5 6 7 

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 +.  3 ῌ῍ῌ
+





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!"#+ $%&, '()*,+ +.  ,  . ,-.  +.  2  + ,-/0

Geochemistry of Fluids from Hot Springs, Mineral Springs,
Wells and Fumarolic Area in the Shimabara Peninsula,
Middle Western Kyushu, Japan
Shinji OHSAWA+, Kohei KAZAHAYA, and Masaya YASUHARA,+

Beppu Geothermal Research Laboratory, Kyoto University,
Geological Survey of Japan, AIST

Abstract
Water and gas samples from hot springs, mineral springs, wells and fumarolic area in
the Shimabara Peninsula, middle western Kyushu, were collected for chemical andisotopic analyses. Geochemical data analyses lead us to the following results. Hot springwater of acid SO. type in Unzen-Jigoku fumarolic area is derived from meteoric shallow
groundwater heated up to +/*1 by secondary steam originated from deep hydrothermal
water of about -**1. Thermal water of Cl type in Obama area, which is basically mixtureof seawater and shallow groundwater of meteoric origin, interacts with reservoir rock at
about ,**1. The thermal water in the reservoir is heated by steam of about -**1
containing magmatic He and CO,. Thermal waters of HCO- type in Shimabara and Harajo
areas are slightly heated groundwater of meteoric origin. However, it is detected thatmagmatic CO, is dissolved in the thermal waters. Both thermal waters from Mizuho andYue, which are classiﬁed chemically into Cl-HCO- mixed type and HCO- type, respectively, are likely to be non-volcanic formation waters. The accompanying methane gaseswith these waters have thermogenic and biogenic origins, respectively. Mineral water of
Cl type from Karako may be mixture of seawater and meteoric groundwater, and is not
a#ected by magmatic emanation. Mineral water of HCO- type from Karimizu in Obama
area is originated from meteoric water, but the accompanying gas with strong H, S smell
would be derived from the reservoir of the Obama thermal water2
51

¼

52

Key words : Shimabara Peninsula, Unzen Volcano, hot spring, mineral spring, hydrogeochemistry   
 : +ῌ ῏ ῍ ῐ ῎
%&'( )!"#$

*+,%-./012
$3 456789:;89<=>

6?@A6ῌ BCDEFGHIJ KLM NO
-.PQ(12$% )RS῍+T"UVZ[!

WXY12$3

 \]1 B^[ +,-/3
mJ KL0_% `a +33* :+33/ b  *K+`(_c6def8

B^[ +,.20 mJ

KL$ Bghῌij ,***J3 k_  lmnopFG%qr(ῌ"stY$uvwx%ya(
BFig. +J ῌzp#${|K}M~(\X Z
+** b , mm ῌ year 

K(12$"Y12$
B +32/J3 

\X(1M Y"e(10_6*+M *+, ῌ{K *:/** m  BZ2
K 3** mJ ῌ {K.
Z¡K , ¢£ +** m r#$ Bghῌij ,***J3 ¤H$¥¦ §+%¨XY$%
)YXPQ "(1ῌWXY12$ B© +321J3
ῌmª«  B¬­J l®  B¯°±²ῌ:¯³J ῌ??m´M

Fig3 + Sampling sites in the the Shimabara Peninsula. µ+ :Shimabara-kanko Hotel (hot spring water [well]), µ, :Shimabara-onsen (hot spring water [well]), µ- : Motoike(hot spring water [well]), µ. : Shinyama-onsen (mineralspring water [well]), ¶/ : Shinyu (hot spring water), ¶0 :Kojigoku (hot spring water), ·1 : Tanaka-so (boiling springwater and separated steam [well]), ·2 : Karimizu (mineralspring water and bubble gas), ·3 : Kunisaki-ryokan (hotspring water [well]), ¸+* : Karako-onsen center (mineralspring water [well]), ++ : Mizuho Sennen-no-yu (hot springwater and accompanying gas [well]), ¹+, : Yugyoku-onsen(hot spring water and accompanying gas [well]), º+- :Harajo-so (hot spring water [well]), º+. : Harajo Masagoῌ +/ : Obama harbor (seawater),(hot spring water [well]), »·+0, +1 : Seishichi-jigoku (fumarolic gas). Numbers correspond to those in Tables + and /3

/, ¼ ,**,

-9.-ῌA01»ab H, S 53   +31-   ! ῍"#$%&'( )*$+,- %./,01!2,3 ῍45 6
7 8 9:   ;   !<=>?@#$"ῌA!#B #B3 ! ῍$%&CD'EF G1'H0(IJKLM+$)K*!++
,NO -9.-%& A >?PKQ/R0ST01
2U 3 A3 /RVW 45%6XR VW ῌA76VW YZ,89[
Rῌ,K#$3%63$\$+VW ;@]:^_`3 Gabῌ;c1%< d# "efg .-=h3ῌA3M+$ G>
?,@i KQ3j@QA %kl BC3  /RVW 45%6XR A
76VWefgm< DB01EniF,GH?

