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,**0

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,2  ,**03,+ 

Syneruptive magma ascent revealed by crystallization processes
Recent progresses with decompression experiments
Yuki SUZUKI῍This paper reviews the principles and the methods used to investigate the ascent process of water-saturated
magmas based on crystal texture and composition, which are especially relevant to recent progress made in
decompression experiments. The primary cause of syneruptive crystallization is an increase in the liquidus
temperature and resultant undercooling due to a decrease in dissolved H,O in the melt. Analyses of ejecta crystal
texture provide time-resolvable information.
Firstly, recent decompression experiments have improved knowledge regarding crystallization kinetics andhave conﬁrmed correlations made between ascent conditions, texture and crystal composition. The number
density of groundmass microlite, crystal size distribution, and crystal form all reﬂect e#ective undercooling (Te#). This increases with an increased pressure drop (P), and also with an increased decompression rate (P/t). If P or P/t match in an experiment series, we can compare the texture of the run products withrespect to the other parameters. The experiments conﬁrmed that the rates of crystal growth and nucleation showclassical bell-shaped curves with Te# . Growth rate reaches a peak at a lesser Te# than for nucleation.
Variation of Te# causes a shift in crystallization style.
Secondly, decompression experiments help in estimation of the rate and style of magma ascent during a
speciﬁc eruption through replication of crystals found in ejecta. To best reproduce natural ascent conditions one
needs to know a) the number of syneruptive ascent stages, each of which can be assigned an approximate constant
speed, b) temperature and pressure of magma at the start and end of each ascent stage, c) how texture evolved
during the syneruptive ascent. Ascent conditions are estimated for each stage based on the experimental
reproduction of the texture and composition of the natural ejecta. Accuracy in the estimation of ascent rate isthus inﬂuenced by errors in quantitative analysis of natural ejecta and the correlation of the decompression ratewith textural parameters. Such experimental approaches improve our interpretation of eruption mechanisms byenabling us to combine observation made upon the eruptive product and time-resolved geophysical data. The
application of this approach to the ,*** A.D. eruption of Usu Volcano in Japan is presented. With further
improvement in the experimental techniques both laboratory and observational studies on ejecta will play a more
important role in linking various volcanology research ﬁelds.
Key words : rate and style of magma ascent, e#ective undercooling, nucleation and growth rates, quantiﬁcation ofgroundmass microlite, experimental replication of crystals+ῌ ῐ ῎ ῑ ῏ !" #$%&V32*ῌ2/12 WXYZ[\]^Z[_`aNaNbNPQMcNdecf5LMNM
Department of Mineralogy, Petrology and Economic
Geology, Graduate School of Science, Tohoku University, Aoba-ku, Sendai, 32*ῌ2/12, Japan !" 3456789:;<'e-mail : suzukiyk@ganko.tohoku.ac.jp

HIJK 5LMNOPQR +33*'()* +,-"#$,'./012 =>?@ABC DEF Cashman, ,**. ; Cashman et al.,,*** ; Jaupart, +332 ; Rutherford and Gardner, ,***, G

STU 

   ¼

374

Fig. +. Procedures investigating magma ascent condition using crystallization. Italic letter indicates result in eachprocedure. Procedure and result at the starting point of arrow control those at the end point.

      ! "# !$ % &'&()*+,-./01234

5, 
,ῌ+

 

(Fig. +a) 559:;<=>?@A|DE>?@A_4:$ 1

B?C9% DE>F2 GH$ I JKFF ,29%  &'& !D

L&'&MNOP$ Q/R STUFC

E>F12653 $ M zPt

X!HYZL &'&9[$ ?@A\?@A:$ 1 !_5q 6789%VWI] ^_ 2: ` I,*** abc deP$fghij< X kl Cashman, ,**.` 9[mPnopq $ ?@2rsn B 

P$ ?@A\I]RtTU X- u` $ I

 :$ &'&12:^_n:n XMastin and Ghiorso X,***`  Conflow! $¡¢£ !HM¤9:&'&H!H¥¦§ `$y?

?@A¨ S© : Hª  5! M@43M zPt&'&./;{|<E« ¬p3­_ 78®6% 6$ d }~[  P$ , @Mvw

X. u`  , x VWPdM! $ &'&69H
43

?@A9%H$ DE>,6

59¯

Pt[ X kl Rutherford and Hill, +33-` [°6±²P$ ?CP³6d´

59

, q 6$  hij<qyH (Jaupart, +332 ;_5qRutherford and Gardner, ,***)$ 9:Pt

(Fig. ,a) ¯°±² ³:$&'&./;{|<E ¬p3­d´P$ M
zPt?@A¨ ©  Mµ¶9$ &'&H9:DE>9%t·¸¹º» XFig. - :\ ` M zPt?@A:$¶ · ]^~¸¹º» <*`¼

375

Fig. ,. Phase diagrams for isothermally decompressed felsic melt. a) A diagram showing increase of liquidus
temperature with decrease of pressure for water saturated conditions. Modiﬁed from Eichelberger (+33/).
,**, ,*, + MPa correspond to reservoir, conduit and near-surface, respectively. L, C and V represent liquid,
crystal and vapor, respectively. Boundaries of L vs. LµC and LµV vs. LµCµV denote liquidus. When
reservoir magma is water saturated and free from vapor, its melt part locates at “Melt”. As magma ascends
to surface and the melt is transformed to groundmass ("GMS”) of ejecta, the liquidus increases from T,** toT+. b) H,O-saturated phase relations. Modiﬁed from Cashman (,**.). Each phase is stable over lowpressure side of phase boundary, except hornblende. Orhopyroxene (Opx), augite (Aug), plagioclase (Pl),hornblende (Hb) and quartz(Qtz).

