Geochemistry of surface soil in the Eastern Pamirs and its implications for Muztagata ice core dust provenance

Determining the geochemical composition of mineral dust is highly effective for provenance tracing. Studies on the geochemistry of surface soils in the Pamirs, especially with different size fractions, are relatively limited. This study investigated the major, trace and rare earth elements (REEs) of surface soil samples collected on the Eastern Pamirs. The Fe/Al (similar to 0.60), Mg/Al (similar to 0.30) and Ti/Al (similar to 0.05) ratios clearly highlight its clayey nature, while the La/Th (similar to 2.60) and Th/U (similar to 4.00) ratios indicate it is typical of the upper continental crust (UCC). The La-Th-Sc and Zr/10-Th-Sc ternary diagrams show the source rock of the Eastern Pamirs surface soil to be mainly felsic. The bulk and <20 mu m fractions were separated and analysed, showing similar REE patterns. However, the La-N/Sm-N, delta Ce, Ce/Nd, Th/Tb and Y/Er ratios of the <20 mu m fraction differ from those of the bulk, suggesting particle size sorting has a significant impact on the elemental composition of surface soil samples. The Taklimakan Desert sand samples partly display similar tracing indices while the Eastern Pamirs surface soil samples generally show different provenance indexes compared to the Muztagata ice core and aerosol dust, indicating that the Taklimakan Desert might be an important contributor to the Muztagata ice core/aerosol dust and the local contribution is minor. Analysis of the MODIS AOD fields, wind streamline fields and HYSPLIT backward trajectory model demonstrates certain atmospheric circulation patterns and dust transport pathways in the Eastern Pamirs, which allows for sourcing of Muztagata dust from the Taklimakan Desert, Central Asian deserts, and northern Afghanistan and Pakistan.