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- Figure 4: Major-element and B-isotope abundances from texturally-variable tourmalines; core (gold), sector-zoned rim (blue), and oscillatory-zoned rim (green). (a) Al-Mg-Fe ternary plot. Numbers show compositional fields of tourmalines defined by Henry and Guidotti (1985); 1, 2: Li-rich or Li-poor granitoid pegmatites and aplites. 3: Ferric ion-rich quartz tourmaline rocks (hydrothermally-altered granites). 4, 5: Metapelites and metapsammites with or without an Al-saturating phase. 6: Ferric ion-rich quartz tourmaline rocks, calc-silicate rocks and metapelites. 7: low-Ca metaultramafics and Cr,V-rich metasediments. 8: Metacarbonates and metapyroxenites. (b) δ11 B - Mg/(Fe+Mg) plot. Error bars on δ11 B values correspond to reproducibilities on reference tourmaline analysis during the session (~1.2‰ in 1σ).