Na–K (Arnorsson et al. 1983; Fournier 1979) | Na–K–Ca corrected for Mg (Fournier and Potter 1979) | Na–K–Ca–Mg (Nieva and Nieva 1987) | K–Mg (Giggenbach 1988; Fournier 1991) | Quartz (Fournier 1977; Fournier and Potter 1982; Arnorsson 1985) | Chalcedony/silica (Fournier 1977; Arnorsson et al. 1983) | Binary diagram (Giggenbach 1988; Tassi et al. 2008) |