Germanium isotopes and Ge/Si fractionation under extreme tropical weathering of basalts from the Hainan Island, South China

CORC > 地球化学研究所 > 中国科学院地球化学研究所 > 矿床地球化学国家重点实验室

	Germanium isotopes and Ge/Si fractionation under extreme tropical weathering of basalts from the Hainan Island, South China
	Hua-Wen Qi ; Rui-Zhong Hu ; Ke Jiang ; Ting Zhou ; Yue-Fu Liu ; Yan-Wen Xiong
刊名	Geochimica et Cosmochimica Acta
	2019
卷号	253 页码:249–266
关键词	Ge Isotopes Ge/si Ratio Chemical Weathering Basalt Hainan Island (South China)
英文摘要	Chemical weathering of silicate rocks controls the flfluvial input of dissolved Ge and Si into the ocean, and has substantial inflfluence on the global Ge and Si geochemical cycles. The heavier dissolved Ge isotope compositions in the rivers (relative to the bulk silicate earth) suggest preferential incorporation of light isotopes into secondary weathering products during rock weathering (Baronas et al., 2017a). In this paper, we present the Ge isotope and Ge/Si ratio variations in the solid weathering products (soil and saprolite) from a well-developed basalt weathering profifile (>15 m thick, including soil, saprolite, semi weathered rock and fresh basalt) on the tropical island of Hainan (South China). We discussed the elemental/isotopic fractionation mechanism and the possible inflfluence of major oxide composition on Ge isotope fractionation during extreme weathering of basalts in tropical climate. The Ge content ([Ge] = 2.19–4.12 ppm, 2.93 ppm on average, n = 52) and Ge/Si ratios (5.55–13.7 lmol/mol, 7.42 lmol/mol on average, n = 52) of solid weathering products are distinctly higher than those of the fresh basalts (avg. [Ge] = 1.64 ppm, Ge/Si = 2.66 lmol/mol, n = 5). The d74Ge values of solid weathering products range from 0.02 ± 0.10‰ (2r) to 0.63 ± 0.10‰ (2r), and exhibits complex stratigraphic variation across the weathering profifile. There are no distinct correlations between the concentrations of Ge (or the Ge/Si ratio and d74Ge values) and SiO2, Al2O3, Fe2O3 and MnO for most of the soil and saprolite samples. The distinct positive d74Ge vs. Ge (or sGe value and Ge/Si ratio) correlations for most soil and saprolite samples indicate that the enrichment (or depletion) of Ge content, Ge isotopes and Ge/Si fractionation are controlled by a common sorption process of solid weathering products. The predicted opposite relationships between Ge/Si ratios and d74Ge values for pore water and that for solid weathering products can be evidenced by the positive Ge/Si vs. d74Ge correlation in the Wenchang basalt weathering profifile and a negative one in the river water (Baronas et al., 2017a). Moreover, the estimated negative D74Gesolid-dissolved (1000 * Ln(a)) value (1.38 ± 0.28‰ (2r)) indicates that solid weathering products are a sink for light Ge isotopes, possibly balancing the isotopic budget with heavy Ge isotope compositions in global rivers and oceans.
语种	英语
内容类型	期刊论文
源URL	[http://ir.gyig.ac.cn/handle/42920512-1/10142]
专题	地球化学研究所_矿床地球化学国家重点实验室
通讯作者	Hua-Wen Qi
作者单位	1.University of Chinese Academy of Sciences, Beijing 100049, China 2.State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
推荐引用方式 GB/T 7714	Hua-Wen Qi,Rui-Zhong Hu,Ke Jiang,et al. Germanium isotopes and Ge/Si fractionation under extreme tropical weathering of basalts from the Hainan Island, South China[J]. Geochimica et Cosmochimica Acta,2019,253:249–266.
APA	Hua-Wen Qi,Rui-Zhong Hu,Ke Jiang,Ting Zhou,Yue-Fu Liu,&Yan-Wen Xiong.(2019).Germanium isotopes and Ge/Si fractionation under extreme tropical weathering of basalts from the Hainan Island, South China.Geochimica et Cosmochimica Acta,253,249–266.
MLA	Hua-Wen Qi,et al."Germanium isotopes and Ge/Si fractionation under extreme tropical weathering of basalts from the Hainan Island, South China".Geochimica et Cosmochimica Acta 253(2019):249–266.