Diagenetic and other highly mineralized waters in the Polish Carpathians

Applied Geochemistry 24 (2009) 1889–1900

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Diagenetic and other highly mineralized waters in the Polish Carpathians Andrzej Zuber *, Józef Chowaniec Polish Geological Institute, Carpathian Branch, PL-31560 Kraków, ul. Skrzatów 1, Poland

a r t i c l e

i n f o

Article history: Received 18 March 2009 Accepted 3 July 2009 Available online 10 July 2009 Editorial handling by W.M. Edmunds

a b s t r a c t Highly mineralized waters of different chemical types and origin occur in the flysch formations and their bedrocks in the western part of the Polish Carpathians. The marine sedimentation water of the flysch formations is not preserved, as the most mineralized and the heaviest isotopic values of flysch waters are characterized by d18O and d2H values in the ranges of 5–7‰ and (20–30)‰, respectively. Their origin is related to the dehydration of clay minerals during burial diagenesis, with molecules of marine water completely removed by molecules of released bound water. They are relatively enriched in Na+ in respect to the marine water, supposedly due to the release of Na+ during the illitization of smectites and preferable incorporation of other cations from the primary brine into newly formed minerals. In some parts of younger formations, i.e. in the Badenian sediments, brines occur with isotopic composition close to SMOW and Cl contents greatly exceeding the typical marine value of about 19.6 g/L, supposedly due to ultrafiltration. Most probably, the marine water of the flysch formations was similarly enriched chemically in its initial burial stages. Final Cl contents in diagenetic waters depend on different Cl contents in the primary brines and on relationships between diagenetic and further ultrafiltration processes. In some areas, diagenetic waters migrate to the surface along fault zones and mix with young local meteoric waters becoming diluted, with the isotope composition scattering along typical mixing lines. In areas with independent CO2 flow from great depths, they form chloride CO2-rich waters. Common CO2-rich waters are formed in areas without near-surface occurrences of diagenetic waters. They change from the HCO3–Ca type for modern waters to HCO3–Mg–Ca, HCO3–Na–Ca and other types with elevated TDS, Mg2+ and/or Na contents for old waters reaching even those of glacial age. Bedrocks of the flysch are represented by Mesozoic and Paleozoic mudstones, sandstones and carbonates, and in some areas by Badenian sediments. Brines of the Mesozoic and Paleozoic bedrocks are usually significantly enriched in Ca2+ and Mg2+ in comparison with the Badenian brines. By analogy to the deepest brines in the adjacent Upper Silesian Coal Basin, they are supposed to originate from paleometeoric waters of a hot climate. Ó 2009 Elsevier Ltd. All rights reserved.

1. Introduction In the western part of the Polish flysch Carpathians there are many occurrences of highly mineralized waters of different types. Some of them are used for medical purposes or production of bottled waters; their origin being of importance for determining available resources, and for proper management. Particularly interesting is the origin of numerous near-surface occurrences of Cl and chloride CO2-rich waters in the flysch formations, which have no isotopic signatures of the primary sedimentation brines. The heaviest isotopic values of these waters are characterized by d18O and d2H values in the ranges of 5–7‰ and (20–30)‰, respectively. Similar waters in the California Coast Range were regarded by White et al. (1973) as a result of the dehydration of clay minerals in low-temperature metamorphism. From known isotopic compositions of clay minerals and * Corresponding author. Tel.: +48 12 4113822102. E-mail address: [email protected] (A. Zuber). 0883-2927/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.apgeochem.2009.07.002

isotopic fractionation factors, the calculated ranges of dehydration waters in equilibrium with metamorphic rocks are from 4.5‰ to 25‰ for d18O and from 20‰ to 65‰ for d2H (Taylor, 1974, 1977; Kharaka and Carothers, 1986; Longstaffe, 1987; Kerrich, 1987). However, neither these nor any other later authors dealing with similar waters were able to explain reasonably significant differences in Cl contents from about 1 to more than 20 g/L in spite of nearly constant isotope composition. A metamorphic origin for the Carpathian waters can be excluded because flysch formations were formed in the process of burial diagenesis at temperatures below 200 °C (S´wierczewska, 2005; S´rodon´, 2007), and they do not contain any metamorphic signatures. According to Longstaffe (1987), ‘‘clay dewatering and isotopic exchange with clay minerals during burial” is one of four main processes responsible for isotopic composition of waters in large sedimentation basins, which ‘‘pertains mostly to smectite and illite/smectite dominated shales”. Similarly to the definition of metamorphic waters, waters released from or being in equilibrium with diagenetic rocks can be termed diagenetic waters.

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The earliest opinions related the Cl waters of flysch formations to the remnants of marine sedimentation waters on the basis of chemical data. Trying to solve the problem of different Cl contents in dehydration waters of the Carpathian flysch, which are characterized by similar isotopic composition, Les´niak (1980), Dowgiałło (1980) and Dowgiałło and Les´niak (1980) proposed a mixing model. In that model, the isotope and Cl contents of the actually observed non-meteoric component were supposed to result proportionally from the marine water and metamorphic water with d18O values above 20‰. Such values result from the dehydration of clay minerals during high-temperature metamorphism. The primary mixing was assumed to take place on a regional scale between marine sedimentation water of flysch and/or Miocene formations with non-mineralized metamorphic water. The secondary mixing between that end member and meteoric waters of different ages is of local character as observed in numerous springs and wells. Zuber and Grabczak (1986) regarded the end member of Cl waters of the Polish flysch Carpathians to result only from the dehydration of clay minerals in metamorphic processes, these waters migrate to the ground surface and mix with local meteoric waters. Zuber (1987) and Oszczypko and Zuber (2002) excluded metamorphism as the source of dehydration water and suggested the diagenesis of clay minerals, in which enrichment of Na+ occurs. However, the origins of highly different Cl concentrations in

waters with similar isotopic composition still had no satisfactory explanation. The aim of the present work is to present new ideas on the origin of Cl waters in flysch formations in relation to other highly mineralized waters in the western part of the Polish Carpathians. Special attention is devoted to the explanation of mechanisms which lead to the similar isotopic composition of their end members in different areas in spite of highly different Cl contents. Hypotheses on the origin of highly mineralized waters in the bedrocks of flysch formations are also presented. 2. Geology and hydrogeology of the study area The study area covers the western part of the Polish Western Carpathians which are divided into the Inner and Outer Carpathians (Figs. 1 and 2). The Inner Carpathians include the Tatra Mountains, the Podhale Basin and the Pieniny Klippen Belt which separates the Inner and Outer Carpathians. Available resources of fresh water occur in Quaternary sediments of main river valleys, and also in the uppermost flysch layers which are weathered to a depth of several meters, and usually fractured to depths of 50– 100 m. An exception exists in the Tatra karstified carbonate series of the Inner Carpathians where fresh waters occur to depths of 500–1000 m (Fig. 2). Within the Tatra Mountains the waters are modern as indicated by the presence of 3H (Zuber et al., 2008)

Fig. 1. Geology of the study area with the structural units and positions of sampling sites.

