Extreme He-3/He-4 ratios in northwest Iceland: constraining the common component in mantle plumes

Hilton, DR, Gronvold K, Macpherson CG, Castillo PR.  1999.  Extreme He-3/He-4 ratios in northwest Iceland: constraining the common component in mantle plumes. Earth and Planetary Science Letters. 173:53-60.

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evolution, geochemistry, Geodynamics, greenland, helium, helium isotope evidence, hot spots, hotspot, Iceland, isotopes, lavas, lead, loihi seamount, mantle, oceanic basalts, radioactive, systematics


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. He-3/He-4 ratios measured on three different samples and extracted by stepped crushing in vacuo fall consistently similar to 37 R-A (R-A = air He-3/He-4) - 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 Ph 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. (C) 1999 Elsevier Science B.V. All rights reserved.