421
HYDROTHERMAL KARSTIFICATION IN VADOSE CAVES (WESTERN CARPATHIANS)
GEOLOGICA CARPATHICA, 55, 5, BRATISLAVA, OCTOBER 2004
421429
FLUID INCLUSION AND STABLE ISOTOPIC EVIDENCE FOR EARLY
HYDROTHERMAL KARSTIFICATION IN VADOSE CAVES OF THE
NÍZKE TATRY MOUNTAINS (WESTERN CARPATHIANS)
MONIKA ORVOOVÁ
1
, VRATISLAV HURAI
2
, KLAUS SIMON
3
and VIERA WIEGEROVÁ
4
1
Slovak Museum of Nature Protection and Speleology, kolská 4, 031 01 Liptovský Mikulá, Slovak Republic; orvosova@smopaj.sk
2
Department of Mineralogy and Petrology, Faculty of Natural Sciences, Comenius University, 842 15 Bratislava, Slovak Republic
3
Geochemistry Institute, Georg-August University, 37077 Göttingen, Germany
4
Geological Survey of Slovak Republic, Mlynská dolina 1, 841 07 Bratislava, Slovak Republic
(Manuscript received January 8, 2003; accepted in revised form December 16, 2003)
Abstract: Hydrothermal paleokarst cavities with calcite crystals up to 20 cm in diameter were found in two caves of the
Nízke Tatry Mountains developed in Triassic limestone and dolomite of the Guttenstein type. In both caves, older zones
of tectonic and hydrothermal activity have been overprinted by vadose speleogenesis. According to fluid inclusion
microthermometry data, prismatic-scalenohedral calcite from the Silvoova Diera Cave has precipitated at temperatures
between ~60 and 101 °C from low salinity aqueous solutions (≤0.7 wt. % NaCl eq.). Carbon and oxygen isotope profil-
ing revealed significant δ
13
C decrease accompanied by slight δ
18
O increase during growth of calcite crystals. The nega-
tively correlated carbon and oxygen isotope data cannot be interpreted in terms of any geologically reasonable models
based on equilibrium isotopic fractionation. Fluid inclusion water exhibits minor decrease of δD values from crystal core
(31 SMOW) to rim (41 SMOW). Scalenohedral calcite from the Nová Staniovská Cave has precipitated at
slightly higher temperatures (63107 °C) from aqueous solutions with salinity ≤2.7 % NaCl eq. The positively corre-
lated trend of δ
13
C and δ
18
O
values is similar to common hydrothermal carbonates. The fluid inclusion water δD values
differ significantly between the crystal core (50 SMOW) and rim (11 SMOW). The calcite crystals are inter-
preted as representing a product of an extinct hydrothermal system, which was gradually replaced by shallow circulation
of meteoric water. Fossil hydrothermal fluids discharged along Alpine uplift-related NNWSSE-trending faults in
Paleogenepre-Pliocene times. Increased deuterium concentration in the inclusion water compared to recent meteoric
precipitation indicates a warmer climate during the calcite crystallization.
Key words: stable isotopes, fluid inclusions, hydrothermal karst, hydrothermal calcite.
Introduction
Products of hydrothermal karstification superimposed by
younger meteoric speleogenesis have been described in many
karst regions. Dublyanski & Lomaev (1980) found calcite
veins and hydrothermal cavities lined by Iceland spar in at
least two caves of the Mountainous Crimea, Ukraine (Khod
Konem and Gvozdeckogo Caves). Cryptokarstic hydrother-
mal cavities modified by later vadose caves were described by
Sgibnev (1986) from the Tchien Shan Mountains (Kazakh-
stan), by Bosák (1993) from the Tyuya-Muyun Ridge
(Kyrghyzstan), and by Bac-Moszaszwili & Rudnicki (1991)
from the Polish Tatra Mountains (Dziura Cave). Osborne
(1999, 2000) and Osborne & Cooper (2001) studied sulphide-
bearing hydrothermal paleokarsts invaded by meteoric speleo-
genesis from the Jenolan Caves (New South Wales) and Ida
Bay (Tasmania). The most detailed study of Ford (2000) fol-
lowing his previous paper (Ford 1995) and completed later by
Cordingley (2000), demonstrated a number of cases of the hy-
drothermal karst overprinted by younger vadose speleogenesis
in the Castleton area (Derbyshire, UK). Typical hydrothermal
karst also occurs in the Transdanubian and North Hungarian
Ranges, where three settings have been defined according to
fluid inclusion and stable isotope data (Dublyansky 1995,
1997; Dublyansky & Ford 1997). All authors emphasized the
important role of the earlier hydrothermal paleokarst as a
guide for infiltration of water incidental to the younger mete-
oric speleogenesis (Osborne 2000).
Hydrothermal karstification has not been described in the
Western Carpathians until now. Recently, large calcite crys-
tals have been reported from two caves located in northern
slopes of the Nízke Tatry Mountains (Hochmuth & Holúbek
1996; Votoupal & Holúbek 1996; Orvoová 1999). The caves
are developed in Triassic limestones and dolomites of the
Guttenstein type belonging to the carbonate sequence of Choè
Nappe thrusted over the crystalline basement and autochtho-
nous Permian-Triassic cover of the Tatric Tectonic Unit
(Fig. 1). Fluid inclusion and stable isotope studies were car-
ried out with the aim of elucidating the origin of the calcite.
