Absolute accumulation and isotope fractionation of Si and Fe during dolomite weathering and terra rossa formation | |
Feng, JL (Feng, Jin-Liang)1; Pei, LL (Pei, Le-Le)1,2; Zhu, XK (Zhu, Xiangkun)3; Ju, JT (Ju, Jian-Ting)1; Gao, SP (Gao, Shao-Peng)1 | |
刊名 | CHEMICAL GEOLOGY |
2018-09-30 | |
卷号 | 496期号:0页码:43-56 |
关键词 | Yunnan-guizhou Plateau Iron-oxide Mineralogy Rare-earth-elements Silicon Isotopes Soil Chronosequence Geochemical Cycle Dissolved Silicon Genesis Basalt China |
ISSN号 | 0009-2541 |
DOI | 10.1016/j.chemgeo.2018.08.018 |
英文摘要 | The behavior of silicon (Si) and iron (Fe) and their isotope fractionation during carbonate weathering and terra rossa formation are unclear. Here, we focus on a 4.05-m-thick terra rossa profile developed on dolomite in the Yunnan-Guizhou Plateau, China. We measured the mineral and geochemical composition, magnetic susceptibility and Si and Fe isotopic composition of the terra rossa, ferromanganese concretions (FMCS), and the dolomite and its insoluble residues. The results indicate that there is absolute accumulation of Si and Fe during dolomite weathering and terra rossa formation, due to the extraneous input of dissolved Si and Fe. This means that the insoluble residues of dolomite are not the only source for terra rossa formation. In addition, we suggest that the high frequency-dependent magnetic susceptibility (chi(fd), %) and rubification of the terra rossa are the result of the oxidation of extraneous dissolved Fe and the neoformation of finely dispersed Fe oxides. Overall, the terra rossa is characterized by the enrichment of light Si and Fe isotopes, compared with insoluble dolomite residues and bulk dolomite. The extraneous input of dissolved Fe is characterized by a light isotopic signature, whereas the Si isotopic signature of the extraneous source is unclear due to modification by late desilicification. Si isotope fractionation in the terra rossa is mainly controlled by chemical weathering and associated mobilization and redistribution of Si. The delta Si-30 values of terra rossa decrease with increasing weathering intensity, while the re-precipitation of mobilized Si leads to the significant enrichment of isotopically heavy Si in the basal terra rossa. The delta Si-30 values of terra rossa are not significantly affected by the adsorption of the Fe and Al (oxyhydr)oxides. By contrast, the major process that fractionates Fe isotopes in the dolomite-terra rossa weathering system is unclear. In the terra rossa profile, the delta Fe-56 values of the FMCS are significantly lower than those of the surrounding terra rossa matrix. These low delta Fe-56 signatures of the FMCS reflect the preferential translocation of the light Fe isotope, while the FMCS may be able to record the low-delta Fe-56 characteristics of pore water. |
学科主题 | 地理学 |
WOS研究方向 | Geochemistry & Geophysics |
语种 | 英语 |
出版者 | ELSEVIER SCIENCE BV |
WOS记录号 | WOS:000444923600005 |
内容类型 | 期刊论文 |
源URL | [http://ir.itpcas.ac.cn/handle/131C11/8541] |
专题 | 青藏高原研究所_图书馆 |
通讯作者 | Feng, JL (Feng, Jin-Liang) |
作者单位 | 1.Chinese Acad Sci, Inst Tibetan Plateau Res, Key Lab Tibetan Environm Changes & Land Surface P, Beijing 100101, Peoples R China; 2.Univ Chinese Acad Sci, Beijing 100049, Peoples R China; 3.Chinese Acad Geol Sci, Inst Geol, MNR Key Lab Isotope Geol, Beijing 100037, Peoples R China. |
推荐引用方式 GB/T 7714 | Feng, JL ,Pei, LL ,Zhu, XK ,et al. Absolute accumulation and isotope fractionation of Si and Fe during dolomite weathering and terra rossa formation[J]. CHEMICAL GEOLOGY,2018,496(0):43-56. |
APA | Feng, JL ,Pei, LL ,Zhu, XK ,Ju, JT ,&Gao, SP .(2018).Absolute accumulation and isotope fractionation of Si and Fe during dolomite weathering and terra rossa formation.CHEMICAL GEOLOGY,496(0),43-56. |
MLA | Feng, JL ,et al."Absolute accumulation and isotope fractionation of Si and Fe during dolomite weathering and terra rossa formation".CHEMICAL GEOLOGY 496.0(2018):43-56. |
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