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首页> 外文期刊>Geochimica et Cosmochimica Acta: Journal of the Geochemical Society and the Meteoritical Society >Vanadium K edge XANES of synthetic and natural basaltic glasses and application to microscale oxygen barometry
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Vanadium K edge XANES of synthetic and natural basaltic glasses and application to microscale oxygen barometry

机译：合成和天然玄武玻璃的钒K边缘XANES及其在微量氧气气压测定中的应用

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摘要

A new microscale oxybarometer for solar system basaltic glasses, based on vanadium K-edge X-ray absorption near edge structure (XANES) spectroscopy, is described. Vanadium is unique among abundant elements in siliceous materials in that it can potentially occur in nature in four valence states: V2+, V3+, V4+ and V5+. Consequently, the vanadium redox system is a robust oxybarometer covering at least six orders of magnitude in buffer-relative oxygen fugacity. The method was calibrated using synthetic glass standards produced under known fO(2) and temperature conditions. Correction for temperature differences among standards and unknowns was quantified using microXANES data for isobaric synthetic glass couples. Application of the method to lunar, martian, and terrestrial glasses yielded fO(2) estimates from 1.6 log units more reduced than the iron-wustite (IW) buffer (IW-1.6) for lunar glasses, to IW + 4.0 for terrestrial glass inclusions. The martian and terrestrial results are in good agreement with previous estimates by other methods. The inferred fO(2) values for lunar pyroclastic glasses are similar to 0.5 log unit more reduced than previous estimates, but the differences are comparable to analytical uncertainties. Micro-extended X-ray absorption fine structure spectra were consistent with the valence states determined by microXANES and provided additional constraints on vanadium site geometry. These results demonstrate the value of this new oxybarometer, which can be applied nondestructively to individual grains in conventional thin sections with similar to micrometer resolution and similar to 100 ppm elemental sensitivity. Copyright (c) 2005 Elsevier Ltd.
机译：描述了一种基于钒K边缘X射线吸收近边缘结构（XANES）光谱学的用于太阳能系统玄武岩玻璃的新型微型气压计。钒在硅质材料中的丰富元素中是独特的，因为它在自然界中可能以四种价态存在：V2 +，V3 +，V4 +和V5 +。因此，钒氧化还原系统是一种坚固的氧饱和度计，其相对于缓冲液的氧气逸度覆盖至少六个数量级。该方法是使用在已知的fO（2）和温度条件下生产的合成玻璃标准液校准的。使用microXANES数据对同量异位合成玻璃对的标准品和未知品之间的温差进行校正。该方法在月球，火星和陆地玻璃上的应用产生的fO（2）估计值比对月球眼镜的铁-铁（IW）缓冲液（IW-1.6）减少了1.6 log个单位，对于陆地玻璃夹杂物减少至IW + 4.0 。火星和陆地的结果与其他方法先前的估计非常吻合。推断的月球火山碎屑玻璃的fO（2）值比以前的估计值减少了0.5 log单位，但差异可与分析不确定性相比。微观扩展的X射线吸收精细结构光谱与由microXANES确定的化合价态一致，并为钒位点的几何形状提供了额外的限制。这些结果证明了这种新型的气压计的价值，该气压计可以无损地应用于传统薄片中的单个晶粒，其分辨率与微米分辨率相似，元素灵敏度与100 ppm相似。版权所有（c）2005 Elsevier Ltd.

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