Noble gas and nitrogen isotopic components in Oceanic Island Basalts Journal Article uri icon

DCO ID 11121/4659-4285-5479-6581-CC

in language

  • eng

year of publication

  • 2009

abstract

  • We present helium, argon, xenon and nitrogen isotopic data from Oceanic Island Basalts (OIBs), obtained from stepped heating and vacuum crushing experiments. Signatures of (3)He/(4)He in the present samples, except for those from the Canary Islands, are significantly higher (up to 20xthe air ratio) than the MORB signature (8.5xair ratio). The argon ((40)Ar/(36)Ar) and xenon ((129)Xe/(132)Xe and (136)Xe/(132)Xe) isotopic data are consistent with a two-component mixture of gases from the mantle (either MORB or OIB source) and air contamination. In the stepwise heating data, delta(15)N varies from -20 parts per thousand to + 15 parts per thousand in the different heating steps. The vacuum crushing data show a narrower range (-5 parts per thousand to + 8 parts per thousand) of delta(15)N, which, except for one Reunion sample, is somewhat heavier than the totals from the stepped heating experiments.|Simultaneous argon and nitrogen isotopic systematics of the present data suggest contributions from mantle (somewhat different from MORB), recycled materials and air contamination. This is also consistent with the (36)Ar/(132)Xe elemental ratio. The present stepped heating data are consistent with a nitrogen isotopic component with delta(15)N similar to-25% in the OIB mantle. In line with the oxygen isotopic composition of the bulk Earth, this would be consistent with a contribution from enstatite chondrite-like volatiles to the planet's accretion. (C) 2009 Elsevier B.V. All rights reserved.

volume

  • 266

issue

  • 1-2