Movement of inner fluids in calcite crystallites at standard conditions

摘要

Calcite is the most abundant carbonate mineral in the lithosphere and plays a major role in CO2 balance as a geological controller of this greenhouse gas and on contaminant uptake in the environment. Here,we report evidence of migration of CO2 from fluid inclusions hosted within a calcite crystal to the surface,with subsequent renewal of the calcite surface. Spontaneous nucleation and growth of nanometre-scale hillocks,without evidence of dissolution pits, is provided by Atomic Force Microscopy observations of a freshly cleaved calcite surface. The rate of fluid transport is estimated at 5 × 10-10±0.5 m.s-1, which is about 10 orders of magnitude greater than elemental diffusion within a solid lattice under standard conditions. Surface sites of natural calcite are most likely constantly renewed by the fluid mobility that we have documented here and, as a consequence, calcite's uptake capacity for contaminants in environmental systems is probably significantly higher than predicted by current models.