Hydrochemistry and genesis of CO2-rich springs from Mesozoic granitoids andtheir adjacent rocks in South Korea
CHAN HO JEONG,1* HAK JUN KIM1 and SUNG YEOP LEE2
1Department of Geological Engineering, Daejeon University, Daejeon 300-716, Korea2Korea Atomic Energy Research Institute, Daejeon 305-353, Korea
(Received May 7, 2004; Accepted May 23, 2005)
Many CO2-rich springs are found in Mesozoic granitoids and surrounding rocks in South Korea. Their presence islocally restricted to three regions: the Kangwon region, the Chungcheong region and the Kyungpook region. Discharge ofmany CO2-rich springs is mainly related to the geologic structures, i.e., the geologic boundaries, faults and dykes. Thesixty-three CO2-rich water samples can be classified into three chemical water types; Ca-HCO3 water, Ca(Na)-HCO3water, and Na-HCO3 water. Most of the soda waters show a high CO2 concentration (PCO2 0.12 atm to 5.21 atm), a slightlyacid pH (4.8 to 6.76), and high ion concentrations.
The microscopic observation and the chemical analysis of host rocks at CO2-rich spring sites show that the carbonateminerals are secondary precipitates and interstitial fillings in Cretaceous sedimentary rocks that are the main sources ofCa, Mg, HCO3 and Fe in the CO2-rich waters of the Kyungpook region. The carbonate minerals locally present in thefractures of granite and gneiss would be one of the main sources of abundant Ca, Mg and HCO3 in the CO2-rich water ofthe Kangwon and the Chungcheong regions. The chemical composition of these CO2-rich springs according to host rocksand discharge regions was compared by using the Box-Whisker diagram.
Oxygen and hydrogen isotope data indicates that the CO2-rich waters are of meteoric origin. The carbon isotope data(δ13C –6.6 to –0.9‰) suggest that the carbon of the soda waters is mainly derived from a deep-seated source, but is partlymixed with CO2 derived from carbonate minerals. The formation process of the CO2-rich springs can be summarized asfollows. After the CO2 gas derived from the deep-seated source enters the groundwater system along faults or geologicboundaries, the CO2-rich water evolved into three chemical types depending on the aquifer rock types.
granites.The CO2 gas in groundwater may be derived from
various sources including metamorphic devolatilization,magmatic degassing, oxidation of organic matter and dis-solution of sedimentary carbonates (Schöell, 1983; Chivaset al., 1987; Giggenbach, 1992; Harris et al., 1997;Cartwright et al., 2002). The origin of CO2 gas can beestablished by isotopic analysis of 13C, which indicatesthe presence of mantle-derived CO2 gas (–8 < δ13C‰ <–3), or CO2 derived from biogenic activity in the soil(–22 < δ13C‰ < –25), it may also be the result of meta-morphic devolatilization (δ13C‰ > 2) (Céron et al., 1998).
Carbon isotope compositions of CO2 gas demonstratesthat CO2 gas in most studied springs mainly comes froma deep-seated source (Griesshaber et al., 1992; Ishibashiet al., 1995; Schofield and Jankowski, 1998; Cartwrightet al., 2002; Marques et al., 2001), and that the origin ofCO2 gas in shallow groundwater from the Rocky Moun-tain Front Range, Colorado is of diagenetic-metamorphiccontribution as well as of a deep-seated source (Mayoand Muller, 1997).
The purpose of this study is to report the occurrence
INTRODUCTION
CO2-rich springs have been reported from all over theworld. The occurrence of these springs is closely relatedto major faults and volcanoes, which are mostly in youngorogenic belts; however, some are in areas of rifting con-tinental margins (Irwin and Barnes, 1980; Griesshaber etal., 1992; Ishibashi et al., 1995; Mayo and Muller, 1997;Schofield and Jankowski, 1998; Cartwright et al., 2002;Marques et al., 2001).
Although the Korean peninsula is a tectonically sta-ble region, CO2-rich springs have been found in manyplaces. The occurrence of CO2-rich springs is restrictedto the Mesozoic granitoids and their adjacent rocks. Inparticular, most of the CO2-rich water discharges alongthe fault zones and the geologic boundaries. These fac-tors strongly indicate that the origin of CO2-rich springsis closely related to geologic structures and Mesozoic
518 C. H. Jeong et al.
and hydrochemistry of CO2-rich springs found inMesozoic granitoids and the adjacent rocks in South Ko-rea. Furthermore, this study presents isotopic and min-eralogical evidence for the origin of abundant CO2 gasand dissolved solids in the CO2-rich water.
GEOLOGY AND OCCURRENCE OF SPRINGS
The CO2-rich springs in South Korea are found mainlyin Mesozoic granitoids and surrounding rocks. These arePrecambrian gneiss and Cretaceous sedimentary rocks(Fig. 1). Mesozoic granitoids are present as two types:(1) the Jurassic Daebo granite (210–180 Ma), which areemplaced by syntectonic and continental marginmagmatism, and (2) the Cretaceous Bulkugsa granite(120–50 Ma) that is of a post-orogenic and intra-conti-nental origin (Cluzel et al., 1991; Jwa, 1998). Figure 1shows the large area of emplacement of the Jurassic gran-ite along NNE direction, and the stock emplacement ofCretaceous granite in the south-eastern area. Most of theCO2-rich springs are distributed in the eastern and cen-tral areas of the granitoids in South Korea, but they arenot found in the southwestern area.
Figures 2, 3, 4 and 5 show geologic maps with thelocations of the CO2-rich springs from three regions inSouth Korea. Figure 2 shows the geologic map of theKangwon region. This region consists chiefly ofPrecambrian banded gneiss, and Jurassic biotite granite,two-mica granite and K-feldspar granite. Several majorfaults, the Whocheon fault, the Woaljeongsa fault and theYeongok fault, are present in the study area (Kim et al.,
1975; Min and Kim, 1996; Kim et al., 1998). In theKangwon province, all springs except K7 are artesian thatflow along fissures of valley floors. The K7 spring is adeeply drilled well and is used as a spa. The K3 springoccurs along the fault that is a geologic boundary betweenJurassic granite and Precambrian gneiss. The K1, K2, K5,K6, K7, K9 and K9 springs are found within the Jurassicgranite body. In the field and in published geologic maps,it is difficult to find the distinct geologic structure re-lated to the occurrence of above springs. The K4 springis found in the Precambrian gneiss. The K10 spring islocated at the geologic boundary between the Jurassicgranite and the Precambrian gneiss.
