Literature values for oxygen isotope ratio of garnet (determined by laser fluorination) and mole fraction Andradite (And) for Willsboro–Lewis skarn garnets from Kohn and Valley (1998), Clechenko (2001), Clechenko & Valley (2003), Barcello et al. (2018), and this study (Table S16). ‘A’ shows the span of values from a single Willsboro garnet (Clechenko & Valley, 2003) and ‘B’ shows the span of values from a single Lewis garnet (Fig. S8). Three possible fluid endmembers are recognized: (1) magmatic water, (2) meteoric water, and (3) meteoric water after interacting with igneous rocks (see text; Clechenko, 2001).