Quantitative Tracing of Provenance for Modern Eolian Sands with Various Grain Size Fractions in the Ulan Buh Desert, Northwestern China

Accurate identification of eolian sand provenance in deserts is beneficial for understanding desert formation and evolution. However, eolian sands of diverse grain sizes usually have different provenances, making their quantitative tracing challenging. In this study, a total of 45 samples, including 24 current desert eolian sand samples and 21 provenance region samples, were collected across the Ulan Buh Desert in northwestern China; they were analyzed for trace elements and rare earth elements using inductively coupled plasma mass spec-trometry. The provenance of various grain size fractions was quantitatively traced using a composite finger-printing approach. Our results revealed that provenance contributions to the eolian sand grain size fractions were affected by transport dynamics, transport distance, and source lithology. The Langshan Mountains, which have a highly unstable mineral content, contributed 68% of the very fine sand (<125 mu m). The Hawula Mountains and paleolacustrine deposits in the desert hinterlands, which have the shortest transport distance and are affected by strong winds, contributed 36-65% and 20-56% of the coarser (>125 mu m) fractions of eolian sand in the desert, respectively. Thus, the quantitative contribution of the provenances to eolian sands were as follows: the Hawula Mountains, 39%; paleolacustrine deposits in desert hinterlands, 34%; the Langshan Mountains, 21%; and the peripheral Gobi, 6%. This study suggests that coarse-grained materials can originate from paleolacustrine de-posits in desert hinterlands, which should not be ignored as a substantial provenance of eolian sands in future studies. Moreover, sedimentary sorting should be considered during composite fingerprinting to quantitatively trace the provenance of eolian sands with various grain sizes. This study enables an accurate estimation of the provenance of eolian sands in deserts.