  

 ; Fig. -     !"#$%&'( )*+ , %  
- ./0 12- 34./5 671 8
9:; 89 <*12-=> ?@ABCDE*FGHI*+ Fig. ,b JKLMGNE<O  PQGRSE* T( DU-,PQVW 
XYZ[! HRS \QVWH]^E*+ (_X`a bc  de,F fgE(Y:h 
XY Rutherford and Hill, +33- ieG>E*+ G5*jk lmn!GPl(*H
XY Fig. - n!GhopqrstuFq*+

vSw.xqyzO{ !"JKL|}
,῍, ,>~U-@ABX*  % ,῍- ,῍. , ~ E*lH-@ABX*G5* (Cashman,,**.)+ l %B)  T) , B  => ,῍- F 7 -=>\BP lH* ,῍.

: &E*+,ῌ, 



Fig. -. BSE image of groundmass (micropumice in
Usu ,*** eruption). Microlites are magnetite(Mt), pigeonite (Pig) and plagioclase in orderof decreasing brightness. Skeletal plagioclase
microlite appears to show a swallow tail form
(S.T.) or to have a hollow ﬁlled with glass (H.
L.) depending on the orientation of the sectionof each crystal.

E*yzB¤¥ + #$ Pl(* An:G¦

Blundy and Cashman (,**+) ,    §H ,*ῌ ¨©H5(Y ª¦§« (Qz, Ab, Or, An)

U-=> B E*FBxF £u )*¬­« Qz῎, Ab῎, Or῎ B/®

!"#$% Bk*FG¯° qc + q±²³´§ :,¬­'(¡¢ (Qz-Ab-Or)£u

U V W ¼

376

 

(Tuttle and Bowen, +3/2)  kIRK0

QZ) i>q PN )*r+ (,**/)
 stuv ,**. ,-LAcwgx/Qz῎ 

 "H (Qz῎y/*)  '"6789zA B%!
P QZ.RK0
MPa ~hF/{.s] ?|}

XY"",ῌ- 

 + !"

() 0RKS1 #defgd. G!" Swanson et al. (+323) uv2"#$# 03  RK//{ _k" (Cashman,+33, ; Gardner et al., +332 ; Hammer et al., +333, ,*** ;Fig. .. Crystallization path for water-saturated
isothermal decompression (2**&) plotted in QzAb-Or haplogranitic system. Crystallizing phases
are feldspar (fs) and quartz (qz). Cotectic
lines, composition of H,O-saturated minima(ﬁlled circle) and eutectics are also shown as afunction of pressure. Redrafted from Figs +and ,b of Blundy and Cashman (,**+).

Nakada and Motomura, +333) 4 -  >5.()RK0*kP_"
 RKS67.8RK0R ?

` Dowty, +32* ; Kirkpatrick, +32+ ; Swanson, +311F N]! *k"  U9-L
!"#$# J:$;<t=.
//{ _3  () ?#$#
>N %$r) F +ῌ   U ?@  #$#EAB ¡ J:$;<t_"

 (Ebadi and Johannes, +33+ ; Luth0 ¢ C£k"

et al., +30. ; Tuttle and Bowen, +3/2 ; Fig. .) 

#$#J:$ m |D$ ¤k #$#():$ 7¥¦xJ:$


Blundy and Cashman (,**+)  ,** MPa!"#$# % (2**&) ''()*+",-0! R!§.¨8Y*0> ?()U ():$

 : -῍, 2

Y!Y./ 01  Tuttle and Bowen (+3/2)  Holtz et

3F §.¨8Y* _ ©:$

al. (+33,a) 23!45!" (Fig. .) () !" 

5.

6789:;<=> ?@87A῍67

defgd.|D$P #$#J:$ 0E

EF "GHªk" * ¨8F RKS89BC

Qz D

/* MPa '87AH@:  ()I- . Qz  > /* MPa- ./

BCJ > 6789KLIM'N . Qz N Qz-Or  -* MPa

Q

2**&

OPE>

"G RKS

T> Fig. . UV! >W ?aF

RKSXY"QZ)

! -.

Qz  "[

0>

XY

?` Swanson, +311 ; Fig. /F #!$t@>

(Lasaga,+32+ ; Lofgren, +32*) J:$ Y¨WRKS«'X

i*k" ?` Cash-man and Blundy, ,***F Hammer et al. (,***) -g¬v­® G mC£ #defgd.|D$#$#-LH

I¯°!"(Fig. 0a) uv2uJ±#$#>N\$U _" -LH#$#J:$K²?bF \] 6789 ^ : _"` ?6! 789 A#abAc#defgd.

ULtM. -u XYuv, #$#F #$#%$ h!"V>

uJ ;<! NO*k ³ ;<\$_" ij*k '" Ac A 678
9 B%!k` ?Fig. . BCJF ) i 6789

>

l&

MPa 

.7no#d.

BCp'm ,*(_:

2U   ´' #$#J
:$ P` ;<t AcRK$ D Q Y Hammer et al. (+333)  ¬µ¶·uv +33+ ,¡¸®¹RºST»% )+"a KLK\]¼m

#$;d¼

377

jk+a#",l- !_ mn.*c:AdSLe*5   5 op ,l- qr

% /r*0sb# 50+,l- ;$f40t c %&# & $% vw")1+)#( l- cu#"x .*y =z7C W{2)+3
4/0
56|78 (,**+)  9}1 ,*** KLK{~:;  KA6dC KLK<{=#$!/r*:AdSL{>/0G"5 H" (Fig. 1) /+# 0+ =5 )+ <{= ?
Fig. /. Relationship between e#ective undercooling(»Te#) and crystallization rates (nucleation andgrowth). Modiﬁed from Couch et al. (,**-).
Arrows indicate increases in »Te# and rate.
Nucleation requires »Te# exceeds threshold.
With increase in »Te#, rates increase over small»Te# and decrease over large»Te#. This resultsfrom interplay between thermodynamic driving
force and kinetic barrier.

