Conduit- to Localized-scale Degassing during Plinian Eruptions: Insights from Major Element and Volatile (Cl and H2O) Analyses within Vesuvius AD 79 Pumice
Conduit- to Localized-scale Degassing during Plinian Eruptions: Insights from Major Element and Volatile (Cl and H2O) Analyses within Vesuvius AD 79 Pumice
复制标题
普林尼式喷发期间的管道局部脱气：来自维苏威火山 AD 79 浮石内主要元素和挥发物（Cl 和 H2O）分析的见解
DOI：
10.1093/petrology/egt069
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发表时间：
2014
影响因子：
3.9
通讯作者：
Tuffen, H.
中科院分区：
文献类型：
--
作者：
Shea, T.;Hellebrand, E.;Gurioli, L.;Tuffen, H.
对79块维苏威火山浮石的结构研究强调了火山喷发过程中岩浆脱气和结晶的复杂性，喷出的浮石有两种类型（白色和灰色），分别与不同的响岩和暗响岩组成的岩浆体有关。这些研究提出，速度梯度引起的空间变化，在管道和本地化规模的上升岩浆柱内的脱气。为了验证这一假设，挥发分（Cl，H2O）和浮石玻璃和熔融包裹体中的主要元素的分析进行了高空间分辨率的工具（显微拉曼光谱和电子探针），并结合主要元素和挥发分浓度的配置文件和地图。结果表明，熔体相的分化是通过脱气诱导白榴石结晶作用实现的，灰色浮石浆在脱气前得到了有效的均质化。由于Cl在快速上升过程中扩散比H2O慢，因此Cl表现为不相容元素，可用作结晶和H2O脱气的示踪剂。我们强调应变局部化的重要性，在生成区的优先出溶和气体的渗透途径，并建立脱气方案，将剪切带的影响。
Textural investigations of thead79 Vesuvius pumice emphasize the complexity of magma degassing and crystallization during the eruption, which emitted two types of pumice (white and gray) associated with different magma bodies of phonolitic and tephriphonolitic compositions respectively. These studies proposed that velocity gradients caused spatial variations in degassing within the ascending magma column at both the conduit and the localized scale. To validate this hypothesis, analyses of volatiles (Cl, H2O) and major elements in pumice glasses and melt inclusions were performed using high spatial resolution tools (microRaman spectrometry and electron microprobe) and combined with major element and volatile concentration profiles and maps. The results indicate that the melt phase differentiated through degassing-induced crystallization of leucite, and that the gray pumice magma was efficiently homogenized prior to degassing. Because Cl diffuses more slowly than H2O during fast ascent, it behaves as an incompatible element and can be used as a tracer of crystallization and H2O degassing. We emphasize the importance of strain localization in generating zones of preferential exsolution and permeable pathways for gases, and establish degassing scenarios that incorporate the effects of shear-zones.