  /,  (,**1)
 ,  23ῌ+*-  

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

 

 

,**0  -  ,2  ,**0  +,  ,/ Fluorine and Chlorine Contents in the Products of the Large-Scale
Pyroclastic Activity of Aira Caldera
Minoru YOSHIDA and Mineharu OSHIMA
Fluorine (F) and chlorine (Cl) have been determined for the products of a series of large-scale pyroclastic
eruptions that produced the Aira caldera at the northern end of Kagoshima bay in southern Kyushu. It started
with a Plinian pumice eruption (Osumi pumice fall, 32 km-) followed by the Tsumaya pyroclastic ﬂow (+- km-).
After a short pose, a violent explosive eruption occurred to form the Ito pyroclastic ﬂow (,/* km-) accompaniedby the Aira-Tn ash fall (/* km-). Pumice blocks, pumice grains, no welding matrices and welded tu#s sampledfrom the deposits of the Osumi pumice fall, the Tsumaya pyroclastic ﬂow and the Ito pyroclastic ﬂow are analyzed.
Their F and Cl contents varied in the course of the eruptions. The Osumi pumice fall samples have uniform
F and Cl contents and show the highest average values among those deposits. Fluorine contents of the Itopyroclastic ﬂow samples are distinctly lower than the Osumi pumice samples in order of grain size : ﬁne-grained
matrices coarse-grained matrices pumice grains pumice blocks. The Tsumaya pyroclastic samples are divided into two groups according to their F contents. The lower-layer deposits show F contents nearly the sameas those of the Osumi pumices, while the higher-layer deposits near to the Ito samples. The variation of F contents from the Osumi pumices to the Ito pyroclastic deposits is thought to be caused by the change of distributionof F between silicate melt and aqueous phases before and after the ﬁrst Plinian eruption. The variation among
the Ito deposits can be explained by the reaction between gases and silicates after the eruption. Chlorine contents
in pumices and no welding matrices of both pyroclastic ﬂows show wide range, but the highest values are almost
the same as that of the Osumi pumices. Welded tu# samples show the lowest Cl contents and the highest F/Cl
ratio. These results can be explained by release of Cl after deposition of the ﬂows.
Key words : ﬂuorine, chlorine, Aira caldera, large-scale pyroclastic deposits, pumice fall deposit+ i jE!@A-89:Fkl>mnLopO&qrs

   !"#$%&'()*+

2(,7 tu +3/1 ; Aramaki and Yamasaki, +30- ,-./012 3!45*6789: ;9:&vjwx\

3!<=>?!@A*BC7DEFG*H>I JG,W s ~; +12-  Yoshida and Tsuchiya,! F Cl !DELyzO7N&{|}*%KLMNON&FPQRST>?*6IUV2(,,**. B6 ++*2  (Yoshida and Aoyagi, ,**.) !E

7 Yoshida, +30- ;  +31/ ; Yoshida, +33*W XY(-Z['p  vjwx\ ! F Cl L]^

;Z[\ ! F Cl !]^ Z[_*MN79:%'  E*673 j&'( h!

`@A!a*bcO7d!&ef27W g* h!#i@ALq'pW

+/,ῌ2//+  ; ,ῌ+,ῌ+ 
Faculty of Science, Tokyo Institute of Technology,
Ookayama ,ῌ+,ῌ+, Meguro-ku, Tokyo +/,ῌ2//+, Japan.
 ,1,ῌ*2,0  +ῌ/ῌ+0Present address. Mama +ῌ/ῌ+0, Ichikawa ,1,ῌ*2,0,Japan.

 --0ῌ*3,- V,p1  +/./ῌ.ῌ/*1
Present address. Oomagi +/./ῌ.ῌ/*1, Saitama --0ῌ
*3,-, Japan.
Corresponding author : Minoru YoshidaSG ¡_¢¼

90   


F Cl





    (+301)  ῌA  ! Cl " 



r

7  t  \][7  J6 7 E   32 km- 9
7& (Kobayashi et al., +32-)  4 u#$%&' ( )*&+

J &

 7v  w

Ddy !& ; z&,&-./ 012 3(,&-.

x

/ 4!2"5#! $6 7 {:p|@ J}1!&K

8% 6&9%7: ; '( <=>)?@ F Cl

*7+,:& @ $-7  ( ./! A0

 (+- km-)  DCp% J6 6p~g z& I6 " 12

 !z7

8%3BCD E #$*F2G:D

maki, +32.j& 4H 5+IJ6  7( +***

89:D&   ;K 7( + <8H&2 i +32- ; Ara-

 7(  ¡+  OO

D&  @ r>=.12 X'

L4MN ! =>O%?"0  J6 !

d 

@A0 APQBC:  DER%&F

%7 \¢

D&

7 ,d  7




 H2 ITJU 2V
67 1W KLM XN YOJZ[\][^%&FD& @ 4H _P `;; Na@Z[\][^ 2QX  ,/* km- (Ara-z!r Tn

maki, +32.)

