GEOLOGICA CARPATHICA, 53, 5, BRATISLAVA, OCTOBER 2002
303 — 314
RELATIONSHIPS BETWEEN VOLCANISM AND HYDROTHERMAL
ACTIVITY IN THE TOKAJ MOUNTAINS, NORTHEAST HUNGARY,
BASED ON K-Ar AGES
and FERENC MOLNÁR
Institute of Nuclear Research, Hungarian Academy of Sciences (ATOMKI), Bem tér 18, 4026 Debrecen, Hungary;
Department of Mineralogy, Eötvös Loránd University (ELTE), Pázmány Péter sétány 1/C, 1117 Budapest, Hungary; firstname.lastname@example.org
(Manuscript received June 27, 2001; accepted in revised form March 19, 2002)
Abstract: Conventional K-Ar studies of volcanic rocks, rock-forming minerals and hydrothermal adularia and alunite
from different volcanic centres of the Tokaj Mts indicate that volcanic activity took place between 15.2 and 9.4 Ma
(Badenian—Sarmatian—Pannonian). In the northern part of the Tokaj Mts, ages for the relatively deeply eroded hydrother-
mal systems (Rudabányácska and Telkibánya Au-Ag deposits and parts of the Regéc caldera), formed mainly by the
adularia-bearing low-sulphidation epithermal deposits, are between 13.0 and 12.2 Ma. These systems were developed
within andesitic-dacitic volcanic centres with calderas and subvolcanic intrusions. In the southern parts of the Tokaj Mts
(near Mád and in the Szerencs Hills region) exposures of hydrothermal systems mainly represent shallow acid-sulphate
steam-heated zones of low-sulphidation-type systems, and the K-Ar ages are between 12.1 and 10.4 Ma. Radiometric
ages also suggest that in some parts of this latter area, repeated hydrothermal activity occurred, suggesting that hydro-
thermal circulation developed in relation to different magmatic centres that were active at different times.
Key words: Carpathians, Miocene volcanism, epithermal deposits, K-Ar ages.
The Neogene-Quaternary volcanic units of the Carpathians
and connected basin areas (Pannonian Basin, Transylvanian
Basin) are divided into four major groups (Pécskay et al. 1995;
Lexa 1999). The calc-alkaline ignimbrite and felsic tuff units
are regionally distributed in the basin areas where they are
largely covered by young sediments. K-Ar dating of these
units (Pécskay et al. 1995) showed that most deposition took
place between 20 and 10 Ma. The low- to high-potassium
calc-alkaline intermediate-felsic units are associated with
large stratovolcanoes in the Western Carpathians (Central Slo-
vak Volcanic Field, Börzsöny-Dunazug Mts, Mátra Mts, Tokaj
Mts, covered volcanics of the Trans-Tisza Region of Hungary)
and in the Apuseni Mts were formed in the Miocene, between
16 and 7 Ma (Karpatian—Badenian—Sarmatian—Pannonian).
The arc-type, low- to high potassium calc-alkaline andesite,
basaltic andesite units are distributed from the Slanské and Vi-
horlat Mts through the Oas-Gutâi Mts to the Harghita Mts.
The major stages of volcanic eruption in this arc occurred from
13 to 0.2 Ma ago. The K-Ar ages for the local alkaline basaltic
volcanism developed in the back-arc extensional regime, are
between 11.5 and 0.35 Ma.
Among the different volcanic groups only the intermediate-
felsic units associated with stratovolcanoes and the andesitic
arc-type units are characterized by metallogenetically impor-
tant hydrothermal activity. Although there is abundant K-Ar
data for the various volcanic rocks from these units (Pécskay
et al. 1995), systematic radiometric age determination of hy-
drothermal activity has rarely been conducted (there are some
data from the Gutâi Mts and the Central Slovak Volcanic
Field; Kovacs et al. 1997; Chernyshev et al. 1995). Thus the
age relationships between the various eruption stages and dep-
osition of hydrothermal minerals in volcanic centers has not
yet been documented. In this paper we present the results of
comparative radiometric dating of volcanic rocks and hydro-
thermal minerals from various volcanic centers and related
mineralized areas of the Tokaj Mts.
General characteristics of volcanism and
hydrothermal activity in the Tokaj Mts
The intermediate-felsic calc-alkaline volcanic rocks of Bad-
enian to Pannonian age of the Tokaj Mts were deposited in a
N-S trending graben-like structure in northeast Hungary (ca.
