The theory of zoning patterns in magmatic minerals using olivine as an example
The theory of zoning patterns in magmatic minerals using olivine as an example
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以橄榄石为例的岩浆矿物分带格局理论
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发表时间：
1987
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影响因子：
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通讯作者：
T. H. Pearce
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文献类型：
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作者：
T. H. Pearce
以橄榄石为例，提出了岩浆岩矿物简单分带生长理论。FeO-MgO绝对空间中的生长规律为(Y0-Ys) = A*(X0-Xs)k*，其中X表示FeO， Y表示MgO，下标s表示固相。X0和Y0是液体中的起始量，A是表征每个液体下降线的常数，k是分布系数。对该方程的考虑表明，局部系统的大小是影响分区格局形状的最重要参数。MgO/FeO的起始比是次重要的岩浆参数，而k是约束最严格的，因此是影响分带模式的最不重要的参数。绘制晶体中MgO/FeO与晶体体积之间的经验关系，使分带模式线性化，从而可以预测晶体的实际体积和晶体生长的体系直径。模型计算表明，在确定系统的线性尺寸时误差为7%或更小。在线性化的图上，晶体的起始组成可以通过外推法确定，即使截面不经过中心。利用这一生长理论规律对分带曲线进行分析，可用于研究晶体生长速率、成核机制、扩散速率和天然熔体的粘度。
A theory of simple zoned growth in magmatic minerals is developed using olivine as an example. The law of growth in absolute FeO-MgO space has the form (Y0-Ys) = A*(X0-Xs)k* where X refers to FeO, Y refers to MgO and the subscript s refers to the solid phase. X0 and Y0 are the starting amounts in the liquid, A is a constant which characterizes each individual liquid line of descent and k is the distribution coefficient. Consideration of this equation shows that the size of the local system is the most important parameter affecting the shape of the zoning pattern. The starting ratio MgO/FeO is the next most important magmatic parameter and k is the most tightly constrained and, therefore, the least important parameter affecting the pattern of zoning. An empirical relationship plotting MgO/FeO in the crystal versus the volume of the crystal linearizes the zoning pattern, allowing prediction of the fictive volume of the crystal and the diameter of the system from which the crystal grew. Model calculations show an error of 7% or less in determining the linear dimensions of the system. On a linearized plot the starting composition of the crystal may be determined by extrapolation, even if the section does not go through the center. Analysis of zoning profiles using this theoretical law of growth may be useful in studies of crystal growth rates, nucleation mechanisms, diffusion rates, and viscosity of natural melts.