I CO, , CH.

kl BC3 ,89 %.efg,Gm<opM+$Jq,ῌ ΐῐ῔ΐ῍῎ῒῌῑῒ῍῏῕KrL -9.-%&ῌA]UD'M\K= ῍$
 ENj@Q-9 Ys +31- ; +32. @  .-
tu>vcwxy,Oz{|P 1** m EQ#B3 MR3$Rῌ}!ῌS!~,E~%* T~,= H, S U

H-SO. V3!W3$j

K K/RX Y#$+ ^BENZ +* m+** m |>?@#$[ lZ +* Q \]] \ Na-Cl V3!

45/3$+ | y#3 A!s CO, , H, S Rῌ Y+K!3$+ ^3A_ENA  -9 [j+$Z +** m 
2** m `>?@ HCO- 3 -* K !a3@"$+ | HH$b +* m Y>?P!#B3 ,* YA3!a3 6 cded$+ Sy%!,!  fyghziPj.** m k }F A  ,3$l$+> K A!#B3!
+33*+33/ m/ (30@no3%.spKY4 ῍4   !< 5 67 9: 
hῌA#B!l$+ Ys +31- ; y5q +33- @   +8 r3 % l¡T¢῎d3£>?P¤   32 m #! a33s# 0t!+FuC )*= ^Bvwxyed$+ ¥¦gf    zm!   {|§}¨>?

P¤ 

 +,*// ml,{I /*  0* 

Na-Cl-HCO- V3!X~a! vw©ed$+ ª«t;H¬¦­ !< I®  I{¯°3±I  .0*.1* m P¤ l,3 -*Z  Na-HCO- 3!²¦³a!$ cded$+ 5A 5{´µ¶G-{I>?@#$"A ,,  Na-Cl-HCO- 30 · 67 67{367>b¸#B3 %3d3l,3$>?P¤
A3 ,+ !"! ^Bed$+K+ 9: \I{¹º´N}FW3$+=  G¨j+$ +** mZ +** m >?@

3

¼T

54

  -*   Na-HCO-      -** m  !"# $% -*  Ca,&  ' HCO- ( ) *  +, - - .  /  0 1234%5"67) *-ῌ ῎ῑ῍ῐ῏-ῌ+ ῎ῑ

8#9  1 : ;0  < =  > ? =@A BC +. D)EF# ;Fig. + " Table +A <G, *HEF# pH

I#  %C# < !" ;No. 1A   !JK#$ * LMNOP"%&(QR *  &'(ST4)*"+U(,4-V "&OP. &OP ;WXA EF BY*QZ &OP. [\]^_`ab]L/ ;=ῌc0 +303A Q  : * def"X\ghijgk1 *#WX9"#* < "lmD)J n !"&OP"2&WX ;PῌA
 >34"?oD)2&WX p0 5P ;qrsA D)
t65P ;, 9A EF# ;Fig. + " Table /A !"&OP"t65P,uv>34
2&WX  KOH ;/MA w'WXEF7x89EF# ;:ῌ;< ,**+A J=ῌ
m2&WX  y$zu{|>}~]?V  KOH ;/MA @{WXEF7x
# ;/AD ,***A p < !"&OP: *  yBC
V DE#Fx EF#-ῌ, ῐ῏-,+ 9
Na&, K&, Mg,&, Ca,&=/u{ Cl_, SO.,_

ICP G/u{.# HI ;FeA

MN`\]u{ Al-& 7- M\

MGY**C1 *.# HCO-_ )*  BCG J"#KLu{9C V ;..2 ¡¢*A HM£ ;DICA N££¤#*M£4H*

CO,;aqA Oz# Mb]L ;P¥QRS IM-+BA 9T#U£SMVQ¦ ;P¥QRS CE,-/A 1 * WX.Y/u{# DῌH " +2Oῌ+0O   J n §Z¥¨1 / U£SMV[©/uZ*# V-SMOW Xe]\# ;dD " d +2 OA ]*  J n ª+« ª*.+« 5HM£ ;DICA  +- Cῌ+, C   hXkgNSFx^M£wp+

Sr;OHA, _¬1Y ;` .*A SrCO- "#*ab&#- )M£L­#*G® CO, .
Cc@#*# +U(,4  V-PDB +U(¯°S#*de±\# ;d +-CA 
²±  +|9³I¤D) *.+« ´­"µf )  SO.;¶HSO._&SO.,_A  +2Oῌ+0O
  BaCl, _7*abY BaSO. ·\"¸¹º +,*** %#*G® CO, .Cc@#*# +»®4 BaS  Ag, S Oz#- Cu, O "¸ 2** %#*G® SO, D) SO.  -.Sῌ-,S  V +U(,4  J n
V-SMOW +U(" V-CDT +U(¯°S#*de±\# ;d +2 O- SO. " d -. SSO.A ²±  J n ª*.-« ª*.,« 5d /, ¼ #,**,&:[:>ῌtM,H»u55-,, 

 CO,, H, S, N,, CH., Ar, H,, He, O,    !ῌ' ()*+)

 ,**+&./ 0 H, O 12
Q #/ m& #"$% +332 ; #$% +332& 3  45678 C, H0  Ar 9:

FID =>?8

;<8*"

, -
0"  @ABῌC, Polapac  #+ ml& -DE / F, /*G H I- /Gῌmin JKL+/*G 3L=> M  N/,  ,῍ LOP KOH QRS

CO,  d +-C  T*

 H, S  Sῌ S $, H, O, U%V"

KOH RSQ%'&"-.

