Isotopic Composition of Thermal Waters in Chukotkageotherm.ginras.ru/Pdf/_Pol et al 2008 244_LMReng.pdfISSN 0024-4902, Lithology and Mineral Resources, 2008, Vol. 43, No. 5, pp. 429–453

ISSN 0024-4902, Lithology and Mineral Resources, 2008, Vol. 43, No. 5, pp. 429–453. © Pleiades Publishing, Inc., 2008.Original Russian Text © B.G. Polyak, E.O. Dubinina, V. Yu. Lavrushin, A.L. Cheshko, 2008, published in Litologiya i Poleznye Iskopaemye, 2008, No. 5, pp. 480–504.

429

Hot springs are known in the eastern Chukotka Pen-insula since the terminal 18th century, although theirscientific studies commenced only in the mid-1930s.Information on these springs gained during geologicalmapping and thematic works is summarized with dif-ferent details in (Shvetsov, 1957; Kalabin, 1959;Ivanov, 1960; Zavgorodnii, 1962; Zelenkevich, 1963;Gol’dtman, 1967;

Katalog…

, 1969;

Gidrogeologiya…

,1972). Fragmentary data on the most known springs arecontained in (

Chukotka…

, 1995;

Prirodnye…

, 2003).Lists of hydrothermal springs and their overviews arepresented by Kryukov in (

Ekosistemy…

, 1981) andStepina in (Vladimirtseva et al., 2001).

Most springs are located at low altitudes in thevicinity of the seashore. At the same time, thermomin-eral springs located 40–50 km away from the sea dis-charge usually at altitudes below +100 m. In terms ofthe anion composition of waters, most springs are chlo-ride or, less commonly, chloride–hydrocarbonate; interms of the cation composition, sodium–calcic.

The distribution patterns and salt compositions ofthermal waters in Chukotka provided grounds forassuming their genetic relation to seawater. Someresearchers believed that seawater feeds immediatelyhydrothermal springs being infiltrated into coastal rockcomplexes (Shvetsov, 1937; Stremyakov, 1967; andothers). Ivanov (1960) believed that the high salt con-tent in thermal waters could be explained by neither thepenetration of recent seawaters to interior areas of thecontinent nor the influence of their ancient buried orepigenetically transformed counterparts. Instead, he

presumed that “…thermal waters formed on account ofinterstitial solutions of sea basins and they are signifi-cantly younger in geological sense as compared withhost formations” (Ivanov, 1961, p. 233).

At the same time, nature of water (H

2

O) proper inthermomineral fluids cannot be interpreted adequatelywithout the knowledge of its isotopic composition,which has never been studied. To fill this gap, we sam-pled in 2002 and 2004 waters from several thermomin-eral springs of eastern Chukotka.

1

Data on the isotopiccomposition of hydrogen and oxygen in some watersamples were published elsewhere (Cheshko et al.,2004). In the present work, these results are supple-mented with information on samples collected later andon samples from other springs examined in 2004 and2005 by geologists from the

Georegion

Federal StateUnitary Enterprise (Anadyr), who kindly donated themfor the analysis. In total, 80 samples of thermomineraland surface waters were studied for 23 groups of ther-mal springs. Figure 1 demonstrates their locations.Tables 1 and 2 present the results of analytical studies.

As applied to Arctic conditions, it is necessary tospecify the notion “thermal spring.” In balneology,warm or hot therapeutic waters that cause correspond-ing physiological feelings are usually called as thermal.In the mining industry, waters with discharge tempera-tures sufficient for using them for certain purposes

1

E.A. Vakin from the Institute of Volcanology and Seismology(Far East Division, Russian Academy of Sciences), who died onSeptember 13, 2003, took part in field works of 2002 and analysisof materials obtained.

Isotopic Composition of Thermal Waters in Chukotka

B. G. Polyak

a

, E. O. Dubinina

b

, V. Yu. Lavrushin

a

, and A. L. Cheshko

a

a

Geological Institute (GIN), Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017 Russiae-mail: [email protected]

b

Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry (IGEM), Russian Academy of Sciences, Staromonetnyi per. 35, Moscow, 119017 Russia

Received December 24, 2007

Abstract

—Twenty three groups of thermomineral springs in eastern Chukotka with the discharge temperatureof 2 to 97

°

C and mineralization of 1.47 to 37.14 g/l are studied and compared with surface freshwater from theirlocalities. The

δ

D

and

δ

18

O

values in surface waters vary from –121.4 to –89.5

‰

and from –16.4 to –11.1

‰

,respectively, while respective values in thermomineral waters range from –134.2 to –92.5

‰

and from –17.6 to–10.5

‰

. The

δ

D

value in surface waters decreases from the east to west, i.e., toward interior areas of the pen-insula. Hydrothermal springs most depleted in deuterium (

δ

D

< –120

‰

) are localized in the geodynamicallyactive Kolyuchinskaya–Mechigmen Depression. According to the proposed formation model of Chukotka ther-momineral waters, their observed chemical and isotopic characteristics could result from the mixing (in differ-ent proportions) of surface waters with the deep-sourced isotopically light mineralized component (

δ

D

≈−

138‰,

δ

18

O

≈

–19

‰, M = 9.5–14.7 g/l). The latter originates most likely from subpermafrost waters subjectedto slight cryogenic metamorphism.

DOI:

10.1134/S0024490208050027

430

LITHOLOGY AND MINERAL RESOURCES

Vol. 43

No. 5

2008

POLYAK et al.

Fig. 1.

Thermomineral springs of the eastern Chukotka Peninsula with measured isotopic composition of H

2

O. (1) Groups ofsprings; (2) occurrences of Late Cenozoic basaltic volcanism, after (Akinin and Apt, 1994; Kryukov, 1980; Nedomolkin, 1978;Romanova and Zhukova, 1970a, b). Numerals designate springs (their other names mentioned in publications are given in paren-theses): (1) Chaplino, (2) Senyavin, (3) Arakamchechen, (4) Kivak, (5) Kukun (Lorino), (6) Mechigmen (Gil’mimlinei,Khel’khmymleveem), (7) Babushkiny Ochki (Bezymyannye), (8) Tumannye, (9) Dezhnev, (10) Neshkan, (11) Teyukei(Tag’ekveem), (12) Kub (Pravo-Tynynvaam), (13) Vytkhytyaveem, (14) Oranzhevye, (15) Olen’i (Ynpynenveem), (16) Arenysh-kynvaam, (17) Nel’pygenveem (Ngel’veem), (18) Verkhne-Nunyamoveem, (19) Sineveem, (20) Getlyangen, (21) Stupenchatye,(22) Ioni mineral; (23) Pechingtanvaam.

(electric energy production, heat supply, and others) areconsidered as thermal and sometimes called as heatwaters. In the physical (geophysical) sense, waters withtemperatures exceeding their average climatic value inthe particular area, i.e., all the groundwaters occurringbelow the layer of annual heat cycle are classed withthermal waters. K. Keilgak, a German hydrogeologist,was first to formulate clearly such a concept in 1912–1917. He emphasized that the notion of warm spring orwarm groundwater that corresponds to spring or water,the temperature of which exceeds its average annualvalue in the particular area, is not permanent and abso-lute. It is variable to such a degree that waters with tem-peratures of at least 1

°

C in polar regions with the aver-age annual temperature of 0

°

C should be designated as“warm” or “thermal” (Keilgak, 1935). The surface dis-

charge of thermal springs is accompanied by advectivetransport of heat from the Earth’s interior, which addsits conductive heat losses. Chukotka is a typical Arcticregion with negative average annual surface tempera-tures (Fig. 2) and universal development of the cry-olithozone, i.e., permafrost. Therefore, all springs inthis region with their year-round discharge should beconsidered as thermal. The temperature of examinedthermal waters at the surface ranges from

~2°ë

in theNel’pygenveem (Ngel’veem, after Kievskii et al., 2006)springs to 97

°

C in one of the thermal jets in the Mechig-men springs. In winter, thermal springs form chrysto-crenes at different distances from their discharge areas.Such chrystocrenes are widespread in river valleys ofSubarctic regions, where they are usually attributed todischarges of underflows.

Erguveem

MMMeeeccchhhiiigggmmmeeennn EEEssstttuuuaaarrryyy

Tkachen Bay

Ne

skynpil’gyn Lagoon

BBBeee

rrriii

nnnggg

SSSttt

rrraaa

iiittt

·

682

3

20

1

Chaplino

Yttygran Is.

Arakamchechen Is.

Getlyangin Lagoon

Mechigmen

Bay

5

Lavrentiya Bay

23

8 6

16

7 1721

22 15

2

4

19

1158 Mt. Iskhodnaya

Prov

iden

iya

Bay

KivakC. Chukotskii

·

638

18

Ioni

veem

R.

Lavrentiya

Nunyamo

C. Achchen

Emmelen R.

Ruddera

Irgynkol

·

622

176° 175° 174° 173° 172° 171° 170° 169°64°

65°

66°

67°

Chegitun

Uelen

9

C. Dezhnev

Chegitu

n R.

Uta

veem

R.

C. NettenEnurmino

652

·

Mt. Mama

12

1110

·

1043

Belyaka Bar

Kolyuchinskaya

Estuary

Eturervee

m R.

14

13

Kus’

yuve

em R

.

Neshkan

12

Nunyamoveem R.

Igel

’khv

eem

R.

Kuetkuiym

Bay

Provideniya

çÛÌÎË„‡Ì

·

949

Lorino


Vol. 43

No. 5

2008

ISOTOPIC COMPOSITION OF THERMAL WATERS IN CHUKOTKA 431

Tab

le 1

.

Hyd

roge

n an

d ox

ygen

isot

ope

com

posi

tions

in w

ater

s of

the

east

ern

Chu

kotk

a Pe

nins

ula

Num

ber

in F

ig. 1

Sam

ple

Spri

ngs,

wat

er o

ccur

renc

es(

∆δ

D =

δ

D

ther

m

–

δ

D

surf

)

δ

18

O, ‰

δ

D, ‰

T

,

°

CD

ry r

esi-

due,

g/l

Kur

lov’

s fo

rmul

a

1

12

56

78

910

0U

relik

i Set

tlem

ent (

64

°

26

′

N, 1

73

°

09

′

W)

0a1/

02D

esce

ndin

g sp

ring

–13.

3–9

9.6

20.

034

0b2/

02C

reek

–13.

6–9

7.1

70.

020

1C

hapl

ino

(64

°

25

′

N, 1

72

°

30 W

)

∆δ

D =

–10

1.3

– (–

99.2

) =

–2.

1‰1a

21/0

2Se

lf-d

isch

argi

ng b

oreh

ole

–13.

6–1

01.3

8819

.280

Cl9

8/N

a62C

a37

1b22

/02

Eas

tern

gro

up, s

prin

g ne

ar th

e ba

sin

–13.

2–1

01.7

6818

.950

Cl9

8/N

a60C

a39

1c23

/02

Wes

tern

gro

up, s

prin

g–1

3.4

–100

.568

17.9

60C

l98/

Na5

9Ca4

01d

24/0

2Fa

r gr

oup,

spr

ing

in th

e di

g–1

3.1

–100

.679

18.9

80C

l98/

Na6

0Ca3

91e

2r-1

/02

Ul’

khum

Riv

er 7

00 m

dow

nstr

eam

of

the

swim

min

g po

ol–1

3.3

–99.

