@A J. Hot Spring Sci. 0* /,ῌ0. ,*+*ῌ῍ῒΐ῎ΐῑ῍ῐῌῐ῏BCDE+ FGHI,
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Chemical Properties of Hot Spring Waters in
Nozawa Onsen, Nagano Prefecture
Kenta EMORI+ and Hiroaki TSUKAHARA,

Abstract
Chemical properties and isotopic composition of hot spring waters at the spa area inNozawaonsen Village, Nagano Prefecture, were investigated. The origin of the hot springwaters is proved to be meteoric water on the basis of the oxygen and hydrogen isotope
ratio. The hot spring waters were classiﬁed into two groups of geothermal systems according to ratios containing chloride ions in total dissolved anions, a relatively high concentration group, and a low concentration group. The variation in chemical compositionof low concentration group does not generate with mixing the geothermal waters of highconcentration group and surface water. Therefore, there is an own source in each group.
Further, the variation in ion composition of the hot spring waters in the same group revealed that the ion composition was controlled by mixing two original hot waters, a hightemperature and high ion concentration water, and a low temperature and low concentration one. The mixing ratio varies depending on hot spring site and time. Every group has
their own two original hot waters. The spa area is in a valley on the boundary between
the volcanic rocks from Mizuoyama volcano and Kenashiyama volcano. The group of
relatively high concentrations of chloride ions, containing two hot springs “Shinyu” and“Takinoyu”, seems to be upwelling from the original waters under the Mizuoyama volcano because of their locations, and the others from Kenashiyama.
Key words : Nozawa Onsen, Origin of hot springs, Classiﬁcation of hot springs, Water
property and geology, Hydrogen and oxygen isotope ratio+ -3*ῌ20,+  -ῌ+ῌ+
!" : #$%& '()-,3ῌ*+*/ *+,-./+01$234 +ῌ+ + Graduate School of Science and Technology,
Shinshu University, -ῌ+ῌ+ Asahi, Matsumoto-shi, Nagano-ken -3*ῌ20,+, Japan. Current Position :Research and Development Division, Kurita Water Industries Ltd, +ῌ+ Gochoyama, Kawada,Nogi-machi, Shimotsuga-gun, Tochigi-ken -,3ῌ*+*/, Japan,) 5678 -3*ῌ20,+  -ῌ+ῌ+ 9:; : -23ῌ*2+, <=>? +-*3 , Faculty of Science, Shinshu University (Professor Emeritus), -ῌ+ῌ+ Asahi, Matsumoto-shi,Nagano-ken -3*ῌ20,+, Japan. Contact address : +-*3 Haneo, Chikuma-shi, Nagano-ken -3*ῌ*2+,,
Japan.

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 : High temperature hot springs,  : Quaternary volcanoes.  : Main cities +   ,**.
    53+,-.

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Modiﬁed map of Miyauchi et al. (,***)
TK : Takinoyu, SN : Shinyu, KW : Kawarayu,
OG : Ogama site (/ hot springs : Shimogama,Takenoshigama, Marugama, Yudegama, Oogama), OY : Ooyu, XῐY : Line for cross section for Fig. ++, and Dashed lines and hatchedlines : Active faults.
 ,  ,***TK : SN :  KW :  OG : /  :      OY :  XῐY : Fig. ++   !
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Table +The concentrations of major dissolved components of hot spring waters in the Nozawa Onsen area.
 +  

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

55

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$%& '()  *+,-%.)/   Fig. .b 01-(230 &45678?%.)9567:;<=>567 &@ABCDE567>F)GHIJ K.)> L K 8M NO& 9567<=>?P5678 @ABCDE567:;<=/?% QR&S!)*+ TU 567<=>?% LV1W+%
Fig. -. A view of upwelling of hot springs at Ogama site.
From the front : Takenoshigama, Marugama, Yudegama and Oogama -   XYZ[&#02\+8] ^8$%>K> '(_(!` [aW+b)  9567 X
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0lgmn#Vop;0m9q mqrsVtuWp Table+ 9qrs)mqrsvwV Fig. / 01g xy B & Craig +30+ 02zmy
dD2d+2O+*

