Magma-water interaction can dramatically influence the explosivity of volcanic eruptions. However, syn- and post-eruptive diffusion of external (non-magmatic) water into volcanic glass remains poorly constrained and may bias interpretation of water in juvenile products. Hydrogen isotopes in ash from the 2009 eruption of Redoubt Volcano, Alaska, record syn-eruptive hydration by vaporized glacial meltwater. Both ash aggregation and hydration occurred in the wettest regions of the plume, which resulted in the removal and deposition of the most hydrated ash in proximal areas <50 km from the vent. Diffusion models show that the high temperatures of pyroclast-water interactions (>400°C) are more important than the cooling rate in facilitating hydration. These observations suggest that syn-eruptive glass hydration occurred where meltwater was entrained at high temperature, in the plume margins near the vent. Ash in the drier plume interior remained insulated from entrained meltwater until it cooled sufficiently to avoid significant hydration.

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火山灰的同步喷发水合作用记录了爆炸性喷发中的火山碎屑-水相互作用

岩浆-水相互作用可以显着影响火山喷发的爆炸性。然而，外部（非岩浆）水向火山玻璃的同步和喷发后扩散仍然受到很大限制，并且可能会影响对幼年产品中水的解释。2009 年阿拉斯加堡垒火山喷发的火山灰中的氢同位素记录了蒸发的冰川融水产生的协同喷发水合作用。灰烬聚集和水化都发生在羽流的最潮湿区域，这导致在距喷口 <50 公里的近端区域中水化程度最高的灰烬的去除和沉积。扩散模型表明，在促进水合作用方面，火山碎屑-水相互作用的高温 (>400°C) 比冷却速度更重要。这些观察结果表明，在熔水在高温下夹带在喷口附近的羽流边缘时，发生了协同喷发的玻璃水化作用。干燥羽流内部的灰烬与夹带的融水保持绝缘，直到它充分冷却以避免显着水合作用。