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1 The Journal of Engineering Geology, Vol.19, No.4, December, 2009, pp s yw p»» y Áš«Áy Á, /BHBP Á½³w Á½ 1w œw, 2 w, w ƒyw, 4 yw w w Hydrochemistry and noble gas origin of hot spring waters of Icheon and Pocheon area in Korea Chan Ho Jeong 1 *, Yung Kwon Koh 2, Seon Ho Shin 2, Keisuke Nagao, Kyu Han Kim 4, and Gun Young Kim 2 1 Department of Geotechnical Design Engineering, Daejeon University, Daejon, 00716, Korea 2 Korea Atomic Energy Research Institute, Daejeon, 055, Korea Laboratory for Earthquake of Chemistry, Graduate School of Science, University of Tokyo, 1100, Japan 4 Department of Science Education, Ehwa Woman University, Seoul, , Korea s swš w yw,, š x š» p w yw p š,»» w yw wwš w. w 7 ƒ wš, œ w t 17 w w. yy ü e ph p š,» 10~75 µs/cm. 21.5~1.4 o C x, w. ph w w CaHCO ü Ca(Na)HCO yw x, s e ph NaHCO x yw y p. w š, s w p. δ 18 O δd ƒƒ 8.85~ ~72.2 y». s w w š w ¼ e w. ü» He/ 4 He ~ »» x w p( )» yw s p. s ƒ» x yw. w w» yw w w y wk 4 He/ 20 Ne. 40 Ar/ 6 Ar»» w. :, yw, x, He/ 4 He, ƒ» Hydrochemical, stable isotopic (δ 18 O and dd) and noble gas isotopic analyses of seven hot spring water samples, eleven groundwater samples and six surface water samples collected from the Icheon and Pocheon area were carried out to find out hydrochemical characteristics, and to interpret the source of noble gases and the geochemical evolution of the hot spring waters. The hot spring waters show low temperature type ranging from 21.5 to 1.4 o C and the ph value between 6.69 and Electrical conductivity of hot spring waters has the range from 10 to 75 µs/cm. Whereas the hot spring water in the Icheon area shows the geochemical characteristics of neutral ph, the Ca HCO (or Ca(Na)HCO ) chemical type and a high uranium content, the hot spring water in the Pocheon area shows the characteristics of alkaline ph, the NaHCO chemical type and a high fluorine content. These characteristics indicate that the hot spring water in the Icheon area is under the early stage in the geochemical evolution, and that the hot spring water in the Pocheon area has been geochemically evolved. The δ 18 O and δd values of hot spring waters show the range of 10.1~8.69 and from 72.2~60.8, respectively, and these values supply the information of the recharge area of hot spring waters. The He/ 4 He ratios of the hot spring waters range from to *Corresponding author: chjeong@dju.ac.kr 529

2 50 yáš«áyák. NagaoÁ½³wÁ½ which are plotted above the mixing line between air and crustal components. Whereas the helium gas in the Icheon hot spring water was mainly provided from the atmospheric source mixing with the mantle(or magma) origin, the origin of helium gas in the Pocheon hot spring water shows a dominant crustal source. 40 Ar/ 6 Ar ratios of hot spring water are in the range of an atmosphere source. Key words: hot spring water, hydrochemical composition, low temperature type, He/ 4 He ratios, crustal source ù 1981 x¾ 404 (k, 2008). 18 ƒ ûw û 5 o C w ûw û sw. p w Ÿ w w 26 (65.1%) wš, Ÿw Ÿ 84 (20.8%), wy 27 (6.68%), y 17 (4.21%), k 1 (.21%) (k, 2008). w w yw w ü w yw yw p ³, y w yw y w,, w yw w ü w ƒ w (Koh et al., 1994; ½³w x, 1998; Yun et al., 1998; ½, 2000; š«, 2001). š 5 w yw p ü x,, š»(noble gas) mw ƒ»w ww š w ƒ (y, 2007; y, 2008; ½³w, 2008).» ƒ w (Nakamura et al., 1999; Okazaki et al,. 2001; Osawa et al., 2002). ü w» p w» w ƒ wš, ù ƒ» y w ƒ w (Aka et al., 2001).» s sw, w t y yw p ³wš y w w wš w(fig. 1). p ƒü w y»(he, Ne, Ar) w,» yw p w w w. w ü w»ƒ q. yw p y w, yw w., s Fig. 1. Location map showing the study area, and detail location map of two hot spring sites(sinbuk and Jeil hot springs) in the Pocheon area.

