近日，美国贝勒大学Michael Manga等人报道，再水合玻璃海湾沉积记录了黄石公园熔结凝灰岩的冷却过程。2024年3月26日出版的《地质学》发表了这项成果。

据研究人员介绍，水合前缘渗透50-135μm进入玻璃质流纹岩（产于黄石公园高原火山区梅萨瀑布凝灰岩石英晶体中）。水化前缘以陡峭的富集形式出现，在海湾开口处显示为2.4±0.6wt%H₂O，远高于内部0.9±0.2wt%H₂O的浓度。分子水占水富集的大部分。

研究人员称，水形态表明，水化前缘由吸收的大气水组成，这些大气水改变了流纹岩玻璃的原始岩浆成分。研究使用有限差分扩散模型，以证明随着熔结凝灰岩的冷却，玻璃再水合可能会在几十年的时间内发生。这样的温度和时间尺度与在皮纳图博山(菲律宾)和万烟谷(阿拉斯加)，冷却的熔结凝灰岩十年热液系统的罕见第一手观察相一致。

附：英文原文

Title: Rehydrated glass embayments record the cooling of a Yellowstone ignimbrite

Author: Kenneth S. Befus, James O. Thompson, Chelsea M. Allison, Anna C. Ruefer, Michael Manga

Issue&Volume: 2024-03-26

Abstract: Hydration fronts penetrate 50-135 μm into glassy rhyolite embayments hosted in quartz crystals from the Mesa Falls Tuff in the Yellowstone Plateau volcanic field. The hydration fronts occur as steep enrichments that reach 2.4 ± 0.6 wt% H₂O at the embayment opening, representing much higher values than interior concentrations of 0.9 ± 0.2 wt% H₂O. Molecular water accounts for most of the water enrichment. Water speciation indicates the hydration fronts comprise absorbed meteoric water that modified the original magmatic composition of the rhyolitic glass. We used finite difference diffusion models to demonstrate that glass rehydration was likely produced over a few decades as the ignimbrite cooled. Such temperatures and time scales are consistent with rare firsthand observations of decadal hydrothermal systems associated with cooling ignimbrites at Mount Pinatubo (Philippines) and the Valley of Ten Thousand Smokes (Alaska).

DOI: 10.1130/G51905.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G51905.1/637039/Rehydrated-glass-embayments-record-the-cooling-of