Date: Tue, 13 Sep 1994 19:11:49 -0400 (EDT)
Subject: Re: biotite analysis problem
From: Gregory H Symmes
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John-
Stormer et al 1993 (American Mineralogist, V. 78, p 641) found very large
variations in Cl and F X-ray intensity in apatite as a function of time and
crystal orientation. We were able to reproduce their results for F loss on our
apatite standard. The study calls into question all F and Cl analyses where
apatite is used as a standard. I guess it is possible similar behavior could
occur in F-phlogopite, but I would think it less likely due to mineral
structure. I have also used PbF2 as a F standard. Ultimately, I hope to get
some F-topaz as a F standard. We still use BAAP standard for Cl, but I would
rather not due to Stormer et al.'s work. We also have a scapolite from
Michigan which could be used for Cl, though I have never used it personally.
Good luck with the biotite analyses.
Cheers, Greg