;  (+301) (G SG75+

HIs /*

km- iG £ +310j 97& \¢  p¤¥¦§¨
7 t¡©2z ! ~ Ly7 9& i +32-jmª r

Rbc& S@d E ;e +TJUf! 1`Jgy ; E #$ 9P«





XN

7



s $6 L'gVWIh.





7 7

7

 -./p4

iYOJj k: F Cl lX27

{|&VD& $- 6 n.p J

 m;Y-./!@nZ #$7[\¡+, 7 h]^+OoJp9&@K2@

X2¬­6 7

7t^t6Dd9& i_ +33/j E 0q "0rs ?"0 i®£ +33*j D& 7  1qtu]vw/ ?"0%&¯xC2 °q 9&V t^t X2





J6

K + F Cl "  D F/Cl `OoJRx

6D&; $±

aV "0rs Cl " by F/Cl `:y "0z Cl -/!{|J

& 6c ?"0

H,O(})  Cl

eBaV 

+dtu]vw/

5#4!& Cl "f QBCH~!

(+301)

 H,O(})  F  ReBy 4!&F"ghi! ; ?"0

Aoyagi, ,**.)

++*2 8 (Yoshida and+12- 8n (Yoshida and Tsuchiya,,**.) !J6

F/Cl `G7mo

b@d @ L4 0q6n7XN `S7 y QBC H~8 E .p JK| 

J65+I J6 +

F/Cl `:pD&J67
D

9 `

7t^t Cp7@&7

67 & %} 7k]^`



J6 F/Cl ?jby !@Okj f-/ l m  : e   5 + Ix1 'J6 7&D&  +T kZ[\][^  

%& qZ ,- <8'r>=77s.,:!&  

,ῌ ῍

῎

XN .²J7³´gV%&;D& tV XD ;e X]^
k: &@4&;  µ¶%&
 7
8 , t¡  k ,,,*** 8 B.P. , ! 6aV E ( r Tn Isk ,· ,.,***,/,*** 8 B.P. Ly!  
8  ¸ ¹ !     = ¶ º  
,0,***,3,*** 8 B.P. !& iG £,**- ; » ,**,j?¶·¸°O¹K*+ºL j16¯» ¼»;
 
 

 (Fig. +)  

91STdC (PB)  ~2 /ῌ-* cm - v,  3)% /%4+ C,!"#$%&'(  $  )*+(+ C ' 3)- (Ito . PB-,) 8 g,-./012, 34 56 789 f H,O() F Cl ,-/, 5/0":2,;/ <=";  > ? Tn * mR6

@A B85C,DEF"12, G
HI%JEKL :1,MN012,;/ "7"; ?*+hiG lYSTd Z"]': /0 :1 ZAramaki, +32. ; 8s. +33*] <=9n1 F, Cl; 
OPQRST (Os ; PF)  UVW X':  ":8; HIn1<#8: > =>9 "

R;/Y ZC[\,  Os + ;/ Os -]#$g,ST%^_;/ ` (Os .) %ab

5/0 20/&%?  #$ghi ';/  (Fig. ,) Os +, Os . "c Os:  @:L%  ":7 9n12, !,, Os - dc-e1

A Z O¡%B:]

F/Cl

':

8

j1, ":¢:)*+ (Ito)  f #$ghijklY (C£ >01"¤89":  ¥DtE

STd% (C UV Os . ,%(F¦"§8¨E G©$ ;"ª¨%/":,

& OPQRST`  ;/ (Ito 2 ;CH«¬ ­I"Jª%®E,MN0

Fig. ,) 2,mR [n,`Rop'/;l2 *.1+ mm mR ZTs +  + mm mR] %": R":Y qV(rst):E';¯°±²³ L #$gC);/u@v *1+,w:

ZIto +, Ito ,, Ito - ;Ito , & l&R,` , C]  ZNW] , > ¢:´µ ,ῌ. mm ¯°±²³;/

O¡. ST"% handpicking ` X` -./Tx/ (Ito ., Ito/, Ito 0)  > )*+$gyAt

u@v! .W0z+,1

(Ito 1)  (Fig. -)
{U*+ ZTs ; #$ghi|]  }[(rst)
e1);/u@v`1+,w: Ito + R

ZTs + ;/ Ts .] ;/ (Fig. -)

Fig. +. Index map of sampling areas : +. the Kanoya
area, ,. the Kokubu-Krishima area.

