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Lanzhou University (2020)

Heavy Mineral Assemblages and Provenance Analysis of Eolian Sand in the Alashan Desert, Northwestern China

张诚;

Titre : Heavy Mineral Assemblages and Provenance Analysis of Eolian Sand in the Alashan Desert, Northwestern China

Auteur : 张诚;

Grade : Master’s Theses 2020

Université : Lanzhou University

Résumé
Deserts in northern China are located in the mid-latitude arid region and play an important role in shaping terrestrial hypergene processes.Furthermore,these deserts are the main source of dust in eastern Asia and even throughout the Northern Hemisphere.Therefore,accurate identification of the provenance of eolian sand in deserts is essential to studying sedimentation processes in the earth system.Eolian sediment is the material basis for the formation and development of aeolian geomorphology.Its characteristics record significant information in the formation and development of the desert.Thus,determination of the sedimentary environment and material provenances of the desert have great significance for desertification control and ecological construction.The Alashan Desert is an important part of the deserts of northern China with strong sandstorm activity.It is the representative of the typical arid desert with various landforms inside the desert and the sedimentary environment and sediment types is complex and varied.In addition,the Alashan Desert is surrounded by bedrocks,wilderness,fluvial sediment and lacustrine sediment and affected by both fluvial and eolian effects,which leads to quite complex provenances of the Alashan Desert and no unified understanding.Studies of the provenance and transportation processes of eolian sand can not only provide further understanding for the regional and global land desertification and the formation of aolian geomorphology,but also have important guiding significance for land desertification control.And it can provide new evidence for the interaction process and mechanism of various earth surface layers.Hence,in this study,we selected the Alashan Desert in northern China as the study area,and a total of 433 samples were collected throughout the desert and nearby regions to study the provenance of the eolian sand based on their heavy mineral assemblages and contents and combined with wind direction datum and regional geological background.The results show as follows :(1)The heavy mineral assemblages of eolian sand in the Alashan Desert is dominated by magnetite,hematite,garnet,amphibole,zircon,tourmaline,rutile,ilmenite,pyroxene,epidote,apatite,titanite and monazite.However,different deserts and different locations of the same desert have different relative content of heavy minerals.The relative content of stable heavy minerals gradually increases from the periphery of the desert to the hinterland on the whole,and the unstable heavy minerals have opposite trends,but the spatial changes of different deserts are different.Additionally,the heavy mineral assemblages of eolian sand is very similar to that in the bedrock,wildness and the fluvial-lacustrine sediments around the desert.(2)ZTR index and stability coefficient have different changes in different deserts.the spatial variability of the ZTR index and the stability coefficient of the eolian sand in the Badain Jaran Desert and the Tengger Desert are relatively smal

Mots clés : Provenance; Heavy minerals; Arid region; Eolian sediments; Sand sea;

Présentation (CNKI)

Page publiée le 15 octobre 2020