3 s yw p»» 51 Fig. 2. Geologic map of Sinbuk hot spring area(a), Jeil hot spring area(b) and Icheon hot spring area(c). yw p ww» w vw p» x( y, 1974;, 1999) w w»wš w. Fig. 2 w. œ,» y, w ty. y Ÿ,,, w. š z» w ³ w N10~20E,, w š. y ü wš j ƒ ùkù, N25~0W, 60~80NE N25E, 60NW w w. s ù ƒ r, r,» w y,» wš. d NE w. xd w», s ƒ wš, œ w t 17 w. sww x (ph), yy(eh),,,», š k dw. ph Orion 290A { ph d», Eh»» w dw.» Orion model 142» d», w Orion model 85 d» ƒƒ dw. w x 0.45 µm w w

4 52 yáš«áyák. NagaoÁ½³wÁ½ z. sp» z ƒw ph 2w yg eù» wš w. yw w (Ca, Mg, K, Na, Si, Fe, Mn, Sr) w»w Ÿ Ÿ»(Unicam model 989, AAS), w v Ÿ»(Shimadzu model ICPS1000 III, ICPAES) w, w v»(fison model PQ III, ICPMS). SO 4 2, Cl, NO, F w Dionex 120 jm v w. yw y mw» w w yw w³x w., y CO 2 H 2 O sx(epstein and Mayeda, 195) w wš, w y(coleman et al., 1982; Kendall and Coplen, 1985) w w z w»w»(; VG ISOTECH PRISM II) d wš, w»(; Euro Vecstor Euro Pyrorl micromass Isoprime) w dw. d ts³ dw. d ts³w(smow) t yw ( ) ùkü. x t dw δ 18 O δd ƒ ƒ ±0.1, ±1.5.»» w ƒ w ƒyw p w œ» w w.» 50 cm.» mvrvl. l» e ƒ y w» dw e. mv rv w l w» TiZr s w yg. š s þƒ l s w He Ne š ArKeXe» w.» He, Ne, Ar VG5400 (MSIII) w ƒyw»» w.» t»»w dw w. m xd», s, w, t w ph, yy(eh),»(ec), (DO), x dw Table 1 w. œ 200~1,10 m. xd 21.5~1.4 o C, s (JI) 1.4 o C ƒ. ph 6.69~9.21 s ƒ ph, phƒ w w e œ ƒ w w ¾ ¼ mw e y w. yy (Eh) 45~178 mv y w t y. w y w t w w q» y ty w y y w. z ü w ew. pheh w(t) w, ph ƒ Eh w w (Fig. a). ph ph (Fig. b). ƒ w y mw yw y w e w. š s ƒ w ph š, Eh û p.» 10~75 µs/cm. ƒ ¾ IC2 IC 700 µs/cm s w. w t» ƒ ƒ 7.2~46 µs/cm, 104~4 µs/cm.» ph w

5 Table 1. Hydrochemical data of of hot spring water, groundwater and surface water samples collected from the study area. (unit : mg/l) 1) Sample ID Sampling T ( o C) ph Eh (mv) EC DO (µs/cm) (mg/l) Na + K + Ca 2+ Mg 2+ Fe Sr 2+ Si HCO CO 2 SO 4 2 CI NO F 2) EN (%) Hot spring water JI1 05/12/ JI2 05/12/ JI 05/12/ SB 05/12/ IC1 05/12/ IC2 05/12/ IC 05/12/ Groundwater PCG1 06/8/ PCG2 06/8/ PCG 06/8/ PCG4 06/8/ PCG5 06/8/ PCG6 06/8/ < MD 05/12/ ICG1 06/8/ ICG2 06/8/ ICG 06/8/ ICG4 06/8/ Surface water PSC1 06/8/ PSC2 06/8/ PSC 06/8/ ICS1 06/8/ ICS2 06/8/ ICS 06/8/ JI, SB, PC and MD series samples: water samples from the Pocheon area, IC series samples: water sample from the Icheon area EN (%) :charge balance error 1) 2) s y w p»» 5

