柴达木盆地灌丛沙丘稀土元素地球化学特征与物源

doi:10.7522/j.issn.1000-694X.2017.00065

摘要/Abstract

摘要： 分析了柴达木盆地灌丛沙丘剖面风沙沉积物中稀土元素及其相关特征参数、分布模式和（La/Yb）_N-REE（稀土元素）物源特征。结果表明：灌丛沙丘剖面风沙沉积物中REE值100.52~163.47 μg·g^-1，接近于新疆灰钙土，而略低于中国黄土；LREE（轻稀土元素）值87.80~144.65 μg·g^-1，占总量86.62%~90.53%，决定了稀土总量的变化。总体表现为LREE相对富集，而HREE（重稀土元素）丰度相对较低，分馏特征基本相似，呈斜"L"型缓右倾斜，Eu大致呈现中度负异常的分配模式，而Ce未表现出明显异常，且更多地反映了其物源特性。其物源主要由东昆仑北麓冲积扇碎屑沉积物质经过风化、搬运、沉积而成，而并非来自于干旱期的湖底剥蚀物。总体而言，灌丛沙丘沉积过程稀土元素分异特征反映了灌丛沙丘发育时期柴达木盆地总体处于干燥的气候环境，化学风化作用弱，植被发育相对较差，成壤作用不明显。

关键词: 灌丛沙丘, 稀土元素, 地球化学特征, 物源, 柴达木盆地

Abstract: Rare Earth Elements (REE) are widely used as trace elements in provenance studies of various sediments, and their characteristics also can record the evolution of environment more detailly. Therefore, they are widely used as an important indicator in studies of paleoclimate changes. The relationships between REE characteristics and environmental change on aeolian deposits have intensively been investigated in the Chinese Loess Plateau. However, the relationships between REE and paleoenvironment recorded by aeolian sediments of nebkhas in the Qaidam basin are still poorly understood. So the REE characteristics and environmental implication revealed by aeolian sedimental profiles of nebkhas in the Qaidam basin were studied. The results show that REE values of nebkhas' profiles vary from 100.527 μg·g^-1 to 163.47 μg·g^-1, and they are close to the REE values of Xinjiang Sierozem, but slightly lower than the Chinese loess. The LREE values determined the changes of the total content of REE with a range of 87.80~144.65 μg·g^-1, which percentage changes from 86.62% to 90.53%. Overall, the LREE is relative enrichment and relatively low HREE abundance, with similar fractionated characteristics of REE. The distribution patterns of REE are the slowly gradient "L" types, and distribution patterns of Eu elements are moderate negative anomaly, and Ce elements show no obvious abnormality and more reflect their source features. The source of nebkhas sediments is mainly composed of detrital deposits material which come from the alluvial fans located in northern slope of East Kunlun, not from the lakes bottom erosion in the drought periods. After weathering, transportation and deposition, the clastic sediments become the aeolian sediments of nebkhas in southern of the Qaidam basin. The differentiation characteristics of rare earth elements primely record the regional climate and environmental changes by the development of nebkhas in the Qaidam basin. On the whole, the characteristics of REEs revealed dry climate condition in the whole development of nebkhas in the Qaidam basin, with weak chemical weathering, relatively poor vegetation growth condition, and the pedogenesis effect is not obvious.

Key words: nebkhas, rare earth elements(REEs), geochemical characteristics, sediment provenance, Qaidam Basin

中图分类号:

P313.3

凌智永, 王建萍, 陈亮, 芦宝良. 柴达木盆地灌丛沙丘稀土元素地球化学特征与物源[J]. 中国沙漠, 2018, 38(5): 963-971.

Ling Zhiyong, Wang Jianping, Chen Liang, Lu Baoliang. Rare Earth Elements' Geochemical Characteristics of Nebkhas in the Qaidam Basin and the Provenance[J]. Journal of Desert Research, 2018, 38(5): 963-971.

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