Geochemical Characteristics of Eolian Deposits on the Eastern Margin of the Tibetan Plateau and Implications for Provenance  

作　　者：QI Lin QIAO Yan-song 

机构地区：[1]School of Earth Sciences and Resources, China University of Geosciences [2]Institute of Geomechanics,Chinese Academy of Geological Sciences [3]Key Laboratory of Neotectonic Movement and Geohazard

出　　处：《Acta Geologica Sinica(English Edition)》2014年第3期963-973,共11页地质学报（英文版）

基　　金：supported by the National Department Public Benefit Research Foundation of China (grant no. 201211077);the Mineral Resources Investigation and Appraisal Project of the Ministry of Land and Resources (grant nos. 41212011087118 and 1212010914041)

摘　　要：Eolian dust deposition is intimately related to atmospheric circulation and environmental setting of the source region,and therefore is an invaluable tool for studying the evolutionary history of atmospheric circulation patterns and paleoclimatic change.Identifying the provenance of any eolian deposit is crucial not only for reconstructing the paleoenvironmental history of the dust source region,but also for understanding the paleoclimatic significance of various indices.Loess and paleosol samples from the Garze region on the eastern margin of the Tibetan Plateau （TP） were analyzed for their elemental （major and trace elements） and isotopic （Sm-Nd） geochemistry and compared with those of Northern Chinese （NC） loess formed at the same age.The results show that the geochemical compositions of the Garze loess and paleosol samples are similar to those eolian deposits on the Chinese Loess Plateau （CLP）,and also resemble the average UCC.This indicates that the eolian deposits on the eastern margin of the TP were derived from well-mixed sedimentary protoliths that had undergone numerous upper crustal recycling processes,just as with the CLP loess deposits.However,compared with NC loess,the Garze samples have higher ∑REE,Li,Rb,Zr,Cs,Hf and Bi concentrations,higher TiO2/Al2O3,Hf/Nb,La/Nb,Th/Nb and lower K2O/TiO2,Zr/Hf,Ba/Rb ratios.From the Sm-Nd isotopic geochemistry,εNd（0） and 147Sm/144Nd values of Garze loess and paleosol samples are clearly lower than the NC loess.The higher Bi,Zr and Hf concentrations are relevant to the widely distributed acid-magmatic rocks in this region,whereas the higher contents of Li,Cs,Rb are attributed to the high background values of the TP.The geochemical characteristics of the Garze loess and paleosol samples further prove that the local glacial and other Quaternary detrital sediments are predominantly the contributors for the eolian deposits on the eastern margin of the TP.Stable element concentrations and their ratios in the Garze loess and paleosol samples forEolian dust deposition is intimately related to atmospheric circulation and environmental setting of the source region,and therefore is an invaluable tool for studying the evolutionary history of atmospheric circulation patterns and paleoclimatic change.Identifying the provenance of any eolian deposit is crucial not only for reconstructing the paleoenvironmental history of the dust source region,but also for understanding the paleoclimatic significance of various indices.Loess and paleosol samples from the Garze region on the eastern margin of the Tibetan Plateau （TP） were analyzed for their elemental （major and trace elements） and isotopic （Sm-Nd） geochemistry and compared with those of Northern Chinese （NC） loess formed at the same age.The results show that the geochemical compositions of the Garze loess and paleosol samples are similar to those eolian deposits on the Chinese Loess Plateau （CLP）,and also resemble the average UCC.This indicates that the eolian deposits on the eastern margin of the TP were derived from well-mixed sedimentary protoliths that had undergone numerous upper crustal recycling processes,just as with the CLP loess deposits.However,compared with NC loess,the Garze samples have higher ∑REE,Li,Rb,Zr,Cs,Hf and Bi concentrations,higher TiO2/Al2O3,Hf/Nb,La/Nb,Th/Nb and lower K2O/TiO2,Zr/Hf,Ba/Rb ratios.From the Sm-Nd isotopic geochemistry,εNd（0） and 147Sm/144Nd values of Garze loess and paleosol samples are clearly lower than the NC loess.The higher Bi,Zr and Hf concentrations are relevant to the widely distributed acid-magmatic rocks in this region,whereas the higher contents of Li,Cs,Rb are attributed to the high background values of the TP.The geochemical characteristics of the Garze loess and paleosol samples further prove that the local glacial and other Quaternary detrital sediments are predominantly the contributors for the eolian deposits on the eastern margin of the TP.Stable element concentrations and their ratios in the Garze loess and paleosol samples for

关 键 词：QUATERNARY eolian sedimentology geochemistry PROVENANCE Tibetan paleoclimate Sichuan province 

分 类 号：P512.2[天文地球—地质学] P53