 " 

" Noguchi et al. (,**0)  @A 2-2  
BCD7 , -// MPa

EKLK

{>/0G"5 H" 0+ =KA7AT F,l-#$+^+iG/ 5 )+ G xH GI vw"5 H",ῌ.ῌ, -#./0

gAh' V CSDY

F`)+

%

`"@a J5 ( 55K    "N.*2 O#_4

 (Fig. 0b)3*  Geschwind and Rutherford (+33/)  !"  #$

 
 &

.* CSD L (Marsh, +322 +332) #$ M'( ) )*)!" )

CSD L K.* CSD

V+Y%

gAh' (CSD)  _  l7g

Ah G/ 2.#K4 MP  5

*+ Cashman (+33,) Gardner et al. (+332) Hammer5 + mm-et al. (+333 ,***) Nakada and Motomura (+333) 

S E#gAh (mm),-. /0"123 45  6

L7BQ+00t gAh R(S#£)!

789:9

;

< = 12 >? @

;

!":AB"gAh'
 (mm¡-)

Tp¤¥!"UD¦V_§+0 5 U§5 ( Q+0"

2#IJKLKM#NO"PQ

ARST"KLK U

F (mm¡.) 

D¦VW40t gAhX#

CD9EFG/05 H"   1!" 

F (mm¡.)gAh yK"_  © ª ¢CTL7B s«X# !"

AhY¬5 #$!§5 ( , KLK\]^_

'(_ *-@!4 KLK\] `" %a  #b#/0 c:AdSL e* $f (,ῌ.ῌ+) #$!c%& ) #

gAh'

(

(,ῌ.ῌ,) KLK\])i" *

5 (,ῌ.ῌ+ !"#$%&' ()*+,

1l

CSD

G- -

gAh'

 50- ¨T  (Fig. 2)

 V @WXY # Z[,ῌ. 

g
¢CT

F
g

¨T%V#­( Marsh (+322) ®¯® Z°/0"
CSD L±  5 $u*VF

CSD  ²

³`"# !"5 H4 " 5 op

³`

" 

[\.#'( G|GI



 

GI gAh#´]* uµ^

  " CSD L_`@²¶·³.*8ET V
CSD L#$*Ya ¸b²c  ¹ND#IJ%º L

& ' ( ¼378JKLMN,2789:5+

O6 Cashman, +33, ; Hammer, et al., +3330789P+Q

5:

R9

 STUV(TO+ 2 W JK X
Y Z$[L\ + ]HI(^)+_ Marsh (+322 +332)  `a?Ybc(XYd (batch crystallization) eP[, CSD fW[9Tgh[L\ JK0ij k (2 $bc '.

CSD (Fig. 2a)  2lImn ,2 oph+ (0qr H,lIstuvwR2):6**2stu(x op


-P+

(0q yze\{).m

CSD 0|}+\ JK0~Ih

X

Y0TO )^)
cD YA:TO)W :c9)W9(, fyo'A:)h+ CSD  ,

stuvwR2)W(()op 2P+ (0qr stuW /2$Wbc Fig. 2b  +,op 2 $)P+ (0 H2wh Af/2stu(x$)P+bc ; CSD z'm7OA9h5)W Fig. 2b  ,stu2( stuW
Fig. 0. Correlations between eruptive parameters andmicrolite textures. a) E#usive ﬂux and number
density (modiﬁed from Hammer et al., ,***), b)
Repose time and crystallinity (modiﬁed from Hammer
et al., +333).

 /0f CSD 2, (Fig. 2c) 
2CV(h[,9h"2  ,2Fh+Z$
9  stuW2 h ;stu
$W2 ,ῌ.ῌ+ a +¡¢t£¤^)l¥!A: ¦§ 8+\    

2(xh+ (2"¨©556 "

n n*expLῌGt
 n* :(+)

 L :  G :  t :   n  Ln n  L  !"  !" #$ Gt%+&n* '()

n*G

eP[stu$W2«hh)W¬\ CSD #/0fA:,2

`0­I $=R2,

2y` CSD (h[ Fig. 2a, b qe®)$)¯¢°¤2\% (Fig. 2c)*+ , J 
J

9Z$+=R2ªW(WO "

,
(,)

CSD 0W+opCV±²

CSD 0³´h+±²)5[W2 Armienti
et al., +33. ; Cashman, +33, ; Castro et al., ,**- ; Hammer - '. CSD /01 G 234 

et al., +333 ; Noguchi et al., ,**0 ; Sato, +33/ ; Suzuki et

56 t 2789:5 ;<9=) t 0>?

al., ,**0 ; µ¶N· ,**0 ; ¸¹º0@A:BCD >EFG(HI ( 

op(»fM+yz¬I5

%&Q,g¸XD¹EFE"#º»¼/23º379

Fig. 1. Magma plumbing system beneath Usu volcano, and ascent process (a) and textural evolution (b) of Usu,*** magma supplied from shallow reservoir. From Suzuki et al. (,**0). For reservoir at +* km depth,Tomiya and Miyagi (,**,) was referred. ¶ · indicates experimental result in Suzuki et al. (,**0).

 Fig. 2a, Fig. 2c  +  CSD +{

 (Cashman, +33, ; Castro et al., ,**- ; Hammer et|}!'$cd~X$X p

ODC ,**. Dh"[v1HXal., +333 ; Noguchi et al., ,**0 ; Sato, +33/ ; Suzuki et al.,OP/G#+9 X,**0) Marsh (+322 +332)  CSD  

!'$%~XX cd~X ! "#$ %&'X()*+ $,$ CSD 
%&

-



3456 7

./0 CSD 1

2-  +



89 (Eberl et al., ,**, ; Maalῌe-  & '1(!eX1

et al., +323) :;<= > +? @A)*@ * g%&}1)b* +8 Suzuki et al. (,**0)  BC ,*** DE

@S Geschwind and Rutherford (+33/) FE"#G1H IEJKLMJN CSD 1O

 N^ +32* D@EFEV*1

P@%&QRS +*TU$ VWX

*¡++@A0XX &¢'£EJKLYZ[\]J^ ]J^_ `@, *g%&})

+e Fig. 2b ,0X & '6!' 2X (Couch,+ \"#EFEf-1 $ ,**- ; Couch et al., ,**- ; Hammer and Rutherford, ,**, ;a"#bcd@A0(Fig. 1) *f-%&"#66Xg$