100 km long and 25—30 km wide; Pantó 1968; Gyarmati
1977). The basement units consist of various Precambrian and
Paleozoic metamorphic rocks, which crop out along the north-
eastern boundary of the graben (Fig. 1).
Miocene volcanism in the Tokaj Mts took place in two ma-
jor stages (Gyarmati 1977). The older (Badenian) volcanic
stage began with ignimbrite and felsic tuff eruptions along the
Szamos Line (Fig. 1). The subsidence of the basement resulted
in marine transgression, and the accumulation of thick Bade-
nian andesitic and dacitic lava flows took place under subma-
rine conditions along the axis of the graben. For the late stage
of Badenian volcanism, some areas were uplifted and andesit-
ic-dacitic subvolcanic bodies intruded into the earlier volcanic
and sedimentary units. The Badenian rocks crop out only in
the northeastern part of the Tokaj Mts; they are covered by
Sarmatian-Pannonian volcanic and sedimentary accumula-
tions in other parts of the mountains.
The initial stages of the Sarmatian-Pannonian volcanic cycle
in the Tokaj Mts started in partly subaqueous and partly sub-
aerial conditions, corresponding to a terrestrial environment
304 PÉCSKAY and MOLNÁR
Fig. 1. Simplified geological map of the Tokaj Mts (redrawn after Gyarmati et al. 1976) with outlines of studied areas.
VOLCANISM AND HYDROTHERMAL ACTIVITY IN THE TOKAJ MTS 305
dissected by lagoons and bays. This initial stage was charac-
terized by accumulation of felsic tuff commonly intercalated
with shallow marine clay and marl. In the central and northern
part of the Tokaj Mts, initial felsic pyroclastic deposition was
followed by formation of subaerial andesitic stratovolcanoes
(Telkibánya and Regéc; Fig. 1). Synchronous with andesitic
volcanism, rhyolite dome-flow complexes were formed in the
Mád area as well as southeast of Telkibánya (Fig. 1). In the
late stages of Sarmatian-Pannonian volcanism, andesitic dikes
and flows related to fissure-volcanism were emplaced in the
axial part of the mountains. Dacite extruded along the margin-
al zones of the graben-structure. The youngest product of vol-
canism is olivine basalt known from drilling along the eastern
boundary of the graben (Fig. 1).
The magmatism related to both Badenian and Sarmatian-
Pannonian volcanism generated hydrothermal activity. How-
ever, hydrothermal environments in Badenian volcanic rocks
are known mostly from deep drilling; their exposures are limit-
ed to the northeastern part of the Tokaj Mts. (e.g. the Rud-
abányácska area; Fig. 1). The mineralized zones in both Bade-
nian and Sarmatian sequences are typical examples of
low-sulphidation-type epithermal environments, with different
levels of erosion in exposures of various parts of the Tokaj Mts
(Molnár et al. 1999). The most deeply eroded zones are char-
acterized by adularia-sericite alteration, which crops out in the
vicinity of Rudabányácska, Telkibánya and Regéc (Fig. 1).
Remnants of the shallower, acid-sulphate steam-heated alter-
ation zones are also present at Telkibánya and Regéc; howev-
er, this type of hydrothermal alteration predominates on the
surface at Mád and in the Szerencs Hills, north of Szerencs
(Fig. 1). The essentially non-eroded, distal environments of
hydrothermal systems are represented by limnic siliceous and
clay deposits near Mád and Regéc and in several other parts of
the Tokaj Mts.
Detailed K-Ar studies have been conducted on the volcanic
rocks and hydrothermal minerals from the following volcanic
and hydrothermal centers: Rudabányácska, Telkibánya,
Regéc, Mád and the Szerencs Hills.
Method of K-Ar study
The K-Ar age determinations of all samples were carried out
at the Institute of Nuclear Research of the Hungarian Acade-
my of Sciences (ATOMKI), Debrecen, Hungary, except for
some alunite samples (with S35 sample numbers, see Tables 2,
4 and 5) which were analysed at the Okayama University of
Fresh to highly altered (>8 wt. % K
O content due to K-
metasomatic alteration) volcanic rocks from drillcores and
outcrops were crushed, then a sample of the crushed rocks was
selected and pulverized. Rock-forming minerals (biotite, am-
phibole, and sanidine) were separated from the host rocks by a
combination of magnetic and heavy-liquid methods. Hydro-
thermal minerals (adularia and alunite) were handpicked from
fractures and cavities of host rocks. Ultrasonic washing in
tubes produced clean mineral surfaces. Alunite samples were
chemically treated following the method of Itaya et al. (1996)
to remove small amounts of contaminant phases such as iron
minerals. As a consequence of this treatment, atmospheric ar-
gon contamination was significantly reduced.
