Geochemical constraints on provenance of the mid-Pleistocene red earth sediments in subtropical China
Geochemical constraints on provenance of the mid-Pleistocene red earth sediments in subtropical China
复制标题
中国亚热带中更新世红土沉积物物源的地球化学约束
DOI：
10.1016/j.sedgeo.2013.03.008
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发表时间：
2013-05-15
影响因子：
2.8
通讯作者：
Li, Zhaohui
中科院分区：
文献类型：
--
作者：
Hong, Hanlie;Wang, Chaowen;Li, Zhaohui
根据长江中下游地区中更新世红土沉积物的地球化学特征，探讨了其物源。宣城和九江红土沉积物具有相似的常量和微量元素分布模式。与中国黄土高原的黄土和古土壤、上陆壳（UCC）和澳大利亚后太古代平均页岩（PAAS）相比，沉积物中CaO、MgO、Na 2 O明显亏损，而TiO 2、Al 2 O3和Fe 2 O3（t）明显富集。红土沉积物的微量元素分布模式也不同于黄土和PAAS，但与黄土沉积物的分布模式相似，只是移动的微量元素Sr、Ba和Ni的值较低，而Zr和Y的值较高。红土样品具有均匀的La/Th比值，接近2.8，与UCC、黄土和古土壤的La/Th比值一致。它们也具有相似的重稀土配分模式，具有富集轻稀土和相对平坦的重稀土剖面，并具有一致的负Eu异常，与UCC、黄土和古土壤以及扬子矿床相似。这些结果表明，红土沉积物已受到相当大的混合之前，沉积和强烈的随后的化学风化。沉积物中Nd-143/Nd-144和Sm-147/Nd-144的比值非常均匀，表明沉积物具有良好的混合和多次循环。红土沉积物的Nd-143/Nd-144和Sr-87/Sr-86值与长江中下游沉积物的Nd-143/Nd-144和Sr-87/Sr-86值吻合较好，但与黄土和古土壤的Nd-143/Nd-144和Sr-87/Sr-86值不同。这表明红土沉积物来自长江中下游流域，经历了比长江沉积物更强烈的化学风化作用，表现为Rb/Sr比值较高，移动的元素强烈亏损，非移动的元素富集，网状结构发育。(c)2013爱思唯尔有限公司版权所有。
The source of mid-Pleistocene red earth sediments in the middle to lower reaches of the Yangtze (Changjiang) River was investigated based on their geochemical characteristics. The Xuancheng and Jiujiang red earth sediments have similar major and trace element distribution patterns. Compared to the loess and paleosol deposits of the Chinese Loess Plateau, the upper continental crust (UCC), and the post-Archean Australian average shale (PAAS), the sediments display notable depletion of CaO, MgO, Na2O, and accumulation of TiO2, Al2O3, and Fe2O3(t). The trace element distribution patterns of the red earth sediments are also different from those of loess and the PAAS, but are similar to those of the loess deposits, except for lower values of mobile trace elements Sr, Ba, and Ni, and higher values of Zr and Y. The red earth samples have uniform La/Th ratios of similar to 2.8, compatible with those of the UCC, loess, and paleosol. They also have similar chondrite-normalized REE patterns, characterized by enriched LREE and relatively flat HREE profiles, and consistent negative Eu anomalies, similar to those of the UCC, the loess and paleosol, and the Yangtze deposits. These results suggest that the red earth sediments have been subject to considerable mixing prior to deposition and strong subsequent chemical weathering. The sediments have very uniform Nd-143/Nd-144 and Sm-147/Nd-144 ratios, this points to well-mixed and multi-recycled sediments. The Nd-143/Nd-144 and Sr-87/Sr-86 values of the red earth sediments match well with those of the deposits in the middle to lower reaches of the Yangtze River, but are different from those of the loess and paleosols. This suggests that the red earth sediments are derived from the drainage basins of the middle to lower Yangtze River and might have experienced more intense chemical weathering relative to the Yangtze deposits, as reflected by their higher Rb/Sr ratios, intense depletion of mobile elements and accumulation of immobile elements, as well as their well-developed net-like structure. (c) 2013 Elsevier B.V. All rights reserved.