EXPERIMENTALLY DETERMINED MINERAL-MELT PARTITION-COEFFICIENTS FOR SC, Y AND REE FOR OLIVINE, ORTHO-PYROXENE, PIGEONITE, MAGNETITE AND ILMENITE
EXPERIMENTALLY DETERMINED MINERAL-MELT PARTITION-COEFFICIENTS FOR SC, Y AND REE FOR OLIVINE, ORTHO-PYROXENE, PIGEONITE, MAGNETITE AND ILMENITE
复制标题
DOI：
10.1007/bf00344083
复制
发表时间：
1992-05-01
影响因子：
3.5
通讯作者：
NEWBERGER, F
中科院分区：
文献类型：
--
作者：
NIELSEN, RL;GALLAHAN, WE;NEWBERGER, F
我们目前对Sc、Y和REE（稀土元素）的分配行为缺乏了解，这可以直接归因于缺乏足够大或化学多样性的实验数据集。为了解决这个问题，我们进行了一系列的实验，使用几种不同的天然成分熔岩，掺杂感兴趣的元素，作为起始成分。微探针分析的斜方辉石，pigeonite，橄榄石，磁铁矿，钛铁矿和共存的玻璃中的实验费用被用来计算表达式，描述稀土分配作为一个函数的各种系统参数。使用表示矿物熔体反应（相对于元素比分布系数）的表达式，可以计算表示低钙辉石熔体分配行为的条款，并独立于辉石和熔体组合物。成分的变化表明，钪替代橄榄石涉及一个配对的替代与铝或更常见的是，与空位。Sc的分配取决于熔体组成和温度。实验测定的橄榄石熔体稀土元素分配系数与McKay（1986）的结果相似，但略高于McKay的结果，支持了他们的结论，即橄榄石的轻稀土元素强烈亏损。Y和稀土矿物/熔体分配系数的磁铁矿范围从0.003 La的0.02 Lu。钛铁矿分配系数范围从0.007 La的0.029 Lu。这些实验值是两个数量级低于许多发表的值确定的斑晶/矩阵分离技术。
Our current lack of understanding of the partitioning behavior of Sc, Y and the REE (rare-earth elements) can be attributed directly to the lack of a sufficiently large or chemically diverse experimental data set. To address this problem, we conducted a series of experiments using several different natural composition lavas, doped with the elements of interest, as starting compositions. Microprobe analyses of orthopyroxene, pigeonite, olivine, magnetite, ilmenite and co-existing glasses in the experimental charges were used to calculate expressions that describe REE partitioning as a function of a variety of system parameters. Using expressions that represent mineral-melt reactions (versus element ratio distribution coefficients) it is possible to calculate terms that express low-Ca pyroxene-melt partitioning behavior and are independent of both pyroxene and melt composition. Compositional variations suggest that Sc substitution in olivine involves either a paired substitution with Al or, more commonly, with vacancies. The partitioning of Sc is dependent both on melt composition and temperature. Our experimentally determined olivine-melt REE Ds (partition coefficients) are similar to, but slightly higher than those reported by McKay (1986) and support their conclusions that olivines are strongly LREE depleted. Y and REE mineral/melt partition coefficients for magnetite range from 0.003 for La to 0.02 for Lu. Ilmenite partition coefficients range from 0.007 for La to 0.029 for Lu. These experimental values are two orders of magnitude lower than many of the published values determined by phenocryst/matrix separation techniques.