Martel and Schmidt, ,**-) 1¤|@¥¦b §~  $,$hEJKLMJN CSD cd1iS¨©¢#%&'-+%ªg  %&Qj$Xkeg X

m - 6 Fig. / /)!'$X )

Fig. 2b /)+ ]J^_`@a"#b%&Q«¬ G#­S+.®@-¯

cd CSD  Armienti et al. (+33.) lmn(Fig. /)  °//±5N0²"#ª(,**0)  m $  opqrsrh1

H %&'tu )vwx["#,gyz³*11"´0X%ªRS +8

Martel and Schmidt (,**-) @6µX/)

4 5 6 ¼

380' 0 TUVWX =W (Ps ;Table +)' Y Z[X=!< (Pf ;Table +)/ \]^_J`a=&bcdef

KLghPLi' jT 6k lC
C8 Mpqr< (Fig. 3, Table&mno+)/ st  u*dvw B*

>' defKr
6Fig. 38/ Fig. 3

&jT

u*dvw

B*>

xyz. ' =& { |y' =&>/ ' \] z}' SSD  MSD (Hammer andRutherford, ,**,  l ) >}~;%</SSD (single-step decompression)  ' Y *' C Y

A

> *< (Table +, Fig. +*)/ Q

MSD (multi-

step decompression)  ' YKa ' !

*< (Fig. +*)/ SSD

MZ

"y& 6HK#$8 ' MSD#%*< (Hammer and Rutherford, ,**,)/ #m4" SSD L MSD ?%D";!<
Hammer and Rutherford (,**,)  ' Y

M SSD  01/῍-,,/ MPaῌh 6Ys+& ; Table +8

u*' MSD gh

(Table +) L' MSD zWr SSD .

+., MPa ῌ h!</ $ " '{M(} &$L)y&%
 >*M(+=&/ # MSD MKa !< (Fig. +*)  ' $y&<4,#Mg-.=& z&/-ῌ, 
Fig. 2. Representative CSDs from groundmass of
volcanic ejecta. For interpretation, see text. a)
Linear CSD, b) Kinked CSDs, c) CSD withnegative slope at large sizes and positive slope atsmall sizes.

g#no
C 6+,jTeff8'  ¡¢£y&+¤ + {=W' gh¥t¦ §%!"¨&/ **gh / ' jTeff L 6k lC&m8 jT §©(}*r0ª «0*">> 6Couch et al. 6,**-8' jTeff MLN ¬Gy&L­®*" >&M8/





jTeff

(0,***'  (jP) ¯¨'  (jPῌjMPaῌh)  t) !"#$%&' ( ) *4' MSD ghz.Ka (Fig. +*) °
H&M' +, ' =&Ka

"+,- #$./-ῌ+ 

0
' Ptotal¨' ²² ³!<´#


1234' PH,O 5Ptotal 6PH,O
78 9:;%</ 0 1 'y/0

Ka ' noM|y&/ **, BC

 32Mµ;* 6 @MB*8' defK' FGH<IJK (Couch,PM,y&$LnoMt¶y&/ ·>¸H

=&> ?@ 1' 09:A
D3@*</ Ez!"rBy&L°H&/ $$ ±1<,**-) 4"'  (SiO,51*῍2* wt.ῌ ; Table +) L32µ;LN ' ¹M

MNO*"></  P;%</ Qnot¶ '  C& M>[º¨$L &/

R 6Martel and Schmidt 6,**-8  LP ; Table +8 S»32Mµ<4¨&/ 73*"°H9:W^^|})DNO& 

    !"#$%"&'()*+,-. /-012

381

Rutherford (,**,)  SSD NO8 luvw

kxyz'{|}? (Fig. ++)W-uv

8~%  ~ Fig. ++a 

*3 45 6789:;<=> +?,( Hammer and Rutherford ,**, 80. GH!,@3  ATeff AT BC-,DE,F-.

8w z'{~( (Fig. ++b.

GH8IJ

45 KLMNOPQR SSD,

Hammer and Rutherford (,**,)  MSD NO Ps 

Table + ; Fig. +*  GH89:;+#S

APῌAt i ; Table + 8+ z'{klw

T(.
-ῌ- ῐ῏῎ῌUVW- BC XYZ[8\]^_`ab_cSdef8g.
-ῌ-ῌ+ ῍ῒῑΐ῔hijkNOWlmn lhiNOWmn opq0r.
+ lst
Couch (,**-) Couch et al. (,**-) Hammer andFig. 3. Undercooling simply deﬁned by di#erence
between temperature (12*) and plagioclaseliquidus (AT in text). Modiﬁed from Hammer
and Rutherford (,**,).

Table +.

Fig. +*. Styles of decompression. Modiﬁed from
Couch et al. (,**-).

Conditions of experiments for decompression-induced crystallization in felsic system.

For detail of references, see text. Decompression rate (m/s) in MSD experiments in Couch (,**-) was calculated
assuming +** MPa is equivalent to ,./ km. Martel and Schmidt (,**-) tested the most variable decompression
rate in MSD experiments. When ﬁnal pressure was set at /* MPa, experimental time varied from 0 second to +/days.

º » ¢ ¼

382 Pf
mm ,, ,/ MPa+** MPa, /* MPa-**ῌ.**.*,*** mm , ; +,*** mm , / MPa

 Table .
, 


()*+,

!"#$%&'
Couch et al. (,**-)

MSD-./012 (Fig. +,) Martel and Schmidt(,**-)

3456789:;<=9>0'3?@5( Fe-Ti ABC6 DE() FG9DE HIJ;KLMNO() -P9QRS *-ῌ, T SSD -.

U'VW,>

-P9QRS'XFY90Y Z[\] + ,^$%&_B`PabORS-.

c]d Fig. / e(fgP h i9j, $%&'H*lmn

_BFko'j]9 ph' q[ 'rstu
Y9>0=vuwqF[ hxy-ῌ-ῌ, ῏ῒῐΐ$%&(z{-.e>GN(

'|j}[, N
Couch (,**-)

Couch et al. (,**-)

Rutherford (,**,) / SSD -.

