Abstract

The main geochemical characteristics of gray silts of the Volga Reservoir cascade are discussed. Together with sandy varieties, they occupy more than 60% of the total bottom area in some reservoirs. Gray silt samples were taken in the first half of June 2016 during an expedition from the Borok Port to the Astrakhan Port on the R/V Akademik Topchiev. It is shown that the content of Ni, Cr, Y, and Sr in gray silts increases from the Rybinsk Reservoir to the Kuibyshev Reservoir, and gradually decreases downstream. On the contrary, the Ba and Zn contents remain almost unchanged downstream the reservoir cascade. Values of a number of indicator ratios (Cr/Th, Th/Sc, and others) behave approximately the same way. In general, the content of trace elements in the studied gray silt samples is lower than in the Post-Archean Australian Shale (PAAS). Hence, the grain size composition of gray silts and the PAAS is most likely somewhat different because of certain diluting effect of the nonclay component. Gray silts sampled from the Kama River mouth opposite the Atabaevo Settlement (station 39) are characterized by a significantly lower (La/Yb)_N value than other samples studied in this work, indicating a fundamentally different (probably, Uralian?) source of the aluminosiliciclastic material in this sample.

中文翻译：

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伏尔加水库梯级的灰色淤泥：地球化学的主要特征

摘要

讨论了伏尔加水库梯级灰泥的主要地球化学特征。与砂质品种一起，在一些水库中占总底部面积的 60% 以上。2016 年 6 月上半月，在 R/V Akademik Topchiev从 Borok 港到阿斯特拉罕港的一次探险中采集了灰色淤泥样本. 结果表明，从雷宾斯克水库到古比雪夫水库，灰色淤泥中Ni、Cr、Y、Sr的含量逐渐增加，向下游逐渐降低。相反，在储层梯级下游，Ba 和 Zn 含量几乎保持不变。许多指标比率（Cr/Th、Th/Sc 等）的值表现大致相同。一般来说，所研究的灰色粉砂样品中的微量元素含量低于太古代后澳大利亚页岩（PAAS）中的含量。因此，由于非粘土组分的某些稀释作用，灰色粉砂和 PAAS 的粒度组成很可能有些不同。从 Atabaevo 定居点（第 39 站）对面的卡马河口采集的灰色淤泥的特征是 (La/Yb) _{N显着降低}值比这项工作中研究的其他样品，表明该样品中铝硅碎屑材料的根本不同（可能是乌拉尔？）来源。