A. Zuber, J. Chowaniec / Applied Geochemistry 24 (2009) 1889–1900

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Fig. 2. The hydrogeologic cross-section with the schematic projections of ascension paths of diagenetic waters and CO2.

whereas at greater depths, under the cover of impermeable thick flysch sediments of the Podhale Basin, they are much older, becoming warmer, up to ca. 100 °C, and mineralized up to 3 g/L (Chowaniec, 2009). The Pieniny Klippen Belt is an impermeable obstacle for these thermal waters as it is composed of Paleozoic and Mesozoic carbonates, weathered and karstified only in the uppermost elevated parts, and low permeability flysch formations. The Outer Carpathians are built of Cretaceous and Paleogene flysch formations (shales and sandstones of different thickness) which were overthrust from the south and folded in a number of orogenic cycles in the Paleogene and Neogene up to the late Miocene. As a consequence, in some regions the flysch formations overlie Badenian marine sediments, and in the north-western part of the area also underlie them. In most of the area, the flysch formations cover older Mesozoic and Paleozoic mudstones, sandstones and carbonates. Surface and near-surface occurrences of highly mineralized waters are mainly related to the largest overthrust unit, the Magura Nappe, though springs with chloride CO2-rich waters are also known within the Pieniny Klippen Belt (No. 9). The most abundant resources of common (i.e. non-Cl) CO2-rich waters are observed along the valleys of the Poprad river and several of its tributaries (Nos. 1, 2, 4–6), where the structure of the flysch formations is so complicated by folds and faults that wells drilled for fresh water often find highly mineralized water, and vice versa. Deep-seated CO2 is of metamorphic origin as indicated by d13C(CO2) values close to 1‰ (Les´niak, 1985), though some contribution of magmatic CO2 is possible as suggested by 3He/4He data (Les´niak et al., 1997). Surface occurrences of chloride CO2-rich waters are known in several areas (e.g. Nos. 7, 8 and 9 in Poland, and in Cigelka and Bardejov in Slovakia near the Polish border). Surface occurrences of Cl waters without free CO2 are also known (Nos. 12, 13, 14, 16 and 19). Chloride waters were also found in deep wells in flysch formations (Nos. 10, 11, 14, 16–20), Miocene sediments (21–27),

and Paleozoic and Mesozoic carbonates and sandstones (20, 25– 27). Highly mineralized water has not been found so far in the flysch of the Podhale Basin, with a maximum thickness of about 3 km. Most probably, that lack of highly mineralized water is mainly caused by upward seepage of fresh water from the underlying Mesozoic carbonate formations during the last land period, which started during the final regression of the Badenian sea, i.e. about 12 Ma ago. The bedrocks of flysch are represented by Miocene (mainly Badenian) sediments and Mesozoic and Paleozoic sandstones, claystones, mudstones and carbonate rocks. Brines preserved in some areas of the Miocene formations have the isotopic composition close to the SMOW indicating their marine origin (Dowgiałło, _ 1973; Rózkowski and Przewłocki, 1974), whereas brines of Devonian and Carboniferous formations were not studied isotopically, with one exception suggesting its paleometeoric origin, identical with the deepest brines in the adjacent Upper Silesia Coal Basin (USCB) (Pluta and Zuber, 1995). 3. Methods All isotope analyses were performed at the well established laboratory of the Faculty of Physics and Applied Computer Sciences, AGH – University of Science and Technology, Kraków, in relation to the V-SMOW standard, with the uncertainty (1 SD) of 0.1‰ for d18O and 1‰ for d2H. Chemical analyses of samples, for which stable isotope data are available, were in most cases performed at several certified laboratories. Archival chemical data of waters found in wells drilled shortly after the Second World War are in most cases incomplete and available only in a simplified form of the Kurlov formula which reads as follows (e.g. Zaporozec, 1972):

G Sp M

Anions T pH Q Cations

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where G is the gas content in g/L, Sp represents one or more selected specific components with concentrations given in the upper scripts (formerly lower scripts were used) in g/L or mg/L, M (mineralization) stands for the total dissolved solids (TDS) with its content given in the upper script in g/L, Anions and Cations represent ion contents with concentrations greater than 1% in decreasing order of equivalent percentages given in the upper scripts, T is the temperature in °C, and Q is the outflow rate in m3/min, if applicable. G, Sp, T, pH and Q as well as percentages of major ion below 10% or 20% can be omitted if not needed. The Kurlov formula was chosen from available graphical methods of presentation of chemical data for the aims of the present work due to several reasons. That formula is well known and often used in countries of the post-Soviet block and its advantages are worth advertising to a global audience. These advantages are: simple presentations of major and minor components with a chosen degree of accuracy, information on trace components which are of importance for a process under consideration, and information on total mineralization (TDS), and if necessary also on temperature, pH and outflow rate if needed. Some archival data are available only in the form of that formula, which was also an important factor in considering its use. The molar ratio of Na+ to Cl often allows identifying the origin of salinity in highly mineralized waters as values close to 0.86 represent unaltered marine sedimentation water, close to 1.0 are characteristic for leaching of NaCl, and above 1.0 indicate the presence of diagenetic water released from clay minerals as shown farther. For the investigated waters, the molar ratio of Na+ to Cl does not differ by more than 1–2% from that calculated from the percentages of equivalents reported in the Kurlov formula. Chemical types of water (facies), which indicate ions exceeding 20% equivalents, are also directly seen from that formula. For stable isotope determinations, the majority of sites with CO2-rich waters were sampled many times over periods ranging from several to about 20 a. For multiple samples, median values are given; in most cases the scatter of individual analyses being not larger than 2–3 standard deviations of the analytical precision. Stable isotopes and Cl contents of chloride CO2-rich waters and near-surface Cl waters of flysch formations in most cases exhibit

variations along their two-component mixing lines. In such cases, chemical data of samples close to the median isotope values were chosen as representative examples. 4. Isotopic and chemical composition of waters Tables 1–4 contain examples of the chemical and isotope composition of highly mineralized waters within the study area with chemical data presented in the form of the Kurlov formula. For comparison, the chemical composition of ocean water is additionally given in Table 4, also in the form of the Kurlov formula. Chemical compositions of several important types of water discussed within this work are also given in a common way in Table 5. Table 5 also contains the values of such chemical indicators as Cl/Br, m(Na+/ Cl) and Cl/B. The first one is shown to be of little use for the studied waters whereas the next two are useful for the identification of diagenetic waters as postulated by Oszczypko and Zuber (2002). Selected examples of common CO2-rich waters and chloride CO2-rich waters are given in Tables 1 and 2, respectively. The common CO2-rich waters are understood to be those in which Cl contents are within the natural background of fresh waters whereas chloride CO2-rich waters are those with Cl content significantly exceeding the local background value, even if it is a small percentage of all anions. Table 3 contains examples of the chemical and isotope composition of Cl waters in flysch formations, which do not contain free CO2 whereas Table 4 contains examples of Cl waters in the bedrocks of flysch in comparison with ocean water. Table 6 contains chemical and some other data on Cl waters from flysch and bedrock formations for which no isotope data are available. 5. Origin of waters 5.1. Common CO2-rich waters in flysch formations The stable isotope contents of the common CO2-rich waters scatter along the world meteoric water line (WMWL) confirming their meteoric origin. Chosen examples can be divided into two main groups: (I) modern waters as indicated by significant pres-

Table 1 Isotopic and simplified chemical composition of common CO2-rich waters. No.

d18O (‰)

Site/well/depth (m)

d2H (‰)