Hammer and&4'

N (~P) ()0tuY9 FG9~P 
()XFY9;K'<=G[ (Fig. +-) Tab p  Q()  XF
Y90 (Fig. +-b)
- 
Couch et al. (,**-)MSD -./0

Dt()&4'DE*;K1

&4(

(Fig. +.) Couch (,**-)

9;K <=G[9>0p t&4't9e
NO() -P9QRS T SSD -.

*

U'VW, -P

9QRS'XFY90Y \]F[&4Fig. ++. Relationship between~T (simply deﬁned
by ~P) and plagioclase nucleation rate (I) in
SSD. a) and b) are modiﬁed from Hammer
and Rutherford (,**,) and Couch et al. (,**-),
respectively. In SSD, ~T is equal to~Te#(refer text). There exists time lag between
occurrence of undercooling and nucleation start.
In addition, nucleation stops when system approaches equilibrium and undercooling becomes
small (e.g. decrease in nucleation rate, as shownin b)). To evaluate e#ect of ~P, we thus needto compare samples held at ﬁnal pressure for thesame duration. a) shows data from samples
which were held for +02 hours at ﬁnal pressure,while b) shows incremental rates for various
durations (.ῌ/*. hours).

`ORS-. c]d Fig. / (fgP h

i9j_BFk
H*lmno'j]9
9>0= hxy, &4'

'rstuYk /l( &4DE'i-ῌ-ῌ- ῍῎ῌῑ
SSD -.

 /0 ¤¥ _B* (Hammer and Rutherford, ,**,) >¦J 
NDt() §?¨©Vªe«¬­«¬®¯# -P9QRS_B&4'_B9°±©e«(_B c]d Table , ; Vªe«(­«  ¡p Hlmno'1]9`¢c£6>p[9RS Dt &4pDE* Z[´J µ¶Fig. +/ ²³ NDt()-P9Q·¸ '78(9 µ¶·¸ (e«¹n³´X4µ3]^¶ ·¸¹º» HI:;G%m¼º

383

Fig. +,. Relationships among {T (simply deﬁned
by {P), decompression rate and plagioclase
nucleation rate (I) in MSD. Modiﬁed from
Couch et al. (,**-). Relative decompression
rate is known from the legend showing durationof experiment.



  
!   #$%&'()*+ ,- ./ 01"

2'345 678῍91:; <ῌ=> Lofgren,+32*? @A῎B! -ῌ. 



Hammer and Rutherford (,**,) 8 Table +CD

EF3:;!2G HICD@JK LM2
N@OPQ (Table ,) R4
STI

SSD, MSD :;G8

UVGW +X+HI(Y01/ῌ-,,/ MPaῌh <Z[? G\+ MSD :; 8

SSD+., MPaῌh (Table +)  ]^_` T)abc2

7d7e+PQ6@G 6 %fHI(gQX4 hij<:kB? l῍92mnjo

HIp8 qrP MSD :; hiXF38st 

Fig. +-. Relationship between {T (simply deﬁned
by {P) and plagioclase growth rate (Y and Gi)
in SSD. In SSD, {T is equal to{Te# (refertext). a) is modiﬁed from Hammer andRutherford (,**,) where average rates for +02
hours are shown. b) is modiﬁed from Couch(,**-) which includes incremental growth rates
for various durations (2ῌ/*. hours). For
growth rate estimation, ten largest microlites
were used (both a) and b)).

.u 01'67@A῎B  ,vw/x5HIp8 MSD

yhiQ (Table ,) 6 Y2

zN= Table , 2:kBl῍9 hij ({Teff) @Q n)e6&G

f|YX4}~+5@  %fG)*(@n)(2X={Teff 8

{Teff  <Pf+** /* MPa

QG3O <Fig. / Q8 Fig. ++a @ Fig. +-a<a?

MSD ; Table ,? :X4 )* +  n)8N>4<b?

)*    n)
{Teff hiQ : n)

+ j ,/   n)
<d?

{Teff h <Pf/ MPa

B01i Fig. +/ G

5 Suzuki et al. (,**0){Teff hiQ : X46& hi. <"?
<c?

? <a?ῌ<d?

SSD ; Table ,? : ./

MSD :;¡¢ !' 

0187PQQ {Teff G£fn)01:¤¥¦j73ῌ <{P §¨{Pῌ{t 01? 6 %fGJK8 {Teff©Qª«G

§y {P @{Pῌ{thij2­®+PQ

¬y{Teff<-ῌ,? JKX4{P {Pῌ{t 2¯¥G°¨5

G8 §y hijaXFPQ±²} ~  ¼

384

w8@ABC@D ! +** MPa 56p 7
xyU<  z8 +,9:!O==4*.  ,;{ +, 

|^}$~` ,*** <8<= (Suzuki et al., ,**0)* =l8
j$= (Couch et al., ,**- ; Geschwind and Rutherford, +33/)* =898>?@A) ]

Bw<





CD!EF

$!O=* #;{ GH O=*.ῌ+ 
Fig. +.. Relationship amongT (simply deﬁned by
P), decompression rate and plagioclase growthrate (Gm) in MSD. Modiﬁed from Couch et al.
(,**-). Legend indicates duration of experiment. Relative decompression rate is known
from the legend showing duration of experiment.

&I^}J>[@o0ZK JEF BL
898>

?aE



P

M!

0Z * !vt0ZN+,D (SSD, MSD) +,MOP<=^}! QR ^F898>
?OP 

Pῌt *; Fig. +a-,E* SP0

Z%$ TU Teff,ῌ. 

   P

= V@T%W8 X $ 

*P  !

#$%$&'( ) *"+, -./0
 !