Detailed measurements of carbon and oxygen isotope ratios
across crystal growth zones, hydrogen isotope analyses of in-
clusion water, and microthermometry data from fluid inclu-
sions were the principal analytical methods.
Sample location
The Silvoova Diera Cave situated at about 1500 meters
above see level in the SE part of the Ohnite karst massif
422
ORVOOVÁ, HURAI, SIMON and WIEGEROVÁ
(Fig. 1) is a fluvial cave with narrow corridors and small
rooms. The cave represents a fragment of a fossil cave net-
work developed in a ponor area along the contact of Variscan
granitoids with karst rocks. Calcite crystals form linings of
hydrothermally corroded nests in a NNWSEE-trending tec-
tonically disintegrated zone. Detached crystals were found to-
gether with rock debris in allochthonous clastic fill of a sump.
Smaller colourless, translucent crystals, up to 1 cm in size,
display a rhombohedral habit, while larger ones have typical
prismatic-scalenohedral shapes created by combination of
dominant hexagonal prism (1010) and a flat scalenohedron.
The maximum length of the doubly terminated and partly
translucent ochre-coloured crystals is 10 cm (Fig. 2). The
prismatic facets of larger specimens exhibit etching figures.
The interior of the crystals is oscillatory zoned.
Fig. 1. Geological cross-section of the study area (modified after Mahe¾ 1986). 1 Quaternary; 25 Choè Nappe: 2 Lunz Beds
(Karnian), 3 Reiflin Limestone (Upper AnisianLadinian), 4 dolomite (MiddleUpper Triassic), 5 Guttenstein Limestone (Ani-
sian); 68 Krína Nappe: 6 marly limestone (TitonianLower Cretaceous), 7 dolomite (Middle to Upper Triassic), 8 quartzite
(Lower Triassic); 9 fault.
The Nová Staniovská Cave is located at about 700 m above
see level at the junction of the Jánska and Staniovská Valleys,
delineating the Ohnite karst massif from north and west. The
cave has developed on two horizontal levels, following a
rhomboidal net of NS (NNWSSE)- and WNWESE-trend-
ing faults. Calcite crystals partly or completely fill small disso-
lution cavities, up to several decimeters in diameter (Fig. 3),
following the NNWSSE-trending fissures in the southern-
most part of the system. Vadose speleothems have not been en-
countered in this part of the cave.
The calcite crystals are partly translucent, grey or yellow,
1020 cm in size, and exhibit scalenohedral habit with domi-
nant first-order (2131) scalenohedron (Fig. 3). Larger crystals
often display skeletal growth and etching figures. All the crys-
tals consist of transparent core and rhythmically banded rim,
423
HYDROTHERMAL KARSTIFICATION IN VADOSE CAVES (WESTERN CARPATHIANS)
Fig. 2. Individual crystals and druses of prismatic-scalenohedral cal-
cite recovered from sediments of the Silvoova Diera Cave.
12 cm thick, composed of recurrent dark-grey and transpar-
ent stripes. The grey colour of dark stripes results from a high
density of small (several µm in diameter) clayey particles.
Both caves represent products of phreatic/vadose speleo-
genesis by cold water of deeply circulating meteoric waters.
Typical speleothems (dripstones, flowstones, crusts, stalac-
tites, stalagmites etc.) are connected with later vadose evolu-
tion of the caves. No other minerals are associated with the
drusy calcite, belonging to the early hydrothermal stage of the
cave development.
Analytical methods
Calcite crystals were cut perpendicular to the c-axis to ob-
tain an elongated strip, 1 cm thick, 2 cm wide, with length cor-
responding to crystal diameter. The strip was further split into
1011 consecutively numbered aliquots, each about 2
Fig. 3. Nest of giant scalenohedral calcite crystals lining dissolution
vug in the Nová Staniovská Cave.
2.5 cm
3
in volume, representing individual growth zones of
the crystal.
About 10 mg from each aliquot was taken for determination
of carbon and oxygen isotopes. Common closed-reaction-ves-
sel method of McCrea (1950) was used to convert the carbon-
ate to CO
2
. Carbon and oxygen isotope ratios of CO
2
were
measured using a Finnigan MAT 250 mass spectrometer at the
Geological Survey, Bratislava. The results are given in con-
ventional δ-notation as deviation from the V-PDB and
V-SMOW standards. Uncertainty for both the δ
13
C and δ
18
O
values is ±0.1 .
Remaining part of each aliquot was gently split into thin
cleavage fragments and carefully inspected under polarizing
microscope. Cleavage fragments containing fluid inclusions
were selected for microthermometry and hydrogen isotope
analysis of inclusion water.
