松嫩沙地元素和Sr-Nd同位素组成特征及其对区域粉尘物源的指示  

Characteristics of element and Sr-Nd isotope composition of the Songnen sandy land and their indications of regional dust material sources

作　　者：杨珮瑶 迟云平[1,2] 谢远云[1,2] 康春国[3] 孙磊 吴鹏 魏振宇 Yang Peiyao;Chi Yunping;Xie Yuanyun;Kang Chunguo;Sun Lei;Wu Peng;Wei Zhenyu(College of Geographic Science,Harbin Normal University,Harbin 150025;Heilongjiang Province Key Laboratory of Geographical Environment Monitoring and Spatial Information Service in Cold Regions,Harbin Normal University,Harbin 150025;Department of Geography,Harbin Institute,Harbin 150086)

机构地区：[1]哈尔滨师范大学地理科学学院,哈尔滨150025 [2]哈尔滨师范大学,寒区地理环境监测与空间信息服务黑龙江省重点实验室,哈尔滨150025 [3]哈尔滨学院地理系,哈尔滨150086

出　　处：《地质科学》2024年第2期549-561,共13页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金项目(编号:42171006,41601200);黑龙江省自然科学基金项目(编号:ZD2023D003)资助。

摘　　要：松嫩沙地位于欧亚黄土带最东端,其物质组成的研究有利于重建松嫩平原冰期—间冰期粉尘传输路径。为此,系统采集了松嫩沙地123个河流沙和风成沙样品,对其进行分粒级的常量、微量和稀土元素以及Sr-Nd同位素组成等地球化学分析,并利用Frequentist模型进行风尘物源定量重建,探讨松嫩沙地不同区域、不同粒级组分对哈尔滨黄土的贡献及搬运路径。结果表明,松嫩沙地经历了初级的化学风化过程(<63μm、<30μm、<10μm组分CIA平均值分别为55.20、57.46、57.51),有较低的再循环历史(<63μm、<30μm、<10μm组分CIA/WIP比值的平均值为0.98、1.08、1.04)。根据不同粒度组分的元素地球化学与Sr-Nd同位素组成特征,将松嫩沙地划分为西北部和西南部两个地球化学分区。不同粒度组分地球化学组成的定量重建结果表明,这两个分区不同粒级组分(<63μm、<30μm、<10μm)对哈尔滨黄土的贡献度分别为:75.7%~88.5%、73.4%~84.9%、61.0%~89.7%(西南部)和11.5%~24.3%、15.1%~26.6%、10.3%~39%(西北部)。本研究揭示了末次冰期以来松嫩平原粉尘传输路径以西南方向为主,与冰期以西北风为主导的环流模式存在差异。The Songnen sandy land is located in the easternmost part of the Eurasian loess belt,and the study of its material composition is beneficial to reconstruct the glacial-interglacial dust transport pathways in the Songnen Plain.To this end,123 fluvial and eolian sand samples from the Songnen sandy land were systematically collected,geochemically analyzed for major,trace and rare earth elements and Sr-Nd isotopic compositions in different grain size fractions,and quantitatively reconstructed from the eolian dust material sources using the Frequentist model,to explore the contribution of the components of different grain size fractions in different regions of the Songnen sandy land to the loess in the Harbin and the transport paths.The results show that the Songnen sandy land has experienced a primary chemical weathering process(the mean CIA values of<63µm,<30µm,and<10µm fractions were 55.20,57.46,and 57.51),with a low recirculation history(the mean values of the CIA/WIP ratios for the<63µm,<30µm,and<10µm fractions were 0.98,1.08,and 1.04).Based on the elemental geochemistry and Sr-Nd isotope composition of the different grain size fractions,the Songnen sandy land was divided into two geochemical subzones,the northwestern and southwestern parts.The quantitative reconstruction results of the geochemical compositions of different grain size fractions showed that the contributions of different grain size fractions(<63µm,<30µm and<10µm)to the Harbin loess in these two subzones were 75.7%~88.5%,73.4%~84.9%and 61.0%~89.7%(southwestern part)and 11.5%~24.3%,15.1%~26.6%and 10.3%~39%(northwestern part).This study reveals that the dust transport path in the Songnen Plain since the Last Glacial Period has been dominated by the south-west direction,which differs from the circulation pattern dominated by the north-west wind during the glacial period.

关 键 词：松嫩沙地 地球化学 Sr-Nd同位素组成 物源定量重建 哈尔滨黄土 

分 类 号：P594[天文地球—地球化学]