Fig. ,. Sampling locations in the Kanoya area.
(Osumi pumice fall and Ito pyroclastic ﬂow)

L ;c<¼92Fig. -. Sampling locations in the Kokubu-Kirishima area. (Tsumaya and Ito pyroclastic ﬂows)

  (PG)





       ! " Ito 0, Ito 2 

#$%&'() *+&, sug21 /?0 1 C:

12c ug

2

,-+ ./01 2R34=b Philips

456+ (WT)  782 9: $¢a£¤& " H,O(¥)  ++*¦ ,.

23 (LF)
;
B=9

PW+.*. z X 52C wjl ¡<=9  456+>?@ A
 4?C

456+

DE2F1G  (+33/) ?H  I
 456+4J2K0) 456+ L M %NO$ P HQ=9
 RSFRTU VWXY ZC3
[\1§¨ h1©2

0  L? ] !^3_`ab=9 ,-" _cd +32, 2ef. 
.ῌ+6 772 FeO+**ῌ (FeOª) 2«C:1h¬: Table +Y­  Z8®/0:C1h
Aramaki, +32. ; 3¯°c±9 +33*  ²³´\ 0 4,-" *.1+ mm µ¶ Ito ,-   + Ito ,-, Ito - Ts - #$%&'( 

h1ijklm&2T Table + F)01h  *.-/ mm µ

jmno#῍pq(r$s%t& ug _' h1v¶I#$%&'(  C:²³´ (lq&`(wxyzz)& cL ,**/ ­  ·¸2¹ / *.-/῍*.1+ mm#Ng Tsuchiya et al. (+32/) {|}*~ 1 ug + 7u#$%&'( d#$%&'( ¸ºg  sug2 2, sug :

C?:G)0 / SiO, K,O ?@ Al,O-
CaO FeOª MgO ? C SiO, C:®f» ­

0 -:C1  sug?  P.

&'vcwxyz(){| *+, U} ~}?

93

Table +. Major chemical compositions of the deposits of the Aira pyroclastic eruption. MWeightῌ : normalized to+**ῌ on the water-free base.O
speciesOs +Os ,Os Os .
Ts Ts Ts Ts Ts Ts Ts Ito +Ito ,Ito ,-+
Ito ,-+
Ito ,-+
Ito ,-+
Ito ,-+
Ito ,-+
Ito ,-,
Ito ,-,
Ito ,-,
Ito ,-,
Ito ,-,
Ito ,-,
Ito Ito Ito Ito Ito Ito Ito Ito Ito .
Ito .
Ito /
Ito 0
Ito 1
Ito 1

size MmmO

SiO,

TiO,

Al,O-

FeO*

MnO

MgO

CaO

Na,O

K,O

P,O/

PF
1/.22
PF
10.*.
PF
1/.11
PF
1...*
PG-+
,-.
1/.*3
PG-,
,-.
1/.,1
NW
*.-/-*.1+
01.,0NW*.,/-*.-/
1*.+1
NW*.+.3-*.+11 1,.20
NW*.*0,-*.+.3 1-.23
NW
t*.*0,
1-.1+
PB
1,..1
PB
1/.++
PG
,-.
1-.00
NW
*.-/-*.1+** 1*.3+
NW*.,/-*.-/** 1..,/
NW*.+.3-*.+11 1/../NW*.*0,-*.+.3** 1/./2
NW
t*.*0,**
1..-2
PG
,-.
1/../
NW
*.-/-*.1+
1+.1/
NW*.,/-*.-/
1..3,
NW*.+11-*.,/
1/..,
NW*.*0,-*.+.3 10.*2
NW
t*.*0,
1..3.
PB
1/.01
PG-+
,-.
1/.-/
PG-,
,-.
1../3
NW
*.-/-*.1+
1+../
NW*.,/-*.-/
1-./.
NW*.+.3-*.+11 1..,2
NW*.*0,-*.+.3 1..1,
NW
t*.*0,
1,.1PB-+
1/./*PB-,
1..2PB
1/..*
PB
1..,2
WT-+
1-.-/
WT-1,.*-

*.+2
*.+3
*.,*
*.,,
*.,*.,*.-3
*..+
*..*
*.-+
*.-*
*.,.
*.+3
*.,.
*.-*.-+
*.-+
*.,.
*.,/
*.,+
*.,1
*.,3
*.-+
*.,0
*.,.
*.+3
*.,+
*.,*
*.,3
*.-+
*.-.
*.,1
*.,3
*.+3
*.,*
*.+3
*.,*
*.,0
*.,2