114

1.50

01f

2r/0

2U

l’kh

um R

iver

4 k

m u

pstr

eam

of

the

swim

min

g po

ol–1

3.8

–99.

28

0.02

61g

2r-2

/02

Cre

ek a

t the

Mt.

Uty

ug p

iedm

ont

–11.

1–8

9.5

2Se

nyav

in (

64

°

44

′

N, 1

72

°

51

′

W)

∆δ

D =

–13

0.8

– (–

106.

0) =

–24

.8‰

2a30

/02

Upp

er g

ryph

on (

no. 1

)–1

7.4

–130

.878

1.47

0C

l90S

O

4

6/N

a77C

a21

2b31

/02

Low

er g

ryph

on (

no. 2

)–1

7.2

–130

.579

1.50

0C

l92S

O

4

6/N

a77C

a21

2c30

-2r/

02K

lyuc

heva

ya R

iver

dow

nstr

eam

of

spri

ngs

–14.

3–1

06.9

0.14

02d

30-1

r/02

Kly

uche

vaya

Riv

er u

pstr

eam

of

spri

ngs

–14.

1–1

06.0

140.

050

3A

raka

mch

eche

n (6

4

°

45

′

N, 1

72

°

18

′

W)

∆δ

D =

–10

5.2

– (–

107.

1) =

1.9

‰3a

34/0

2L

ower

gry

phon

–13.

9–1

05.2

371.

470

Cl9

0SO

4

8/N

a82C

a17

3b32

r/02

Pyl’

mym

lak

Riv

er u

pstr

eam

of

spri

ngs

–14.

1–1

07.1

150.

070

3c33

m/0

2Se

awat

er in

the

Lak

e A

raka

mch

eche

n ar

ea–1

.3–1

0.0

4K

ivak

(64

°

21

′

N, 1

72

°

56

′

W)

∆δ

D =

–96

.1 –

(–9

2.8)

= –

3.3‰

4a40

/02

Dis

char

ge n

ear

the

indo

or s

wim

min

g po

ol–1

2.8

–96.

143

4.78

0C

l98/

Na5

1Ca4

84b

42r/

02C

reek

flo

win

g in

to th

e K

ivak

Lag

oon

–12.

1–9

2.8

4c41

m/0

2K

ivak

Lag

oon,

sea

wat

er–3

.4–2

6.8

5K

ukun

(65

°

35

′

N, 1

71

°

29

′

W)

∆δ

D =

–11

0.5

– (–

111.

5) =

1‰

5a50

/02

Spri

ng 1

(cu

be)

–14.

1–1

10.5

605.

230

Cl9

6/N

a76C

a21

5b1/

04Sp

ring

1 (

cube

)–1

4.8

–109

.556

4.60

05c

51/0

2Sp

ring

2 (

disc

harg

e in

the

swim

min

g po

ol)

–14.

6–1

09.3

524.

030

Cl9

6/N

a76C

a21

5d1a

/04

Bor

ehol

e–1

4.2

–109

.358

4.72

0C

l96/

Na7

1Ca2

75e

52r/

02K

ukun

Riv

er, d

owns

trea

m o

f sp

ring

s–1

3.6

–107

.35f

1r/0

4K

ukun

Riv

er, u

pstr

eam

of

spri

ngs

–14.

8–1

11.5

0.00

76

Mec

higm

en (

65

°

48

′

N, 1

73

°

24

′

W)

∆δ

D =

–13

0.6

– (–

111.

9) =

–18

.7‰

6a60

/02

Gry

phon

1 o

n th

e ri

ght w

all o

f th

e va

lley

–16.

0–1

30.6

903.

930

Cl9

2HC

O

3

5/N

a88C

a86b

62/0

2G

ryph

on 2

in th

e ce

ntra

l par

t of

the

fiel

d–1

4.8

–126

.964

4.08

0C

l92H

CO

3

6/N

a87C

a86c

64r/

02K

hel’

khm

ymle

veem

Riv

er, u

pstr

eam

of

spri

ngs

–14.

2–1

11.9

60.

170

432


Vol. 43

No. 5 2008

POLYAK et al.

Tab

le 1

. (C

ontd

.)

12

56

78

910

7B

abus

hkin

y O

chki

(66

°00′

N, 1

73°3

6′ W

) ∆δ

D =

–13

4.2

– (–

109.

9) =

–24

.3‰

7a70

/02

Nor

ther

n gr

ypho

n–1

7.5

–134

.220

9.26

0C

l74H

CO

321/

Na5

5Ca3

3Mg1

07b

2/04

Nor

ther

n gr

ypho

n–1

7.1

–132

.221

9.58

0C

l80H

CO

320/

Na5

6Ca3

2Mg9

7c71

/02

Sout

hern

gry

phon

–17.

1–1

31.9

149.

150

Cl7

5HC

O32

0SO

45/N

a58C

a33M

g67d

2a/0

4So

uthe

rn g

ryph

on–1

6.6

–130

.918

7e72

/02

Spri

ng n

ear

the

pied

mon

t of

the

trav

ertin

e co

ne–1

7.6

–133

.714

9.28

0C

l74H

CO

320S

O45

/Na5

7Ca3

2Mg8

7f73

r/02

Riv

er in

the

spri

ngs

area

–14.

3–1

09.9

7g74

o/02

Lak

e Io

ni–1

4.8

–112

.57h

12r/

04L

ake

Ioni

–15.

0–1

15.2

7i13

r/04

Wel

l at t

he L

ake

Ioni

coa

st–1

5.8

–119

.07

8T

uman

nye

(65°

49′ N

, 173

°27′

W)

8a80

/02

Gro

up 1

, spr

ing

–16.

2–1

31.7

598b

81/0

2G

roup

2, s

prin

g–1

6.9

–131

.655

3.40

0C

l91H

CO

36/N

a86C

a11

9D

ezhn

ev (

66°0

6′ N

, 169

°49′

W)

∆δD

= –

96.9

– (

–98.

2) =

1.3

‰9a

90/0

2B

oreh

ole

Ver

khny

aya

–13.

2–9

6.9

6919

.600

Cl9

9/N

a72C

a26

9b91

/02

Bor

ehol

e T

sent

ral’

naya

(ne

ar th

e sw

imm

ing

pool

)–1

2.6

–95.

960

19.7

60C

l99/

Na7

1Ca2

79c

92/0

2B

oreh

ole

Niz

hnya

ya (

near

the

dig)

–13.

4–9

7.2

5319

.290

Cl9

9/N

a72C

a26

9d93

r/02

Gor

yach

ii C

reek

, 700

m d

owns

trea

m o

f sp

ring

s–1

2.9

–96.

60.

520

9e94

r/02

Gor

yach

ii C

reek

, 300

m u

pstr

eam

of

Bor

ehol

e V

erkh

nyay

a–1

3.7

–98.

210

Nes

hkan

(66

°43′

N, 1

73°1

8′ W

) ∆δ

D =

–12

0.1

– (–

108.

5) =

–11

.6‰

10a

3/04

Upp

er g

roup

, spr

ing

–14.

5–1

20.1

5237

.140

Cl0

0/N

a69C

a28

10b

3r/0

4A

anry

lyne

kvee

m R

iver

, low

er r

each

es–1

3.9

–108

.513

.440

11T

eyuk

ei (

66°4

2′ N

, 173

°10′

W)

∆δD

= –

113.

4 –

(–10

9.0)

= –

4.4‰

11a

4/04

Min

eral

wat

er s

prin

g–1

4.6

–113

.46

17.6

40C

l100

/Na6

7Ca3

111

b4r

/04

Lef

t tri

buta

ry o

f th

e T

eyuk

eive

em R

iver

–14.

3–1

09.0

120.

120

12K

ub (

66°3

1′ N

, 173

°14′

W)

∆δD

= –

119.

3 –

(–10

8.1)

= –

11.2

‰12

a6/

04Sp

ring

–15.

5–1

19.3

74.

480

Cl8

8HC

O31

1/N

a80C

a16M

g412

b6r

/04

Kub

Cre

ek, 2

00 m

ups

trea

m o

f sp

ring

s–1

4.7

–108

.114

0.06

512

c5r

/04

Prav

aya

Tyn

ynva

am R

iver

–14.

6–1

09.0

13V

ytkh

ytya

veem

(66

°19′

N, 1

74°3

7′ W

) ∆δ

D =

–12

4.0

– (–

119.

7) =

–4.

3‰13

a7/

04Sp

ring

–16.

9–1

24.0

653.

450

Cl9

0HC

O31

0/N

a74C

a26

13b

7r/0

4V

ytkh

ytya

veem

Riv

er, u

pstr

eam

of

spri

ngs

–16.

4–1

19.7

170.

034

14O

ranz

hevy

e (6

6°12

′ N, 1

74°3

4′ W

) ∆δ

D =

–11

8.6

– (–

119.

3) =

0.7

‰14

a8/

04Sp

ring

–14.

7–1

18.6

1436

.230

Cl9

9/N

a52C

a46

14b

8r/0

4K

al’k

heur

erve

em R

iver

–16.

2–1

20.1

0.03

014

c9r

/04

Uly

uvee

m R

iver

–15.

6–1

19.3

0.08

0

LITHOLOGY AND MINERAL RESOURCES Vol. 43 No. 5 2008


Tab

le 1

. (C

ontd

.)

12

56

78

910

15O

len’

i (66

°01′

N, 1

73°4

1′)

∆δD

= –

92.5

– (

–109

.1)

= 1

6.6‰

15a

11/0

4Sa

line

lake

–10.

5–9

2.5

158.

530

Cl8

2HC

O31

7/N

a53M

g41C

a415

bA

n-17

(2i)

/05

Spri

ng 1

–11.

0–9

8.5

18.3

15c

11r/

04R

iver

in th

e sp

ring

s ar

ea–1

4.7

–109

.114

0.10

015

d10

r/04

Ioni

veem

Riv

er–1

5.2

–116

.60.

020

15e

An-

17(2

r)/0

5R

iver

in th

e sp

ring

s ar

ea–1

4.3

–108

.516

Are

nysh

kynv

aam

(65

°59′

N, 1

73°4

2′ W

) ∆δ

D =

–12

2.4

– (–

100.

1) =

–22

.3‰

16a

12/0

4Sp

ring

–15.

4–1

22.4

128.

370

Cl9

3HC

O36

/Na6

5Ca2

416

bA

n-18

(3i)

/05

Spri

ng 6

–16.

8–1

33.3

6.2

16c

An-

18(3

r)/0

5C

reek

–12.

9–1

00.1

17N

el’p

ygen

veem

(65

°58′

N, 1

72°4

7′ W

) ∆δ

D =

–12

2.6

– (–

108.

6) =

–14

.0‰

17a

14/0

4Sp

ring

–14.

4–1

22.6

76.

870

Cl6

2HC

O33

7/N

a59M

g23C

a16

17b

An-

13(1

i)/0

5Sp

ring

1–1

5.8

–122

.91.

