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Origin of Deep Hot Spring Waters in
Kanagawa Prefecture, Japan
Kazuhiro ITADERA+, Joji KIKUGAWA+ and Kei ODAWARA+

Abstract
Origin of deep hot spring waters in Kanagawa Prefecture is investigated based oncompositions of major ions and oxygen-hydrogen isotope ratio. It is found that they areclassiﬁed into three groups. Hot spring waters of group +, which are seen in the coastal
area, are considered to be originated from mixing of seawater and meteoric water. Theirisotope ratios indicate that contribution of the latter is small. Hot spring waters of group,, for their formation fossil seawater is probably involved, are divided into two subgroups
based on the ratio of calcium ion in total cation. Hot spring waters of subgroup ,-A are
characterized by the feature that calcium concentration is higher than that expectedfrom the gypsum precipitation model. It is supposed that a cation exchange occurs between the sodium ion in the rock and the calcium ion in the water. Those hot springs areseen in the central and southwestern parts of the Prefecture. On the other hand, hotspring waters of subgroup ,-B show lower calcium concentration than that expected, that
is, a reverse cation exchange that causes dissolution of calcium-carbonate is considered tohave taken place in the course of their formation. They are distributed in the northeastern part of the Prefecture. Hot spring waters of group - which exist around Tanzawa
Mountains are considered to consist of groundwater recharged by rainwater. It is supposed that major chemical ingredients are supplied not by the present or fossil seawater,
but by the contents in the stratum where the hot waters yield. This assumption is supported by the geology of the stratum and the groundwater ﬂow inferred from the waterlevels, as well as by geographical distribution of the isotope ratios.
Key words : deep hot spring, fossil seawater, cation exchange reaction, groundwater ﬂow

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{| G5'} c*GF . * /f:;<l3~3Hh *># ^_`VG5)l*eG?VC 3iS mnop
2mnop ,-A *7.)l* , !3 :;< G5.-

89-  Y 3 f K VC Y .GD)23b c*.a:;<l35 VC h . )l* G5V
C 36ge1, TL a:;<l. 89- *VC 3Z, !
1, ! ,73H  )l* Wmnop ,-B t*. 89- 22* VC Z3 , !2J"512*  ` +32- *>L7 . b D +* +*.

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 Ur ¬3\­ a!)23­G

{| G5'} c*GF VlD. ® @³ ´"*²µWVUG5

1¯°, ! Fig. - ¶7

¯°U!±3²+§*h·#.H  r

¬3a!7 ¸¹VC  $j*>º»¼½.«!2J"5 ))2.

Fig. +*

Distribution of transmissivity of the stratum that yields hot spring waters.
 +*    331 







!" #$% & '() *%+ , 

&-% .!/0+12 #$%  34 &5'/678
9 :89 8;<=>8+'(/% 0$ 8 8;?@ AB4'(CD E !F G"H+I'( +, JKLKM/0+ NOP+ Q
R!IS0DT-/UV&W%+XY$%
/, 



ZP+I'[+\ NOP \= ]+'( ^_(/ SO., #;`a%0+!4\% $ ῌb% +322 -4&cd[+CD :efgKh ,& SO., #!

^_(/+/i!W%0+ E jk&NOP!l'(/%m&F!M/+XY
$%
8&'no_$[P! SO., ;pi<=q(+'( M rs&Ct% ῌ 8
Ca, + uJvwx&y%

% SO,.

Mg,

z{|} Ca,)~+ ῍ CaSO.

j+*+&yz{!,$(/%  +31/ B[ F rs&C/(- 

&y% [_ SO., !p$%0+1.#$(/% ῌ/ +312 1^_(04' 5[=P !=t$ NOP

SO., #1&-%

004 P!8&'no_$[ 2&yD#$%K;XY% 0 +\PCy} j A#; E$$ XA, xA +-%  & 2&1¡j!

¢&£B$%! 004 P;-%2 j#; A¤&¥¦+-%
ZP

Cl #;G§+-%+ 2&y%3 f ¨©&yDª«4\%

fxClῌXCl

῎

2&y%P 3ª«#$%j A#+ & £B$%j A#

+ ¬ DA A-difference 
DAxAfῌXA

῏

4#$%
DA*­R  j A# ZP  ®4¯4!4\%  DA*­R °± h¦²!l-%0+&y³( E j´j!5N'[0+;µ'(CDNOPN10 K&£B$%
Fig. ++  fgKh ,- fgKh ,& SO.

