新疆塔城黄土沉积常量地球化学元素特征及其环境意义  

CHARACTERISTICS OF MAJOR GEOCHEMICAL ELEMENTS OF TACHENG LOESS DEPOSITS IN XINJIANG AND ITS PALEOENVIRONMENTAL IMPLICATIONS

作　　者：李冠华[1] 夏敦胜[1,2] 柳加波[1] 温仰磊[1] 赵爽[1] 贾佳[1] 

机构地区：[1]兰州大学西部环境教育部重点实验室,兰州730000 [2]中国科学院寒区旱区环境与工程研究所沙漠与沙漠化重点实验室,兰州730000

出　　处：《海洋地质与第四纪地质》2013年第4期183-191,共9页Marine Geology & Quaternary Geology

基　　金：国家重点基础研究发展规划项目(2010CB950202);教育部博士点科研基金项目(20100211110001);国家自然科学基金项目(41071125;41130102)

摘　　要：选取新疆塔城地区典型黄土剖面进行常量地球化学元素分析,根据常量元素氧化物含量及其相关比值参数对剖面风化淋溶程度及其控制因素进行了初步探讨。结果表明,常量地球化学元素氧化物含量依SiO2、Al2O3、CaO、CO3、Fe2O3、MgO、K2O和Na2O的顺序在地层中逐次降低。相对于上部陆壳(UCC)平均值,塔城剖面各元素平均含量具有一定的差别。以黄土层中平均含量为参考,地球化学元素的相对含量与表土层及埋藏古土壤层也有着显著不同,Ca、Si、Mg元素含量在表土和古土壤中的差异明显。进一步分析显示,塔城剖面基本处于脱Ca、Na的初级风化阶段,总体风化程度较低。表土及古土壤中化学风化程度相对高于黄土层,而埋藏古土壤层的淋溶程度低于黄土层。区域水热组合模式可能对研究剖面的地球化学特征具有重要影响,温湿度状况一定程度上影响地层成壤过程中原生矿物的风化程度,而淋溶作用可能受控于沉积时期的相对湿度状况。In this paper,we studied the characteristics of major geochemical elements and weathering intensity of the loess deposits at the Tacheng section,Xinjiang,northwest China.Results show that among the oxides of the major geochemical elements,SiO2,Al2O3,CaO,CO3,Fe2O3,MgO,K2O and Na2O occur in a decreasing order in the loess section.There is obvious differentiation of oxides in the palaeosol and loess layers and the average contents of Al2O3,Fe2O3 and CaO were markedly higher in paleosol layers.CaO,Fe2O3,MgO,and K2O were accumulated and Na2O,SiO2,Al2O3 depleted in the section compared to the upper continental crust（UCC）.The oxides have different distribution pattern in loess and paleosols and some of the major geochemical elements exhibit different concentrations in the topsoils and the paleosols.Further analysis shows that the Tacheng section had experienced weak chemical weathering after deposition,which was similar to the Yili loess section but far weaker than the loess deposits in the Chinese Loess Plateau and the lower reaches of the Yangtze River.The differentiation of weathering degree between the loess and paleosol was also distinct,indicating that the paloesols have experienced stronger weathering process.However,the eluviation of paleosol layers was weaker than that of loess layers probably resulting from the decline of humidity during the period of pedogenesis.The heat-moisture pattern might exert important effect on the chemical weathering of loess/paleosol sequences in the arid area.

关 键 词：常量元素 化学风化 成壤作用 新疆黄土 

分 类 号：P532[天文地球—古生物学与地层学] P595[天文地球—地质学]