He and Ar isotopes in mantle megacryst minerals from Nushan and Yingfengling in Southeast China  

作　　者：XUShijin FANGZhong T.Matsumoto J.Matsuda M.Yasuda YUJinhai WANGRucheng LIUWenzhong 

机构地区：[1]DepartmentofEarthSciences,StateKeyLaboratoryforMineralDepositsResearch,NanjingUniversity,Nanjing210093,China [2]DepartmentofEarthandSpaceSciences,OsakaUniversity,Osaka560-0043,Japan

出　　处：《Chinese Science Bulletin》2003年第15期1624-1630,共7页

基　　金：supported by The National Natural Science Foundation of China(Grant Nos.49473175,49972062 and 40110104104).

摘　　要：He and Ar isotopic compositions of megacrystal minerals from mantle xenoliths were measured by the technique of vacuum crushing extraction. The used samples were clinopyroxene, garnet and ilmenite in Cenozoic alkaline basalts, which were from Nushan in Anhui Province and Yingfengling in Guangdong Province, respectively, and represented materials from the upper mantle in the continental margin of SE China. The results show 3He/4He ratios of 7.99 Ra to 8.58 Ra, consistent with the characteristic ratios of the MORB-type mantle. 40Ar/39Ar ratios vary from 313 to 909, suggesting a binary mixing between the MORB-type mantle and air argons. This may reflect the incorporation of the air argon absorbed in oceanic sediments into the mantle beneath the continental margin by subduction of oceanic plate. This study presents the first report that ilmenite megacrysts contain abundant fluid inclusions and noble gases in the mantle xenoliths.He and Ar isotopic compositions of megacrystal minerals from mantle xenoliths were measured by the technique of vacuum crushing extraction. The used samples were clinopyroxene, garnet and ilmenite in Cenozoic alkaline basalts, which were from Nushan in Anhui Province and Yingfengling in Guangdong Province, respectively, and represented materials from the upper mantle in the continental margin of SE China. The results show 3He/4He ratios of 7.99 Ra to 8.58 Ra, consistent with the characteristic ratios of the MORB-type mantle. 40Ar/39Ar ratios vary from 313 to 909, suggesting a binary mixing between the MORB-type mantle and air argons. This may reflect the incorporation of the air argon absorbed in oceanic sediments into the mantle beneath the continental margin by subduction of oceanic plate. This study presents the first report that ilmenite megacrysts contain abundant fluid inclusions and noble gases in the mantle xenoliths.

关 键 词：东南地区 中国 氦 氩 亏损地幔 

分 类 号：P542.5[天文地球—构造地质学]