Kurlov formulaa

73.0

0:68 CO1:6 2 M

72.6

2:3 CO2:7 2 M

3

I. Modern meteoric waters as indicated by stable isotopes and significant H contents 10.4 1a Krynicab/Jan/2.0

7

20 HCO73 3 SO4 Cl Ca69 Mg21 Na7 K1

1b

Krynicab/Main Spring/3.1

2a

Muszyna/Wapienne/0

10.8

73

2:1 CO1:9 2 M Ca

3a

Złockie/Z-III/70

10.6

74

2:0 3 4 CO1:4 2 M Ca80 Mg17 Na2 Fe1

4a

_ Zegiestów/Anna/1.2

10.5

73

2:4 CO2:8 2 M

Ca Mg Na Fe1

5a

Piwniczna/P-5/32

10.2

73

2:1 CO2:7 2 M

3 2 HCO95 3 SO4 Cl Ca40 Mg31 Na26 K2 Fe1

5b

Piwniczna/P-6/81

10.0

71

2:3 CO1:7 2 M

3 HCO93 3 SO4 Cl Ca46 Mg31 Na20 Fe1 K1

II. Meteoric waters of glacial age as suggested by stable isotopes and lack of 3H 12.3 1c Krynicab/K-10/425

85.9

0:001 8:7 3 CO2:2 M Mg47 Ca41 Na 10 2 HBO2 Fe1

2b

Muszyna/Antoni/120

11.6

82

0:034 8:8 M CO2:9 2 HBO2

HCO100 3 Mg71 Ca15 Na12 Fe1

3b

Złockie/Z-I/165

11.8

83

0:001 7:7 CO2:1 M 2 HBO2

HCO99 3 Mg46 Na32 Ca18 Fe3 K1

4b

_ Zegiestów/II/300

11.2

78.3

0:007 13:6 3 CO1:8 M 2 HBO2 Mg57 Na33 Ca8 K1

5c

Piwniczna/P-7/165

11.1

78.8

0:007 5:9 M CO2:0 2 HBO2

6

Zubrzyk/Z-3a/27

11.9

81.0

0:034 12:5 3 CO1:8 M 2 HBO2 Na67 Mg27 Ca4 K1

a b

10.6

Br, I, and HBO2 below the detection level if not given. Zuber et al. (1999); chemical data mostly from Jarocka (1976); other data from unpublished reports of I. Józefko and B. Porwisz.

1

HCO98 3 Cl Ca76 Mg16 Na6 K1 HCO99 3 77 15

Mg Na7

HCO96 SO2 Cl

2

HCO99 3 66 30 3

3

HCO99

HCO99

HCO98 3 Mg38 Na32 Ca28 K1 HCO99

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A. Zuber, J. Chowaniec / Applied Geochemistry 24 (2009) 1889–1900 Table 2 Isotopic and simplified chemical composition of chloride CO2-rich waters. No.

d18O (‰)

Site/well/depth (m)

d2H (‰)

Fa

Kurlov formula

I. Diagenetic waters without meteoric components 7a Wysowa/Aleksandra/100

6.5

30

1.0

0:22 0:005 I HBO0:99 M25:4 Na93 Ca35 K1 Mg1 CO1:7 2 Br 2

8a

Szczawa/well II/100

6.8

31

1.0

0:33 0:007 CO1:7 I HBO0:53 M26:9 Na88 Mg3 9 Ca2 K1 2 Br 2

9a

Szczawnica/Magdalena/3.45

5.0

32

1.0

II. Diagenetic waters mixed with local meteoric waters 7b Wysowa/well 14/50

3.1

38

0.8

34

HCO66 Cl

49

HCO51 Cl

47 HCO53 3 Cl 1 1 92 5

CO0:89 Br0:031 I0:008 HBO0:75 M26:3 Na 2 2

Mg Ca K

HCO66 Cl

34

0:017 0:004 I HBO0:81 M19:9 Na93 Ca34 Mg1 K1 CO2:1 2 Br 2

7c

Wysowa/well 13/36

1.6

50

0.5

0:010 0:002 CO2:4 I HBO0:44 M12:9 Na 2 Br 2

7d

Wysowa/spring Na Skrypinie/0

6.4

59

0.15

0:007 0:001 CO1:7 I HBO0:19 M7:6 2 Br 2

8b

Szczawa/well I/32

2.6

51

0.4

0:014 0:004 CO2:0 I HBO0:40 M16:5 2 Br 2

8c

Szczawa/Krystyna/5

4.6

58

0.2

0:02 0:004 CO2:2 I HBO0:12 M16:8 2 Br 2

8d

Szczawa/Hanna/8

5.2

61

0.3

0:010 0:002 CO1:8 I HBO0:27 M9:17 Na90 Ca35 K3 Mg2 2 Br 2

8d

Szczawa/spring Koci Zamek/0

9.1

71

0.07

0:004 0:0008 CO1:7 I HBO0:078 M3:7 2 Br 2

9b

Szczawnica/Stefan II/1.1

8.0

66

0.2

CO2:08 Br0:006 I0:002 HBO0:19 M6:9 2 2

9c

Szczawnica/Szymon/2.3

68

0.08

9.0

32 HCO68 3 Cl 4 93 2 1

Ca Mg K 24

HCO76 3 Cl Na88 Ca8 Mg2 K1 34 HCO66 3 Cl Na87 Mg7 Ca3 K2 47

HCO53 3 Cl Na92 K3 Ca3 Mg2 46

HCO54 Cl

34 HCO65 3 Cl 22 68 8

Na Ca Mg K1 39

HCO60 3 Cl Na80 Ca11 Mg8 K1

CO2:96 Br0:002 I0:0004 HBO0:07 M2:9 Na 2 2

32 HCO67 3 Cl 23 65 9

Ca Mg K2

III. Very old meteoric waters with non-meteoric component (Zuber waters) 6.9 1d Krynicab/Zuber-III/936

56

0.34

0:007 0:002 CO2:1 I HBO0:017 M29:2 2 Br 2

HCO91 3 Cl Na84 Mg8 Ca3 K2 Li1

3c

67

0.13

0:005 0:0005 CO2:4 I HBO0:04 M20:0 2 Br 2

6 HCO93 3 Cl Mg51 Na43 Ca4 Li1 K1

a b

Złockie/Z-VI/299

10.9

9

F, estimated fraction of non-meteoric component in mixture with meteoric water. Oszczypko and Zuber (2002); other data from unpublished reports of B. Porwisz, I. Józefko and M. Dulin´ski.

Table 3 Isotopic and simplified chemical composition of chloride waters in flysch formations. d18O (‰)

No./site/well/depth (m)

d2H (‰)

Fa

Kurlov formulab 4.39 Cl g/L, m(Na/Cl) = 1.47

I. Pure or nearly pure non-meteoric waters d,e _ 11/Cie˛zkowice/IG-1 /1100 14a/Rabka/18e/120

5.5 6.2

23 24

0.95? 1.0

14b/Rabka/IG-1c/967

5.9

24

0.97?

7.0

12

1.0

Br0:120 I0:016 M44:3

II. Non-meteoric waters with meteoric component 4.5 16a/Pore˛ba Wielkac/IG-1c/1898

27

0.90?

Br0:039 I0:01 HBO0:17 M21:9 2

19a/Sól/Sól-5

g,h

/1071

c

Br0:08 I0:016 HBO0:40 M25:4 2

94

Cl HCO63 Na97 Ca1 Mg1

Br0:065 I0:019 HBO0:35 M20:9 2 95

90

Cl CO10 3 Na98 K1

HCO43 96 3

Cl ðNaþKÞ Ca

67

Cl HCO30 3 Na99

12/Bies´nik/Łazienki Spring /0

2.7

53

0.45

13/Słona/Irytowski Springc/0

0.6

42

0.57

0.3

42

0.60

Br0:05 I0:008 HBO0:26 M15:8 Na96 Ca1 Mg31 K1 2

7.9

62

0.15

Br0:009 I0:001 M5:5

4.4

21

0.85

Br0:143 I0:008 HBO0:17 M40:1 2

3.8

23

0.80

1.7 1.3

30 39

0.70 0.50

13

0.4 dehydration + 0.6 marine

14c/Rabka/Warzelnia/50 15/Sidzina/spring 2f/0 19b/Sól/Slanicah/0 h

19c/Sól/Shaft /11 6 1.5

III. Sedimentation marine water mixed with diagenetic water 10/Krosnoc/McAllen-11/627 2.4 a b c d e f g h

Br0:02 I0:01 HBO0:30 M5:6 2

68

Cl HCO32 3 Na95 Ca3 Mg2 75

Cl HCO25

3 Br0:039 I0:016 HBO0:55 M8:4 Na97 Ca1 Mg 1 2 92

Cl HCO8

Cl94 HCO53 ðNaþKÞ92 Ca4 Mg3 Cl94 HCO53 Na96 Ca2 K1

93

Cl HCO63 3 1 96

Br0:120 I0:049 M36:1 Na

Ca K

97

Cl HCO3

3 Br0:088 I0:023 HBO0:09 M44:5 Na95 Ca3 Mg 1 2

F, fraction of non-meteoric water. Br, I, and HBO2 not measured if not given. After Dowgiałło (1980), situated about 70 km to the east of the study area. Les´niak (1980). Zuber and Grabczak (1985). Kleczkowski et al. (1979). Isotope data assumed to fit the mixing lines (see text). Rajchel et al. (2004); other data from unpublished reports of I. Józefko, and B. Porwisz.

