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首页> 外文期刊>Contributions to Mineralogy and Petrology >Reaction kinetics of dolomite rim growth
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Reaction kinetics of dolomite rim growth

机译：白云岩边缘生长的反应动力学

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Reaction rims of dolomite (CaMg[CO_3]_2) were produced by solid-state reactions at the contacts of oriented calcite (CaCO_3) and magnesite (MgCO_3) single crystals at 400 MPa pressure, 750-850 °C temperature, and 3-146 h annealing time to determine the reaction kinetics. The dolomite reaction rims show two different microstructural domains. Elongated palisades of dolomite grew perpendicular into the MgCO_3 interface with length ranging from about 6 to 41 μm. At the same time, a 5-71 um wide rim of equiaxed granular dolomite grew at the contact with CaCO_3. Platinum markers showed that the original interface is located at the boundary between the granular and palisade-forming dolomite. In addition to dolomite, a 12-80 urn thick magnesio-calcite layer formed between the dolomite reaction rims and the calcite single crystals. All reaction products show at least an axiotactic crystallographic relationship with respect to calcite reactant, while full topotaxy to calcite prevails within the granular dolomite and magnesio-calcite. Dolomite grains frequently exhibit growth twins characterized by a rotation of 180° around one of the [1120] equivalent axis. From mass balance considerations, it is inferred that the reaction rim of dolomite grew by counter diffusion of MgO and CaO. Assuming an Arrhenius-type temperature dependence, activation energies for diffusion
机译：通过定向方解石（CaCO_3）和菱镁矿（MgCO_3）单晶在400 MPa压力，750-850°C和3-146的接触下通过固相反应生成白云石（CaMg [CO_3] _2）的反应边缘h退火时间，以确定反应动力学。白云石反应边缘显示出两个不同的微观结构域。拉长的白云石栅栏垂直于MgCO_3界面生长，长度范围约为6至41μm。同时，与CaCO_3接触时，等轴粒状白云石的边缘宽为5-71微米。铂标记显示原始界面位于颗粒状和栅状白云岩之间的边界处。除白云石外，在白云石反应边缘和方解石单晶之间还形成了厚度为12-80微米的镁方解石层。所有反应产物相对于方解石反应物都显示出至少一个等规晶体学关系，而在颗粒状白云石和镁方解石中主要存在全方解石方解石。白云石晶粒经常表现出生长孪生，其特征是围绕[1120]等效轴之一旋转180°。从质量平衡的考虑，可以推断白云石的反应边缘是由于MgO和CaO的反向扩散而增长的。假设温度与阿伦尼乌斯有关，则扩散的活化能

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