Pressure solution and hydrothermal recrystallization of carbonate sediments — An experimental study

The extent of calcite recrystallization was determined in pressure-solution and hydrothermal experiments which were conducted on deep-sea carbonates of low-Mg calcite, Iceland spar, and reagent-grade calcite powder. In the pressure-solution experiments, wet sediments were subjected to confining pressures of 500–1500 bars and pore pressures of 150–500 bars, at temperatures between 22° and 180°C, for 21–240 h. The hydrothermal experiments were performed in sealed teflon-coated bombs at 200°C, zero effective stress, in sulfate-free sea water, for two weeks. The hydrothermal system was solution-dominated. The extent of calcite recrystallization was determined by measuring the oxygen isotopic compositions of the pore fluids and solids before and after each experiment. Scanning Electron Microscope observations, porosity and specific surface-area measurements were performed. In fine-grained carbonate samples subjected to high effective stresses, the mechanism for recrystallization apparently involves both relief of strain energy at grain-to-grain contacts and decrease in surface free energy by decreasing the surface area, while in coarse-grained carbonates, relief of strain energy appears to be the most important control of recrystallization. In the hydrothermal experiments, however, decrease in surface free energy is the only driving force for recrystallization. Effective stress increased the rate of calcite recrystallization. In both pressure-solution and hydrothermal experiments, clay minerals retarded the reaction. The effects of diatomite and basaltic glass on the extent of calcite recrystallization was investigated only in the hydrothermal experiments. Both admixed non-carbonate materials retarded the reaction, diatomite being the most effective inhibitor. Surface chemical reactions seem to be responsible for the observed inhibitions of calcite recrystallization. Increases in the extent of calcite recrystallization with increasing ionic strength were observed in hydrothermal experiments in NaCl solutions of five different ionic strengths. © 1980, All rights reserved.

Duke Scholars

Author Paul A. Baker Earth and Climate Sciences