Dear all,

I am wondering about these Quartz-Magnetite and Magnetite-Ilmenite
thermometers and getting a similar temperature by applying them -  the
following is coming to my mind:
Quartz, after it is formed, will close to O-isotopic exchange at a
different temperature then is the case for magnetite - ilmenite.
So, if thermometry is applied on the Quartz-Magnetite and the
Magnetite-Ilmenite systems, one should expect to get different
temperatures because of this different isotopic-exchange closing
temperature of the minerals? If a similar temperature is obtained then
at least one of these thermometers must give erroneous results. If
determined experimentally, the 'calibration' of the thermometer can be
wrong in this sense... If this reasoning is right, a lower temperature
is expected for the Quartz-Magnetite thermometer.
I like to see your comments. Maybe I am wrong in the idea of different
closing temperatures there - I just was citing from what I remember on
this and I have no time now to look it up (sorry for that).

Pier.
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Dr. P.A. de Groot
University of the Witwatersrand
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