Hi Clemente,

regarding huntite a kinetic phosphoric acid fractionation factor between
dolomite and magnesite seems to be appropriate. Calcite and aragonite
might probably be possible to separate from the huntite /dolomite at low
reaction temperatures due to faster reaction rates. Huntite /dolomite
compositions should be possible to relate to liberated Ca/Mg
stochiometries (stop reaction after different times and analyse both: C+O
isotopes in the gas phase and Ca+Mg in the phosphoric acid leachate.

Good luck, Michael

*****************************************************
Michael E. Böttcher
Marine Geochemistry, IOW
Warnemünde, Germany
[log in to unmask]
*****************************************************

> Dear Colleagues,
>
> We have been asked to analyze C and O isotopes in
> a carbonate called Huntite, CaCO3.3MgCO3.
>
> A literature search has returned few references
> to the mineral, and none regarding its stable
> isotope systematics.
>
> Will any of you have any experience on it, and
> can advice on recommended fractionation factors,
> even if approximate? Any suggestion for a "close
> relative" than can be used as an analogy
> (regarding stable isotopes)?
>
> To complicate even more the situation, some
> samples are mixtures with dolomite, aragonite
> and/or calcite. Any clue regarding relative
> reaction rates to attempt fractional extractions?
>
> Directions to literature sources would be excellent!
>
> Cheers,
>
> Clemente
>
>
>
>
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