Dear All,
based on Mossbauer on mineral separates, our recent experience (CMP
149, 129-140, 2005) is that in graphitic rocks Fe3+ is reduced during
biotite melting, with Fe3+/Fetot values of 9-16 in Bt, 0-1% in Grt,
Crd and Ilm.
We have used xenoliths, which may not necessarily be related to each
other in terms of primary lithology and chemical system.
However, old works (cited in the same paper) on granulites from the
Ivrea and the Adirondacks seem to support this idea of prograde Fe3+
reduction.
Thus, another thing to consider is where the Fe3+ may go.
It seems that while Bt is the primary Fe3+ carrier, even in graphitic
rocks, cordierite, garnet or ilmenite tend to become Fe3+-free.
Regards,
bernardo
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Bernardo Cesare
Dipartimento di Mineralogia e Petrologia, Universita' di Padova
Corso Garibaldi, 37, I-35137 PADOVA ITALY
Tel: ++39-049-8272019 Fax: ++39-049-8272010
email: [log in to unmask]
web site: http://www.dmp.unipd.it/bernardo/bernardo.html
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