A Study on Elemental Geochemical Characters of the Wuwei Loess Section in the South Vicinity of Tengger Desert
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摘要: 对腾格里沙漠南缘武威黄土剖面１８个样品系统的元素地球化学分析结果表明，剖面中８种常量元素氧化物总量平均值为８８.９９%，且整个剖面中变化微弱（８７.２６%～９０.４６%），显示了构成武威黄土物质组成的均一性；反映风化程度的Ｆｅ２Ｏ３/ＦｅＯ和Ａｌ２Ｏ３/ＳｉＯ２，值变化较为明显，平均值分别为１.４６（１.０２～２.８６）和０.１９（０.１７～０.２２）；稀土元素总含量平均值为１８５.４２（１６９.３１～１９９.８２）μｇ/ｇ，稀土分布斜率较大、有较明显Ｅｕ异常，ΣＬＲＥＥ/ΣＨＲＥＥ值平均为８.２３（７.３８～９.６０），表现出较显著的轻重稀土的分镏作用，指示着一定程度的风化作用；而代表原岩特征的稀土参数Ｅｕ/Ｓｍ、Ｓｍ/Ｎｄ、Ｎｄ/Ｌａ、δＣｅ、δＥｕ等变化不大，反映了不同时代黄土物质来源的一致性Abstract: The elemental geochmical analysis results on 18 samples taken from a 115m thick loess sectionwhich is located in Wuwei on the south vicinity of Tengger Desert, showed that the 8 common elementaloxides make up 88.99 % of the material with a very narrow variable range, from 87.26 to 90.46 per cent,indicating the Similarity of the loess material in the whole section.The average weathering indices ex-pressed by the ratios of Fe 2 O 3 /FeO and Al 2 O 3 /SiO 2 are 1.46 and 0.19, ranging from 1.02 to 2.86 and0.17 to 0.22, respectively.The average content of REE is 185.42 μ g /g, ranging from 169.31 to199.82 μ g /g and the REE distribution pattern is of a relatively big slope and obvious anomal and of Eu,in the reference with the ratio of LREE/HREE, which is 8.23 averagely, ranging from 7.38 to 9.60 andshowing a relatively stong fractionation which indicates a considerable degree of weathering.At thesametime, the indices of Eu /Sm, Sm /Nd, Nd /La,δ Eu andδ Ce proved that the loess materials of differentages are transported from a common source area that is similar to the typical loess in Loess Plateau.
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Key words:
- loess /
- elemental geochemistry /
- source area of loess material
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