Dear Ihsan,

for the oxygen isotope fractionation between MnCO3 and water, there
is only one experimental study of Jim O'Neil from 1969 yet published.
Theroretically, Golyshev et al (1981) and Zheng (1997) have also
derived the temperature dependence.

A few years ago, I did some low-temperature experiments on the
formation of Ca-rhodochosites using precipitation and transformation
reactions, and observed that 18O is enriched in these carbonates when
compared to pure calcite, in agreement with theoretical predictions.
Also under hydrothermal conditions (100-150C), the 18O/16O
partitioning
during aragonite replacements matched the calculated values.

Ciao
Michael

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Dr Michael E. Boettcher
Department of Biogeochemistry
Max-Planck-Institute for Marine Microbiology
Celsiusstr.1
D-28359 Bremen, FRG
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