Carbonates reactivity in temperature and interactions with Fe- minerals

International audienceThe carbonate system is the one of most reactive in the mineralogical assemblages of clay-rocks. Consequently, pristine clay-rocks pore water compositions are expected to be at equilibrium with carbonate minerals. However, it is difficult to fully reconcile the concentration data obtained from seepage water sampled in equipped in situ boreholeswith the equilibrium concentrations obtained from pore water modeling (Pearson et al., 2011). It is especially true for dolomite whose solubility spans a large range of values in thermodynamic database as a function of crystallinity considerations, and for siderite/ankerite or other Fe-bearing carbonates whose compositions influence their solubility. The understanding of the carbonate system in clay-rock is necessary for a number of predictions including the effect of an increase of temperature on the pore water chemistry. In this respect, experiments were conducted to study the kinetics of equilibration of carbonate mineral assemblages as a function of temperature (25-80°C) in chemical conditions otherwise similar to those encountered in the Callovian-Oxfordian clay-rock