对橄榄石相变形核率的估算  

Evaluation of the nucleation rate of olivine

作　　者：王曙光[1] 宁杰远[1] 叶国扬[1] 楼小挺[1] 刘平江[1] 

机构地区：[1]北京大学地球与空间科学学院计算地球动力学实验室,北京100871

出　　处：《地球物理学报》2007年第1期122-125,共4页Chinese Journal of Geophysics

基　　金：国家科技部(2004cb418406);国家自然科学基金(40521002)资助

摘　　要：地幔主要矿物橄榄石[(Mg0.89Fe0.11)2SiO4]的相变与深源地震的解释以及俯冲带和周围地幔的相互作用相关.其中,形核率和长大率是刻画其相变动力学的两个重要参数.因为实验技术的原因,目前人们还没有基于实验数据给出橄榄石的形核率.本文首先通过对挤碰物理图像的分析,对边界形核情形的相变动力学理论中表征挤碰程度的无量纲参数进行了修正.在此基础上,根据已有的实验资料,首次对橄榄石相变的形核率进行了估计.通过对形核率数据的拟合,可以得到形核率参数K0和γ1/3.得到两个形核率参数的变化范围分别为K0=5.5×1021-8.7×1027s-1.m-2.K-1,γ1/3=0-0.20 J.m-2,最佳拟合值为:K0=6.9×1024s-1.m-2.K-1,γ1/3=0.16 J.m-2.Phase transformation of （Mg0.89 Fe0.11 ）2SiO4 olivine, the proposed major composition of upper mantle, is related to the mechanism of deep focus earthquakes and the interaction between subduction zones and their ambient mantle. Nucleation rate and growth rate are two important parameters in the computation of phase transformation. However, the nucleation rate has not been derived from the experimental data partly for technical difficulties. We modify the dimensionless parameter describing the impingement under grain boundary nucleation through physical analysis on the image of the impingement. Based on this modification and the experimental data, we first evaluate the nucleation of olivine. By fitting the new nucleation rates, we get the parameters K0 and γФ^1/3. The best fitting results are K0 =6.9× 10^24 S^-1 ·m^-2·K^-1, γФ^1/3 =0.16 J·m^-2

关 键 词：亚稳态橄榄石 相变形核率 俯冲带 地幔间断面 

分 类 号：P574[天文地球—矿物学]