Experimental determination of trace element partition coefficients between spinel and silicate melt: the influence of chemical composition and oxygen fugacity
Experimental determination of trace element partition coefficients between spinel and silicate melt: the influence of chemical composition and oxygen fugacity
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DOI：
10.1007/s00410-015-1128-5
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发表时间：
2015-04
影响因子：
3.5
通讯作者：
C. H. Wijbrans;S. Klemme;J. Berndt;C. Vollmer
中科院分区：
文献类型：
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作者：
C. H. Wijbrans;S. Klemme;J. Berndt;C. Vollmer
我们提出了新的实验测定的微量元素之间的尖晶石和硅酸盐熔体分配系数。实验在大气压和1220至1450 °C的温度下进行。为了研究氧化还原条件对微量元素分配的影响，我们在不同的氧化还原条件下进行了实验，fO2范围从log −12到log −0.7。不同的尖晶石组合物的效果也进行了研究。结果表明，各种成分的尖晶石都容易与过渡金属Ni、Co和Ga相结合，相应的分配系数均大于1。改变熔体成分、晶体成分和氧化还原条件对Ni、Co、Ga的影响不大。然而，多价微量元素V和Mo表现出强烈的氧化还原条件对其分配行为的影响，DV和DMo在非常还原的条件下最高，在氧化性更强的条件下相当低。高场强元素Ti、Zr、Hf、Nb和Ta以及元素Sc和Lu的分配系数强烈地依赖于晶体组成，对于非常富Fe 3+或Cr（和贫Al）的尖晶石，DTi和DSc>1，但是在富Al尖晶石的系统中低一到两个数量级。我们提出了一些例子，我们的数据可以用来重建尖晶石形成的氧化还原条件。本文还对Pt和Rh在尖晶石和熔体之间的分配进行了研究，发现DRh强烈地依赖于氧化还原条件，而DPt则没有明显的影响。
We present new experimentally determined trace element partition coefficients between spinel and silicate melt. The experiments were performed at atmospheric pressure and at temperatures between 1220 and 1450 °C. To study the effect of redox conditions on trace element partitioning, we performed experiments under different redox conditions, withfO2ranging from log −12 to log −0.7. The effect of different spinel compositions is also investigated. Our results show that spinel of all compositions readily incorporates the transition metals Ni, Co and Ga and the corresponding partition coefficients are >1.DNi,Co,Gaare not significantly affected by changing melt composition, crystal composition or redox conditions. However, the multivalent trace elements V and Mo show a strong effect of redox conditions on their partitioning behavior withDVandDMohighest at very reducing conditions and considerably lower at more oxidizing conditions. Partition coefficients for the high field strength elements Ti, Zr, Hf, Nb, and Ta and the elements Sc and Lu strongly depend on crystal composition, withDTiandDSc>1 for very Fe3+- or Cr-rich (and Al-poor) spinels, but one to two orders of magnitude lower in systems with Al-rich spinels. We present some examples on how our data may be used to reconstruct redox conditions of spinel formation. We also present some results on the partitioning of Pt and Rh between spinel and melt.DRhdepends strongly on redox conditions, whileDPtis not significantly affected.