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B 0g.)VWp y A dD2d+2O,0 & ῌ  +310 02yK] }m& A ) B 0K)Wp Fig. / 0&0M0+QR  +32* NO Q +331 /1g & A ) B 0K] m&}mn# K.)>1-(+%{|!Qrstu Giggenbach +33, & Q@A@0l-(@A@mrs> d+2O/+* dD+*-* 0K)Wp 'V Fig. / 01g y C & Q@A@m)!V/ K] @A@m>g(m&.y C 0g &Q0K] @A@l-(pm>¡(+%¢£>K\p> &¤¥&;(8\p 8M NO¦Q§0K¨mrs&.y0K.)>o(+%Q +331+ ©?#m0e!m>ª<= «.)02\+# U¬­®U>¯«+%)°ug( m)567 X)&yvw08.)>±-( ¡p # &²³V+ ´µtuV!+%> .(">=<=$%¶0·¸W+%)g(yvwV1g&¹ K Fig. 0 0m)4567º `/ X?% 9567)vwV1g
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Fig. .a

Trilinear diagram for Nozawa Onsen hot spring water samples.
 .a  

Fig. .b Trilinear diagram for Nozawa Onsen, Kusatsu Onsen and Yamanouchi
Onsen hot spring water samples.
 .b    58) 0* * ,*+*!"!#$%%&Fig. / Relation between d+2O and dD for Nozawa Onsen, Kusatsu Onsen andYamanouchi Onsen hot spring water samples.
Dotted line A : Upper limit line for Japan meteoric water (Matsubaya andSakai, +310), Solid line B : Global meteoric water line (Craig, +30+), Dashedline C : Mixing line of meteoric water and andesitic magma water.
 /     d+2O  dD  A : ῌ +310  B :  Craig, +30+  C : Fig. 0 Relation between water temperature and concentrations of sulfate ion.
 0   N +,-./0, 121 M  N 345 Fig. 0 6 7,859: ;-<7,25=>/0?8 @ABC<DE1F8,GD5 Table + <HIJK< +*'LM/ NOPQRST5 *.0(*.3 mgῌL UT/7, -GDV M I,<5$T.W8 X59

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 1 
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Fig. 2 Relation between concentrations of sulfate ion and sodium ion.
 2 
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Fig. 3 Relation between concentrations of chloride ion and sodium ion.
 3 
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9 Fig. + D3E Fig. , FGH3IF , /JKLM NOM 8PM QRST&USTV>WXY"Z5[56F\]H) ^_ῌ`a ,**+ 9b , =>LMSTcNOMLMdST 8PῌefMLMdST*gh&'() 1i"9NOMLMST 8PMLMST*jH ^_ῌ`a ,**+ F3)5 kc Fig. +* FGH b5 klmL61)*+, -./01234

Fig. +* Distribution of rocks erupted from Kenashiyama volcano and MizuooOoiriyama
volcano (Kaneko and Tsuchiya, ,**+).
Black and gray areas : Rocks from Kenashiyama, Horizontal line area : Rocks from
Mizuo-Ooiriyama, XῌY : Line for cross section for Fig. ++ +*   ῌ ,**+:   :  XῌY :Fig. ++  !"#$%&'(89:;<89: 89=> +.-ῌ+.* Ma,  +33+ !?@A B>CD;
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Fig. ++ Conceptual model of geothermal water system in Nozawa Onsen ++  AῐB    !"! #$%  &'()*+,-ῌ. ,**+ ) /012/3/ 456789:;
<= ><=?@AB/CC+D EFG)!HI)J4$%% !K
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de!K fghij)6bῌ 2k+ 2+,l- "6 2W.2+LK῍ ):mn +oE:mnpq[%r) /%r , s0"t6b
῎ ,urvjbw

, A2 [:mn12[2)/:mn12/2 xq 3EDEFG3U xq 4yzt+`{|3E}'῏ /56)2/56#b~b78!K92sG!H%H #b~b

92s+xqH%)

bK :-oE:mn12[%;<;  2/s0 =/s0) b">KD ? 0@LK ((!HA!j' B/FCF#  DEk+ῌ2+,l5F  IR-MS GH%Kz%Kzt+
` HCI GI "4J%Kz%K K ¡KD ¢C""U¢C£¤ ¥¦£¤ L§ ¨M5? 0@LK NOP+
G!K Q© + ª«¬­R®¯ F F°±Fs²³´µ¶FlOP)!H!A!
K+ S|aF &·¸¹K ¡ )G""ºT%Kz%K cU©V)µ»DNOP `¼Wbj!K ½%K!j'63 ῌ῏῎῍Craig, H. (+30+) : Isotopic variations in meteoric waters. Science, +--, +1*,ῌ+1*-.

 ,**2 : ῌ   !"#$% &'() *+,-Giggenbach, W.F. (+33,) : Isotopic shifts in waters from geothermal and volcanic systems along
convergent plate boundaries and their origin. Earth Planet. Sci. Lett., ++-, .3/ῌ/+*.

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