Compositions of Noble Gas Isotopes in Different Kinds of Mantle-Derived Rocks and Its Origins, Shandong Province, China
详细信息
- 责任者：Zeng Liang (Key Laboratory of Mineral Resources in Western China ; School of Earth Sciences ; Lanzhou University ; Lanzhou 730000 ; China) ; Cheng Zhiyan
- 刊名：Geological Review
- 出版年：2013
- 卷期：59(4)
- 关键词：惰性气体 ; noble gases ; 同位素组成 ; isotope composition ; 山东 ; Shandong Province
- 页码：p.677-686
- 图表：illus., 2 tables, 78 refs.
- 分类号：0600
- issnNo：ISSN0371-5736
- isbnNo：CN11-1952/P
摘要
Noble gases are efficacious tracers for the origins of the Earth volatiles. Noble gas isotopes in megacrysts, whole rocks of mantle-derived xenoliths and corresponding mineral separates, and host-basalts from Shandong area are tested by heating-melt, and the obtained data indicate that obvious differences in isotopic compositions of noble gases, especially in helium are observed in different kinds of samples. Ratios of n(3He)/ n(4He) in megacrysts and mineral separates, respectively varying from 0.87 to 11.31 Ra and 0.911 to 10.11 Ra, and with corresponding average values of 6.1 Ra and 3.73 Ra, imply a double-source compound of atmosphere and mantle. Ratios of n(3He)/ n(4He) in the whole rocks, ranging from 0.19 to 2.30 Ra (the average is 1.05 Ra) and being lower than those of corresponding mineral separates, suggest that the radiogenic outcome from intergranular ingredients is additional devotion besides primitive mixing of atmosphere—mantle in source area. And with the values of 10-8, the n(3He)/ n(4He) ratios in basalt samples emphasize the role of radiogenic 4He. No clear differences in n(40Ar)/ n(36Ar) , which usually fall in 296.4~864.3 and are a bit higher than that in the atmosphere but far lower than that in the mantle, are detected in different kinds of samples. All ratios of n(20Ne)/n(22Ne) in different kinds of samples are higher than atmosphere, which show characteristics of mantle-derived origins, and as a whole, n(20Ne)/n(22Ne) in basalts (11.07~13.10) are slightly higher than those in the whole rocks and corresponding mineral separates, separately ranging from 10.19 to 12.42 and 10.55 to 11.80 and showing no visible differences. Those characteristics and differences of noble gas isotopes suggest different origins and evolution processes for different kinds of samples.