DiscussionReply to: “Recycled” volatiles in mantle derived diamonds—Evidence from nitrogen and noble gas isotopic data
Section snippets
On the subduction of rare gases
The evidence for the mixing model of Mohapatra and Honda [2] is presented in two figures (40Ar/36Ar vs. 129Xe/130Xe and 36Ar/130Xe and 84Kr/130Xe vs. 129Xe/130Xe) in which there is a “recycled/subducted” endmember lying on one side, with the other endmember, on the opposite side, being the mantle. Mohapatra and Honda thus agree with our main conclusion, namely that a “mantle component” [1] is present within our samples. The discussion centers on whether some subducted volatiles may or may not
On the fractionation of stable isotopes at mantle temperatures
It is generally accepted that peridotite-related diamonds form from mantle-related carbon [6], [7]. Only some eclogitic diamonds might form from subducted carbon and these would have odd isotopic values (e.g. sulfur, oxygen, carbon) (e.g. [6], [7]). In our study [1], the identification of similar mantle-like Xe-patterns within both polycrystalline peridotitic and eclogitic diamonds was taken as further support for derivation from the same source. In addition, both monocrystalline and
Conclusions
We thus question the arguments presented by Mohapatra and Honda [2] proposing that there is some obvious subducted component(s) in the rare gases found in polycrystalline diamonds. The chemical isotopic composition of rare gases in polycrystalline diamonds from Orapa can be best explained on the basis of mantle fluids and post-crystallization radiogenic/nucleogenic/fissiogenic ingrowths and diffusion out of the diamond. We believe that this is the simplest way to account for our observations
Acknowledgments
We are grateful to the anonymous reviewer for his comments which helped improving both clarity and tone of our reply.
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