,Ca, Mg, Cy} SO., &]/( fῌXA + xAl¶;µ!·+¸£B$(/=/ c yi& Ek+'(- &y% m&F1X6'=t$==/! 7&P!#$[­R+I-%+ ·+¸-d( &]/( Ca, )~ Mg, Cy} SO., z{'(/%
0+ 894 :e ῌ uJvwx Cy} ῍ CaSO.

*+ &y³(P!NOPN'[1 +'(¹:;_%
Fig. +, & fgKh , &;'[&]/( ῎ ῏ ©&yDºª'[ DMg + DSO.

;µ- :e q( ῌ &yD Mg,z{<+ <l¶Ca, !NOP&#$%0+&=%

 & SO., !·+¸£B$(/=³[0+ P&£B$(/[ SO., !
q( ῍ &y³(»(p$[+-$ E z{<;µ- DSO. n@*+&y% Ca,z{<&=-%¢4W%
'%& Fig. +, &C/( ¼½
῍DMg῍῍DSO.῍l¶!>_$% 0 0+ Ca, + uJvwx&yDp$[ Mg,332

z{<! *+&

 /3  ,*+*





Fig. ++ Relationship between calculated concentrations of calcium ion,magnesium ion, and sulfate ion and analyzed values of those ions.
 ++ 

 !"# $% SO.,  !"#$$%& Ca, &'()*!+$,-.)!  +$/ 0123 Ca, 4 " 567&89:

Ca, ;<= >?

2@AB&

4 %CD? EFGHIJ K YCa $? "LG YCafῌXCa῍DMg῍῍DSO.῍

῏$+MN Fig. +- &-.$O ῏ F&H
IJ

P&

V. Ca, 4@A$QRST ῌ ῍ ,U

YCa $ WX

3 Ca, 4

xCa "YZ.?! +[YZ\],^ _Fig. +, Relationship between di#erences of calculated and analyzed concentrations of magnesium ion and those for sulfate ion.
 +,

 
&'()*# !"# +,$%& 567 dCa xCaYCa $ DNa 3

WX Na 4 $2@A`,UV. Na 4$7 ῎ F&a)HIJ  bc&d!
)eN Fig. +. G  Fig. +. &f dCa
NghiG" DNa $j&kl?m8bNn_
333 







  !"#$%&'() ,-A $*+, -$./0123 &'() ,-A $4*% Ca, $56  7 Na $89
:;<=>23:? @A.$ Ca, :B
CD4.$ Na $EFGHI
Ca, 756O

J$KL!MN2

P7QR

RS

Mizukami et al. +31. % T UGV'W 4$

XYZ[\]B^_$`a? D47&b(
GcdA $eGebfgEU:$EFGHIh
1\, Na ῌ Ca-Cl i1j#:!k23
 l m +321 % -01n#opq$Dr@s1# CaCl, % tuPv7
Fig. +- Relationship between calcium ion concentration calculated by considering dilutionof seawater and precipitation of CaSO. andanalyzed value.
 +-  CaSO.  !
"#

wZ*+xyqA.$z{:D4$|}h
1\>2~_:QR23&'() ,-A $$s*% \
1 41#@4$ 73: [\]4A:=>23@A$4P73
:? @4$%+l,=3:
7>2 $@s1[32% $ ῌ ῍
1\, SO., !>BCD471+
, @A.$ Na :$EFGHI1\>2j!
MN231+:QR  Fig. +. 1[32 dCa 7  $  s*%DNa %$!:>23 

!"#$%&'() ,-B $*+, -1<23 BCD4.$ Na !56 Ca, !89:2% @A.$ Na :BCD4.$ Ca, :$*$ :%$EFGHI
J$KL7QR ,**+ % @4:

