Other
Scientific paper
May 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005e%26psl.233..391c&link_type=abstract
Earth and Planetary Science Letters, Volume 233, Issue 3-4, p. 391-409.
Other
3
Scientific paper
We report He isotope (3He/4He) variations in samples from alkali basaltic and basanitic lava flows from Grande Comore Island complemented by existing[1,2] [C. Class, S.L. Goldstein, Plume lithosphere interactions in the ocean basins: constraints from the source mineralogy. Earth Planet. Sci. Lett., 150 (1997) 245 260, C. Class, S.L. Goldstein, R. Altherr, P. Bachèchlery, The process of plume lithosphere interaction in the ocean basins—the case of Grande Comore. J. Petrol., 39 (5) (1998) 881 903] and new Sr Nd Pb isotope ratios and major and trace element abundances. He isotope data in samples from Tristan da Cunha and Gough islands and the Huri Hills in Kenya are reported also. Grande Comore 3He/4He ratios vary between 5.05 and 7.08 RA (4He/3He ≈ 141,000 101,000). Chemical and Sr Nd Pb isotopic variations of Grande Comore lavas were previously shown to reflect melts derived from the deep mantle plume and the shallow lithospheric mantle[1 3] [C. Class, S.L. Goldstein, Plume lithosphere interactions in the ocean basins: constraints from the source mineralogy. Earth Planet. Sci. Lett., 150 (1997) 245 260, C. Class, S.L. Goldstein, R. Altherr, P. Bachèchlery, The process of plume lithosphere interaction in the ocean basins-the case of Grande Comore. J. Petrol., 39 (5) (1998) 881 903, C. Claude-Ivanaj, B. Bourdon, C.J. Allègre, Ra Th Sr isotope systematics in Grande Comore Island: a case study of plume lithosphere interaction. Earth Planet. Sci. Lett. 164 (1998) 99 117]. The lithosphere-dominated end-member (La Grille volcano) shows uniform 3He/4He ratios within error of 6.75 7.08 RA (4He/3He ≈ 106,000 101,000) over a range of [He] = 36 428 × 10- 9 ccSTP/g. The plume end-member (of the Karthala volcano suite), as constrained by Sr, Nd, Pb isotope ratios, shows uniformly lower 3He/4He ratios with 5.05 5.41 RA (4He/3He ≈ 141,000 132,000) over a range of [He] = 11 136 × 10- 9 ccSTP/g. All samples show good correlations between Sr Nd He isotope ratios, indicating that the Grande Comore 3He/4He ratios are not significantly influenced by crustal contamination and reflect recent mixing between plume- and lithosphere-derived melts. The lithosphere beneath Grande Comore has retained its MORB-like helium isotopic composition, which suggests that the previously identified amphibole-forming metasomatism of the lithospheric mantle [1] [C. Class, S.L. Goldstein, Plume lithosphere interactions in the ocean basins: constraints from the source mineralogy. Earth Planet. Sci. Lett., 150 (1997) 245 260] occurred prior to the arrival of the Comoro plume. The well-constrained 3He/4He = 5.2 ± 0.2 RA (4He/3He ≈ 137,000 ± 5000) of the Comoro plume confirms the existence of “low 3He/4He” mantle plumes. A global compilation of OIB shows that OIB from “low 3He/4He” plumes form one “side” of the roughly triangular distribution of the global OIB data set in 143Nd/144Nd versus 206Pb/204Pb and 208Pb/204Pb, encompassing the lowest Nd to the highest Pb isotope ratios. It is also shown that “low 3He/4He” plumes are more enriched in Th and U relative to other plumes.
Class Cornelia
Goldstein Steven L.
Kurz Mark D.
Schlosser Peter
Stute Martin
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