Rob, 11/20/00
Very interesting questions. I'll be looking forward to what replies
you get.
I can't say I know any affects bearing on how the manganese
component of ilmenite affects garnet growth processes during prograde
regional metamorphism. However, in the W. Maine rocks we've found
systematic relations between grade and the Mn-content of coexiting Ilm and
Grt. We've also found the Mn content of Ilm and Grt increase as the extent
of sulfidation reactions become stronger. Eventually Grt drops out and then
Mn goes up abruptly in the Ilm. And when the sulfidation reactions become
even more intense so that Ilm drops out, leaving Rt as the Ti phase, the Mn
abruptly increases in phases that normally have lesser amount of Mn, e.g.
Phl, Chl, and especially Crd. We've looked for alabandite in such highly
sulfidized rocks but never found it (yet). It all seems to be a game of
crystal chemistry in terms of Mn going into its happiest home, and leaving
home when the house gets destroyed! Sounds quaint, but it really seems to
be the way it works.
But this still says nothing about your geothermometry question. I
hope hope to hear more on that soon.
Cheers, Charlie
*************************************************************************
>Dear Listmembers,
>Is anyone aware of any recent work (last 5 years) on the garnet-ilmenite
>geothermometer? I have Kress et al. (1985), Pownceby et al. (1987) and
>Pownceby et al. (1991), but haven't found any more recent ones.
>
>In particular I am looking for information concerning how the manganese
>component of ilmenite affects garnet growth processes during prograde
>regional metamorphism.
>Thanks in advance.
>Best regards,
>Rob Newman
>_____________________________________________
>Rob Newman
>Structure and Metamorphism Research Institute
>School of Earth Sciences
>James Cook University, Townsville
>Queensland 4811, Australia
>
>P: +61 747 816810
>F: +61 747 251501
>E: [log in to unmask]
>W: http://www.jcu.edu.au/~sci-rln
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