Tourmaline geochemical and boron isotopic compositions of the Bailongshan rare-metal pegmatite deposit: Implications for magmatic-hydrothermal evolution of the West Kunlun Orogen (NW China)

•Tourmaline in muscovite is of schorl type and tourmaline in barren and ore-bearing pegmatite are of oxy-schorl and fluor-elbaite.•Local fluid/melt composition may have influenced the tourmaline trace element compositions.•Fluid exsolution occurred in ore-bearing pegmatite with high Li contents.•B-isotope variation among tourmaline types linked to melt-fluid-tourmaline fractionation.