-,K" XY'LZ([ M)*"
V-CDT

!"#L

SO,  \]+"

^,$L_`"/0/L1""12

BaSO.  SiO, * V, O/ W" ^,-.,

N/, a*.,b LOP CH.  +-Cῌ#d -.S&

C $, 45678ῌ * /c+ ml XY2"Q,35+,

d #e+30G& L H, O * CO, fg" - 3**G  Cu, O 2" CH.  CO, 4h"
*."i

H, O jkl8me6<5no #e3*G& Lfg" - \]+

"

" 

^,-., V-PDB^,$L_`"/0/L1", a*.,b LOP pqT DῌH $* Oῌ O $, T* !"#L+2+0#d +-C&N/" V-SMOW 

r8mL1s" . 
.+  

>tTuvw Table + s" 5'x8k y6z-.{#Cl-HCO--SO. {& |d5" *}~ #Fig. ,A& 7> #No. ++&  Cl-HCO- WKLO

Pf   % +z.8PT\}*s 9H :>#No. +, ,, -, .& > #No. +-, +.& ;> #No. +,&  !<Tt #No. 2& , HCO- => #No. /, 0& , SO.  <> #No. 1, 3& *>$> #No. +*&  Cl LOP }'H =>?'%@AP #Table +& 3  

H, S BH'C

PTtT,@AP #pH/.1& D>LOP 2% H, S  PE*.,FL'  T\*", HCO- * P
y6z-.%'P* GH(T #H()I*P > Na-Cl (TJKLL,}  ¡}*P& H1¢M£N@OP, <>*>$>* }*PLO~ I}L (TuO¤¥PQ.R PSTLUP Na-K- ῎ ῌ῍ { #Giggenbach, +322& ¦ GH(T£N@§VZ¨#Fig. ,B& HCO-  SO. >ῌtT #No. +c0, 2, +-, +.& * ! <> #No. 1, 3&*>$> #No. +*& H' O¤¥P%'%
d5

0 «¬* YTGH(TI L, }*s" P ­"

W.©TXªd5
I ®

W.©T #immature waters& Xª 7> #No. ++& *;> #No. +,& >T,  

Cl-HCO- WK HCO- LO0

SO. ¯° Z [ Na± \2P ]²³@ ´µP^(T ¬' PT\s ¶|}*%' :[:L,
_T@GH(TH1¢`aM,'  *·¨  #}}*bcLOP}*, ¸¹LºT ^,-.[ 0?'%

P&

Shimabara-kanko Hotelw
Shimabara-onsenw
Motoikew
Shinyama-onsen Kami-no-yuw
ShinyuhKojigokuh
Tanaka-sow
Karimizum
Kunisaki-ryokanw
Karako-onsen centerw
Mizuho Sennen-no-yuw
Yugyoku-onsenw
Harajo-sow
Harajo Masagow

Seawater (Obama)

+ SB
, SB
- SB
. SB
/ UZ
0 UZ
1 OB
2 OB
3 OB
+* KK
++ MH
+, YH
+- HJ
+. HJ

+/

04.
14.
14,
041
,4.
.424.
/41
24*
14/
142
24.
24141
24-

+042

pH

,.43
-*41
-*4/
+04+
//41
.14,
+**
,.41
014*
+-4,
.343
-04,
,040
,042

Temp


3522*

+3*
+./
,21
+,4,
04+
04/
,52**
+-41
,5.3*
+52+*
.5,0*
.-1
,342
++,
-1.

