Extreme 3He/4He ratios in northwest Iceland: constraining the common component in mantle plumes
Extreme 3He/4He ratios in northwest Iceland: constraining the common component in mantle plumes
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DOI：
10.1016/s0012-821x(99)00215-0
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发表时间：
1999-11
影响因子：
5.3
通讯作者：
D. Hilton;K. Grönvold;C. Macpherson;P. Castillo
中科院分区：
文献类型：
--
作者：
D. Hilton;K. Grönvold;C. Macpherson;P. Castillo
来自冰岛西北部Selardalur的晚第三纪玄武岩中的橄榄石和单斜辉石斑晶携带的挥发物具有迄今报道的最高的氦同位素比率。在三个不同的样品上测量并在真空中阶梯粉碎提取的3He/4He比值一致地下降到˜37Ra(RA=air3He/4He)-显著高于以前报道的冰岛或Loihi海山的值(见K.A.Farley，E.Neroda[Annu。地球牧师星球。SCI。26(1998)189-218])。同一样品的锶、钕和铅同位素组成使其位于Hart等人的地幔四面体的中心。(S.R.Hart，E.H.Hauri，L.A.Oschehead，J.A.Whitehead[Science 256(1992)517-520])-根据世界各地洋岛玄武岩伪线性排列的汇聚，准确预测共同地幔端元的区域(E.H.Hauri，J.A.Whitehead，S.R.Hart[J.GePhys.第99号决议(1994年)24275-24300])。这一观察结果表明，Selardalur可能是迄今为止对许多地幔热柱共有的第5个地幔成分的He-Sr-Nd-Pb同位素组成的最好估计。
Olivine and clinopyroxene phenocrysts contained in late Tertiary basalts from Selardalur, northwest Iceland, carry volatiles with the highest helium isotope ratio yet reported for any mantle plume.3He/4He ratios measured on three different samples and extracted by stepped crushing in vacuo fall consistently ˜37 RA(RA= air3He/4He) — significantly higher than previously reported values for Iceland or Loihi Seamount (see K.A. Farley, E. Neroda [Annu. Rev. Earth Planet. Sci. 26 (1998) 189–218]). The Sr, Nd and Pb isotopic composition of the same sample places it towards the center of the mantle tetrahedron of Hart et al. (S.R. Hart, E.H. Hauri, L.A. Oschmann, J.A. Whitehead [Science 256 (1992) 517–520]) — in exactly the region predicted for the common mantle endmember based on the convergence of a number of pseudo-linear arrays of ocean island basalts worldwide (E.H. Hauri, J.A. Whitehead, S.R. Hart [J. Geophys. Res. 99 (1994) 24275–24300]). This observation implies that Selardalur may represent the best estimate available to date of the He–Sr–Nd–Pb isotopic composition of the 5th mantle component common to many mantle plumes.