Figure 3 shows the geologic map of the Chungcheongregion, which is composed of Precambrian gneiss,Paleozoic metasedimentary rocks and Jurassic biotite (ortwo-mica) granite (Kim and Lee, 1971; Lee et al., 1996).In the Chungcheong province, the CO2-rich springs at theBM and MM locations are the artesians that flow con-tinuously along the fissures of the valley floors. Thesprings of CM, DM and AH sites are exploited wells of50 to 500 meter depth. The AH-series wells are used as aspa. The springs at the BM, DM and AH sites are foundat the geological boundary between Jurassic granites andtheir adjacent Precambrian gneisses. Drilling cores andgeophysical investigations indicate the development ofdyke swarms and calcite veins at the CM site (KARICO,1998). Hence, CO2-rich springs at this site would beclosely related to the dyke and the veins within the gran-ite. The relationship between CO2-rich springs and geo-logic structure at MM locations is not evident from a field
C h i na
J a p a n
CO -rich spring
2
CretaceousGranite
JurassicGranite
Pusan
Seoul
0 100 km
Fig. 1. Map showing the occurrence zones of CO2-rich springs and the distribution of the Jurassic and Cretaceous granitic rocksin South Korea.
Hydrochemistry and genesis of CO2-rich springs 519
survey and the published geologic map.Figures 4 and 5 show the geologic map and the loca-
tion of the CO2-rich springs of the Kyoungpook prov-ince. Figure 5 is an enlarged map of the rectangular areaof Fig. 4. This province consists mainly of Precambriangneiss, Jurassic and Cretaceous granites and Cretaceoussedimentary rocks (Hwang et al., 1996). The springs atthe P2, P3, P4, P5, P6, P8, P10, P12, P13, P14, P15 andP16 locations overflow along the fissures of the valleyfloors. The P9 spring is found at the fault on the moun-tain slope. The P7 and P11 springs are wells of 100 to150 m depth. The spring at the P1 site is a deep well (about500 m depth) developed for the use of a spar. The P2 andP3 springs are located at the geologic boundary betweenthe Jurassic granite and the Precambrian gneiss. The P8,P12, P13, P14 and P15 springs occur along the geologicboundary between the Jurassic (or Cretaceous) granite and
the Cretaceous sedimentary rocks. The CO2-rich water atthe P5, P9, P11, P13 and P14 locations comes out alongfaults. The springs of the P1, P4, and P10 samples arelocated within the granite body. Many CO2-rich waters atthe P6 site flow out along fissures of the valley floor thatare assumed to be faults. Many drilled wells at the P7site are located along an assumed fault in the Cretaceoussedimentary rocks.
The occurrence of CO2-rich springs from theChungcheong and the Kyoungpook provinces in SouthKorea show a close relationship with the geologic struc-tures, i.e., the geologic boundary, fault zone and dykeswarms. These geological structures could act locally asa conduit for deep CO2 to rise to the surface. However,most of CO2-rich springs from the Kangwon province donot show a clear relationship between their occurrenceand geologic structures.
Fig. 2. Geologic map including the locations of CO2-rich springs in the Kangwon area.
520 C. H. Jeong et al.
ANALYTICAL METHODS
Sample collection and in-situ measurementSixty-three CO2-rich water samples were collected
from artesian and exploited wells at thirty sites. Threeseparate 60 mL samples in polypropylene bottles, weretaken for analysis of cation, anion, stable isotope (oxy-gen and hydrogen) composition, after having been filteredthrough 0.45 µm Millipore filters. The samples for cationanalysis were acidified to pH < 2.0 using concentratednitric acid. The pH and Eh of the water samples weremeasured in the field using a portable ion meter with dif-ferent electrodes (Orion 290A model) and the electricalconductivity was measured in the field by use of a port-able electrical conductivity meter (Orion 142 model). Thedissolved oxygen content and temperature were also de-tected in-situ by using a portable dissolved oxygen meter(Orion 830 model). Alkalinity, expressed as bicarbonate,was quantified by a digital auto-titrator with 0.05N or0.5N HCl, and methyl orange as an indicator.
Chemical and isotopic analysisIn the laboratory, the major cations (Na, K, Ca, Mg,
Si) and trace elements (Fe, Mn, Sr, Zn, Li, Ba, Al, Cr, Cu,Ge, As, Pb, U) of the water samples were analyzed byatomic absorption spectrometry (Unicam model 989,AAS), inductively coupled plasma atomic emissionspectrometry (Shimadzu model ICPS-1000 III, ICP-AES)and inductively coupled plasma mass spectrometry (Fisonmodel PQIII, ICP-mass). Anions such as sulfate, chlo-ride, fluoride and nitrate were determined by ion chro-matography (Dionex DX-120). The reliability of chemi-cal analyses was estimated by the calculation of the chargeimbalance between cations and anions.
The hydrogen and oxygen isotopes of the water sam-ples were analyzed by use of an isotope ratio massspectrometer (Model VG SIRA II). Oxygen and hydro-gen isotope ratios from water, relative to the ViennaSMOW standard, were determined by the conventionalCO2 equilibration method and reduction with zinc metal,respectively (Coleman et al., 1982; Kendall and Coplen,1985). The analytical precisions are ±0.1‰ for oxygenand ±1.0‰ for deuterium.
In order to determine carbon isotopes in the water sam-ples, the carbon in the CO2-rich water samples was pre-cipitated as BaCO3 by adding BaCl2 (Clark and Friz,1997) after alkalinization of pH > 11. The 13C isotopewas determined on CO2 gas released by the reaction ofthe BaCO3 precipitate with H3PO4. A gas source massspectrometer (VG Isotech PRISM II model) was used todetermine carbon isotope ratio relative to PDB standard.The precision of carbon isotope analysis is ±0.1‰.
RESULTS
Chemical characteristicsThe chemical data for the CO2-rich water samples
collected at sixty-three springs at thirty sites are presentedin Table 1. The chemical composition of the CO2-richwaters varies according to their locations. The electricalconductivity ranges from 101 to 3,100 µS/cm. The DM-series samples in the Chungcheong area have low electri-cal conductivity between 101 and 146 µS/cm. However,the P62, P63, AH2, AH3 and AH5 samples show highelectrical conductivity of 2,790 to 3,100 µS/cm. The pHvalues range from 4.8 to 6.76. The DM-series samplesshow the lowest pH values and the AH-series samples ofthe deep wells show the highest pH values. The Eh val-ues of the soda-rich water show a range of –25 mV to126 mV. The CO2-rich water from the AH-series, the P1and K7 wells has been used as a spa of warm temperaturebetween 22.3°C and 30.7°C. The temperature of the othersoda waters ranges from 2.9°C to 21.2°C. Most of thesoda-rich waters have low dissolved oxygen content.
