粉尘释放、搬运、沉积与黄土化过程中磁性变化规律

he Chinese Loess Plateau contains vast deposits of aeolian dust, with loess sediments spanning an area of approximately 440 thousand square kilometers and a volume exceeding ~200 thousand cubic kilometers. However, the provenance of these deposits remains debated. The Alxa Plateau and its surrounding regions have been identified as a significant potential source of loess for the Chinese Loess Plateau (CLP), but this hypothesis has been challenged due to the notably high magnetic susceptibility of the loess compared to its proposed source. Some studies suggest that the differing magnetic characteristics between the source material and the loess deposits may result from particle sorting during transportation from the Alxa Plateau to the CLP. To assess whether environmental magnetism can effectively trace loess sources and how to apply this method, it is essential to understand the transformations of ferrimagnetic minerals during dust emission, transport, deposition, and subsequent loessification. In this study, we compare the magnetic properties of desert sediments, modern dust samples from the Alxa Plateau, and aeolian deposits (loess) from the CLP. Our results indicate that: (1) desert samples (particle size <63 micrometer) are dominated by PSD/MD-grained magnetite, (2) modern dust and loess samples (both <63 micrometer) exhibit a mix of PSD/MD to coarse SD magnetite. (3) magnetite concentration is similar in modern dust and CLP loess but significantly higher in desert samples. These findings suggest that wind preferentially transports finer, less magnetic minerals to the loess deposition area. Continuous wind sorting leads to substantial differences in magnetic properties between source sediments and aeolian deposits. Therefore, comparing aeolian dust in the source region with deposits in the CLP provides a more scientifically robust approach for provenance estimation than comparing loess with desert sediments directly. Additionally, it should be noted that loessification can significantly enhance the concentration of fine, strongly magnetic minerals in loess deposits. Thus, weakly weathered loess is a more suitable research subject for source tracing.