Magnetic Study For Natural Silty-Dust Materials In The Ili Basin And Its Evidenced The Dust Source

Natural source dust is mainly composed of fine sand minerals,which can be transported over long distances and have significant impacts on human health,global climate,biochemical and geochemical cycles,etc.by participating in material and energy exchange in multiple layers.The Central Asian region is one of the important natural source dust emission areas worldwide.A large number of scholars have conducted systematic research on the dust release and transportation processes in Central Asia based on remote sensing data,and have achieved a series of results.However,this research method cannot reflect the material exchange between dust and topsoil during transportation.Geological research methods identify dust source areas by comparing the properties of dust deposition(usually loess)with potential source areas,which has advantages in clarifying the sources of dust deposition materials and is an important supplement to remote sensing analysis methods.At present,the uplift of high Asia has led to the generation of a large number of silt particles,which has provided the main material source for Central Asian loess(dust).However,there is no unified understanding of the dust release and transport mechanism in this area.Some researchers believe that Central Asian loess is the pattern formation through the mountain source area river transport desert transition;Some researchers also believe that the contribution of near source alluvial and fluvial facies materials cannot be ignored,and deserts play a more important role as "intermediate reservoirs".Their contribution to the loess accumulation process in Central Asia has been overestimated.Therefore,it is urgent to conduct more in-depth and comprehensive investigations and studies on the release and deposition of dust in Central Asia.Due to the advantage of closed terrain,the dust in the Ili Basin mainly comes from the interior and surrounding areas of the basin,making it an excellent place to verify the connection between desert and loess materials and determine the source of dust release in arid basins.Based on this,this article takes different types of surface sediments in the Ili Basin as the research object,and further explores the formation and sorting process of dust in the Ili Basin through environmental magnetic research on multiple particle size components.It clarifies the material connection between river sedimentation,desert sedimentation,piedmont alluvial deposits,and loess sedimentation(natural source dust).The preliminary conclusion is as follows:(1)The spatial distribution of magnetic minerals in sediments of different particle size components in the Yili Basin is different.The high magnetic susceptibility values in the components<63 μ m generally appear in the fluvial sediments of the Tukai Desert,the Yili River Valley and the Kunes River Valley,and the alpine silt materials in the west of Tianshan Mountains.For the sand components>63 μ m,the magnetic susceptibility values in the west of the Yili Basin lose the advantage of high values,while the samples in the Kunes River Valley and Tianshan Mountains in the east of the Yili Basin are higher.The variation of saturation isothermal remanence value is not completely consistent with the spatial variation of magnetic susceptibility.(2)The systematic magnetic analysis of grain size grading of sediments of different sedimentary facies in the Yili Basin shows that the magnetic minerals are mainly ferromagnetic magnetite,and hematite contains a certain amount.The magnetic minerals are mostly primary PSD and MD,and almost do not contain SP particles.Loess sediment,fluvial sediment,alluvial-proluvial sediment,and sand samples are all present in 31-63 μ The strongest magnetic properties of the m component,while the strongest magnetic properties occur in high mountain silt materials at>63 μ M component.(3)Based on the spatial distribution characteristics of particle size fractions and magnetic investigations,it is found that the concentrations of 31-63 in loess sediments,fluvial facies sediments,alluvial-proluvial facies sediments,and sand samples are μThe strongest magnetic property of component m is>63 in alpine silt material μ M component.(4)Based on saturated isothermal residual magnetism,a study was conducted to investigate the source of surface sediments in the Ili Basin.It was found that the contribution of weathered debris(alpine silt material)from the Tianshan Mountains to the loess sediments in the basin is minimal,with river facies and alluvial and proluvial sediments being the main suppliers.At the same time,changes in SIRM indicate that sediments near rivers in the desert exhibit transitional characteristics between river facies and desert sediments,This may provide a unique perspective on the role of deserts in dust release and sedimentation patterns in Central Asia,and also remind us to pay attention to the material connections and inheritance between sediments during the process of source tracing in this area.This article provides a scientific supplement to the study of dust release in Central Asia,and points out that it is also necessary to pay attention to the exposed mountain front alluvial fans and aquatic sediments near rivers when conducting dust control in the Ili region.