717

c14

r/04

Nel

’pyg

enve

em R

iver

, ups

trea

m o

f sp

ring

s–1

4.5

–108

.615

0.07

017

dA

n-13

(1r)

/05

Nel

’pyg

enve

em R

iver

–14.

3–1

07.9

18V

erkh

ne-N

unya

mov

eem

(65

°25′

N, 1

73°1

8′ W

) ∆δ

D =

–12

8.4

– (–

121.

4) =

–7.

0‰1.

6962

18a

An-

27(8

i)/0

5Sp

ring

35

–17.

1–1

28.4

3618

bA

n-27

(8r)

/05

Cre

ek–1

6.2

–121

.419

Sine

veem

(64

°37′

N, 1

73°4

9′ W

)9.

5082

19a

An-

26(9

i)/0

5Sp

ring

6–1

4.6

–111

.143

20G

etly

ange

n (6

5°12

′ N, 1

72°4

7′ W

) ∆δ

D =

–11

8.9

– (–

110.

7) =

–8.

2‰4.

4532

20a

An-

22(7

i)/0

5Sp

ring

8/2

–15.

4–1

18.9

4320

bA

n-22

(7r)

/05

Cre

ek–1

4.8

–110

.721

Stup

ench

atye

(64

°59′

N, 1

73°5

4′ W

) ∆δ

D =

–13

1.1

– (–

102.

1) =

–29

.0‰

7.27

72

21a

An-

21(5

i)/0

5Sp

ring

1–1

7.3

–131

.12.

721

bA

n-21

(5r)

/05

Cre

ek–1

1.2

–102

.122

Ioni

min

eral

(65

°59′

N, 1

73°5

0′ W

) ∆δ

D =

–12

8.2

– (–

109.

4) =

–18

.8‰

7.28

72

22a

An-

20(4

i)/0

5Sp

ring

3–1

6.6

–128

.25

22b

An-

20(4

r)/0

5C

reek

–14.

3–1

09.4

23Pe

chin

gtan

vaam

(65

°34′

N, 1

73°4

2′ W

) ∆δ

D =

–13

1.2

– (–

118.

5) =

–12

.7‰

23a

An-

6i/0

5Sp

ring

6–1

6.7

–131

.228

2.10

62

23b

An-

6r/0

5C

reek

–15.

9–1

18.5

Not

es:

1 Num

eral

s de

sign

ate

the

shar

e of

ion

in m

g-eq

uiv.

2 Aft

er (

Kie

vski

i et a

l., 2

006)

.

434


POLYAK et al.

Tab

le 2

. C

hem

ical

com

posi

tion

of w

ater

s in

the

exam

ined

hyd

roth

erm

al s

prin

gs o

f th

e C

huko

tka

Peni

nsul

a

Num

ber

in T

able

1Sa

mpl

eSp

ring

, sam

plin

g si

teC

once

ntra

tion,

mg/

lD

ry r

esi-

due,

g/l

t, °C

pHN

aK

Ca

Mg*

HC

O3

Cl

SO4

1a21

/02

Cha

plin

o, s

elf-

disc

harg

ing

bore

hole

87.5

8.61

4800

108

2505

0.95

122

1163

022

519

.28

1b22

/02

Cha

plin

o, V

osto

chna

ya g

roup

, spr

ing

67.8

8.03

4280

110

2425

0.94

9810

990

225

18.9

5

1c23

/02

Cha

plin

o, Z

apad

naya

gro

up, s

prin

g68

.17.

2241

7010

524

550.

8214

.610

780

204

17.9

6

1d24

/02

Cha

plin

o, D

al’n

yaya

gro

up, s

prin

g79

.06.

2543

0010

924

550.

8814

.610

990

232

18.9

8

2a30

/02

Seny

avin

, upp

er g

ryph

on (

no. 1

)78

.08.

6338

611

.792

.20.

1049

717

621.

47

2b31

/02

Seny

avin

, low

er g

ryph

on (

no. 2

)78

.78.

5937

512

88.2

0.09

2971

762

1.50

3a34

/02

Ara

kam

chec

hen,

low

er g

ryph

on37

.48.

3640

09.

372

.10.

5534

730

841.

47

4a40

/02

Kiv

ak, d

isch

arge

nea

r th

e in

door

sw

imm

ing

pool

43.1

8.15

875

1972

10.

4022

2610

634.

78

5a50

/02

Kuk

un, s

prin

g 1

(cub

e)60

.06.

9813

3082

.532

11.

1681

2590

825.

23

5c51

/02

Kuk

un, s

prin

g 2

(dis

char

ge in

the

swim

min

g po

ol)

52.0

7.40

1070

6826

00.

9973

2120

494.

03

5d1a

/04

Kuk

un, s

prin

g58

.06.

9794

074

300

1.13

9826

3081

4.72

6a60

/02

Mec

higm

en, g

ryph

on 1

on

the

righ

t wal

l of

the

valle

y89

.77.

0512

4077

104

1.81

190

2050

803.

93

6b62

/02

Mec

higm

en, g

ryph

on 2

in th

e ce

ntra

l par

t of

the

fiel

d64

.36.

8912

8078

108

1.86

217

2100

814.

08

7a70

/02

Bab

ushk

iny

Och

ki, n

orth

ern

gryp

hon

20.1

6.45

1790

167

930

153

1928

3860

340

9.26

7b2/

04B

abus

hkin

y O

chki

, nor

ther

n gr

ypho

n21

.06.

3119

5017

096

015

818

1042

6036

09.

58

7c71

/02

Bab

ushk

iny

Och

ki, s

outh

ern

gryp

hon

13.7

6.66

1930

168

954

115

1897

4080

391

9.15

7e72

/02

Bab

ushk

iny

Och

ki, s

prin

g ne

ar th

e pi

edm

ont o

f th

e ar

ch14

.219

1016

193

214

918

9039

9034

29.

28

8b81

/02

Tum

anny

e, g

roup

2, s

prin

g55

.110

0068

.610

82.

8320

717

1072

3.40

9a90

/02

Dez

hnev

, Bor

ehol

e V

erkh

nyay

a69

.05.

9354

0020

417

232.

2424

1160

099

19.6

0

9b91

/02

Dez

hnev

, Bor

ehol

e T

sent

ral’

naya

60.1

7.83

5000

200

1683

2.32

2411

350

9219

.76

9c92

/02

Dez

hnev

, Bor

ehol

e N

izhn

yaya

52.8

5100

211

1611

2.38

19.5

1199

010

019

.29

10a

3/04

Nes

hkan

, upp

er g

roup

, spr

ing

52.0

6.05

9800

710

3400

24.8

122

2240

03

37.1

4

11a

4/04

Tey

ukei

, spr

ing

6.0

6.25

4200

210

1700

17.4

7999

003

17.6

4

12a

6/04

Kub

, spr

ing

7.0

1300

9324

038

.055

024

905

4.48

13a

7/04

Vyt

khyt

yave

em, s

prin

g65

.06.

4688

033

276

1.18

330

1780

73.

45

14a

8/04

Ora

nzhe

vye,

spr

ing

14.0

6.40

6900

400

5350

6723

220

950

1736

.23

15a

11/0

4O

len’

i, sa

line

lake

15.0

7.58

1580

9310

065

014

2039

0029

8.53

16a

12/0

4A

reny

shky

nvaa

m, s

prin

g12

.018

4011

059

012

448

843

3027

8.37

17a

14/0

4N

el’p

ygen

veem

, spr

ing

7.0

6.59

1470

5636

030

824

6024

1030

6.87

* M

g co

nten

t was

det

erm

ined

by

the

ICP-

MS

tech

niqu

e.



CHEMICAL COMPOSITION OF THERMAL WATERS

Many springs discharge gases usually dominated bynitrogen. Only gases from the Babushkiny Ochki andOlen’i springs near Lake Ioni and those from theNel’pygenveem springs located further to the east (Fig. 1,points 7, 15, and 17, respectively) largely consist of car-bon dioxide (~80–90 vol %). In some other springs, suchas Stupenchatye (Point 21), Mechigmen (Point 6), andothers, the gaseous phase also contains up to 30–60 vol %of CO2 (the remainder is represented by N2). In general,relatively CO2-rich springs are mostly confined to theKolyuchinskaya–Mechigmen Depression that repre-sents a zone of recent geodynamic activity, which isevident from sporadic manifestations of Late Cenozoicbasaltic volcanism and concentration of recent seismicevents (Romanova and Zhukova, 1970a, 1970b;Kryukov, 1980; Vladimirtseva et al., 2001; and others).

The integral mineralization of thermomineralwaters is highly variable: from ~1.5 g/l in the Senyavinsprings (Point 2) to ~20 g/l in the Chaplino and Dezh-nev springs (points 1 and 9, respectively). In the Nesh-kan (Point 10) and Oranzhevye (Point 14) springs, itexceeds values typical of seawater (Table 2). Relativecontents of some mineral components in thermalwaters of Chukotka differ from their values in seawater.For example, it is known that the Cl/Br value for seawa-ter is as high as 292. Based on this ratio, the Chukotkathermal waters are divided into two groups. In the firstgroup, which includes springs of the Bering Sea coast,this coefficient is lower as compared with that in seawa-ter (<200). The second group unites CO2-rich springs ofthe Lake Ioni and Chukchi Sea coast areas, where itsvalues range from 370 to 433.

In terms of anion compositions, waters of mostsprings are classed as chloride and chloride–hydrocar-bonate types with Cl ion and HCO3 ion concentrationsamounting to at least 90 and 17–37 mg-equiv %,respectively (Fig. 3). The last type is characteristic ofthe above-mentioned CO2-rich springs of the Ko-lyuchinskaya–Mechigmen zone and its peripheralareas. Sulfates in Chukotka thermal waters are usuallypresent as insignificant admixture: their contents are<82 mg/l in 14 groups of springs (in four cases,<10 mg/l) and up to 100 mg/l or higher only in thecoastal Chaplino, Dezhnev, and Babushkiny Ochkisprings (100, 232, and 391 mg/l, respectively).

In terms of cation compositions, waters under con-sideration are of the sodium–calcic type. The Ca ionconcentration in them ranges from ~10 to 48 mg-equiv %(Fig. 3), which exceeds the concentration in seawater,positively correlates with the total mineralization(Fig. 4) and contents of Cl, Na, K, Rb, Sr, and someother elements. The Mg ion in Chukotka thermomin-eral waters is almost always subordinate. Its content inwaters of 13 groups of springs is <100 mg/l (in sixcases, <10 mg/l) and increases to 130 and 184 mg/lonly in CO2-rich waters of the Lake Ioni area in the

Babushkiny Ochki and Arenyshkynvaam (Point 16)springs, respectively. In waters of the Nel’pygenveemand Olen’i springs, the Mg ion concentration is 270 and690 mg/l (or 23 and 41 mg-equiv %), respectively.

The enrichment in Ca against the background ofSO4 and Mg depletion is a most distinct feature of theChukotka thermomineral waters that makes them dif-ferent from seawater. This may be a consequence ofexchange reactions in the water–rock system at temper-atures exceeding 200°C (Krainov et al., 2004). Highlymineralized Cl–Ca brines are characteristic of thedecelerated exchange zone developed at lower hydro-geological levels. In such brines, dissolved matter andits carrier are either syngenetic, when they are primarilysedimentogenic (isotopically heavy) waters of normalsea or saliferous basins, or genetically different, whenthey are brines resulted from the leaching of evaporiticsequences by the fresh meteogenic (isotopically light)waters.

