GEOLOGICA CARPATHICA, 48, 5, BRATISLAVA, OCTOBER 1997
315–323
THE GENESIS OF MESOZOIC RED CALCITE DIKES OF THE
TRANSDANUBIAN RANGE (HUNGARY): FLUID INCLUSION
THERMOMETRY AND STABLE ISOTOPE COMPOSITIONS
ATTILA DEMÉNY
1
, ISTVÁN GATTER
2
and MIKLÓS KÁZMÉR
3
1
Laboratory for Geochemical Research, Hungarian Academy of Sciences, Budaörsi út 45, H-1112 Budapest, Hungary
2
Department of Mineralogy, Eötvös Loránd University, Múzeum krt. 4/A, H-1088 Budapest, Hungary
3
Department of Paleontology, Eötvös Loránd University, Ludovika tér 2, H-1083 Budapest, Hungary
(Manuscript received November 11, 1996; accepted in revised form June 24, 1997)
Abstract:
Red calcite dikes with widths of 1–3 m were formed during the middle and upper Cretaceous within
Mesozoic sedimentary carbonate rocks in the Transdanubian Range of Hungary. The dikes frequently develop a
complex zonation with fine-grained dark red calcite at their margins and purer and more coarsely crystalline calcite
toward their centres. The staining material responsible for their colour is amorphous Fe-oxide-hydroxide whose amount
remains below 1 %. The fluid inclusions of carbonates contain rather dilute (<3.5 NaCl eq. wt. %) solutions and
frequently show boiling phenomena. The evidence of boiling makes the use of T
h
data (100–190
o
C) as estimates of
formation temperatures possible. The T
h
-salinity plot of the microthermometric data reveals that boiling, cooling and
dilution processes were operating during calcite precipitation. The stable carbon and oxygen isotope compositions of
calcites and hydrogen isotope compositions of inclusion waters indicate that the formation of red calcite dikes was
induced by the ascent of magmatic H
2
O-CO
2
fluid which suffered degassing prior to and during dike formation and
was contaminated by meteoric waters originating from the neighbouring rocks. The assumed movements of the mag-
matic fluids fit well into the results of earlier studies which have shown direct effects of magmatic fluids around
lamprophyre dikes and influences of magmatic fluids in the formation of manganese oxide ores during the Cretaceous
in the area of the Transdanubian Range.
Key words:
Transdanubian Range, red calcite dikes, fluid inclusion microthermometry, stable isotope compositions,
fluid evolution.
have presumed that movements of magmatic fluids played a
major role in the formation of red calcite dikes, and — along
with age evidence — this led them to suggest a genetic link
with Cretaceous lamprophyre dikes of the same area. This sug-
gestion has further implications, since if these very different
formations are related, then the tectonic characteristics of the
red calcite dikes might be used for paleogeographical recon-
structions as has been done in the case of the lamprophyres
(Kázmér & Szabó 1989a,b). In this study we present fluid in-
clusion and stable isotope data for the red calcite dikes, and us-
ing these results we provide a model of magmatic fluid move-
ment and evolution by degassing and mixing with meteoric
fluids and evolution.
Geological background and samples
There is a single locality at Sümeg, which provides a con-
straint on the biostratigraphic age of the red calcite dikes. The
Sintérlap Quarry exposes the Tata Limestone Formation, cross-
cut by a 3 m wide dike in the western part of the quarry. The
Introduction
Spectacular, reddish brown calcite dikes several metres wide
cross-cut Mesozoic carbonate sequences in the Transdanubi-
an Central Range. Fragments of the dike-filling material are
popular among mineral collectors due to the intense, dark-red
to brown colour, unusual for calcite. The dikes are mostly in
Triassic carbonates, and have never been found in Tertiary
rocks. Although Wein (1977) suggested a post-Cenomanian–
pre-Senonian age for the dikes in the Buda Hills, there is only
a single locality at Sümeg, where a middle to upper Creta-
ceous age of the dikes can be determined (Haas et al. 1985).
Products of later hydrothermal activity are also widespread in
the Transdanubian Central Range. The origin and timing of ig-
neous dikes produced by Middle Miocene volcanism (Báldi &
Nagymarosy 1976), and of speleothems in the thermal karst of
the Buda hydrothermal zone (Alföldi 1979; Müller 1989; Ju-
hász et al. 1995) are well known. The appearances of these for-
mations are quite different from those of the red calcite dikes
indicating different origins. On the basis of results of a prelim-
inary stable isotope investigation, Demény & Kázmér (1994)
316 DEMÉNY, GATTER and KÁZMÉR
basal beds of the unconformably overlying Ugod Limestone
contain pebbles both of the Tata Limestone and of the red calcite
(Haas et al. 1985), proving that the hydrothermal activity re-
sponsible for the precipitation of the red calcite occurred be-
tween the deposition of the two formations. The Tata Limestone
consists of crinoid ossicles and extraclasts mostly derived from
Upper Jurassic–Lower Cretaceous limestone (Lelkes 1990). It is
widespread in the Transdanubian Central Range reaching a
thickness of up to 200 m. The Sümeg locality — where the up-
per part of the formation crops out — yielded the larger fora-
miniferal species Orbitolina (Mesorbitolina) texana (Roemer),
which lived from Late Aptian (Gargasian) to Middle Albian
(Görög 1996). Planktonic foraminifers from the same locality
indicate the Globigerinelloides algerianus Zone (Sidó in Haas et
al. 1985) of Late Aptian (Gargasian) age. Typical Clansayesian
index fossils (e.g. Ticinella bejauensis) are missing even in the
topmost beds. The locality Kálvária Hill at Tata (10 km NW
from Tatabánya) exposes the lowermost beds of the Tata Lime-
stone (Fülöp 1976). The condensed ammonite fauna from the
basal beds contains Early Aptian to earliest Albian species
(Szives 1996). We do not know, whether the deposition of the
Tata Limestone was isochronous or heterochronous along its ex-
tent. However, the meagre data suggest, that any dike cross-cut-
ting the Tata Limestone was certainly formed after the Middle
Aptian (Gargasian), and possibly after the earliest Albian age.
