Abstract We established the phase equilibria of a representative tephriphonolitic sample of the 1631 eruption of Vesuvius (Italy). Experiments were conducted at 100 MPa, in the temperature range 950–1050 °C for melt water content ranging from 1.3 to 3.2 wt%, and at an oxygen fugacity (fO2) of NNO+1 to NNO+3 (one to three log unit above the fO2 of the Ni-NiO solid redox buffer). Results show that clinopyroxene, biotite and leucite dominate the crystallizing phase assemblage, with minor proportions of plagioclase and amphibole, in agreement with the petrological attributes of the tephra. Comparison between the phase proportions and compositions obtained in experiments and those observed in the rock indicates a pre-eruptive temperature of 950 ± 30° and a melt water content H2Omelt = 2.3 ± 0.3 wt%, for an oxygen fugacity around NNO+1. These T-H2O estimates are confirmed by empirical geothermometers based on experimental clinopyroxene and melt compositional trends. As for other Vesuvius eruptions, the most felsic part of the 1631 reservoir appears to have reached pre-eruptive leucite saturation, although a large amount of leucite microcrystals in the studied samples likely grew syn-eruptively. Our results confirm that magma storage conditions beneath Vesuvius became hotter, shallower, and more CO2-rich after the AD 79 Pompeii Plinian event.

中文翻译：

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对 1631 年维苏威火山喷发前喷发条件的实验限制

摘要 我们建立了 1631 年维苏威火山（意大利）喷发的代表性 tephriphonolitic 样品的相平衡。实验在 100 MPa、950–1050 °C 的温度范围内进行，熔体水含量范围为 1.3 至 3.2 wt%，氧逸度 (fO2) 为 NNO+1 至 NNO+3（1 至 3 log 单位）高于 Ni-NiO 固体氧化还原缓冲液的 fO2）。结果表明，单斜辉石、黑云母和白榴石在结晶相组合中占主导地位，斜长石和角闪石的比例较小，与火山灰的岩石学属性一致。实验中获得的相比例和组成与岩石中观察到的相比例和组成之间的比较表明，喷发前温度为 950±30°，熔体水含量 H2Omelt = 2.3±0.3 wt%，氧逸度在 NNO+1 左右。这些 T-H2O 估计值由基于实验单斜辉石和熔体成分趋势的经验地温计证实。至于其他维苏威火山喷发，1631 储层中最长英质的部分似乎已经达到了喷发前白榴石的饱和度，尽管研究样本中的大量白榴石微晶可能是同步喷发的。我们的结果证实，在公元 79 年庞贝普林尼亚事件之后，维苏威火山下方的岩浆储存条件变得更热、更浅、更富含二氧化碳。尽管研究样品中的大量白榴石微晶可能是协同生长的。我们的结果证实，在公元 79 年庞贝普林尼亚事件之后，维苏威火山下方的岩浆储存条件变得更热、更浅、更富含二氧化碳。尽管研究样品中的大量白榴石微晶可能是协同生长的。我们的结果证实，在公元 79 年庞贝普林尼亚事件之后，维苏威火山下方的岩浆储存条件变得更热、更浅、更富含二氧化碳。