--40
,-4*
-,4,
-43
,4,4.
,/0
24/
,-.
324/
+04+42
14,
++4,
+5,**

,/*
0-4334/
34,4.
,4,
+/1
+242
+/*
,.+
142
+4.
34,
14,
-2*

+13
//41
0,42
,/40
141
042
+-1
,.4,
+.2
,3+24*/41+24.
+-4n.a

n.a
n.a
n.a
n.a
,4*42*
n.a
n.a
n.a
n.a
n.a
n.a
n.a
n.a
n.a

n.a
n.a
n.a
n.a
*4/+
*4-1
n.a
n.a
n.a
n.a
n.a
n.a
n.a
n.a
+250**

3,4/
+240
-24+
241
-41
-4/
.53,*
04,
.5/**
-53**
/5+1*
+,4/
.41
++43
,5+.*

114*
++4+.40
14,.0
+,3
,2.
+24-,/
..+
n4d
n4d
n4d
,43
+/1

,5*0*
223
+5.,*
+-1
*
*
,*2
+1,,,
+.*
,51**
+5+0*
3,4.
-3+

Na
K
Mg,
Ca,
Al-
Fe
Cl
SO., HCO-mgῌl mgῌl mgῌl mgῌl mgῌl mgῌl mgῌl mgῌl mgῌl

+4/

.34.
.34.
.34/
.14/,4,
/*41
-043
.34/
-24+
-*4,
.+4/141
./4.
.240

dD
 

*4+0

14*.
141,
1412
14.1
141,
14,.
.4.1
14.0
.4//
/4.3
/422
24-+
14,1
14,0

d +2O
 

Sampling date (in ,***) : Nos4 +* and +- on Feb4 2 ; Nos4.5 15 25 ++5 +, and +/ on Dec4 +- ; Nos4 +5 ,5 -5 3 and +0 on Dec4 +. ; Nos4 /5 0
and +. on Dec4 +/@ SB : Shimabara5 UZ : Unzen5 OB : Obama5 KK : Karako5 MH : Mizuho5 YE : Yue5 HJ : Harajo
w : well5 h : hot spring5 m : mineral spring ; n4 a4 : not analyzed5 n4d4 : not detected (detection limit of SO. ion *4*+ mg/l)# : Water sample was collected from Shinyama-onsen Shimo-no-yu about +** m away from Shinyama-onsen Kami-no-yu4
d +2O and d -.S of SO. ( HSO.SO.,) in No4 / sample (Shinyu) are.4, and/41 5 respectively4

Name

Chemical and isotope compositions of waters from wells5 hot springs and mineral springs in the Shimabara Peninsula

No Area

Table +56ῌ῏῍῎» /, ¼ ,**,

7ῌd¸¹º., 

57

 

ῌ

Table +

 ῌ!"# $%& ''() dD-d +2O *+,-./0)%1 Fig. -A 2 3456789: No. 1 );<=> ?

Table + )@ABC @Aῌ?DE*.*.0 ; @A dD ' d O >FGHGI00./J I3.3+J+2

K( LMNO2 P Q9)%1RS MWL  d TU5T'UVT 1.*J' ,*.,J >  dEdD

I2Wd O X#YZ[2+2\]+^_`a#Y HCO- b' SO. b)BcG7ῌd No. +e0, 2, +-, +. > fhi jklBmnopqr)LMNOcG sGY7ῌdg7 No. +,t> Ruvwxos' y=<o2 zD7 No. +*  {7 No. ++ 4|fg
7

No. +,> 0} ,~PG r)xol

RS)Y#)jk

'>3`a =<o2 P 567 No. 1, 3 +_O> RS#YViG )LMNOcG=4 uv jk' 3wxo' Y#  =<o'3G3Y3<2jk'uv)no567 zD7 {74|fg7
7ῌd No. 1, 3, +*, ++, +, );<= ClI ' dD #Y cY)
uv

=o2 sGY7> <G()<w)=YG7ῌdwx fg7
>Ruv ¡?l¢£yn
ClI ¤<Tynw Table+  ¥¦§¨©lxo2 Fsw 56w'jk<= IR¥ B 9)%1 ,PGpq 2 sNo. 1, 3

Fig. -

ªS' dD «wq r ) 5 6 7 

+_O>¬P=4

 567?ljk
R'¥)=­a
('=® §¨wxo2 F=s)= (¯° dD-d +2O *+,./0567'

+_O ±oFig. -A  No. 1, 3  ¥²)

D ³Vc´oµ =<os'l¶o2 Fµ'=U(·n<

Fig2 , Ternary plots used to classify waters based on
the relative proportions of Cl, SO. and HCO- ions(A) and used to recognize equilibrated waters (B)for waters from wells, hot springs and mineralsprings in the Shimabara Peninsula. Symbols withnumbers correspond to those in Fig. +2

GH¼

58

  +320  
!

 
water

" andesite-magmatic

dD#$,*%*& d +2O#'2%'+,& ; Giggenbach, +33,a ()*+,- ./0, ! 12
3145 6/78490:;ῌ<4/=>?@4?A B C DEFGHG

HῌIH" J,K LMNOPQ"R

STU"V"(W4/=X

YST  ,/0 - SSCl-dD Z[4\STPQ"$V"(W]^4_`abc
-B  PQ"dV"Fig.

e f4)

T:;R9gh iGH4U"V"(W4/7j3 S,
- kO" 31lBGH
No. +, C GH No. ++ m/nLM

V" No. +/ opqrstbdD-d +2 O u s v ! w x Fig. - A [ dCl-dD Z Fig. -B [ yAz{4| Fig. -A, -B }{  @GH"R

STE~ePQ"

