Are there any refs where fluorescence of Cr is discussed? How good may ZAF
account for the fluorescence?
----- Original Message -----
From: Eric Essene <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, May 23, 2001 6:39 PM
Subject: Re: TiO2 in Grt
> We are very aware of the effect. We have documented the problem for
> in even an iron-poor host (pyrope, olivine) with chromite inclusions, and
> the effect can be shown to be important for 50-100 um at 15 kV (Cr is more
> strongly fluoresced by Fe than Ti).
> To Horst, Eric, and others
> >Anyone studying the solubility of TiO2 in garnet grains
> >containing small inclusions of a Ti-rich phase, such as
> >rutile or ilmenit exsolutions, needs to be aware of the
> >danger of spurious effects in electron microprobe analysis
> >of the host garnet. Apparent titanium contents of up to
> >1 weight-% TiO2 can result from secondary fluorescence
> >effects, in the vicinity of such inclusions, and the effect
> >is significant to a distance of 25-30 microns from the
> >nearest inclusion. The problem has been documented for
> >garnet by Feenstra & Engi (1998, notably in Fig.5 and
> >text p.385-6).
> >In essence, primary radiation generated by Fe and Mn in
> >garnet causes the excitation of Ti-fluorescence radiation
> >in nearby Ti-rich phases, even if no grain of the latter
> >phase is hit by the electron beam. In samples that contain
> >abundant such inclusions in garnet, it is virtually not
> >possible to correct for this effect or indeed to avoid it.
> >Ignoring this analytical artifact may produce unrealistically
> >high Ti-contents for garnet (and other Fe-rich silicates).
> >Best wishes,
> >Martin Engi
> >Feenstra A. & Engi M. (1998) An experimental study of Fe-Mn
> >exchange between garnet and ilmenite. Contributions to
> >Mineralogy and Petrology, vol. 131, p. 379-392.