Clay crustal dating environment in isotope tracing
The Chinese deserts have ε from −5.94 to 4.63 (mean = −0.97).The Mongolian Gobi is more radiogenic in Nd and Hf isotope compositions which ranges from −5.99 to −2.67 (mean = −4.43; n = 9) and from −2.56 to 3.68 (mean = 0.81; n = 9), respectively.
The Hf and Nd isotopic data of the clay-sized fractions of the Chinese deserts and the Mongolian Gobi are presented in Figure 2A (see Table S1 in Supplementary information).REE barely fractionate during weathering and have been used for studying the provenance of detrital sediments.More specifically, ratios such as REE ratio and Nd isotopic compositions of weathered material, are considered to represent the compositions of source rocks2 μm fraction (0.05), whereas the Sm/Nd ratio remains the same (0.18) (Table S3, and Figure S3 in Supplementary information), suggesting the difference or decoupling of Hf to REE during weathering process.For example, samples from the Central Asian Orogeny Belt (CAOB, Altay Mts.-Tianshan Mts.-Yin Mts.-Daxinganling Mts) were easily differentiated from the Sino-Korean-Tarim Craton (SKTC) desert samples based on their Hf-Nd isotopic composition, supporting two separate isotopic provinces as reported before The Hf-Nd isotopic signatures of the Chinese and Mongolia Gobi Deserts are consistent with previous Sr-Nd isotopic observations, suggesting that the isotopic composition of deserts is closely related to the tectonic setting of the surrounding mountains (Fig. The Gobi Desert, Gubanunggut Desert and Hulun Buir Sandy land are on the CAOB, whereas the Taklimakan, Qaidam, Badaim Jaran, Tengger and Mu Us Deserts are on the SKTC.The Tarim, Qaidam and Alxa blocks belonged to the Sino-Korean tectonic domain during the Archean-Mesoproterozoic value within CAOB indicates that the clay-sized fraction is generated from CAOB juvenile continental crust, which was formed by the collision between the Siberian Plate and the southern blocks during the early stages of the orogeny about 1.0 Ga and continued to about 250 Ma values from deserts of the same geologic setting, suggesting that not all the isotopic differences are caused entirely by the heterogeneity of material at their source.
The Hf isotope signatures from SKTC also show more scatter.