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山东地区新生代不同类型幔源样品中稀有气体同位素组成与成因
  • ISSN号:0371-5736
  • 期刊名称:地质论评
  • 时间:2013.7.15
  • 页码:677-686
  • 分类:P588.121[天文地球—岩石学;天文地球—地质学]
  • 作者机构:[1]兰州大学地质科学与矿产资源学院&甘肃省西部矿产资源重点实验室,兰州730000
  • 相关基金:国家自然科学基金资助项目(编号41173014);甘肃省自然科学基金资助项目(编号1010RJZA113)的成果
  • 相关项目:甘肃文县阳山金矿中稀有气体同位素及其与流体主要组分的多元综合示踪
中文摘要:

稀有气体是地球流体源区信息的有效示踪剂。利用热熔融法对山东地区幔源巨晶、包体全岩及其单矿物以及寄主玄武岩等幔源样品中稀有气体的测试表明,不同类型样品具有明显不同的稀有气体同位素组成,特别是He同位素比值差异明显。巨晶和包体单矿物中的n(3He)/n(4He)值分别为0.87~11.31Ra、0.911~10.11Ra,均值分别为6.1Ra和3.73Ra,主体介于地幔—大气—地壳源区之间;包体全岩中n(3He)/n(4He)值0.19~2.30Ra(均值为1.05Ra),且均低于相应单矿物中该比值;而玄武岩中n(3He)/n(4He)值全为10-8数量级,与地壳均值无异。各类幔源样品中n(40Ar)/n(36Ar)值无明显差异,介于296.4~864.3,高于大气但远低于典型地幔值。所获有限数据中,不同类型样品中n(20Ne)/n(22Ne)值均高于大气,具幔源特征,其中包体全岩及其单矿物n(20Ne)/n(22Ne)值分别为10.19~12.42和10.55~11.80,无明显差异;玄武岩中该值介于11.07~13.10,总体高于包体全岩及其单矿物。上述比值特征的差异反映了不同类型幔源样品各自不同的成因和演化特征:巨晶和包体单矿物中的轻稀有气体同位素组成主要反映了由于古板块俯冲所导致的岩浆源区地幔—大气/地壳的混合特征,个别样品中可能存在宇宙成因3He;除单矿物中所体现的源区混合特征外,包体全岩还存在放射成因4He;而玄武岩在喷出地表后丢失大量地幔稀有气体信息,其同位素组成主要体现了放射成因4He的影响。

英文摘要:

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.

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期刊信息
  • 《地质论评》
  • 北大核心期刊(2011版)
  • 主管单位:中国科学技术协会
  • 主办单位:中国地质学会
  • 主编:杨文采
  • 地址:北京阜成门外百万庄路26号中国地质学会期刊处
  • 邮编:100037
  • 邮箱:georeview@cags.ac.cn
  • 电话:010-68999804
  • 国际标准刊号:ISSN:0371-5736
  • 国内统一刊号:ISSN:11-1952/P
  • 邮发代号:2-382
  • 获奖情况:
  • 中国期刊方阵“双效”期刊
  • 国内外数据库收录:
  • 美国化学文摘(网络版),美国地质文献预评数据库,日本日本科学技术振兴机构数据库,中国中国科技核心期刊,中国北大核心期刊(2004版),中国北大核心期刊(2008版),中国北大核心期刊(2011版),中国北大核心期刊(2014版),中国北大核心期刊(2000版)
  • 被引量:23413