Inclusion water was extracted from ~2 g of desiccated cal-
cite fragments by vacuum milling at 60 °C (Simon 2001). The
liberated water was converted to hydrogen by reduction with
uranium at 750 °C. The hydrogen was adsorbed onto activated
charcoal in a liquid nitrogen-cooled glass container and imme-
diately analysed by mass spectrometry. The inclusion water
extraction and hydrogen isotope measurements were carried
out at the Institute of Geochemistry, Göttingen, using a Finni-
gan MAT 251 mass spectrometer. The δD values are ex-
pressed relative to the V-SMOW standard. The uncertainty
limit is within ±1 .
Cleavage fragments were used for microthermometry in
order to avoid thermal and/or mechanical re-equilibration of
fluid inclusions during sawing and polishing. Homogeniza-
tion temperatures were measured first to eliminate errors due
to expansion of ice and concomitant inclusion stretching on
cooling. Only one heatingfreezing cycle was applied to
each cleavage fragment. The heating-freezing stage used was
a Linkam THM-600 at the Geological Survey of the Slovak
Republic, Bratislava, mounted on a Nikon Optiphot micro-
scope with long-working distance objectives and a JVC
CCD camera. The stage was calibrated using redistilled wa-
ter, pure chemical substances and synthetic fluid inclusions.
The uncertainty of the temperatures of phase transitions is
about ±0.1 °C.
Fluid inclusions
Fluid inclusions are abundant in both calcite types. They
can be classified as primary (Fig. 4a,b,d,e) and pseudosecond-
ary (Fig. 4c,f) sensu Roedder (1984). True secondary inclu-
sions with compositions and densities significantly differing
from those in primary and pseudosecondary inclusions, or
cross-cutting outer surface of calcite crystals, were not detected.
Extraordinarily large primary inclusions, with diameters up
to 1000 µm, are typical of scalenohedral calcite from the Nová
Staniovská Cave (Fig. 4e). The inclusions are strongly elon-
gated and often exhibit a saw-tooth shape. Other large inclu-
sions have strongly irregular walls, but the smaller ones be-
come equant, acquiring a normal negative-crystal shape of
host crystal (Fig. 4a,b). Pseudosecondary inclusions are
grouped into planes along healed fractures, which cross-cut
424
ORVOOVÁ, HURAI, SIMON and WIEGEROVÁ
Fig. 4. Aqueous fluid inclusions trapped in prismatic-scalenohedral calcite (the Silvoova Diera Cave: ac) and scalenohedral calcite (the
Nová Staniovská Cave: df). a Group of primary, negative crystal-shaped inclusions. Two-phase inclusion consisting of vapour bubble
and aqueous liquid is indicated by open arrow, while the remaining inclusions marked by solid arrows are filled only with aqueous liquid;
b Extremely large primary, negative crystal-shaped, two-phase inclusion; c Group of fracture-bound, pseudosecondary inclusions,
consisting of monophase (liquid, marked by solid arrows) and two phase (liquid+vapour, marked by open arrows) inclusions; d Primary,
two-phase aqueous inclusion (marked by open arrow) trapped in rhythmically banded rim of the crystal along dark growth zone with dense
concentration of clay particles (upper left part of the photomicrograph); e Primary, two-phase inclusion from the transparent core of the
crystal; f Group of pseudosecondary, two-phase inclusions with consistent liquid-to-vapour ratios. The absence of monophase aqueous
inclusions is indicative of higher crystallization temperatures of the scalenohedral calcite compared to the prismatic-scalenohedral type.
Scale bars in all photomicrographs represent 50 µm.
several growth zones, but terminate within the crystal interior
(Fig. 4c,f).
Mono- and two-phase inclusions, both dominated by aque-
ous liquid, have been distinguished according to phase com-
position at room temperature. Two-phase inclusions contain
small (15 vol. %) vapour bubbles (Fig. 4b,d,e,f). Monophase
aqueous inclusions accompanying two-phase aqueous inclu-
sions occur only in prismatic-scalenohedral calcite from the
Silvoova Diera Cave (Fig. 4a,c). Consistent volumetric phase
ratios in neighbouring inclusions in scalenohedral calcite from
425
HYDROTHERMAL KARSTIFICATION IN VADOSE CAVES (WESTERN CARPATHIANS)
Discussion
Crystallization PT conditions
Consistent volumetric phase ratios and absence of vapour-
dominated inclusions in both calcite types indicate a homoge-
neous trapping in a high-temperature phreatic zone (Goldstein
& Reynolds 1994). The homogenization temperatures thus
represent the minimum possible trapping temperature. The T
h
values in scalenohedral calcite (63.1107.1 °C) are somewhat
higher than those in the prismatic-scalenohedral type (58.6
100.5 °C). Primary monophase aqueous inclusions, not result-
ing from necking-down process (e.g. Fig. 4a), indicate an epi-
sodic decrease in crystallization temperature of the
prismatic-scalenohedral calcite below ~50 °C, corresponding
to a low-temperature phreatic zone. However, absence of air-
filled bubbles rules out crystallization in the vadose zone
(Goldstein & Reynolds 1994).
The observed homogenization temperatures above 100 °C,
slightly exceeding freshwater boiling point at atmospheric
pressure, enable calculation of minimum trapping pressure.