Potassium determinations were made on about 100 mg por-
tions of the pulverized samples by means of a flame photome-
ter. For Ar analyses, approximately 500 mg of sample were
used. Details of analytical procedures (potassium determina-
tions, Ar extraction lines and mass spectrometers) are de-
scribed by Balogh (1985) and Itaya et al. (1996). All analytical
errors in this paper represent one sigma standard deviation (i.e.
a 68 % analytical confidence level).
Volcanism, hydrothermal processes and K-Ar ages
in different parts of the Tokaj Mts
The felsic pyroclastic deposits (ignimbrite, welded ignim-
brite, crystal tuff) of Badenian age are only a few hundred
meters thick and they cover Triassic-Jurassic carbonate units
that are underlain by metamorphic rocks at Rudabányácska
(Gyarmati & Pentelényi 1973). K-Ar ages for biotite and sani-
dine from the pyroclastic deposits are between 15.2 and 13.1
Ma (Fig. 2, Table 1). The eruption centers for ignimbrite are
probably along the Szamos Line (Gyarmati 1977); however,
there are also small rhyolite domes in the vicinity of Rud-
abányácska that have similar ages (13.0 Ma, Table 1). The py-
roclastic rocks were intruded by dacitic bodies (Száva Hill;
Fig. 2), which suffered hydrothermal alteration. Subsequent
andesitic dacitic-andesitic lava flows covering ignimbrites are
fresh. K-Ar data for whole-rock and amphibole samples sug-
gest a Sarmatian age for intermediate lava flows in this area
(12.4—12.2 Ma, Table 1).
The hydrothermally altered rocks of the area occur in a NW-
SE oriented zone nearly parallel to the Szamos Line (Fig. 2).
The most intense adularia-sericite-pyrite-hematite alteration
affected the felsic pyroclastic units of the Bányi Hill and the
dacite intrusion of Száva Hill (Fig. 2). The zone with adularia-
bearing alteration assemblage is surrounded by regional pro-
pylitized rocks (Varga-Máthé 1961). Rocks with adularia-
sericite alteration host a siliceous-pyritic disseminated-stock-
work gold deposit, which was exploited in medieval times.
According to fluid inclusion data, the deeper zones of the gold
deposit (Bányi Hill) formed at temperatures of 230—300 °C
during boiling of fluids, at a minimum depth of about 300 m
below the paleogroundwater table (Molnár 1994).
The K-Ar age of intrusive dacite from Száva Hill affected
by intense K-metasomatic (K-feldspar-sericite) alteration, is
13.2 Ma (Table 1). The K-Ar age for adularia from the stock-
work deposit of Bányi Hill is 13.0 Ma (Table 1). These data
suggest that hydrothermal mineralization of the area near Rud-
abányácska took place at the end of the Badenian rhyolitic-
dacitic volcanic stage and may be related to emplacement of
The volcanic and sedimentary sequence of Sarmatian-Pan-
nonian age that is exposed in the vicinity of Telkibánya is
306 PÉCSKAY and MOLNÁR
about 1 km thick and is underlain by Badenian intermediate
volcanic rocks, based on data from the 1240 m deep Telkibán-
ya-2 borehole (Széky-Fux 1970; Gyarmati 1977; Molnár et al.
1999). Interpretation of geophysical data by Zentai (1991) sug-
gests that the depth to the basement is about 2000 m.
Sarmatian volcanism started with ignimbrite and rhyolitic
tuff eruptions from a still recognizable volcanic center at the
northwestern end of Telkibánya village (Horváth et al. 1989;
Fig. 3). The early products of explosive activity accumulated
in subaqueous conditions and are interbedded with clay and
marl as well as coarse siliciclastic sedimentary rocks. The next
stage of volcanic evolution was characterized by the formation
of subaerial andesite stratovolcanic and caldera-like structures.
