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Major and trace element, Sr–Nd–Pb–O isotope and mineral chemical data are presented for post-collisional ultrapotassic, silicic potassic and high-K calc-alkaline volcanic rocks from SW Tibet, with ⁴⁰Ar/³⁹Ar ages in the range 17–25 Ma. The ultrapotassic lavas contain mantle xenocrysts (olivine ± rutile/armalcolite). Their initial ⁸⁷Sr/⁸⁶Sr (0.7172–0.7220) and ¹⁴³Nd/¹⁴⁴Nd (0.51190–0.51200) ratios suggest that they originated from lithospheric sources enriched in Rb with low Sm/Nd ratios. Initial Pb isotopic compositions (²⁰⁶Pb/²⁰⁴Pb = 18.41–18.51; ²⁰⁷Pb/²⁰⁴Pb = 15.68–15.72; ²⁰⁸Pb/²⁰⁴Pb = 39.42–39.60) and geochemical features such as high Th/Ta, low Sr/Nd, low Ce/Pb and negative Eu anomalies are consistent with a recycled crustal component. Nd depleted mantle model ages range from 1.3 to 1.9 Ga, whereas Pb model ages record an Archaean event, suggesting that the source had a complex …