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首页> 外文期刊>Journal of Volcanology and Geothermal Research2012V243-244NOCT,15 >The 2008 eruption of Okmok Volcano, Alaska: Petrological and geochemical constraints on the subsurface magma plumbing system
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The 2008 eruption of Okmok Volcano, Alaska: Petrological and geochemical constraints on the subsurface magma plumbing system

机译：2008年，阿拉斯加奥克莫克火山爆发：地下岩浆管道系统的岩石学和地球化学约束

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摘要

The July-August 2008 phreatomagmatic eruption of Okmok Volcano produced -0.26 km~3 (DRE) of phenocryst-poor (1 to 2 vol.%) basaltic andesite ejecta, compositionally distinct from the basalt erupted during 1997 (51.90 wt.% SiO_2). Analyzed juvenile products are tan to dark gray vesicular lapilli (scoria), and dense, purple-black bombs. Whole-rock compositions cluster tightly (54.97 ± 0.25 wt.% SiO_2). The eruption also produced mafic ash containing basaltic groundmass glasses (52 wt.% SiO_2) and olivine-hosted melt inclusions (down to 47 wt.% SiO_2). The scoria and early-erupted ash contain compositionally similar plagioclase, clinopyroxene, and olivine phenocrysts. Olivine phenocrysts in the scoria and ash are not in equilibrium with the basaltic andesite whole-rock composition. Olivine-hosted melt inclusions yield 0.11 (± 0.04) to 3.61 (± 1.24) wt.% total H_2O by μ-FTIR, with an average of 1.23 ± 0.68 (lσ) wt.%. Three inclusions contain CO_2 = 37 to 49 ppm with the rest below detection. Solubility model-derived inclusion entrapment/re-equilibration depths extend from near surface to 4.6 (±2.5) km, in agreement with recent geophysical studies. The 2008 eruption was triggered by an influx of melt-rich basalt originating from the 3 to 6 km storage region beneath the center of the caldera, which intersected a shallower, more evolved magma body beneath Cone D. Our study concludes that the Okmok magma system is "mush-column" like, containing multiple magma bodies with a common and frequent replenishment source, but segregated with unique geochemical signatures.
机译：Okmok火山的2008年7月至8月发生的岩浆喷发产生了-0.26 km〜3（DRE）的稀晶玄武岩（占体积的1-2％），其成分不同于1997年爆发的玄武岩（51.90 wt。％SiO_2）。 。经分析的少年产品为棕褐色至深灰色的水疱性绒毛膜（粘膜炎），以及密集的紫黑色炸弹。全岩组合物紧密聚集（54.97±0.25 wt。％SiO_2）。火山喷发还产生了含玄武岩碎屑玻璃（52 wt。％SiO_2）和橄榄石型熔体夹杂物（低至47 wt。％SiO_2）的黑铁灰。火山灰和早期喷出的火山灰含有组成相似的斜长石，斜辉石和橄榄石的隐晶。火山灰和火山灰中的橄榄石类隐晶与玄武质安山岩全岩组成不平衡。橄榄石型熔体包裹体通过μ-FTIR产生的总H_2O为0.11（±0.04）至3.61（±1.24）wt。％，平均为1.23±0.68（lσ）wt。％。三个夹杂物的CO_2 = 37至49 ppm，其余未检出。溶解度模型衍生的包裹体包裹/重新平衡深度从近地表扩展至4.6（±2.5）km，与最近的地球物理研究一致。 2008年的火山喷发是由火山口中心下方3至6 km的储藏区涌入的富含熔体的玄武岩的涌入引起的，该玄武岩与C锥D下方的一个较浅，演化程度更高的岩浆体相交。我们的研究得出结论，Okmok岩浆系统类似于“蘑菇柱”，包含多个岩浆体，具有共同且频繁的补给源，但具有独特的地球化学特征。

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    Jessica F. Larsen; Maciej G. Sliwinski; Christopher Nye; Cheryl Cameron; Janet R. Schaefer;

  • 作者单位

    Department of Geology and Geophysics and Geophysical Institute, Rm. 308 Reichardt Building, 900 Yukon Dr., University of Alaska, Fairbanks, AK 99775, USA Alaska Volcano Observatory, USA Department of Geology and Geophysics and Geophysical Institute, Rm. 308 Reichardt Building, 900 Yukon Dr., University of Alaska, Fairbanks, AK 99775, USA;

    Department of Geology and Geophysics and Geophysical Institute, Rm. 308 Reichardt Building, 900 Yukon Dr., University of Alaska, Fairbanks, AK 99775, USA;

    State of Alaska Division of Geological and Geophysical Surveys, 3354 College Rd., Fairbanks, AK99709, USA Alaska Volcano Observatory, USA;

    State of Alaska Division of Geological and Geophysical Surveys, 3354 College Rd., Fairbanks, AK99709, USA Alaska Volcano Observatory, USA;

    State of Alaska Division of Geological and Geophysical Surveys, 3354 College Rd., Fairbanks, AK99709, USA Alaska Volcano Observatory, USA;

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  • 正文语种 eng
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  • 关键词

    Alaska; Basaltic andesite; Melt inclusions; Okmok Volcano; Petrology; Geochemistry;

    机译：阿拉斯加州;玄武质安山岩;融化夹杂物;Okmok火山;岩石学;地球化学;

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