The major unconformity between the Tata and Ugod Lime-
stone Formations indicates the onset of the Senonian sedi-
mentary cycle. The rudist-bearing Ugod Limestone uncon-
formably covers the eroded surface of a tilted Tata Limestone
block, which hosts the red calcite dike. The rudists suggest a
Late Santonian to Early Campanian age for the deposition of
the Ugod Limestone (Czabalay 1982; Bignot et al. 1984;
Haas et al. 1985). Elsewhere the deposition of the Senonian
complex started in the Santonian (Haas et al. 1985). The ma-
rine Senonian sediments are underlain by terrestrial bauxite
and freshwater coal beds at nearby localities. Palynological
data suggest Coniacian (and possibly latest Turonian) as the
start of bauxite formation (Knauer & Siegl-Farkas 1992), i.e.
the end of tectonic activity.
Summarizing the above considerations, we can conclude
that dikes were opened and filled with red calcite not earlier
than during the Late Aptian and possibly after the earliest Al-
bian. Subaerial erosion of the red calcite and its host rock start-
ed not later than the Early Campanian, and took place in two
stages (Early Albian and Turonian-Coniacian). Both the Tata-
banya dike (Kesellő Hill, uppermost level of the quarry) and
the Piliscsaba-Jászfalu dike are hosted by Upper Triassic
Dachstein Limestone. The thickness of both dikes is variable,
up to several metres. There is no suitable sedimentary cover to
constrain the age of dike emplacement at either localities.
The dike of Sümeg has been studied by fluid inclusion ther-
mometry by Gatter (1984) who estimated the formation tem-
peratures at about 135–155
o
C. His cryoscopic measurements
indicate that the fluids were rather diluted having 0–3 %
NaCl equivalent salinity presumably in alkali bicarbonate
and/or alkali earth chloride form. No free CO
2
was observed
in the inclusion fluids by Gatter (1984), although it should be
noted that water might contain up to 3.6 wt. % of dissolved
CO
2
without developing a CO
2
hydrate on freezing. Tóth &
Gecse (1981) studied “dedolomitized” zones in Triassic dolo-
mites, whose appearance resemble that of the red calcite dikes
studied in this paper. They attributed the “dedolomitization” to
the influence of a magmatic body that supplied hydrothermal
fluids. Dedolomitization is actually calcitization of dolomite,
and can be produced by a variety of processes (diagenesis,
metamorphism, alteration by hydrothermal fluids, weathering,
etc.). Thus, the “dedolomitization” presumed by Tóth & Gecse
(1981) does not provide a plausible explanation for the forma-
tion of the red calcite dikes.
A total of 5 dikes at three localities (Fig. 1) has been sam-
pled for fluid inclusion thermometry and stable isotope analy-
sis. As a common feature, the dikes show complex zonation
proceeding from the neighbouring limestones toward dike
centers: fine-grained dark-red calcite — dark-red sparic calcite
— banded calcite with cm-scale concentric bands of white and
red calcite — pale red sparic calcite (Figs. 1, 2). Electron mi-
croprobe measurements proved that the dike carbonate is cal-
cite with negligible impurities. Since the marginal parts have
the darkest red colour, the staining material has been deter-
mined in these samples by XRD measurements. It is amor-
phous Fe-oxide-hydroxide, whose amount is <1 %. Beside
the Fe-oxide-hydroxide, in a dike at Tatabánya, xenomorphic
zircon, a TiO
2
phase and monazite grains (<10 µm) have also
been encountered. The sinuous contact between the dikes and
the neighbouring limestones (see Fig. 1) indicates that the
fluids responsible for calcite precipitation dissolved a signifi-
cant amount of limestone and thus might have had an acidic
pH. Colourless and white calcite veins formed at a later stage
cut the red calcite dikes.
Fig. 1.
Localities of red calcite dikes studied in the Transdanubian
Range (Hungary) and a schematic drawing of dike zonation. P —
Piliscsaba (2 dikes), T — Tatabánya (2 dikes), S — Sümeg (1 dike);
1
— fine-grained dark-red calcite, 2 — dark-red sparic calcite, 3 —
concentric bands of white and red calcites, 4 — pale red sparic cal-
cite, 5 — later colourless calcite veins cross-cutting the red calcite
dikes.
THE GENESIS OF MESOZOIC RED CALCITE DIKES OF THE TRANSDANUBIAN RANGE 317
Analytical methods
Microthermometric measurements were carried out on a
Chaixmeca stage (Poty et al. 1976) mounted on a Zeiss Am-
plival microscope using long working distance objectives (32
×
and 50
×
) at the Department of Mineralogy of the Eötvös
Loránd University, Budapest. Fluid inclusion data were ob-
tained from a total of ~20 double polished sections. The car-
bon and oxygen isotope composition of calcites were deter-
mined using the conventional phosphoric acid digestion
method of McCrea (1950). Fluid inclusion waters were re-
leased by vacuum crushing and thermal decrepitation (in the
case of calcites free of H-bearing impurities) after eliminating
absorbed water by heating the samples at 150
o
C for 2 hours
under vacuum. Inclusion waters were converted to hydrogen
gas by reaction with zinc alloy (obtained from Bloomington,
USA) at 480
o
C (Coleman et al. 1982) with special care for
variations of hydrogen/zinc ratios (Demény 1995).
