火山灰から見た2008年の桜島昭和火口の再活動過程

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(2) ²³±´:µ±¶·¸¹±º»3/¼S½ ,**3 1 : +. ; ,**3 +, : ,, ;. Re-activation Process of Showa Volcanic Vent at Sakura jima Volcano in ,**2 : Evidence From Volcanic Ash Isoji MIYAGI, Jun’ichi ITOH, Hiroshi SHINOHARA and Kagoshima Observatory, Japan Meteorological Agency We describe reactivation processes of the Showa volcanic vent at Sakura jima volcano, Kagoshima, Japan. The Showa volcanic vent is located on the east side hill of Minami-dake summit vent at Sakura jima volcano. While Minami-dake summit vent has been active intermittently for the past five decades, the Showa volcanic vent was dormant for an interval of about /2 years until . June ,**/. Ash samples analyzed were obtained from volcanic explosions of both Showa and Minamidake summit vents from +32+ to ,**3. The analyses and observations on the volcanic ash samples include (+) amount of water soluble chlorine and sulfur adsorbed on volcanic ash particles, (,) mineral identification using X-ray di#raction patterns, (-) color measurement, (.) simplified particle size analysis of volcanic ash, (/) micrographic observations of ash particles using an optical binocular microscope and a SEM, and (0) chemical analysis of minerals and glasses in ash particles with an EPMA. (+) and (,) suggested that the proportion altered/non-altered blocky particles in volcanic ash from the Showa volcanic vent was decreased from ,**2 to ,**3. (,), (-), and (/) indicated a gradual increase in temperature of the vent with time. We regard (+)-(/) features as results of a gradual reactivation process of the Showa volcanic vent since . June ,**/ by May ,**2. Key words : Sakura jima, Volcanic ash, Backscattered Electron Images, XRD, Volcanic gas. +ῌ ῏ ῍ ῐ ῎. <=5 >+,+-?@7 A'BCDEF$. >+,+-?@7 A'BCDEF$ 2G. HI%" JK.LA'MN5$ OP2%Q. 2RS5T0/ 5U"V.WMA- XY. Z[KM\]^_àbcd]!5. e5L[KM@$f0-M0 +,+gh . 1@i0Mj.klUm'-&' 5 . "# $ %&' Ryan, +321 ; (

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(4) -*/ῌ2/01 + + + ! Kagoshima observatory, Japan Meteorological Agency Geological Survey of Japan, Tsukuba Central 1, +ῌ+ῌ+. Higashi, Tsukuba, Ibaraki -*/ῌ2/01, Japan. Corresponding author : Isoji Miyagi e-mail : miyagi.iso+.***@aist.go.jp.

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(173). 38. ./012345*+678,-./9: 0;< Nakamura, +33/ DEF:;<GHIJK L. M N>?9@AOPQ -=$R>SQTB UCODBUCVEGFPW H=$RX/GY HIGZ =J[/0\8DK]P9S^ LMGHN_ O`D< ῏. ῎. =$RhUVWHMi jXYklT>mnD ]^qQSMISM - =o\_rD`s HMi tuvw7DabxcPQSdeyfR>z {$|}X~ghR ZPQij9P kl mno\o p pql>r s9qM ntTfcdR lT u CvwDxPQSMISM 8v Byz lT{|vwDxPQSMISM }~Tfcd R !lO ZPQj9 lT MvwxOa?9`D SMISM y ῌ ῑ ῐ ῍ ¤¥¦"# X§ (,**2) MT 5 6@7z-=$¡I¢¨ =$AB8 C9 ,**2 = P., +-.p. Anderson, O.L. (+312) The role of magma vapors in volcanic tremors and rapid eruptions. Bull. Volcanol., .+, -.+ῌ-/-. Barron, V. and Torrent, J. (+320) Use of the KubelkaMunk theory to study the influence of iron oxides on soil colour. J. Soil Sci., -1, .33ῌ/+*. Cashman, K.V. and Blundy, J.D. (,***) Degassing and crystallization of ascending andesite and dacite. Philos. Trans. R. Soc. Lond. A, -/2, +.21ῌ+/+-. Clark, S.P. J. (+300) Thermal conductivity. In Handbook of physical constants. Geol. Soc. Am. Mem., 31, .0*ῌ.2,. Dingwell, D.B. (+330) Volcanic dilemma : flow or blow?. Science, ,1- +*/.ῌ+*//. "#©£¤ª« ¬ (,**2) -¥=# =K ¦\k§ =$AB8C9 ,**2 = B,0 12p. )$Y '¨©) (,**2) -¥=# =o\O =Kª\«®¯SQ =$AB 8C9 ,**2 = P-2 +-*p. Kazahaya, K., Shinohara, H. and Saito, G. (+33.) Excessive degassing of Izu-Oshima volcano : magma convection in a conduit. Bull. Volcanol., /0, ,*1ῌ,+0. ²³±} ´² (,**2) ³´µvw7DcSM ¶µ=#j{¥=#=$ ¶··¸¸3 wpj{ZlH =$AB8C9 ,**2 = P-3 +-+p.. !"#$%&'() !"#*$+%&',$() (,**2) =$>?123456@7 =$AB8C9 ,**2 = P.+ +--p. Koyaguchi, T. (,**/) An analytical study for +-dimensional steady flow in volcanic conduits. J. Volcanol. Geotherm. Res., +.-, ,3ῌ/,. Kubelka, P. and Munk, F. (+3-+) Ein Beitrag zur Optik der Farbanstriche. Zeitschrift fur technische Physik, +,, /3-ῌ0,*. aP$AQbcdR (,**2) S +* e-=$9Tf @7 '/ +3 = 0 g'/ ,* = - g aP$AQb cdRZ[=$o\cd\p Mangan, M. and Sisson, T. (,***) Delayed, disequilibrium degassing in rhyolite magma : decompression experiments and implications for explosive volcanism. Earth Planet. Sci. Lett., +2-, ..+ῌ.//. Melnik, O., Barmin, A.A. and Sparks, R.S. J. (,**/) Dynamics of magma flow inside volcanic conduits with bubble overpressure buildup and gas loss through permeable magma. J. Volcanol. Geotherm. Res., +.-, /-ῌ02.. (,**1) =$ : O=$o\ =$ /, -++ῌ---.. (,**,) W=$R l : ¡=$ ,*** = 2 g +2 =$ ¢c =$ .1 1/1ῌ10+..