The sulfate and magnesium deficiency is usuallyattributed to metamorphism of sedimentogenic seawa-ters, when Mg2+ is fixed in clay minerals and carbon-

ates, while S is removed during sulfate reduction.Isotopic study of the sulfate sulfur composition in sixgroups of springs revealed that the δ34S value in theDezhnev and Mechigmen thermal waters, where SO4concentrations are less than 100 mg/l, varies from 19.9to 20.2‰ (Polyak et al., 2004). They correspond to typ-

O42–

1

2

3

9

7 6

5

4

8

10

–12°

–10°

–8°

1 2 3 4

–6°

Fig. 2. Average annual air temperatures and total atmo-spheric precipitation in Chukotka, after (Gidrogeologiya…,1972). (1–4) Total precipitation, mm: (1) 200–300, (2) 300–400, (3) 400–500, (4) 500–600. Numerals designate meteo-rological stations and investigation sites of frost conditions:(1) Pevek, (2) Cape Schmidt, (3) Iul’tin Settlement,(4) Uelen Settlement, (5) Lorino Settlement, (6) Provi-deniya Bay (Ureliki Settlement), (7) Nunligran Settlement,(8) Egvekinot Settlement; (9) Amguema Settlement,(10) Anadyr.

436


POLYAK et al.

ical δ34S values of sulfate in seawater. The increase insulfate concentrations in other springs is accompaniedby the drop of this value to +11.7‰ (e.g., the Babush-kiny Ochki spring), indicating admixture of the isotopi-cally lighter sulfur. This admixture in groundwater mayby provided by the oxidation of dispersed sulfides. Thisis confirmed by some growth of S, Fe, and Al concen-trations in thermal waters, although heavy metals donot demonstrate similar growth.

The observed correlation between δ34S values andsulfate concentrations could be determined by sulfatereduction in the closed system, because exhaustion ofdissolved sulfate should result in the transformation ofthe sulfur isotopic composition due to 32S isotope fixingin the sulfide phase. The greater the reduction degree ofsulfate sulfur, the heavier the isotopic composition ofsulfate ion against the background of decrease of itsconcentration in the solution. Thus, sulfate reduction ingroundwater is accompanied by lightening of the pri-mary isotopic composition of sulfate sulfur in them;

i.e., the latter becomes closer to that in springs withmaximal concentration of this element and, conse-quently, substantially different from its composition inseawater. At the same time, it seems strange that theδ34S value in waters of the Dezhnev and Mechigmensprings appeared to be exactly equal (not lower orhigher) to that in seawater.

Similar to other areas of the cryolithozone develop-ment, occurrence of highly mineralized waters withnegative temperatures (the so-called cryopegs), whichare formed under the permafrost sequence due to waterphase freezing during the formation of subsurface ice,represents a peculiar feature of the subsurface hydro-sphere in Chukotka (Tolstikhin, 1941; Ponomarev,1960; Gidrogeologiya…, 1972; Kononova, 1974; Fotiev,1978; and others). The initial temperature of cryogenictransformation of groundwaters depends on their pri-mary mineralization: seawater (~35 g/l) remains liquidat temperatures of –1.8 to –1.9°C, while brines withmineralization of 200 g/kg preserve their liquid stateeven at –20°C. Cryogenic metamorphism of subsurfacesolutions is accompanied by both the growth of totalmineralization and its qualitative changes. “Crystalliza-tion of freshwater …in a freezing solution … isaccompanied by decrease in Ca2+ concentrationsagainst the background of simultaneous increase inNa+ and Mg2+ … contents” (Fotiev, 1978, p. 38). Incontrast, cryogenic concentration of seawater is accom-panied first by increase in contents of NaHCO3,Na2SO4 and chlorides of Na, Mg, and Ca and then bydecrease in contents of sodium sulfate at temperaturesof ~–8 to –23°C (Fotiev, 1978, Fig. 6). It is unclear sofar to what extent such a decrease explains the above-

mentioned S deficiency in thermal waters ofChukotka relative to its content in seawater.

Phase transformations of water are accompanied byisotope fractionation, i.e., transfer of D and 18O into thenewly forming ice (Vetshtein, 1982), resulting in theisotopically lighter composition of water and highersalt load of corresponding cryopegs. Variations in theδD and δ18O values in the frozen sequence are deter-mined by isotope fractionation in the water–ice systemduring the crystallization and melting of ice underchangeable climatic conditions. In closed systems(without additional water influx), the isotopic composi-tion of the newly forming ice becomes successivelyheavier. This is responsible for its significant variationswithin a single ice body: for example, δD values in itsdifferent parts may differ by 30‰ (Vasil’chuk and Kot-lyakov, 2000). At the same time, variability of the iso-topic composition in subsurface ice may reflect cli-mate-dependent variations in the isotopic compositionof atmospheric precipitation during cryozone develop-ment. Published data on the isotopic composition ofChukotka subsurface ice are cited below. Unfortu-nately, the isotopic composition of waters in cryopegsof the Chukotka region is unknown so far. Availabledata on their chemical composition are presented in

O42–

0

20

40

60

80

100

0 20 40 60 80 100

0

20

40

60

80

100

Mg,

mg-

equi

v % Ca, m

g-equiv %

Na + K, mg-equiv %0 100

80

60

40

20

0

100806040200

100

80

60

40

20

SO4, m

g-eq

uiv

%

Cl, mg-equiv %

HCO3, mg-equiv %

Fig. 3. Chemical composition of thermomineral waters inChukotka.



Table 3. Figure 4 demonstrates the correlation of watermineralization with Cl, Na, and Ca concentrations. Theplot shows data points corresponding to these cryopegs.

Chukotka cryopegs are variable in terms of theirmineralization type. For example, waters recoverednear the town of Anadyr and Nunligran settlement areclose in this respect to seawater, while waters observednear the town of Pevek differ from the latter in terms oftheir cation composition: Ca and Mg contents arehigher as compared with Na concentration. The Ca/Mgvalue in cryopegs penetrated by Borehole Pevek-10 ispractically similar to that in Borehole Anadyr-93 (1.55and 1.52, respectively). In boreholes drilled in the Nun-ligran settlement, this ratio is substantially lower (0.84–0.98). This is likely explained by regional differences inthe composition of primary waters subjected to cryo-genic metamorphism and/or by peculiarities of this pro-cess in different areas of Chukotka.

As was mentioned, the Neshkan and Oranzhevyesprings (Fig. 1, points 10 and 14, respectively) dis-charge waters with mineralization higher than in sea-water. Corresponding data points in plots demonstrat-ing correlation of Cl, Na, and Ca concentrations withthe total mineralization form trends similar to datapoints of both other thermomineral springs and cry-opegs of the Nunligran and Anadyr areas (Fig. 4). Tak-ing into consideration this similarity and differencesmentioned above between Chukotka cryopegs in thetotal salt contents, one can assume the contribution of

subpermafrost waters with different degrees of miner-alization and cryogenic metamorphism to the formationof the salt composition in different thermal waters.According to Fotiev, the last process results, however,in an enrichment of freezing waters with Mg, while cor-responding thermal waters become depleted in this ele-ment. Thus, the role of cryometamorphism in the for-mation of their chemical composition is unclear.

METHODS

The chemical composition of liquid and gaseousphases in thermomineral fluids was determined in linewith standard techniques at the Geological Institute,Moscow. The water isotopic composition (δD andδ18O) was analyzed in the IGEM RAS at the FinninganDELTAphis mass-spectrometer. δD values were mea-sured by the method of direct decomposition of waterat hot (800°C) metallic chrome using (FinninganH/Device); measurement accuracy of H isotopic com-position was ±0.2‰. The δ18O values were determinedusing the classical method of isotopic equilibrating ofwater samples with CO2 at t = 25°C. Reproducibility ofδ18O measurements in parallel experiments was±0.15‰. The total accuracy was at least ±0.25‰. Allmeasurements were controlled using standardMAGATE (IAEA) samples OH-1, OH-2, OH-3, andOH-4.

105

104

103

102

101

103102101100

Total mineralization (M), g/l

[X], mg/l

R2 = 0.98

SeawaterR2 = 0.85

Neshkan spring

Boreholes Nunligran-55 and Nunligran-57

Borehole Anadyr-93T = –6, 6°C

1

2

3

4

5

Fig. 4. Total mineralization (M) and concentrations of Cl, Na, and Ca ions ([X]) in groundwaters of Chukotka. (1–3) Concentration:(1) Cl, (2) Na, (3) Ca; (4, 5) regression lines: (4) [Cl]-M, (5) [Ca]-M. Solid symbols of elements correspond to seawater.

438


POLYAK et al.

–18 –17 –16 –15 –14 –13 –12 –11 –10δ18O, ‰

–140

–130

–120

–110

–100

–90

–80

δD, ‰

y = 5.98x – 22.7R2 = 0.8225

21b

1g

4b

Bethel

9„

16c

1d

0‡

0b9d

1f17c

2d3· 5f

10b

6c

7f5f

7g7h15c

14c7i

18b13b

14b23b

20b15c

12b

12c2c

7f, 11b, 15e, 17c, 22b

Barrow

Fig. 5. Isotopic composition of surface waters in eastern Chukotka at the examined discharge sites of thermomineral fluids. Datapoints correspond to numbers in column 1 of Table 1. Solid and dashed lines are the regression and Craig lines, respectively. Trian-gles designate average annual δD and δ18O values of atmospheric precipitation obtained at the Bethel (60.78° N) and Barrow(71.30° N) stations (Yurtsever and Gat, 1981).

OXYGEN AND HYDROGEN ISOTOPE COMPOSITION IN CHUKOTKA WATERS

Table 1 presents data on deuterium and 18O contentsin waters of the Chukotka region. δD and δ18O valuesare given relative to the international SMOW standard.Table 4 summarizes variations in these values in waterreservoirs that are of interest in the context of the prob-lem in question. The table demonstrates that waters ofthe Bering Sea are close in their isotopic composition toaverage seawater, although they are slightly depleted inheavy isotopes due to their freshening in the coastalzone. On the contrary, surface (creeks, rivers, andlakes) and thermomineral waters of the Chukotka Pen-insula are characterized by substantially different isoto-pic compositions of hydrogen and oxygen.