Horváth & Zelenka (1997) recognized two caldera structures,
Fig. 2. Simplified geological map of the Rudabányácska area (redrawn after Gyarmati et al. 1976), with the locations of samples for K-Ar dating.
Table 1: K-Ar data for fresh and altered rocks and hydrothermal minerals from the Rudabányácska area. 1 – Pécskay et al. (1986).
type of hydro-
Type of rock and
Nagy Szava Hill
VOLCANISM AND HYDROTHERMAL ACTIVITY IN THE TOKAJ MTS 307
each about 5—7 km in diameter (Fig. 3). The K-Ar ages for
stratovolcano pyroxene- and amphibole- andesitic lava flows
are between 13.1 and 11.6 Ma (Table 2). Radiometric ages for
rhyolite and rhyodacite domes and flows that formed within
the calderas are between 12.6 and 11.5 Ma (Table 2). Accord-
ing to data from drillholes and interpretation of geophysical
data, a subvolcanic andesite intruded the southern caldera
structure during the late stages of volcanic evolution (Horváth
& Zelenka 1997; Zelenka et al. 2000).
At the time of the Sarmatian-Pannonian boundary, volcan-
ism was still active in the vicinity of Telkibánya. These young-
est volcanic rocks in the area occur as pyroxene andesite lava
flows and dikes (the so-called “upper pyroxene andesite” ac-
cording to Gyarmati 1977). The radiometric ages for these
units are between 10.9 and 10.6 Ma (Table 2).
The low-sulphidation type epithermal mineralization of the
area near Telkibánya is characterized by the occurrence of N-S
striking quartz veins in the central parts of caldera-like struc-
Fig. 3. Geological sketch-map of the Telkibánya ore deposit compiled on the basis of maps from Széky-Fux (1970), Gyarmati (1977),
Molnár (1993) and Horváth & Zelenka (1997), and locations of samples for K-Ar dating.
308 PÉCSKAY and MOLNÁR
tures (Fig. 3). Gold and silver from these veins was exploited
during the midle ages. The intermediate and felsic volcanic
rocks related to the caldera-like structures are characterized by
strong K-metasomatic (adularia-sericite) alteration along these
veins (Fig. 3) with >8 wt. % K
O content in the rocks (Széky-
Fux 1970; Molnár et al. 1999; Molnár & Pécskay 2000). The
K-metasomatic alteration pinches out at depth and is surround-
ed by a propylitic alteration halo. In some rhyolitic tuff and ig-
nimbrite units situated above the adularia-bearing alteration
zones, an acid-sulphate type steam-heated alteration zone with
kaolinite-alunite assemblage is also present (Molnár 1993;
Molnár et al. 1999). The formation of the quartz veins and hy-
drothermal wall rock alteration occurred at temperatures of
250 to 180 °C, during boiling of hydrothermal fluids. The min-
imum paleodepth of hydrothermal activity was around 200 to
500 m below the groundwater table (Molnár & Zelenka 1995).
The youngest pyroxene andesite dikes of the mineralized
area do not show hydrothermal alteration. This suggests that
the age of hydrothermal activity is older than the 10.9—10.6
Ma. K-Ar ages of the very strongly altered rocks with >8 wt.
O are between 12.4 and 11.5 Ma, and for adularia and
alunite from quartz veinlets and steam-heated alteration zones,
respectively, ages are between 12.5—12.2 Ma (Table 2). These
data reveal that hydrothermal activity immediately followed
the formation of the host rocks related to the caldera-like struc-
tures. The identical K-Ar ages of adularia and alunite indicate
that precipitation of alunite in the steam-heated alteration
zones was synchronous with the deposition of adularia in
veins formed during boiling within the same hydrothermal
In the central part of the Tokaj Mts, around Regéc, there is a
caldera-like circular structure, about 4 km in diameter (Ba-
jnóczi et al. 2000). Data from the Baskó-3 drillhole (Fig. 4)
shows that a subaerial stratovolcanic sequence consisting of
andesitic lava and pyroclastic units approximately 850 m
thick, as well as subvolcanic andesite bodies, accumulated
over the Badenian subaqueous intermediate lava flows during
the Lower Sarmatian. The K-Ar ages for the stratovolcanic
andesite lava flows and subvolcanic units are between 13.6
and 12.1 Ma (Table 3). The average of whole rock and biotite
K-Ar data from the dacitic dome situated in the center of the
caldera structure (Fig. 4) is 11.6 Ma (Table 3). The late-stage
pyroxene andesite flows related to fissure volcanism in the vi-
cinity of the caldera have K-Ar ages between 10.4 and 10.7
Ma (Table 3).
