Pages: 139 - 146
Abstract: Endowed with the theoretical knowledge of carbonate evaporation and the precipitation of CaMg carbonates from aqueous solutions the authors systematically researched the low temperature formation of dolomite-like carbonates. The results obtained at 40 °C indicate that the formation of rhombohedral CaMg carbonates depends on the solid matter/water ratio (solidus index Is). The higher the ratio, the more MgCO3 enters into the carbonate structure. The results also confirm a gradual transition of these relationships from calcite, through Mg-calcite, Ca-dolomite and Q-dolomite (Quasi-dolomite) to Mg-dolomite (Ca44Mg56). The structure of these synthesised carbonates is disordered, much like their natural counterparts in lagoons, sabkhas, soils etc. When studying Ca-dolomite in the laboratory it was found to restructure into stable dolomite at 100 °C and into calcite at 180 °C. Synthetized dolomite (Ca50Mg50) does not show superstructural X-ray reflections and hence it was denominated as a Quasi-dolomite (Q–D).
Keywords: hydrothermal alterations, synthesis, Q-dolomite, dolomite, Ca-dolomite, Mg-calciteDownload PDF document Show Text Version