Identifying Tethys oceanic fingerprint in post-collisional potassium-rich lavas in Tibet using thallium isotopes

Following the Indian-Asian continental collision, Tibetan Plateau experienced continuous magmatism from south to north, most of which is characterized by high potassium (K) content and negative niobium‑tantalum‑titanium (Nb-Ta-Ti) anomalies. We performed first exploration using thallium (Tl) isotopes as potential tracers source post-collisional K-rich magmatism. A case study on Tl isotope systematics lavas in Ashikule volcanic basin (AVB) northwestern Tibet provided, represents youngest volcanism Tibet. Thallium abundances AVB are significantly enriched compared other magmatic settings, with concentrations 148 8259 ng/g. ratios (reported ε 205 Tl) extend some heaviest yet measured igneous materials, a range between −2.7 + 6.4 ε-units. evaluate if secondary processes can account for ratios, systematically examining influences alteration, degassing, fractional crystallization, assimilation. Only two samples appear be influenced processes, interpreted kinetic fractionation during one sample may contaminated sulfides coupled elevated Pb contents. The remainder ratio (−2.0 +5.1 ε-units) we interpret reflect region(s) magmas derived. have restricted strontium neodymium isotopes, suggestive homogeneous source, therefore an apparent decoupling radiogenic stable systems these lavas. variation contribution oceanic sediments, associated ancient Paleo- Neo-Tethys subductions. • higher than partial melts primitive mantle. distinguish components. Evidence minor via degassing. Phlogopite important host mineral Tl.