“…Since hyperacid volcanic fluids are more aggressive with respect to near-neutral and alkaline fluids during water-rock interaction, a higher amount of rock-derived elements, including Rare Earth Elements (lanthanides + yttrium; REE), is leached and mobilized (Michard, 1989;Lewis et al, 1997;Takano et al, 2004;Varekamp et al, 2009;van Hinsberg et al, 2010;Peiffer et al, 2011;Hikov, 2015;Inguaggiato et al, 2015;Varekamp, 2015;Inguaggiato et al, 2017;van Hinsberg et al, 2017;Woitischek et al, 2017;Inguaggiato et al, 2018;Inguaggiato et al, 2020a;Inguaggiato et al, 2020b). The geochemical and economic importance of REE prompted to study them in a wide variety of environments, among which the fluids associated with volcanic areas, and especially volcanic crater lakes (Kikawada et al, 2004;Takano et al, 2004;Varekamp, 2015;van Hinsberg et al, 2017;Inguaggiato et al, 2018;Inguaggiato et al, 2020a;Inguaggiato et al, 2020b;van Hinsberg et al, 2020). Consequently to the increasing knowledge of the geochemical behavior of REE, it is possible to develop several applications using REE as geochemical tracers of fluid-rock interaction in active volcanic systems.…”