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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Evolution of the mafic Villa Senni caldera-forming eruption at Colli Albani volcano, Italy, indicated by textural analysis of juvenile fragments
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Evolution of the mafic Villa Senni caldera-forming eruption at Colli Albani volcano, Italy, indicated by textural analysis of juvenile fragments

机译：通过对青少年碎片的质地分析表明，意大利科利阿尔巴尼火山的黑手质维拉森尼破火山口形成喷发的演化

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摘要

The Villa Senni Formation (355 ka) represents the youngest mafic caldera-forming eruption of the Colli Albani Volcano (Central Italy), and one of the best exposed large mafic ignimbrite successions on Earth. The unusual Si-undersaturated and high-K composition of the magma, and corresponding low magma viscosity, raise important questions about the conditions of magma ascent, eruption, and fragmentation that led to such a large explosive eruption. We examined the juvenile dast textures - that is, the abundance, shape, size and number density of both vesicles and leucite microlites - to reconstruct the fragmentation conditions and to trace major changes in the ascent rate and vesiculation history of the magma associated with caldera collapse. The juvenile textures record two major changes in the eruption dynamics through the stratigraphy. First, the sudden depressurization of the magma chamber and the onset of the first ignimbrite-forming phase are marked by a dramatic increase in the magma ascent velocity inferred by a decrease in vesicle and leucite microlite sizes and increase in their number densities. Second, the progressive restoration of pressure within the magma reservoir as a consequence of caldera collapse is recorded by an inversion of vesicle and leucite microlite textures, which suggest a strong decrease in magma ascent rate. Complex vent conditions in this later phase of the caldera collapse are recorded by the diversity of textural features, variation in magma chemistry and the abrupt changes in the stratigraphic record (including the presence of co-ignimbrite breccias, spatter dasts and lithics).
机译：Villa Senni地层（355 ka）代表了Colli Albani火山（意大利中部）中最年轻的镁铁质火山口形成喷发，也是地球上最暴露的大型镁铁质火成岩演替之一。岩浆中异常的硅欠饱和和高K成分，以及相应的低岩浆粘度，引发了有关导致如此大爆炸爆发的岩浆上升，喷发和破碎状况的重要问题。我们检查了幼虫的质地-即囊泡和白云母微晶的丰度，形状，大小和数量密度-来重建碎裂条件并追踪与破火山口塌陷相关的岩浆上升速率和溶栓历史的主要变化。幼年质地通过地层学记录了喷发动力学的两个主要变化。首先，岩浆腔的突然降压和第一个火成岩阶段的开始，其特征是岩浆上升速度的急剧增加，这是由于囊泡和白云母微晶尺寸的减少以及其数量密度的增加而引起的。第二，由于破火山口塌陷而导致的岩浆储层内压力的逐步恢复是通过囊泡和白云岩微岩质地的倒置来记录的，这表明岩浆上升速度大大降低。火山口坍塌的后期，复杂的出气条件通过构造特征的多样性，岩浆化学的变化和地层记录的突然变化（包括共生角砾岩角砾，飞溅的碎屑和岩性）来记录。

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  • 来源
    《Journal of Volcanology and Geothermal Research》 |2012年第1期|p.37-54|共18页
  • 作者

    Anna Paula Vinkler; Katharine Cashman; Guido Giordano; Gianluca Groppelli;

  • 作者单位

    Department of Earth Sciences, University of Milan, Via Mangiagalli 34, Milan 20133, Italy,CNR-IDPA Milano section, Via Mangiagalli 34, Milan 20133, Italy,Department of Geological Sciences, University of Roma Ire, Lgo S. Murialdo 1, Roma 00146, Italy;

    Department of Geological Sciences, 1272 University of Oregon, Eugene, OR 97403, USA;

    Department of Geological Sciences, University of Roma Ire, Lgo S. Murialdo 1, Roma 00146, Italy;

    CNR-IDPA Milano section, Via Mangiagalli 34, Milan 20133, Italy;

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  • 正文语种 eng
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  • 关键词

    fragmentation; juvenile textures; mafic ignimbrite; caldera;

    机译：碎片化少年质地;镁铁质火成岩破火山口;

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