13
C/
12
C,
18
O/
16
O and D/H ratios were determined using a Finnigan
MAT delta S mass spectrometer at the Laboratory for
Geochemical Research, Budapest. The isotopic compositions
are expressed in the traditional
δ
notation in ‰ relative to V-
PDB (
δ
13
C) and V-SMOW (
δ
18
O and
δ
D). Reproducibilities
of
δ
13
C and
δ
18
O values are better than ±0.2 ‰. Within this
analytical precision, theoretical data were obtained on the Har-
ding Iceland Spar standard (
δ
13
C = –4.80 ‰,
δ
18
O = 12.78 ‰,
Landis 1983). The
δ
D values are normalized to the V-SMOW–
SLAP scale and reproducible to ±2 ‰.
Results and Discussions
Fluid inclusion studies
Inclusion petrography
The fluid inclusion groups were characterized by phase re-
lations observed at room temperature. The genetic classifica-
tion is based on Roedder (1984). According to an earlier
study by Gatter (1984) and the present work, the fluid inclu-
sion characteristics of the examined samples are as follows.
1. Solid inclusions. Calcites often contain euhedral carbon-
ates a few tenths of µm in size. The red calcite samples contain
rounded limonite blebs (~0.1 µm).
2. One-phase (liquid) inclusions. These inclusions have pla-
nar shapes and were formed along healed fractures. They are
usually of secondary (S) type.
3. Vapour-rich inclusions. These inclusions are isometric,
having often negative crystal shape with dark contours. A thin
liquid film is sometimes visible.
Fig. 2.
Hand specimens of the main calcite types within the red calcite dikes of the Transdanubian Range. A. fine-grained dark red calcite,
B.
dark red sparic calcite, C. concentric bands of white and red calcites, D. pale red sparic calcite.
318 DEMÉNY, GATTER and KÁZMÉR
4. Two-phase (liquid+vapour) inclusions. These inclusions
appear in various forms:
i
. isolated, large (up to 100–200 µm), elongated inclusions
with negative rhombohedron or spindle shapes, arranged par-
allel to the rhombohedron’s planes. These inclusions can be
considered as primary (P type).
ii.
elongated, or tooth-like cavities (10–50 µm) cutting the
banded structure of the samples.
iii.
isometric rounded inclusions or corroded rhombohedron
forms (5–20 µm), usually confined to calcite growth zones. The
latter two types are classified as pseudosecondary (PS).
iv.
Secondary (S type) inclusions with planar shapes and
formed along healed fractures (50–100 µm).
5. Three-phase inclusions. The two-phase inclusions rarely
contain carbonate crystallites, 2–3 µm in diameter.
Microthermometry
Summary of the measurement statistics is given in Table 1.
The homogenization temperatures (T
h
) of the two-phase inclu-
sions range from 107 to 185
o
C. In all cases the homogeniza-
tion was observed in liquid phase. As shown in Fig. 3, there
are some small differences between the localities studied.
Cryoscopic measurements showed fluid freezing between
–45 and –35
o
C. During gradual reheating of the inclusions
to ambient temperature, slight, sometimes cloudy phase
changes were detected in the –40 to –35, –25 to –20 and –12
to –8
o
C intervals, indicating the presence of Na, Ca-chlo-
ride and alkali bicarbonate/sulphate in the solutions. No visi-
ble gas hydrates were observed.
The temperature of the last ice crystal disappearance (T
m/ice/
)
was observed between –1.6 and –0.1
o
C. The apparent salini-
Fig. 3.
Homogenization temperatures and salinities of fluid inclusions
of the red calcite dikes of the Transdanubian Range (Hungary).
Table 1:
Statistical data of microthermometric measurements on
fluid inclusions.
Homogenization temperatures [Th,
o
C]
Samples
n
min
max mean
std.
Gatter (1984)
45
106.7 168.3 146.1
11.8
VK-2
4
134.4 147.1 140.1 6
VK-3
4
129.5 156.9 144
11.2
VK-4
11
126.5 158.9 144.5
9.8
VK-5
10
115.2 149.6 132.4
9.5
VK-13 dark-red
13
122.4 138.3 129.6
5.4
VK-13 sparic
7
103.4 127
120.9
8.3
VK-19
10
156.8 176.3 162.6
5.9
VK-20 red
8
135.8 147
142.2
4.4
VK-20 white
10
134.4 147.1 141.1
4.5
VK-21
17
146.6 185.1 165.3
9.2
Temperatures of ice melting [T
m
(ice),
o
C]
Samples
n
min
max mean
std.
Gatter (1984)
17
-1.3
-0.5
-0.9
0.2
VK-2
0
VK-3
0
VK-4
1
-0.8
-0.8
VK-5
4
-1
-0.9 -1
0.1
VK-13 dark-red
4
-0.3
-0.1
-0.2
0.1
VK-13 sparic
0
VK-19
3
-0.3
-0.2
-0.3
0.1
VK-20 red
3
-0.3
-0.2
-0.3
0.1
VK-20 white
6
-0.2
-0.1
-0.2
0.1
VK-21
7
-1.6 -1
-1.2
0.2
Salinities [NaCl eg. wt %]
Samples
n
min
max mean
std.