+-..+
+-.,/
+-...
+..-0
+-.3+-.01+1.-+/../
+..-1
+..,,
+..10
+0.+2
+-.30
+..30
+/..1
+-.2,
+-.-3
+-./,
+...+
+-.10
+/.,+-../
+-.+/
+-.*2
+..**
+-..+
+-.30
+../.
+/../
+..,1
+..*+
+..++
+/.2+-.02
+-.3,
+-.0.
+...0
+..00
+/..-

+.03
+.02
+.1,
+.31
+.31
+.30
-.11
-.1+
-.*3
,.0,
,.3+
,.*1
+.0+.3-.+,./2,.,,.*,./,
+.22
,.2*
,..*
,.-.
+.3/
,.-2
+.1+
+.2,
+.10
,.3/
,.1.
,.0/
,.-3
,.31
+./3
+.1/
+.1+.20
,.+2
,..2

*.*0
*.*0
*.*0
*.*1
*.*1
*.*0
*.++
*.+*
*.*2
*.*1
*.*1
*.*2
*.*0
*.*2
*.+*
*.*3
*.*1
*.*0
*.*0
*.*0
*.*2
*.*1
*.*1
*.*0
*.*1
*.*0
*.*0
*.*/
*.*2
*.*2
*.*1
*.*1
*.*1
*.*0
*.*1
*.*0
*.*1
*.*1
*.*2

*.,.
*.,,
*.,1
*.-2
*.,1
*.-+
+.,2
+.*3
*.1,
*..3
*...
*.,2
*.,.
*.-1
*.3,
*./1
*.-.
*.,2
*.-,
*.,.
*.11
*..3
*..*
*.,.
*.,1
*.,/
*.,/
*.,/
*.2,
*.0+
*..*.-,
*.-2
*.,/
*.,2
*.,3
*.,3
*./,
*./0

+.1*
+.02
+.12
+.33
+./0
+.1+
..+1
-.+,.,0
+.22
+.0+
,.*/
+.3.
+.3.
-.,0
+.33
+./+
+.-1
+.-,
+.//
-.+/
+.31
+.01
+..*
+.-0
+.1/
+./,
+.22
-.+2
,.+1
+.0+
+..+.-+
+.3,
+.3,
+.21
+.3+
,./,.0+-.0-.01-.0-.0*-./-.0,
-.13
-./3
-.-2
-..2
-.+*
-.1.
-.1.
-.0/
-.10
-./.
-..2
-./,
-.-.
-.0.
-.13
-./1
-./1
-./3
-.-3
-./-./0-.0-.1*
-./0
-..2
-..*
-.+3
-.0*
-.01
-..-.12
-.1+
-.2,

-.+1
-.+2
-.*3
,.32
-.-,
-.++.2,.,3
,.11
-.**
-.*.
,.20
-.+*
-.+,.*0
,.2+
-.+1
-.-0
-.-/
-.+1
,.+*
,.2*
-.*.
-.,3
-.,2
-.-3
-.,.
-.*1
,.*,
,.01
-.*3
-.,.
-.+0
-.+1
-.-.
-.-/
-.+,.01
,.03

*.*.
*.*.
*.*.
*.*.
*.*.
*.*.
*.*2
*.*0
*.*/
*.*/
*.*0
*.*.
*.*.
*.*.
*.*0
*.*/
*.*.
*.*/
*.*1
*.*.
*.*0
*.*.
*.*.
*.*/
*.*1
*.*.
*.**.*.
*.*/
*.*.
*.*.
*.*.
*.*1
*.*.
*.*.
*.*.
*.*,
*.*/
*.*-

* Calculated total Fe as FeO.
** These samples are not analyzed for F, Cl and H,O MuO .

  1,ῌ 
!"#$ (+33*)  *.-/῍*.1+ mm

H  IJ K2L MNO %PQ RSTUV Aramaki (+32.) 

WX% *.-/ mm  YZ[\

% &'()*+,-

]^%AB_ _` Ts - NW a; *.,/῍*.-/./ 0123456 7898:;

mm

2< 0=>2?@  7 .

_ ghijk, lmn l[4 SiO,

/56?@; %AB %7 CD E;FGZo

pq99:;bcdefJrmnsa;¦§ -Qb.¼

94

Table ,a. F, Cl and H,O(H) contents of the samples of the Osumi pumice fall.

