craters stage have similar Sr-isotope composition, suggesting that both units (Crater II and III; Figs. 3 and 13), giving rise to the Laguna Unit. After (Malku and Los Gordos) evolved mainly through fractional crystal- this, a new vent generated the extensive flows of the Llareta Unit lization (Fig. 12). (Figs. 3, 4 and 13). Volcanic products from this stage are mostly dacitic Ages obtained for Los Gordos Unit (Godoy et al., 2017) indicate that with some andesite lava flows, and pyroclastic bombs of basaltic-an- construction of Paniri started at least at 1.39 ± 0.28 Ma. This age is desitic to andesitic compositions (Fig. 5). Pyroclastic bombs are related similar to those obtained by Baker and Francis (1978), Seelenfreund to the eruption of a small scoria cone identified at the top of the vol- et al. (2009), and Godoy et al. (2017) for the lower flows of Toconce cano, corresponding to the last eruptive event of Paniri volcano (Francis and Cerro del Leon volcanoes, suggesting that eruption of this stage is and de Silva, 1989). not only related to the first stage of evolution of Paniri volcano, but also Geochemical and isotopic composition of analyzed samples show an – 87 86 of the San Pedro Linzor volcanic chain (Godoy et al., 2017). Ages from almost linear trend between Sr/ Sr and SiO2 (wt. %) (Fig. 9) and Sr younger lavas (Godoy et al., 2017) indicate that the Plateau Shield (ppm) (Fig. 12) for the Laguna and Llareta units. Thus, fractional Stage occurred between 300 and 850 kyr, for which this is the most crystallization is the main process controlling evolution of lavas erupted enduring stage of construction of Paniri volcano. With the Malku and during the New Cone Stage. Los Gordos units having erupted elliptically from the volcanic vent Llareta Unit preserves flow structures (ogives and ) that can (Fig. 2), the Plateau Shield Stage is the most voluminous stage of the also be recognized on lavas with similar ages erupted from San Pedro evolution of Paniri volcano, with a total erupted material of ∼51 km3. volcano and La Poruña scoria cone (100–160 ka; Wörner et al., 2000; Taking into account the obtained age of Los Gordos Unit (1.39 Ma) an Bertin and Amigo, 2015; Delunel et al., 2016; Sellés and Gardeweg, estimated bulk eruption rate of 0.086 km3/ka (Fig. 11b) is obtained for 2017). the Plateau Shield Stage. The eruption rate varies from 0.059 to 0.165 New and published (Godoy et al., 2017) ages indicate that eruption km3/ka between the maximum and minimum eruptive ages of this of 9.9 km3 of lavas from the Laguna Unit occurred in a short time (85 stage, respectively (Fig. 11b). kyr; eruption rate 0.12 km3/ka), whilst generation of the Llareta Unit (5.2 km3) lasted ca. 65 kyr, with an eruption rate of 0.08 km3/ka. This 5.3.2. Stage II – Main Edifice (800–400 ka) gives a bulk eruption rate of 0.101 km3/ka for the New Cone Stage Although compositionally different, accordingly to obtained ages, (Fig. 11b). and stratigraphic position, this stage was built by eruption of lavas and Finally, moraine deposits, and associated geomorphological fea- pyroclastic flows of Las Lenguas, and isolated flows from Las Negras tures, have been recognized on the top of Paniri volcano. The glacial units (Fig. 13). Lavas from this stage show flow-banding textures and activity affected, mainly, lavas of the Old and New Cone stages (Fig. 4). are highly eroded (Fig. 4). The volcanic products of this stage covered Also, alluvial and colluvial deposits (Hao, Fig. 3) are distributed mainly almost all lava and pyroclastic flows of the Plateau Shield Stage (Figs. 4 on the lower flanks of the volcano. As estimated by denudation degree and 13). for another volcanoes at Central Andes (Karátson et al., 2012), fluvial Lava flows from Las Lenguas Unit vary from andesitic to almost and glacial activity has removed 5.4 km3 vol. of material from Paniri rhyolitic in composition (Fig. 5). Volcanic products of Las Negras Unit volcano. are the most primitive of the volcanic edifice, varying from basaltic- andesite to andesitic compositions (Fig. 5), with olivine phenocryst 6. Conclusions (Fig. 6e) recognized only on basaltic-andesite lava flows. Flows of Las Negras Units have the highest Mg#, and Ni concentrations (Figs. 7 and Evolution of Paniri volcano involved eruption of lava and

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Fig. 13. Schematic profile showing evolution of Paniri volcano based on AA′ line of Fig. 3. pyroclastic flows over > 1 Myr. These volcanic products gave rise the ( ± 7 km). volcano during four stages: Plateau Shield, Main Edifice, Old Cone and Furthermore, eruptions of lavas at Paniri are related to the north- New Cone. During this evolution an estimated volume of 85.3 km3 of westwards migration of the San Pedro – Linzor volcanic chain. The material was erupted, with bulk eruption rates of each stage varying magmatic evolution of Paniri is therefore similar to the main frame- from 0.021 to 0.101 km3/ka, and a total of 5.4 km3 removed by glacial work of evolution of this volcanic chain, with crustal contamination of and fluvial activity. Compositionally a wide range of lavas is observed, partially molten upper crust associated with the presence of the varying from