کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
10224342 | 1701096 | 2018 | 62 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Absolute accumulation and isotope fractionation of Si and Fe during dolomite weathering and terra rossa formation
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Absolute accumulation and isotope fractionation of Si and Fe during dolomite weathering and terra rossa formation Absolute accumulation and isotope fractionation of Si and Fe during dolomite weathering and terra rossa formation](/preview/png/10224342.png)
چکیده انگلیسی
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 (Ïfd, %) 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 δ30Si 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 δ30Si 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 δ56Fe values of the FMCs are significantly lower than those of the surrounding terra rossa matrix. These low δ56Fe signatures of the FMCs reflect the preferential translocation of the light Fe isotope, while the FMCs may be able to record the low-δ56Fe characteristics of pore water.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Chemical Geology - Volume 496, 30 September 2018, Pages 43-56
Journal: Chemical Geology - Volume 496, 30 September 2018, Pages 43-56
نویسندگان
Jin-Liang Feng, Le-Le Pei, Xiangkun Zhu, Jian-Ting Ju, Shao-Peng Gao,