Dear Bassey Ephraim
differentiation of Fe3+ and Fe2+ in biotite from electron probe analyses
is VERY difficult (and unreliable, in my experience), even when additional
estimate of H is directly available from SIMS data.
If your research really requires good data for Fe3+ I would suggest that
you measure this parameter directly by Moessbauer (separating some tens of
mg of biotite from the granite should be relatively easy). We followed
this approach.

Sorry for not being of much help...

Regards,
Bernardo


>
> Dear Colleagues,I am working with microprobe data of biotite from granitic
> rocks. Unfortunately data on Fe2O3 and FeO are lumped together as FeO*
> (total Iron), thereby affecting my investigations. Does any of the
> community members know of a software (possibly, spreadsheet) that can
> assist in the differentiation of Fe3+ and Fe2+ in the structural formulae,
> using stoichiometry or any other somewhat reliable procedure. Kindly
> forward the software to me at [log in to unmask] or
> [log in to unmask] my in-dept appreciation in advance.Thanks
> Regards
> Dr. Bassey EphraimDepartment of GeologyUniversity of Calabar,
> CalabarNigeria


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Bernardo Cesare
Dipartimento di Geoscienze, Universita' di Padova
Via Gradenigo, 6, I-35122 PADOVA 	ITALY
Tel: ++39-049-8279148	Fax: ++39-049-8272010
email: [log in to unmask]
web site: http://147.162.117.1/~bernardo/bernardo/berning.html
MicROCKScopica web site: http://www.microckscopica.org
InsiemePerWamba web site: http://www.insiemeperwamba.org
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