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首页> 外文期刊>Contributions to Mineralogy and Petrology >Diffusion-controlled spherulite growth in obsidian inferred from H2O concentration profiles
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Diffusion-controlled spherulite growth in obsidian inferred from H2O concentration profiles

机译：H 2 O浓度曲线推断黑曜石扩散控制的球晶生长

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Spherulites are spherical clusters of radiating crystals that occur naturally in rhyolitic obsidian. The growth of spherulites requires diffusion and uptake of crystal forming components from the host rhyolite melt or glass, and rejection of non-crystal forming components from the crystallizing region. Water concentration profiles measured by synchrotron-source Fourier transform spectroscopy reveal that water is expelled into the surrounding matrix during spherulite growth, and that it diffuses outward ahead of the advancing crystalline front. We compare these profiles to models of water diffusion in rhyolite to estimate timescales for spherulite growth. Using a diffusion-controlled growth law, we find that spherulites can grow on the order of days to months at temperatures above the glass transition. The diffusion-controlled growth law also accounts for spherulite size distribution, spherulite growth below the glass transition, and why spherulitic glasses are not completely devitrified. Keywords Spherulites - Obsidian - FTIR - Advection–diffusion Communicated by J. Blundy.
机译：球晶是放射状晶体的球形簇，其自然存在于流纹黑曜石中。球晶的生长需要从主体流纹岩熔体或玻璃中扩散和吸收晶体形成成分，并排斥来自结晶区域的非晶体形成成分。用同步加速器-源傅里叶变换光谱法测量的水浓度分布图表明，在球晶生长过程中水被排入周围的基质中，并且在前进的晶体前沿之前向外扩散。我们将这些轮廓与流纹岩中水扩散模型进行比较，以估计球晶生长的时间尺度。使用扩散控制的生长定律，我们发现在高于玻璃化转变温度的温度下，球晶可以生长数天至数月。扩散控制的生长定律还解释了球晶尺寸分布，玻璃态转变以下的球晶生长，以及为什么球晶玻璃没有完全失透。关键字球晶-黑曜石-FTIR-对流扩散由J.Blundy传达。

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