Chemical variations of loess from the Chinese Loess Plateau and its implications

ABSTRACT

The Chinese Loess Plateau (CLP) is the largest loess deposit on Earth with expansive surface-exposed source rocks of varying origins, ages, and history. Here, we present abundances of elements on representative loess and palaeosol samples from seven classic sections of the CLP. Most elements, including soluble elements (e.g. Rb and Cs), show significant correlations with La or Al₂O₃. These correlations indicate that these elements are hosted or absorbed in particle minerals during weathering, transport, and deposition (e.g. mica, K-feldspar, and clay minerals). These new observations allow the use of La/X (‘X’ being the element of interest) and the estimated La abundance of 31 ppm in the model upper continental crust (UCC) to estimate the abundances of other elements. The results show higher Cs (Cs = 6.7 ± 1.2 ppm), lower transition metals, Ba, and Ga. Given the high CaO and presence of carbonate in UCC rocks of both vast western China (the primary source for the CLP) and eastern China, we propose that these updates on the element abundances represent a refined model for the carbonate-bearing UCC.

KEYWORDS:

• Upper continental crust
• loess
• Chinese Loess Plateau
• element behaviours
• carbonate

Acknowledgments

This paper is dedicated to the late Prof. Shan Gao, who has made major contributions to constrain the composition of the UCC. This study was supported by the National Natural Science Foundation of China (Grant numbers: 41776069 to Yuanyuan Xiao), Strategic Priority Research Program of Chinese Academy of Sciences (Grant number: XDB42020302). We appreciate Dr. Robert J. Stern for superb editorial handling. Thanks to Professor Roberta Rudnick and an anonymous reviewer for in-depth review comments and suggestions, and the constructive discussions with Professor Yong-Fei Zheng. We also thank Dong Wang for sample preparation and Kelai Xi and Chunyu Li for SEM-EDS analysis.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2022.2087110

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [41776069]; Special project of strategic leading science and technology of the Chinese Academy of Sciences [XDB42020302].