(Fig. 3) 

,?cE 0ZNGG,Y1234 2 *K 898 D&&'( 5

6)$7 898':;<= '(
>

?bE ^}J &I G $=0Z? E $[¡J¢]&I£^

MN_4

@TP\&* << 898'

ZG

#

(Fig. +a-+)* t! $[!O BL?8@ABC@DE F<G $ 

 @TP\ ?cE  - `^}a¤$

HI $ JK7   L!O=   &I ¥¦ * !v

MN!!O=)(Suzuki, ,**+ ; Hammer,,**0)* Blundy and Cashman (,**/)  PQDRSQT+32* U"

VC0#$"W%&

X'YZ[>\ F<=]& ^(<=* = Suzuki (,**+)   "G ' 

&'(Jt""§¨To¬ :ª«"Dbc ©ª«"

@Dd­ e® ©2¬ !' "¯BL!^J!]

1r0{* j ῌD°±f)  "

gv'

 (Fokin et al., +333)

hi$ : P\²@T _<=* )*`+ab 0 ,c-d&I¥¦ * # &I^}J89

eU<=fg  hi. 8988j³ F Uk"« ^F

' (.** MPa) jk+** MPa l+,m/ n
$

?Fig. +0  An -oE* << +, '\K BL*$~` ,*** < - ´ -+ l898'mµnkop&! ?>8@ABC@D

898>u< "q¶rO 898 `s;<! ; Fig. +0E* +** MPa 0p +,t·p u`t·vw<= 3$+,q

= ?¸¹x ,**, ; Oshima and Ui, ,**-E* º ,ῌ.ῌ' "

 -./0

(Fig. 3)

$ ]1r (T) #  "2s% O=3$
898 "&

(Suzuki, ,**+)* t!&'( 4]<= uvj

,

=

y«"«µz@T%W£^O 898 M!

, 0Z%{  |j$= ?}~- ,**,E* »J
Table ,.

 

385

Textual change of run product with ﬁnal pressure and decompression rate.

Excerpt of Table . of Hammer and Rutherford (,**,). Results are from +02 hour experiments forboth SSD and MSD. Te# in table corresponds to T (simply deﬁned by P) in text.

Fig. +/. BSE images of decompression products in Suzuki et al. (,**0) where samples were decompressed from+,/ MPa to /* MPa. MSD and SSD show style of decompression (see Fig. +*). Numbers after MSD and
SSD indicate experimental time (hour). Phases are Fe-Ti Oxides (Ox), clinopyroxene (Cpx), plagioclase (Pl),glass and bubble in order of decreasing brightness. Most crystals are microlite. Crystals which existed before
decompression are labeled with pe (abbreviation of pre-existing). Plagioclase pe in MSD-+./ is fragmented.
Plagioclase microlites in SSD-,. are skeletal (for reason, see caption of Fig. -), while those in MSD products
are tabular and euhedral. Note systematic change in microlite number density with time in MSD run(increases from MSD-0* to MSD-0 and decreases to MSD-+./ ; also see text). Among all run products in
Suzuki et al. (,**0), SSD-,. best resembles ejecta (Fig. -) in terms of microlite. Actual magma wasdecompressed to +*ῌ/ MPa after crystallization was completed (Stage-, ; Fig. 1), so there exists textural
di#erence of bubbles between ejecta and SSD-,..

 M ¼386/* MPa 7']^6 SSD ,[QTT<

7$%J*6bc_ $k- MSD

/* MPa .'tERS.ῌ, 



'6, 34*$% ./01.
2 ' ,J*'UV2RQ% )TA
E J* /e0 )T+W6`

 Ae1  p /* MPa 7']^eS ,' An * SSD 7-2[(An./.0῍.3.+) 'w3@T SSD 77'4 (An...,῍/-.*) qTA6y A
5'F 7
Fig. +0. BSE image for plagioclase phenocryst(Pl-Ph) and groundmass (GMS) of a pumicesample from Futatsudake eruption at the middleof 0th century. Low-An rim records syneruptive
magma decompression from reservoir (.**MPa) to +** MPa (Suzuki, ,**+). Also noteno microlite in groundmass. Fr-Ph ; fragmented
phenocryst.

eyz8

L-]^7!" A

R ]^' L-T MSD T) M.N'677 ,./01.2'6nERS_ /* MPa 7']^e
88A7@ERS aA734*w

9-&{8ARQ -῍-῍+ ./0
1.2': w; n ./01.2 /*MPa 7'"'!" ]^' !

E'!"7¡8¢£ey8

Fig. +/ ' MSD ; Fig. / <=- ,J*e 



bc87 ]^6 +./ ]^9!7 

Fig. 1    !"'./01.2 Pw> [¤[E

# $%&'() %*+,-./01.2

 aA7]^6 +./ ]^PwTA6RS'34*5* 6 7

89:  ;< (Fig. 1)

=>+ ; Fig. 1 ?@A6

BC' DEF 7

6G$4*

./0HI'JKL

A'# SSD 7'¥ 6

qTw'?@ ae¦ /* 5 ,**+ + $%M.N'OP

MPa 7')*]^eS ]^./01.

QRES)T ,῍.῍+

2AB (vol. ῌ) +: '§¨RQ 

;<=>, 7$%&6?

@ERS' UV2'W'!" XY75'F8$%&'Z6[E! Q \

6`A6RS Fig. 1 ; Fig. +* ' SSD -E

(/* MPa)  +῍, #C .DE

4RQG$7']^6'

7[ES A'$F ,-G_Q©%ª./_7` aA7$%JK'bc7

;<=>+

01.2 (Fig. -) 6 MSD «¬p SSD 'deAES fg'h 

G_QAw<=-7`S !no Fig. +/;<=>+ 'l^+d,-'./01.2 CSD  M.Nm !no Fig. +* ' SSD  MSD 'Tpq­% Fig. 2c y8#E®'¯H6G_Q6

RS'R 6RQETrs6`S 8Etu:"7 SSD '°G_QAw<=-7

ij'$kRQ
'v . #^tP?@)Tw'' vx'F `S Fig. +/ ' SSD-,.  './01.2

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387

Fig. +1. Seismic activity and ground deformation before and just after the -+ March eruption in Usu volcano(modiﬁed from Oshima and Ui, ,**-). (B) temporal change in base line distance (for location, see (C)), (E)hypocenter distribution in EW cross section, (F) temporal variation in hypocenter depth. Three phases in the
precursory seismicity (I-III), proposed in Oshima and Ui (,**-), are shown with the vertical dotted lines in(B) and (F).