Gatter (1984)
17
0.9
2.2
1.6
0.4
VK-2
0
VK-3
0
VK-4
1
1.4
1.4
VK-5
4
1.6
1.7
1.6
0.1
VK-13 dark-red
4
0.2
0.5
0.2
0.2
VK-13 sparic
0
VK-19
3
0.4
0.5
0.5
0.1
VK-20 red
3
1.4
1.7
1.6
0.1
VK-20 white
6
0.2
0.4
0.3
0.1
VK-21
7
1.7
2.7
2
0.2
THE GENESIS OF MESOZOIC RED CALCITE DIKES OF THE TRANSDANUBIAN RANGE 319
The limestones usually preserved their original sedimenta-
ry isotopic compositions, but strong
δ
13
C and
δ
18
O shifts
also occur (e.g. VK13/1) frequently associated with a colour
change of the limestone to pale red.
The isotopic compositions of the colourless calcite veins
and white calcite dikes are very different from those de-
scribed above with
δ
13
C data resembling those of limestones,
and
δ
18
O data shifted to more negative values (see Fig. 5),
thus their formation might be related to a later fluid move-
ment independent of the formation of the red calcite dikes.
Table 2:
Stable carbon, oxygen and hydrogen isotopic composi-
tions [%
o
] and water contents [ppm] of calcite samples and fluid
inclusions trapped in the calcites of the red calcite dikes of the
Transdanubian Range.
Samples
Description
δ
13
C
δ
18
O H
2
O
δ
D
Sümeg
VK1
limestone
0.2 26.7
VK2
dark-red calcite
-5.5 25.5 400
-35
VK3
banded dark-red calcite
-5.2 25.2 450
-27
VK4
concentric banded calcite
-7.5 25.6
95
-49
VK5
pale red sparic calcite
-3.2 25.6 100
-63
VK6/1
limestone
0.1 27.9
VK6/2
limestone
-0.3 27.9
VK6/3
dark-red calcite
-5.5 25.9
VK7/1
dark-red calcite
-5.3 25.8
VK7/2
colourless drusy calcite
-5.7 25.9 100 -102
VK8
dark-red sparic calcite
-6.1 25.4 515 -30
Tatabánya
VK10/1
limestone
2.3 29.6
VK10/2
limestone
2.3 29.7
VK10/3
dark-red calcite
-8.1 26.3
VK11
dark-red calcite
-7.3 26.1 650 -47
VK12
colourless drusy calcite
-3.6 17.3 20 -113
VK13/1
pale red calcite
-5.8 22.9
VK13/2
dark-red calcite
-7.1 25.7 1050 -36
VK13/3
dark-red sparic calcite
-9.7 25.7 450 -45
VK13/4
concentric banded calcite(red) -8.8 26.1
VK13/5
concentric banded calcite
(white)
-6.8 26.0
VK13/4+5
205 -64
VK13/4+5 Q
470
-69
VK13/6
colourless drusy calcite
-5.2 21.4 180 -47
Piliscsaba
VK18/1-1 limestone
0.2 26.2
VK18/1
limestone
-5.1 27.2
VK18/2
dark-red calcite
-9.1 24.5 1000
-48
VK19
dark-red calcite
-10.0 24.5 1060
-48
VK20
concentric banded calcite(red) -9.0 24.3
760
-49
VK21/1
pale red sparic calcite
-10.1 23.7
VK21/2
colourless drusy calcite
0.1 17.9
VK22Q
white calcite vein
1.0 16.5
95 -108
VK24Q
white calcite vein
0.5 16.5
44 -111
Fig. 4.
Salinity vs. homogenization temperatures of fluid inclusions
of the red calcite dikes of the Transdanubian Range (Hungary).
ties (expressed as NaCl eq. wt. %) range from 0 to 3.5 %
(Fig. 3).
Interpretation of fluid inclusion data
Boiling phenomena were observed in almost all the sam-
ples, thus the calcite precipitation took place along or close
to the boiling curve of the liquid system, making pressure
correction unnecessary (Potter 1978; Roedder & Bodnar
1980). It follows from this consideration that the T
h
data
provide the lower limit of formation temperature.
Using salinity and T
h
data pairs measured on the same inclu-
sions, the average fluid density is estimated at 0.90–0.95 g/cm
3
(Bodnar 1983). The dynamic features of the investigated fluids
can be studied on the salinity–T
h
plot (Fig. 4) introduced by
Hedenquist & Henley (1985) and Shepherd et al. (1985). Two
trends can be observed in Fig. 4. In the higher salinity field,
both cooling+dilution and boiling effects appear, whereas in
the lower salinity field only cooling+dilution processes can be
observed. The presence of trace amounts of CO
2
might be in-
dicated by salinity–T
h
correlations. However, this feature
would be concealed by the effect of coupled cooling and dilu-
tion. Thus, the influence of the CO
2
degasing cannot be as-
sessed unequivocally.
Stable isotope compositions
The stable carbon and oxygen isotope compositions of cal-
cites are listed in Table 2 and plotted in Fig. 5. Although the
data show a large scatter, some systematic trends within the
selected calcite types can be observed.
Based on the data from two sections of the dikes at Sümeg
and Tatabánya, the carbon isotope compositions of the red
calcite dikes display fluctuations (~4 ‰, see Fig. 6), as op-
posed to the
δ
18
O data which are almost constant. The dark-
red calcite of the dike margins have
δ
13
C data of –5.5 ‰
(VK2) and –7.1 ‰ (VK13/2), then the
δ
13
C values decrease
towards the dikes’ centers (VK4: –7.5 ‰, VK13/3: –9.7 ‰),
then increase again in the concentric banded calcite (VK5:
–3.2 ‰, VK13/5: –6.8 ‰). The
δ
13
C variation is <1 ‰ in the
Piliscsaba dike.
