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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Extreme 3He/~4He ratios in northwest Iceland: constraining the common component in mantle plumes
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Extreme 3He/~4He ratios in northwest Iceland: constraining the common component in mantle plumes

机译：冰岛西北部的极端3He /〜4He比：限制地幔柱中的共同成分

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摘要

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 approx 37 R_A (R_A = air ~3He/~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.
机译：来自冰岛西北部Selardalur的第三纪晚期玄武岩中所含的橄榄石和斜辉石的隐晶石携带的氦同位素比率最高的挥发物尚未见任何地幔柱。在三个不同的样品上测得的〜3He /〜4He比值，并通过在真空中逐步粉碎而提取，始终下降约37 R_A（R_A =空气〜3He /〜4He）-大大高于先前报道的冰岛或Loihi Seamount的值（请参见KA Farley， E. Neroda [地球地球科学年鉴，科学26（1998）189-218]。同一样品的Sr，Nd和Pb同位素组成使其朝向Hart等人的地幔四面体中心。 （SR Hart，EH Hauri，LA Oschmann，JA Whitehead [Science 256（1992）517-520]）—正是基于许多洋岛玄武岩的伪线性阵列的收敛性，为普通地幔端部构件预测的区域。 （EH Hauri，JA Whitehead，SR Hart [J. Geophys。Res。99（1994）24275-24300]）。该观察结果表明，Selardalur可能代表了迄今为止对许多地幔柱普遍存在的第五地幔组分的He-Sr-Nd-Pb同位素组成的最佳估计。

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