ence of 3H and (II) glacial age waters (or in some cases perhaps also waters recharged at the highest altitudes in the area) as suggested by much lighter stable isotope composition than that of modern

waters, the lack of 3H, and elevated TDS contents. The second group is characterized by the most negative d18O and d2H values in the region as seen in Fig. 3, which in most cases are difficult

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Table 4 Isotopic and simplified chemical composition of waters in the bedrocks of flysch. d18O (‰)

No./site/well/depth (m) Ocean water

0.0

I. Marine sedimentation brines 21/Łapczycab/Ł-3/592–855

0.0

d2H (‰)

Lithology/stratygraphy

Kurlov formulaa

–

Br0:007 I0:00006 HBO0:018 M35:1 2

4

Sands/Badenian

Br0:16 I0:09 M182:5

0.0

100

Cl ðNaþKÞ91 Mg5 Ca4

23a/De˛bowiec/D-2/448

0.12

4.2

Sands/Badenian

Br

23b/De˛bowiec/S-3/533

0.06

3.9

Sands/Badenian

M36:4 Br0:14 I0:12 HBO0:046 2

0.0

+2

Sands/Badenian

M43:1 Br0:033 I0:12 HBO0:087 2

24b/Zabłocie/Tadeusz/1096

+0.3

1

Sands/Badenian

Br

II. Paleometeoric brines 20a/Ustron´b/U-3/1837

1.0

22

Limest., Dolomites/Devonian

M110 Br0:34 I0:01 HBO0:02 2

20b/Ustron´b/U-3a/1753

0.8

20

Limest., Dolomites/Devonian

M126 Br0:36 I:012 HBO0:025 2

24a/Zabłocie/Korona/671

a b

0:14 0:12

I

0:19 0:09

I

90

Cl SO94 Na77 Mg18 Ca3 K1

99 HBO0:11 M36:5 84Cl 8 7 2 Na Ca Mg

Cl99 Na83 Ca9 Mg7 Cl99 Na83 Ca9 Mg7 NH14

99 HBO0:054 M52:3 Na81 CaCl 10 2 Mg8 NH14

99

Cl Na62 Ca24 Mg12 K1 99

Cl Na63 Ca24 Mg11 K1

Br, I, and HBO2 not measured if not given. Isotope data after Zuber and Grabczak (1985), chemical data form unpublished reports of I. Józefko and B. Porwisz.

Table 5 Chemical data of selected waters. Parameter

pH () TDS (g/L) Na+ (mg/L) K+ (mg/L) Li+ (mg/L) NHþ 4 (mg/L) Ca2+ (mg/L) Mg2+(mg/L) Ba2+ (mg/L) Sr2+ (mg/L) Fe2+ (mg/L) Mn2+ (mg/L) Cl (mg/L) Br (mg/L) I (mg/L) HCO 3 (mg/L) SO2 4 (mg/L) HBO2 (mg/L) H2SiO3 (mg/L) CO2 (mg/L) m(Na+/Cl) () Cl/Br () B/Cl (%) d18O (%)V-SMOW d2H (%)V-SMOW

Site number 1b

1c

7a

8a

14a

1d

10

24b

20a

6.05 2.27 40 6 n.d. Trace 418 53 1.1 2.4 4.8 1.4 7.1 n.d. n.d. 1643 13

6.75 8.76 250 12.5 Trace n.d. 924 636 5.8 7.8 40 Trace 3.5 n.d. n.d. 6784 1

6.82 25.4 6900 129 10.5 n.d. 314 26 3 1.4 34 n.d. 3850 22 5.3 13,110 1

7.01 26.9 7670 23.2 15 12 116 430 2 20 2.1 0.05 6524 33 7.2 11,520 0.9

8.05 25.4 9300 54 16 8.4 80 48 13 30 1.8 0.06 13,852 80 16 1525a Trace

7.33 29.2 7000 325 26.5 14.5 208 378 <0.5 <2.5 55 Trace 1136 7.0 2.2 19,965 65

7.0 44.5 16,350 35 7.0 21 413 190 6 38 9 0.25 25,734 68 23 1470 33

6.8 52.9 17,000 100 4.0 88 1882 876 n.r. 105 12 1.1 32,354 186 106 135 n.d.

6.37 110 27,600 600 10 31 9433 2819 <0.5 480 11 0.2 68,089 344 135 95 466

Trace 68 2760 n.a. n.a. n.a. 10.6 72.6

Trace 91 2200 n.a. n.a. n.a. 12.3 85.9

990 14 1690 2.76 175 42 6.5 30

527 15 1740 1.81 198 20 6.8 31

395 7.1 n.m. 1.04 173 30 6.2 24

17 52 2060 19.4 162 3.7 6.9 56

78 10 n.m. 0.97 292 1 2.4 13

54 18 n.m. 0.82 173 0.38 0.3 1.0

21 11.7 n.m. 0.63 198 0.08 1.0 22

Chemical data after Jarocka (1976) and from unpublished reports of I. Józefko, and B. Porwisz. a And 22.5 mg/L of CO2 3 ; n.a., not applicable; n.d., not detected; n.m., not measured; n.r., not reported.

to explain without the hypothesis of recharge under cooler climate, _ i.e. more than 10 ka ago (Cie˛zkowski and Zuber, 1997; Zuber et al., _ ´ ski and Zuber, 2000). 1999; Rózan The mean 3H ages of modern CO2-rich waters range from several years for some small springs to several hundred years for other springs and wells (Zuber et al., 1999). Such waters are of the HCO3– Ca type with TDS contents below 3 g/L. Their HBO2 contents are usually below 1 mg/L. When mixed in springs and wells with older waters, they usually change to HCO3–Ca–Mg or HCO3–Ca–Mg–Na types (Chowaniec et al., 2009). Glacial age waters, and/or waters recharged at much higher altitudes than their outflows and thus at great distances away, have TDS contents distinctly exceeding 3 g/L. They are usually of one of the following types: HCO3–Mg, HCO3–Na, HCO3–Mg–Na, HCO3–Na–Mg, and HCO3–Mg–Na–Ca, with TDS contents above 5 g/L and measurable HBO2 contents. Elevated TDS contents in these older waters result from prolonged

water–rock interaction in the presence of CO2, whereas the relative increase of Mg2+ and Na+ contents presumably results from cation exchange with Ca2+, dominating initially in the youngest waters and continuously supplied by dissolution of carbonate minerals. That hypothesis is supported by the rather unusual chemical composition of water No. 6, which is of glacial age judging from its isotopic composition and high TDS content, and is characterized by a strong dominance of Na+ and Mg2+. 5.2. Chloride CO2-rich waters in flysch formations The most positive d18O values of chloride CO2-rich waters (group I in Table 2) are regarded as representative for the end members of metamorphic waters (White et al., 1973; Les´niak, 1980; Dowgiałło and Les´niak, 1980) or diagenetic waters (Oszczypko and Zuber, 2002). They are 3H free with low surface outflows or