  *.+,/῍*.,/ mm  *.*0, mm    *.1+ mm J   !"#$% & '

# de]v*4m1 L

G
C 5 v* =>?"fg 7w

()* +,)- ./ 012 3

H,O(H) : Cl  H, O(H) : F*45%6 !"#$789:7;<#

 J Cl *9:B7m1*b qb$7  !"7=>?".  @A

 +33/t

B CD#EFG7.ῌ, 
F, Cl, H,O(H)IJK

Table ,a, ,b, ,c LGIM NO P: .  .** mgQgH+

F Cl#R+* mgQgH+ S:T#UVWXR-ῌ YO#



$7
.ῌ,ῌ+

H,O( ) 

Z[ I\  H,O(H) * ,ῌ T)7])^_ `a ) ; b * *./ῌ T

H,O(H).c#%

*.*0, mm 

a<:j# B Uy|} w S JKH,O(H) : Cl # rH*.+10 q~O : /.t # /ῌe# )Uy) B de7 Cl

 SiO,, Na,O {B()l Z[ \ # S
fg#7i H,O(H) : F AB r*./++ q~O :/.t # +ῌ) Uy* w<:7 F

B

;<E7 5

"H,O(H)  F

!AUy<l Ky| LG #)l 

O #x') 89:7 de O*,;Y45%6 o F   u¡$¢% £U£¤¥:7 q¦§ +31/ ; Yoshida,;<+33*t * 5 ¨%O ,;*45%6 5!"% H,O(H) .

*kl de m1 LnB7
oP p<*L qAramaki and Lipman, +30/ ; p
G7wH,O(H)  Na,O  SiO,$¢AB &{7* 5 JK;< de7 F

Qrs+300tu de] Na,O, SiO,h J!" i\





h

C'd

e fg h G7 *$7  J


Uy

v
x

U

.ῌ,ῌ,

v w<:)

F, Cl  ©&ª'«¬(JF῍Cl 3­  Fig. . LG ]® 2A¯¯°)

y z{H,O(H) : Na,O #Uy|} (r) H*./.*±2 L !"²³ qt

q~O : --t # +ῌJ\) Uy LG

SiO, AB #{] J

#2

I

)a ´B)# *.-/

mm T - .µ !" qt)a*.-/ mm T  !" <;

5:< \  ¶* j  !"{B

SiO, . * B 5 3de fg

Cl *() 5: 2 5·#{ ¸5:<G7w 5:<\ S

JK

H,O(H) : SiO, # rH*..*1 q~O : ,3t # /ῌ) Uy LG T JK H,O(H) !"+¹*l.o:B7º ]E#»#7* F AB 5:<  !"j  !" x@ w<:P 5 ,n/RWXa!. &'95

Table ,b. F, Cl and H,O() contents of the samples of the Tsumaya pyroclastic ﬂow.





jkl F &'7 mnop^qrs` 

!"#$% Cl &

 t tua+tv)! waxdy*z-#'()* + ,#-./0123$%456789:;+<7!, =>?@;
AB#! CD7 ,#- E
FGHI*- JKL>45MN!
,O- PQ?7- RST%UVWXYZ!+) RST% F &' UVWXY{kl|}7 &~ cdefg /ῌ &~[+ +ῌ ]  +ῌ &~ [R

 [\] ^_? F &'` *.+ῌ ] `* !
,) UVWXYcd7

* !, 6abcdefg [UV]  Cl &'*h\ ( *.*0, mm) i, !

mm) 

\

0

0\ (*.*0,῍*.1+! ,,  /ῌ &

[\ ]^<_`a96
Table ,c.

F, Cl and H,O(Z) contents of the samples of the Ito pyroclastic ﬂow.

  +ῌ     ! +*ῌ "#$%&%'( +ῌ )*?@ ABCD E ! +*ῌ 4F  0

1 (Ts -, Ts .)  GH-./ IJKL  
MN <=>2?@'( +ῌO# 

-) +,-./ 01 21 34# F 56 (P *.*0, mm)  Q (*.*0,῍*.1+

7  21 (Ts +, Ts ,)  89:;# <=>2mm) ?@%R9O#( STUT%VWXY¡¢£kfI¤¥¦t §¨}© ª©12
Table ,c.

 

   !"#$

Continued.