The CO2 species in the soda water is free CO2, H2CO3o
Granite
Metasedimentry rockGneiss Complex
0 10 20 kmJurassic
Paleozoic
Pre-cambrian
DM
BM
MM
CM
AH
Fig. 3. Geologic map including the locations of CO2-richsprings in the Chungcheong area.
Hydrochemistry and genesis of CO2-rich springs 521
Fig. 4. Geologic map including the locations of CO2-rich springs in the Kyoungpook area.
Fig. 5. Enlarged geologic map of rectangular area in Fig. 4.
522 C. H. Jeong et al.
Tabl
e 1.
C
hem
ical
com
posi
tion
of
wat
e r s
ampl
e s c
olle
c ted
fro
m C
O2-
ric h
spr
ings
in
Sout
h K
ore a
Sam
ple
No.
BM
MM
CM
1C
M2
CM
3C
M4
CM
5C
M6
CM
7C
M8
CM
9D
M1
DM
2D
M3
DM
4A
H1
AH
2A
H3
AH
4A
H5
pH5.
995.
945.
315.
845.
55.
375.
445.
635.
795.
635.
365.
034.
954.
854.
86.
396.
766.
686.
56.
76E
h (m
V)
24.7
52.9
62.8
74.6
71.8
66.4
70.8
72.3
69.2
5670
.175
.864
.285
.374
.641
.317
.754
.841
.1−2
9.1
*E.C
. (µS
/cm
)16
7443
649
112
6556
348
955
639
067
166
335
413
814
612
810
118
5728
2029
5018
5627
90
Tem
p (°
C)
13.6
13.6
15.5
18.5
16.2
1516
.117
.715
16.4
21.2
16.6
14.2
15.2
14.5
25.9
27.5
25.4
24.3
30.7
PC
O2
(atm
)0.
959
0.23
40.
929
0.98
60.
647
0.78
90.
748
0.32
70.
477
0.67
70.
538
0.26
90.
499
0.61
20.
389
0.55
60.
986
0.78
20.
225
0.99
8
(uni
t: m
g/L
)**
D.O
.1.
52.
35.
64.
23.
62.
53.
95.
66.
13.
24.
76.
25.
76.
54.
30.
51.
20.
121.
15.
1N
a73
.143
.528
.737
29.4
28.9
24.1
13.5
3437
.921
.410
11.2
10.3
9.6
111.
728
3.3
280.
012
4.2
305.
9K
2.84
3.07
2.34
1.55
2.06
1.85
1.7
1.71
1.94
2.26
1.46
2.24
2.57
2.31
1.39
2.28
10.6
420
.34.
3511
.32
Ca
293.
339
.759
.220
0.6
72.9
59.6
74.2
47.6
87.9
81.2
39.6
9.8
11.1
10.3
5.1
310
480
330
330
517
Mg
19.5
8.8
10.1
34.5
10.5
10.2
11.4
11.6
1415
.26.
93.
12.
92.
61.
622
.641
.638
.936
.645
.6Si
34.5
9.4
16.2
25.2
18.4
16.6
24.9
17.3
19.2
1723
.318
.423
.520
.213
.646
.244
.445
3843
.8H
CO
312
2224
222
081
823
821
624
015
735
133
713
131
.450
.049
.127
.212
1421
4720
2415
4923
58S
O4
8.7
21.6
17.9
11.8
18.2
19.7
4.7
7.6
13.7
12.9
11.4
0.6
1.5
0.7
1.8
13.4
18.3
21.9
6.2
19.2
Cl
4.6
1526
.928
.331
.127
.222
.529
.421
.929
.217
.518
.910
.33.
86
21.5
21.3
31.3
13.2
22.2
F3.
21.
30.
31
0.4
0.4
0.09
0.2
0.4
0.2
0.3
0.1
0.2
0.2
0.06
3.67
4.17
4.12
3.82
4.35
NO
3N
.D.
N.D
.10
.75.
238
.812
57.1
10.8
23.5
10.1
24.4
18.5
6.8
4.8
8.5
N.D
N.D
0.38
N.D
N.D
Fe13
.24
2.51
0.01
0.17
N.D
.0.
04N
.D.
0.02
0.15
0.35
0.01
0.12
0.03
0.02
0.04
7.15
2.30
2.29
9.67
7.02
Sr1.
80.
510.
51.
290.
550.
510.
710.
30.
60.
560.
350.
120.
120.
10.
051.
532.
41.
812.
312.
5
(uni
t: µg
/L)
Li
294.
150
.414
.139
.823
.115
.937
.223
.346
.645
.634
.837
.417
.624
.128
.926
107
1724
667
0A
l97
.858
.736
.510
6.7
36.5
34.1
285.
952
.936
.545
45.1
47.8
70.6
4810
987
8315
213
9C
r<
0.2
2.2
3.2
1.7
4.4
2.2
1.5
1.2
0.8
8.5
0.2
2.7
2.4
5.5
1.7
5.89
12.1
217.
4314
.8M
n13
5763
646
.910
1430
.179
.555
.323
.314
9684
012
9.6
35.4
35.1
31.1
22.9
870
2550
1820
740
2730
Cu
15.2
26.6
13.1
31.7
34.3
10.8
41.
911
.221
.312
.55.
12.
33.
41.
923
11<
301.
6113
Zn
95.4
17.4
26.1
72.3
73.6
35.6
31.2
33.2
609.
72
4946
.46
5.5
3.8
<0.
1<
0.1
<20
<0.
1<
0.1
Ge
1.9
0.9
<0.
10.
3<
0.1
<0.
1<
0.1
<0.
10.
2<
0.1
<0.
1<
0.1
0.07
0.16
<0.
024.
5823
.7
1.05
25.1
As
<0.
10.
230.
270.
20.
320.
280.
190.
660.
280.
090.
150.
110.
120.
120.
140.
170.
12<
51.
32<
0.1
Ba
56.1
40.4
42.4
34.9
32.4
31.5
0.6
0.5
0.5
0.1
0.3
0.5
0.2
0.1
0.3
<0.
