Grain growth kinetics in olivine aggregates
Grain growth kinetics in olivine aggregates
复制标题
DOI：
10.1016/0040-1951(89)90221-7
复制
发表时间：
1989-11
期刊：
影响因子：
2.9
通讯作者：
S. Karato
中科院分区：
文献类型：
--
作者：
S. Karato
研究了热压细晶粒橄榄石团聚体的晶粒生长动力学。实验条件包括0.1 MPa、300 MPa和1 GPa的压力，以及1473、1573和1673 K的温度，存在或不存在水。在晶粒生长的初始阶段，较大晶粒的生长迅速发生，消耗较小的晶粒，这导致显著的孔隙截留。在这个过程中，几乎均匀的粒度分布被建立。在此阶段之后，在大多数情况下，粒度分布几乎保持均匀。结果发现，当水的量是有限的，水的存在下，增强晶粒生长动力学。但当含水量较大时，含水孔隙对晶界迁移有明显的抑制作用。因此，由于水的存在，晶粒生长的增强是由于溶解水在橄榄石中的作用，而不是通过水的质量传输。在某些样品中发现了异常晶粒长大。在这些情况下，正常的晶粒生长受到抑制的存在下，大量的水填充的孔隙，或晶粒具有显着较大的尺寸比其余发生在起始材料。在0.1 MPa的运行，显着的孔隙开发和晶粒生长速率显着低于在高围压。这些结果表明，水和孔隙对橄榄石中的晶粒生长动力学有重要影响。当气孔（或第二相）对晶粒生长的抑制作用不重要时，橄榄石中晶粒的生长速率非常快：在1500 K下，晶粒在102 ~ 103小时内生长到100 μm尺寸。因此，橄榄石中的细粒度将仅在很短的地质时间内保持，除非晶界被次级粒子有效地钉扎。
Grain growth kinetics were studied in hot-pressed fine-grained olivine aggregates. Experimental conditions include pressures of 0.1 MPa, 300 MPa and 1 GPa, and temperatures of 1473, 1573 and 1673 K, with or without the presence of water. At the initial stage of grain growth, growth of larger grains occurs rapidly, consuming smaller grains, which results in significant pore entrapment. Almost homogeneous grain-size distribution is established in this process. After this stage, grain-size distribution remains almost homogeneous in most cases. It was found that the presence of water enhances the grain growth kinetics when the amount of water is limited. However, when the amount of water is large, the water-containing pores significantly inhibit the grain boundary migration. Therefore the enhancement of grain growth due to the presence of water is due to the role of dissolved water in olivine rather than the mass transport through water. Abnormal grain growth was found in some samples. In these cases, normal grain growth was inhibited by the presence of a significant amount of water-filled pores, or grains with significantly larger size than the rest occurred in the starting materials. In 0.1 MPa runs, significant porosity developed and the grain growth rates were significantly lower than in those at high confining pressures. These results show that both water and pores have important effects on grain growth kinetics in olivine. When the effects of pores (or secondary phases) in inhibiting grain growth are unimportant, the grain growth rate in olivine is very fast: growth to 100 μm size will occur in 102to 103hours at 1500 K. Thus fine grain size in olivine will be maintained only for a short geological time, unless the grain boundaries are effectively pinned by secondary particles.