Sara,
Also check out Guidotti (1984) in V. 13 of Rev. Mineral. It reviews
a lot of the metamorphic biotite data at that time. Therein is also a
discussion of how F infreases in Bt as a function of grade up into
granulite facies. If you are interested in ammonium in Bt, you might also
check the references in Guidotti and Sassi (1998), EJM.
C.V. Guidotti
Sarah,
Sorry if you have hear back on this already. You certainly can
[and probably '
should'] analyze F in biotite, especially in granulites [probably Cl as well].
On the microprobe we usually use a TAP crystal, but you might get higher
count r
ates on a light-el. crystal such as LDE1. The beam should be defocused,
and a g
ood idea also is to check for 'burn' effects [count-rate drop over time for F].
I would expect you probably can find abundant references to F and
biotite stabi
lity; one that comes to mind immediately is the MSA reviews Mica
volume[13], ch.
11 [munoz]. A georef or similar search likely will turn up some recent
article
s. I also recall some articles several years back on ammonium substitution, at
least one from Brittany(?) rather near you there [in AJS?].
Good luck.
>At 05:01 10/12/99 +0200, Sara Welley wrote:
>
>Hello Everyone,
>
> I noticed in some papers on granulites that the
>tables of chemical composition of biotite do not
>contain
>fluorine (F), is it because its
>not possible to analyse fluorine in biotite (?), if we
>can analyse it, could someone tell me how? I would
>appreciate if you could help me also with the relevant
>references on the effect of
>fluorine on biotite stability at high metamorphic
>grade?
>Many thanks in advance for your help.
>Sara
>
>=====
>
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