1<
0.1
<60
<0.
1<
0.1
Pb27
.25.
30.
40.
40.
60.
57.
417
3.4
5.8
9.7
9.1
8.4
4.3
27.1
0.16
0.18
<30
0.14
0.27
U3.
30.
46.
126
.123
.86.
716
.824
.85.
33
5.6
<0.
1<
0.2
<0.
2<
0.2
<0.
1<
0.1
<10
<0.
1<
0.1
Hydrochemistry and genesis of CO2-rich springs 523
*E.C
.: E
l ect
rica
l C
ondu
cti v
i ty,
**D
.O.:
Di s
sol v
ed O
xyge
n.
Sam
ple
No.
P1P2
1P2
2P3
P4P8
1P8
2P9
P10
P11
P12
P13
P14
P16
D1
D2
D3
D4
D5
D6
D7
pH6.
445.
315.
325.
225.
435.
195.
755.
655.
605.
805.
605.
876.
416.
246.
036.
266.
255.
896.
136.
116.
17E
h (m
V)
100
107
9329
5757
1014
719
9−2
5−2
34
58−8
.1−8
9928
349
*E.C
. (µ S
/cm
)17
0542
255
913
9198
862
515
2011
5614
5290
814
4222
8017
3610
4520
1030
0031
0014
4225
7023
8026
50
Tem
p (°
C)
25.8
13.4
11.5
2.9
11.3
8.2
12.9
10.1
7.9
8.6
10.8
1411
.216
.712
.113
1010
.19.
68.
510
.6
PC
O2
(atm
)0.
494
1.00
1.46
5.21
2.41
2.83
1.88
1.75
2.44
0.92
52.
232.
230.
461
0.31
60.
120.
959
0.96
10.
914
0.37
50.
939
1.00
(uni
t: m
g/L
)**
D.O
.1.
30.
70.
32.
60.
31.
80.
40.
90.
82.
62.
31.
84.
72.
00.
72.
13.
00.
81.
21.
81.
7N
a91
.917
.331
.748
.944
.625
89.5
23.2
81.6
10.9
36.0
9786
.041
.880
.214
2.2
153.
962
.311
8.2
107.
114
8.1
K2.
708.
407.
2016
.83.
9022
.04.
1024
.62.
600.
8016
.84.
704.
502.
662.
76.
87.
84.
95.
17.
25.
8C
a37
6.0
27.8
59.0
361.
019
1.0
113.
027
9.0
235.
028
6.0
241.
035
5.0
521.
040
0.0
146.
331
9.4
394.
541
3.2
176.
434
7.8
295.
728
1.0
Mg
40.2
22.9
28.8
12.2
31.1
30.6
68.4
56.3
56.3
14.8
37.6
87.1
5431
56.9
102.
711
0.4
48.9
9383
133
Si61
.737
.536
.037
.237
.732
.433
.040
.924
.622
.135
.742
.124
.818
.832
.643
.645
.229
.537
.130
.433
.0H
CO
315
7925
538
112
4684
957
214
0710
5313
5477
913
5822
6316
2466
316
0523
9524
7794
019
2516
9320
59S
O4
12.3
7.14
13.1
15.4
15.0
22.7
11.2
14.8
17.1
15.0
7.97
14.0
31.5
38.4
26.1
33.8
35.3
38.1
34.8
38.6
27.2
Cl
14.1
1.3
2.6
5.1
8.0
4.8
7.5
6.5
6.7
6.4
8.8
8.6
8.3
21.3
16.0
25.4
28.0
19.0
25.0
27.0
23.6
F1.
60N
.D.
N.D
.1.
41N
.D.
N.D
.N
.D.
N.D
.N
.D.
N.D
.0.
74N
.D.
N.D
.0.
731
0.7
0.7
0.6
0.6
0.7
1.1
NO
3N
.D.
6.6
N.D
.N
.D.
N.D
.N
.D.
N.D
.N
.D.
N.D
.N
.D.
N.D
.N
.D.
N.D
.N
.D.
0.1
0.1
0.1
10.2
2.6
480.
1Fe
7.2
48.7
34.6
17.6
16.2
6.2
11.9
12.8
7.50
N.D
.18
.06.
70N
.D.
2.54
1.5
15.8
2.4
1.3
0.9
0.3
0.9
Sr1.
770.
360.
522.
431.
051.
404.
691.
755.
941.
033.
063.
671.
811.
251.
271.
681.
780.
571.
491.
361.
66
(uni
t: µg
/L)
Li
950
65.0
122
96.4
151
53.9
353
87.5
232
21.3
118
371
186
264
152
347
442
170
305
272
551
Al
0.26
N.D
.N
.D.
0.39
0.17
0.20
0.27
0.17
0.19
0.16
0.27
0.35
0.24
2739
5046
196
3531
64C
r22
.414
.420
.832
.925
.015
.721
.018
.626
.217
.64.
4925
.860
.783
611
951
.295
.545
.710
6.2
97.8
213.
6M
n0.
481.
030.
901.
411.
771.
101.
370.
521.
220.
012.
151.
201.
9615
683
718
752
591
755
950
918
Cu
54.0
10.9
45.2
18.4
44.2
47.1
32.2
33.5
25.2
31.2
35.5
8.71
8.28
836
35.4
6.7
32.
32.
32.
81.
4Z
n74
.935
.539
.717
.460
.411
169
.534
.729
.817
.966
.735
.630
.833
35.7
21.4
21.6
250
21.7
142.
316
.2G
e3.
973.
982.
771.
871.
570.
491.
201.
090.
690.
251.
551.
040.
561.
2
As
1.48
2.77
N.D
.0.
899.
562.
3716
.38.
60.
401.
542.
870.
931.
722.
729
.564
.245
.84.
415
4.3
119.
7B
a0.
125.
904.
572.
987.
816.
202.
421.
503.
691.
132.
292.
462.
6114
179
531
917
511
614
819
114
8Pb
1.37
1.32
0.86
0.41
2.71
2.33
1.97
1.56
N.D
.1.
191.
23N
.D.
N.D
.1.
60.
50.
60.
20.
20.
10.
20.
2U
1.06
0.18
0.06
0.37
0.11
0.35
4.94
1.33
18.4
4.31
23.9
8.21
0.36
2.3
Sam
ple
No.
S1S2
S3S4
S5S6
S7S8
G1
K1
K2
K3
K4
K51
K52
K6
K7
K91
K92
K93
K10
K11
pH6.