Y LM.=T@
R>S S,.-



Fig- - dD vs. d +2O plot (A) and dD vs. Cl ion concentration plot (B) for waters from wells, hotsprings and mineral springs in the Shimabara
Peninsula. Cold spring and shallow groundwater
data are referred from Kazahaya et al. (unpublished data). Symbols with numbers correspondto those in Fig. +- GliGH } No. 1  No. 3  C GH No. ++ m/nGH No. / 45 PGR PQ4mGH"GR*S
T-  - GH45 6 .-,:;V"(W  Mg,' RST Na-K-Ca G Fournier and Potter, +313 RS GH45 13, H, O-SO.#HSO.$'SO.,$  G1R

STG Mizutani and Rafter, +303 RST ¡R Table , 4>?- iGH"G! ,**¢ R>S +32. 4£T¤
 +21¢%,*,¢  +320 yA¥?- "¦4§S ¨"4©+K#STª,  iGH"«"O@@ +* ¬­*ST®¯4°g/0- C GH*G 21¢

7 GH±²³ +,*// m G 0/¢ ´ ! ,*¢ i´ - GH

P}"Gm/. +/*¢ c GH"SO.  d -. S ¤ '/.1&

$µ H, S .

 '..2&%'..3& yA¥?@ f? k%P"&¶T·¸,¹µ4/7NOPQ"ºcXYST" @R»\¶- /7lGk%P"M© /, ª T,**,V  "$ῌ#$ ¤_¥¦§¨

Table ,

Estimations of underground ﬂuid temperatures in the Shimabara Peninsula
Name

Calculated
Temp4(V

Geothermometer

ShinyuTanaka-so
Kunisaki-ryokan
Mizuho Sennen-no-yu

+/+
+30
,*2
21

d +2O TH,O;SO.V A¡
Mg-correction to the Na-K-Ca geothermometer[B]
ditto
ditto

No Area@
UZ
OB
OB
MH

/
1
3
++

59

@ UZ : Unzen5 OB : Obama5 MH : Mizuho[A] Mizutani and Rafter (+303)5 [B] Fournier and Potter (+313)
 : SO.UHSO.;WSO.,;  
..







.+  !"#$
%

Name

DIC*
TmgῌlVd +-CDIC
T£V

Shimabara-kanko Hotel
Shimabara-onsen
Motoike
Shinyama-onsen Kami-no-yu
Tanaka-so
Karimizu
Kunisaki-ryokan
Karako-onsen center
Mizuho Sennen-no-yu
Yugyoku-onsen
Harajo-so
Harajo Masago

,5*1*
00.
+5+,*
+,.
,5-2***
+5*3*
+/*
..41
+1.
1.4*
+,,
,1*

;.4*.
;1410
;0411
;,*4.*;/40***;-40.
;240+;++4/2;04.2
W*412;+,423;2421

2142

W+41***No Area¢

Table - Concentrations and isotope ratios of dissolved inorganic carbon(DIC) in waters from wells5 hot springs and mineral springs in the
Shimabara Peninsula&'() HCO-

* %+,-. Cl */Cl-HCO- 01*234

56 6 +** 78+,*** mg ῌ l 9:

HCO-; ,<= >



+
,
.
1
2
3
+*
++
+,
++.

SB
SB
SB
SB
OB
OB
OB
KK
MH
YE
HJ
HJ

Seawater (Obama) HCO-  +/

 "$%ῌ#$% ?

@ SB : Shimabara5 OB : Obama5 KK : Karako5 MH : Mizuho5 YE :Yue5 HJ : Harajo* DICUCO,(aqVWHCO-;WCO-,;** collected values for CO, separation using chemical and isotopic
compositions of steam phase5 and steam/water ratio (*4*.0)*** cited from Sakai and Matsuhisa (+330);@AB2C 67
7D8E >5FG
HIJ245>KA7L M
N "$% OPQRSTDICUCO,TaqVWHCO-;WCO-,;VXYKRZ[\]^_`B Td +-CV

78 RSB2 abIK01cd,efgh)i45  Tjk ,**+V >>6G lh,m ,nL
So$Cpq"$,rsQ "#$%DIC

XYK d +-C t, Table -  TSo$ DIC )uvwjxyz{|  }~t)85AV >  "$ y TNo. 1V,nL6&t "$%78

 $%DIC

CO,

|KG5]^_2

XYK d +-C t 2xy

CO,

XYK d +-C t

TTable /V xῌ% T*.*.0V ,Lv
., 78  "$ TNo. 1, 3V  % 0)85  DIC

6F

»¼

60

  

    , !"#

Cl 

DIC $%&' ()*+,-./DIC

0$12 3 4 5No. +*6 7 8 9:;$<=
>DIC?nsw@>DIC?smp5DICῌCl6swA>Cl?smp
d +-Cnsw@5d +-Csmpd +-Csw6A5>DIC?smpῌ>DIC?nsw6Bd +-Csw

 >DIC?nsw

() DIC

DICῌCl  >Cl?smp

 

* >DIC?smp

+,-./0$ C FG 

DIC

DIC * 5DICῌCl6sw

Cl *$ C d +-Cnsw d +-Csmp d +-Csw

HIDED()

 +JKLMNFO

PQ R7  S TU V WX 5No. 16 V -.

