Vesiculation rates of obsidian domes inferred from H2O concentration profiles
Vesiculation rates of obsidian domes inferred from H2O concentration profiles
复制标题
从 H2O 浓度分布推断黑曜石圆顶的囊泡率
DOI：
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发表时间：
2005
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通讯作者：
Michael C. Martin
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文献类型：
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作者：
J. Castro;M. Manga;Michael C. Martin
流纹岩穹隆的爆炸性取决于气泡的成核和长大。为了了解这些过程，我们用同步加速器傅里叶变换红外(FTIR)光谱显微镜测量了层间黑铁矿-浮石样品中H2O的毫米尺度变化。所有样品的H2O含量都在1-atm的溶解度值(∼0.10wt.%)以上，并向气泡区呈系统性下降，表明气泡正在生长，熔体对常压的脱气是不完整的。为了限制泡化的时间尺度，将H2O剖面与水扩散模型进行了比较。扩散时间从0.4天到15天不等，代表气泡成核到熄灭之间的时间。我们使用这些结果来估计挥发性出溶的持续时间，并评估在黑岩圆顶表面经常发现的爆炸坑的形成时间，尽管从未见过。
Explosivity of rhyolite domes depends on bubble nucleation and growth. To understand these processes, we measure millimeter‐scale variations in H2O by synchrotron Fourier transform infrared (FTIR) spectromicroscopy on interlayered obsidian‐pumice samples. The H2O contents of all samples are above the 1‐atm solubility value (∼0.10 wt.%) and decrease systematically towards vesicular zones, indicating that gas bubbles were growing and that degassing of melt to atmospheric pressure was incomplete. H2O profiles are compared with models for water diffusion in order to constrain the temporal scale of vesiculation. Diffusion timescales range from 0.4 to 15 days, and represent the time between bubble nucleation and quenching. We use these results to estimate the duration of volatile exsolution and evaluate the timing of the formation of explosion pits frequently found on the surfaces of obsidian domes, though never witnessed.