Abstract The diffusion of hydrogen in natural hydrothermal quartz crystals was studied between 657–956 °C at atmospheric pressure and various oxygen fugacity ( f O 2 ) conditions. Single crystals of OH-bearing quartz were dehydrated in the presence of Li or Na-enriched powders to induce Li-H or Na-H exchange, with the resulting diffusion profiles measured by both Fourier transform infrared (FTIR) spectroscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Diffusion parallel to [0001], i.e. the crystallographic c-axis, is described by: log 10 ⁡ D ( m 2 s − 1 ) = − 6.5 ± 0.3 + − 100.4 ± 5.2 kJ mol − 1 2.303 RT where log10D is the base 10 logarithm of the diffusion coefficient, R is the gas constant and T is the temperature in kelvins, and uncertainties are 1 σ. Diffusion is not affected by ( f O 2 ) in this system. Diffusion perpendicular to [0001] is consistently slower, but quantitative constraints cannot be obtained from our data given experimental limitations. This diffusivity is primarily associated with H+-Li+ (or H+-Na+, Na+-Li+) exchange, where the H+ and Li+ are charge-balanced by tetrahedrally-coordinated Al3+. A faster mechanism may also exist where the monovalent cations are charge balanced by excess oxygen. The final defect population, as imaged by FTIR spectroscopy and LA-ICP-MS, likely results from a combination of diffusion and inter-site rearrangement of the monovalent cations. Regardless of such complexities, the determined Arrhenius relationship should be applicable for natural volcanic quartz crystals from the Bishop Tuff, California, wherein H+ is associated with Al3+, and H loss from quartz preceding and/or accompanying the eruption is charge-balanced by Li-gain, without Al movement. Li and H profiles from an example quartz crystal suggest that it experienced eruption/cooling timescales of just 16 minutes to 2.4 hours, showing the considerable promise of using frozen H diffusion profiles in quartz to extract timescales and thus elucidate the last moments of such explosive silicic eruptions.

中文翻译：

---

基于实验确定的 H-Li 和 H-Na 在石英中扩散的喷发计时器应用于 Bishop Tuff

摘要 在大气压和各种氧逸度 (f O 2 ) 条件下，研究了 657–956 °C 之间天然热液石英晶体中氢的扩散。含 OH 的石英单晶在 Li 或 Na 富集粉末的存在下脱水以诱导 Li-H 或 Na-H 交换，通过傅里叶变换红外 (FTIR) 光谱和激光烧蚀电感耦合测量得到的扩散曲线等离子体质谱 (LA-ICP-MS)。平行于 [0001] 的扩散，即晶体学 c 轴，描述为： log 10 ⁡ D ( m 2 s − 1 ) = − 6.5 ± 0.3 + − 100.4 ± 5.2 kJ mol − 1 2.303 RT 其中 log10D 是基础10 扩散系数的对数，R 是气体常数，T 是开尔文温度，不确定度为 1 σ。在该系统中，扩散不受 (f O 2 ) 的影响。垂直于 [0001] 的扩散始终较慢，但鉴于实验限制，无法从我们的数据中获得定量约束。这种扩散性主要与 H+-Li+（或 H+-Na+、Na+-Li+）交换有关，其中 H+ 和 Li+ 由四面体配位的 Al3+ 进行电荷平衡。也可能存在更快的机制，其中单价阳离子通过过量氧进行电荷平衡。通过 FTIR 光谱和 LA-ICP-MS 成像的最终缺陷群可能是由单价阳离子的扩散和位点间重排的组合产生的。不管这些复杂性如何，确定的 Arrhenius 关系应该适用于来自加利福尼亚州主教凝灰岩的天然火山石英晶体，其中 H+ 与 Al3+ 相关联，火山喷发之前和/或伴随着石英的 H 损失由 Li-gain 电荷平衡，没有 Al 移动。来自示例石英晶体的 Li 和 H 剖面表明它经历了仅 16 分钟到 2.4 小时的喷发/冷却时间尺度，显示了使用石英中冻结的 H 扩散剖面来提取时间尺度并因此阐明这种爆炸性硅酸盐的最后时刻的巨大前景喷发。