松嫩平原杜蒙沙地地表物质的地化组成及风化特征  

Geochemical Composition and Weathering Feature of Surface Sediment in the Dumeng Sandy Land,Northeast China

作　　者：谢远云[1] 孟杰[1] 郭令芬[1] 何葵[1] 康春国[2] 

机构地区：[1]哈尔滨师范大学地理科学学院,黑龙江哈尔滨150080 [2]哈尔滨学院地理系,黑龙江哈尔滨150086

出　　处：《中国沙漠》2013年第4期1009-1018,共10页Journal of Desert Research

基　　金：国家自然科学基金项目(41072259);黑龙江省自然科学基金项目(G201027)资助

摘　　要：本文分析了杜蒙沙地表土样品各粒级组分(全样、>63μm、63～30μm、30～11μm和<11μm)的常量元素组成。结果表明:杜蒙沙地地表物质化学元素组成以Si、Al为主,与上地壳相比,除Si、Mn和Ti外,Fe、Mg、Ca和P严重亏损,Al和Na中度亏损,K轻微亏损;除Si、Al、Na、K外,Fe、Mg、Ca、Ti、P、Mn的变异系数均很高;常量元素在不同粒级中的变化程度按照Al<Si<Na<K<P<Fe<Ti<(Ca,Mn)<Mg的顺序依次递增,Al在不同粒级中的变化很小。Fe、Mg、Ca、Mn、Ti和P随着粒度的变细,含量逐渐增加,而Si、Na和K则相反,Al与粒度不存在明确的相关关系。化学风化指标按照CIA(化学蚀变系数)<(Al+Fe+Ti+Mn)/(Mg+Ca+K+Na)<(CaO+K2O+Na2O)/Al2O3<Fe2O3/MgO<K2O/Al2O3<(CaO+MgO+Na2O)/TiO2的顺序受粒度的影响依次增大,CIA是最好的化学风化指标,其次是(Al+Fe+Ti+Mn)/(Mg+Ca+K+Na)和(CaO+K2O+Na2O)/Al2O3,然后是Fe2O3/MgO和K2O/Al2O3,(CaO+MgO+Na2O)/TiO2比值受沉积物粒度的影响较大,不适合作为指示沉积物化学风化程度的指标。杜蒙沙地的CIA值为52.28,A-CN-K图解指示了杜蒙沙地处于化学风化的最初阶段,处于较弱的脱Ca、Na阶段,其他元素未发生明显化学风化或迁移;A-CNK-FM图解表明杜蒙沙地的Fe、Mg元素仅发生了微弱分异,原因在于半干旱、半湿润气候条件下杜蒙沙地微弱的机械风化,另外杜蒙沙地物质来源决定的短距离搬运也使Fe、Mg元素的分异不明显。The surface sediment samples from Dumeng sandy land were collected and divided into different grain size fractions（bulk sample,63 μm,63-30 μm,30-11 μm and 11 μm）.These samples were analyzed in the laboratory to obtain composition of geochemical elements.The result shows that Si and Al take up a large part of chemical composition of surface sediment in Dumeng sandy land.Compared with the average composition of geochemical elements in the upper continental crust（UCC）,Fe,Mg and Ca are depleted to a severe degree,Al and Na are depleted to a medium degree,and K are depleted slightly;Fe,Mg,Ca,P,Ti and Mn contents have high coefficients of variation;The variation degrees of major elements in different grain size fractions increase in the following order： AlSiNaKPFeTi（Ca,Mn）Mg,and variation of Al element is relatively slight.The volumes of Fe,Mg,Ca,Mn,Ti and P elements gradually increase with decreasing grain size,while the volumes of Si,Na and K are exactly the opposite,and the relationship between Al element and grain size is not significant.The influence of grain size on chemical weathering index is ranked in the following order： CIA（Al＋Fe＋Ti＋Mn）/（Mg＋Ca＋K＋Na）（CaO＋K2O＋Na2O）/Al2O3Fe2O3/MgOK2O/Al2O3（CaO＋MgO＋Na2O）/TiO2.CIA is the best index reflecting chemical weathering degree,and next are（Al＋Fe＋Ti＋Mn）/（Mg＋Ca＋K＋Na） and（CaO＋K2O＋Na2O）/Al2O3,followed by Fe2O3/MgO and K2O/Al2O3,and（CaO＋MgO＋Na2O）/TiO2 ratio is greatly influenced by grain size,so it isn＇t a good index of chemical weathering degree of sediments.The CIA value of Dumeng sandy land is 52.28,A-CN-K ternary diagram shows that these sediments are in the early stage of continental chemical weathering characterized by slight loss of Na and K,and other geochemical elements are in a less weathering or leaching process.A-CNK-FM ternary diagram suggests that Fe and Mg only have undergone slight chemical differentiation because of weak physical weathering and chemical weathering un

关 键 词：粒级组分 地球化学组成 化学风化指标 风化特征 杜蒙沙地 

分 类 号：P596[天文地球—地球化学]