Elemental Geochemistry Characteristics Of Surface Sediments From The Ili Basin And The Southeast Of Kazakhstan,and Their Implications For Provenance

The westerly lies in the transitional zone between the climate system of the North high latitude Hemisphere and the East Asian monsoon,and the varies of its position and intensity along with glacial-interglacial cycles have great effects on the East Asian monsoon climate as well as global climate.The Ili Basin in the Xinjiang Province of northwestern China is located in the Central Asian hinterland,and is influenced by westerlies throughout the year.Thus the loess record in the Ili Basin provides an important archive for the westerlies and the regional environment change.Provenance studies of the aeolian deposits are important figuring out the significance of proxies and rebuilding regional climate.Then,the study of the Ili loess provenance is important to westerlies study.In this work,we choose surface sediments of loess,soil,river,desert,bedrock from the Ili Basin and the southeast of Kazakhstan,which are the potential provenance regions of the Ili loess,as our study object,and systematically analyse of major elements,rare earth elements(REE),and other trace elements in bulk phase,acetic acid leachate and the residue of these sediments were taken out.At the same time,we also collect elements data of sediments from the China Loess Plateau(CLP),the Tibetan Plateau,the Tarim Basin and the Thar Desert in India for comparative studies.The preliminary results are shown as below:1.The comparison result of geochemistry analyses of sediments from the CLP,the Tarim Basin,the Tibetan Plateau,the Thar Desert and the Ili loess with different phase(bulk,acid-leachate,acid-residue)showed that the distribution of REE concentration normalized to upper continental crust(UCC)and bivariate plots of stable elements normalized to UCC ratio proxies((Zr/Nb)N-(Hf/Th)N with bulk phase,(Rb/Al)N-(Na/K)N and(La/Gd)N-(Nd/Yb)N with acid-residue phase)could record the differences of sediment from different climatic zones.2.The distribution of REE concentration normalized to UCC and bivariate plots of stable elements of surface sediments from the Ili Basin and the southeast of Kazakhstan analyse results showed that most of loess samples from the Ili Basin had the REE pattern with medium rare earth elements enrich,and river sediments,desert sand sediments from the Ili Basin,bedrocks from Tianshan mountain and sediments from the southeast of Kazakhstan had the REE pattern with heavy rare earth elements enrich.But sediments with similar REE pattern showed spot area independently in bivariate plots of stable elements,and only few samples showed cross region.3.According to the geochemistry analyse results we considered that the uplift of the Tianshan Mountain,glacier erosion,and weathering produced large-scale silt material.This kind of material was transported into the piedmont alluvial fans by rivers,such as Tekes River,Kash River and Kiines River.Part of them exposed surface by the geologic movement,and were carried to terraces and neighboring regions by local circulation,and formed into loess and desert sediments.The other part was carried to the southeast of Kazakhstan by fluvial system,and formed into the Kazakhstan loess and desert sediments.And the fine grain-size part may be carried to east by low level west wind,and formed into the Ili loess.But sediments in the Ili Basin and southeast of Kazakhstan are not the main source of the Ili loess both.the Ili loess is the thoroughly mixed product of high altitude westerly carrying material,dust material transported by the west wind from Kazakhstan,material of Tianshan Mountain and the Ili Basin supplement by local circulation,even more wide area material probably.