Rheology of phonolitic magmas – the case of the Erebus lava lake
Rheology of phonolitic magmas – the case of the Erebus lava lake
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DOI：
10.1016/j.epsl.2014.11.042
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发表时间：
2015-02
影响因子：
5.3
通讯作者：
C. Losq;D. Neuville;R. Moretti;P. Kyle;C. Oppenheimer
中科院分区：
文献类型：
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作者：
C. Losq;D. Neuville;R. Moretti;P. Kyle;C. Oppenheimer
长期活跃的熔岩湖比较罕见，通常与低粘度玄武岩浆有关。南极洲的埃里伯斯火山是现今独一无二的一个响岩熔岩湖。响岩岩浆可以爆发，如公元79年意大利维苏威火山的普林尼式喷发，因此了解它们的物理性质是很重要的。埃里伯斯的响岩的硅含量比维苏威火山略高，但其目前的活动主要是非爆炸性的。作为对理解这种对比喷发行为的贡献，我们专注于这些可比岩浆之间的流变学差异。特别是，我们评估的粘度Erebus响岩岩浆的理论和经验框架内整合新的实验数据。由此产生的模型能够估计Erebus熔体粘度作为温度、晶体和水浓度的函数，具有至多±0.45 log（Pa·s）的不确定性。使用这些参数的报告范围内，我们预测，在上部区域的铅垂系统的埃里伯斯的岩浆粘度范围在10 5和10 7 Pa·s之间。这是大大高于迄今为止被认为具有重大意义的建模的熔岩湖，导管和岩浆库系统的动态。我们的分析强调了在计算岩浆粘度时遇到的一般性挑战，并提出了一种可应用于其他情况的方法。
Long-lived active lava lakes are comparatively rare and are typically associated with low-viscosity basaltic magmas. Erebus volcano, Antarctica, is unique today in hosting a phonolitic lava lake. Phonolitic magmas can erupt explosively, as in the 79 CE Plinian eruption of Vesuvius volcano, Italy, and it is therefore important to understand their physical properties. The phonolite at Erebus has slightly higher silica content than that at Vesuvius yet its present activity is predominantly non-explosive. As a contribution to understanding such contrasting eruptive behaviour, we focus on the rheological differences between these comparable magmas. In particular, we evaluate the viscosity of the Erebus phonolite magma by integrating new experimental data within a theoretical and empirical framework. The resulting model enables estimation of the Erebus melt viscosity as a function of temperature, crystal and water concentrations, with an uncertainty of, at most,±0.45 log (Pa s). Using reported ranges for these parameters, we predict that the magma viscosity in the upper region of the plumbing system of Erebus ranges between 10 5 and 10 7 Pa s. This is substantially higher than has been hitherto considered with significant implications for modelling the dynamics of the lava lake, conduit and magma reservoir system. Our analysis highlights the generic challenges encountered in calculation of magma viscosity and presents an approach that can be applied to other cases.