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W stg ,+ ¬­COE ®¯,°±r²³ ´)Iµ*¶·qῌ ῑ ῐ ῍Armienti, P., Pareschi, M. T., Innocenti, F. and Pompilio,
M. (+33.) E#ects of magma storage and ascent on the
kinetics of crystal growth¸The case of the +33+ῌ3- Mt.
Etna eruption. Contrib. Mineral. Petrol., ++/, .*,ῌ.+..
Blundy, J. and Cashman, K. (,**+) Ascent-driven
crystallisation of dacite magmas at Mount St. Helens,+32*ῌ+320. Contrib. Mineral. Petrol., +.*, 0-+ῌ0/*.
Blundy, J. and Cashman, K. (,**/) Rapid decompressiondriven crystallization recorded by melt inclusions
from Mount St. Helens volcano. Geology, --, 13-ῌ130.
Cashman, K. V. (+33,) Groundmass crystallization of
Mount St. Helens dacite, +32*ῌ+320 : a tool for interpreting shallow magmatic processes. Contrib. Mineral.
Petrol., +*3, .-+ῌ..3.
Cashman, K. V. and Blundy, J. D. (,***) Degassing andcrystallization of ascending andesite and dacite. Philos.
Trans. R. Soc. Lond. A, -/2, +.21ῌ+/+-.
Cashman, K. V., Sturtevant, P., Papale, P. and Navon, O.

389(,***) Magmatic fragmentation. In Encyclopedia ofVolcanoes (Sigurdsson, H. ed), .,+ῌ.-*. Academic Press,
San Diego.
Cashman K. V. (,**.) Volatile controls on magma ascentand degassing. American Geophysical Union Monograph,+/*, +*3ῌ+,..
Castro, J. M., Cashman, K. V. and Manga, M. (,**-) A
technique for measuring -D crystal-size distributions ofprismatic microlites in obsidian. Amer. Mineral., 22, +,-*ῌ
+,.*.
Couch, S. (,**-) Experimental investigation of crystallization kinetics in a haplogranite system. Amer. Mineral.,
22, +.1+ῌ+.2/.
Couch, S., Sparks, R. S. J. and Carroll, M. R. (,**-) The
kinetics of degassing-induced crystallization at Soufrie◊reHills volcano, Montserrat. J. Petrol., .., +.11ῌ+/*,.
Dowty, E. (+32*) Crystal growth and nucleation theory
and the numerical simulation of igneous crystallization.
In Physics of Magmatic Processes (Hargraves, R. B. ed),.+3ῌ.2/. Princeton University Press, Princeton, New
Jersey.
Ebadi, A. and Johannes, W. (+33+) Beginning of melting
and composition of ﬁrst melts in the system Qz-AbOr-H,O-CO,. Contrib. Mineral. Petrol., +*0, ,20ῌ,3/.
Eberl, D. D., Kile, D. E. and Drits, V. A.(,**,) On geological interpretations of crystal size distributions : constantvs. proportionate growth. Amer. Mineral., 21, +,-/ῌ
+,.+.
Eichelberger, J. C. (+33/) Silicic volcanism : ascent of viscous magmas from crustal reservoirs. Annu. Rev. Earth
Planet. Sci., ,-, .+ῌ0-.
Fokin, V. M., Potapov, O. V., Chinaglia, C.R. and Zanotto,
E. D. (+333) The e#ect of pre-existing crystals on the
crystallization kinetics of a soda-lime-silica glass : thecourtyard phenomenon. J. Non Cryst. Solids, ,/2, +2*ῌ+20.
Gardner, C. A., Cashman, K. V. and Neal, C. A. (+332)
Tephra-fall deposits from the +33, eruption of Crater
Peak, Alaska : implications of clast textures for eruptive
processes. Bull. Volcanol., /3, /-1ῌ///.
Gardner, J. E. and Denis, M. H. (,**.) Heterogeneous
bubble nucleation on Fe-Ti oxide crystals in high-silica
rhyolitic melts. Geochim. Cosmochim. Acta, 02, -/21ῌ-/31.
Geschwind, C. H. and Rutherford, M. J. (+33/) Crystallization of microlites during magma ascent : the ﬂuid mechanics of recent eruptions at Mount St. Helens. Bull.
Volcanol., /1, -/0ῌ-1*.
Hammer, J. E. (,**0) Interpreting Inclusive Evidence.
Nature, .-3, ,0ῌ,1.
Hammer, J. E. and Rutherford, M. J. (,**,) An experimental study of the kinetics of decompression-induced
crystallization in silicic melt. J. Geophys. Res., +*1, +ῌ,..
Hammer, J. E., Cashman, K. V., Hoblitt, R. and Newman,
S. (+333) Degassing and microlite crystallization during
pre-climactic events of the +33+ eruption of Mt.
Pinatubo, Philippines. Bull. Volcanol., 0*, -//ῌ-2*.

