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首页> 外文期刊>Contributions to Mineralogy and Petrology >Quantitative field constraints on the dynamics of silicic magma chamber rejuvenation and overturn
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Quantitative field constraints on the dynamics of silicic magma chamber rejuvenation and overturn

机译：硅质岩浆腔复活和倾覆动力学的定量场约束

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摘要

The catastrophic eruption of large-volume, crystal-rich silicic magmas is often proposed to be a consequence of reheating, melting and overturn of partially molten, buoyant silicic material following repeated injection of dense, hot mafic magma. To test this “rejuvenation hypothesis”, we analyze at high spatial resolution 33 examples of deformed interfaces between intrusive mafic and silicic layers in two plutons of the Coastal Maine Magmatic Province, USA. These deformed interfaces are thought to record the buoyant overturn of silicic crystal mush layers, apparently in response to the injection and cooling of hot, dense mafic magmas. We use spectral analysis and scaling theory along with petrologic and textural data to identify, characterize, and understand periodic deformations from the scale of individual crystals (≈1 cm) to the thicknesses of mafic and silicic layers. Deformations at the largest scale lengths (>100 m) are at wavelengths comparable to, or greater than, silicic layer thicknesses and support a conjecture that mafic recharge can cause large-scale Rayleigh–Taylor-type overturning of silicic mushy layers. By contrast, the smallest scales of individual crystals probably record effects related to production and buoyancy-driven rise of melt from the tops of silicic mushes in contact with overlying hot basalt, whereas intermediate scales are explained by compaction. Our results constrain the evolution of a thermal rejuvenation event and potentially identify a condition for a large-scale overturn of the magma chamber that may lead to eruption. This work provides the first quantitative field-based constraints on some of the key physical processes inherent to the rejuvenation hypothesis.
机译：经常提出，大体积，富含晶体的硅质岩浆的灾难性喷发，是由于反复注入致密的热镁铁质岩浆导致部分熔融的浮性硅质材料重新加热，熔融和倾覆的结果。为了检验这种“复兴假说”，我们以高空间分辨率分析了美国缅因州沿海岩浆省两个岩体中侵入性铁镁质和硅质层之间变形界面的33个例子。这些变形的界面被认为记录了硅质结晶糊状层的浮力翻转，显然是响应于热的，密集的铁镁质岩浆的注入和冷却。我们使用光谱分析和定标理论以及岩石学和质地数据来识别，表征和理解从单个晶体的标度（≈1cm）到镁铁质和硅质层厚度的周期性变形。最大尺度长度（> 100 m）的变形波长等于或大于硅质层的厚度，并支持一种推测，即铁镁质补给可导致硅质糊状层的大规模瑞利-泰勒式倾覆。相比之下，单个晶体的最小尺度可能记录了与硅质软膏顶部与上覆的玄武岩接触而产生的熔体和浮力驱动的熔体上升相关的影响，而中间尺度则由压实解释。我们的结果限制了热复兴事件的发展，并潜在地确定了岩浆室大规模倾覆的条件，这可能导致喷发。这项工作为复兴假说固有的一些关键物理过程提供了第一个基于定量场的约束。

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