Hydrogen isotopes in volcanic plumes : Tracers for remote temperature sensing of fumaroles
Hydrogen isotopes in volcanic plumes : Tracers for remote temperature sensing of fumaroles
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火山羽流中的氢同位素：用于喷气孔远程温度传感的示踪剂
DOI：
10.1016/j.gca.2011.05.023
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发表时间：
2011
影响因子：
5
通讯作者：
D.D.Komatsu
中科院分区：
文献类型：
--
作者：
Tsunogai;U.;K.Kamimura;S.Anzai;F.Nakagawa;D.D.Komatsu
在高温火山喷气孔 (>400°C) 中，分子氢 (H2) 的同位素组成与喷气孔 H2O 的同位素组成达到平衡。在这项研究中，我们使用喷气孔 H2 的氢同位素交换平衡作为火山喷气孔远程温度的示踪剂。在这次遥感中，我们从火山羽流中推导出了延胡索H2的氢同位素组成（δD值）。为了确定我们可以从火山羽流中估计喷气孔 H2 的 δD 值，我们估计了出口温度为 630°C (Tarumae)、203°C (Kuju) 和 107°C (E-san) 的三个喷气孔的值。为此，我们测量了每个火山羽流中 H2 的浓度和 δD 值，以及直接在每个喷气孔处测定的值。羽流总 H2 中喷气孔 H2 的平均和最大混合比分别为 97% 和 99%（在 Tarumae）、89% 和 96%（在 Kuju）以及 97% 和 99%（在 E-san）。我们发现 H2 δD 值的消耗与 H2 浓度的倒数之间存在线性关系。此外，每个富含H2成分的估计端元δD值（Tarumae中为-260±30‰ vs. VSMOW，Kuju中为-509±23‰，E-san中为-437±14‰）与每个喷气孔处观察到的值非常吻合（Tarumae中为-247.0±0.6‰，Kuju中为-527.7±10.1‰，以及-432.1±2.5‰ (E-san)。此外，计算出的喷气孔同位素温度与观测到的樽前和九重出口温度的误差在 20°C 以内。我们推断，喷气孔 H2 的 δD 值在火山羽流中被淬灭。这使我们能够远程估计喷气孔中的这些，从而远程估计喷气孔的出口温度，至少对于那些出口温度超过 400°C 的喷气孔。通过将该方法应用于无法直接测量喷气孔的中岳山（阿苏火山）1号火山口喷出的火山羽流，我们估计喷气孔H2的δD值为-172±16‰，出口温度为868±97°C。本研究开发的使用氢同位素的远程温度传感广泛适用于许多火山系统。
In high-temperature volcanic fumaroles (>400°C), the isotopic composition of molecular hydrogen (H2) reaches equilibrium with that of the fumarolic H2O. In this study, we used this hydrogen isotope exchange equilibrium of fumarolic H2as a tracer for the remote temperature at volcanic fumaroles. In this remote sensing, we deduced the hydrogen isotopic composition (δD value) of fumarolic H2from those in the volcanic plume. To ascertain that we can estimate the δD value of fumarolic H2from those in a volcanic plume, we estimated the values in three fumaroles with outlet temperatures of 630°C (Tarumae), 203°C (Kuju), and 107°C (E-san). For this we measured the concentration and δD value of H2in each volcanic plume, along with those determined directly at each fumarole. The average and maximum mixing ratios of fumarolic H2within a plume’s total H2were 97% and 99% (at Tarumae), 89% and 96% (at Kuju), and 97% and 99% (at E-san). We found a linear relationship between the depletion in the δD values of H2, with the reciprocal of H2concentration. Furthermore, the estimated end-member δD value for each H2-enriched component (−260±30‰ vs. VSMOW in Tarumae, −509±23‰ in Kuju, and −437±14‰ in E-san) coincided well with those observed at each fumarole (−247.0±0.6‰ in Tarumae, −527.7±10.1‰ in Kuju, and −432.1±2.5‰ in E-san). Moreover, the calculated isotopic temperatures at the fumaroles agreed to within 20°C with the observed outlet temperature at Tarumae and Kuju. We deduced that the δD value of the fumarolic H2was quenched within the volcanic plume. This enabled us to remotely estimate these in the fumarole, and thus the outlet temperature of fumaroles, at least for those having the outlet temperatures more than 400°C. By applying this methodology to the volcanic plume emitted from the Crater 1 of Mt. Naka-dake (the volcano Aso) where direct measurement on fumaroles was impractical, we estimated that the δD value of the fumarolic H2to be −172±16‰ and the outlet temperature to be 868±97°C. The remote temperature sensing using hydrogen isotopes developed in this study is widely applicable to many volcanic systems.