Ut Tuvw7x  @A 8yU z
{|A%&'*%&'()* +&,- ./0 F 1234567 89:./,;<=)0>97

   >?
+)}k~,1 !X,i

P5Pfghi Cl 12 5?@AB$C F, Cl DEF GHI'ab|)0 /ῌ tq_7_  

K$LMN +3/1b ; Iwasaki et al., +302 ; Yoshi- =) 6^ ~J,-da et al., +31+O 8P:

GQRS

t TU

 /῍+*ῌ 7x  89:yU KO 

0VWA !X3456 KCl YZ0O ,;<=Ar ~

 Fig. . -=) C*[$\ ]=^ F 12_`ab Cl 12() Fig. . ,c =  +*ῌ  < 345:!",)  !7 ~#$,;) ` d_Q345 (*.*0,῍*.1+ mm)  ~ ( *.*0, mm)

8e  fghijklmno^ RS

tq0 /ῌ 7_ @A ~Qdf  Nab p90jklmP(*.*0,῍*.1+ mm) tq +*ῌ 7_

qfr^sRSQ,c  t T

 KO ./,;<

 /ῌ 7_^ 

°± ²³A´µ¶98ªFig. .. F-Clinsol. variation patterns for the samples of the Aira pyroclastic eruptions : ¦ Osumi pumice fall, § Ito,pumice block, ¨ Ito, pumice grain (,῍. mm), © Tsumaya, pumice grain (,῍. mm), upper layer, « Ito, nowelding matrix, coarse-grained fractions (*.*0,῍*.1+ mm), ¬ Ito, no welding matrix, ﬁne-grained fraction (­*.*0, mm), ® Tsumaya, no welding matrix, lower layer, © Tsumaya, no welding matrix, upper layer, ¯ Itowelded tu#. Samples whose symbols are parenthesized have main chemical compositions di#erent from theothers.





+*ῌ



@h yHz Cl {|5}T~ ;JnoW#X )YZ?, -) 

Cl   !"# 

+*ῌ.) $%&'( )*+,
+ῌ 01234

CDEF Cl  5 )?@K , =2I GHI rst01Zw2x `a`Od Cl )[- !"./0\ H,O, 5 S ;KJ:; 

Cl 56

CDEFJrst# =2I i.ῌ,ῌ-  F, Cl 

Jjkx T0<5~;Jmo 

789:;0< =>?@:;ABCDEF



GHI5 F, Cl JK=AILM:
 TTJ

and Aoyagi (,**.) UV:;?^:

NOPQ5RS

Yoshida and Tsuchiya (,**.) Yoshida

W#XYZ[0\Y]=>?@:;CDEFJ_ [1 `a`5b?cde fgS

?@h

F, Cl

5iJjkle TJLMmJno T
p: q$%rstL ,)EFu EFv

Cl  NOPQ5 owAcx

?

Tp:

F 

>?@t./

ABCDEF h?@t6x~ o TZw+) ?@h 

 F 5{:; ,) ?@7 `a` F  5~ ;  w 
 Cl 5=K Cl LMmKCDEFJkF 5Zw

ILMm ¡¢£¤¥ (Yoshida, +30- ; Yoshida, +33*)8µ¶·¸;¹v9:ºW,r»¼w sw" F  Cl      +)   ,)   ,ῌ+)  qrs, Cl /$D(*6 Shinohara et al. (+323)  ,., kbar  B 

! F "

99

1H, Cl /$DQ7qrsH, Cl /$#$! , %&'&() * F &'&+ 

D RS P{  X  5CD#7YS
Z X  7[S# 6

 F  &'&(,! -./ 0S v CD p 5 #7

12345 6#76   

qrsH, Cl /$ = 1**ῌ+*** mgRg+  0

5 89:9 ;< 1 \;\v  6]g(=>?@+A6 B = C>

^ Webster (,**.)  sBH t!7qrs7

D(  E +32- ; Aramaki, +32. 6. F

FGHW ^ F Cl /$CD~T#! ( F "(A6 #_

G  H. , %&'&()!I  ,! . /J*" F (-.qrsH,/ZV!c

MN"/O. #PQ R E (+33*)

 W7B18GH, F (5  'VKL

&'&S$ R%F& T; S$U'(V *W&'&)5XYV!

`a(/ IuJKvB1H qrs7F
G

@ F 'W

( 6. 8G#A 79]1bB  9

MN"(*+(  V
 &'&), F (-./ZV!

]1csd bQbB >(MN QR-.[01#\27 3@]4^_459;e +312 ; White, +3/1 6bBf, F /$,ῌ,)W &'&)-. Cl ^_ H,O (/ZV Cl g!  `a657b89D(V 9]18G F "!( 6? F W= C>D(:c 6  i

5! 5 3@]4R459 89:
9  &'&);V &'&1; S$R,ῌ-) Z White, +3/1 ; h +32/V=>  ;`a6,e &'&), qrs7FG, F "(D! -.MN

%F(5 H d ef<g"(/ T* &'&) 6. D(A6F -.h/Z(A  =76   ^5 5j ( ;`( i<g Cl (/ZV  j5k -a6( k, A +/. #lc6 m 7

