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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Changing Eruptive Styles In Basaltic Explosive Volcanism: Examples From Croscat Complex Scoria Cone, Garrotxa Volcanic Field (ne Iberian Peninsula)
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Changing Eruptive Styles In Basaltic Explosive Volcanism: Examples From Croscat Complex Scoria Cone, Garrotxa Volcanic Field (ne Iberian Peninsula)

机译：玄武岩爆炸性火山中喷发样式的变化：以克罗斯卡特复杂的斯科里亚圆锥体，加罗萨火山场（伊比利亚半岛）为例

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The Croscat pyroclastic succession has been analysed to investigate the transition between different eruptive styles in basaltic monogenetic volcanoes, with particular emphasis on the role of phreatomagmatism in triggering Violent Strombolian eruptions. Croscat volcano, an 11 ka basaltic complex scoria cone in the Quaternary Garrotxa Volcanic Field (GVF) shows pyroclastic deposits related both to magmatic and phreatomagmatic explosions. Lithofacies analysis, grain size distribution, chemical composition, glass shard morphologies, vesicularity, bubble-number density and crystallinity of the Croscat pyroclastic succession have been used to characterize the different eruptive styles. Eruptions at Croscat began with fissural Hawaiian-type fountaining that rapidly changed to eruption types transitional between Hawaiian and Strombolian from a central vent. A first phreatomagmatic phase occurred by the interaction between magma and water from a shallow aquifer system at the waning of the Hawaiian- and Strombolian-types stage. A Violent Strombolian explosion then occurred, producing a widespread (8 km2), voluminous tephra blanket. The related deposits are characterized by the presence of wood-shaped, highly vesicular scoriae. Glass-bearing xenoliths (buchites) are also present within the deposit. At the waning of the Violent Strombolian phase a second phreatomagmatic phase occurred, producing a second voluminous deposit dispersed over 8.4 km~2. The eruption ended with a lava flow emission and consequent breaching of the western-side of the volcano. Our data suggest that the Croscat Violent Strombolian phase was related to the ascent of deeper, crystal-poor, highly vesicular magma under fast decompression rate. Particles and vesicles elongation and brittle failure observed in the wood-shaped clasts indicate that fragmentation during Violent Strombolian phase was enhanced by high strain-rate of the magma within the conduit.
机译：已对Croscat火山碎屑演替进行了分析，以研究玄武岩单基因火山的不同喷发方式之间的过渡，特别强调了岩浆作用在触发暴力性Strombolian喷发中的作用。克罗斯卡特火山是第四纪Garrotxa火山场（GVF）中的11 ka玄武岩复式圆锥体，显示了与岩浆和岩浆爆炸有关的火山碎屑沉积物。 Croscat火山碎屑演替的岩相分析，粒度分布，化学成分，玻璃碎片形态，囊泡，气泡数密度和结晶度已被用来表征不同的喷发样式。克罗斯卡特（Croscat）的喷发始于夏威夷裂隙型喷泉，并从中央喷口迅速转变为在夏威夷和斯特龙伯利期之间过渡的喷发类型。岩浆与水的相互作用是由岩浆和浅层含水层系统中的水之间的相互作用在夏威夷型和斯特伦伯利亚型阶段逐渐减弱时发生的。然后发生了暴力的Strombolian爆炸，产生了一个巨大的（8平方公里）巨大的提夫拉毯。相关的沉积物的特征是存在木质的高囊泡渣ria。沉积物中也存在含玻璃的异种石（硬硅钙石）。在猛烈的Strombolian相减弱时，发生了第二岩浆岩相，产生了第二个大量沉积物，分散在8.4 km〜2的范围内。火山喷发以熔岩流喷出而告终，并因此破坏了火山的西侧。我们的数据表明，在快速减压速率下，Croscat暴力Strombolian期与深层，晶体贫乏，高囊泡岩浆的上升有关。在木形碎屑中观察到的颗粒和囊泡的伸长和脆性破坏表明，在暴力斯特伦伯利期阶段的碎裂通过导管内岩浆的高应变率而得到增强。

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