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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Root zone processes in the phreatomagmatic pipe emplacement model and consequences for the evolution of maar-diatreme volcanoes
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Root zone processes in the phreatomagmatic pipe emplacement model and consequences for the evolution of maar-diatreme volcanoes

机译：岩浆岩管位模型中的根区过程及其对玛尔特迪特尔火山演化的影响

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摘要

The understanding of processes within the root zone of maar-diatreme volcanoes is important for the interpretation of the geology, volcanology and even hazard assessment of these volcanoes. In the phreatomagmatic model of pipe formation, the irregularly shaped root zone is the site of the phreatomagmatic explosions, and thus functions as the "engine" for pipe formation. In this model the root zone grows over a period of time in a series of many single thermohydraulic, i.e. phreatomagmatic, explosions. The explosions initially occur close to the surface and with ongoing explosive activity penetrate towards deeper levels. The ejection of country rock clasts from the root zone results in a mass deficiency in the root zone that causes the overlying tephra and the adjacent country rocks to subside passively in a sinkhole-like fashion into the root zone. Many phreatomagmatic eruptions consequently result in the formation of a cone-shaped diatreme. Thus with ongoing eruptions the cone-shaped diatreme has to grow systematically both in depth and diameter. During its growth; processes in the lower diatreme levels successively destroy the upper levels of the evolving root zone. At the surface, the maar crater in turn reacts to the underlying subsidence processes and also grows both in depth and diameter. Thermohydraulic explosions, which fragment both magma and the surrounding country rocks, mostly occur within the bottom part of the root zone. Violent explosions in small pipes may clear the overlying diatreme for a short period of time before tephra fall and collapse of the walls of the new crater refill the small initial diatreme. In larger pipes, via expansion of the mixture of highly pressurized water vapor, juvenile gas phases and explosively produced tephra, the confined and expanding eruption cloud has to pierce through the diatreme fill in a feeder conduit in order to erupt. Diatreme-clearing events in large pipes are difficult or impossible to maintain, since the explosive force in the root zone is only in exceptional instances strong enough to lift or entrain the entire diatreme tephra. Knowledge of the genetic relationships between root zones and diatremes is critical to understand pipe growth processes. The combination of such processes can lead to substantial variation in volcanic behavior and thus produce fundamentally different volcano and rock types. It is the purpose of this paper to outline important features of root zones and suggest their significance for the genesis and evolution of maar-diatreme and related volcanoes.
机译：对玛尔至尊火山根部区域内过程的理解对于解释这些火山的地质，火山学甚至危害评估至关重要。在管道形成的岩浆模型中，不规则形状的根部区域是岩浆爆炸的地点，因此，它是管道形成的“引擎”。在该模型中，根区域在一系列多次单次热液（即吞噬岩浆）爆炸中随时间增长。爆炸最初发生在地表附近，并且持续的爆炸活动渗透到更深的水平。乡村岩屑从根部区域弹出会导致根部区域质量下降，从而导致上覆的特非拉和邻近的乡村岩石被动地以沉陷状沉入根部区域。因此，许多岩浆喷发导致形成了锥形的异常。因此，随着不断的喷发，圆锥形的直径必须在深度和直径上系统地增长。在成长过程中；较低的diatreme级别的过程连续破坏了不断发展的根区的较高级别。在地表，火山口对下陷的沉降过程起反应，并且在深度和直径上都增大。破坏岩浆和周围的岩石的热液爆裂大多发生在根部区域的底部。小管道中的猛烈爆炸可能会在很短的一段时间内清除上覆的故障，然后使提菲拉坠落，新火山口的壁坍塌，重新充满较小的初始故障。在较大的管道​​中，通过膨胀高压水蒸气，少年气相和爆炸性生成的特非拉混合物，密闭且膨胀的喷发云必须刺穿馈线导管中的非饱和填充物才能喷出。大型管道中难以清除的事件难以维持或无法维持，因为在根部区域的爆炸力仅在特殊情况下足够强大，足以举起或带走整个非凡的特非拉。了解根部区域与异常之间的遗传关系对于了解管道生长过程至关重要。这些过程的结合可导致火山行为的实质性变化，从而产生根本不同的火山和岩石类型。本文的目的是概述根区的重要特征，并提出其对马阿尔特尔特特里亚特及相关火山的起源和演化的意义。

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