Structural control on shallow hydrogeochemical processes at Caviahue-Copahue Volcanic Complex (CCVC), Argentina

The Caviahue-Copahue Volcanic Complex (CCVC) hosts one of Argentina's most important geothermal systems. To provide new insights into origin, circulation, and residence time fluids, the chemical isotopic composition (3He/4He, ?2H-?18O in H2O; ?13C-?18O CO2; 87Sr/86Sr) thermal waters was measured together with 3H 14C activities. Water samples were collected from hot springs (LM, TC, LMM, CB AF) representing five major zones CCVC assumed to be steam-heated meteoric waters, a well condensate (COP-2). CB, AF 87Sr/86Sr ratios show that water chemistry is acquired locally exchange volcanic rocks (Sr, SiO2, among others) steam (H2S). Two surface manifestations (LM TC), along condensate, COP-2, contain higher contribution deep-originating indicating possible deep-seated granitoids or sediments underlying basement. Radiocarbon-based times indicate ages ranging between 13,540 17,520 yrs. BP, minimum age for reservoir waters. Tritium mainly absent spring except LMM where activity close detection limit. This indicates older than 70 circulating shallow circuit. result suggests have more complex and/or deeper circuit, resulting times. Helium isotopes span wide range, pure mantle-derived value, 8.35Ra, crustal radiogenic signature, 4.6Ra. spatial variation explained by associating geochemical data geological context, which includes distribution fault-fracture meshes different sources magmatic volatiles Copahue volcano. first order control on helium isotope signatures observed this study seems dominated degree assimilation sources, turn controlled local arrays faults.