1895

A. Zuber, J. Chowaniec / Applied Geochemistry 24 (2009) 1889–1900 Table 6 Simplified chemical composition and some other data of Cl waters in flysch and bedrock formations for which no isotope data are available. No./site/well/depth (m)

Lithology/stratygraphy

Kurlov formulaa

I. Chloride waters in flysch formations 16b/Pore˛ba Wielka/1/1833

Sandstones/Paleogene

M21:8 Br0:027 I0:01 HBO0:16 2

17/Skomielna Biała/IG-1/1487

Sandstones/Paleogene/

Cl Br0:01 I0:02 M11:1 NaþK 98

18/Wis´niowa/IG-1/1229

Sandstones/Paleogene

M18:8

20c/Ustron´/U-2/180–250

Sandstones/Cretaceous, Paleogene

Br0:013 I0:009 M2:0

20d/Ustron´/U-2/981

Sandstones/Cretaceous, Paleogene

20e/Ustron´/U-1/839–1005

Sandstones/Cretaceous, Paleogene

Br0:132 I0:067 M32:0

II. Chloride waters in bedrocks of flysch 20f/Ustron´/U-1/1182–1190

Sandstones/Carboniferous/

Br0:223 I0:020 M83

20 g/Ustron´/U-1/1306–1316

Limestones/Devonian/

20 h/Ustron´/U-2/1070

66

Cl HCO33 3 Na98

92

78

Cl SO15 4 ðNaþKÞ96 59

5 3 Cl HCO33 3 CO3 SO4 Na97 Mg2 85

Cl HCO14

3 Br0:116 I0:055 M24:2 Na92 Mg4 Ca 3 82

6 Cl SO12 4 HCO3 Na86 Ca8 Mg4

98

Cl Na60 Ca40 98

Br

0:207 0:015

Sandstones + Limestones/Carboniferous + Devonian

Br

0:207 0:015

22/Hermanice/H-2/818

Sands/Badenian

Br0:35 I0:016 M112

22a/Hermanice/H-1/828

Sands/Badenian

Cl Br0:293 I0:016 M86:5 Na70 Ca 18 Mg11

25a/Jaworze/IG-1/1170–1432

Conglomerates/Badenian/

Cl M99 Na67 Ca Br0:299 I0:014 HBO0:040 22 2 Mg 10

25b/Jaworze/IG-2/1563

Congl., Limest., Dolom./Badenian + Devonian

26a/Ke˛ty/Kt-1/868–874

Sands/Badenian

I

26b/Ke˛ty/Kt-1/1266

Sandstones/Carbonifeous

I0:011 M31

27a/Borze˛ta/IG-1/1511

Sands/Badenian

Br0:048 M11:3

27b/Borze˛ta/IG-1/2216

Limestones/Jurassic

Br0:28 I0:017 M75:8

a

I I

55

Cl Na64 Ca36

55

Cl Na64 Ca36

M M

98

100

Cl Na70 Ca19 Mg11 100

99

Br

0:447 0:017

0:008

I

M67

99 HBO0:034 M143 66 Cl23 10 2 Na Ca Mg

Cl100 Na76 Ca14 Mg8 100

Cl Na70 Ca20 Mg10 61

Cl HCO29 3 ðNaþKÞ92 Ca6 98

Cl ðNaþKÞ74 Ca19 Mg7

Br, I, and HBO2 were not measured if not reported.

low inflows to wells, usually in the range of 0.5–2 L/min, being of the Na–HCO3–Cl type with TDS contents distinctly exceeding 20 g/L. Group II in Table 2 represents selected examples of mixing between diagenetic and meteoric waters which takes place in springs and shallow wells. For Wysowa (No. 7), Szczawa (No. 8) and Szczawnica (No. 9), mixed waters can be approximated by one line with the most positive d18O values being nearly identical in all three sites whereas the most negative values of d18O and d2H represent the mean value of local meteoric waters. The mixing process is also seen in d18O–Cl (Fig. 4) and in d2H–Cl graphs, though different mixing lines are observed because the non-meteoric end members have very different Cl contents. Long term observations exhibit variable mixing proportions in the majority of springs and

wells (Les´niak, 1980: Zuber and Grabczak, 1987). For instance, extreme variations were observed in a shallow well in Szczawa (No. 8d) with d18O and d2H changing along the mixing line between +1‰ and 6.8‰, and 41‰ and 68‰, respectively. The chemistry of mixed waters is governed by that of the diagenetic component, though when the meteoric component dominates, they may change to the Na–Ca–HCO3–Cl type (e.g. Nos. 8d and 9c in Table 2). The third group in Table 2 represents two examples of the socalled zuber waters which are of the HCO3–Na and HCO3–Mg–Na types with TDS contents in the range of about 20–30 g/L, and outflow rates of 0.5–2 L/min, though the meteoric component dominates. Such water was found for the first time in 1914 in Krynica by Rudolf Zuber at a depth of several hundred meters; whereas

Fig. 3. Typical isotope compositions of highly mineralized waters in the western part of the Polish Carpathians, with the supposed evolution paths of marine water during diagenesis. Some characteristic samples are identified by numbers given in tables. The Upper Silesia Coal Basin (USCB) and site No. 10 are outside the study area.

Fig. 4. d18O–Cl relationships of diagenetic waters in the flysch formations in comparison with those of the USCB and Badenian sedimentation waters, with supposed evolution paths during ultrafiltration and diagenesis (symbols as in Fig. 3).

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A. Zuber, J. Chowaniec / Applied Geochemistry 24 (2009) 1889–1900

now it is exploited from four wells in that spa and is known also from two wells in Złockie. The origin of zuber waters was controversial even when the isotope analyses became available due to a high scatter of the data in the d18O–d2H diagrams (Dowgiałło, 1973). However, Zuber (1987), Dulin´ski (2001), and Oszczypko and Zuber (2002) showed that in Cl–d2H diagrams they scatter along the same mixing lines as other chloride CO2-rich waters. Therefore, their shifts from the d18O–d2H mixing line are related to the isotopic exchange of O between water and CO2. Such shifts can be significant because the exchange takes place over a long time between high amounts of CO2 migrating from greater depths through small amounts of water. The pressures of CO2 measured at well heads are within the range of 2.1–3.2 MPa. The Cl–d2H mixing line of the zuber waters when extrapolated to zero Cl content indicates the d2H value of modern water in the Krynica area. However, these waters occur at larger depths than glacial age waters, which suggests their interglacial age. As a result of such great ages of the meteoric component and large amounts of CO2, the zuber waters differ distinctly from other chloride CO2-rich waters in the region. All chloride CO2-rich waters contain specific components, like Br and I, characteristic of non-meteoric origin, and are rich in HBO2. The molar Na+/Cl ratio of the first two groups ranges between about 2 and 4, whereas for the zuber waters it is between 7 and 13.5. 5.3. Chloride waters in flysch formations The most positive d18O values of Cl waters (group I in Table 3) can be regarded as representative for diagenetic waters like the chloride CO2-rich waters discussed in the previous section. They are also characterized by elevated values of m(Na+/Cl) and B/Cl, being of the Na-Cl type. Water No. 19a, which has the highest Cl in the Sól area, is not available for isotope analysis. Therefore, its d18O value of 7‰ is assumed to fit with the Sól mixing line in Fig. 4, which defines in turn its d2H value of 12‰ in Fig. 3. An alternative interpretation relates to the position of the water in the middle of the diagenetic paths with d18O about 2.3‰ and d2H about 12‰, i.e., incomplete diagenesis at a temperature much lower than the typical final value of 170–200 °C, whereas the Sól line in Fig. 3 extrapolates to the final values. A close occurrence of waters which during the process of diagenesis were under distinctly different temperatures suggests that the alternative hypothesis is less probable. Examples of mixing between diagenetic Cl waters and local meteoric waters are given in the second group. The chemistry of that group is of course governed by the higher mineralization of the diagenetic component, but the presence of the meteoric component may lead to changes to the Na–Cl–HCO3 type. In the Carpathian flysch, diagenetic waters without admixtures of meteoric components seem to be practically free of SO2 4 (see Table 5), though similar waters in the California Coast Range (White et al., 1973) and in the south Bavaria Tertiary basin (Oszczypko and Zuber, 2002) contain distinct concentrations of that ion. Contrary to some other European and world regions, within the study area no water has been found so far which would correspond to the diagenetic paths postulated in Figs. 3 and 4. The only example given in Tables 3 and 5 (No. 10) is from the area situated about 70 km to the east of the study area. Judging from the position of that water in Fig. 4, 60% is of marine origin and 40% is diagenetic. Though the molar ratio of Na+ to Cl distinctly exceeds 0.87, the type of water is Cl–Na like that of sea water. 5.4. Brines and saline waters in the bedrocks of flysch The first group in Table 4 represents isotopically practically unaltered Miocene ocean water as shown by several authors