(174) (,**3) - +32-,**2 = =$RKYi BTf\pcd£U 9 no. .23. Miyagi, I., Yurimoto, H. and Takahashi, E. (+331) Water solubility in albite-orthoclase join and JR-+ rhyolite melts at +*** and /** to ,*** bars, determined by microanalysis with SIMS. Geochem. J., -+, /1ῌ0+. Miyagi, I., Matsubaya, O. and Nakashima, S. (+332) Change in D/H ratio, water content and color during dhydration of hornblende. Geochem. J., -,, --ῌ.2. Nakamura, M. (+33/) Continous mixing of crystal mush and replenished magma in the ongoing Unzen eruption. Geology, ,-, 2*1ῌ2+*. Ryan, M.P. (+321) Neutral buoyancy and the mechanical evolution of magmatic systems. In Magmatic processes : physicochemical principles (Mysen, B.O. ed.), Geochem. Soc. Special Publ., +, ,/3ῌ,21. Suzuki, Y., Gardner, J.E. and Larsen, J.F. (,**0) Experimental constraints on syneruptive magma ascent related to the phreatomagmatic phase of the ,*** A.D. eruption of Usu volcano. Japan. Bull. Volcanol., doi +*.+**1/s **../-**0-**2.--. Swanson, S.E. (+311) Relation of nucleation and crystal growth rate to the development of granitic textures. Amer. Mineral., 0,, 300ῌ312. , ¤ (+33.) °¬B®Oy¯ ° Li BA±9 .- +ῌ+3. Takeuchi, S. (,**.) Precursory dike propagation control of viscous magma eruptions. Geology, -,, +**+ῌ+**.. ¹Pº¡¹»$±Hoang NGUYENº¼» $¼½¥½ (,**/) -=$A./.

(175)

(176) ,**2 !"#$%&'( .2B, +ῌ1. Yamanoi, Y., Takeuchi, S., Okumura, S., Nakashima, S. and Yokoyama, T. (,**2) Color measurements of volcanic ash deposits from three di#erent styles of summit activity at Sakura jima volcano, Japan : conduit processes recorded in color of volcanic ash. J. Volcanol. Geotherm. Res., doi : +*.+*+0/j.jvolgeores.,**1.++.*+-. =>?@ (,**2) OPQRGH)*+,- " STU0 ,**2 P.* +--p. =>?@VWX (,**2) OPQRY1GH. 39. )*+,- . +* / 0123,- 45 +3 0 645 ,* - 6 !"#$%&'78 %&9:;< +-+ῌ+-0. =>?@ABCDEF (,**1) GH)*+,

(177) IJK LMNG /, +,+ῌ +,0. Zimanowski, B., Buttner, R., Lorenz, V. and Hafele, H.-G. (+331) Fragmentation of basaltic melt in the course of explosive volcanism. J. Geophys. Res., +*,, 2*-ῌ2+.. Z0[\ ] ^X.

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