Fig. 8

a Th/U ratio versus the U/Pb age of the single grain zircon ages (Table 4). b Th/U ratio versus MgO of the whole rocks (data source: Venturelli et al. 1984; Van Marcke de Lumen and Vander Auwera 1990; Owen 2008; Conticelli et al. 2009). In addition the Th/U ratios of Cesana et al. (1976) are indicated as boxes as no exact MgO values are available. c Whole rock La versus MgO for the calc-alkaline rocks (data source as in a). d Whole rock ⁸⁷Sr/⁸⁶Sr isotope ratios versus MgO of dykes of the Sesia–Lanzo Zone. Data source: Bergell-Adamello trend: Kagami et al. (1991); von Blanckenburg et al. (1992, 1998); Venturelli et al. (1984); Owen (2008); Conticelli et al. (2009)