320 DEMÉNY, GATTER and KÁZMÉR
The stable hydrogen isotope compositions of fluid inclu-
sion waters are listed in Table 2 together with the water con-
tents of calcite samples. The
δ
D values scatter in a very wide
range from –113 ‰ to –27 ‰, showing correlation with the
water content (Fig. 7). The distribution of data points fits to a
curve of mixing of two components with
δ
D values of –120 ‰
and –35 ‰. The
δ
D variation is also correlated with the dike
zonation. The highest
δ
D values are found in the dark-red
calcite at dike margins, whereas progressively more negative
δ
D values appear toward the centres. The most deuterium-
depleted fluids were detected in the late calcite veins that
cross-cut the red calcite dikes. These late veins have sedi-
mentary
δ
13
C compositions, thus their formation might be re-
lated to movements of meteoric water carrying dissolved
sedimentary carbonate. Beside the observed shifts within in-
dividual dikes, the C and H isotope compositions of the dark-
red calcite of dike margins — which represents the beginning
of dike formation — display variations between different lo-
calities (Fig. 8).
Interpretation of the isotopic compositions
Since inclusions sample the dike-forming fluids and the car-
bonate is precipitated from the dissolved C, stable carbon and
hydrogen isotope compositions of calcites and inclusion waters
provide constraints on fluid origin, whereas the
δ
18
O data of
calcites largely depend on both fluid composition (related to
the origin) and precipitation temperature. Thus, using forma-
tion temperature estimations and oxygen isotope compositions
of the carbonates, the
δ
18
O compositions of the fluids can be
assessed, provided that the temperature dependence of the car-
bonate-water oxygen isotope fractionation is well established.
Fig. 9 shows the hydrogen and oxygen isotope compositions of
fluids measured and calculated using the relationship of O’Neil
et al. (1969) recalculated by Friedman & O’Neil (1977), re-
spectively. The isotopic compositions of the main water types
(after Sheppard 1986) are also shown for comparison. The data
points fall into the overlap area of several water types, however
the tendency of shifting to more negative
δ
D and
δ
18
O with
dike evolution appears in the figure.
The observed
δ
13
C,
δ
18
O and
δ
D changes during dike evo-
lution raise two questions. What is the origin of the fluid
whose movement gave rise to the formation of the red calcite
dikes? What kind of processes are responsible for the varia-
tions in the isotopic compositions?
The carbon isotope compositions of dissolved sedimentary
carbonate (0 ± 2 ‰), magmatic CO
2
(–8 to –4 ‰) and CO
2
derived from oxidation of organic matter (–30 to –20 ‰)
differ significantly from each other (Hoefs 1980). Thus, the
origin of the dissolved C derived from these sources can be
assessed by
δ
13
C measurements, although intermediate val-
ues can be produced by mixing of fluids of different origins.
The
δ
13
C data of the dark-red calcite of dike margins (–10 ‰
to –5.5 ‰) might indicate influence of magmatic CO
2
or a
fluid derived from mixing of CO
2
originated from oxidation
of organic matter and dissolved sedimentary carbonate. The
interpretation of the trend in
δ
13
C-
δ
D correlation in the dark-
red calcites (see Fig. 8) needs further considerations. Oxida-
tion of organic matter yields only a small amount of water,
although it is significantly depleted in deuterium (see Fig. 9).
The
δ
13
C data indicate that — assuming that the fluid is de-
rived from a sedimentary sequence — the amount of organic-
derived CO
2
in the total dissolved carbon would not have ex-
ceeded 50 %. Since the fluids were dominated by H
2
O, the
addition of proportional amounts of organic water (Sheppard
Fig. 5.
Stable carbon and oxygen isotope compositions (in ‰) in red
calcite dikes and associated rocks in the Transdanubian Range
(Hungary).
Fig. 6.
Internal variations of stable carbon and oxygen isotope com-
positions (in ‰) in red calcite dikes of the Transdanubian Range
(Hungary). 1 — dark-red calcite at dike margin, 2 — dark-red spar-
ic calcite zone, 3 — concentric banded calcite zone, 4 — pale red
sparic calcite zone.
Fig. 7.
Stable hydrogen isotope compositions of inclusion fluids vs.
water contents of the red calcite dikes of the Transdanubian Range
(Hungary).
THE GENESIS OF MESOZOIC RED CALCITE DIKES OF THE TRANSDANUBIAN RANGE 321
& Charef 1986) to the fluid would not shift its
δ
D value by
more than 1–2 ‰. On the contrary, a
δ
D difference of about
20 ‰ is observed in the dark-red calcites (Fig. 8).
Another possibility for explaining the variations is the as-
cent and evolution of magmatic fluids. The isotopic compo-
sitions of the dark-red calcite of the Sümeg dike are consis-
tent with a magmatic H
2
O-CO
2
fluid (see discussion above
and Fig. 9). Open system degassing of this fluid is suggested
by the ubiquitous appearance of boiling phenomena in fluid
inclusions, and — since the dark-red calcites were formed at
the beginning of dike formation — this degassing might
have started at deeper levels. The T
h
data give the minimum
temperature of calcite precipitation, thus, any preceding
process might have occurred at higher temperatures. The
dark-red calcites forming the dike margins have high
δ
D val-
ues up to –27 ‰. In complience with their
δ
13
C data which
indicate magmatic fluids, such high
δ
D values are frequent in
magmatic fluids derived from magma degassing at conver-
gent plate margins (Giggenbach 1992; D’Amore & Bologne-
si 1994). These data suggest that the fluids responsible for
the formation of the red calcite dikes originated from degas-
sing of a deep-seated magmatic source. This assumption is in
accord with the low salinities of the fluid inclusions, since
fluids derived from degassing would not contain high
amounts of dissolved material.