YZ[ 5No. 36 4 5No. +*6

L

DIC \2

DIC

] 

DED +῍ +.῍ .+῍ ^_7#D ]$%&R`ab$ 3  ] FR7c`ab$ DIC

* d

ef d +-C g 5  +ῌDICd +-C g6 hijk 5Fig. .6 l mnS  5No.
.6 

DIC]$%&R4 5No. +*6tuOvwxy

DICCO, 5z +33/ ; {| ,**+ }vw CO,  ~6 $R    vw

 ,*o TUVpF d +-C q$rs

DIC *{'FR^#D

 vw CO, *

pFO %pDR2  #D   L

R `abk $ l l V 
L DED SU p#D#   d +-C S  5/o6  5Fig. .6   l l ¡¢£¤ 5No. +6 V ¥`abk"#¦ d +-C q§¨DR D ©ª

L 5No. 26

 -. TU
©ª

CO,

 DIC

CO,

DIC «R-.¬pD2  #D ­® 

d +- C q

DTU ,o "# /o tOVpR 5Table-  Table / ; Kita et al.,+33-6 + ῌ DICd +- C gS

~D  ,  ¯°)D# , 0 8±


²³$´



 l! ῌL



DIC



vw CO,

!."µpD¦R d +- C q$7=

CO,  8±¶ #F  l! · R
7 ^ ¸ p D  G U
5Ohsawa et al., ,**,6 

TF¦R d +- C q$r
 CO, $¹º¹()Fig . d +-C vs. reciprocal concentration plot of dissolved inorganiccarbon (DIC) for waters from wells, hot springs and mineralsprings in the Shimabara Peninsula. Symbols with numbers
correspond to those in Fig. +. For soil water box see text.

» /, ¼ ,**,

  ῌ "(o¸¹º61Table . Estimated carbon sources of dissolved inorganic carbon (DIC) in waters fromwells5 hot springs and mineral springs in the Shimabara Peninsula
Contribution (῍)

No4 Area@

Name

SB
SB
SB
SB
OB
OB
OB
KK
HJ
HJ

+
,
.
1
2
3
+*
++.

Magmatic CO,

Soil CO,

Seawater DIC

+**
2/
3*
+.
3/
+**
0+
1
/0
13

*
+/
+*
20
.
*
,/
/,
..
,+

*
*
*
*
+
*
+.
.+
*
*

Shimabara-kanko Hotel
Shimabara-onsen
Motoike
Shinyama-onsen Kami-no-yu
Tanaka-so
Karimizu
Kunisaki-ryokan
Karako-onsen center
Harajo-so
Harajo Masago@ SB : Shimabara5 OB : Obama5 KK : Karako5 MH : Mizuho5 YE : Yue5 HJ : Harajo  d +-C  No. 2   No. + CO, ! "#$%&'( -Heῌ.He

et al., +33-. //0 12  d C)*+,- Kita

345 CO, 367689:;< =>?:; @A+-:;BC D  No. ++ EF No. +, =.  GH
K+,- Table /. L!
.

T

DIC =MNOP CO, 89:Q d C+-

CH.

34RS UV:WS CH.  XG&'(YZ 8+[. \&'( +,C]S^. DIC =_`aG d C+-

 Sh. @AG=676C CO,

3b<+GcRSd <

IJ

CH. G

>?cUe:;fgi j*-K ; : gk. l  ;lm. ,**+.  nop

DIC Gq<rstuv 2&'(wx 3yz. 67

6C CO, OP CO,

3}~<=;

{q|D EF3. DIC Gqῌ

{q| ;+ -,cRS :.

DIC G*676C CO, OP CO,

i3. &'(Gq< p

3GS
d +-Csmpd +-CmgmXd +-Csoil+/X

++G. X =676C CO,
C CO,. OP CO,

i. d +-Csmp. d +-Cmgm. d +-Csoil =. KK&'(wx3. d Cmgm  d Csoil+-+-

DIC. 676 . KK//0 ,-  . /,-0 Ohsawa et al., ,**, 3 S G*S 3I*. ^3 Table . GJ*S
89

CO,

©

DIC

i

¡oῌ¢ . o£ G676_? + b¤K . ++:¥G¦<§+=. oῌ¨
DIC

ªc«

67689:;^ ¬-KS+:;[. + 3­®CS¯° fg ¯° , +31- 3±4 c². ³ No. +*
G 1῍ 12 676C CO,i ;cR . i ´ S*G S

0 !hµ:. i= *῍ cS*. 676C CO,:;fg·:;