basaltic-andesite to rhyolitic. Isotopically, almost all lavas Altiplano – Puna Magma Body. In addition, it is important to point out show 87Sr/86Sr ratios between 0.7070 and 0.7075. AFC-models indicate that Paniri, together with San Pedro volcano, represents the last evo- that contamination of primitive magmas with melts generated by par- lutionary stage of this volcanic chain. tial melting of the crust is the first stage of the magmatic evolution of Pristine, extensive lava flows in the final stages (i.e. Llareta Unit) Paniri volcano. After this, fractional crystallization of primary magmas suggest that Paniri is an active volcano. However, ages presented in this with main crystallization of plagioclase + pyroxene ± hornblende work indicate that the last activity of Paniri occurred, at most, at ∼100 assemblage, and plagioclase + olivine ± pyroxene assemblage in the ka. This indicates that Paniri has remained inactive during the less contaminated products (i.e. Las Negras Unit) occurred. Crustal Holocene, with eruption of its last stage occurring prior to eruption of contamination was generated at shallow levels (< 20 km), while frac- Chao Dacite (89 ka) and Chillahuita dacitic domes, considered a vol- tional crystallization was active in reservoirs at even shallower depths canic system different to Pleistocene volcanism at the Altiplano-Puna

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Table 5 Bertin, D., Amigo, A., 2015. Geología y peligros del Volcán San Pedro, II Region. In: Actas AFC-type model parameters (after DePaolo, 1981) for erupted magmas at San XIV Congreso Geológico Chileno, La Serena, Chile, vol. 3. pp. 128–131. Pedro – Linzor volcanic chain. Bulk D according to partitioning coefficients Blum-Oeste, M., Wörner, G., 2016. Central Andean magmatism can be constrained by three ubiquitous end-members. Terra. Nova 28, 434–440. http://dx.doi.org/10. from Rollinson (1993) for basaltic melts. Mineral assemblage according to 1111/ter.12237. petrographic characterization of lavas from Paniri volcano (Martínez, 2014; Burns, D.H., de Silva, S.L., Tepley III, F., Schmitt, A.K., Loewen, M.W., 2015. Recording Lazcano, 2016; this work, Table 4). the transition from flare-up to steady-state arc magmatism at the Purico-Chascon volcanic complex, northern Chile. Earth Planet Sci. Lett. 422, 75–86. http://dx.doi. Initial Contaminant Mineral (% vol) org/10.1016/j.epsl.2015.04.002. Assemblage Chmielowski, J., Zandt, G., Haberland, C., 1999. The central Andean Altiplano-Puna magma body. Geophys. Res. Lett. 26 (6), 783–786. http://dx.doi.org/10.1029/ Location Lascar volcano Sierra de Plagioclase 40 1999GL900078. Moreno Clavero, J.E., Sparks, R.S.J., Pringle, M.S., Polanco, E., Gardeweg, M.C., 2004a. Evolution Reference Matthews Lucassen et al. Clinopyroxene 30 and volcanic hazards of Taapaca volcanic complex, central Andes of northern Chile. et al. (1994) (2001) J. Geol. Soc. 161 (4), 603–618. http://dx.doi.org/10.1144/0016-764902-065. Sample LA 123 4/316 Orthopyroxene 15 Clavero, E.J., Sparks, J.S.R., Polanco, E., Pringle, S.M., 2004b. Evolution of Parinacota volcano, central Andes, northern Chile. Rev. Geol. Chile 31 (2), 317–347. http://dx. SiO2 (wt. %)* 57.55 65.28 Hornblende 5 doi.org/10.4067/S0716-02082004000200009. Al2O3 (wt. %)* 17.10 15.12 Olivine 5 Coira, B., Davidson, J., Mpodozis, C., Ramos, V., 1982. Tectonic and magmatic evolution CaO (wt. %)* 7.11 1.78 – – Sr of the Andes of northern and Chile. Earth Sci. Rev. 18 (3 4), 303 332. Na2O (wt. %)* 3.64 2.47 D (bulk) 0.84 Nd http://dx.doi.org/10.1016/0012-8252(82)90042-3. K2O (wt. %)* 1.55 3.19 D (bulk) 0.2 de Silva, S.L., 1989a. Altiplano-Puna volcanic complex of the central Andes. Geology 17 MgO (wt. %)* 3.78 2.14 (12), 1102–1106. http://dx.doi.org/10.1130/0091-7613. t FeO (wt. %)* 6.36 5.63 de Silva, S.L., 1989b. Geochronology and stratigraphy of the from the 21°30′S Sr (ppm) 711 185 to 23°30′S portion of the Central Andes of northern Chile. J. Volcanol. Geoth. Res. 37 87Sr/86Sr 0.705765 0.72777 Conditions (2), 93–131. http://dx.doi.org/10.1016/0377-0273(89)90065-6. Nd (ppm) 25 37 r = Ma/Mc 0.6 de Silva, S.L., Francis, P.W., 1991. Volcanoes of the Central Andes. Springer-Verlag, 143Nd/144Nd 0.51247 0.512087 Berlin, pp. 218. de Silva, S.L., Self, S., Francis, P.W., Drake, R.E., Ramírez, C., 1994. Effusive silicic vol- *Recalculated 100% water free. canism in the Central Andes: the Chao dacite and other young lavas of the Altiplano- Puna volcanic complex. J. Geophys. Res. 99 (B9), 17805. http://dx.doi.org/10.1029/ t = Total Fe as Fe2+. 94JB00652. Delgadillo Terceros, Z., 2000. State of the geothermal resources in , Laguna volcanic complex. This suggests a change on magmatic evolution of the Colorada project. In: World Geothermal Congress Proceedings, Kyushu - Tohoku, – San Pedro – Linzor volcanic chain at this zone related to waning of the Japan, pp. 153 158. fl – Delunel, R., Blard, P.H., Martin, L.C.P., Nomade, S., Schlunegger, F., 2016. Long term low ignimbrite are-up of the Altiplano Puna volcanic complex. latitude and high elevation cosmogenic 3He production rate inferred from a 107 ka- old lava flow in northern Chile; 22°S-3400 m a.s.l. 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