Crystal-melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene
Crystal-melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene
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DOI：
10.1016/j.gca.2006.11.010
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发表时间：
2007-02-15
影响因子：
5
通讯作者：
Wood, Bernard J.
中科院分区：
文献类型：
--
作者：
Heber, Veronika S.;Brooker, Richard A.;Wood, Bernard J.
通过紫外激光烧蚀（213 nm）在 0.1 GPa 混合稀有气体压力下从熔体生长的单个晶体，获得了橄榄石 (of) 和单斜辉石 (cpx) 的所有稀有气体的矿物熔体分配系数 (D-min/melt(i))。人们开发了实验技术来生长几乎不含熔体和流体夹杂物的晶体，因为在之前的工作中发现这两种夹杂物会引起严重的问题。对于分析相对于共存熔体和流体相具有非常低的分配系数的晶体中的稀有气体来说，这是一个特别重要的问题。 He、Ne、Ar、Kr 和 Xe 的 ol-熔体系统获得的优选分配值分别为 0.00017(13)、0.00007(7)、0.0011(6)、0.00026(16) 和 0.0006((-6))((+9))。各自的 cpx-熔体分配系数为 0.0002(2)、0.00041(35)、0.0011(7)、0.0002(2) 和 0.0002。数据证实了稀有气体对于橄榄石和单斜辉石的不相容行为，但与其他微量元素不同的是，这些值在较宽的原子半径范围内几乎没有变化。然而，分配对原子半径的依赖性的缺乏与其他痕量元素的分配行为一致，这些元素已被发现随着电荷减少而表现出逐渐降低的 D-min/melt(i) 对半径的依赖性。由于所有稀有气体似乎都表现出相似的 D-min/melt(i) 值，我们推断稀有气体在熔融和分级结晶过程中不会被橄榄石和单斜辉石显着地彼此分馏。尽管不相容，稀有气体的分配值也表明，尽管经历了强烈的熔融过程，但大量的原始稀有气体很可能保留在地幔中。我们的数据表明，玄武岩羽流源的高原始/放射成因稀有气体比率（He-3/He-4、Ne-22/Ne-21 和 Ar-36/Ar-40）特征可以通过回收先前熔化（耗尽）的地幔源来实现，而不是反映孤立的、未脱气的原始地幔区域。 (c) 2006 Elsevier Inc. 保留所有权利。
Mineral-melt partition coefficients of all noble gases (D-min/melt(i)) have been obtained for olivine (of) and clinopyroxene (cpx) by UV laser ablation (213 nm) of individual crystals grown from melts at 0.1 GPa mixed noble gas pressure. Experimental techniques were developed to grow crystals virtually free of melt and fluid inclusions since both have been found to cause profound problems in previous work. This is a particularly important issue for the analysis of noble gases in crystals that have very low partition coefficients relative to coexisting melt and fluid phases. The preferred partitioning values obtained for the ol-melt system for He, Ne, Ar, Kr, and Xe are 0.00017(13), 0.00007(7), 0.0011(6), 0.00026(16), and 0.0006((-6))((+9)), respectively. The respective cpx-melt partition coefficients are 0.0002(2), 0.00041(35), 0.0011(7), 0.0002(2), and 0.0002 The data confirm the incompatible behaviour of noble gases for both olivine and clinopyroxene but unlike other trace elements these values show little variation for a wide range of atomic radius. The lack of dependence of partitioning on atomic radius is, however, consistent with the partitioning behaviour of other trace elements which have been found to exhibit progressively lower dependence of D-min/melt(i) on radius as the charge decreases. As all noble gases appear to exhibit similar D-min/melt(i) values we deduce that noble gases are not significantly fractionated from each other by olivine and clinopyroxene during melting and fractional crystallisation. Although incompatible, the partitioning values for noble gases also suggest that significant amounts of primordial noble gases may well have been retained in the mantle despite intensive melting processes. The implication of our data is that high primordial/radiogenic noble gas ratios (He-3/He-4, Ne-22/Ne-21, and Ar-36/Ar-40) characteristic of plume basalt sources can be achieved by recycling a previously melted (depleted) mantle source rather than reflecting an isolated, non-degassed primordial mantle region. (c) 2006 Elsevier Inc. All rights reserved.