DIC

i ;RS¶:12

²8

62
./ ῌ

 .. ῌ   CO,  !"#$%  &&' ($ῌ)*+,-./01234$56(%,-.78ῌ9:;<=> -.?@%, CO, A CH. /-.=BC+,DEF;GHI=

J
K (%

O, Table / = LMNO PQ RS /K TU1VW LMXY ,ZA>[ \]U178<=^_[K`ab=cd> CO,-He-Ar ef<gGiggenbach, +33,b hijk> ! Fig. / l, gTm(%andesitic An(%op'qrst-.< u-.!2vTwxyzK {>CO,

|}=~, <' AS andesitic subducted 4$ AT andesitic thermogenic 
4J 

st-.<' basaltic An(% opl 9Q]+,

CO, |}=~,A <' BM basaltic mantle 4$ BC basaltic contaminated 7+, Ja=m+u-.U1K 1/U1> 2 !|+,A %$<' ME meteoric endmember 4J

¡2¢£

06+,-. No. 1, 2, +0, +1 ' 2vTwx¤¥VW=~[__qrst. U1+,K!|}>Zl,&A=m>[_,! CO, ῌ Ar ¦! ,./§+*- ¨+.3§+*. A U1% ..*§+*©,  /¨0 ªU«_&A4$ CO, ¬_['U1+,EK'ῌ4l A­!l,A®¯, ¡2῍°±$%-.

Fig / Relative CO,, He and Ar contents of sample gases listed in Table /, together with those of
the potential endmember components : meteoric (ME), andestic (AS, AT) and basaltic (BM, BC)gases. Symbols with numbers correspond to those in Fig. +. For AS(andestic subducted), AT(andestic thermogenic), BM(basaltic mantle) and BC(basaltic contaminated) see text.

OB
OB
MH
YE
UZ
UZ

Tanaka-so
Karimizum
Mizuho Sennen-no-yuw
Yugyoku-onsenw
Seishichi-jigokuf
Seishichi-jigokuf

w

Name
314*
3/4.+4*
,24*
3/41
3/43

+**
,.41
.343
-04,
314+
+*1

3142,
n4a4
n4a4
n4a4
304.2
304-2

CO,

Temp4 H, O(῎) (Vol4ῌ)
*4//
*4+.
n4d4
n4d4
,4.
,4+

H, S
+43
,40
04,
++4.
+4*
*431

N,
*4/.
+41
/+42
/342
*40/
*42+

CH.
*4*++
*4+2
*41+
*4/1
*4**3
*4*+,

O,
*4*-2
*4*-,
*4*-/
*4+*4**//*4**/*

Ar*4*+0*4**21*4***/*4***/
*4,*
*4,*

H,

He
*4***/*4**+*4**/3*4**3.
*4**++*4**++

Composition of gas exclusive of H, O (Vol4ῌ)*4**,2*4*++*4,2*4**,3n4a4*4**.0C, H0

῍/4῍/42
n4a4
n4a4
῍.4,
῍.4,

CO,

῍,142
῍,34,
῍-/40
῍0242
n4a4
῍,24,

CH.

d +-C (῏)

Chemical and isotope compositions of gases from fumaroles5 thermal water wells and mineral spring in the Shimabara Peninsula

Sampling date (in ,***) : Nos4 15 25 ++ and +, on Dec4 +- ; Nos4 +1 and +2 on Dec4 +/@ SB : Shimabara5 OB : Obama5 MH : Mizuho5 YE : Yue5 UZ : Unzenf : fumarole5 m : mineral spring5 w : thermal water well
n4a4 : not analyzed5 n4d4 : not detected
d -.S of H, S in Nos4 +0 and +1 samples collected from Seishichi-jigoku are ῌ.43῏ and ῌ.42῏5 respectively4
dD and d +2O of H, O in No4 1 sample (Tanaka-so) are ῍004/῏ and ῍343+῏5 respectively4

1
2
++
+,
+0
+1

No4 Area@

Table /

 /,  ,**,
ῌ

63

M¼K

64
No. ++, +,    
  !"#$%&#"' $( !")*

+,./01 23456 7 89 CH.ῌCO,

"
+*

;,

 /.0:+*;-<+.2: CO,  = CH. >?@AB7"- CDE CH.

CO, FGHIJKL$"MHNO,EP CH. QR +- C ῌ+, C
  CO, S4DETUVW"

XYE4CO,Z.H,[CH.Z,H, O\] ^_, Ono et al., +33- 9`abcdSefg hi]jklm,n$ Fig. 0 "- ^Magmatic CO,9no pq

r./pss7 89n CO,  d +-C t ;..+u ; Kita etal., +33- 7vwnx o] CO,

JKῌQRN" CH. S  CO,  7  Chemical Z isotopic
equilibrium9noyz7DE{|9n}o ~Q!" "- Figure 0 ]`bcdfm
No. 1, 2, +1 E"  CH.

