广西自然科学基金(2021GXNSFAA220126); 国家自然科学基金(41962010, 42030502, 42090041)
High-temperature (above 150℃) dolomite synthesis experiment is considered to be an effective way to understand the genesis of natural dolomites. Under the consideration of the Mg/Ca value (molar concentration ratio) index that has an important impact on the genesis of natural dolomites, our experiment used two kinds of aragonitic bioclasts (Acropora, Ficus) as the precursor reactants in the 220℃ conditions to study the dolomitization process under different Mg/Ca concentration ratios (0.5, 0.7, 1.0, 1.2, 1.5) and reaction times (0.5, 1.0, 1.5, 2, 3, 6, 8, 14 h) respectively. The results show that the dolomitization process under high temperature can be divided into induction stage, rapid reaction stage and stable stage. This reaction process was not obviously affected by the precursor aragonite reactants, implying that the Mg/Ca concentration should have an obvious influence on the dolomitized products. With the increase of Mg/Ca ratio in the reaction solution, the induction period of dolomitization was shortened and the rate of dolomitization was accelerated, and the mole fraction of CaCO3 in the product dolomile was reduced and the order degree was increased, which indicates that high Mg2+ concentration can rapidly promote the replacement of Ca2+ by Mg2+ in aragonite lattice and complete the ordering process of the dolomites. This results provide basic theoretical support for explaining the influence of Mg/Ca mole concentration on natural dolomitization process.