_ (Dowgiałło, 1973; Rózkowski and Przewłocki, 1974; Pluta and Zuber, 1995). However, as seen from Tables 4 and 5, the chemical composition of the Badenian marine sedimentation water significantly differs from ocean water mainly due to the reduction of sulphates, increased Ca2+ content by cation exchange with Mg2+, and release of such trace components like Br, I and B, which can most probably be related to the decay of organic matter. In most cases, the Badenian water is enriched in Cl in relation to ocean water, though the isotopic composition remains practically unchanged (Fig. 4). Such enrichment can be explained either by secondary dissolution of salts or by ultrafiltration resulting from the burial compaction as highly mineralized waters undergoing the latter process become enriched in chemical constituents without any significant change in isotopic composition (Fleischer et al., 1977). Ultrafiltration is more probable as the main process of chemical enrichment because in the case of the dissolution of NaCl, an increase in the Na+/Cl ratio would be expected, which is not observed, with the exception of No. 21 where m(Na+/Cl) is equal to 0.91. The second group is represented only by samples taken from two wells exploiting brine from Devonian carbonates. Their isotopic and chemical compositions fall within those of the most common and the deepest brines in the Carboniferous and Devonian formations of the Upper Silesia Coal Basin (USCB) (Pluta and Zuber, 1995), which are related to meteoric waters of a hot and dry climate in the Rotliegendes (Pałys, 1966). Sporadic but heavy rains leached weathered rocks, and meteoric waters infiltrated to large depths due to high differences in the topography of the basin. Strong enrichment in dissolved solids was initially supposed to result from evaporation prior to infiltration. However, as shown in Figs. 3 and 4, their isotopic composition is close to the world meteoric water line (WMWL) and independent of Cl content confirming the meteoric hypothesis, excluding evaporation as the enrichment process. Therefore, Pluta and Zuber (1995) suggested ultrafiltration as the main secondary process leading to high Cl contents in the USCB brines. These brines are of the Cl–Na–Ca type with elevated Mg2+ contents. Table 6 contains examples of waters for which isotopic analyses are unavailable, with the chemical data being in most cases incomplete. The first group represents waters in flysch formations which can be identified as those containing a diagenetic component as deduced from elevated Na+/Cl ratios. They are of the Na–Cl type when the diagenetic component dominates and of the Na–Cl– HCO3 type when the meteoric component dominates. The origin of other waters in the bedrocks of flysch cannot satisfactorily be identified without isotope data. However, by analogy to the waters identified by isotope data, waters of the Cl–Na type (Nos. 22, 22a and 26a) are presumably of marine origin, waters of the Cl-Na-Ca type with high Ca2+ contents (20f, 20 g, 20 h), and other water of the Cl–Na–Ca type (25a, 25b, 26b, and 27b) are particularly difficult to identify. The chemical composition of water in the Badenian formation below the flysch at a depth of about 1500 m (No. 27a) significantly differs from other shallower Badenian waters. Both the Na+/Cl ratio of 1.5 and the TDS content of about 11 g/L suggest that Badenian sediments at greater depths underwent similar diagenetic changes as flysch formations.

6. Examples of diagenetic waters in some other areas The ranges of isotope data of formation waters in three other European areas are shown schematically in Fig. 5, with the data of examples that are close to the diagenetic and/or marine members given in Table 7. All these waters are characterized by high Na+/Cl ratios, being mainly of the Na–Cl and Na–Cl–HCO3 types.

1897

A. Zuber, J. Chowaniec / Applied Geochemistry 24 (2009) 1889–1900

Isotope data on the formation waters in the Tertiary molassa basin of south Bavaria were described by Stichler (1997) who showed that they result from mixing between diagenetic and meteoric components representing cold and moderate Quaternary climates, and warm pre-Quaternary climates, as seen in Fig. 5 from the large scatter of the meteoric component along the World Meteoric Water Line (WMWL). Their diagenetic end component is represented by water in Bad Endorf (Table 7), which is also characterized by high Na+/Cl and B/Cl ratios as pointed out by Oszczypko and Zuber (2002).

Fig. 5. The isotopic ranges of waters which result from mixing between diagenetic and meteoric waters in molassa of south Bavaria (Stichler, 1997), and between diagenetic waters containing some remnants of marine water and meteoric waters in the Vienna Basin and Bochemian Massif (Buzek and Michalicˇek, 1997), and in the Central Carpathian Synclinorium (CCS), south-eastern Poland (Porowski, 2006). Details of samples are given in Table 7, diagenetic paths as in Fig. 3.

Formation waters in the Vienna Basin and Bohemian Massif (Buzek and Michalicˇek, 1997) seem to result from mixing between diagenetic, marine and meteoric waters. The isotope and chemical data of two samples from the Neogene of the Vienna Basin (Nos. 2 and 50 in Table 7) either represent diagenetic water or are close to the diagenetic end member. Sample No. 29 taken from Paleogene formations of the fore-deep of the Bohemian Massif is very similar to No. 2 in the Vienna Basin, whereas samples Nos. 28 and 34 represent mixtures of marine and diagenetic waters (Fig. 5). The salinity of these waters was regarded by Buzek and Michalicˇek (1997) as a result of ‘‘subaerial evaporation of diluted sea water” whereas their isotopic and chemical compositions are inconsistent with such a hypothesis. Waters related to oil-fields in the Central Carpathian Synclinorium (CCS), SE Poland, were described by Porowski (2006), with the ranges of d18O and d2H values being shown in Fig. 5. Two samples (Nos. 80 and 81 in Table 7) of the total 81 samples described in the original work seem to represent mixtures of marine and diagenetic water, similar to No. 10 within the present work. Five other samples are close to the diagenetic end member. All the remaining waters also have high Na+/Cl ratios indicating the contribution of a diagenetic component, though they are diluted in a secondary process by meteoric waters of different climates. The dominant presence of diagenetic waters in the flysch Carpathians can also be deduced from the earlier results of Borysławski et al. (1980) who considered archival data on 308 waters from the whole area of the Polish Carpathians flysch from depths exceeding 100 m, and obtained the following mean chemical composition expressed by the Kurlov formula: 84

Br0:005 I0:012 M19:3

1 Cl HCO14 3 SO4

Na93 Ca5 Mg2

which represents waters of the Na–Cl type, with the molar ratio of Na+/Cl above 1.