Fig- 0 d +-C values for CO, (open symbols) andCH. (closed symbols), and CH./CO, ratios ofgases discharged from Unzen and Obama
areas (Numbers correspond to those in Table/). The trend for both chemical and isotopic
equilibrium between magmatic CO, with avalues of ;..+u and CH. is shown as shortdashed line, and the equilibrated temperatures
are plotted along the top (Ono et al., +33-).

CO,  JKῌQRN NM -** " $"- 3 
]nJKL MN$ NO, A
E" Giggenbach and Goguel, +323  7 89ny]!

N"$A"#$,En' $(./ ῌ%M No. ++ 345&M No. +, '(
M)*T CH. $FWDE" Table /- CH. ¡¢QR d +-C $

CH. £¤)!"+¥" 9E" ,YP ¦-7 +333  CH.

 d +-C t

CH.ῌC, H0

3 ./2."/0 Kiyosu et al., +33, 1.,E CH. £¤*,n6 Mῌ'( CH.  §¨4©N"

4DE ª«QR 2$¬AE"' $( ­37®n- d +-C;CH.ῌC, H0 efg hi Fig. 1 ]jklm9nbcdfm7 %M No. ++

 CH. ¯°4+±4_²4 Thermogenic  &M No. +,  CH. 
5²4³.4²,nx Biogenic " $´9n- 3 4© CH. £¤µ¶$6w" ·¸¹2¶ Table + $º»,E"' $¶ /, · X,**,\³´µ³uῌ¦:;&'(  



65



 
!"# $%&'()*+,.0-./0#12345ῌ

 
6 789:;%<ῌ'(=> ? @A9BC'(DEFGH9IJKL CO,ῌArM
H, ῌ Ar NOPQRSTUV4KW

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BC XNo. +0, +1\

 6 , w'(xFig5 1 d +-C values of CH. and CH./C, H0 ratios ofaccompanying gases from Mizuho (Mizuho Sennen-no-yu : No. ++) and Yue (Yugyoku-onsen : No.
+,). Thermogenic and biogenic boxes are referredfrom Sato et al. (+333).

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Ca-Al,-silicate
K-feldsparCO,
K-micacalcite.XFeO+./\.XFeO\O,.5- V#e ]V stu68W n1+V4

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Fig5 2 Evaluation of H,-Ar, CO,-Ar equilibration conditions for gases from the Shimabara Peninsula. Symbols with numbers correspond to those in Fig. +.

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66

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Chiba, H. (+33+) : Attainment of solution and gas equilibrium in Japanese geothermal system,
Geochemical J., ,/, --/῏-//.
Fournier, R.O. and Potter, R.W. (+313) : Magnesium correction to the Na-K-Ca chemical geothermometer, Geochim. Cosmochim. Acta, .-, +/.-῏+//*.
Giggenbach, W.F. (+322) : Geothermal solute equilibria. Derivation of Na-K-Mg-Ca geoindicators, Geochim. Cosmochim. Acta, /,, ,1.3῏,10/.
Giggenbach, W.F. and Goguel, R.L. (+323) : Collection and analysis of geothermal and volcanic
water and gas discharges, Fourth Edition. Report CD,.*+, Chemistry Division, DSIR, New
Zealand, 2+p.
Giggenbach, W.F. (+33, a) : Isotopic shifts in waters from geothermal and volcanic systems
along convergent plate boundaries and their origin, Earth Planet. Sci. Lett., ++-, .3/῏/+*.
Giggenbach, W.F. (+33, b) : The composition of gases in geothermal and volcanic systems asa function of tectonic setting, Proceedings of the Seventh International Symposium on
Water-Rock Interaction, 21-῏212.

= 4T },*** : '(  ,, ,-1῏,./$Kiyosu, Y., Asada, N. and Yoshida, Y. (+33,) : Origin of light hydrocarbon gases from Matsukawa geothermal area in Japan, Chem. Geol., 3., -,+῏-,3.

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Kita, I., Nagao, K., Taguchi, S., Nitta, K. and Hasegawa, H. (+33-) Emission of magmatic He with
di#erenct -He/.He ratios from the Unzen volcanic area, Japan, Geochemical J., ,1, ,/+῏,/3.
Mizutani, Y. and Rafter, T.A. (+303) : Oxygen isotopic composition of sulfates, -. Oxygen

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68

isotopic fractionation in the bisulfate ion-water system, N.Z. J. Sci., +,, /.ῌ/3.

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Ohsawa, S., Kazahaya, K., Yasuhara, M., Kono, T., Kitaoka, K., Yusa, Y. and Yamaguchi, K.
(,**,) : Escape of volcanic gas into shallow groundwater systems at Unzen volcano(Japan) : Evidence from chemical and stable isotope compositions of dissolved inorganiccarbon, Limnology, (in press))ab +31- :c Tde>IJ fQR gh&   c_[ijkQR

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Ono, A., Sano, Y., Wakita, H. and Giggenbach, W.F. (+33-) : Carbon isotopes of methane andcarbon dioxide in hydrothermal gases of Japan, Geochemical J., ,1, ,21ῌ,3/.

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