The other question to be discussed is the cause of isotopic
variations related to dike zonations. On the basis of the
above considerations, the isotope changes might be attribut-
ed to the evolution of extinquishing magmatic fluids, under-
going degassing and having been contaminated by a steady
influx of formation water of meteoric origin from the sur-
rounding sedimentary rocks. In order to test this hypothesis,
a model has been established using the following input data
and assumptions:
— starting compositions of the magmatic fluid are
δ
13
C =
–5.5 ‰,
δ
D = –27 ‰.
— the water content of the calcites precipitated from magmat-
ic and meteoric fluids (1000 ppm and 50 ppm, respectively)
are used to estimate the ratio of the fluid components.
—
the contaminating meteoric water has a
δ
D value of –120 ‰
and carried a dissolved CO
2
with
δ
13
C = 0 ‰. This so
lution is
assumed to have supplied about 1 % of the total C content of
the mixed meteoric-magmatic fluid at the beginning of red cal-
cite precipitation. The significance of the sedimentary C com-
ponent increases with the degree of CO
2
degassing from the
magmatic fluids.
— the CO
2
degassing might have occurred at or above the
calcite precipitation temperatures (>150–200
o
C). In the case
of an H
2
CO
3
-dominated system, the CO
2
-fluid carbon isotope
fractionation is 0 to ~1 ‰ (Deines et al. 1974; Robinson
1975), whereas the CO
2
-HCO
3
-
fractionation is about 2 ‰ at
150–200
o
C, tending to increase with temperature (see Fried-
man & O’Neil 1977, and references therein). The apparent
dissolution of the neighbouring limestone at the dike margins
indicates low-pH, H
2
CO
3
-dominated fluids. However, admix-
ing of solutions originating from the surrounding carbonate
rocks might have affected the pH conditions. Since we have
no exact data on the actual temperature of the CO
2
degassing
and the H
2
CO
3
-HCO
3
-
speciation, an arbitrary
δ
13
C(CO
2
-flu-
id) fractionation value of 2 ‰ was chosen.
Fig. 8.
Variations in stable hydrogen and carbon isotope composi-
tions (in ‰) of dark-red calcites of dike margins in different red cal-
cite dike localities.
Fig. 9.
Measured and calculated hydrogen and oxygen isotope com-
positions, respectively, of waters in equilibrium with red calcite
dikes and associated later colourless calcite veins of the Transdanu-
bian Range (Hungary).
δ
18
O data were calculated using the calcite-
water fractionation of O’Neil et al. (1967) re-calculated by Fried-
man and O’Neil (1977) and equilibrium temperatures estimated
from fluid inclusion microthermometry data (see text). Fields of
main water types are from Sheppard (1986). Squares — Sümeg, sol-
id circles
— Tatabánya, crosses — Piliscsaba.
Fig. 10.
δ
13
C vs.
δ
D plot of red calcite dikes and associated colourless
calcite veins of the Transdanubian Range (Hungary). Dashed line is
based on calculations for influences of fluid mixing and degassing
(see text). Arrows show trends from dike margins to centres.
322 DEMÉNY, GATTER and KÁZMÉR
— we assume that the depletion in the magmatic H
2
O is
equal to the degree of CO
2
degassing. These parameters have
similar meanings (i.e. rate of change) and quantities, thus
this assumption is used for the sake of simplicity. A compa-
rable approach was made by Zheng (1990) concerning CO
2
degassing and rate of calcite crystallization from an H
2
O-
CO
2
fluid.
— the CO
2
degassing took place in an open system, thus the
Rayleigh fractionation relationship is used.
The resulting model curve is shown in Fig. 10 together
with the measured isotopic compositions. The curve shows
similar
δ
13
C and
δ
D changes as those observed in the red
calcite dikes. This observation indicates that — although we
have made assumptions that might not be entirely valid —
the scenario of magmatic fluid evolution describes the actu-
al processes operating during the formation of the red cal-
cite dikes.
Correlations with other studies and further implications
Direct and indirect evidence of magmatic fluid influences
during the Cretaceous has been investigated by Demény
(1992), Demény et al. (1994) and Pantó et al. (1996). Direct
effects of the magmatic fluids appear in the formation of
ubiquitous carbonate veins around upper Cretaceous lampro-
phyre bodies which intruded into Mesozoic sedimentary car-
bonate sequences of the Transdanubian Range. The lampro-
phyre series has carbonatitic affinities as proved by the
appearance of carbonate ocelli of magmatic origin in these
rocks. Local enrichment resulted in ~50% carbonate, leading
Horváth et al. (1983) to classify these rocks as beforsite (do-
lomite-carbonatite). The isotopic compositions of the accom-
panying carbonate veins indicate the presence of magmatic
H
2
O-CO
2
fluids (Demény 1992; Demény et al. 1994).
Indirect evidence for the involvement of magmatic fluid
has been described in the Transdanubian Range by Pantó et
al. (1996) who have shown that secondary oxidation of man-
ganese carbonates and formation of Sr- and Ba-rich manga-
nese oxides (with up to 1 % Sr and 0.5 % Ba) in the Úrkút
Mn-deposit can be attributed to movements of magmatic flu-
ids during the middle Cretaceous.