296.
136.
186.
156.
476.
346.
306.
215.
995.
195.
485.
555.
846.
015.
735.
815.
475.
255.
775.
845.
935.
64E
h (m
V)
126
138.
4−2
3−5
.130
2626
.2−2
.870
−80
112
580
045
211
670
22−6
276
*E.C
. (µS
/cm
)12
4223
8024
6017
6324
1128
1010
9318
0117
9410
5095
875
769
617
9522
3010
7316
1239
788
014
2117
3381
9
Tem
p (°
C)
14.8
14.1
15.3
14.3
15.3
15.8
1616
.214
.57.
87.
411
.79.
811
.512
.310
.622
.37.
87.
412
.511
.79.
8
PC
O2
(atm
)0.
598
1.01
00.
934
0.66
80.
485
0.73
60.
290
0.65
00.
864
4.78
2.28
1.48
0.78
71.
132.
671.
162.
831.
370.
971
1.35
1.52
1.19
(uni
t: m
g/L
)**
DO
4.5
1.6
1.6
1.5
3.0
0.8
2.9
1.2
1.1
1.2
0.8
1.2
1.7
1.8
1.8
1.4
1.2
2.1
3.5
1.4
1.8
1.0
Na
122
205
213
166
213
225
6213
779
35.3
14.1
79.0
10.8
376
485
240
283
6.63
11.3
34.4
51.5
20.3
K3.
66.
67.
96.
67.
06.
64.
14.
54.
52.
361.
633.
372.
9123
.727
.25.
9415
.50.
420.
512.
764.
082.
38C
a11
5.9
281.
327
014
226
932
111
720
224
916
115
283
.781
.349
.362
.311
.146
.964
.916
828
032
613
5M
g38
.166
.569
.854
.169
.110
1.6
36.4
50.7
40.3
36.0
37.1
7.76
37.9
2.15
2.38
0.43
1.59
9.19
18.3
25.7
2.91
15.3
Si16
.735
34.8
15.7
36.9
28.3
17.3
24.2
45.8
15.5
17.0
15.3
23.6
38.1
39.3
34.2
38.2
23.9
29.4
33.2
43.7
32.3
HC
O3
833
1797
1834
1196
1856
2115
702
1324
1080
793
732
549
513
1233
1559
778
882
247
610
1031
1357
549
SO
424
.433
.829
.533
.931
1437
31.6
21.2
4.05
7.25
12.1
6.75
11.6
21.5
3.9
27.6
11.1
10.1
18.0
10.5
10.8
Cl
24.3
29.0
29.0
29.0
28.0
32.0
32.0
28.0
24.1
3.50
4.15
7.55
5.00
9.10
12.2
6.20
11.1
3.90
4.60
5.05
6.40
5.60
F1.
10.
70.
50.
40.
050.
050.
60.
71.
81.
551.
556.
002.
057.
056.
409.
607.
154.
855.
053.
205.
104.
80N
O3
2.3
0.3
0.1
0.1
0.1
0.6
0.1
0.1
0.3
N.D
.N
.D.
N.D
.N
.D.
N.D
.N
.D.
N.D
.N
.D.
N.D
.N
.D.
N.D
.N
.D.
N.D
.Fe
1.0
2.7
2.7
4.5
3.6
1.1
5.2
2.9
31.5
11.4
20.1
8.47
24.3
6.34
5.92
4.74
12.4
7.51
18.8
14.5
54.0
28.7
Sr0.
521.
291.
541.
431.
331.
970.
450.
680.
812.
383.
292.
714.
761.
683.
671.
853.
764.
126.
7810
.95.
495.
53
(uni
t: µg
/L)
Li
149
531
621
275
605
595
125
327
159
A
l4
1824
530
166
6845
4<
0.1
<0.
10.
28<
0.1
1.15
0.57
0.19
0.53
0.45
0.41
0.17
0.88
0.55
Cr
36.5
92.3
129
68.1
111
143
26.5
8645
.8
Mn
276
672
780
302
710
668
710
865
808
0.92
0.64
0.77
0.55
0.45
0.46
0.46
0.66
0.70
1.38
1.36
2.61
1.15
Cu
2.4
2.3
1.2
1.3
1.6
21.
71.
12.
4<
0.06
<0.
06<
0.06
<0.
06<
0.06
<0.
06<
0.06
<0.
06<
0.06
<0.
06<
0.06
<0.
06<
0.06
Zn
162
25.2
25.8
12.1
28.8
39.8
25.8
50.9
103
0.05
0.18
<0.
040.
09<
0.04
<0.
040.
060.
07<
0.04
<0.
04<
0.04
<0.
04<
0.04
As
1.4
10.4
19.5
5511
.67.
93.
522
.638
B
a15
314
115
210
713
212
612
310
942
Pb
0.2
0.2
0.1
0.1
0.1
0.1
0.2
0.1
1.1
524 C. H. Jeong et al.
or HCO3–. The partial pressure of the CO2 in the soda
water was computed using the WATEQ4F program (Balland Nordstrom, 1992), and is high (PCO2 0.12 to 5.21 atm).
In this paper, the chemical constituents of the CO2-rich waters were classified from the viewpoint of theirhost rocks and the region of their occurrence. The CO2-rich waters were classified into five groups according tohost rocks which can control the chemical compositionof soda water: (1) The springs in granite area are the MM,CM-series, P4, P10, P11, K1, K2, K51, K52, K6, K7, K81,K82 and K9; (2) The springs in the gneiss and meta-sedi-mentary rock area are K4 and K10; (3) The springs inwhich host rocks are both granite and gneiss are BM, DM-series, AH-series, P21, P22, P3, K3 and K11; (4) Thesprings in which host rocks are both granite and sedi-mentary rocks are P1, P4, P6, P81, P82, P9, P12, P13,
cc kw kp0
100
200
300
400
500
Na+
K(m
g/L)
cc kw kp0
100
200
300
400
500
600
Ca+
Mg(
mg/
L)
cc kw kp0
500
1000
1500
2000
2500
HC
O3(
mg/
L)
cc kw kp
0
2
4
6
8
10
F(m
g/L)
cc kw kp-10
10
30
50
Fe(m
g/L)
cc kw kp
0
2
4
6
8
10
Sr(
mg/
L)gr gr/gn gr/sed
0
100
200
300
400
500
Na+
K(m
g/L)
gr gr/gn gr/sed0
100
200
300
400
500
Ca+
Mg(
mg/
L)
gr gr/gn gr/sed0
500
1000
1500
2000
2500
HC
O3(
mg/
L)
gr gr/gn gr/sed
0
2
4
6
8
10
F(m
g/L)
gr gr/gn gr/sed
0
10
20
30
40
50
Fe(m
g/L)
gr gr/gn gr/sed
0
2
4
6
8
10
Sr(m
g/L)
Fig. 6. Box-Whisker Diagram of the concentration of major ions of CO2-rich water according to host rocks and occurrence area.cc: Chungcheong area, kw: Kangwon area, kp: Kangwon area, gr: granite, gn: gneiss, sed: sedimentary rocks.
