Hydrogeochemical processes governing the origin, mobility and transport of trace elements in the Domuyo Volcanic complex Geothermal system (Patagonia, Argentina)

The system of Domuyo Volcanic Complex is one of the most promising geothermal fields of Patagonia (Argentina). In this paper, we present a geochemical model of the Domuyo geothermal system based on previous studies and integrated with the systematic characterization of trace elements, thus adding a new piece to the puzzle of one of the most impressive geothermal systems in Argentina. A total of 38 water samples were collected from 17 different sampling sites, during three field-campaigns from 2013 to 2016, and analysed for 28 trace elements (Li, Be, B, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Y, Zr, Mo, Cd, Sb, Cs, Ba, Tl, Pb, Th and U). Sampling sites included the main river (Varvarco), its tributaries which cross the geothermal area, and thermal and cold springs. The investigation was focused on the origin, behaviour and estimation of mass fluxes of trace elements. Computing mass fluxes of trace elements transported by rivers is an important tool in the estimation of both the impact of potentially toxic elements and the exploitation of economically valuable elements. Among others, the mass fluxes of trace elements originating from the Domuyo geothermal system transported by rivers range from 45 to 278 t y −1 for As, B, Cs, Li, Sr and Rb; such contributions flow to the Varvarco river, where the concentrations and mass fluxes of these elements increase by one to two orders of magnitude in the site downstream of the geothermal area with respect to that upstream. • The Domuyo hydrological system is significantly influenced by a mature geothermal brine, impacting surface water quality. • Tributaries to Varvarco river exhibit marked shifts in water composition, driven by geothermal contributions from Na + -Cl − -rich thermal springs. • Rivers in the system transport substantial fluxes of trace elements (e.g. As, B, Cs, Li, Sb), increasing concentrations by up to two orders of magnitude in the Varvarco River. • The total energy release from the geothermal system is calculated at 1.0 ± 0.2 GW.