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Distribution of rare earth elements in sediments of the North China Plain: A probe of sedimentation process
Applied Geochemistry ( IF 3.1 ) Pub Date : 2021-09-02 , DOI: 10.1016/j.apgeochem.2021.105089
Haiyan Liu 1, 2 , Huaming Guo 3 , Olivier Pourret 4 , Zhen Wang 1, 2 , Zhanxue Sun 1, 2 , Weimin Zhang 1, 2 , Maohan Liu 1
Affiliation  

Rare earth elements (REE) are powerful tracers for our understanding of sedimentary provenance and depositional processes. This study investigated geochemical characteristics of REE in 226 sediment samples collected from the piedmont, central and littoral plains of the North China Plain. Results showed that total REE concentrations exhibited a decreasing trend as piedmont > central > littoral, and 82%, 70% and 67% samples had total REE concentrations higher than the value of upper continental crust. The REE concentrations were controlled by sedimentary provenance and sediment physicochemical properties. Ternary diagrams of sandstone classification and Al2O3–CaO + Na2O–K2O reflected that sediments originated from greywackes and they experienced an incipient to intermediate chemical weathering. Average chemical index of alteration (CIA) value was 68, 51 and 55 for sediments from piedmont, central and littoral plains, respectively. Sediment North American Shale Composite (NASC)-normalized patterns were characterized by light REE (LREE) enrichment over heavy REE (HREE) and coherent negative Eu anomaly (Eu/Eu* ranging between 0.57 and 1.00). Value of (La/Yb)NASC ranged from 0.86 to 1.15 (average 1.23), and from 1.03 to 1.49, and from 0.91 to 1.49 in three zones, respectively, indicating REE fractionation occurred from piedmont to littoral during sedimentation processes. A positive correlation between (La/Yb)NASC and total REE concentrations was observed in piedmont and central sediment samples, implying that LREE were preferentially enriched over HREE with an accumulation of REE. This positive correlation was not found in littoral sediment samples, where a general decreasing trend along depth for REE concentrations existed. The findings of this study have an implication for using REE as a tracer in provenance studies from a basin scale.



中文翻译:

华北平原沉积物中稀土元素的分布:沉积过程探析

稀土元素 (REE) 是我们了解沉积物源和沉积过程的有力示踪剂。本研究调查了从华北平原山麓、中部和沿海平原采集的 226 份沉积物样品中稀土元素的地球化学特征。结果表明,稀土元素总浓度呈山前>中部>沿海递减趋势,82%、70%和67%的样本稀土元素总浓度高于陆壳上部。REE浓度受沉积物源和沉积物理化性质控制。砂岩分类与Al 2 O 3 –CaO + Na 2 O–K 2三元图O 反映沉积物起源于灰岩,它们经历了初期到中间的化学风化。山前、中部和沿海平原沉积物的平均化学蚀变指数 (CIA) 值分别为 68、51 和 55。沉积物北美页岩复合材料 (NASC) 归一化模式的特征在于轻稀土 (LREE) 富集超过重稀土 (HREE) 和相干负 Eu 异常 (Eu/Eu* 范围在 0.57 和 1.00 之间)。(La/Yb) NASC值在三个区域分别为 0.86 至 1.15(平均 1.23)、1.03 至 1.49 和 0.91 至 1.49,表明在沉积过程中从山麓到沿海发生了 REE 分馏。(La/Yb) NASC之间的正相关在山前和中央沉积物样品中观察到总 REE 浓度,这意味着随着 REE 的积累,LREE 优先于 HREE 富集。在沿海沉积物样品中没有发现这种正相关,其中 REE 浓度沿深度存在普遍下降的趋势。本研究的结果对在盆地尺度的物源研究中使用 REE 作为示踪剂具有重要意义。

更新日期:2021-09-07
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