Composition and constraints of lithium isotopes in cryoconite from various remote glacier areas of the Tibetan Plateau.

Lithium isotope is one of the most promising indicators for the study of continental silicate weathering, and lithium concentrations and its isotopic compositions in earth surface can provide a better understanding of the geochemical behavior and isotopic fractionation during weathering and erosion. This work focused on the composition and distribution of Li isotope in cryoconite deposited on various glacier areas in a large range of the Tibetan Plateau and surroundings, as well as its implications for cryoconite dust provenances. Results showed that δ7Li in cryoconite varied within the same order of magnitude (-2.14 ‰-7.74 ‰), which is characterized by geographic distribution of higher δ7Li value of cryoconite in northern glaciers (e.g. Yuzhufeng Glacier), and lower δ7Li value in southern glaciers. In comparison with other global materials, the cryoconite dust shows a lighter δ7Li isotopic composition due to constraints of climatic conditions and land surface weathering intensity. Compared with dust materials in the surrounding Asian dust sources (e.g. large deserts and Gobi), we find that, the primary sources of Li isotope in cryoconite of the northern locations were from both local dust/soils of the TP surface and the surrounding large deserts. Moreover, the products of anthropogenic activities (e.g. coal-burning) may also influence the isotopic composition of the cryoconite dust, and Li isotope may serve as potential tracers of anthropogenic source activities. Therefore, this work provides a complete view of the composition and distribution of Lithium isotopes in cryoconite from various glacier areas of the Tibetan Plateau, and the research significance of its transport processes and source constraints of Li isotopes in cryoconite is proposed.