气候变化领域集成服务门户(CCPortal): Absolute accumulation and isotope fractionation of Si and Fe during dolomite weathering and terra rossa formation

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DOI	10.1016/j.chemgeo.2018.08.018
	Absolute accumulation and isotope fractionation of Si and Fe during dolomite weathering and terra rossa formation
	Feng, Jin-Liang; Pei, Le-Le; Zhu, Xiangkun; Ju, Jian-Ting; Gao, Shao-Peng
通讯作者	Feng, JL (通讯作者)
发表日期	2018
ISSN	0009-2541
EISSN	1872-6836
起始页码	43
结束页码	56
卷号	496
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.
关键词	YUNNAN-GUIZHOU PLATEAU IRON-OXIDE MINERALOGY RARE-EARTH-ELEMENTS SILICON ISOTOPES DISSOLVED SILICON GENESIS CONCRETIONS CONSTRAIN ORIGIN SOILS
英文关键词	Dolomite; Terra rossa; Chemical weathering; Silicon isotopes; Iron isotopes; Extraneous input
语种	英语
WOS研究方向	Geochemistry & Geophysics
WOS类目	Geochemistry & Geophysics
WOS记录号	WOS:000444923600005
来源期刊	CHEMICAL GEOLOGY
来源机构	中国科学院青藏高原研究所
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/259197
推荐引用方式 GB/T 7714	Feng, Jin-Liang,Pei, Le-Le,Zhu, Xiangkun,et al. Absolute accumulation and isotope fractionation of Si and Fe during dolomite weathering and terra rossa formation[J]. 中国科学院青藏高原研究所,2018,496.
APA	Feng, Jin-Liang,Pei, Le-Le,Zhu, Xiangkun,Ju, Jian-Ting,&Gao, Shao-Peng.(2018).Absolute accumulation and isotope fractionation of Si and Fe during dolomite weathering and terra rossa formation.CHEMICAL GEOLOGY,496.
MLA	Feng, Jin-Liang,et al."Absolute accumulation and isotope fractionation of Si and Fe during dolomite weathering and terra rossa formation".CHEMICAL GEOLOGY 496(2018).