Surface Waters

Surface water reservoirs (rivers, creeks, lakes, andwells) fed by atmospheric precipitation and surfaceflow were sampled at 21 of 23 examined dischargelocalities of hydrothermal springs. In the δD–δ18O dia-gram, location of all 36 data points available for surfacewaters (Table 5, selection 1) is controlled by lineardependence δD ≈ 6δ18O – 22.7 (Fig. 5). This depen-dence differs slightly from the global “Craig line” δD =

8δ18O + 10 that reflects the isotopic lightening of atmo-spheric precipitation toward higher latitudes (Craig,1961). Data points of average annual (average weightedrelative to integral precipitation during the year) δD andδ18O values in atmospheric precipitation of neighbor-ing Alaska, where it was studied at the Bethel and Bar-row meteorological stations (Yurtsever and Gat, 1981),fall practically onto the “Chukotka” trend. Data pointsof these two Alaskan meteorological stations, which arelocated slightly south and north of the study area,respectively, limit the spectrum of δD and δ18O valuesobtained for surface waters of the Chukotka Peninsula.Chukotka surface waters appear to be slightly richer indeuterium and 18O as compared with atmospheric pre-cipitation at the Bethel Station only in four cases. Thisenrichment is best manifested in two small creeks nearthe Chaplino and Kivak thermomineral springs, whereit reflects probably their dominant feeding by summerprecipitation. In addition, the isotopic composition ofH2O in small creeks should be slightly enriched in deu-terium and 18O due to evaporation (at least, morestrongly than in rivers). Therefore, water samples fromrivers reflect the isotopic composition of meteogenicwaters more adequately. Except for samples taken fromsmall creeks and lower reaches of rivers drainingsprings and a sample with the strange anomalous result



1716

68

22

715

12

11

10

13

14

23

2018

19

2 3

–105

–115

14

9

21

(a)

–85–90–95

–100–105–110–115–120–125

δD, ‰

169170171172173174175Western longitude

δD = –8.863(° W) + 1426.8R2 = 0.6283 (n = 24)

River watersCreeks

(b)

176° 175° 174° 173° 172° 171° 170° W

67° N

66° N

65° N

176° 175° 174° 173° 172° 171° 170° W

65°

67°

66°

Fig. 6. Lateral variations in the δD values in surface waters near thermomineral springs of eastern Chukotka (numbers in Fig. 1).(a) Schematic δD isolines; (b) correlation between δD values in river waters and longitude of sampling sites (straight line shows thetrend).

(Table 1, Point 21b), the distribution of 25 data pointsavailable for surface waters is governed by lineardependence with the correlation coefficient R = 0.93(Table 5, Selection 2).

Atmospheric precipitation of Alaska demonstrates adistinct universal lightening of its isotopic compositiontoward higher latitudes. In contrast, Chukotka watersshow a substantially more distinct longitudinal trend:decrease in δD and δ18O values from the east to west ininterior areas of the peninsula (Fig. 6a). Correlation

between the hydrogen isotope composition in surfacewaters and western longitude of the sampling point canbe formally approximated by the regression equationδD = –8.863(deg) + 1426.8, where (deg) corresponds towestern longitude of the particular point determinedwith an accuracy of 0.01n° (Fig. 6b). In the selectionunder consideration (n = 24), this correlation is statisti-cally significant: R2 = 0.6283; i.e., |R| = 0.792 > Rcrit =0.390.

5

0

440


POLYAK et al.

Tab

le 3

. Pa

ram

eter

s of

cry

opeg

s in

the

Chu

kotk

a Pe

nins

ula

Obj

ect

T, °

CM

, g/l

Con

cent

ratio

ns o

f co

mpo

nent

s, m

g/l/m

g-eq

uiv

%C

oeff

icie

nts

(mg-

equi

v/m

g-eq

uiv)

Sour

ce1

Na

+ K

Mg

Ca

Cl

SO4

HC

O3

Na/

Cl

Ca/

Cl

Mg/

Cl

SO4/

Cl

Ca/

Mg

Peve

k, B

oreh

ole

10,

0.2–

0.3

km a

way

fr

om th

e se

a–2

3813

1631

2480

7025

206

232

680.

080.

570.

360.

011.

571

836

5699

0.8

0.2

Nun

ligra

n Se

ttle-

men

t, B

oreh

ole

57,

3 km

aw

ay f

rom

th

e se

a

<–

0.4

(–2.

5)50

.9

1447

118

2025

1831

900

100

91

0.70

0.14

0.17

0.00

0.84

1

7016

1499

.50.

30.

2

Nun

ligra

n Se

ttle-

men

t, B

oreh

ole

55,

0.4

km a

way

fro

m

the

sea

<–

0.4

(–2.

5)57

.4

1653

117

0227

4435

100

250

49

0.73

0.14

0.14

0.01

0.98

1

7214

1499

.20.

70.

1

Ana

dyr,

Bor

ehol

e 93

, pen

etra

tion

5 m

–6.

610

0.7

2600

030

0075

0059

000

2750

2440

0.68

0.23

0.15

0.03

1.52

264

.714

21.3

94.5

2.2

2.3

Kaz

achk

a D

epre

s-si

on–2

.280

.20.

640.

160.

230.

023

Sea

35.0

1114

712

9441

319

353

2712

142

0.89

0.04

0.19

0.10

0.19

478

.718

.13.

290

.59.

30.

1

Spri

ng N

eshk

an2

5237

.110

510

6134

0022

400

312

20.

720.

270.

010.

0033

.79

572

.10.

3 27

.6

99.7

<

0.01

0.

3

Not

es:

1 Sou

rce:

(1)

(G

idro

geol

ogiy

a…, 1

972;

(2)

(Po

nom

arev

, 196

0); (

3) (

Fotie

v, 1

978)

; (4)

(H

orn,

197

2); (

5) O

ur d

ata.

2 Dat

a ar

e gi

ven

for

com

pari

son.



Thermomineral Waters

Thermomineral waters of the Chukotka region aregenerally depleted in 18O and deuterium as comparedwith their surface counterparts (Tables 1, 4). The scatterrange of δD and δ18O values in them is wider: 41.8 and7.1‰, respectively. In surface water, these parametersare 31.9 and 5.3‰, respectively. Water from the miner-alized (8.53 g/l) and warm (15°C) Olen’i springsappeared to be isotopically heaviest: δD = –92.5‰ andδ18O = –10.5‰ (Table 1, Point 15a). This is probablyexplained by loss of the isotopically light water due toevaporation and shift of the isotopic compositiontoward enrichment of the remaining water in the heavyoxygen and hydrogen isotopes.

In the δD–δ18O plot (Fig. 7), half of data points fallinto the field corresponding to surface waters. This pro-vides grounds for impression that the correspondingthermomineral springs are fed only by local infiltrationwaters, as it follows from the concepts of practicallycomplete spatial coincidence between feeding and dis-charge zones of such circulation systems (Shvetsov,1951; Ponomarev, 1960). Comparison of δD values inthermomineral and surface waters reveals, however,that thermal waters in 16 groups of springs are depletedto a variable extent in deuterium relative to the neigh-boring surface waters.

Similar to surface waters, the lateral distribution ofδD values in thermomineral solutions also reveals spa-

tial (although principally different) regularity. In thesouthern and eastern Chukotka Peninsula, the isotopiccomposition of thermomineral waters in most springs isclose to that of local freshwaters and their data pointsform a regression line with the similar slope in Fig. 7(Table 5, Selection 3). In the Senyavin and Verkhne-Nunyamoveem groups of springs (points 2 and 18,respectively) in this part of the peninsula, the δD valuesare substantially lower than in surface waters. Never-theless, their data points 2a, 2b, and 18a are locatedalmost at the same “surface” trend (cf. regression equa-tions in selections 2 and 3 in Table 5). These points,anomalous for the southeastern Chukotka Peninsula,appear simultaneously in the field of thermomineralwaters (Fig. 7) that are most depleted in deuterium(δD < –120‰). The latter points are located, however,in the Kolyuchinskaya–Mechigmen Depression ratherthan the westernmost part of the area, where surfacewaters are most depleted in this isotope (Fig. 8a). Thisinference is substantiated by concentration of datapoints available for thermomineral waters in the areabetween 172.8° and 173.8° W (Fig. 8b), i.e., by lack ofcorrelation between δD values and longitude of the cor-responding sample point notable in surface waters.

At the same time, springs depleted in deuteriumdemonstrate a substantial enrichment in the heavy iso-tope 18O (relative the Craig line) and form flatter trendsin the δD–δ18O plot (Fig. 7). The similarity between

Table 4. Variation ranges of δD and δ18O in different H2O reservoirs

Type of natural waterδD, ‰ δ18O, ‰

min max min max

Bering Sea1 –26.82 –10.05 –3.38 –1.31

Alaska, atmospheric precipitation2 –129.80 –98.60 –17.64 –12.63

Chukotka

surface waters –121.41 –89.46 –16.38 –11.12

thermomineral waters –134.223 –96.914 –17.523 –12.624

subsurface ice5–223.66 –79.67 –29.26 –11.27

–191.58 –90.29 –24.98 –12.59

Notes: 1 Our measurements: minimal and maximal values are in the Kivak Lagoon and Senyavin Strait, respectively.2 Average annual parameters determined at the Bethel (60.78° N) and Barrow (71.30° N) meteorological stations (Yurtsever andGat, 1981).3 Babyshkiny Ochki springs.4 Dezhnev springs; water from the Lake Olen’i (Ynpyneveem) springs is isotopically even heavier: δD and δ18O values are –92.45and –10.52‰, respectively.5 After (Vasil’chuk, 1992; Vasil’chuk and Kotlyakov, 2000). Italics designate samples calculated using equation δD = 8δ18O + 10(Craig, 1961).6 Regenerated vein ice (20600 yr) in the Amguema River valley. In regenerated vein ice dated back to <40 ka near Anadyr,the measured δ18O and calculated δD values are –27.3 and –208.4‰.7 Recent structural ices at the initial part of the Mechigmen Estuary.8 Holocene regenerated vein ice, Pekul’nei Range.9 Recent structural ice, Onemen Bay, ~20 km away from Anadyr.

442


POLYAK et al.

Table 5. Parameters of particular selections of paired δ18O and δD values in waters of the Chukotka Peninsula

Selec-tion no. Selections

Numbers of groups of springsin Fig. 1, Numbers of samples

in column 1 of Table 1n Equation of

regression R2 |R| |Rcrit|

Surface waters

1 All samples All (0–7, 9–18, 20, 22, 23) 36 5.9828x – 22.7057 0.8225 0.9069 0.329

2 Without samples from creeks and lower reaches of rivers

(without 1g, 4b, 5e, 5f, 9d, 9e, 12b, 16c, 18b, 20b, 21b, 22b)

25 7.4609x – 0.9950 0.8734 0.9346 0.335

Thermomineral springs

3 Southeastern margins, anomalies* included

1–5, 9, 18–20 18 7.5879x + 0.5510 0.9713 0.9855 0.468

4 Southeastern margins without anomalies*

1, 3–5, 9, 19, 20 15 8.059x + 6.9705 0.9059 0.9518 0.514

5 Central areas 6–8, 15–17, 21–23 16 3.5905x – 70.7614 0.7095 0.8423 0.497

6 Central areas without the Pechingtanvaam springs

6–8, 15–17, 21–22 15 3.5779x – 70.9298 0.7079 0.8414 0.514

7 Northern margin 10–14 5 2.8740x – 75.3126 0.5565 0.746 0.878

8 Central areas + northern margin

6–8, 10–17, 21–23 21 4.7684x – 50.2403 0.6973 0.8351 0.433

9 Central areas + northern margin + anomalies of southeastern Chukotka*

2, 6–8, 10–18, 21–23 24 4.4765x – 54.6683 0.6958 0.8227 0.390

* “Anomalous” springs of southeastern Chukotka: Senyavin (no. 2) and Verkhne-Nunyamoveem (no. 18).

regression equations in selections 5 and 6 (Table 5)shows that the Pechingtanvaam springs (Point 23) arecloser to their counterparts in the Kolyuchinskaya–Mechigmen zone than to the southern springs in termsof the isotopic composition of water.

