CVClient

Kyohei Sano

  (佐野 恭平)

Profile Information

Affiliation
University of Hyogo
Degree
博士(理学)(九州大学)

Researcher number
40843321
J-GLOBAL ID
201901001207789188
researchmap Member ID
B000367091

External link

研究テーマ 

・火山噴火の多様性を支配する要因の解明

 火山噴火は,噴煙をもくもくとあげるような”爆発的な”噴火をすることもあれば,地上で溶岩を流すような”非爆発的な”噴火をすることがあります.目の前で噴火している火山が将来どのような挙動を示すのかを予測するためには,噴火様式が変化するメカニズムを理解することが重要です.火山岩の岩石組織は火山の噴火履歴を記録しており,解析することで噴火時の「マグマの挙動」を追いかけることができます.噴火様式の多様性を理解するために、火山岩に含まれるガラスや微小結晶の化学組成,形態,数密度などを解析し.火山の噴火プロセスを支配する要因を明らかにする研究を進めています.

・黒曜石を生み出す噴火の噴出過程・黒曜石石器の産地同定について
 粘り気の大きなネバネバしたマグマが噴火した際に「黒曜石」と呼ばれる,大部分がガラスで構成される大変美しい岩石が形成されることがあります.黒曜石を生み出すような粘性の大きな噴火の噴火プロセスや噴火様式が変化する要因を明らかにするために,岩石組織の解析からマグマ上昇や揮発性物質の放出過程を解明する研究を進めています.また,黒曜石を構成するガラスの化学組成や結晶の特徴に着目し,遺跡から出土する石器がどの産地に由来するものなのかを明らかにする”産地同定”に関する研究を,考古学者と連携しながら進めています.

 


Major Papers

 21
  • Kyohei Sano, Atsushi Toramaru
    JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH, 341 158-171, Jul, 2017  Peer-reviewedLead author
    To reveal the cooling process of a rhyolite-obsidian flow, we studied the morphology of plagioclase microlites in the Tokachi-Ishizawa lava of Shirataki, northern Hokkaido, Japan, where the structure of the lava can be observed from obsidian at the base of the flow to the innermost rhyolite. Needle-like micron-scale textures, known as "projections", occur on the short side surfaces of the plagioclase microlites. Using FE-SEM we discovered a positive correlation between the lengths and spacings of these projections. On the basis of the instability theory of an interface between melt and crystal, and to understand the length and spacing data, we developed a model that explains the positive correlation and allows us to simultaneously estimate growth rates and growth times. Applying the model to our morphological data and the estimated growth rates and growth times, we suggest that the characteristics of the projections reflect the degree of undercooling, which in turn correlates with lava structure (the obsidian at the margin of the flow experienced a higher degree of undercooling than the interior rhyolite). The newly developed method provides insights into the degree of undercooling during the final stages of crystallization of a rhyolitic lava flow. (C) 2017 Elsevier B.V. All rights reserved.
  • Kyohei Sano, Keiji Wada, Eiichi Sato
    JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH, 292 29-40, Feb, 2015  Peer-reviewedLead author
    Very few quantitative textural data exist for viscous obsidian lava eruptions, and it is still unclear from the mechanical behavior of ascending magmas if outgassing is controlled dominantly by brittle or ductile deformation. In order to obtain insights into how degassing and ascent proceed in such highly viscous magmas, we conducted textural and chemical analyses of the Tokachi-Ishizawa (TI) obsidian lava, in the Shirataki rhyolite volcanic area, northern Hokkaido, Japan, and estimated the water exsolution rate and ascent rate. The storage conditions of the TI lava are estimated from the Rhyolite-MELTS program as T = 840-860 degrees C and P = 50 MPa using the mineral assemblages and the chemical compositions of plagioclase phenoctysts and glass. To estimate the magma ascent rate, we measured the length, width, and number of oxide microlites using three-dimensional techniques. Textural analysis indicates that the microlite number densities (Nv [number/m(3)]) of oxide microlites in TI lava samples are 2.1 x 10(13) to 1.4 x 10(14), which correspond to water exsolution rates of 3.5 x 10(-9) to 1.7 x 10(-8) wt.%/s and ascent rates of 1.7 x 10(-6) to 1.1 x 10(-5) m/s. Together with an estimate of viscosity, the inferred ascent velocities allow us to examine the mechanical behavior of the magma in the conduit. We conclude that the development of permeability leading to outgassing is controlled by ductile deformation rather than brittle fracturing. (C) 2015 Elsevier B.V. All rights reserved.

Misc.

 5

Books and Other Publications

 2

Research Projects

 4