Selenium speciation in Lower Cambrian Se-enriched strata in South China and its geological implications

	Selenium speciation in Lower Cambrian Se-enriched strata in South China and its geological implications
	Haifeng Fan; Hanjie Wen; Ruizhong Hu; Hui Zhao
	2011
发表期刊	Geochimica et Cosmochimica Acta
卷号	75 期号:23 页码:7725-7740
摘要	To understand the impact of Selenium (Se) into the biogeochemical cycle and implications for palaeo-redox environment, a sequential extraction method was utilized for samples including black shales, cherts, a Ni-Mo-Se sulfide layer, K-bentonite and phosphorite from Lower Cambrian Se-enriched strata in southern China. Seven species (water-soluble, phosphate exchangeable, base-soluble, acetic acid-soluble, sulfide/selenide associated, residual Se) and different oxidation states (selenate Se(VI), selenite Se(IV), organic Se, Se (0) and mineral Se(-II)) were determinated in this study. We found that the Ni-Mo-Se sulfide layer contained a significantly greater amount of Se(-II) associated with sulfides/selenides than those in host black shales and cherts. Furthermore, a positive correlation between the degree of sulfidation of iron (DOS) and the percentage of the sulfide/selenide-associated Se(-II) was observed for samples, which suggests the proportion of sulfide/selenide-associated Se(-II) could serve as a proxy for palaeo-redox conditions. In addition, the higher percentage of Se(IV) in K-bentonite and phosphorite was found and possibly attributed to the adsorption of Se by clay minerals, iron hydroxide surfaces and organic particles. Based on the negative correlations between the percentage of Se(IV) and that of Se(-II) in samples, we propose that the K-bentonite has been altered under the acid oxic conditions, and the most of black shale (and cherts) and the Ni-Mo-Se sulfide layer formed under the anoxic and euxinic environments, respectively. Concerning Se accumulation in the Ni-Mo-Se sulfide layer, the major mechanism can be described by (1) biotic and abiotic adsorption and further dissimilatory reduction from oxidized Se(VI) and Se(IV) to Se(-II), through elemental Se, (2) contribution of hydrothermal fluid with mineral Se(-II).
学科领域	矿床地球化学
收录类别	SCI
语种	英语
文献类型	期刊论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/4903
专题	矿床地球化学国家重点实验室_矿床地球化学国家重点实验室_期刊论文矿床地球化学国家重点实验室
推荐引用方式 GB/T 7714	Haifeng Fan,Hanjie Wen,Ruizhong Hu,et al. Selenium speciation in Lower Cambrian Se-enriched strata in South China and its geological implications[J]. Geochimica et Cosmochimica Acta,2011,75(23):7725-7740.
APA	Haifeng Fan,Hanjie Wen,Ruizhong Hu,&Hui Zhao.(2011).Selenium speciation in Lower Cambrian Se-enriched strata in South China and its geological implications.Geochimica et Cosmochimica Acta,75(23),7725-7740.
MLA	Haifeng Fan,et al."Selenium speciation in Lower Cambrian Se-enriched strata in South China and its geological implications".Geochimica et Cosmochimica Acta 75.23(2011):7725-7740.

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