Re: What causes the Hawaiian Hot Spot and why is it located where it is?

Well, I poked around a little bit, too, and I was not much more successful 
than you were.  I did try a few search strategies that you might not 
have.  One of the leading figures in mantle plume research is Norm Sleep 
of Stanford University.  His web site reveals the following two papers 
that could be interesting, although I do not know how much information 
they contain about the source.

Sleep, N.H.. 1992, Hotspot volcanism and mantle plumes. Annu. Rev., Earth 
Planet. Sci., v. 20, pp. 19-43.

Sleep, N.H.,1992, Time dependence of mantle plumes: some simple theory. J. 
Geophys. Res., v. 97, pp. 20007-20019.

One paper I found by searching "mantle plume" is the following paper that 
suggests that a large number of "hotspots" from Sleep's original list may 
in fact be near-surface features.  Apparently, some researchers are now 
questioning the existence of plumes at all.  This paper does not go that 
far, however.  The references in this paper might be quite helpful in 
finding more information.  
 http://wellspring.ess.sunysb.edu/html/seminar/elusive_mantle_plume.pdf

Another paper, recently published by Michael Manga and Don DePaolo at 
Berkeley and Lawrence Berkeley Labs highlights the evidence in support of 
deep origins of mantle plumes:
 http://www.lbl.gov/Science-Articles/Archive/assets/images/2003/May-08-2003/Deep_Origin.pdf


One idea I have heard is that plumes originate from slabs of ophiolitic 
oceanic lithosphere, possibly from the core-mantle boundary.  I found one 
citation to an "eclogite block" as a source in the Hawaiian plume:
 http://bullard.esc.cam.ac.uk/~seminar/abstract/takahashi.htm

Another paper at a site on the Bismarck Sea provides evidence of a 
lithosperic component to the plume source
 http://www.dur.ac.uk/colin.macpherson/bismarck/bismarck.html

The key data seem to be isotopic compositions of magmas, indicating an 
altered lithospheric source, combined with helium-3 abundances that 
indicate a mantle plume.  The following abstract seems to indicate an 
altered (or metamorphosed?) lithospheric component in some Iceland magmas, 
but it's not clear from the abstract what significance the authors attach 
to that finding.  
 http://www.cosis.net/abstracts/EAE03/07509/EAE03-J-07509.pdf

Further complicating the picture is the difficulty of determining what 
magmas at the surface come from a plume in the first place.  See:
 http://www.ingv.it/~roma/cultura/convegni/antec/ANTEC_abstracts/Panter.doc


I think the bottom line for your student is that this is an area of 
significant uncertainty and very active research.  Although there does 
seem to be general acceptance of a model in which plumes of mantle, 
including magmatic components from old subducted slabs, rise from near the 
core-mantle boundary, the evidence for such a model is not as robust as 
you might wish and there are some very competent geophysicists who are 
skeptical of the model.

Hope this helps,
David