Considering PT conditions close to the liquidvapour phase
boundary for pure H
2
O (e.g. Haas 1976), the T
h
value of
the Nová Staniovská Cave are indicative of entrapment of a
homogeneous fluid (Fig. 4f). Boiling-related, vapour-domi-
nated inclusions have not been recognized. Air bubbles indi-
cating a low-temperature vadose environment (e.g. Goldstein
& Reynolds 1994) are also absent.
Homogenization temperatures (T
h
) of two-phase inclusions
in prismatic-scalenohedral calcite from the Silvoova Diera
Cave are clustered mostly between 75 and 85 °C, with the to-
tal range between 58.6 and 100.5 °C. No significant changes
in T
h
values were recorded in various growth zones (Fig. 5).
Temperatures of ice melting (0 to 0.4 °C) correspond to sa-
linities between zero and 0.7 wt. % NaCl eq. (Bodnar 1993),
with the majority of the determinations approaching the fresh-
water salinity. Eutectic temperatures could not be determined
due to very low salt content and the small volume of the eu-
tectic solution remaining after ice freezing.
The microthermometry data for scalenohedral calcite of the
Nová Staniovská Cave are slightly different (Fig. 6). Al-
though the total range of the T
h
values is similar (63.1
107.1 °C), significant differences exist between the crystal
core and its rim. Most determinations from the core are
grouped between 96 and 108 °C. Lower T
h
values (8094 °C)
pertain either to pseudosecondary inclusions in the core or to
primary inclusions in rhythmically banded rim. Temperatures
of ice melting varied between 0 and 1.6 °C, thus correspond-
ing to salinities between zero and 2.7 wt. % NaCl eq. No
correlation between salinities and T
h
values has been ob-
served. Eutectic temperatures fall consistently between 21
and 22 °C, thus indicating either binary H
2
ONaCl mixture,
or its combination with Na
2
CO
3
and/or NaHCO
3
salts
(Borisenko 1977).
Stable isotopes
The carbon and oxygen isotope ratios in both calcite types
are remarkably different (Table 1). Prismatic-scalenohedral
type shows lower δ
18
O (9.812.6 ) and δ
13
C (3.2 to
11.7 ) values compared to the scalenohedral type (δ
18
O =
11.117.8 , δ
13
C = 3.3 to 6.8 ). The δ
18
O and δ
13
C val-
ues of prismatic-scalenohedral type are negatively correlated,
showing distinct changes along crystal growth direction
(Fig. 5), where the large depletion in
13
C (∆ = 8 ) is ac-
companied by moderate enrichment in
18
O (∆ = +3 ). In
contrast, except for the thin rims, a substantial portion of
scalenohedral calcites is almost homogeneous in terms of iso-
topic composition, showing only weak concomitant increase
in the δ
18
O (∆ = +0.4 ) and the δ
13
C (∆ = +1 ) values
(Fig. 6). The rhythmically banded rim is characterized by
strongly fluctuating and non-proportional changes in the δ
18
O
and δ
13
C values indicative of a non-equilibrium precipitation.
The δD values of inclusion water differ in both caves. A de-
crease in δD values from 31 in core to 45 in the rim
has been recorded in prismatic-scalenohedral calcite from the
Silvoova Diera Cave. Inclusion water from homogeneous
core of scalenohedral calcite from Nová Staniovská Cave is
somewhat lighter (50 ), but rhythmically banded rim con-
tains inclusion water with extraordinarily high δD value
(11 ).
Table 1: Isotope composition of calcite crystals (Nos. 1658, 1659,
HO-1) from the Silvoova Diera, and a calcite crystal (No. 1819)
from the Nová Staniovská Caves.
Sample No. Zone No.
@
18
O
V-SMOW
@
13
C
V-PDB
@
18
O
V-PDB
1658
11 rim
12.6
10.3
17.7
12
12.5
11.0
17.8
13
12.3
10.2
18.0
14
12.1
8.8
18.2
15
11.0
5.5
19.3
16 core
10.3
3.2
20.0
17
10.7
4.6
19.6
18
10.7
5.4
19.6
19
12.1
10.3
18.2
20 rim
12.4
10.0
17.9
1659
11 rim
12.2
11.7
18.1
12
12.1
11.0
18.2
13
12.1
10.3
18.2
14
11.5
8.1
18.8
15
10.2
5.3
20.0
16 core
9.8
3.8
20.4
17
9.8
3.6
20.4
18
10.3
4.8
20.0
19
11.5
7.1
18.8
20
12.4
9.9
17.9
21 rim
12.2
10.3
18.1
HO-1
core
11.2
4.0
19.1
rim
12.5
10.6
17.8
1819
11 core
18.1
3.3
12.4
12
17.9
3.5
12.6
13
17.7
3.6
12.8
14
17.7
3.8
12.8
15
17.6
4.0
12.9
16
17.8
3.9
12.6
17
17.7
4.3
12.8
18
13.2
6.8
17.1
19
11.1
3.7
19.2
20 rim
16.8
5.2
13.7
426
ORVOOVÁ, HURAI, SIMON and WIEGEROVÁ
107.1 °C corresponds to a trapping pressure of 0.13 MPa. As-
suming a hydrostatic regime with a fluid density of 967 kg.m
3
(average density of H
2
O-liquid at 63.1107.1 °C), the corre-
sponding water column must have been higher than 3.2 m to
prevent boiling at the bottom of the column. Calculation with
2.7 % NaClH
2
O solution (maximum salinity determined in
the scalenohedral calcite) does not substantially modify the
estimated minimum height of the water column, because de-
creased saturation vapour pressure is counterbalanced by in-
creased fluid density.