Selection 7 (Table 5), which includes a small num-ber of samples from thermomineral springs nearest tothe Neshkan Lagoon and Kolyuchinskaya Estuary,lacks correlation between δD and δ18O values (|R| <Rcrit). Nevertheless, when this selection is united withSelection 8 (Kolyuchinskaya–Mechigmen zone) andSelection 9 (“anomalous” springs in the southern partof the peninsula), correlation between δD and δ18O val-ues appears to be statistically significant (|R| > Rcrit).

Minimal δD values in waters of the Kolyuchin-skaya–Mechigmen springs reflect their distinctregional specificity. It is of extreme interest that thespecificity is also evident from other isotopic–geochemical features of springs, which make them dif-ferent from their counterparts discharging beyond thedepression. In addition to the above-mentioned enrich-ment of their gaseous phase in carbon dioxide, specificisotopic parameters of carbon in the carbon dioxide, aswell as of helium and nitrogen that are present in thisphase, are also notable. All these parameters are inde-pendent from each other, and their coordinated spatial

variability deserves special analysis, which will bemade in other publications.

DISCUSSION

Probable Factors Responsible for Isotopic Specifics of Thermomineral Waters

The performed study demonstrates that approxi-mately half of hydrothermal springs are depleted indeuterium and 18O as compared with local surfacewaters. Provided that these hydrothermal springs arefed only by atmospheric precipitation (i.e., they wereformed on account of the precipitation), such a defi-ciency might be explained by the fact that all the sam-ples were taken in July–August. In contrast, winter pre-cipitation, which prevails usually in the subsurfaceinfiltration flow that feed springs, is depleted in deute-rium and 18O.

Isotopic differences between thermomineral andlocal surface waters may in principle be explained bydifferent altitudes of their feeding provinces. It isknown that increase in altitude results in depletion ofatmospheric precipitation in heavy isotopes with gradi-ents ∆δD/∆h = 1.5–4‰ and ∆δ18O/∆h = 0.15–0.5‰ perevery 100 m of altitude (Yurtsever and Gat, 1981). Inthis case, feeding areas of thermomineral waters shouldbe located at least 500–600 m above their discharge



localities. In the Kolyuchinskaya–Mechigmen Depres-sion, the relief amplitude amounts to 700–800 m, andthe Senyavin springs (Point 2) discharge near Mt.Iskhodnaya (1158 m) representing the highest summitin eastern Chukotka. Therefore, such an explanation ofisotopic lightening of thermal waters relative to localsurface waters is theoretically admissible.

The depletion of thermomineral waters in deuteriumrelative to local surface waters could also reflect other(colder) paleoclimatic conditions of their feeding areas.However, local differences between these conditionswithin the Chukotka Peninsula seem improbable.Therefore, contribution of the water component withlow δD and δ18O values (lower than in surface waters ofthe study area) into the formation of thermomineralwaters is the most probable factor responsible for theirdeuterium deficiency as compared with surface waters.

Such values are characteristic, for example, of sub-surface ice. In Chukotka, its isotopic composition wasstudied only for uppermost parts of the geological sec-tion in separate outcrops near Lake Koolen, in theAnadyr area, and in the Tanyurer (Pekul’nei Range) andAmguema river valleys (Vasil’chuk, 1992; Vasil’chukand Kotlyakov, 2000). Table 4 and Fig. 9 present theresults of these studies. It is seen that δD and δ18O val-

ues in ice of the Chukotka Peninsula are highly vari-able. Such a wide scatter is attributed to variability offormation settings of ice bodies: degree of closeness ofhydrological systems and climatic conditions. Forexample, radiocarbon dating of sequences enclosingice bodies revealed that δ18é values in Upper Pleis-tocene ice which is believed to be related to colder cli-matic conditions in the past (Vasil’chuk and Kotlyakov,2000) are generally 3–7‰ lighter than in recent ice.

Feeding of thermal waters by meltwaters of adegrading frozen sequence is refuted by the followingunavoidable inference from such assumption: subge-lisol in the discharge zone of thermal waters should per-manently grow; otherwise, “ice” feeding of the hydro-thermal system by water (consequently, influx of lightH and O isotopes) should stop. The growth of subge-lisol is considered a nonstationary process in manyrespects: it should be accompanied by changes ingeometry of the ascending hydrothermal flow and cor-responding changes in its temperature and yield. Thescale and rate of such a process should depend on thick-ness of the frozen sequence, yield of hydrothermalwaters, and their temperature.

When considering the probable role of subsurfaceice in the formation of thermal waters, one should take

–10–12–14–16–18–20δ18O, ‰

–140

–130

–120

–110

–100

–90

–80

δD, ‰

1

2

3

4

5

6

7

8

9

10

Hydrothermal springs of southeastern Chukotkay = 8.06x + 6.97

Hydrothermal springs of the

y = 3.6x – 71

“Oxygen shift”

Kolyuchinskaya–Mechigmenzone

Fig. 7. Hydrogen and oxygen isotope compositions in surface waters and thermomineral springs of eastern Chukotka. (1) Datapoints of local surface waters; (2–4) data points of waters from thermomineral springs: (2) southern and eastern margins of the pen-insula, (3) northern margin (vicinities of Neshkan Lagoon and Kolyuchinskaya Estuary), (4) central areas (Kolyuchinskaya–Mechigmen Depression and its framing); (5) Craig line; (6) field of data points corresponding to local surface waters; (7) regressionline for local surface waters; (8, 9) regression lines for thermomineral springs of the peninsula: (8) southeastern marginal area,(9) central area; (10) deep-sourced component A (for explanation, see the text).

444


POLYAK et al.

into account the fact that this ice is characterized byvery low mineralization: its maximal value usuallydoes not exceed 124 mg/l (average 35–69 mg/l) in vari-eties studied in the Chukotka (Vasil’chuk, 1992). Mix-ing of waters formed during the melting of such icewith infiltrating meteogenic waters, i.e., two fresh com-

ponents, cannot provide mineralized waters that dis-charge in hydrothermal springs.

Such waters could seemingly originate from themixing with seawaters. Figure 10 demonstrates, how-ever, lack of universal correlation between chlorine anddeuterium concentrations in thermomineral waters. The

10

11

1213

14

21 22 167

15

8

17

9

–120

–125–130 6 5

23

18

–100

20

–125

–115

–110

–105

–100

32

14

0

–120

(‡)

–80

–90

–100

–110

–120

–130

–140169170171172173174175176

Western longitude

(b)δD, ‰

River watersCreeksHydrothermal springs

176° 175° 174° 173° 172° 171° 170° W

67°

66°

65° 65° N

66° N

67° N

Fig. 8. Lateral variations in the δD values in waters of thermomineral springs in eastern Chukotka (numbers in Fig. 1). (a) SchematicδD isolines: dashed line contours the Senyavin negative δD anomaly (out of scale); (b) correlation between δD values in river watersand longitude of sampling sites. The hatched area corresponds to the field of data points obtained for river waters. The straight lineshows the trend in Fig. 6b.

19



conjecture that Chukotka thermal waters resulted fromthe mixing of seawaters with the isotopically lightmeteogenic variety automatically implies the existenceof isotopically diverse freshwater reservoirs with δDvalues ranging from –110 to –250‰. Such a range ofvalues is substantially wider as compared with thoseestablished in surface waters of the Chukotka Penin-sula. At the same time, this range is similar to thatobserved in subsurface ice bodies (Table 4). Hypothet-ical speculations on diversity of ice-related freshwaterreservoirs with a single (purely “marine”) source formineralization of thermal waters cannot explain theabove-mentioned differences in the mineralizationspectrum observed between thermomineral waters andthis source: excess of Ca and deficiency Mg and SO4relative to seawater.

Moreover, such speculations cannot explain the for-mation of thermomineral waters with mineralizationexceeding the value in seawater, which discharge in theNeshkan and Oranzhevye springs (Fig. 1, Table 1,points 10 and 14). Judging from all these features, onlythe above-mentioned cryopegs, i.e., highly mineralizedgroundwaters (with negative temperatures), whichoccur in some areas of Chukotka, may provide dis-solved salts for the thermomineral waters. Due to isoto-pic lightening of the subpermafrost water during itsfreezing, δD and δ18O values in cryopegs are lower thanin the conjugate subsurface ice. Unfortunately, directdata on δD and δ18O values in cryopegs of Chukotkaand their lateral variability are unavailable so far.Therefore, their real role in the formation of the isoto-pic composition of waters in the springs examinedremains unknown.

In any event, the occurrence of waters depleted inheavy hydrogen and oxygen isotopes (relative to localsurface waters) in thermomineral springs of Chukotkais beyond doubt.

Isotopic Composition of Deep-Sourced Component A

If we assume that some deep-sourced component iscommon for all deuterium-deficient (relative to localsurface waters) thermomineral springs, its isotopicparameters may be determined using the followingtechnique. In the δD–δ18O diagram, thermomineralwaters with particularly distinct deuterium deficiency(Table 5, Selection 5) provide a regression line δD =3.6δ18O – 70.1. The regression line of surface waters(Selection 2) is characterized by a steeper slope. Sincea hypothetical “hydrogen-light” deep-sourced compo-nent should be diluted to some extent by surface watersduring the discharge, the intersection point of regres-sion lines obtained for selections 2 and 5 in the δD–δ18O diagram should correspond to the isotopic compo-sition of water characterizing the required component,i.e., to point A in Fig. 7, where δ18O = �–19‰ andδD = �–138‰.

The isotopic composition of water discharged inthermomineral springs may be formed in two ways. Inthe case of simple mixing of component A with surfacewaters, data points corresponding to isotopic composi-tions of mixtures should be located along the surfacewater line in the δD–δ18O diagram. Precisely this ischaracteristic of thermal waters in southeasternChukotka: equations of regression lines in selections 2and 3 are practically identical. Deuterium-deficientthermomineral waters demonstrate a distinct shift ofdata points to the right from the surface water line. Thisimplies a variation in the isotopic composition of com-ponent A prior to its mixing with surface waters.

Variation of the isotopic composition of water insubsurface reservoirs is related to its interaction withhost rocks at elevated temperatures. Therefore, thehydrogen isotope composition in thermomineral watersdepends only on proportion of component A mixedwith surface waters, while the oxygen isotope compo-sition also depends from interaction of this componentwith rocks (the possible alternative explanation of theorigin of Selection 5 is considered below).

Share of Component A in Waters of Thermomineral Springs

After determining δDÄ and knowing the value of the”hydrogen isotope shift” (∆δD = δDtherm – δDsurf , where

–35 –30 –25 –20 –15 –10 –5 0

–250

–200

–150

–100

–50

δ18O, ‰

δD, ‰

Waters ofChukotka

1

2

3

4

5

Fig. 9. Isotopic composition of H2O in different reservoirsof Chukotka. (1) SMOW; (2) coastal waters of the BeringSea near Arakamchechen Island and in the Kivak Lagoon(Table 4); (3–5) compositions of subsurface ice, after(Vasil’chuk, 1992; Vasil’chuk and Kotlyakov, 2000):(3) based on measured δD and δ18O values, (4) based onδ18O measurements and δD calculations using the Craigline, (5) based on δD measurements and δ18O calculationsusing the Craig line. The hatched rectangle comprises datapoints obtained for thermomineral springs of easternChukotka and local surface waters.

