Experimental Synthesis And Geological Significance Of Calcium Carbonate Under Different Additives

The paper studied the impacts of various organic and inorganic on carbonate crystals, the changes of sizes and morphologies and other properties during the crystal formation. Calcium carbonate was studied as the object of study. The calcium carbonate crystal with special morphologies was produced by biomimetic synthesis,and its structure and morphology were characterized.In agarose gel, carbohydrates, alcohol/water solution, amino acids,protein/water solution and inorganic Mg2+, calcium carbonate particles with different crystal type and morphology were produced by the liquid phase method. Calcium carbonate particles with spherical, dumbbell, needle bar and so on were produced by controlling the reaction conditions and the additive concentration.By comparing the carbonate minerals with special morphologies in geological environments with the synthetic calcium carbonates in laboratory, we found that:carbonate minerals with special morphology found in the natural geological environment and calcium carbonate crystals synthetised under the conditions of different additives were very similar in morphology and microstructure,but both were different in material composition, particle size and formation environment.The compared results indicate that the organic compounds of microbes may play an important role in the precipitation of carbonate minerals with special morphologies in natural environments. The formation of microspheric dolomite in middle Permian carbonate rocks may have close relationship to some gelatinous compounds or organic molecules rich in -OH,-COOH; The microparticles appeared on the crystal surfaces of calcite and gypsum in the oolitic limestone in lower Pleistocene Qigequan Formation probably belong to the crystal itself. They can be interpreted as the coarse crystal surface during crystal growth.By comparing the synthetic calcium carbonates induced by different additives in*laboratories with the carbonate minerals with special micromorphologies(e.g. microspheres and micro-rod shapes) found in modem sediments and ancient carbonate rocks, we explore and discuss the possible mechanisms of deposition of these carbonate minerals in geologic environments. The results of the research have some significance for the formation mechanism of carbonate minerals in the geological history..