J#vC7D_A*+: CaoeGebfg
EU*%=< NaoeGebfgEU7¡<¢£
Fig. +. Relationship between di#erences of calculated and analyzed concentrations of calcium ion and those for sodium ion.
 +. $%&'()*! !+,"#2[, Nao eGebfgEU:@4.$ Ca,.:$EFGHI1\, CaoeGebfgEU7¤_ Ca, 7@4.?,¥:
23 l C¦ +320 % §¨-©ª1«# Ca ῌ Na-Cl $j$¬B1­3
2`a NaoeGebfgEU: CaoeGebf

gEU:$EFGHI1[32 $¢_789#:1\, |®1.$Ca, 789 Na 756#:!¯°23

± Fig. +. 1[32 dCa 7$s*% dCa 7$²³´µ DNa :$1 =|¶%!·¸ ¡<$¹7῍DNa῍῍dCa῍$s1)fºU23 ­l, Na $51
»2 Ca, $8979=3:1= %¼?$¤* BCD4.1 Ca, 7½623334

 /3  ,*+*





!"# $%&' , (6789 :;< $%&' ,-B )*+,-./0 ClHCO- 12345
=)>98 ῌDNaῌῌdCaῌ?)@A DHCO- BC

DEFG;H IJK)0L9MB1N;1OP7 Fig. +/Fig. +0 ) $%&' , Q HCO- R STUDVA Fig. +0  Fig. 3 DWXA YZ3W1[\ ]^_`1a9bQcd<0 HCO- R 1 * )e9 fg
hd<0 YZ3W1a9;Hij A6Ok]^_`1l9;Hij HCO-
R 1[\6mn1N
op +33* 0 qrs Na  CaCO- 1tuG;IJ1vw]^xyA;)z78
[R

 NaHCO- {]^1|5};D

VG89 :~0
῎ ]Q Na Q Ca, -./r
῏

CaCO- )zQ Ca, 

HCO- 


#G)z<2)hd])G dCa 16$%&' ,-B 0

~ ῌ ῍ )z# SO., D

7 1 }) ]-./r
CaCO-   ~ ῎ ῏ D85}89s1 )J)"980 ]^B`1 9s1

M@)[9;w P }]^¡¢£¤0 ; D¥¦G89

Fig. +/ Relationship between di#erence in analyzed concentration of bicarbonate ion andcalculated value, and those for calcium ion,in hot spring waters of group ,-B.
 +/  ,-B  
 !"#$%&'Fig. +0 Geographic map showing spatial distribution of the di#erences
between calculated and analyzed concentrations of bicarbonate ion.
 +0  ( !)*'335



/-







!"#$ +31/   ! "#$%&'()*+,-./012'30456 789: Ca, ";!<=>?'() @:'*+,./!AB C?DE SO., -FGHI NaCa-Cl JK !LM@NO?0PIO Q(RHK ! Q56Q>'ST0PI4?UNVWX Y 8'Z4O[$7 /* \5 : ,**1 ]ZO9: $%&??

6' CaSO. "#$!^_UO4`  ab SO., -Fc>?'HO]ZdR ef'ghij ,   SO., -C?DEFD]IHI>?9: k+  CaSO. -./@l4m
n9:op0 WX] CaSO. -FGHImn'ST0PIOqrs!tu:NOFig. +1  Table , 'vw4xy-6?'  SO., z${(b HCO- z$? CaSO.

*+, '|UO SI 12}~ -04]ZO 12}~'Z4 P ,/ '{O*+,"#$ *.*+/ molῌkg 9: "#$- ,.,/E-. ?04Fig. +1 '(NV ghij + {(b -  SI* ]Z) CaSO. '|0P12]ZO >N'|0P ghij ,   SI `P @= CaSO. '|0P0=12]ZO>?!9O  HCO- z$? SI '{IP HCO- z$!ICE SI !%=H P
IO ?{) HCO- z$^_'7& !I?tu:NO>?9: ghi
j ,  !*+,'|0P12H 7& -PIO?UO>?]
ZO$!qr]ZO 090H!: ghij ,  +,'|UO12}~0=%=  ¡¢£¤¥'(O¦#6§¨]HIqrs!ZO Q'©IPª«
UO4`' ¬­®¯° d-.S ± ²Y87³´µ¶'ef'FGNO·¸'©IP¹º »uV Yamanaka and Kumagai, ,**0 !¼½]ZO