446


POLYAK et al.

(therm) and (surf) designate thermal and local surfacewaters), we can calculate the share of component A(ïÄ) in particular thermomineral water regardless ofthe interaction degree of this component with rocks inline with the following equation:

ïÄ = (δDtherm – δDsurf)/(δDÄ – δDsurf). (1)

Correspondingly, the share of surface waters ïsurf =(1 – ïÄ) is determined as

ïsurf = (δDtherm – δDÄ)/(δDsurf – δDÄ). (2)

Equation (2) shows that the deuterium excess inthermomineral waters (relative to component A) shouldreflect its dilution degree by near-surface waters withthe higher δD value: the closer the hydrogen isotopecomposition in thermal waters to that in the deep-sourced component A, the lower the dilution degree ofcomponent A.

In principle, local and infiltration meteogenicwaters, as well as thalassic varieties buried during sed-imentation or driven from the recent sea basin into thecontinental hydrothermal systems, can be characterizedby higher δD values as compared with thermomineralwaters. Such a phenomenon is observed in some coastalcirculation systems (Kononov and Tkachenko, 1974).Therefore, the assessment of ïÄ in the thermomineralsprings depends on the presumed nature of the dilutingcomponent and technique of δD determination in thesewaters.

The δDsurf value used in Eqs. (1) and (2) is an aver-aged parameter that characterizes the isotopic composi-tion of surface waters in the particular discharge local-ity of hydrothermal springs. As is known, this compo-sition is season-dependent. Therefore, the use ofrandom estimates of δD as its characteristics for the cal-culation of ïÄ (or ïsurf) introduces a certain error. Theerror could seemingly be reduced using the δD value insurface waters based on its above-mentioned correla-tion with the longitude. In this case, however, anothererror due to curvature of δDsurf isolines relative tomeridians (Fig. 6) is possible. For the hypotheticaladmixture of seawater, the δD value of –20‰ wasaccepted in accordance with our measurements in watersof the Kivak Lagoon and Senyavin Strait (Table 4).

In five examined thermomineral water localities(points 3, 5, 9, 14, and 15), δD values is higher (isoto-pically heavier) than in the local surface water, indicat-ing that mixing of the latter water with component Acould not form the isotopic composition of the thermo-mineral water. For these localities, calculated δDsurf val-ues based on the correlation with longitude (points 3and 5) rather than the values measured in springs wereused or seawater was conditionally accepted as a dilut-ing component. The last assumption seems possible forthe coastal Dezhnev springs (Point 9), less probable forthe Oranzhevye springs (Point 14), and improbable forthe Olen’i springs. Therefore, the ïÄ value for the lastsprings was not determined.

0

–50

–100

–150

–200

–250

–300

δD, ‰

2500020000150001000050000Cl, mg/l

14

1011

19

7

16

15

1712

682

13

3

5

4

Seawater

Fig. 10. Correlation between the hydrogen isotope composition in H2O and Cl ion concentration in thermal waters of easternChukotka. Numerals correspond to numbers of groups of springs in Fig. 1.



The calculation results are given in Table 6 (column 4).They show that all samples taken in a single locality ofhydrothermal spring discharge reflect almost the sameshare of component A. In contrast, its value ranges from0.07 to 0.88 and lacks regional specifics in different dis-charge localities.

Salt Composition of Component A

Mineralization of component A (åÄ) may be esti-mated on the basis of its calculated share (ïÄ) in thesprings examined and the following assumptions: (i)component A provides both H2O and dissolved salts;(ii) this component is diluted by local surface waters,which are practically barren of salts (Msurf ~ 0). The MAvalue was determined in 20 of 22 spring groups. Thisvalue was 9.5–14.7 g/l in 13 groups, <7 g/l (1.9 g/l insome places) in five groups, and 36.5–37.5 mg/l in twogroups located at the northern margin of the studyregion (Table 6, Fig. 11). Two last values were obtainedfor the Neshkan and Oranzhevye springs in the north-ernmost part of the peninsula (points 10 and 14; miner-alization 37.16 and 36.23 g/l, respectively).

For 15 groups of springs, where local surface waters(Msurf = 0) were believed to serve as a diluting agent,Mtherm = MA × XA and MA = Mtherm/XA. For other fivegroups of springs with mineralization exceeding 17 g/l,the Oranzhevye (Point 14), Neshkan (Point 10), andTeyukei (Point 11) springs in northernmostChukotka, as well as for the Dezhnev and Chaplinosprings (points 1 and 9, respectively) in the eastern-most and southeastern parts of the peninsula, seawaterswith δD values of –20‰ and MSW = 35‰ wereaccepted as a diluting agent. In these cases, Mtherm =åÄ × ïÄ + åSW × (1 – ïÄ) and MA = [Mtherm – MSW ×(1 – ïÄ)]/ïÄ (if real MSW values are lower, the MAvalue should be higher than the calculated one). In theTeyukei, Dezhnev, and Chaplino springs, the MA values

were 13.1, 10.1–12.2, and 11.0–11.4 g/l, respectively,i.e., similar to their estimates for most other springs ofthermomineral waters with local surface watersassumed as the diluting component. This provides animpression that mineralization of component A is uni-form throughout the entire Chukotka Peninsula andclose to 10–12 g/l. The formal average from MA esti-mates obtained for all 20 groups of springs (after theirpreliminary averaging for different samples of the samegroup) is 11.8 g/l.

In the case of the Oranzhevye springs (Point 14),assumption of dilution of component A by fresh surfacewaters leads to an absurd result: XA and MA valuesappear to be negative. Consequently, assumption ofdilution of the deep-sourced component by seawaterhas no alternative. In this case, we obtain MA = 36.5 g/l,which exceeds insignificantly mineralization of dis-charged thermal waters. Therefore, seawater is alsobelieved to represent a diluting agent in the Neshkansprings. Complete exclusion of possibility of the contri-bution of recent seawater to the formation of hydrother-mal solutions in (Cheshko et al., 2004) was too categor-ical, as is evident from the data presented in our paper.

Concentration of CaA in component A calculatedsimilarly as the MA value at the Ca content in seawaterequal to 413 mg/l does not change the mineralizationtype of the deep-sourced component relative to watersof springs, where the share of Ca is substantially higherthan in seawater (Table 6, columns 6 and 7). At thesame time, in the case of positive correlation betweenMA and CaA values, the latter values are highly variablewithin a narrow interval of the most widespread MAestimates available for Chukotka (Fig. 12). This factsuggests different metamorphism degrees of ground-waters in the study region.

MA estimates are substantially lower as comparedwith their average values in three groups of springs—the Senyavin springs located in the southeastern part of

102

101

100

åÄ, g/l

1‡db 5‡ 5d3‡

5c1c

2‡ 2b 23‡8b

6‡

6b

13‡12‡

11‡

14‡

10‡

16‡17‡

21‡ 22‡

20‡

18‡

Southeastern marginsCentral areas (Kolyuchinskaya– Northern

margin

7cbe‡9‡bc

Mechigmen zone)

Fig. 11. Mineralization of component A in various areas of Chukotka. Numerals of data points correspond to numbers in column 1of Table 1.

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Table 6. Parameters of the deep-sourced component A

Numberin Table 1 Group of springs Sample X(A) M(A), g/l CaA, g/l CaT, g/l T(A), °C

1 2 3 4 5 6 7 8

9a Dezhnev (m)1 90/02 0.65 11.4 2.651 1.723 1059c 92/02 0.66 11.0 2.441 1.611 809b 91/02 0.64 11.3 2.630 1.683 93

average 0.650 11.23 931a Chaplino (m)1 21/02 0.69 12.2 3.630 2.505 1271d 24/02 0.68 11.6 3.610 2.455 1151b 22/02 0.69 11.8 3.514 2.425 981c 23/02 0.68 10.1 3.610 2.455 99

average 0.685 11.42 1015a Kukun 50/02 0.39 13.5 0.823 0.321 1535c 51/02 0.36 11.1 0.722 0.260 1415d 1a/04 0.36 13.0 1585f 1/04 0.37 0.300 151

average 0.37 12.53 150.74a Kivak 40/02 0.07 0.7212a Senyavin 30/02 0.78 1.9 0.118 0.092 1002b 31/02 0.77 2.0 0.115 0.088 103

average 0.775 1.95 101.53a Arakamchechen 34/02 0.13 11.4 0.555 0.072 28020a Getlyangen An-22(7i)/05 0.43 10.3 1.074 0.4622 9819a Sineveem An-26(9i)/05 0.20 3.350 0.6702 21318a Verkhne-Nunyamoveem An-27(8i)/05 0.43 4.0 0.647 0.2782 8310a Neshkan (m)1 3/04 0.85 37.5 4.000 3.400 6114a Oranzhevye (m)1 8/04 0.84 36.5 6.369 5.350 1611a Teyukei (m)1 4/04 0.79 13.1 2.152 1.700 713a Vytkhytyaveem 7/04 0.23 14.7 1.200 0.276 27412a Kub 6/04 0.36 12.5 0.667 0.240 1817b

Nel’pygenveemAn-13(1i)/05 0.50 2

17a 14/04 0.49 14.1 0.735 0.360 1321a Stupenchatye An-21(5i)/05 0.77 9.5 1.870 1.4402 323a Pechingtanvaam An-6i/05 0.66 3.2 0.255 0.1682

22a Ioni An-20(4i)/05 0.66 11.0 2.182 1.4402 716a Arenyshkynvaam 12/04 0.59 14.1 1.000 0.590 2016b An-18(3i)/05 0.88 7

average 0.735 13.57d Babushkiny Ochki 2a/04 0.71 257c 71/02 0.75 12.2 1.272 0.954 187b 2/04 0.76 12.6 1.263 0.960 277e 72/02 0.83 11.2 1.123 0.932 177a 70/02 0.85 10.9 1.094 0.930 23

average 0.780 11.7 228b Tumannye 81/02 0.76 4.5 0.142 0.108 728a 80/02 0.76 77

average 0.760 74.56b Mechigmen 62/02 0.58 7.1 0.186 0.108 1106a 60/02 0.72 5.4 0.184 0.104 124

average 0.650 117Notes: 1 Seawater was a presumable diluting agent.

