Experimental quantification of vanadium partitioning between eclogitic minerals (garnet, clinopyroxene, rutile) and silicate melt as a function of temperature and oxygen fugacity
Experimental quantification of vanadium partitioning between eclogitic minerals (garnet, clinopyroxene, rutile) and silicate melt as a function of temperature and oxygen fugacity
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DOI：
10.1007/s00410-022-01888-8
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发表时间：
2022-01
影响因子：
3.5
通讯作者：
M. Holycross;E. Cottrell
中科院分区：
文献类型：
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作者：
M. Holycross;E. Cottrell
钒是一种多价元素，可以在硅酸盐和氧化物相中形成V2+、V3+、V4+和V5+。V在行星材料中的相对丰度可以用作氧逸度（fO 2）的代理时，其分配行为已被校准与控制实验室实验。本文介绍了在800 ~ 1230 °C、1.8 ~ 2 GPa的温度下，在10个对数单位范围内进行的20个活塞-圆筒实验的结果，以量化在俯冲带榴辉岩熔融相关条件下V在石榴石、单斜辉石、金红石和含水硅酸盐熔体之间的分配。在所有的实验中，V在相之间的分配几乎相等地由fO 2和温度（和/或与温度直接相关的成分效应）控制。在实验金红石中，钒的相容性最好，其次是单斜辉石，最后是石榴石。在我们的实验系列中，计算的矿物/熔体分配系数对于所有三相均≥ 1。V在榴辉岩矿物中的高相容性导致在所研究的所有fO 2条件下榴辉岩熔融过程中V的传质可以忽略不计。钒的氧化态更易溶于金红石中，导致金红石/cpx和金红石/石榴石矿物间分配系数随fO 2的增加而线性增加。我们校准V之间的金红石-CPX和金红石-石榴石对天然岩石的ANFO 2代理和测试其应用程序的科伊杜金伯利岩套（塞拉利昂）榴辉岩捕虏体的分区。我们的应用程序产生spuriousfO 2值Koidu，表明自然系统的V系统学可能比我们的实验预测的要复杂得多。需要进一步的工作来表征的V之间的分区榴辉岩矿物的矿物固溶体，压力和温度的扩展范围之前，V-氧气压计可以应用于自然变质系统的信心。
Vanadium is a multivalent element that may speciate as V2+; V3+; V4+and V5+in silicate and oxide phases. The relative abundance of V in planetary materials can be used as a proxy for oxygen fugacity (fO2) when its partitioning behavior has been calibrated with controlled laboratory experiments. Here we present the results of 20 piston-cylinder experiments executed over a 10-log unit range offO2at temperatures from 800 to 1230 °C, at 1.8–2 GPa, to quantify the partitioning of V between garnet, clinopyroxene, rutile and hydrous silicate melt under conditions relevant to eclogite melting in subduction zones. In all experiments, the partitioning of V between phases is controlled nearly equally byfO2and by temperature (and/or compositional effects that are directly related to temperature). Vanadium is most compatible in experimental rutile, followed by clinopyroxene, then garnet. Calculated mineral/melt partition coefficients are ≥ 1 for all three phases in our experimental series. The high compatibility of V in eclogitic minerals results in negligible mass transfer of V during eclogite melting under allfO2conditions investigated. Oxidized species of V are more soluble in rutile compared to garnet and clinopyroxene, leading to a linear increase in rutile/cpx and rutile/garnet inter-mineral partition coefficients asfO2increases. We calibrate the partitioning of V among rutile-cpx and rutile-garnet pairs as anfO2proxy for natural rocks and test its application to eclogitic xenoliths from the Koidu kimberlite suite (Sierra Leone). Our application yields spuriousfO2values for Koidu, indicating the V systematics of natural systems are likely much more complex than predicted by our experiments. Further work is needed to characterize the partitioning of V between eclogitic minerals over an extended range of mineral solid solutions, pressures, and temperatures before a V-oxybarometer may be applied to natural metamorphic systems with confidence.