Re: icthyolith diagenesis

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Hello Clive
        Thanks for the reference.  I agree that the REE spectrum itself
fractionates (with respect to LREE-MREE-HREE).  What sort of bone are you
talking about.  I would think (although I don't know for sure) that in the
case of skeletal bones such as long bones (i.e. leg, arm etc) that due to
the complex make up of the various parts of bone that there would be
differential uptake.  I have not done a REE spectrum on the conodonts (it
was to expensive to do the number of samples I have) we have only done the
Sm and Nd ratios and isotopes.  I have read a few papers on the role of
PO4.  I suspect it depends on the form that PO4 is in (e.g. in solution or
not).  As for Ca, it appears that Nd and Sm are so close to the ionic radii
of Ca (they are slightly larger) that it replaces Ca in the lattice (much
like Sr).  Judith Wright describes a two substitution model based on
adsorption and diffusion.  Also have you read LeGeros (1981). Incorporation
into the biogenic material appears to be postmortem and hence it
equilibrates with seawater.

I'll reread the papers on PO4 and if I have any bright ideas I'll let you
know

Here are the refs for anyone interested:

Wright, J. 1990. Conodont geochemistry: A key to the Paleozoic. Courier
Forschungsinstitut Senckenberg, 118:277-305.

LeGeros, R. Z. 1981. Apatites in biological systems. Prog. Crystal Growth
Charact. 4:1-45
 

Great to hear from you again
Cindy


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Cindy Wright
School of Earth and Ocean Sciences
University of Victoria