P14 and P15; (5) The springs in the sedimentary rock areaare P7-series and P16. The discharge of CO2-rich springsin South Korea can be largely grouped as three regions:the Chungcheong regions (BM, MM, DM, CM-series, AH-series), the Kangwon regions (K-series) and theKyungpook regions (P-series).
The Box-Whisker diagram of major ions (Ca2+ + Mg2+,Na+ + K+, HCO3
–, F, Fe and Sr) in the CO2-rich waterswas made to show the variation of chemical compositionof soda water according to the host rocks and their occur-rence region (Fig. 6). Ca, Mg, Na and HCO3 in soda wa-ter were the dominant inorganic constituents. Fe, Sr andF as minor elements are also abundant in CO2-rich wa-ters.
The CO2-rich water from the Kyoungpook regionshows the highest Ca2+ + Mg2+ and HCO3
– contents. Fe,
Hydrochemistry and genesis of CO2-rich springs 525
Ca NO3+ Cl
Kyungpook areaChungcheong area
Kangwon area
Fig. 7. Tril inear diagram of major ion composit ion(miliequivalents) of CO2-rich water.
samples at three springs (D2, D7, S4) exceed the statu-tory permissible limit of As for drinking waters.
The major ions of the CO2-rich water have been plot-ted on a trilinear diagram (Fig. 7). The CO2-rich water isclassified by three chemical types on the Piper diagram(Piper, 1944): Ca-HCO3, Ca(Na)-HCO3 and Na-HCO3type. Most of the CO2-rich water belongs to the Ca-HCO3type. A few of the soda waters from the Kangwon regionbelong to the Na-HCO3 type. Some soda waters of theKyoungpook and the Kangwon regions are plotted on thearea of Ca(Na)-HCO3 type.
Oxygen and hydrogen isotopesThe δ18O and δ2H values of the CO2-rich water show
a range of from –12‰ to –7.7‰ and from –86.8‰ to–50.4‰, respectively (Table 2). Figure 8 shows that allδ18O and δ2H data plot along or near the meteoric waterline of Craig (1961) and this indicates that all soda wa-ters are of a meteoric origin.
Records of the stable isotopic data of the local pre-cipitation were available from the database of IAEA sta-tion (Cheongju station) in South Korea. The Cheongjustation is located nearby a CO2-rich spring site (MM) inthe Chungcheong area. Twenty-six data of δ18O and δ2Hof precipitation from 1998 to 2000 were measured at thissite. The average values of δ18O and δ2H are –9.92‰ and–68.9‰, respectively. The level is in the middle of mea-sured isotope values of CO2-rich water.
The δ18O and δ2H values of the CO2-rich waters showa decreasing trend in the following order: Chungcheong(or Kyoungpook) and Kangwon. The relatively wide rangeof isotope values of CO2-rich waters reflects the latitudeand the recharge altitude effects of oxygen and hydrogenisotopes according to the location of the springs.
DISCUSSIONS
Mineral source of major ionsFigure 9 shows that the concentration of major ions
(Ca2+, Mg2+, Na+, K+, HCO3– and F–) of the CO2-rich
water except the DM-series samples is much higher thanthat of the CO2-free groundwater of commercial potablewater in South Korea (KIGAM, 1998). The concentra-tions of SO4
2– and Cl– ions show similar levels betweenCO2-rich water and CO2-free commercial groundwater.NO3
– contamination is recognized in the CO2-rich water.Most commercial groundwater is extracted from graniteand gneiss which are major host rock type for CO2-richsprings. Hence, it can be inferred that the CO2-rich waterhas evolved through a different water-rock interactionenvironment than commercial groundwater.
If CO2 gas dissolves in groundwater, it dissociates inthe aqueous solution and the pH of the solution generallybecomes lower. Through this process, CO2-rich waters
Sr and F concentrations are the highest in the CO2-richwater from the Kangwon region. The Na+ + K+ content inthe CO2-rich water from the Kyungpook region shows ahigher value than those of the Chungcheong and theKangwon regions.
The F, Fe and Sr contents in the CO2-rich waters fromthe granite and gneiss host rocks are higher than thosefrom the sedimentary host rocks. Otherwise, the concen-tration of Ca2+ + Mg2+ and HCO3
– in soda water from thesedimentary host rocks is higher than that of the graniteand gneiss rocks. The Na+ + K+ content in the CO2-richwater from sedimentary rocks is higher than that of gneissand granite rocks.
The contents of SO42– and Cl– in CO2-rich water show
ranges of 0.6~38.6 mg/L and 1.3~32.0 mg/L, respectively.These ranges are similar to those of CO2-free groundwaterin granitic and gneissic rocks in Korea (KIGAM, 1998).
Most of CO2-rich waters show a high iron content.Levels range from 0.12 to 54 mg/L. In particular, K4, K10,K11, P21 and P22 samples have a very high content ofabove 24 mg/L. Iron in CO2-rich water is precipitated asa reddish FeOOH after exposure to air. The concentra-tions of Sr and Mn also range from 0.1 to 10.9 mg/L, andfrom 0.001 to 2.73 mg/L, respectively. Most of CO2-richwaters in the Kangwon and Kyoungpook regions showhigh Sr concentrations. However, Mn concentration ishigh in several samples (BM, CM2, AH2, AH3, AH4,AH5) in the Chungcheong region. Arsenic is a toxic ele-ment and it constitutes a health hazard in high concentra-tions. In Korea, the maximum acceptable concentrationof As in drinking water is 50 ppb. The CO2-rich water
526 C. H. Jeong et al.
0.000
0.001
0.010
0.100
1.000
10.000
100.000
K Na Ca Mg HCO3 Cl SO4 F NO3 Fe
Max
Min
Ave
(A)
0.000
0.001
0.010
0.100
1.000
10.000
100.000
K Na Ca Mg HCO3 Cl SO4 F NO3
Max
Ave
Min
(B)
x
Fig. 8. δ18O versus δ2H relationship of the CO2-rich water.
