Fe isotopic composition of the Quaternary Red Clay in subtropical Southeast China: Redoxic Fe mobility and its paleoenvironmental implications
Fe isotopic composition of the Quaternary Red Clay in subtropical Southeast China: Redoxic Fe mobility and its paleoenvironmental implications
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中国东南亚热带第四纪红粘土的铁同位素组成：氧化还原铁迁移率及其古环境意义
DOI：
10.1016/j.chemgeo.2019.07.010
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发表时间：
2019-10
期刊：
影响因子：
3.9
通讯作者：
Liu Xiang-Jun
中科院分区：
文献类型：
--
作者：
Hu Xue-Feng;Zhao Jing-Long;Zhang Pei-Feng;Xue Yong;An Bo-Nian;Huang Fang;Yu Hui-Min;Zhang Gan-Lin;Liu Xiang-Jun
To probe Fe isotopic signatures of the Quaternary Red Clay (QRC) in subtropical southeastern China, two QRC profiles located in southern Anhui Province, Southeast China, were studied. The whole profiles were generally in a narrow range in δ56Fe of −0.040 ± 0.061‰—0.117 ± 0.048‰. The Yellow-brown Earth (YBE) and Uniform Red Clay (URC) of the upper profiles were similar in δ56Fe to the Xiashu Loess along the Yangtze River, Southeast China, and the loess, paleosols and Tertiary red clay in the Chinese Loess Plateaus, Northwest China, as well as the baseline of terrestrial igneous rocks. The slight variation of δ56Fe from the YBE to the URC suggests that the chemical weathering and rubification on the aerobic surface did not fractionate Fe isotopes significantly. The Reticulate Red Clay (RRC) underlying the YBE and URC fluctuated in δ56Fe to some extent. The white veins separated from the lower RRC were depleted of Fe oxides and heavier in Fe isotopes, and the red veins, on the contrary, were isotopically lighter in Fe. δ56Fe of the white veins, 0.345 ± 0.053‰ on average, was significantly higher than the bulk samples, 0.033 ± 0.044‰ on average, and the red veins, −0.021 ± 0.046‰ on average. This suggests that the reticulate textures of the RRC were formed by the reductive removal/re-precipitation of Fe due to the cyclical changes of redoxic conditions. Fe isotopic composition of the QRC was dominantly controlled by the redoxic mobility of Fe, rather than the degree of weathering. δ56Fe of the profiles was not correlated with the paleoclimatic events, and thus cannot be used as a paleoclimatic proxy. The fractionation of Fe isotopes in the lower RRC, however, indicated the occurrence of over-humid paleoclimate with alternations between drought and wetness in Southern China during the Pleistocene.
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