The hydrogen isotopic composition and water content of southern Pacific MORB: A reassessment of the D/H ratio of the depleted mantle reservoir

Type Article
Date 2013-11
Language English
Author(s) Clog Matthieu1, Aubaud Cyril1, Cartigny Pierre1, Dosso Laure2
Affiliation(s) 1 : Univ Paris 07, Inst Phys Globe, Lab Geochim Isotopes Stables, CNRS,UMR 7154,PRES Sorbonne Paris Cite, F-75005 Paris, France.
2 : IFREMER, CNRS, UMR 6538, F-29280 Plouzane, France.
Source Earth And Planetary Science Letters (0012-821X) (Elsevier Science Bv), 2013-11 , Vol. 381 , P. 156-165
DOI 10.1016/j.epsl.2013.08.043
WOS© Times Cited 51
Keyword(s) hydrogen isotopes, mantle geochemistry, mantle water
Abstract In this paper, we re-investigate the isotopic composition of hydrogen in MORB and the possible effects of contamination on delta D and water content. A suite of 40 N-MORB from the Pacific-Antarctic ridge, far from any hotspot, was analyzed for chlorine content by electron microprobe and for water content and delta D with silica tubes. Cl concentrations (from 29 to 2400 ppm) indicate widespread contamination, more intense with faster spreading rates, while water contents (from 840 to 7800 ppm) are mainly controlled by igneous processes. delta D values range from -76 to -48 parts per thousand, with an average value of -61 parts per thousand. The lack of correlation between Cl content and either H2O/Ce or SD indicate that contamination has a negligible effect on delta D for our samples, which is therefore characteristic of the mantle below the Pacific-Antarctic ridge. We suggest that the 20 parts per thousand lower delta D value reported for the North Pacific and North Atlantic is highly unlikely from geodynamical arguments. We propose that the convecting mantle is characterized by a delta D of -60+/-5 parts per thousand, as supported by the most recent data from North Atlantic N-MORB.
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