Isotopic composition of hydrothermal fluids
Prismatic-scalenohedral calcite
The δD values of inclusion water provide direct information
on the isotope composition of the calcite-forming fluids,
whilst the carbon and oxygen isotope ratios in the calcite must
be recalculated using an appropriate model to obtain isotopic
composition of the parental fluid.
An inverse correlation between the δ
18
O and δ
13
C values
(Fig. 5), with large depletion in
13
C (~8 ) accompanied by
a moderate enrichment in
18
O (~+3 ) from core to rim is
unique. A qualitatively similar isotopic trend has been hither-
to recorded only in hydrothermal carbonate veins genetically
linked with lamprophyres, where the isotopic trend resulted
from extreme CO
2
devolatilization (Demény et al. 1994).
DeVivo et al. (1987) have described a qualitatively similar
trend in hydrothermal karst from western Sardinia, where
scalenohedral calcite accompanied by quartz and barite in
Cambrian carbonates shows an increase in δ
18
O values from
13.816.3 in the core to 20.322.2 in the rim accom-
panied by δ
13
C decrease from 0.1 in the core to 5.1 in
the rim.
A negatively correlated CO fractionation has recently been
attributed to advanced CO
2
degassing of boiling aqueous so-
lutions combined with progressive cooling (Zheng 1990; De-
mény et al. 1994). A simple cooling by ~70° proposed by
DeVivo et al. (1987) for Sardinian calcites cannot be accepted
in light of fractionation models applied to hydrothermal car-
bonates (Zheng 1990; Zheng & Hoefs 1993a), because the
temperature decrease cannot lead to calcite precipitation due
to increasing solubility of the carbonates in the aqueous solu-
tions (Segnit et al. 1962). To precipitate the carbonate, the
temperature decrease of the aqueous fluid must be accompa-
nied by pH increase due to CO
2
outgassing and concomitant
breakdown of HCO
3
to H
+
and CO
3
(Rimstidt 1997).
The extensive CO
2
-devolatilization cannot be accepted as a
viable precipitation mechanism of hydrothermal calcites stud-
ied, because of negligible CO
2
concentrations potentially dis-
soluble at low temperature and pressure in the aqueous fluid.
Furthermore, HCO
3
should be the dominant dissolved carbon-
ic species at temperatures around 100 °C and pH values corre-
sponding to the stability of calcite. At this temperature, the
carbon isotope composition of fluid does not change substan-
tially, because the effect of CO
2
degassing is counterbalanced
by carbonate precipitation owing to proportional fractionation
factors (Ohmoto & Rye 1979). During CO
2
degassing at tem-
peratures below 100 °C, the residual HCO
3
rich fluid tends to
be enriched in
13
C, which is inconsistent with the observed
large depletion in the
13
C during growth of the prismatic-
scalenohedral calcite.
A mixing of two fluids might represent an alternative mod-
el, which could account for the unusual δ
13
Cδ
18
O data array
in the prismatic-scalenohedral calcite. The model illustrated in
Fig. 7 assumes mixing of hot (120 °C) H
2
OH
2
CO
3
fluid A
with cool (20 °C) fluid B with H
2
OHCO
3
composition. The
fluid A may represent a deeply circulating meteoric water dis-
solving CO
2
obtained by acid leaching of fresh limestone
(δ
13
C
lim.
= ~ 0 ) during initial stages of the Rayleigh frac-
Fig. 5. Two isotopic profiles and fluid inclusion data for prismatic-
scalenohedral calcite from Silvoova Diera Cave. The fluid inclu-
sion homogenization temperatures are consistent in all the growth
zones.
2
427
HYDROTHERMAL KARSTIFICATION IN VADOSE CAVES (WESTERN CARPATHIANS)
Fig. 6. Isotopic profile and fluid inclusion data for scalenohedral calcite from the Nová Staniovská Cave. The fluid inclusion homogeniza-
tion temperatures in the rim are lower than those in the core.
Fig. 7. Mixing model (Zheng & Hoefs 1993a) applied to C- and O-
isotope composition of the prismatic-scalenohedral calcite. Iso-
tope compositions of two mixing fluids A and B are given in the
insert. C
A
/C
B
ratios denote relative carbon concentration in two
mixing fluids.
tionation. The fluid B could correspond to shallowly circulat-
ing meteoric water saturated with CO
2
of pedogenic origin
(δ
13
C
CO
2
= 25 ) produced by rainforest plants (e.g. Cerling
1984). The δD and δ
18
O values for the mixing fluids A and B
(34 and 5.5 , 54 and 8 , respectively) are roughly
identical with the recent meteoric water line (Craig 1961). The
δD values of the inclusion water (35 and 41 in the core
and rim, respectively) correspond to 10 and 35 % admixture
of the fluid B in the fluid A. It is interesting to note that input
of
18
O-depleted fluid B into the fluid A results in precipitation
of a
18
O-enriched calcite. Thus, at temperatures below 100 °C,
the mixing mechanism can produce inversely correlated
δD
fluid
δ
18
O
cc
and δ
13
C
cc
δ
18
O
cc
data arrays.