Fig. 9. Schoeller diagram showing the level difference betweenmajor ions of CO2-rich water (A) and those of CO2-free com-mercialized mineral water from South Korea (B).
-100
-80
-60
-40
-20
-14 -12 -10 -8 -6 -4
δ 18O(V-SMOW, ‰)
δD(V
-SM
OW
, ‰)
KangwonChungcheongKyungpook
show a weakly acidic condition with pH 4.8 to 6.76. Thisreaction also produces abundant HCO3
– in the CO2-richwater. The weakly acidic water can drive the weatheringprocess continuously in the water-rock reaction system.Hence, the supplying of CO2 gas to groundwater continu-ously results in a high dissolved ion concentration in CO2-rich waters.
The dissolution of carbonate minerals and CO2 gasplayed a major role in supplying Ca2+, H2CO3
o and HCO3–
to the soda water:
Ca(Mg)CO3 + CO2 + H2O ↔ Ca2+ + (Mg2+) + 2HCO3–.
(1)
The Na+ and K+ in the soda water chiefly originatedfrom the incongruent dissolution of plagioclase and po-tassium feldspar in the granite, gneiss and sedimentaryrocks:
(K,Na,Ca)Al2Si2O8 + H2O + 2H+ ↔feldspar
Al2Si2O5(OH)4 + (K+,Na+,Ca2+). (2)kaolinite
Reaction (2) can also be one of the main sources ofCa in soda water. The carbonate mineral can be locallypresent in joints of granite and gneiss rocks (KARICO,1998). It can also occur as secondary precipitates. In thinsections, carbonate minerals as the replacement ofplagioclase were observed in granite and gneiss rocks.The sandstone and shale of the Cretaceous sedimentaryrocks contain carbonate minerals as interstitial materialsuch as cement and matrix formed during the diagenesisand as a replacement for plagioclase. The chemical com-position of carbonate minerals in sedimentary rocks was
obtained by microprobe analysis. Figure 10 shows thechemical composition of carbonate minerals plotted onthe calcite and dolomite area. The carbonate minerals alsoinclude Fe of about 20 molecular weight percent. Hence,it seems that the dissolution of the carbonate minerals isthe main contributor to the abundant Ca2+, Mg2+ and Fe(IIor III) in the CO2-rich water of the Kyoungpook area.
The CO2-rich water from AH-series deep wells in theChungcheong area, and CO2-rich water in the Kangwonarea are characterized by high contents of fluorine(4.1~9.6 mg/L). F– could basically have originated froma F-bearing mineral such as fluorite in the rocks. The mainsource of groundwater fluorine in granitic rocks is thedissolution of fluorine which exchanges hydroxyl ions ofmicaceous minerals and their clay products (Savage etal., 1987; Nordstrom et al., 1989; Apambire, 1997).
Hydrochemistry and genesis of CO2-rich springs 527
Origin of CO2 gasThe defining characteristic of the soda water is its high
CO2 content ranging from a PCO2 of 0.12 to 5.21 atm.CO2 pressure was calculated by using the WATEQ4F pro-gram. The mean atmospheric and soil CO2 pressures showlevels of 10–3.5 atm and 10–1.5~10–2.5 atm, respectively(Appolo and Postma, 1996). Since water that is saturatedwith carbon dioxide is continuously infiltrating throughsoils into the aquifer, the groundwater of organism-freeaquifer would have CO2 concentration below the soil equi-librium. Therefore, the high PCO2 of the soda water indi-cates that the CO2 gas in water samples has been sup-plied from an external source.
Carbon dioxide is discharged naturally from theEarth’s crust. CO2 in mineral springs may be derived froma variety of sources, including liberation of CO2 by meta-morphic processes, magmatic degassing, oxidation oforganic matter, and the interaction of water with sedi-mentary carbonates (Schoell, 1983; Chivas et al., 1983,1987; Griesshaber et al., 1992; Giggenbach, 1992;
Table 2. Isotopic data of water samples collected at CO2-rich springs in South Korea
Fig. 10. Diagram showing the chemical composition of car-bonate minerals in shale and sandstone of Cretaceous sedimen-tary rocks.
Sample No. δ18O
(V-SMOW, ‰)
δD
(V-SMOW, ‰)
δ13C
(PDB, ‰)
Sample No. δ18O
(V-SMOW, ‰)
δD
(V-SMOW, ‰)
δ13C
(PDB, ‰)BM −8.82 −61.9 −6.4 D2 −10 −67 −0.9
MM −8.62 −62.5 −6.5 D3 −10.09 −67 −2.8
CM2 −9.2 −55.8 D4 −9.48 −63 −1.1
CM3 −8.6 −59.8 −6 D5 −9.89 −66 −3
CM4 −9 −61.2 −6 D6 −9.75 −64
CM6 −8.4 −62.4 −5.9 D7 −10.13 −68
CM8 −8.8 −61.6 S1 −7.94 −54
DM1 −7.76 −57.5 −6.3 S2 −9.19 −63 −6.6
DM2 −7.88 −52.5 −5.4 S3 −9.23 −63.2
DM3 −8.16 −51.4 −5.1 S4 −9.33 −62
AH1 −10.42 −66.7 −3.1 S5 −9.48 −63.5 −6
AH2 −9.55 −67.5 −4.7 S6 −9.85 −64
AH3 −10.05 −67.4 −4.9 S7 −8.45 −56
P1 −10.1 −73 −2.6 S8 −9.32 −62.6
P21 −9.7 −67 −5.4 G1 −9.61 −64 −3.5
P22 −10 −67 −4.1 K1 −10.1 −69.3
P3 −9.9 −67 −1.8 K2 −9.8 −66
P4 −9.2 −66 −4.1 K3 −10.3 −71.1 −5.3
P81 −9.3 −61 −6.1 K4 −10 −68.8
P82 −10 −62 −3.7 K51 −10.3 −72 −4
P9 −9.5 −63 −3.9 K52 −10 −70.7
P10 −9.4 −65 −4.6 K6 −7.7 −50.4
P11 −8.6 −64 −4.5 K7 −12 −86.8 −0.3
P12 −9.1 −60 −3.5 K91 −10.95 −74.8
P13 −9.2 −61 −1.5 K92 −10.5 −72.8
P14 −8.6 −58 −2.8 K93 −11 −77.7
P16 −8.1 −56 −4.8 K10 −11 −78.7
D1 −9.48 −66 −6.6 K11 −11.2 −80.5 −5.6
528 C. H. Jeong et al.
Giggenbach and Corrales-Soto, 1992; Harris et al., 1997;Ceron et al., 1998; Cartwright et al., 2002).
