Hi Tim,

There are some bond-strength - type calculations, but these have been shown to be pretty inaccurate so I would avoid them.

You might look at Farquhar et al. (1993; EPSL). I can't find my copy this moment, but I remember data for apatite and oxides (ilmenite, I think) equilibrated at high-T. Ilmenite has a high closure temperature, so if there's not much else in the rock and you know ilmenite relative to anything else you can back out the fractionation factor. One of James' apatites - sample SP3-3 - has been used as an occasional internal lab standard for d18O of PO4, BTW.

More generally you might see if there are isotope data from other apatite-oxide (Kiruna-type) deposits that could be used analogously.

Best,

Matt

******************************************************************
Dr. Matthew J. Kohn, University Distinguished Professor
Department of Geosciences, Boise State University
1910 University Dr.; MS1535
Boise, ID 83725-1535
[log in to unmask]
http://earth.boisestate.edu/mattkohn/
phone: (208)-426-2757   fax: (208)-426-4061
******************************************************************

On Sep 17, 2013, at 10:00 PM, ISOGEOCHEM automatic digest system wrote:

> Date:    Tue, 17 Sep 2013 13:16:53 +0100
> From:    "Heaton, Timothy H.E." <[log in to unmask]>
> Subject: Apatite oxygen isotope fractionation at high temperature
> 
> Does anyone know of data for the apatite oxygen isotope fraction (apatite-H2O or apatite-mineral) at high (hydrothermal-magmatic) temperatures?
> 
> Tim H.E. Heaton
> NERC Isotope Geosciences Laboratory
> British Geological Survey
> Keyworth, Nottingham NG12 5GG, England
> (www.bgs.ac.uk/nigl/index.htm<http://www.bgs.ac.uk/nigl/index.htm>)
> Tel. +44(0)115 936 3401
> Email: [log in to unmask]<mailto:[log in to unmask]>