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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Thermomechanical feedbacks in magmatic systems: Implications for growth, longevity, and evolution of large caldera-forming magma reservoirs and their supereruptions
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Thermomechanical feedbacks in magmatic systems: Implications for growth, longevity, and evolution of large caldera-forming magma reservoirs and their supereruptions

机译：岩浆系统中的热机械反馈：对大型火山口形成岩浆储层及其超喷发的生长，寿命和演化的影响

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Large magma bodies that feed super-eruptions and build batholiths are not instantaneously emplaced. Many accumulate over time scales of 10~5 to 10~6 years as part of magmatic episodes that last 10~7 years and propagate a thermal and magmatic front through the crust to stabilize the reservoirs in the upper crust. This history imposes a rheological and thermodynamic conditioning on the host rocks that sets in motion three feedbacks that promote growth and longevity of large silicic magma reservoirs. Herein we review the development of ideas about the thermomechanical evolution of large silicic magma systems and explore the feedbacks and their implications for the growth, longevity, and evolution of large silicic magma reservoirs. Feedback 1 promotes increasing temperatures and consequent lower viscosities in the host rocks and the development of a ductile halo. Feedbacks 2 and 3 are feedbacks that result from the thermal dependence of the Theological properties of this ductile halo. In feedback 2 low wall rock viscosities lead to dissipation of strain in the host rocks reducing the likelihood of eruption. Feedback 3 is a negative loop between volume change and pressurization also reducing the likelihood of wall rock failure and eruption. We show that these feedbacks are most pronounced in larger reservoirs (＞500 km~3) and conspire to promote reservoir growth. Predicted imprints of these feedbacks are extended melt present lifetimes, complex heterogeneous age records and crystal-rich magma in some large silicic magma reservoirs. In this framework, interruption of the slow steady progress towards viscous death and solidification manifests as a supereruption. Second boiling and recharge (including buoyancy effects) acting in concert or independently lead to roof uplift and extension and eruptions are finally triggered by downward propagating faults from the extended and weakened roof. This connotes a thermomechanical division of calderas into those where eruptions are triggered "internally" by magmatic processes and those that are triggered "externally" by faulting related to roof uplift and attenuation. The division is controlled by size of magma reservoir, although, true to nature, exceptions exist, demonstrating interruption of the feedbacks by other processes like tectonism.
机译：能够瞬间注入超喷发并形成岩心的大型岩浆体不会被放置。作为持续10〜7年的岩浆事件的一部分，许多岩层在10〜5至10〜6年的时间尺度上积累，并通过地壳传播热和岩浆锋，以稳定上地壳中的储层。这段历史在主体岩石上施加了流变学和热力学条件，从而引发了三个反馈，从而促进了大型硅质岩浆储层的生长和寿命。本文中，我们回顾了大型硅质岩浆系统热力学演化思想的发展，并探讨了这些反馈及其对大型硅质岩浆储层的生长，寿命和演化的影响。反馈1会促使温度升高，从而导致基质岩石的粘度降低，并导致延展性光晕的发展。反馈2和3是这种延性光环的神学特性对温度的热依赖性所产生的反馈。在反馈2中，低壁岩石粘度导致基质岩石中的应变消散，从而降低了喷发的可能性。反馈3是体积变化和增压之间的负循环，也减少了围岩破坏和喷发的可能性。我们表明，这些反馈在较大的水库（＞ 500 km〜3）中最为明显，并共同促进了水库的增长。这些反馈的预期印记是延长的熔体当前寿命，复杂的非均质年龄记录以及一些大型硅质岩浆储层中富含晶体的岩浆。在这种框架下，向粘性死亡和凝固的缓慢稳定进展的中断表现为一种超级爆发。共同作用或独立作用的二次沸腾和补给（包括浮力作用）会导致屋顶隆起和伸展，最终爆发是由伸展和削弱的屋顶向下传播的断层引起的。这意味着火山口的热机械划分为喷发过程是由岩浆过程“内部”触发的，而喷发是由与屋顶隆起和衰减有关的断层“外部”触发的。该划分受岩浆储集层的大小控制，尽管自然界中确实存在异常，这表明构造等其他过程对反馈的干扰。

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