Gas and aerosol emissions from Lascar volcano (Northern Chile): Insights into the origin of gases and their links with the volcanic activity G. Menard a, ⁎, S. Moune a,b , I. Vlastélic a , F. Aguilera c,1 , S. Valade a , M. Bontemps b , R. González d a Laboratoire Magmas et Volcans, Clermont Université, Université Blaise Pascal, CNRS UMR 6524, IRD R 163, 5 rue Kessler, 63038 Clermont-Ferrand Cedex, France b Observatoire de Physique du Globe de Clermont-Ferrand, 24 avenue des Landais, BP 80026, 63171 Aubière Cedex, France c Departamento de Geología, Universidad de Atacama, Av. Copayapu 485, Copiapó, Chile d Departamento de Ciencias Geológicas, Universidad Católica del Norte, Av. Angamos 0610, Antofagasta, Chile abstract article info Article history: Received 19 December 2013 Accepted 8 September 2014 Available online 19 September 2014 Keywords: Lascar volcano Volcanic plume Acid gases Aerosols Volatiles Trace elements This study focuses on the chemical compositions of volcanic gases and aerosols emitted by Lascar volcano (Northern Chile). The sustained volcanic plume was sampled in April 2009, April 2011 and November 2012 through filter packs and analyzed for major gaseous species (SO 2 , HCl, and HF) and trace elements. During field- work, SO 2 flux measurements were also performed by UV spectrometry (DOAS). The Lascar volcano is a signifi- cant and sustained emitter of SO 2 (between 150 and 940 t/d), HCl (between 170 t/d and 210 t/d) and HF (up to 100 t/d). Combining the SO 2 -normalized trace element concentrations and the SO 2 emission rates, we evaluate that the quiescent degassing of Lascar is an important local source of trace metals to the atmosphere with contri- butions to global volcanic fluxes generally less than 2%. Our data were used to infer the origin of the gas emitted at Lascar. Two major degassing sources were identified: a deep magmatic reservoir and a shallow hydrothermal system. The variable interaction between these two sources is the most likely scenario for explaining the compositional ranges in acid gases but also in a volatile and fluid–mobile trace element such as B. These variations are related to changes in volcanic activity: an exten- sive interaction between the hot ascending magmatic gases and the shallow aquifer occurred in 2009, possibly due to a long period of quiescence, before magmatic activity renewed in 2011 and 2012. Our study highlights, therefore, that filter-pack measurements may be used to study changes in subsurface processes that probably play a key role in triggering volcanic eruptions. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Plumes of active volcanoes represent complex mixtures of gases and particles (condensation aerosol and tephra) (e.g., Mather et al., 2003). They are considerably enriched in acid gases (SO 2 , HCl, HF) as well as in numerous trace elements (e.g., Zoller et al., 1974). In magmatic sys- tems, most of the plume's constituents are supposed to have been re- leased directly from the magma (e.g., Symonds et al., 1987) and their study may yield important insights into the dynamics of eruptive processes and the mechanisms that control subsurface degassing activ- ity (e.g., Symonds et al., 1994; Oppenheimer, 1996; Allard et al., 2005; Martin et al., 2009). In the case of a strong hydrothermal component, plume composition records the interaction of the rising magmatic gas with hydrothermal fluids (e.g., Truesdell et al., 1989; Taran et al., 1992; Martini, 1993; Symonds et al., 2001) and provides informations about the state of the volcano. Furthermore, volcanic emissions are one of the most important natural sources of trace metals in the atmo- sphere (e.g., Cadle, 1980; Nriagu, 1989; Hinkley et al., 1999) and may af- fect the chemical composition of the ambient air and the environment at a local (e.g., Calabrese et al., 2011 and reference therein) as well as a global scale during major eruptions (e.g., Rampino and Self, 1992; Thordarson et al., 2001). Characterization of gas and particle chemistry in volcanic plumes is essential for estimating their effects on atmospher- ic composition, ecosystems and human health (e.g., Delmelle, 2003: Mather et al., 2003; Robock and Oppenheimer, 2003). Gas and aerosol measurements using filter packs are widely carried out to study the transport of trace elements in volcanic plumes and to estimate elemental fluxes to the atmosphere (e.g., Varekamp et al., 1986; Pennisi et al., 1988; Zreda-Gostynska et al., 1997; Gauthier and Le Cloarec, 1998; Allard et al., 2000; Allen et al., 2000; Cheynet et al., 2000; Aiuppa et al., 2003; Mather et al., 2003, 2012; Fulignati et al., 2006; Martin et al., 2008, 2012; Moune et al., 2010; Calabrese et al., 2011; Zelenski et al., 2013). These studies have highlighted that, depending on volcano activity, various processes may be responsible for aerosol formation, such as magma fragmentation, condensation of volatile species emitted directly from magmas, incorporation of silicate Journal of Volcanology and Geothermal Research 287 (2014) 51–67 ⁎ Corresponding author at: Laboratoire Magmas et Volcans, 5 rue Kessler, 63038 Clermont-Ferrand Cedex, France. Tel.: +33 4 73 34 67 23. E-mail address: g.menard@opgc.univ-bpclermont.fr (G. Menard). 1 Current address: Servicio Nacional de Geología y Minería, Av. Santa María 0104, Providencia, Santiago. http://dx.doi.org/10.1016/j.jvolgeores.2014.09.004 0377-0273/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Volcanology and Geothermal Research journal homepage: www.elsevier.com/locate/jvolgeores