Catalysis, inhibition, and the calcite-aragonite problem; [Part] 1, The aragonite-calcite transformation

Abstract

The kinetics of the aragonite-calcite transformation were studied in aqueous solution to determine the factors involved in the process of calcite crystallization and the controlling diagenetic conditions for the aragonite-calcite transformation. The reaction involved the solution and equilibration of aragonite with the solution and the subsequent nucleation and growth of calcite. The extent of reaction was determined by X-ray diffraction. Data suggest that calcite nucleation occurs on aragonite surface, whereas growth occurs on point or line defects. Catalysis by CO ₂ , CaCl ₂ , and inhibition by KOH indicate a fundamental reaction involving Ca (super ++) and HCO ₃ (super -) . Calcite crystallization is strongly inhibited by Mg (super ++) and less so by SO ₄ (super --) .