.l>(A 89:9&'&S$R %

¡n[0   ,ῌ,) M¢ &'F Aramaki (+31+) m?R@ (+33.)  11*ῌ&)S$R %F t!7B1H( LIu

12*n A , kbar BCD! V #PQR

8G5xGwGt!£uv6 #¤

E (+33*)  12*o,*n -ῌ/ kbarpE! 9o&'&),B1H( LIu8G ¥ 6/!F qrs7FG t  ¦5xG(t!7wGJK/ p

!7B1H IuJKv %wG x§!. 6 F "Gt!/ LIu8GH

 Shinohara etH, 'V F (Z 7  B1
 qrsH,/$(al.(+323)  8MbvNOyqrs7FG6   ¨©ª«¬­9 ®,

B1H@ Cl  '# 2+*n, *.0ῌ0.* kbar  \2-¯!a6 F "! i23 ,., kbar z- B1H, Cl /$$! MN

P{Q qrs7FGH, Cl /$(RSP{ B1H LIu8G*H MN! 6Q i/$v\#q

89:9e 970%#$!&'& ;°5!

. #PQ R E ,., kbar z B1H, Cl /$(/|$#(+33*) MNdN `a6,e&'&)

}N  qrs, Cl /$* CD~T ?@rA +/. #±.6   qr#76 5 B1H xRw H(!I7 

sHGE(²!  B1HlcGE(5 ! 6F 89:9&'&)F

P{7s/ 6D B1H tcv   4U^H F&V$ #LIu8G/  %Z#u wG

PQRE +33* #MN  &'&), q³xG [01( J!    wG³x

rsHW Cl CD~T(A![01G ^i   /!  xG´g(/7 &'&), Cl -.hW(A

P{7 IuJKvwG J! LIu8G

l> 'H9

100

 F 

2**



   F 
 (Iwasaki et al., +30, ; Yoshida, +33*)
   iJpJ 7$Fh

Aramaki, +32.-

q J7 Cl rRs 1/ F  !" F #$%& Cl 

RY +J%t# -  @eY
 n iJPQRY + iJ ' ()* +HCl NaCl ,&Vu# - Bvu.w R. *- .. &/ 0*

BC J7mr x.9 ?

 1 2 +3-  45

Y @eYr 'y9PQ Ito!"*! "6#7$/89 :+  Ito 0 z +/

$;<;:=;<;. "6>?.&@A|}@- e~@~ w

BC%*  &2'(%$5R ,  /  +  wR Ito +  Ito

DE >F) .&GA

0 ¡

4 (% F .. (%=~£H

RY)*& {¢.n iJl.]

3*ῌ+** m ¤pw2

!"  F H*4

¡F* R. pPQR~@

7 +I +,-.J- KLMNOPe¥¦FT.,$.9) v¥¦TF§

 F /01*23.9 7 4Q R

Z.9

STU1V5 16 W7X* 89©FY: F ;4<Z

 :ex ¨¨*fC"h Clinsol.  /** mg'gw+ :e

Table ,c .

+[='5 +3/1a ; \> +3/2 ; ?@'5 ,**.- 4A

PQ  Ito + Xª Ito , .w R*.&

]R BCB;^_`M *.-/ mm :@KLMNOR @M Ito 0 PQ {P DE/0 Cl  F 5KL Clinsol. F« R

0** mg'gw+ :@fI¬^FWy$

Ito +MNOPabF * 7.;4R

 Ito 0  abz Clinsol.  $$5 23.9 23* ,ῌ,) .G  ­ fI+ ;^_`MI+r* ^R ,ῌ,) . HcdefI F  g;,ῌ-) .

®<Z R¯;^_`M+ +iJ

4A]R`Fhn- Clinsol. 

F #Rh g;<; F j

&¡<Z R Ito 2  )*:@ k*@ l> +KL, ; Tmn

0** mg'gw+ :@ Clinsol. F«<; Rh#

?M Yoshida et al., +31+ Qo-  NOp[ F F* RBC q+,2 PQrstR>+uS

#TUvV A- : -*, mg'gw+x Wy:@BCF°±D eM~ Cl m
:

#

F)

,-MHcdefIu Cl 

&m *

$5 HcdefI (,1*ῌ--* mg'gw+)  F g;iJpJ J l.$ab>?²³

iJ +z{ iJ Ts

R*$ ¡l.=´"6,<;  R$*+, , FX0 HM|+/* mg'gw+-  F # R

h $µ eMa¶4G0

$YZE[} z{CB0* 2 LB

iJ\~(%] HcdefIab^ F F)$ Hcd

E/ XªefIF_`

 l.~D ·(¸ (Ara- z{R;<;(%@M/aiJ(%\%4R*h :@Fb$ cdJ  F  7

maki, +32.) %8}RhA F)$*.&GA? eM l.$,$RZ ¹

e.f*gh ,ῌ-) /0i4h s ³Tº»$Fjk023.9 z{ iJJR +o +32-- w.ῌ,ῌ. 

