Understanding the impact of magmatic plumbing systems on explosive volcanic activity is important for hazard management. This study describes phase equilibria experiments using a high-silica andesite (HSA; SiO2 = 62.5 wt%) from the 2006 eruption of Augustine Volcano, Alaska. Experiments were conducted under H2O saturated conditions, $$f_{{0_{2} }}$$ = RRO (Re–ReO2 or ~ Ni–NiO + 2), at pressures of 50–200 MPa (PTotal = PH2O), and at temperatures of 800–1060 °C. Run durations varied from 23 to 539 h, inversely scaled with temperature. The natural Augustine HSA phase assemblage (plagioclase, two pyroxenes, Fe–Ti oxides, magnesio-hornblende) was reproduced at 860–880 °C and 120–200 MPa. Comparing experimental and natural glass and plagioclase compositions further refined those conditions to ~ 870 °C and 120–170 MPa. Crystallization of euhedral quartz was accompanied by biotite and small amounts of cummingtonite at T ≤ 850 °C. The relatively high temperature appearance of these typically low-T phases indicates that higher $$f_{{0_{2} }}$$ could enhance their stability. The storage conditions estimated from our experiments compare well with previous magma plumbing system models for Augustine from geophysical and petrological data. The refined experimental pressure range suggests a storage depth of 4.6–6.6 km, assuming a crustal density of 2650 kg/m3. The strong petrological and geochemical similarities between the products of the 2006, 1986, and 1976 eruptions suggest that the Augustine magmatic system had generally consistent crystallization conditions for the HSA lithology during that > 30-year time interval. The experimental results broad implications for understanding higher $$f_{{0_{2} }}$$ magmas at andesitic arc volcanoes.

中文翻译：

---

$$f_{{0_{2} }}$$f02 = RRO 处高 SiO2 安山岩的相平衡：对奥古斯丁火山和其他高 $$f_{{0_{2} }}$$f02 弧形安山岩的影响

了解岩浆管道系统对火山爆发活动的影响对于灾害管理很重要。本研究描述了使用 2006 年阿拉斯加奥古斯丁火山喷发的高二氧化硅安山岩（HSA；SiO2 = 62.5 wt%）进行的相平衡实验。实验在 H2O 饱和条件下进行，$$f_{{0_{2} }}$$ = RRO（Re-ReO2 或 ~ Ni-NiO + 2），压力为 50-200 MPa（PTotal = PH2O），并且在 800–1060 °C 的温度下。运行持续时间从 23 小时到 539 小时不等，与温度成反比。天然奥古斯丁 HSA 相组合（斜长石、两种辉石、Fe-Ti 氧化物、镁角闪石）在 860-880 °C 和 120-200 MPa 下再现。比较实验和天然玻璃和斜长石成分，进一步将这些条件细化到 ~ 870 °C 和 120–170 MPa。自形石英的结晶伴随着黑云母和少量的白云母在 T ≤ 850 °C。这些典型的低 T 相的相对高温外观表明较高的 $$f_{{0_{2} }}$$ 可以增强它们的稳定性。根据我们的实验估计的储存条件与以前根据地球物理和岩石学数据得出的奥古斯丁岩浆管道系统模型相比较。假设地壳密度为 2650 kg/m3，精确的实验压力范围表明储存深度为 4.6-6.6 km。2006 年、1986 年和 1976 年喷发产物之间强烈的岩石学和地球化学相似性表明，在 30 年以上的时间间隔内，奥古斯丁岩浆系统对于 HSA 岩性具有大体一致的结晶条件。