Open AccessNitrogen isotopic composition of the MORB mantle: A reevaluation
Author(s) -
Mohapatra Ratan K.,
Murty S. V. S.
Publication year - 2004
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2003gc000612
Subject(s) - mantle (geology) , geology , basalt , hotspot (geology) , geochemistry , isotopic signature , mantle wedge , subduction , nitrogen , isotope , geophysics , seismology , chemistry , physics , quantum mechanics , tectonics , organic chemistry
Nitrogen in the mantle source of mid oceanic ridge basalts (MORBs) is commonly believed to have δ 15 N∼−5‰. This is based on a (selective) statistical average drawn from nitrogen isotopic data obtained simultaneously with argon from MORBs. However, on critical evaluation, using the accompanying 40 Ar/ 36 Ar data, we show this approach to be somewhat ambiguous. Considering the fact that MORBs can have a number of geochemical components in them, as has been shown by several recent studies, the approach of statistical averaging may actually point to a mixture rather than the true mantle end‐member. A more reasonable approach, also used for deriving the mantle noble gas signatures, suggests nitrogen in the MORB mantle to be much lighter (∼−15‰) in its isotopic composition. Such a signature is consistent with nitrogen data from MORBs as well as from other mantle derived samples that are believed to have sampled volatiles from the MORB mantle.