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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Tephra ring interpretation in light of evolving maar-diatreme concepts: Stracciacappa maar (central Italy)
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Tephra ring interpretation in light of evolving maar-diatreme concepts: Stracciacappa maar (central Italy)

机译：根据不断发展的maar-diatreme概念对Tephra戒指的诠释：Stracciacappa maar（意大利中部）

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Maar-diatreme volcanoes in their simplest form are thought to result primarily from discrete, subsurface phreatomagmatic explosions. Tephra ring deposits around maar craters are commonly interpreted in terms of a framework wherein explosions begin at shallow levels and migrate downward, ejecting progressively deeper-seated lithic clasts that contribute to the tephra rings. Additionally, variations in grain size of the deposits are sometimes inferred to record different degrees of fragmentation, which are in turn related to variations in magma-water ratios at the explosion sites. Recent detailed studies of diatremes and of maar tephra rings suggest a different conceptual model wherein explosions can happen at various vertical and lateral locations within a diatreme during its eruptive lifetime, rather than being limited to simple downward migration. Experiments, numerical modeling, and field data indicate that most explosions deeper than about 200-250 m will not vent to the surface, but instead contribute to mixing within the diatremes. Arrival of deep-seated lithics at the surface is related to this mixing process. Experiments also indicate that explosion phenomena can result in a range of emplacement mechanisms and grain sizes in tephra rings, even in the absence of variations in explosion mechanisms (fragmentation efficiency). Here we document the tephra ring of Stracciacappa maar (central Italy), and interpret its eruption and emplacement history in terms of evolving conceptual models along with a comparison to more traditional interpretations. Because most elements of both conceptual models are viable, the work points to an important need to develop criteria to distinguish between the various inferred mechanisms. (C) 2015 Elsevier B.V. All rights reserved.
机译：最简单形式的Maar-极端火山被认为主要是由离散的地下岩浆爆炸引起的。围绕着玛尔陨石坑的Tephra环沉积物通常是根据这样一个框架来解释的，即爆炸从浅层开始并向下迁移，并逐渐喷出深部的石屑碎屑，这些碎屑构成了Tephra环。另外，有时可以推断出沉积物晶粒尺寸的变化，以记录不同程度的破碎，这又与爆炸地点的岩浆水比变化有关。最近对diatremes和maar tephra环的详细研究提出了一种不同的概念模型，其中在diatreme的喷发寿命期间，爆炸可能发生在diatreme内的各个垂直和横向位置，而不仅限于简单的向下迁移。实验，数值模型和现场数据表明，大多数深度超过200-250 m的爆炸都不会排放到地表，而是有助于在径向上混合。深层石料到达表面与该混合过程有关。实验还表明，即使没有爆炸机理的变化（碎裂效率），爆炸现象也可能会导致一系列的特氟拉环的定位机制和晶粒尺寸。在这里，我们记录了Stracciacappa maar（意大利中部）的提菲拉环，并通过发展的概念模型以及与更为传统的解释的比较来解释其爆发和进驻历史。因为两个概念模型的大多数元素都是可行的，所以该工作指出了开发标准以区分各种推断机制的重要需求。 （C）2015 Elsevier B.V.保留所有权利。

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