These studies together with the results of the present work
indicate that a significant magmatic activity took place during
the Cretaceous within and underneath the Mesozoic complex
of the Transdanubian Range. During the Cretaceous, this sedi-
mentary complex was situated in an intermediate position be-
tween the units that now comprise the Mesozoic nappes of the
Southern Alps and the Northern Calcareous Alps several hun-
dred km from the Transdanubian Range to the west, thus be-
longing to the Alpine edifice. Kázmér & Szabó (1989a,b) have
suggested, that these magmatic activities were related to oro-
genic processes acting in the hinterland of the Alpine deforma-
tion front.
Conclusions
On the basis of fluid inclusion microthermometry, the for-
mation of Cretaceous red calcite dikes of the Transdanubian
Range was induced by movements of rather dilute (<3.5 NaCl
eq. wt. %) H
2
O-rich fluids at 100–190
o
C. The dikes were
formed in Mesozoic sedimentary carbonate rocks and general-
ly show complex zonation with fine-grained dark red calcite at
their margins stained by <1% Fe-oxide-hydroxide and more
pure and coarser grained calcite at their centres. They are cut
by colourless calcite veins. The stable C, H and O isotope
compositions of carbonates and their inclusion fluids are most
consistent with a magmatic origin. The isotopic compositions
correlate well with dike zonation which is attributed to the
coupled effects of CO
2
degassing and increasing contamina-
tion by meteoric waters during crack propagation. The forma-
tion of the late stage calcite veins can be assigned to move-
ments of meteoric solutions carrying dissolved sedimentary
carbonate.
The presumed movements of magmatic fluids are consis-
tent with the results of earlier studies of Cretaceous lampro-
phyre dikes and manganese oxide ores of the Transdanubian
Range whose formation provides evidence for direct and in-
direct magmatic influences in the area.
Acknowledgements
: We would like to thank M. Tóth, G. Nagy
and I. Fórizs for their valuable help during XRD and electron
microprobe measurements. The constructive reviews by
J. Haas, V. Hurai and J. Soták greatly helped to clarify our
ideas and are gratefully acknowledged. This work was finan-
cially supported by the Hungarian Scientific Research Fund
(OTKA 1154 and T 014968).
References
Alföldi L., 1979: Thermal waters of Budapest. VITUKI Köz-
lemények
, 20, 102.
Báldi T. & Nagymarosi A., 1976: Silicification of the Hárshegy Sand-
stone and its hydrothermal origin. Földt. Közl., 106, 257–275.
Bignot G., Haas J. & Poignant A.F., 1984: The limestone with Coral-
linaceae of the Upper Cretaceous of Sümeg (Transdanubia,
Hungary): paleogeographic implications. Acta Geologica Hun-
garica
, 27, 429–440.
Bodnar R.F., 1983: A method of calculating fluid inclusion volumes
based on vapor bubble diameters and PVTX properties of in-
clusion fluids. Econ. Geol., 78, 535–542.
Coleman M.L., Shepherd T.J., Durham J.J., Rouse J.E. & Moore
G.R., 1982: Reduction of water with zinc for hydrogen isotope
analysis. Anal. Chem., 54, 993–995.
Czabalay L., 1982: La faune des rudistes des environs de Sümeg
(Hongrie). Geologica Hungarica, Ser. Palaeontologica, 41, 221.
D’Amore F. & Bolognesi L., 1994: Isotopic evidence for a magmat-
ic contribution to fluids of the geothermal systems of Lardarel-
lo, Italy, and the Geysers, California. Geothermics, 23, 21–32.
Deines P., Langmuir D. & Harmon R.S., 1974: Stable carbon isotope
ratios and the existence of a gas phase in the evolution of car-
bonate ground waters. Geochim. Cosmochim. Acta, 38, 1147–
1164.
Demény A., 1992: Origin of carbonates in lamprophyres of Hunga-
ry: a stable isotope study. Földt. Közl., 122, 209–232 (in Hun-
garian with extended English abstract).
Demény A., 1995: H isotope fractionation due to hydrogen-zinc re-
actions and its implications on D/H analysis of water samples.
Chem. Geol.
, 121, 19–25.
Demény A. & Kázmér M., 1994: A stable isotope study on Creta-
THE GENESIS OF MESOZOIC RED CALCITE DIKES OF THE TRANSDANUBIAN RANGE 323
ceous magmatic influences in the Transdanubian Mid-Moun-
tains. Acta Mineral.-Petrogr. (Szeged), 35, 47–52.
Demény A., Fórizs I. & Molnár F., 1994: Stable isotope and chemi-
cal compositions of carbonate ocelli and veins in Mesozoic
lamprophyres of Hungary. Eur. J. Mineral., 6, 679–690.
Friedman I. & O’Neil J.R., 1977: Compilation of stable isotope frac-
tionation factors of geochemical interest. Data of Geochemis-
try 6th, Geol. Surv. Prof. Paper, 440-KK.
Fülöp J., 1976: The Mesozoic basement horst blocks of Tata. Geo-
logica Hungarica, Ser. Geologica
, 16, 229.
Gatter I., 1984: Investigation on embedded fluids in vein fillings
and in crusts precipitated from thermal waters on the walls of
caves in carbonate rocks. Karszt és Barlang, Budapest, 1, 9–18
(in Hungarian).
Giggenbach W.F., 1992: Isotopic shifts in waters from geothermal
and volcanic systems along convergent plate boundaries and
their origin. Earth Planet. Sci. Lett., 113, 495–510.
Görög Á., 1996: Palaeontology, stratigraphy, and ecology of Cretaceous
Orbitolinas in Hungary. Ph. D. thesis, Department of Palaeontolo-
gy
, Eötvös University, Budapest, 1–329 (in Hungarian).
