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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >The fragmentation threshold of pyroclastic rocks
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The fragmentation threshold of pyroclastic rocks

机译：碎屑岩碎裂阈值

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摘要

In response to rapid decompression, porous magma may fragment explosively. This occurs when the melt can no longer withstand forces exerted upon it due to the overpressure in included bubbles. This occurs at a critical pressure difference between the bubbles and the surrounding magma. In this study we have investigated this pressure threshold necessary for the fragmentation of magma. Here we present the first comprehensive, high temperature experimental quantification of the fragmentation threshold of volcanic rocks varying widely in porosity, permeability, crystallinity, and chemical composition. We exposed samples to increasing pressure differentials in a high temperature shock tube apparatus until fragmentation was initiated. Experimentally, we define the fragmentation threshold as the minimum pressure differential that leads to complete fragmentation of the pressurized porous rock sample. Our results show that the fragmentation threshold is strongly dependent on porosity; high porosity samples fragment at lower pressure differentials than low porosity samples. The fragmentation threshold is inversely proportional to the porosity. Of the other factors, permeability likely affects the fragmentation threshold at high porosity values, whereas chemical composition, crystallinity and bubble size distribution appear to have minor effects. The relationship for fragmentation threshold presented here can be used to predict the minimum pressure differential necessary for the initiation or cessation of the explosive fragmentation of porous magma. (C) 2004 Elsevier B.V. All rights reserved.
机译：响应快速减压，多孔岩浆可能会爆炸性破裂。当熔体由于包含的气泡中的超压而无法再承受施加在其上的力时，就会发生这种情况。这发生在气泡与周围岩浆之间的临界压力差处。在这项研究中，我们研究了岩浆破碎所需的压力阈值。在这里，我们介绍了火山岩碎裂阈值的第一次全面的高温实验量化，其孔隙度，渗透率，结晶度和化学成分变化很大。我们在高温冲击管设备中将样品暴露于不断增加的压差下，直到开始破碎。实验上，我们将碎裂阈值定义为导致压力多孔岩样完全碎裂的最小压力差。我们的结果表明，碎裂阈值强烈依赖于孔隙度。高孔隙度样品在比低孔隙度样品低的压差下破碎。碎裂阈值与孔隙率成反比。在其他因素中，渗透率可能会影响高孔隙率值下的碎裂阈值，而化学成分，结晶度和气泡尺寸分布似乎影响较小。此处呈现的碎裂阈值的关系可用于预测引发或停止多孔岩浆爆炸性碎裂所需的最小压力差。 （C）2004 Elsevier B.V.保留所有权利。

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