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The age distribution of detrital zircon has been used to trace sediment sources. Existing datasets show great similarity of zircon ages between the loess on the Chinese Loess Plateau (CLP) and the sediments from the North Tibetan Plateau (NTP), implying that eolian dust is delivered from the NTP to the CLP by westerly winds or via the Yellow River. However, NTP dust can also be transported by northwesterly winds from the Alxa arid lands (AALs), where materials are received from both the NTP and the Gobi Altay Mountains (GAMs). Here we report U-Pb zircon ages for AALs sands and NTP and CLP loess. The results show that the zircons in the AALs are mixed from NTP and GAMs zircons. NTP loess is mainly derived from local sources. Mixing of materials from the NTP and GAMs defines the zircon ages of the loess on the CLP better than the pure NTP source. No temporal and spatial heterogeneities of zircon ages have been observed for the loess on the CLP, which suggests that the well-mixed materials in the AALs likely have an eolian source. (C) 2013 University of Washington. Published by Elsevier Inc. All rights reserved.