Haas J., Edelényi E., Gidai L., Kaiser M., Kretzoi M. & Oravecz J.,
1984: Geology of the Sümeg area. Geologica Hungarica, Ser.
Geologica
, 20, 365.
Hedenquist J.F. & Henley R.W., 1985: The importance of CO
2
on
freezing point measurements of fluid inclusions: evidence from
active geothermal systems and implication for epithermal ore
deposition. Econ. Geol., 80, 1379–1406.
Hoefs J., 1980: Stable isotope geochemistry. Springer-Verlag, New
York, 208.
Horváth I., Tichy-Darida M. & Ódor L., 1983: Magnesitiferous do-
lomitic carbonatite (beforsite) dike rock from the Velence
Mountains. Annual Report of the Hungarian Geological Insti-
tute for 1981
, 369–389 (in Hungarian, English abstract).
Juhász E., Korpás L. & Balogh A., 1995: Two hundred million years
of karst history, Dachstein Limestone, Hungary. Sedimentolo-
gy
, 42, 473–489.
Kázmér M., 1986: Tectonic units of Hungary: Their boundaries and
stratigraphy (A bibliographic guide). Annales Universitatis
Scientiarum Budapestiensis, Sectio Geologica
, 26, 45–120.
Kázmér M. & Szabó Cs., 1989a: Late Cretaceous lamprophyre dikes
in the hinterland of the Alpine deformation front. EUG-V,
Strasbourg, Terra Abstracts
, 1/1, 177.
Kázmér M. & Szabó Cs., 1989b: Apulian plate margin geometry:
constraints inferred from Jurassic-Cretaceous neptunian and
plutonc dikes. Abstracts, 28th International Congress, Wash-
ington, D.C., 2, 167.
Knauer J. & Siegl-Farkas Á., 1992: Palynostratigraphic position of
the Senonian beds overlying the Upper Cretaceous bauxite for-
mations of the Bakony Mts. Annual Report of the Hungarian
Geological Institute for 1990
, 463–471.
Landis G.P., 1983: Harding Iceland Spar: A new
δ
18
O-
δ
13
C carbon-
ate standard for hydrothermal minerals. Chem. Geol. (Isot.
Geosci. Sect.)
, 1, 91–94.
Lelkes Gy., 1990: Microfacies study of the Tata Limestone Forma-
tion (Aptian) in the Northern Bakony Mountains, Hungary.
Cretaceous Research
, 11, 273–287.
McCrea J.M., 1950: On the isotopic chemistry of carbonates and a
paleotemperature scale. J. Chem. Phys., 18, 849–857.
Müller P., 1989: Hydrothermal paleokarst of Hungary. In: Bosák P.
(Ed.): Paleokarst, A Systematic and regional Review. Elsevier,
Amsterdam; Academia, Praha, 155–163.
O’Neil J.R., Clayton R.N. & Mayeda T.K., 1969: Oxygen isotope
fractionation in divalent metal carbonates. J. Chem. Phys., 51,
5547–5558.
Pantó Gy., Demény A. & Polgári M., 1996: Genesis of secondary
Mn-oxide ores in the Úrkút deposit (Hungary): An oxygen iso-
tope study. Mineralium Deposita, 31, 238–241.
Potter R.W. II, 1978: Pressure correction for fluid inclusion homog-
enization temperatures, based on the volumetric properties of
the system NaCl-H
2
O. J. Res. U.S. Geol. Surv., 5, 603–607.
Poty B., Leroy J. & Jachimovitz L., 1976: Un nouvel appareil por la
mesure des temperatures sous le microscope, l’installation de
microtermometrie CHAIXMECA. Bull. Soc. Fr. Min. Crist.,
99, 182–186.
Robinson B.W., 1975: Carbon and oxygen isotopic equilibrium in
hydrothemal calcites. Geochem. J., 9, 43–49.
Roedder E., 1984: Fluid inclusions. Rev. in Mineralogy, 12, 646.
Roedder E. & Bodnar R., 1980: Geologic pressure determinations
from fluid inclusion studies. Ann. Rev. Earth. Planet. Sci., 8,
263–301.
Shepherd T., Rankin A.H. & Alderton D.H.M., 1985: A practical guide
to fluid inclusion studies. Blackie and Son, Ltd., Glasgow, 239.
Sheppard S.M.F., 1986: Characterization and isotopic variations in
natural waters. In: Valley J.W., Taylor H.P., Jr. & O’Neil J.R.
(Eds.): Stable isotopes in high temperature geological process-
es.
Rev. in Mineralogy, 16, 165–184.
Sheppard S.M.F. & Charef A., 1986: Eau organique: caractérisation
isotopique et évidence de son rôle dans le gisement Pb-Zn de
Fedj-el-Adoum, Tunisie. C. R. Acad Sci. Paris, 302, série II,
1189–1192.
Szives O., 1996: Ammonites fauna from the basal beds of Tata
Limestone Formation, Tata, Hungary. M. Sc. thesis, Depart-
ment of Palaeontology, Eötvös University, Budapest
, 1–104 (in
Hungarian).
Tóth Á. & Gecse É., 1981: Dedolomitized dikes in the Upper Triassic
basement of the Nagyegyháza Basin. Annual Report of the Hun-
garian Geological Institute for 1979
, 181–200 (in Hungarian).
Wein Gy., 1977: Tectonics of Buda Hills, Budapest. Hungarian Geo-
logical Institute
, Budapest, 1–76 (in Hungarian).
Zheng Y.-F., 1990: Carbon-oxygen isotopic covariation in hydro-
thermal calcite during degassing of CO
2
. Mineralium Deposita,
25, 246–250.