6 54 yáš«áyák. NagaoÁ½³wÁ½ Fig.. Relationship between temperature, Eh, electrical conductivity and ph of hot spring water, groundwater and surface water samples from the study area. PC: Pocheon hot spring, IC: Icheon hot spring, HW : hot spring, GW : groundwater, SW : surface water. (Fig. c). 0.0~0.1 mg/l û.» ƒ. w t ƒƒ 0.21~7.40 mg/l,.42~6.44 mg/l y. yw p p, w, t w Table 1 w.», s, w, t 2+ Na +, K +, Ca 2+, Mg w p. Na + 2.1~54.2 mg/l š, s.7~92.8 mg/l. s ƒ w w. w t Na +.6~.6 mg/l. K + JC mg/l š 0.72~2.21 mg/l û. w (ICG1, 4) t K ƒ š mg/l. w 2+ e w w. Ca 41.8~68.2 mg/l s 0.78~21.0 mg/l. w t 2.52~0.9 mg/l. Mg w ƒ s 2+ w. w t 0.55~6.91 mg/l. Fig. 4(a)». s w y» w. t w w s» ƒ Na + +K + w j ƒw Ca 2+ +Mg w w w Ca 2+ +Mg w Na 2+ +K 2+

7 s yw p»» 55 Fig. 4. Relationship between major ions and electrical conductivity(ec) of hot spring water, groundwater and surface water samples from the study area. PC: Pocheon hot spring. w ƒw 2+ Ca 2+ +Mg w ƒƒ w w. yw y. w m yw x. ü HCO, Cl 2, SO 4, NO, F w p. k Ÿ w,» m ü CO2 ƒ w w»w HCO 110~211 mg/l (IC2, ). w t ƒƒ 10.7~180 mg/l j w. 2 SO 4.98~19. mg/l w 2 š yü SO 4 w w û r. w t 1.00~16.6 mg/l ƒƒ. Cl 7.08~4.2 mg/l s w. Cl z NO w t w ƒ w. w t 0.44~9.56 mg/l t(ics1) w(icg1, 4) w û. NO w»», ywù s» w»w. tƒ š NO, 0.00~25.9 mg/l. s NO. (IC) 25.9 mg/l.» 45 mg/l (NO N, 10 mg/l» yw ) w «ew œ ƒ w. F 0.29~7.94 mg/l. 0.29~0.57 mg/l û w s 2.18~7.94 mg/l w. F» x(caf 2 ) w, ƒ, z(ca 5 (Cl, F, OH)(PO 4 ) ) O 2 OH eyw Ÿ w k» w. s ph yw y p, y» OH eyw F wƒ ü F» w(apambire et al., 1997). Fig. 4(b)».» ƒ HCO ƒ w w, SO 4 2+ Cl ƒw ƒ s j. p ü tw w Li, Al, Sr, Fe, Mo, Mn, Zn, Ba, U (Table 2). ü Li w 85~10 µg/l w tü w 0.12~7.51 µg/l w. Al 54.9~522 µg/l w š. (IC2, IC)» 200 µg/l w. Sr 120~1,110 µg/l, p s SB 1,110 µg/l w

8 Table 2. Data of trace elements of hot spring water, groundwater and surfacewater samples collected from the study area. (unit : ppb) 1) Sample ID Li B Al Ti Mn Ni Cu Zn Ga Ge As Br Zr Mo Ag Sb Cs BA W Pb Th U 5 6 Hot spring water JI < <0.10 < JI JI < < SB IC < < < IC < < IC < < < < Groundwater PCG < <0.05 <0.05 < < <0.05 < < < PCG < <0.05 <0.05 < <0.05 < <0.05 < < < PCG <0.05 <0.05 < < < < PCG <0.05 <0.05 < < < < PCG <0.05 <0.05 < < < < PCG < <0.05 <0.05 < < < < MD < < ICG < < < ICG < <0.05 <0.05 < < < < ICG < <0.05 <0.05 < < < ICG <0.05 <0.05 < < < < y Á š «Á y Á K. N a g a oá ½ ³ w Á ½ Surface water PCS <0.05 <0.05 < < < < PCS <0.05 <0.05 < < < PCS <0.05 <0.05 < < < < ICS <0.05 < < ICS <0.05 < < ICS < < < < ) JI, SB, PC and MD series samples: water samples from the pocheon area, IC series samples: water sample from the lchen area

