Inorganic and organic influences on carbonate cementation

Abstract

Models of subaerial and beachrock carbonate cementation environments have been simulated successfully in the laboratory and have proven to be an important tool in understanding cementation processes in the field. Decreases in partial pressure of CO₂ in calcium bicarbonate solutions produce cements with various combinations of carbonate polymorphs. Chemical properties and complexing ability of different chemical species are of major importance. Fe, Mo, Ni, Zr, Cu, La and Co show different degrees of metastable carbonate formation. Some amino acids and fatty acids also show different degrees of metastable carbonate formation; organic coatings and complexing may be the driving forces for their formation. In experimental cementation samples, many different calcium carbonate crystals habits have been observed. Rhombohedral or blocky calcite cement, and aragonite needles and radiating aggregates are the most common cements observed. Cements usually grow from point of contacts of the sand grains and gradually fill the pore spaces.