Some Features of Rare-Earth Element Distribution in Surface Sediments of the Bay of Tonkin (South China Sea)

IF 0.9 4区地球科学 Q4 GEOSCIENCES, MULTIDISCIPLINARY

Russian Journal of Pacific Geology Pub Date : 2024-02-04 DOI:10.1134/s1819714023080080

A. A. Legkodimov, A. V. Sorochinskaya, R. B. Shakirov

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Abstract

The peculiarities of the distribution of rare-earth elements (REEs) in the surface bottom sediments in the Gulf of Tonkin (South China Sea) are considered. According to the results of granulometric analysis, the sediments are mainly represented by pelitic silt, silty pelite, and miktites. The REE contents normalized to the chondrite composition show the absence of cerium anomaly, the presence of negative europium anomaly and significant fractionation of light and heavy REEs. The values of indicator ratios La_N/Yb_N, Cr/Th, Th/Co, La/Sc, and Th/Sc indicate the predominance of rocks of intermediate and acidic composition in the erosion areas, due to which sediments were formed. The values of the Ce/La and (Fe + Mn)/Ti ratios characterize the surface sediments as typically terrigenous without the admixture of endogenous exhalative material. The Eu/Sm ratio values indicate low permeability of the sediments for upward fluid flows, which is consistent with the measured methane concentrations. The analysis of correlations indicates the dominance of the terrigenous source of REEs and that clay minerals and iron hydroxides play a significant role in the migration and accumulation of REEs.

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北部湾（中国南海）表层沉积物中稀土元素分布的一些特征

摘要研究了北部湾（中国南海）表层底沉积物中稀土元素（REEs）分布的特殊性。根据粒度分析的结果，沉积物主要以球粒粉砂、粉砂质球粒岩和米克替岩为代表。按软玉成分归一化的 REE 含量显示没有铈异常，存在负铕异常，轻重 REE 存在明显的分馏。指标比率LaN/YbN、Cr/Th、Th/Co、La/Sc和Th/Sc的数值表明，侵蚀区主要是中酸性成分的岩石，沉积物就是在这种成分的作用下形成的。Ce/La和（Fe + Mn）/Ti的比率值表明地表沉积物是典型的陆相沉积，不掺杂内源外渗物质。Eu/Sm比率值表明沉积物向上流体流动的渗透性较低，这与测量到的甲烷浓度相符。相关性分析表明，REEs 的主要来源是陆相来源，粘土矿物和铁氢氧化物在 REEs 的迁移和积累过程中发挥了重要作用。

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来源期刊

Russian Journal of Pacific Geology 地学-地球科学综合

CiteScore

1.30

自引率

37.50%

发文量

审稿时长

>12 weeks

期刊介绍： Russian Journal of Pacific Geology publishes the results of research on the Earth crust and mantle composition and provides articles on the geological structure and patterns of distribution of mineral deposits in the Pacific Ocean, marginal seas and continental margins. It discusses the topics of stratigraphy, sedimentology, magmatic activity, and seismicity. The journal deals with the problems of lithosphere plates tectonics, and offers the results of neotectonic, geomorphological, geodesic, environmental and mining studies in the Pacific region. The journal accepts theoretical, methodical and philosophical articles covering general issues of geology, geophysics, geochemistry, geoecology and mining. The journal also publishes critical notes and comments, and reviews.