Clay crustal dating environment in isotope tracing dating sitr
3) What are implications for the source and transport pathway of eolian dusts in the North Pacific Ocean? The study areas include the Chinese deserts, Mongolian Gobi and northwest Pacific Ocean, are shown in Figure 1 and Figure 3.
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).
The decoupling of clay-sized Hf-Nd isotopic compositions may explain the different Hf-Nd correlation patterns between SKTC and CAOB.
It is noted that the SKTC clay-sized array has a higher radiogenic Hf isotopic composition for its corresponding Nd isotopic composition than the CAOB array.
The offset of the clay-sized Hf and Nd isotopic composition from the terrestrial array toward the seawater array can be generated by incongruent weathering of continental rocks, which is known as “zircon effect”, have relatively high Hf concentrations and indestructibility, and contain large amounts of unradiogenic Hf, causing relatively radiogenic Hf to enter weathering products and/or fine-grained sediments.
Thus, clay minerals, the weathering products of continental rocks, are expected to be more radiogenic that primary rocks or bulk sediments.
Geographically, both D17 and Nmy-8 belong to CAOB, but their source may be the mountainous area of North China Craton as assessed by comparing clay-sized ε.
However, the other two exception samples (T46 and Surfer25), which are located on the northeast of Taklimakan Desert and the northern edge of Hubq Desert between CAOB and SKTC tectonic domain, respectively, do not fall within the SKTC end-member but close to CAOB end member edge, implying that they were controlled by CAOB and SKTC tectonic domains.
Instead they reflect the influence of surface transport causing the isotopes to be skewed toward the CAOB by near-surface northwesterly wind.
Geologically, blocks and/or cratons formed the Chinese continent through multiple collisions and aggregation.
The clay-sized Hf-Nd isotopes of the Qaidam Desert were simliar to the SKTC terrane, we thus conclude that the Qaidam basin was attributed to SKTC, even if the Qaidam basin was influenced by the proximity to Altunshan Fault, Tarim craton and Central China Orogen.
It is clear that the clay-sized fractions have higher radiogenic Hf isotopic composition than silt-to-sand silicate fractions (Map showing the distribution of Gobi and sandy deserts in northern China and southern Mongolia, including the Gobi desert in southern Mongolia (MG) and northern China, Tengger (TG), Badain Juran (BJ), Mu Us (MU) and Hobq (HB) sandy deserts in northern China, Taklimakan (TK) and Gurbantunggut (G) desert in northwestern China, Qtingdag (OT), Hulun Buir (HL) and Horqin (HQ) sandy lands in northeastern China, and Qaidam Desert (QD) in the northern Tibetan Plateau.