The proposed mixing model is, however, inconsistent with
the microthermometry data, because the calculated cooling
trajectory from 110 to 85 °C does not match the observed
nearly isothermal precipitation at ~80±20 °C (Fig. 5). More-
over, the essentially CO
2
-dominated, acidic mixture should
dissolve calcite, rather than precipitate it. In summary, the dis-
tinctive inversely correlated stable isotopic record in the pris-
matic-scalenohedral calcite cannot be interpreted in terms of a
geologically reasonable mixing model, assuming equilibrium
isotopic fractionation. The isotopic signature of the calcite is
428
ORVOOVÁ, HURAI, SIMON and WIEGEROVÁ
inconsistent with most features of the hydrothermal karst en-
vironments as defined by Dublyansky & Ford (1997).
Scalenohedral calcite
The positively correlated δ
13
C and δ
18
O values in the core
of the scalenohedral calcite are qualitatively similar to trends
observed in typical hydrothermal carbonates (e.g. Zheng &
Hoefs 1993b), although the small extent of fractionation (∆ =
0.4 for δ
18
O, 1 for δ
13
C) could also be explained in
terms of intracrystalline differences in natural carbonates (e.g.
Dickson 1997) without invoking isotopic, compositional and/
or temperature changes of the parental fluid. Alternatively, the
positively correlated δ
13
C and δ
18
O values can be interpreted
using optional precipitationdevolatilization, mixing, or fluid-
rock interaction models (Zheng & Hoefs 1993a).
The δ
13
C value of the fluid parental to the scalenohedral
calcite can vary only in relatively narrow interval within
5±1 , what corresponds to carbonates from most hydro-
thermal deposits fluxed with CO
2
from the Earths mantle or
magmatic intrusions (e.g. Hoefs 1997). However, CO
2
with a
similar isotopic ratio can also be generated by acid leaching of
fresh limestone with δ
13
C ~ 0 at around 100 °C, or hydro-
thermally altered limestone with δ
13
C <<0 at proportional-
ly higher temperatures (e.g. Ohmoto & Rye 1979). Alterna-
tively, the δ
13
C
fluid
value of 5 can be obtained by mixing
of
13
C-enriched CO
2
from dissolved unaltered carbonate with
organic matter-derived CO
2
.
Assuming oxygen isotope fractionation in the calcitewater
system (ONeil 1969) and temperatures obtained from fluid
inclusions, an aqueous fluid with δ
18
O between 0 and 5
must have been present during growth of the core of the scale-
nohedral calcite. Such an isotopic signature can be attributed
to magmatic, formation, metamorphic, or meteoric water and
their mixtures equilibrated by interaction with dissolving
limestone at low fluid/rock ratio. Neither of the alternatives,
however, is unequivocally supported by the fluid inclusion
data. The measured salinity (02.7 wt. % NaCl eq.) is consid-
erably lower than the value of ~20 wt. % commonly attribut-
ed to a typical formation water (e.g. DeVivo et al. 1987).
Abrupt enrichment in deuterium of the inclusion water to as
much as 11 in the rhythmically banded rim of the scale-
nohedral calcite probably results from contamination from
clay particles, which could liberate water at grinding. The oth-
er δD values for prismatic-scalenohedral (from 31 to 45 )
and scalenohedral calcites (50 ) are significantly higher
than the average of recent meteoric waters (70 ) in the
studied area. Thus, the calcite crystals are interpreted as hav-
ing formed in a warmer climatic period, during which the me-
teoric waters with higher D/H isotope ratios circulated. Except
for the low δ
18
O and δ
13
C values, fluid inclusion and isotope
characteristics of the scalenohedral calcite overlap nearly all
essential features postulated by Dublyansky & Ford (1997)
for a deep-seated hydrothermal karst.
The age of hydrothermal karstification
The structure of the studied area is complicated due to over-
turned folds, local digitations and recurrent bedding sequenc-
es caused by normal faulting. The complicated setting is influ-
enced mostly by neo-Alpine deformations. The formation of
joint and fault systems in the sedimentary cover is only poorly
constrained due to inhomogeneity and strong rotation. How-
ever, the sedimentary cover and crystalline basement are in-
terconnected with the NS and WNWESE-trending fault
systems, along which vadose caves originated. The NS to
NNWSSE-trending faults in the Silvoova Diera and the
Nová Staniovská Caves are probably coeval with the uplift-
related shear fractures of strike-slip origin in the southern part
of a Paleogene basin located north of the study area (Marko
1995). The WNWESE-trending faults have been linked with
post-Paleogene down-slip faults limiting horst structure along
the northern margin of the Nízke Tatry Mts (Mahe¾ 1986).
