Fluorine partitioning between eclogitic garnet, clinopyroxene, and melt at upper mantle conditions
Fluorine partitioning between eclogitic garnet, clinopyroxene, and melt at upper mantle conditions
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榴辉石榴石、单斜辉石之间的氟分配以及上地幔条件下的熔融
DOI：
10.1016/j.chemgeo.2016.05.032
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发表时间：
2016
期刊：
影响因子：
3.9
通讯作者：
Ireland
中科院分区：
文献类型：
--
作者：
Klemme;Grützner;Ireland
在这个实验研究中，我们获得了在地球上地幔条件下（4-6 GPa，1460-1550 °C）氟在双矿物含水榴辉岩中的矿物/熔体（DF= cmineral/cmelt）分配数据。绿辉石单斜辉石的矿物/熔体分配系数介于DF= 0.056 ± 0.005和DF= 0.074 ± 0.001之间。石榴石分配系数始终较低，平均分配系数为DF= 0.016 ± 0.003。我们发现，绿辉石单斜辉石是占主导地位的名义上无氟相俯冲洋壳，因此绿辉石预计是主要的氟载体在俯冲过程中的地壳到更深的地幔。再加上以前获得的分区数据，我们建议，洋壳可以托管更多的氟每质量单位比下面的亏损的海洋mantle.If大部分夹带的氟再循环到地球的过渡带，它是可能的，氟要么被纳入高压过渡带阶段或释放在高压相变和形成富氟的小程度的部分熔体。这两种情况都得到了洋岛玄武岩，金伯利岩和钾镁煌斑岩中氟浓度升高的支持。结合氟分配数据与水分配数据产生一个合理的过程，以产生一个高F/H2O比的钾镁煌斑岩岩浆。氟相对于H2O的富集是由多个小程度熔融事件引发的，该事件消耗残留的H2O比氟多，这是由H2O的矿物-熔体分配系数小大约三倍造成的。
In this experimental study we obtained new mineral/melt (DF= cmineral/cmelt) partitioning data for fluorine in a bimineralic hydrous eclogite under Earth's upper mantle conditions (4–6 GPa, 1460–1550 °C). Omphacitic clinopyroxene displays mineral/melt partition coefficients between DF= 0.056 ± 0.005 and DF= 0.074 ± 0.001. Garnet partition coefficients are consistently lower with an average partition coefficient of DF= 0.016 ± 0.003. We found that omphacitic clinopyroxene is the dominant nominally fluorine-free phase in subducted oceanic crust and hence omphacite is expected to be the major fluorine carrier during subduction of crust into the deeper mantle. Together with previously obtained partitioning data we propose that the oceanic crust can host more fluorine per mass unit than the underlying depleted oceanic mantle.If the majority of entrained fluorine is recycled into Earth's transition zone it is possible that the fluorine is either incorporated into high-pressure transition zone phases or released during high-pressure phase transformations and forming fluorine-rich small degree partial melts. Both scenarios are supported by elevated fluorine concentration in ocean island basalts, kimberlites, and lamproites.Combining the fluorine partitioning data with water partitioning data yields a plausible process to generate lamproitic magmas with a high F/H2O ratio. The enrichment of fluorine relative to H2O is triggered by multiple episodes of small degree melting that deplete the residual more in H2O than in fluorine, caused by the approximately three times smaller mineral-melt partition coefficients of H2O.
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DOI：
--
发表时间：
1995
期刊：
影响因子：
--
作者：
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DOI：
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发表时间：
1981
期刊：
影响因子：
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作者：
J. V. Smith;J. Delaney;R. Hervig;J. Dawson
通讯作者：
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影响因子：
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作者：
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R. Stalder;P. Ulmer
影响因子：
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