2 After (Kievskii et al., 2006).



104

103

102

102101100

åÄ, g/l

CaÄ, mg/l

1‡bd1c

9‡bc 11‡

22‡21‡7b

13‡

16‡

17‡12‡

3‡

5‚

5‡d20‡

7‡

14‡

10‡

18‡

23‡

6b

6‡2‡8b

y = 138x – 67R2 = 0.44 n = 27

Fig. 12. Concentration of Ca ion and total mineralization of the deep-sourced component A in hydrothermal springs of Chukotka.Numerals of data points correspond to numbers in column 1 of Table 1.

the peninsula (Point 2) and closely spaced Mechigmenand Tumannye springs in the Kolyuchinskaya–Mechig-men Depression (points 6 and 8, respectively). TheSenyavin hydrothermal springs, where the MA value isminimal (<2 g/l), are completely isolated from the sea,although they discharge only ~1 km away from theshoreline and are characterized by the most deuterium-deficient (–24‰) waters among all springs of Chukotkarelative to local fresh surface waters. At the same time,they are neighbors of the Chaplino and Arakamchechensprings (points 1 and 3), where MA is estimated at~11 g/l, which represents a background value for theChukotka Peninsula. The nature of these Senyavin min-imums and their spead remain unclear. Coincidence ofanomalous values for different parameters of the Sen-yavin springs seems hardly incidental: the formation ofthese fresh, depleted in D and 18O, and hot (79°C)waters may be related to disturbance of the subsurfacehydrosphere by the deep thermal source.

Temperature of Component A

Based on XA estimates, we also determined the tem-perature of component A. Such an approach is ratherconditional, because assessment of TA in a particularspring should take into account not only proportions ofthe mixed deep-sourced and cold surface waters, butalso cooling degree of the deep-sourced water duringits ascent.

In Fig. 13, data points of Chukotka thermomineralsprings form two (upper and lower) fields. The upperfield includes thermal springs located at the southeast-ern margin of the peninsula (Fig. 1, Table 1, points 1–5,9, and 18–20), the Neshkan and Vytkhytyaveemsprings at the northern margin (points 10 and 13,respectively), and the Mechigmen and Tumannyesprings of the Kolyuchinskaya–Mechigmen zone(points 6 and 8, respectively). Such a distribution ofdata points implies similarity of conditions that deter-mine the temperature of these hydrothermal solutions.They demonstrate quite natural positive correlationbetween the temperature of discharged waters (T°C)and the share of component A (XA): T(°C) = 56.55XA +31.216 (n = 16; R > 0.8 > Rcrit = 0.497).

This dependence reflects the geothermal specifics ofdifferent thermal springs, although does not allow exactassessment temperatures of the deep-sourced compo-nent and diluting agent. For example, the above regres-sion equation implies that the temperature of the dilut-ing agent (at ïÄ = 0) is close to 30°C. This value is sub-stantially higher than the temperature of atmosphericprecipitation infiltrating in rocks and is approximatelyequal to probable temperatures at a depth of 1.0–1.5 kmunder conditions of the background conductive heatflow (Geotermicheskaya…, 1972; Teplovoi rezhim…,1970). According to this trend, the temperature of thedeep-sourced component A (at ïÄ = 100%) in hydro-thermal springs of southeastern Chukotka should be

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POLYAK et al.

<90°C, which is lower than the real values recorded indischarge areas of the hottest springs, such as theMechigmen spring (97°C in one of the jets) and Chap-lino (92°C in Borehole 23, according to (Suvorova,1972)) springs, where ïÄ ~ 60–70%. Temperature esti-mates obtained for separate samples seem more reli-able. In six groups of thermomineral springs in south-eastern Chukotka, the estimates vary from 83 to 150°C(average 106°C). In two other groups (Sineveem andArakamchechen springs; points 19 and 3, respectively),the temperature of component A ranges from 213 to280°C. Such values seem overestimated and requireconfirmation by other methods.

The lower field comprises data points obtained forthe remaining thermomineral springs of the Kolyuchin-skaya–Mechigmen zone (points 7, 16, 17, 21, and 22)and three springs located in the northernmost part of thepeninsula (points 11, 12, and 14). Such distribution pat-tern implies similar (but different from those inherent tothe southeastern areas of the peninsula) formation con-ditions of springs. These springs are characterized bysubstantially lower discharge temperatures (<22°C).Visual correlation between the temperature of thermalwaters and the share of the deep-sourced component inthem is illusory, since R < Rcrit. At the same time, dataobtained for this selection apparently indicate that tem-perature of the diluting component (with XA = 0) wasclose to 0°C and temperature of component A was low(<30°C). In fact, this temperature most likely reflects acooling effect of the ascending flow of component A

prior to its mixing with the diluting near-surface waters.Such a specific feature of thermal waters in the lowerfield is not quite clear. This may be related to a thickercryolithozone in central areas of eastern Chukotka thanin its coastal areas. The temperature specifics of thesehydrothermal springs correlates with their minimal δDvalues (Fig. 8) and, correspondingly, maximal values ofthe hydrogen isotope shift ∆δD and share of the deep-sourced component XA (up to 88%). Therefore, we canpropose an alternative explanation of the trend in Selec-tion 8 (Table 5): this flat trend δD = 4.7684 δ18O –50.2403 likely reflects the mixing of component A withthe melting H2O delivered from the relatively deute-rium- and 18O-rich subsurface ice rather than (and, pos-sibly, not only) the “oxygen isotope shift.”

All the aforesaid allows the following assumption:the deep-sourced component A represents a subperma-frost meteogenic well-homogenized infiltration waterthat percolated in the interstitial–fissure space of rocksfor a substantially long time and acquired a notablemineralization (10–12 g/l, on average). Its isotopicparameters are probably related to the fact that themeteogenic feeding is dominated by snow waters ratherthan the summer (relatively enriched in deuterium and18O) atmospheric precipitation. In terms of its positionin the hydrodynamic zoning of the geological section,component A corresponds most likely to the zone ofrelatively slow water exchange.

At the same time, we cannot say that issue of the for-mation of hydrothermal springs in the Chukotka Penin-

100

90

80

70

60

50

40

30

20

10

0 1.00.80.40.2XA

22

I

II

21 11

14

16

16

17

1712

3

4 19

18

20

5

513

6

98

8

2

2

6

1

10

7

tsurf, °C

1234

0.6

Fig. 13. Correlation between the temperature of discharged waters and the share of component A in them in various areas ofChukotka. (1–4) Data points of thermomineral springs in various areas of Chukotka (Fig. 1): (1) southeastern margin, (2) centralareas, (3) Mechigmen and Tumannye springs, (4) northern margin. Ovals corresponds to fields of data points obtained for (I) centralareas of Chukotka and (II) its southeastern margin. The straight line in oval I is a regression line for hydrothermal springs of south-eastern Chukotka δD = 56.55δ18O + 31.22 (R2 = 0.65, n = 18).



sula has been solved. Due to deficiency of boreholeobservations and, consequently, hydrogeological andcryological characteristics of the section, their specificsin different structural–tectonic settings of the peninsularemain unclear. Data on the distribution of cryopegsand their isotopic compositions are also missing.Therefore, it is rather difficult to judge about the role ofcryopegs in the formation of thermomineral waters.Mechanism of the heat feeding of hydrothermal sys-tems is also unclear. This aspect is particularly impor-tant in the context of probable use of the thermal energypotential of hydrothermal springs, a pressing issue forChukotka. Finally, analysis of data on the total and iso-topic compositions of the gaseous phase in thermomin-eral fluids, as well as correlation of these data with thechemical composition and temperature of dischargedwaters, wait special consideration.

CONCLUSIONS

Average annual temperature in the eastern ChukotkaPeninsula with the universally developed cryolithozoneis negative. Therefore, all springs discharging the yearround in this region should be considered thermalsprings. We studied thermomineral waters from23 groups of such springs with the total mineralizationranging from 1.47 to 37.14 g/l and the discharge tem-perature ranging from 2 to 97°C. The results obtainedwere compared with the nearby surface freshwaters.

In surface waters, δD varies from –121.4 to−89.5‰; δ18O, from –16.4 to –11.1‰. These values areconsistent with variations in the isotopic compositionof atmospheric precipitation at similar latitudes ofAlaska. The δD and δ18O values obtained for the sur-face waters decrease from the east to west, i.e., towardinterior areas of the land.

In thermomineral waters, δD ranges from –134.2 to–92.5‰; δ18O from –17.6 to –10.5‰. Approximatelyin one-half of sampling localities, such waters aredepleted in deuterium as compared with surface H2O,indicating a contribution of the isotopically light com-ponent to their formation. Based on analysis of trendsof data points obtained for the surface and thermomin-eral waters in the δD–δ18O plot, we reconstructed theisotopic composition of the deep-sourced component A(δD = ≈ –138‰ and δ18é = ≈ –19‰) and estimated itsshare (ïÄ) in particular samples. Lateral distribution ofδD in thermomineral waters shows that hydrothermalsolutions with the minimal deuterium content (δD <−120‰) are confined to the Kolyuchinskaya–Mechig-men Depression that represents a zone of neotectonicactivity. In addition, they differ from thermomineralwaters discharging beyond the depression by relativelyhigher 18é concentrations and other isotopic–geochem-ical properties (the gaseous phase composition, as well

as δ , 3çÂ/4çÂ, and δ15N values).C13CO2

Based on the ïÄ values in particular thermomineralsprings, we estimated the total mineralization of thiscomponent (åÄ) with assumptions of different dilutingagents. The åÄ value ranges from 9.5 to 14.7 g/l (aver-age ~12 g/l) in most springs studied over the entireChukotka Peninsula. In five most mineralized coastalsprings, seawater likely represents such a diluting com-ponent. In three of these five cases, estimates of åÄwere also close to its regional average value. In twoother groups of springs with mineralization of 37.16and 36.23 g/l, seawater subjected to metamorphism(consequently, depletion in Mg and sulfates) and someconcentration of most likely cryogenic nature serves asboth the diluting agent and deep-sourced component A.

Temperature estimates obtained for component Aare more conditional, because such estimates dependon the dilution degree of deep solutions by cold surfacewater and the cooling rate of ascending deep waters.Nevertheless, they indicate substantial regional differ-ences in the thermal regime of springs.

Judging from isotopic characteristics and total min-eralization, the deep-sourced component A represents asubpermafrost well-homogenized meteogenic infiltra-tion H2O that percolated within the interstitial–fissurespace of rocks for a relatively long time and acquired anotable mineralization. With respect to its position inthe vertical hydrodynamic zoning of the geological sec-tion, component A likely corresponds to the zone witha relatively slow water exchange.

ACKNOWLEDGMENTS

We are grateful to A.D. Kievskii and O.V. Ladnyifrom the Georegion Federal State Unitary Enterprise(Anadyr) for some samples kindly placed at our dis-posal; to E.V. Danilyuk (head of the Provideniyaadministrative area) and M.A. Zelenskii (head of theChukotka administrative area) for help during fieldworks; and V.I. Vinogradov, B.G. Pokrovskii,Yu.A. Taran, and G.Yu. Butuzova for reading themanuscript and valuable comments.

This work was supported by the Russian Foundationfor Basic Research (project nos. 03-05-64869-a, 04-05-79087-k, and 06-05-64647-a) and the Division of EarthSciences of the Russian Academy of Sciences (Pro-gram no. 8). Field works in 2002 were supported in partby the Administration of the Chukchi Autonomous Dis-trict.

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Isotopic Composition of Thermal Waters in Chukotkageotherm.ginras.ru/Pdf/_Pol et al 2008 244_LMReng.pdfISSN 0024-4902, Lithology and Mineral Resources, 2008, Vol. 43, No. 5, pp. 429–453