Transversal NWSE tectonics were connected with uplift at
4052 Ma constrained by apatite fission-track dating (Krá¾
1977). Intense block movements and rejuvenation of older
fault systems also occurred during the Neogene (Nemèok
1989) and Middle Pleistocene (Droppa 1964). The fossiliza-
tion of the caves in an extremely high altitude position results
from Pliocene processes, as indicated by the magneto-strati-
graphic interpretation of the cave fills (Kadlec et al. 2002).
Hydrothermal karstification in the Nízke Tatry Mountains can
therefore be placed in pre-Pliocene times, most likely in the
Paleogene.
Conclusions
1. Vadose caves uncovered an earlier hydrothermal pale-
okarst system in the northern slopes of the Nízke Tatry Moun-
tains.
2. Two morphological types of hydrothermal calcite with
distinctive isotopic signatures have been distinguished.
3. Hydrothermal fluids with temperatures between 50 and
107 °C were discharged along regional NS-trending fault
systems, which were reactivated during Paleogenepre-
Pliocene times.
4. The isotopic characteristics of the calcite differ in many
aspects from those typical of hydrothermal caves in Hungary.
Acknowledgments: The manuscript has benefited from per-
ceptive reviews by V. Suchý, A. Demény, and J. Zachariá.
We acknowledge K. ák (Czech Geological Survey, Prague)
for many valuable comments, O. Lintnerová (Comenius Uni-
versity, Bratislava) for critical review of the manuscript, and
P. Bosák (Academy of Sciences CR, Prague) for assistance
during preparation of the manuscript.
References
Bac-Moszaszwilli M. & Rudnicki J. 1991: Dziura Cave. Example of
hydrothermal karst in Tatras. Tatry 1, 1012 (in Polish).
Bodnar R.J. 1993: Revised equation and table for determining the
freezing point depression of H
2
O-NaCl solutions. Geochim.
Cosmochim. Acta 57, 683684.
Borisenko A.S. 1977: The study of salt composition of fluid inclu-
sions in minerals using the cryometric technique. Geol. i
Geofiz. 8, 1627 (in Russian).
429
HYDROTHERMAL KARSTIFICATION IN VADOSE CAVES (WESTERN CARPATHIANS)
Bosák P. 1993: Evolution of karst on Tyuya-Muyun deposit in
Khyrgyzstan. Knih. Èes. Speleol. Spol. 21, 6168 (in Czech).
Cerling T.E. 1984: The stable isotopic composition of modern soil
carbonate and its relationship to climate. Earth Planet. Sci.
Lett. 71, 229240.
Cordingley J. 2000: Vein cavities in the Castleton caves: further in-
formation. Cave Karst Sci. 27, 8588.
Craig H. 1961: Isotopic variations in meteoric waters. Science 133,
17021703.
Demény A., Forisz I. & Molnár F. 1994: Stable isotope and chemi-
cal compositions of carbonate ocelli and veins in Mesozoic
lamprophyres of Hungary. Eur. J. Mineral. 6, 679690.
DeVivo B., Maiorani A., Perna G. & Turi B. 1987: Fluid inclusion
and stable isotope studies of calcite, quartz and barite from
karstic caves in the Masua Mine, Southwestern Sardinia, Italy.
Chem. d. Erde 46, 259273.
Dickson J.A.D. 1997: Synchronous intracrystalline δ
13
C and δ
18
O
differences in natural calcite crystals. Mineral. Mag. 61,
243248.
Droppa A. 1964: Paralellisation of river terraces and horizontal
caves. Geol. Práce, Spr. 64, 9396 (in Slovak).
Dublyanski V.N. & Lomaev A.A. 1980: Karst caves of Ukraine.
Naukova Dumka, Kiev, 1180 (in Russian).
Dublyansky Y.V. 1995: Speleogenetic history of the Hungarian hy-
drothermal karst. Environmental Geol. 25, 2435.
Dublyansky Y. 1997: Transition between hydrothermal and cold-
water karst. In: Jeannin J.Y. (Ed.): Proceedings of the 12
th
Intl.
Congress of Speleology, La Chaux de Fonds, Switzerland, Au-
gust 1017, 1997. Swiss Speleol. Soc., 267270.
Dublyansky Y. & Ford D. 1997: Paleoenvironment in hydrothermal
karst: evidence from fluid inclusions and isotopes of carbon
and oxygen. In: Boiron M.C. & Pironon J. (Eds.): XIV
th
Euro-
pean Current Research on Fluid Inclusions, Nancy, France,
July 14, 1997. Abstracts 9293.
Ford T.D. 1995: Some thoughts on hydrothermal karst. Cave Karst
Sci. 22, 107118.
Ford T.D. 2000: Vein cavities: an early stage in the evolution of the
Castleton Caves, Derbyshire, UK. Cave Karst Sci. 27, 514.
Friedman I. & ONeil J.R. 1977: Compilation of stable isotope frac-
tionation factors of geochemical interest. U.S. Geol. Surv. Pro-
fess. Paper 440-KK.
