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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Understanding the evolution of a small-volume silicic fissure eruption: Puketerata Volcanic Complex, Taupo Volcanic Zone, New Zealand
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Understanding the evolution of a small-volume silicic fissure eruption: Puketerata Volcanic Complex, Taupo Volcanic Zone, New Zealand

机译：了解小规模硅质裂隙喷发的演变：新西兰陶波火山带Puketerata火山综合体

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摘要

The Puketerata Volcanic Complex formed as a result of a series of rhyolitic eruptions along a 2.5 km long NE-trending eruptive fissure at the southern margin of Maroa Volcanic Centre (Whakamaru caldera) at 16.5 ka. Initial deep-seated explosions were excavated and widen the pre-existing volcanic structures associated to earlier basaltic activity. The following emplacement of two lava domes and associated shallow-seated phreatomagmatic activity produced a widespread tephra blanket characterized by alternating surge and fall dominated pyroclastic units. The silicic magma (73% SiO2) erupted during the Puketerata activity was highly degassed, where explosive fragmentation was driven only by the interaction with external water. The lava domes and ejecta ring makes up more than two-thirds (98 x 10(6) m(3) DRE) of the total eruptive volume (similar to 143 x 10(6) m(3) DRE). The compound ring structures surrounding the larger dome totally overlap the underlying volcanic landforrns that formed during the initial phase. The ejecta ring around the larger dome represents a complex landform, which predominantly consists of outwardly thinning pyroclastic breccias forming fan-shape bodies relating to the series of destruction of the larger dome. Despite the relatively large combined dispersal area of the pyroclastic deposits generated by the entire activity (235 km(2)), the volume of single fall beds do not suggest individual explosive events exceeded VEI 2-3. The volcanic hazards associated with such small-volume volcanoes are largely ignored despite these eruptions being more frequent than eruption characterized by caldera collapses. The example of Puketerata suggests that small-volume volcanism often exhibits activity producing fissures, whereas the varied advancement of dykes influenced by external factors makes the course of the eruptions unpredictable in terms of geometry of vents and eruption styles. (C) 2017 Elsevier B.V. All rights reserved.
机译：Puketerata火山群是在16.5 ka的Maroa火山中心（Whakamaru火山口）南缘沿着2.5公里长的NE趋势喷发性裂隙形成的一系列流纹岩喷发而形成的。挖掘了最初的深层爆炸，并拓宽了与较早的玄武岩活动相关的先前存在的火山构造。随后两个熔岩穹顶的进入和相关的浅层岩浆活动，产生了一个广泛的特非拉毯，其特征是潮涌和跌落为主的火山碎屑单元交替发生。 Puketerata活动期间喷出的硅质岩浆（73％SiO2）被高度脱气，其中爆炸碎屑仅由与外部水的相互作用驱动。熔岩穹顶和喷出环占总喷发量的三分之二（98 x 10（6）m（3）DRE）（类似于143 x 10（6）m（3）DRE）。围绕大穹顶的复合环结构完全重叠了在初始阶段形成的下伏火山地貌。较大圆顶周围的弹射环代表复杂的地形，主要由向外变薄的火山碎屑角砾岩构成，形成扇形体，与大圆顶的一系列破坏有关。尽管整个活动（235 km（2））产生的火山碎屑沉积物的组合散布面积相对较大，但单个跌落床的体积并未表明单个爆炸事件超过了VEI 2-3。尽管这些喷发比火山口坍塌为特征的喷发更为频繁，但与这种小体积火山相关的火山危害却被很大程度上忽略了。 Puketerata的例子表明，小规模的火山活动经常表现出产生裂缝的活动，而受外部因素影响的堤坝前进的多样性使喷发的过程在喷口的几何形状和喷发方式方面无法预测。 （C）2017 Elsevier B.V.保留所有权利。

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