390

p q r sHammer, J. E., Cashman, K. V. and Voight, B. (,***)
Magmatic processes revealed by textural and compositional trends in Merapi dome lavas. J. Volcanol.
Geotherm. Res., +**, +0/ῌ+3,.
Holtz, F., Pichavant, M., Barbey, P. and Johannes, W.
(+33,a) E#ects of H,O on liquidus phase relations in the
haplogranitic system at , and / kbar. Amer. Mineral., 11,+,,-ῌ+,.+.
Hurwitz, S. and Navon, O. (+33.) Bubble nucleation inrhyolite melts : experiments at high pressure, temperature, and water content. Earth Planet. Sci. Lett., +,,, ,01ῌ
,2*.
Jaupart, C. (+332) Gas loss from magma through conduit
walls during eruption. Geological Society, London, Special
Publications, +./, 1-ῌ3*.
Kirkpatrick, R. J. (+32+) Kinetics of crystallization in igneous rocks. Reviews in Mineral., 2 (Kinetics of Geochemical Processes), -,+ῌ-32.
Lasaga, A. C. (+32+) Implications of a concentrationdependent growth rate on the boundary layer crystalmelt model. Earth Planet. Sci. Lett., /0, .,3ῌ.-..
Lofgren, G. E. (+32*) Experimental studies of the dynamic
crystallization of silicate melts. In Physics of Magmatic
Processes (Hargraves, R. B. ed), .21ῌ//+. Princeton University Press, Princeton, New Jersey.
Luth, W. C., Jahns, R. H. and Tuttle, O. F. (+30.) The
granite system at pressures of . to +* kilobars. J.
Geophys. Res., 03, 1/3ῌ11-.
Maalῌe, S., Tumyr, O. and James, D. (+323) Population
density and zoning of olivine phenocrysts in tholeiites
from Kauai, Hawaii. Contrib. Mineral. Petrol., +*+, +10ῌ
+20.
Marsh, B. D. (+322) Crystal size distribution (CSD) inrocks and the kinetics and dynamics of crystallization I.
Theory. Contrib. Mineral. Petrol., 33, ,11ῌ,3+.
Marsh, B. D. (+332) On the interpretation of crystal size
distributions in magmatic systems. J. Petrol., -3, //-ῌ
/33.
Martel, C. and Schmidt, B. C. (,**-) Decompression experiments as an insight into ascent rates of silicic
magmas. Contrib. Mineral. Petrol., +.., -31ῌ.+/.
Mastin, L. G. and Ghiorso, M. S. (,***) A numerical program for steady-state ﬂow of magma-gas mixtures throughvertical eruptive conduits. USGS Open-File Report **ῌ
,*3.
Mourtada-Bonnefoi, C. C. and Laporte, D. (,**.) Kinetics
of bubble nucleation in a rhyolitic melt : an experimental
study of the e#ect of ascent rate. Earth Planet. Sci. Lett.,,+2, /,+ῌ/-1.
   ,**+
     ,***  ! : GPS "#$%&'()*+,- ./0)123 45*
6789: 3/: 33ῌ+*/.
Nakada, S. and Motomura, Y. (+333) Petrology of the+33+ῌ+33/ eruption at Unzen : e#usion pulsation andgroundmass crystallization. J. Volcanol. Geotherm. Res.,23, +1-ῌ+30.

Noguchi, S., Toramaru, A. and Shimano, T. (,**0) Crystallization of microlites and degassing during magma
ascent : constraints on the ﬂuid mechanical behavior ofmagma during the Tenjo Eruption on Kozu Island,
Japan. Bull. Volcanol., 02, .-,ῌ..3.
;<=>?@ABCD EFG HIJ
KLMNODPQRSTU ,**, ?VW GPS $%0) ,*** X*+,-3 : .1:/.1ῌ//1.
Oshima, H. and Ui, T. (,**-) The ,*** Eruption of Usu
Volcano. In Reports on volcanic activities and volcanological studies in Japan for the period from +333 to ,**,, ,,ῌ
-+. The volcanological society of Japan and national
committee for volcanology and chemistry of the earth’s
interior, science council of Japan.
Rutherford, M. J. and Hill, P. M. (+33-) Magma ascent
rates from amphibole breakdown : an experimental study
applied to the +32*ῌ+320 Mount St. Helens eruptions. J.
Geophys. Res., 32, +3001ῌ+302/.
Rutherford, M. J. and Gardner, J. E. (,***) Rates ofmagma ascent. In Encyclopedia of Volcanoes (Sigurdsson,
H. ed), ,*1ῌ,+2. Academic Press, San Diego.
Sato, H. (+33/) Textural di#erence between pahoehoe andaa lavas of Izu-Oshima volcano, JapanYan experimental
study on population density of plagioclaseY. J. Volcanol.
Geotherm. Res., 00, +*+ῌ++-.
Z[\] ^B_ `abc d e  Rf,**/ gh ,**. ijXkFlmno3
: /*: -+/ῌ--,.
Suzuki, Y. (,**+) Petrological study on magmatic process
in felsic magma eruption-especially on magma ascentdeduced from degassing, vesiculation, and crystallizationin the ejecta-. Doctor thesis, Univ. Tokyo, ,*3 p.
pqrsRf ,**+ tuvwx)yz{|}~X/Y ,*** :  yXY3 9: 10: ,/-ῌ,02.
pqrsRf ,**, z
:  ,*** Xtyz3 : .1: 01/ῌ022.
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. eruptionof Usu volcano, Japan. Bull. Volcanol., doi +*.+**1/s**../ῌ**0ῌ**2.ῌ-.
Swanson, S. E. (+311) Relation of nucleation and crystalgrowth rate to the development of granitic textures.
Amer. Mineral., 0,, 300ῌ312.
Swanson, S. E., Naney, M. T., Westrich, H. R. andEichelberger, J. C. (+323) Crystallization history of Obsidian dome, Inyo domes, California. Bull. Volcanol., /+,+0+ῌ+10.
 ,**- /. Xyz¡¢)£¤ : ¥W&¦§¨yz©ªX¦«3 ¬al­ ,**- W®¯°­±²³´µ: ,1.
¶·Q ,**,  ,***  - ¸ -+ ¬Xij3 : .1: 00-ῌ01-.
Toramaru, A. (,**+) A numerical experiment of crystalli-#$1234567!"!89:;<=>?@ABCDE:
zation for a binary eutectic system with application toigneous textures. J. Geophys. Res., +*0, .*-1ῌ.*0*.
,**0   ,**.  !"!#$%&'( ) /+) .3ῌ0+.

391

Tuttle, O. F. and Bowen, N. L. (+3/2) Origin of granite in
the light of experimental studies in the system NaAlSi-O2 KAlSi-O2-SiO,-H,O. Geol. Soc. Amer. Mem., 1., +/- p.
*+,- ./ 0