Supervolcano eruptions driven by melt buoyancy in large silicic magma chambers
Supervolcano eruptions driven by melt buoyancy in large silicic magma chambers
复制标题
DOI：
10.1038/ngeo2042
复制
发表时间：
2014-02
影响因子：
18.3
通讯作者：
W. Malfait;R. Seifert;S. Petitgirard;J. Perrillat;M. Mezouar;T. Ota;E. Nakamura;P. Lerch;C. Sanchez‐Valle
中科院分区：
文献类型：
--
作者：
W. Malfait;R. Seifert;S. Petitgirard;J. Perrillat;M. Mezouar;T. Ota;E. Nakamura;P. Lerch;C. Sanchez‐Valle
在地质记录中，超级喷发在喷发量和对环境的影响方面都令所有历史上的火山事件相形见绌。这种富含硅质的岩浆喷发形成了巨大的火山口。触发这些超级喷发的机制是难以捉摸的，因为发生在传统火山系统中的过程不能简单地扩大到超级火山下面更大的岩浆室。岩浆补给引起的岩浆库的超压作用是较小喷发的常见触发因素，但不足以产生大型超级火山岩浆室的喷发。岩浆浮力可能会产生足够的超压，但这种触发机制的效率尚未得到测试。在这里，我们使用X射线吸收的同步加速器测量来确定富含二氧化硅的岩浆的密度，其压力和温度分别高达3.6GPA和1,950 K。我们将我们的结果与现有的环境压力下富硅岩浆密度的测量相结合，表明岩浆浮力可以在大型超级火山岩浆室的屋顶上产生超过10-40 兆帕的临界超压，即使岩浆中的挥发分不饱和也是如此。我们的结论是，岩浆浮力本身是触发超级喷发的一种可行机制，尽管岩浆补给和碎屑再生、挥发饱和度或构造应力在特定喷发期间可能是重要的。
Super-eruptions that dwarf all historical volcanic episodes in erupted volume and environmental impact are abundant in the geological record. Such eruptions of silica-rich magmas form large calderas. The mechanisms that trigger these super-eruptions are elusive because the processes occurring in conventional volcanic systems cannot simply be scaled up to the much larger magma chambers beneath supervolcanoes. Over-pressurization of the magma reservoir, caused by magma recharge, is a common trigger for smaller eruptions, but is insufficient to generate eruptions from large supervolcano magma chambers. Magma buoyancy can potentially create sufficient overpressure, but the efficiency of this trigger mechanism has not been tested. Here we use synchrotron measurements of X-ray absorption to determine the density of silica-rich magmas at pressures and temperatures of up to 3.6 GPa and 1,950 K, respectively. We combine our results with existing measurements of silica-rich magma density at ambient pressures,to show that magma buoyancy can generate an overpressure on the roof of a large supervolcano magma chamber that exceeds the critical overpressure of 10–40 MPa required to induce dyke propagation, even when the magma is undersaturated in volatiles. We conclude that magma buoyancy alone is a viable mechanism to trigger a super-eruption, although magma recharge and mush rejuvenation, volatile saturation or tectonic stress may have been important during specific eruptions.