Actually its a hot question and a debatible issue. I see some papers that show the posibility to have HIMU-OIB signatures in recicled material from pilled slab far behind the trench (Zou et al. 2008) so probably the point its that OIB signatures are "not only" the evidence of primitive reservoirs...I think

sorry for my English jeje

Hi Pablo. Sure it is. Well, a decade ago, Don Anderson questioned the very key parameter people use high 3He/4He. Not many really followed up! I tried to look at it with nitrogen isotopes. I think there is a contribution from recycled mater but how and where is not clear. Recently, Chris Ballentine's group found that there is sea water like noble gas signatures in OIBs....

It is very controversial topic. I suggest reading a book, which contains both pro- and contra views on that, plus discussion added to each chapter. You will enjoy by reading it. The book is a bestseller of GSA:

Foulger, G.R. & Jurdy, D.M. (Eds.) Plates, plumes, and planetary processes. Geological Society of America, Special Paper 430. (2007).

Hi All. Sorry I kind of vanished! Thanks Pablo and Alexei and all those who are following this for taking time to read this. (May be it was not an interesting question as I did not see much of response as anticipated!)

I have an observation to share that relates to this, though. I was traveling in a car through an industrial district in India where I noticed a channel from a chemical industry entering into a small pond! That formed a layer of “scum” on the surface of the pond water. What’s the science behind it? “Incompatibility” is obvious I guess. To me something is incompatible when it is “not accepted” in a system. The channel tries to dump in chemicals that are incompatible to pond water, well may be the pond water is already saturated with all those and “won’t accept” anymore (thanks God I don’t have to drink that water).

So I applied the same logic to mantle. Say we have a mantle that is continuously flushed out (well at least tries to) of “incompatible” elements. But the subduction is doing the opposite. “Oh well most of those recycled matter are expelled at the Island volcanism….” something I heard for quite some time while I was working on my doctoral thesis.

My goal was to “document” (love this word, now that I am learning photo journalism!) nitrogen isotopes in mantle by studying MORBs, OIBs, Mantle xenoliths and Diamonds from worldwide locations. I thank again Late Prof Devendra Lal for helping me out with a majority of samples. Well what I found was interesting: all of them had a nitrogen iso component “that is produced” by the process of subduction! I also found that this was apparently observed in noble gas results before me. But people explained that by “air contamination” – an easy excuse! So I called my results an answer to the “Origin of Air-like noble gases” in mantle samples. But Science was too apologetic to accept my idea based on 2 or 3 lines of comments from some reviewer who probably wrote it while he was going to bed on a Friday evening! And maybe it did not anticipate such idea from a graduate student with a supervisor whom no one knew in mantle studies! Anyway(s), if you’re interested to see my original work I managed to convince GRL to publish it (GRL 2000, please let me know If you cannot find it). Irony is that Science published a paper from P. Sarda who “documented” (wow I seem to be falling in love with this word!) results similar to mine based on a correlation of Ar and Pb isotopic data! And a few years after that Nature has published a series of articles from Ballentine’s group on a similar topic. Well that’s how science rolls! Have a great weekend everyone. I love to hear comments.

The answer is debatable but there are many papers about isotopic relations in OIB-HIMU and OIB-FOZO type of basalts (f.e. Niu et al., 2011; White, 2013). They discuss the random influence of recycled, previously subducted oceanic crust, which contains two magma sources: EMI and EM2. These components pretend to be common in the OIB mantle. However, the primitive, bulk composition of OIB mantle is still hard to distinguish.

Agree. There is a significant recycled component in it. Anyone interested in nitrogen and noble gas isotopes? I have a couple of papers on oceanic basalts related to this issue

Interesting papers about noble gases in OIB and chondrites (in my opinion):

- Graham et al., 2002: Noble Gases in Geochemistry and Cosmochemistry

- Wieler et al., 2006: Trapping and Modification Processes of Noble Gases

and Nitrogen in Meteorites and Their Parent Bodies

I'm interested of mantle geochemistry, if you know something about the papers of anomally mantle isotope composition, please answer:) best regards:)