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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Origin and deformation of high porosity bands in the Takanoobane Rhyolite lava of Aso volcano, Japan
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Origin and deformation of high porosity bands in the Takanoobane Rhyolite lava of Aso volcano, Japan

机译：日本阿苏火山高野坝流纹岩熔岩中高孔隙度带的起源与变形

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摘要

In rhyolite lavas, the high porosity bands are often developed. They potentially act as pathways for gas movement to the lava surface. Since explosive activities of lavas are generally considered to be controlled by degassing system, understanding the origin and deformation process of the high porosity bands is important to assessing volcanic hazards. The Takanoobane rhyolite lava in the middle of Kyushu Island in SW Japan is effused at 51 +/- 5 ka. The volume, flow length, and thickness are 0.14 km(3), >2 km, and about 90 m, respectively. The central crystalline part of the lava is characterized by the light-colored bands defined by the high porosity zone (HPZ). On the basis of geological and petrographical studies, we revealed that the HPZ was primary formed by ductile-brittle tearing of the lava (known as cavitation). According to the AMS results, the HPZs were subsequently stretched and flattened laterally during the concentric spreading of the lava. This deformation process could stretch the HPZ not only radially but also laterally. This effective stretching developed the HPZ into pervasive thin bands. Since the HPZs act as degassing pathways to the lava surface, the pervasive HPZ bands may play a role in providing volcanic gasses to void spaces created in surface fold hinges of rhyolite lavas. Thus, this degassing system may promote explosive activity of the lava surface. (C) 2015 Elsevier B.V. All rights reserved.
机译：在流纹岩熔岩中，通常会形成高孔隙度带。它们潜在地充当气体流向熔岩表面的途径。由于通常认为熔岩的爆炸性活动是由脱气系统控制的，因此了解高孔隙度带的成因和变形过程对于评估火山灾害非常重要。日本西南部九州岛中部的高高根流纹岩熔岩喷出的温度为51 +/- 5 ka。体积，流量长度和厚度分别为0.14 km（3），> 2 km和大约90 m。熔岩的中心结晶部分的特征是由高孔隙度区（HPZ）定义的浅色带。在地质和岩石学研究的基础上，我们发现HPZ主要是由熔岩的韧性脆性撕裂（称为空化）形成的。根据AMS的结果，HPZ随后在熔岩同心扩散期间被横向拉伸和展平。这种变形过程不仅可以径向拉伸HPZ，还可以横向拉伸HPZ。这种有效的拉伸将HPZ变成了无处不在的细带。由于HPZs是通向熔岩表面的除气途径，因此泛滥的HPZ带可能在向流纹岩熔岩表面褶皱铰链中形成的空隙空间提供火山气方面发挥作用。因此，该脱气系统可促进熔岩表面的爆炸活性。 （C）2015 Elsevier B.V.保留所有权利。

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