Table 7 Examples of ‘‘pure” diagenetic waters and mixtures of diagenetic and marine waters, without a distinct contribution of meteoric components, in comparison with the sea water (SW). No.a

d18O (‰)

d2H (‰)

Cl g/L

m(Na+/Cl)

0

19.6

0.86

SW 0 Molassa of South Bavariab Bad Endorf 5.2

19

Paleogen of Vienna Basinc 2 50

B/Cl (‰) 0.23

Cl/Br

Chemical type

287

Cl–Na

8.73

1.29

11

699

Na–Cl

25.9 n.d.

11.7 5.23

0.98 0.91

3.8 19.6

154 308

Na–Cl–HCO3 Na–Cl–HCO3

Paleogen in the fore-deep of Bohemian Massif c 28 2.4 29 4.5

14.6 25.8

11.5 11.5

1.06 1.07

3.9 4.8

164 103

Na–Cl–HCO3 Na–Cl–HCO3

Flysch of Central Carpathian Synclinoriumd 29 4.3 50 5.2 56 4.9 58 4.6 65 4.2 80 2.3 81 2.9

20.1 21.2 25.0 21.0 21.4 15.1 14.5

13.5 10.3 6.16 9.36 12.4 25.0 5.56

1.20 1.15 1.34 1.20 1.20 1.11 1.24

2.8 6.5 100 5.1 1.7 0.9 2.7

343 155 58 152 42 172 88

Na–Cl Na–Cl–HCO3 Na–Cl Na–Cl Na–Cl Na–Cl Na–Cl

North Slopee 78-AK-54

6.6

34.4

10.6

1.08

14.9

196

Na–Cl

California Coast Rangesf Wilbur Spring Ink Spring

5.4 5.6

22.2 24.1

1.34 n.r.

32 n.r.

606 n.r.

Na–Cl–HCO3 n.r.

a b c d e f

4.6 5.2

Nos. as in original works. Stichler (1997) and Oszczypko and Zuber (2002). Buzek and Michalicˇek (1997). Porowski (2006). Kharaka and Carothers (1986). White et al. (1973).

9.7 0.75

1898

A. Zuber, J. Chowaniec / Applied Geochemistry 24 (2009) 1889–1900

Fig. 6. Molar ratio of Na+ to Cl, weight ratio of B to Cl, and temperature in geopressured zones of coastal oil and gas fields in Louisiana and Texas (original data after Kharaka and Carothers, 1986).

Chloride CO2-rich waters are also common in the Slovakian Carpathians near the boundary with Poland (see Fig. 1), e.g. in Bardejov and Cigelka, with Na+/Cl molar ratios exceeding 3.5, whereas brine with that ratio equal to about 0.94 is known in Oravska Polhorá (Franko et al., 1975). Mixing between diagenetic and paleometeoric waters explains the isotope data of formation waters observed in the North Slope, Canada (Kharaka and Carothers, 1986), which are characterized by Na+/Cl molar ratios above 1, and high B/Cl weight ratios, as seen for their diagenetic end member shown in Table 7. Kharaka and Carothers (1986) also presented isotope and chemical data of formation waters from geopressured zones in the northern Gulf of Mexico. Their isotope data scatter along the diagenetic are paths shown in Fig. 3 whereas the values of m(Na+/Cl), B/Cl and temperatures are shown in Fig. 6. Unfortunately, for the 24 isotope samples only eight chemical analyses were presented, without identification to individual samples. In spite of that drawback, the isotope, chemical and temperature data of these waters indicate that diagenetic processes are actually in progress, and that the decrease in Cl content, which is supposedly caused by the contribution of diagenetic water, is accompanied by increased values of m(Na+/Cl), B/Cl and temperature. As mentioned, non-meteoric waters of the Wilbur, Ink and Geyser Springs in the California Coast Range were regarded by White et al. (1973) as a result of early metamorphism though perhaps they are related to late diagenesis. They are of the Na–Cl–HCO3 type, characterized by high Na+/Cl and B/Cl ratios as shown in Table 7 for the two chosen examples. Possible occurrences of diagenetic waters can perhaps be found in some other areas though their identification is not always straightforward, especially if the isotopic composition of the end member differs from the typical values (e.g. Clayton et al., 1966; Hitchon and Friedman, 1969), because the isotopic composition of dehydrated water depends on the isotopic composition of clay minerals, which is related to their original environment (e.g. Taylor, 1974). There are also basins without measurable signatures of diagenetic waters (e.g., Kharaka and Carothers, 1986; Fontes and Matray, 1993a,b). 7. Discussion The initial isotopic and chemical composition of flysch sedimentation water remains unknown, but there is no reason to suspect that it differed significantly from the typical marine sedimentation water similar to that still preserved in some parts of the Badenian formations under the Carpathian overthrust and in the Carpathian Foredeep. Thus, it can be assumed that the isoto-

pic composition of the flysch sedimentation water was close to that of the Badenian sedimentation water, with the salinity most probably increased in a similar way due to ultrafiltration as shown in Fig. 4. That hypothesis agrees with the opinions of Berry (1969) and Graf (1982) who regard ultrafiltration as one of the main processes leading to high salinities of deep waters. The isotopic composition of the sedimentation water was progressively changing from the initial values close to SMOW to the final values in the range of ca. 7–8‰ for d18O and ca. 25‰ for d2H as modelled by Suchecki and Land (1983) and described by a number of other authors (e.g., Taylor, 1974, 1977, 1987; Kharaka and Carothers, 1986; Longstaffe, 1987). In that process, the isotopic composition of pore water becomes completely changed by released bound water and buffered by isotopic exchange with remaining bound water. The illitization of smectites in smectite–illite packets during the diagenesis of clay minerals is supposed to incorporate K from dissolved K-feldspars into illites in reactions accompanied by the release of Na, Ca, Mg, Fe, and some other minor components, which take part in the production of other diagenetic minerals like chlorite, albite and quartz (Hower et al., 1976; Boles and Franks, 1979; S´rodon´, 1999). However, the chemical data on waters, which were involved in diagenetic processes and are still preserved in diagenetic rocks, indicate that enrichment in Na+ in relation to the initial sedimentation water mainly occurs at the cost of Ca2+, Mg2+ and K+. The final chemical composition is also governed by other processes, mainly by cation exchange, ultrafiltration, enhanced dissolution of minerals in the abundant presence of CO2 and mixing with meteoric waters. The influence of cation exchange in which Ca2+ from water exchanges with Na+ and Mg2+ from clay minerals is well seen for common CO2-rich waters (Table 2). That influence on chloride CO2-rich waters with meteoric components is also seen for examples given in Table 3, particularly for Nos. 1d and 3c, where old meteoric components dominate. A rough estimate of the final bound and pore water reservoirs can be performed on the basis of data presented by Bruce (1984) and S´rodon´ et al. (1992, 2006). According to these authors, the bound water content at the initial stages of diagenesis is ca. 6– 9 wt.%, i.e. up to 20 vol.%, which already significantly exceeds the free water content, if the porosity of clay sediments is reduced to ca. 10% after the early stages of compaction. The data of Gucwa and Pelczar (1992) indicate that flysch shales in the Polish Carpathians have bound water content reduced to ca. 2–3 wt.%, i.e. 6– 9 vol.%, whereas their porosity is reduced to less than 1%, which means that the bound water content decreased by 10 vol.% or more, i.e. no less than about 100 L of bound water was released from 1 m3 of rock during the main diagenesis process in addition to the initial pore water squeezed out as the result of compaction during the burial. If that estimation is correct, the final pore water reservoir (61%) is small in comparison with the remaining bound water reservoir (6–9 vol.%), which explains the buffering effect described in the literature (e.g., Longstaffe, 1987). Flysch shales in the Polish Carpathians show characteristic features of past diagenetic processes having generally low smectite percentage (%S) in illite–smectite minerals. Within all units of the Magura Nappe, these percentages in relation to the age of rocks are as follows (in%S): 10–20 for Late Cretaceous-Palaeocene, 16–20 for Palaeocene–Eocene, 24–34 for Eocene, 24–50 for Late Eocene– Oligocene, 55 for Oligocene, and 85 for Miocene (S´wierczewska, 2005). These data suggest that younger formations are still potentially susceptible to illitization. However, according to S´wierczewska (2005), the smectite percentage is independent of the present depth within the Magura Nappe, which suggests that illitization took place during the burial of flysch sediments, before their emplacement in the current position, which started about 30 Ma and ended about 20 Ma ago. On the other hand, according

