The unexpected intersection of rhyolitic magma and retrieval of quenched glass particles at the Iceland Deep Drilling Project-1 geothermal well in 2009 at Krafla, Iceland, provide unprecedented opportunities to characterize the genesis, storage, and behavior of subsurface silicic magma. In this study, we analyzed the complete time series of glass particles retrieved after magma was intersected, in terms of distribution, chemistry, and vesicle textures.Detailed analysis of the particles revealed them to represent bimodal rhyolitic magma compositions and textures. Early-retrieved clear vesicular glass has higher SiO2, crystal, and vesicle contents than later-retrieved dense brown glass. The vesicle size and distribution of the brown glass also reveal several vesicle populations. The glass particles vary in δD from −120‰ to −80‰ and have dissolved water contents spanning 1.3−2 wt%, although the majority of glass particles exhibit a narrower range. Vesicular textures indicate that volatile overpressure release predominantly occurred prior to late-stage magma ascent, and we infer that vesiculation occurred in response to drilling-induced decompression. The textures and chemistry of the rhyolitic glasses are consistent with variable partial melting of host felsite. The drilling recovery sequence indicates that the clear magma (lower degree partial melt) overlays the brown magma (higher degree partial melt). The isotopes and water species support high temperature hydration of these partial melts by a mixed meteoric and magmatic composition fluid. The textural evidence for partial melting and lack of crystallization imply that magma production is ongoing, and the growing magma body thus has a high potential for geothermal energy extraction.In summary, transfer of heat and fluids into felsite triggered variable degrees of felsite partial melting and produced a hydrated rhyolite magma with chemical and textural heterogeneities that were then enhanced by drilling perturbations. Such partial melting could occur extensively in the crust above magma chambers, where complex intrusive systems can form and supply the heat and fluids required to re-melt the host rock. Our findings emphasize the need for higher resolution geophysical monitoring of restless calderas both for hazard assessment and geothermal prospecting. We also provide insight into how shallow silicic magma reacts to drilling, which could be key to future exploration of the use of magma bodies in geothermal energy.

中文翻译：

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冰岛克拉夫拉 IDDP-1 流纹岩熔体的结构和地球化学窗口及其对钻井的反应

2009 年在冰岛克拉夫拉的冰岛深钻项目 1 地热井中，流纹质岩浆与淬火玻璃颗粒的意外交叉，为表征地下硅质岩浆的成因、储存和行为提供了前所未有的机会。在这项研究中，我们分析了岩浆相交后回收的玻璃颗粒的完整时间序列，包括分布、化学和囊泡质地。颗粒的详细分析表明它们代表双峰流纹质岩浆成分和质地。早期回收的透明泡状玻璃比后期回收的致密棕色玻璃具有更高的 SiO2、晶体和囊泡含量。棕色玻璃的囊泡大小和分布也揭示了几个囊泡种群。玻璃颗粒的 δD 从 -120‰ 到 -80‰ 变化，溶解水含量为 1.3-2 wt%，尽管大多数玻璃颗粒表现出较窄的范围。水泡结构表明挥发性超压释放主要发生在后期岩浆上升之前，我们推断水泡形成是对钻井引起的减压的反应。流纹质玻璃的质地和化学性质与宿主长铁矿的可变部分熔化一致。钻井恢复序列表明，清澈的岩浆（较低程度的部分熔融）覆盖在棕色岩浆（较高程度的部分熔融）上。同位素和水物种通过混合的大气和岩浆成分流体支持这些部分熔体的高温水合。部分熔融和缺乏结晶的结构证据表明岩浆正在产生，因此不断增长的岩浆体具有很高的地热能提取潜力。产生了具有化学和结构异质性的水合流纹岩岩浆，然后通过钻井扰动增强了这些岩浆。这种部分熔化可能广泛发生在岩浆房上方的地壳中，在那里复杂的侵入系统可以形成并提供重新熔化主岩所需的热量和流体。我们的研究结果强调需要对不稳定的火山口进行更高分辨率的地球物理监测，以进行危险评估和地热勘探。我们还深入了解浅层硅质岩浆对钻孔的反应，