Cl



Wy(%u0 pJ H´]J

.ῌ,ῌ- .Q RA BCB iJl.] Cl 4R= l.]. RFh

LH90 (%= Cl m8R e-.¶¼C4R Ito 2 (%=m H90E J7

 5~t HcdefI@Wy0ml.=m n iJ HM ?

X ¶4}R

rKm`^`h +o +32- ;fI+ I+;^_`M.D® +

fI¬

eK»TF O²?@¼}ALC'³ x³& 

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

"12 Table - 3 F/Cl 4 ..,1 )/0 Cl 5675 8,,9 :6;2 !"< ,-.. =>"< +1.2

' A*! +ῌ()

! 8,Tf  mnHo%&%0+ F, Cl p28+   ! +33/^l A*! ) *C F & 2 .ῌ,ῌ/  F, Cl 101

 #?@$%&/,4]   

 qj%&%/+ F ?@$r (Fuge, +31. ; Koritnig, +31,) F Ms Cl tP2iW

AU D, ^_W Xj%k& )+ u JJ"1v

2

@Tf BC)8, D,E* +,- ; FGHI. Yoshida et al., +31+ JK  /-I0?1% +,2 0+2,

/

eK?@L?LC'W F, Cl 2/ \lw

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V! +ῌ  B() WX' , AU"#$% I0?1%4Y+! DZ C() Cl E ( F/Cl  [U"12+

 z{| F,

L?2!, /,k <I {2 u( Q;$h)  hhf;l;g* F, Cl  vw`xW) *CM;&D +,i :, ,\/  4]Y #?@$%&'LC/, 5qX ,Oo,{F  "FGH GH 8,C' ,d

^_  I`?@$ "#$%7E

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 F/Cl  ,.1῍,.2 Table - /,!4Y

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4Y+!

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h+

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[() 

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?@$%&'0+ e~R 9¢(A¨©ª)8,

vw`xYyazb/ 0**῍1**n Cl.
F R(cd,9 E* +31/ ; Yoshida, +33*  e0 F {|' /}/} fg/+5
 (Weyl, +3/*)~' AU vw`x fh, 0 F, Cl 2/, «]«. ¬ ¬ 

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, j«g%X«£¤)  R(±v ­B 2

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*D ,9Tf 
.ῌ,ῌ0



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102
Table -.

F, Cl contents of welded tu# samples taken from several large-scale pyroclastic ﬂows in Japan.

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DE6FGHIJ <HK Lῌ ῏ ῎ ῍
MNOP (+3/1)Pyroclastic ﬂow QR!  + .1ῌ/1.
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]%¼w¸ 0£@$M¶\2    (+300) Na,O   1, 03ῌ1-.
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K. and Zemann, J. eds.), +1-K-+ῌ+1-K-2, SpringerVerlag, Berlin.
 ! (+301) "#$%& ῎A '  +, +ῌ+*.
() *+,-. /01 (+3/1a) 2 ' 34567)89: ; -, <=>?@ABC +*+ῌ+*/.
+,-DE FGH (+3/1b)  <=> .+ ' () = 12,+01ῌ+.,.
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. / (+3/2) 2 ' 34567)89:
IJK L MN9:2OPQ'RST)U!= ; -- <=>
?@ABC 3-ῌ3/.
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V"WX#$ (+310) YZ[\QL]% Tn Q &^_` abL c> .0 --3ῌ-.1.
I
V"WX#$ (,**-) W' Qde()_` f*K +g0>2,? --0p.
hijk-lbmnop (+33.) )qrsr Ux L῍ SIMS t.9P/uvwe0
+33. >?yz0?@ABC p.++-.
{|k  X}~   1p  20(,**.) 3 _2 ' &R[\ g04 no. .1 B, 10/ῌ
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  (,**,) 5[\6 - 7 S>  .+ ,,/ῌ,-0.
 !89: (+32,) ;<)ZST) ()U103+ = >¡ Z / 7
¢ 2*p0)?k (+33/) 0£@$%&ST) ()U  +g¤¥0>0>¦A¤>c§¨ /,p.
0)?k©
B (,**/) >¡¢ (GSJ) ªC«¬D' ST) () E   /* ,.-ῌ,.0­X ®0FGH (+312)  ¯° c> .2 .+ῌ
/,.
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B (+31/) _ Jµ¶\ST)
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B (+32/) Lx , (.) ST)x L¹ => . /MºNO{P©
B '  30ῌ33 +g0>2,?
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