Pre-eruptive storage conditions and eruption dynamics of a small rhyolite dome: Douglas Knob, Yellowstone volcanic field, USA
Pre-eruptive storage conditions and eruption dynamics of a small rhyolite dome: Douglas Knob, Yellowstone volcanic field, USA
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DOI：
10.1007/s00445-014-0808-8
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发表时间：
2014-03-01
影响因子：
3.5
通讯作者：
Gardner, James E.
中科院分区：
文献类型：
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作者：
Befus, Kenneth S.;Zinke, Robert W.;Gardner, James E.
控制流纹岩岩浆喷发的规模、持续时间和风格的性质和过程由于缺乏直接观测而受到很大的限制。在这里，我们调查的小体积，非爆炸性的端元。特别是，我们确定了道格拉斯旋钮，0.011公里（3）的黑曜石圆顶，从黄石火山系统的500米长的裂缝喷发的喷发前的存储条件和喷发动力学。为了确定喷发前的存储条件，我们分析了斑晶，基质玻璃，石英为主体的玻璃夹杂物的电子显微镜和傅立叶变换红外分析的组合物。喷发前的熔体是高硅流纹岩（类似于75 wt.% SiO2），并在喷发前储存在760 +/- 30摄氏度和50 +/- 25 MPa下，假设深度处蒸汽饱和。调查侵位动力学和运动学，我们测量了数密度和方向的微晶在不同位置的熔岩圆顶。最接近推断的裂隙喷口的样品中的微晶是最对齐的。对齐不增加远离排气口的距离，这表明微晶记录导管过程。株
The properties and processes that control the size, duration, and style of eruption of rhyolite magma are poorly constrained because of a paucity of direct observations. Here, we investigate the small-volume, nonexplosive end-member. In particular, we determine the pre-eruptive storage conditions and eruption dynamics of Douglas Knob, a 0.011-km(3) obsidian dome that erupted from a 500-m-long fissure in the Yellowstone volcanic system. To determine pre-eruptive storage conditions, we analyzed compositions of phenocrysts, matrix glass, and quartz-hosted glass inclusions by electron microprobe and Fourier-transform infrared analyses. The pre-eruptive melt is a high-silica rhyolite (similar to 75 wt.% SiO2) and was stored at 760 +/- 30 degrees C and 50 +/- 25 MPa prior to eruption, assuming vapor saturation at depth. To investigate emplacement dynamics and kinematics, we measured number densities and orientations of microlites at various locations across the lava dome. Microlites in samples closest to the inferred fissure vent are the most aligned. Alignment does not increase with distance traveled away from the vent, suggesting microlites record conduit processes. Strains of