9 s yw p»» 57. w t 10~00 µg/l w û w. Fe 10~40 µg/l, w t û ù, w(icg1) 10,900 µg/l w. Mn 0.9~ 7.6 µg/l û w, t w 0.79~966 µg/l. s ü Ge 1.9~10.7 µg/l 0.2~1.12 µg/l w. ü U w s JI2 5.8 µg/l w š, 9.7~ 50 µg/l w. y sw wü U ƒ ü š ( y w, 2008). yw x», s, w, t yw x yw yp ww» w qr(piper, 1994) w. qr yw x j 2 xk (Fig. 5). Ca(Na) HCO x w, s (JI1, JI, SB) NaHCO x w. w, w, t CaHCO x w. y (1997) w w yw y w w y r w yw y» CaHCO x w y e w Ca(Na)HCO x e NaHCO x y w w. s JI2 w ph 8.5 x NaHCO x yw p. ph 7.0ü w w yw x. w œ wš ph yw x j š p y d p Fig. 5. Trilinear plots of chemical composition of hot spring water, groundwater and surface water samples in the study area.

10 58 yáš«áyák. NagaoÁ½³wÁ½ yw yƒ w k, d ü Ca 2+, HCO œ ƒw k Ÿ wwš w. p», s, w, t w, w Table w.», s δd = 6.78δ 18 O0.97. δd 60.8 ~64.6, s 65.5 ~72.2. δ 18 O 8.69 ~9.01 Fig. 6. Diagram of δ s 9.27 ~ O versus δd values of major water samples in the study area. PC: Pocheon hot spring, IC: Icheon hot spring, ƒƒ. Fig. 6, w, t δ O 18 δ H 2 Craig (1961) w y (MWL) û š, w t y Table. Stable isotope composition of water samples collected in the study area. ù y. Sample No. δ ƒ y». 18 O( ) δ 2 H( ) Hot spring water z, xp š z w š. s JI JI JI SB IC IC IC Groundwater ICG ICG ICG ICG PCG PCG PCG PCG PCG PCG MD Surface water ICS ICS ICS PCS PCS PCS t w û δd δ O 18 w šx ¼ y y. w û δ H ù 2 δ 18 O w w w w. œ y s w w ƒ en w j.» p», td, ü w { y y»»(noble gas) w (tracer) w wš (Aka et al., 2001). p x ( He/ He)»y 4 d ƒü y dw j pl td { w. x He x»ù x sz x. 4 He U(Th) a.»» x. He/ He 4 w y ù j» ƒ x w w ƒ š. yƒ, ƒ, w, w,, Ÿ

11 s yw p»» 59 Fig. 7. He and Ne isotopic ratios of the hot spring waters and groundwater collected in the study area. He/ He p 4 40 Ar/ 6 Ar wì» w š.» š (Ar) 6 Ar, 8 Ar, 40 Ar ƒ. 40 Ar Kù Ca l x» 40 Ar/ Ar 295. ü k 6 ƒ š x» 40 Ar/ 6 Ar { j. ƒù y ù 40 Ar/ Arƒ j 6.», yw sww ü kƒ ù yw w. xƒ»», ƒ, p œ ƒw mw 7 w 1 (MD) Fig. 7 w.»» x yw wš, s ƒ» x yw w. s 4 He/ 20 Ne x yw. ƒ w He/ 4 He ~ ¾. s ƒ w He/ 4 He ~ Þ10 6 š, ƒ w He/ 4 He ~ ü ƒ He/ 4 He»» û 6. ƒ» He 4 w w. 4 He/ 20 Ne ü l He w»» He yw w w. Fig. 7»p yw»» He, Ne p»( He/ 4 He= with 4 He/ 20 Ne > 10000) yw w p ùkü.» Fig. 8. Diagram showing the relative ratio of argon isotope of hot spring waters collected in the Gyeonggi area. ƒ yw» ƒ»( He/ 4 He=5 10 9, 4 He/ 20 Ne > 10000) yw ùkü. w yw(p», ƒ»). He, Ne ƒ yw w. p s He ƒ yw p w» w w.»pƒ yw» p š, s ƒ» xƒƒ w p. s w p( )» He yw w. ü w p w wz w vƒ. s w» He/ 4 He ù 4 He/ 20 Ne» w yw., 4 He/ 20 Ne ƒ w y w yw w. Fig. 8 Ar ( 40 Ar/ 6 Ar 8 Ar/ Ar) 6 w. ü 40 Ar/ 6 Ar ~02.76»» 295. w.», s yw p ph 6.69~9.21 e š,» 10~75 µs/cm.

