Stefano,

You may find the information you need in: Carothers, Adami & Rosenbauer. 1988.
Experimental oxygen isotope fractionation between siderite-water and
phosphoric acid liberated CO2-siderite. Geochim. Cosmochim. Acta, v. 52, 2445-
2450.

Although it doen't mention anything about carbon isotope fractionation in the
title, it does in fact give experimental values of alpha for FeCO3-HCO3 at 33,
103, 150 and 197 oC.

Hope this is of some use,

Steve Crowley

Stable Isotope Laboratory
Dept. of Earth Sciences
University of Liverpool

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