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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Thermochemical dynamics of magma chambers: A simple model
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Thermochemical dynamics of magma chambers: A simple model

机译：岩浆室的热化学动力学：一个简单的模型

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摘要

A magma chamber may be considered as an open, non adiabatic chemical reactor that continuously receives new liquid, crystallizes, and erupts lava. Heat is transferred to the walls, and crystals settle on the chamber floor. Considering, for simplicity, the chamber magma as a thermally and chemically homogeneous two-component liquid in which the solidification rate is a bell-shaped function of temperature and composition, the system is governed by two coupled differential equations for the evolution of temperature and composition with time. For constant external factors, such as fresh-magma input plow or heat loss flux, the magma chamber tends to a steady state. For a certain domain of external factor values, there are two stable steady state solutions instead of one. When the external factors vary slowly, the magma chamber state also drifts continuously, except when the external factors leave the bistability domain. Then all characteristics of the volcanic system undergo a sudden jump, for example, from basic to felsic composition and from high to low lava output flow when the fresh-magma input flow of a waning volcano declines. THe jump takes place over a time of the order of the magma residence time and is thus short compared to the lifetime of the chamber. Such a magmatic catastrophe, which may occur for a small and continuous evolution of the external conditions, results in a radical change in eruption style and volcanic products and may trigger an exceptionally large or violent eruption. THis kind of event may explain the widespread observation of compositional gaps in lava series (e.g., the Daly gap), a number of radical changes in eruptive style, and certain eruptions which appear unique in the lifetime of some composite volcanoes.
机译：岩浆室可视为开放的非绝热化学反应器，其连续接收新的液体，使其结晶并喷出熔岩。热量传递到墙壁上，晶体沉淀在反应室底部。为简单起见，将腔室岩浆视为热和化学均质的两组分液体，其中凝固速率是温度和成分的钟形函数，因此该系统由两个耦合的温度和成分演化微分方程控制随着时间的推移。对于恒定的外部因素，例如新鲜岩浆输入犁或热损失通量，岩浆室趋于稳定状态。对于外部因素值的特定域，有两个稳定的稳态解，而不是一个。当外部因素缓慢变化时，除非外部因素离开双稳态域，否则岩浆室状态也会连续漂移。然后，当逐渐减弱的火山的新鲜岩浆输入流量下降时，火山系统的所有特征都会突然发生跳跃，例如，从基本组成转变为长笛岩组成，从高熔岩输出流变为低熔岩输出流。跳跃发生在岩浆停留时间的数量级上，因此与腔室的寿命相比较短。这种岩浆灾难可能发生在外部条件的持续小幅演变中，导致喷发方式和火山产品发生根本性变化，并可能引发异常大或剧烈的喷发。这种事件可能解释了对熔岩序列中的成分间隙（例如Daly间隙）的广泛观察，喷发形式的许多根本性变化以及某些喷发在某些复合火山的寿命中似乎是独特的。

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