12 540 yáš«áyák. NagaoÁ½³wÁ½ yy Eh š, w t yy. 21.5~1.4 o C x,. yw p w ph CaHCO xü Ca(Na)HCO x w w p, s w e NaHCO x yw y p. yw p d p y yw y w. δ O 18 δ H y 2, s w û š w ¼ w. w w ƒ w wp q. ƒ w He/ 4 He ~ š, He/ He 4 4 He/ Ne 20 s ƒ»»ƒ w»» yw p( )» x yw p. w» p š w w wz w ƒ eƒ. 40 Ar/ 6 Ar 297.~02.8»» 295. w. d y k sƒ w. w w»w. šx y w, 2008, w (I), w, 29p. š«, k, ½,,, 2001, š y yw y: yx w, y, 4, 294. ½, š«, ½,,, 2000, yw p, wmy, 7, 246. ½³w,, y, K. Nagao, 2008, y w yw, y, 41, 152. ½³w, x, 1998, ûw w yw, wz, 19, 224. k, 2008, ü xy p, w xz, 290p., y, 1974, w s(1:50,000) s, Ÿ, 45p., ½,, ½, v, x,, 1999, û s(1:250,000), w, 51p. y, ½m«, ½, ½, 1997, r y w w yw y Ÿ w, w Ÿwz, 10, 4. y, K. Nagao, ½³w, zœ, H. Sumino,, y,, x, 2008, w x yw p»», wmy, 1, 112. y, xx, K. Nagao, ½³w, 2007, yû x yw p»» w, y, 40, Aka, F.T., Kusakabe, M., Nagio, K. and Tanyileke, G., 2001, Noble gas isotopic compositions and water/gas chemistry of soda springs from the islands of bioko, SoTom and Annobon, along with Cameroon Volcanic Line, West Africa. App. Geochem., 16, 28. Apambire, W, B., Boyle, D. R and Michel, F. A., 1997, Geochemistry, genesis, and health implications of fluoriferous groundwaters in the upper regions of Ghana. Environmental Geology, 124. Coleman, M, L., Shepherd T. J., Durhham, J. J., Rouse, J. E. and Moore, G. R., 1982, Reduction of water with zinc for hydrogen isotope analysis. Anal. Chem., 54, Craig, H., 1961, Isotopic variation in meteorc water, Science, 1, Kendall, C. and Colpen, T. B., 1985, Multisample conversion of water to hydrogen by zinc for stable isotope determination. Anal. Chem., 57, Koh, Y.K., Yun, S.T. and Ahn, J.S., 1994, Environmental isotope and hydrochemical studies of geothermal waters in Korea: Yusung geothermal area, Jour: Korean Inst. Mineral & Energy Resour. Eng., 1, Nakamura, T., Nagao, K. and Takaoka, N., 1999, Microdistribution of primordial noble gases in CM chondrites determined by in situ laser microprobe analysis: Decipherment of nebular processes, Geochim. Cosmochim. acta, 6, Okazaki, R., Takaoka, N., Nagao, K., Sekiya, M. and Nakamura, T., 2001, Noblegasrich chondrules in an enstatite meteotite. Nature, 412, Osawa, T. and Nagao, K., 2002, Noble gas compositions of Antarctic micrometeorites collected at the Dme Fuji Station in 1996 and Meteoritics and Planetary Science, 7, pp Piper, A. M., 1994, A graphic procedure in the geochemical interpretation of water analyses., Transactions of American Gophysical Union, 25, Yun, S. T., Koh, Y. K., Kim, C. S. and So, C. S., 1998, Geochemistry of geothermal waters in Korea: Environ

13 s yw p»» 541 mental isotope and hydrochemical characteristics, I. Bugok area. Econ. Environ. Geol., 1, š, y w œw Ÿ 96 Tel : Fax : chjeong@dju.kr š«w d q 055 Ÿ 1501 Tel : Fax : nykkoh@kaeri.re.kr y w œ w q 0570 Ÿ 4622 Tel : shinsh@kwater.or.kr ½³w yw w w p x 111 Tel : kyuhan@ewha.ac.kr, /BHBP Laboratory for Earthquake Chemistry Graduate School of Science University of Tokyo Hongo, Bunkyoku, Tokyo 1100, Japan TEL: FAX: nagao@eqchem.s.utokyo.ac.jp ½ w s»» 055 Ÿ 1501 Tel : Fax : kimgy@kaeri.re.kr