In some instances, carbon and helium isotopes havebeen used to investigate the origin of CO2-rich ground-water. The relationship between helium and carbon wasapplied to elucidate the presence of mantle-derived CO2in groundwater as reported from some volcanic sites inGermany (Griesshaber et al., 1992). Ishibashi et al. (1995)suggested that the CO2-rich hydrothermal fluid in theOkinawa Trough Back Arc is related to rifting activitiesin the continental margin. It was reported that the CO2 ingroundwater from the Front Range fault in Colorado origi-nated from three different sources, i.e., magmatic,diagenetic and metamorphic origins (Mayo and Muller,1997). Schofield and Jankowski (1998) suggested that anexternal source of CO2 in Na-HCO3 groundwaters from afractured aquifer in the Ballimore region of Australia, ispresent. Cartwright et al. (2002) studied the carbon ori-gin of CO2-bearing mineral spring waters in Daylesford,Australia. They revealed that the carbon was derived froma mantle source associated with local Pliocence to Re-cent basaltic volcanic rocks.
The δ13C of atmospheric CO2 is known to be in therange of –6.4 to –8‰ PDB (Cerling et al., 1991). The
δ13C of soil CO2 is controlled by photosynthesis result-ing in the fractionation of carbon isotopes. Three princi-pal photosynthetic cycles are known: the C3 cycle, theC4 cycle and the CAM cycle (Clark and Friz, 1997). TheC3 pathway operates in about 85% of plant species anddominates in most terrestrial ecosystems, and also in veg-etation in the temperate conditions of Korea. Most C3plants have δ13C values ranging from –24 to –30‰ withan average value of about –27‰ (Vogel, 1993). The CO2derived from marine limestones (δ13C values typically~0‰) will have a δ13C value close to zero. For example,CO2 gas derived from dissolution of limestones in Natal,South Africa has δ13C values of –0.6 to –0.9‰ (Harris etal., 1997). Mantle-derived carbon has a δ13C of –8‰ to–5‰ (Deines, 1970; Kyser; 1986; Sheppard, 1986). Atigneous temperatures, the 13C fractionation between car-bon contained in magma and CO2 is ~ –2‰ (Sheppard,1986). If all CO2 degasses, the δ13C values will be –6‰.Hence, CO2 derived from a magmatic source is predictedto have δ13C values of –6‰ (or higher than –6‰).
In this study, the δ13C values of the CO2-rich watersamples range from –6.6 to –0.3‰ (Table 2). These δ13Cvalues could be reflecting carbon from multiple sources.The δ13C values suggest that the CO2 gas in mineral wa-
Fig. 11. Relationship between δ13C and major components of the CO2-rich water. Symbols are same in Fig. 10.
Hydrochemistry and genesis of CO2-rich springs 529
ter is mainly derived from deep-seated sources such asmagma and the mantle, and is partly contributed by thedissolution of carbonate minerals and the oxidation oforganisms.
The diagrams of δ13C versus major components (PCO2,Ca + Mg, Na + K, HCO3) of CO2-rich water samples arepresented in Fig. 11. The relationship between δ13C andmajor components (PCO2, Ca+Mg, HCO3) shows a roughlypositive trend. This implies that the dissolution of car-bonate minerals supplies the inorganic carbon in addi-tion to the carbon of deep-seated origin in soda water,and contributes to the increase of the CO2 pressure inwater. However, the relationship between δ13C and Na +K concentration is not distinct.
δ18O value against PCO2 level is plotted in Fig. 12.Their relationships show a negative trend in the case ofthe samples from the Kangwon and the Chungcheong area.However, the sample of the Kyungpook area does notshow a clear relationship. Although the variation of δ18Ovalues of CO2-rich waters has a latitude effect, it can bethat lower isotope values of CO2-rich waters indicatedeeper circulating groundwater. AH-series, P1 and K7samples, which are CO2-rich waters pumped from deepwells, show the low isotope values. Hence, it seems thatdeep circulating groundwater can greatly dissolve CO2gas of deep-seated source.
CONCLUSIONS
Many CO2-rich springs are focused in Mesozoicgranitoids and surrounding rocks in South Korea. Thedischarge of CO2-rich springs from the Chungcheong andthe Kyoungpook provinces in South Korea show a closerelationship with the geologic structures, i.e., the geologicboundary, fault zone and dyke swarms. These geologicalstructures could act locally as a conduit for deep CO2 torise to the surface. However, most of CO2-rich springsfrom the Kangwon province do not show a clear relation-ship between their occurrence and geologic structures.
Oxygen and hydrogen isotopic data indicates that theCO2-rich waters are of meteoric origin. The carbon iso-tope data indicates that high content of CO2 gas of thesoda waters is mainly attributable to a deep-seated source,but is partly mixed with CO2 derived from carbonate min-erals. The formation process of CO2-rich springs is asfollows. After the CO2 gas from a deep-seated sourceenters into the groundwater system along the faults orthe geologic boundaries, it mixes into the groundwater.The CO2-rich water evolves into weakly acidic ground-water of three chemical water types (Ca-HCO3 water,Ca(Na)-HCO3 water, and Na-HCO3 water) depending onthe aquifer rock types.
Carbonate minerals as secondary precipitates and in-terstitial fillings in Cretaceous sedimentary rocks are the
main source of abundant Ca, Mg, HCO3 and Fe in theCO2-rich waters of the Kyungpook region. In theKangwon and the Chungcheong regions, carbonate min-erals locally present in the fractures of granite and gneisswould be one of the main sources of abundant Ca, Mgand HCO3 in the CO2-rich water.
It is necessary to study further the helium isotope ofthe samples in order to clearly determine the externalsource of the CO2 gas and the genetic relationship be-tween the discharge of CO2-rich springs and Mesozoicgranites.
Acknowledgments—This work was supported by a grant (R01-2004-000-10759-0) from the Basic Research Program of theKorea Science and Engineering Foundation. Isotope and cationanalyses of CO2-rich water samples were carried out in KoreaBasic Science Research Institute.
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