Fig. +1 Relationship between saturation index for gypsum and concentrationsof sulfate ion, or bicarbonate ion.
 +1 


336

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

0ῌ ῎ ῍ ῏ 

  !"#$% &'()*ῌ+,-./0   1234)5,- 

6 5789 - 1:;<=!>08

? 5@:;<=6 9$AB7.C32!0DE!
FG)32!:;<= + 6HIJKLMNO!0DE! 8 2>0!P"#6QB20R +$%/&S'(8 2>0.
T)32!
:;<= , 6)*+U3)32! SO., ,8VW3 2>0
576X-I8')32!0DE^_ 58I$`a2:;<= ,-A 0



Y./Z[\0W! Ca, ]K

2:;<= ,-B 0b! :;<= ,-A 0:;<= ,-B 06 5@8c!!de#$%5f2g *ῌ+g123!&S'K2f2 45higjkl
8mB?32!/0DE! n) :;<= ,   j  S ' )32!X - I  8SO., .o?p71236 674) CaSO. 89q :*Z[\rstuv

wx$!y123/D;c!<.8O!/)B2:;<= ,-A 6=z))3#`
= Ca,SO., .o?X-I8

!

0Z[\{|$?3>}.~U3j0DE! ?c!

!PS'8 2>0 #$%e0B?32!!8 2>0 @4)hiO!023!
:;<= ,-B 6 SO., .o?X-I8  !0Z[\{|0 CaCO- A
y.C3j32!B8DE!  e8C?Da2>0g
1E3!!P"Fhi !P'/B`O!0DE!
:;<= - 6GH!I)32! 1#$%+ >!
d!P6GH!+J !#$%)JIG?3"F)32!0R 5
 !=.A) 2!/0DE!
676  $%.K 5 .D)3 - 1:;<=L.
M) :;<=6 !ND/mB?!d)32! 6 eNDB$.M)3 5DB8`0!Pu3OX.
P!00/ :+g!}^_I X-I >}g!0C1234.QW!<.8O! B# 67)<R6 S !

T?3/O` 5U 676 " Vc!Z 
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676 V?«.¬05^_­^$`W"./00W
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       !"#$ %&'(')*+,-./')*+0 112345'0+6ῌ῏῎῍Dansgaard, W. (+30.) : Stable Isotopes in precipitation. Tellus, +0, .-0ῌ.02.

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H' I J KL +320 : MN O(ῌPQ)RCC"STUD"#E$&= (VW
XYZ /+ , ++-ῌ+,,.
[\]^*+_` ,**3 :+_aPbcdbe /1 p.

f,- +321 : g./0hA O16iB<2< &=FhCj3kl4
m6i n - Basic rock sea water interaction F CaCl, o=pq&'
r YZ ,+ -ῌ. 1*ῌ2*.
  ,**. : Ssi526 C"D"#E$%F< = 7 /1
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 Y5Yuv:wx  ,**1 : y; 6z{|<}=  ? -3 13ῌ2..
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C

YZ -, + /ῌ+0.
C  +32. :[\<  ,2. p., D E

Lawrence, J.R. and Gieskes, J.M. (+32+) : Constrains on water transport and alternation in theoceanic crust from the isotopic composition of pore water. J. Geophys. Res., 20 (B3), 13,.ῌ
1313
Matsuo, S., Kusakabe, M., Niwano, M., Hirano, T., Oki, Y. (+32/) : Origin of thermal waters fromthe Hakone geothermal system, Japan. Geochem. J., +3, ,1ῌ...

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Mizota, C. and Kusakabe, M. (+33.) : Spatial distribution of dD-d+2O values of surface and shallow groundwaters from Japan, south Korea and east China. Geochem. J., ,2, -21ῌ.+*.
Mizukami M., Sakai S., Matsubaya O. (+311) : Na-Ca-Cl-SO.-type submarine formation waters
at the Seikan Undersea Tunnel, Japan. Chemical and isotopic documentation and its interpretation. Geochim. Cosmochim. Acta, .,, +,*+ῌ+,+,.

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Yamanaka, M., Kumagai, Y. (,**0) : Sulfur isotope constraint on the provenance of salinity ina conﬁned aquifer system of the southeastern Nobi Plain, central Japan. J. Hydrol., -,/,-/῍//.

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