A. Zuber, J. Chowaniec / Applied Geochemistry 24 (2009) 1889–1900

to S´rodon´ (2007), in the eastern part of the Polish Carpathians, the degree of illitization is related to the depths of sediments, which suggests that the final stages of the illitization took place at the present position of the overthrust units. Judging from these data, there is no renewal of diagenetic waters within the sediments of the Magura Nappe, whereas other flysch units of the Polish Carpathians require further study in that respect. The temperatures of diagenesis within the Magura Nappe were mainly in the range of 75–165 °C (S´wierczewska, 2005), thus the pore waters of the flysch should have isotopic compositions ranging from that characteristic for the sedimentation water to that characteristic for the final diagenetic water, i.e. along the whole diagenetic paths shown in Fig. 3. Surprisingly, the diagenetic waters found so far within the Magura Nappe have isotopic compositions close to the final diagenetic temperatures. Perhaps, the amounts of water released at lower temperatures were too low to be still preserved in significant quantities. The diagenetic waters are usually overpressured, which is generally regarded as the result of the past compaction and diagenesis (e.g. Bruce, 1984). However, according to S´rodon´ and McCarty (2008), the density of free water is close to that of bound water, thus, the release of water during illitization should not cause any significant increase of pressure. In addition, as explained above, there is no further diagenesis within the Magura Nappe. Therefore, the only possible explanations for the observed overpressures can be related to remaining orogenic movements, and/or to the hydrodynamic pressures which result from high differences in the topography. However, springs Nos. 12 and 13 with diagenetic components exist at sites where the flysch thickness is less than 1.5 km and there are no great differences in the topography.

8. Conclusions Chloride waters of flysch formations in the Polish Carpathians are shown to be of diagenetic origin as deduced from the geology of mother formations, and isotopic and chemical data. The following three main stages of the processes leading to their final Cl content and isotopic composition can be suggested: (1) initial burial compaction of marine sediments; (2) further burial compaction and diagenesis, the latter being initiated when critical temperatures are reached; and (3) final compaction and diagenesis where the isotopic composition is buffered by the dehydration process. The first stage leads to enrichment in salinity due to ultrafiltration without significant changes in the isotopic composition of water. During the second stage, the salinity may either increase or decrease, depending on the relationships between the ultrafiltration process and the amounts of released water, whereas the isotopic composition progressively changes from values close to SMOW to those similar to typical diagenetic waters in other regions of the world. In the third stage, the isotopic composition does not change any more whereas the salinity may further decrease due to the continued release of bound water. That conceptual model of the evolution of pore water during the diagenesis of clay minerals corresponds to the three-stage concept of the water escape process occurring in the burial diagenesis of clay minerals, which was proposed by Burst (1969) and also discussed by Bruce (1984). In all three stages, the evolution paths of both the residual water and the ultrafiltrate are similar, the residual always being more enriched in chemical constituents than the ultrafiltrate. An infinite number of quantitative scenarios of the diagenesis processes can be expected considering possible large differences in the values of such initial parameters like chemical composition of sedimentation water, porosity, mineralogy and structure of sediments as well as temperature and pressure history of burial.

1899

Diagenetic waters are usually characterized by elevated Na+/Cl and B/Cl ratios which are helpful in their identification whereas the Cl/Br ratio is not to any degree indicative as it can be deduced from the data given in Table 7. Within the study area, ‘‘pure” diagenetic waters have been preserved in some tectonic and sedimentation traps; being either drained naturally via activate faults or available for withdrawal, if stored in sandstone interbeds. Their occurrences are quite common but available resources are rather low. Near the ground surface, they mix with local meteoric waters becoming diluted, and if CO2 also migrates from great depths, they form chloride CO2-rich waters. Abundant fluxes of CO2 in the area without near-surface occurrences of diagenetic waters form common CO2-rich waters of HCO3–Ca types or other types with elevated Mg2+ and/or Na+ contents in the case of older waters, i.e. if their ages can be related to the pre-bomb era or even to the preHolocene recharge. Isotope data for diagenetic waters within the study area are so far available only for several near-surface occurrences and two deep wells. On the d18O–d2H graphs, they fall on mixing lines between the typical end members of diagenetic water and the mean composition of modern groundwater. However, if more data were available from deep wells, the picture would probably differ, becoming most probably similar to those observed in the eastern part of the Polish Carpathians and several other European regions. In the areas of near-surface occurrence of diagenetic waters, which are characterized by very low flow rates, the meteoric waters cannot penetrate to large depths. As a consequence, perspectives for discovering abundant resources of highly mineralized waters are excluded for such areas. Common CO2-rich waters occur in some fault areas where deep-seated CO2 migrates to the surface without a contribution from the diagenetic water. Brines preserved in some parts of the Badenian sediments are of marine origin with an isotopic composition close to SMOW values, and chemical composition significantly changed by reduction of sulphates and enrichment resulting from ultrafiltration. However, in some areas at depth of about 1.5 km, the primary Badenian brine is also chemically changed and diluted by dehydration water of diagenetic origin. Other brines in the bedrocks of flysch are probably of paleometeoric origin. Acknowledgements Drs. I. Józefko, B. Porwisz and M. Dulin´ski are thanked for permission to use their data, Prof. J. S´rodon´ is thanked for valuable discussions related to the smectite illitization in the Polish Carpathians. Constructive review comments of Prof. T. Pacˇes and Prof. S. Witczak were helpful in the correction of the early version of the manuscript. References Berry, F.A.F., 1969. Relative factors influencing membrane filtration effects in geologic environments. Chem. Geol. 4, 295–301. Boles, J.R., Franks, S.G., 1979. Clay diagenesis in Wilcox Sandstones of south-west Texas: implications of smectite diagenesis on sandstone cementation. J. Sed. Petrol. 49, 55–70. Borysławski, A., Oszczypko, N., Tomas´, A., 1980. Chemical composition of Carpathian saline waters – a statistical analysis. Biul. Inst. Geol. 323, 57–87. Bruce, C.H., 1984. Smectite dehydration – its relation to structural development and Hydrocarbon accumulation in Northern Gulf of Mexico Basin. Am. Assoc. Petrol. Geol. Bull. 68, 673–683. Burst, J.F., 1969. Diagenesis of Gulf Coast clayey sediments and its possible relation to petroleum migration. AAPG Bull. 53, 73–93. Buzek, F., Michalicˇek, M., 1997. Origin of formation waters of S-E parts of the Bohemian Massif and the Vienna basin. Appl. Geochem. 12, 333–343. Chowaniec, J., 2009. Hydrogeology study of the western part of the Polish Carpathians. Biul. PIG 434, Warsaw. _ Chowaniec, J., Cie˛zkowski, W., Dulin´ski, M., Józefo, I., Porwisz, B., Zuber, A., 2009. Chemical facies of CO2-rich waters in flysch Carpathians versus water age. Biul. PIG 436. Warsaw (in Polish).

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