Goldstein R.H. & Reynolds T.J. 1994: Systematics of fluid inclu-
sions in diagenetic minerals. SEPM Short Course 31, 1212.
Haas J.L. Jr. 1976: Physical properties of the coexisting phases and
the thermochemical properties of the H
2
O component in boil-
ing NaCl solutions. U.S. Geol. Surv. Bull. 1421-A, 173.
Hoefs J. 1997: Stable isotope geochemistry. Springer, Berlin,
Heidelberg, New York, 1201.
Hochmuth Z. & Holúbek P. 1996: Survey and investigation of the
Nová Staniovská Cave. Spravodaj SSS 1, 1923 (in Slovak).
Kadlec J., Pruner P., Chadima M. & Bosák P. 2002: Magnetostratig-
raphy and mineral magnetic properties of cave deposits pre-
served in cave systems located in the Nízke Tatry Mts.
(Slovakia) preliminary results (abs.). 8
th
Castle Meeting:
Paleo, Rock and Environmental Magnetism: 1p. Geophys. Inst.
AS CR and Geophys. Inst. SAS, PrahaBratislava.
Krá¾ J. 1977: Fission track ages of apatites from some granitoid
rocks in Western Carpathians. Geol. Zbor. Geol. Carpath. 28,
269276.
Mahe¾ M. 1986: Geological structure of the Czechoslovakian Car-
pathians. I. Paleoalpine units. VEDA, Bratislava, 1510 (in
Slovak).
Marko F. 1995: Dynamic analysis of fault distortion of the Central
Carpathian Paleogene basin on the basis of structural observa-
tions from the northwestern and southern periphery of the
Levoèské Vrchy Mountains. Open File Report. GÚ SAV, Brat-
islava, 124 (in Slovak).
McCrea J.M. 1950: On the isotopic chemistry of carbonates and a
paleotemperature scale. J. Chem. Phys. 18, 849857.
Nemèok M. 1989: Structural tectonics of the Dead Bats Cave. Open
File Report SMOPaJ, Liptovský Mikulá, 140 (in Slovak).
Ohmoto H. & Rye R.O. 1979: Isotopes of sulphur and carbon. In:
Barnes H.L. (Ed.): Geochemistry of hydrothermal deposits.
John Wiley and Sons, Inc., New York, 509563.
Orvoová M. 1999: Allochthonous sediments in caves of the Nízke
Tatry Mts. Open File Report SMOPaJ, Liptovský Mikulá, 1
32 (in Slovak).
Osborne R.A.L. 1999: The origin of Jenolan Caves: Elements of a
new synthesis and framework chronology. Proc. Linn. Soc.
N.S.W. 121, 127.
Osborne R.A.L. 2000: Paleokarst and its significance for speleogen-
esis. In: Klimchouk A.B., Ford D.C., Palmer A.N. & Dreybrodt
W. (Eds.): Speleogenesis. Evolution of karst aquifers. Natl.
Speleol. Soc., Huntsville, 113123.
Osborne R.A.L. & Cooper I.B. 2001: Sulfide-bearing palaeokarst
deposits at Lune River Quarry, Ida Bay, Tasmania. Aust. J.
Earth Sci. 48, 409416.
Rimstidt J.D. 1997: Gangue mineral transport and deposition. In:
Barnes H.L. (Ed.): Geochemistry of hydrothermal deposits.
John Wiley and Sons, Inc., New York, 487515.
Roedder E. 1984: Fluid inclusions. Mineral. Soc. Amer., Rev. Min-
eral. 12, 1644.
Segnit E.R., Holland H.D. & Biscardi C.J. 1962: The solubility of
calcite in aqueous solutions I. The solubility of calcite in
water between 75° and 200 °C and CO
2
pressures up to 60 atm.
Geochim. Cosmochim. Acta 26, 13011331.
Sgibnev V.V. 1989: Tectonic boundaries and stages of karstification
in Tien-Shan. Proc. 10
th
Int. Congr. Speleol. Budapest, Vol. 1,
186187.
Simon K. 2001: Does δD from fluid inclusion in quartz reflect the
original hydrothermal fluid? Chem. Geol. 177, 483495.
Votoupal S. & Holúbek P. 1996: A new speleological locality at the
Ohnite the Silvoova Diera cave. Spravodaj SSS 1, 3941
(in Slovak).
Zheng Y.F. 1990: Carbon-oxygen isotopic covariation in hydrother-
mal calcite during degassing of CO
2
. Mineral. Deposita 25,
246250.
Zheng Y.F. & Hoefs J. 1993a: Carbon and oxygen isotopic covaria-
tions in hydrothermal calcites. Theoretical modeling on mixing
processes and application to Pb-Zn deposits in the Harz Moun-
tains, Germany. Mineral. Deposita 28, 7989.
Zheng Y.F. & Hoefs J. 1993b: Stable isotope geochemistry of hy-
drothermal mineralizations in the Harz Mountains: I. Carbon
and oxygen isotopes of carbonates and implications for the ori-
gin of hydrothermal fluids. Monogr. Ser. Mineral. Deposita 30,
169187.