In the area of the caldera at Regéc, there are several hydro-
thermal centers hosted by regionally propylitized stratovolca-
nic andesite units. K-metasomatic (adularia-sericite) alteration
occurs along the quartz veins (Fig. 4). These veins formed at a
temperature between 170 and 190 °C. Boiling hydrothermal
fluids of mainly meteoric origin reacted with igneous rocks at
a minimum depth of 90—150 meters below the paleogroundwa-
ter table (Bajnóczi et al. 2000). In the tuffaceous units of the
stratovolcanic sequence, shallow steam-heated alteration
zones with alunite-argillite alteration assemblages are also
present. At some places in the caldera, the paleosurface of hy-
drothermal activity is still preserved with hydrothermal erup-
tion breccia and related layered siliceous deposits (Fig. 4).
Table 2: K-Ar data for fresh and altered rocks and hydrothermal minerals from Telkibánya. Reference: 1 – Pécskay et al. (1986).
type of hydro-
Type of rock and
Telkibánya. Fehér Hill
Telkibánya. Csengő adit
Telkibánya. Kánya Hill
Hollóháza. Szurok Hill
lava flows and
domes and cones
Telkibánya, Gyepű Hill
Telkibánya, Teréz adit
Telkibánya. Jó Hill
Nyíri Fehér Hill
Telkibánya, Medve Hill
Telkibánya, Baglyas Valley
Telkibánya. Kánya Hill
Telkibánya. Kánya Hill
Telkibánya. Kánya Hill
VOLCANISM AND HYDROTHERMAL ACTIVITY IN THE TOKAJ MTS 309
Table 3: K-Ar data for fresh and altered rocks and hydrothermal minerals from the Regéc area. Reference: 1 – Pécskay et al. (1986).
Fig. 4. Simplified geological map of the Regéc area (modified from Bajnóczi et al. 2000), with the locations of samples for K-Ar dating.
type of hydro-
Type of rock and
Regéc, Soltész Valley
lava flows and
Regéc, Vár Hill
Late dikes and
Regéc, Tokár Hill
Regéc, east of the Vár Hill
Regéc, east of the Vár Hill
Regéc, Csonkás Hill
310 PÉCSKAY and MOLNÁR
The dacite dome in the center of the caldera, as well as the
late-stage andesitic lava flows do not show the hydrothermal
alteration. This suggests that the age of the hydrothermal ac-
tivity is older than 11.6 Ma. In agreement with this, the K-Ar
ages for the rocks enriched in potassium due to adularia-seric-
ite alteration along the veins are between 12.3 and 11.8 Ma
and the age of alunite from a steam-heated alteration zone is
The results of K-Ar age determinations in the vicinity of
Regéc confirm that hydrothermal activity was related to the
formation of the stratovolcanic and caldera structures and pre-
ceded the last stages of volcanism within the caldera and its
In the southern part of the Tokaj Mts, near Mád, volcanic
rocks of Sarmatian-Pannonian age are exposed. Igneous rocks
of Badenian age are known only from the Tállya-15 drillhole
(Fig. 5) below 1000 m depth (Gyarmati 1977); K-Ar data for a
submarine andesite flow of the Badenian sequence is 14.2 Ma
The major part of the Sarmatian-Pannonian volcanic se-
quence consists of pumiceous glass tuff, pumiceous tuff, rhyo-
lite crystal tuff and ignimbrite. These pyroclastic rocks accu-
mulated both under subaqueous and subaerial conditions and
are interbedded and intercalated with shallow marine clay and
marl beds, as well as lacustrine clay and silica deposits. Zelen-
ka (1964) recognized five major periods of accumulation of py-
roclastic rocks. The eruption centres are marked by rhyolitic-
dacitic domes and associated pumiceous lava flows (Fig. 5).
The most intensive hydrothermally altered zone is situated
northeast of Mád. In this area, the exposures of volcanic rocks
consist of felsic pyroclastic deposits and dacitic-rhyolitic ex-
trusions and lava flows of the fourth major eruptive period of
the volcanic evolution (Zelenka 1964). K-Ar ages for dacitic
and rhyolitic rocks from the fourth volcanic period are be-
tween 12.8 and 11.1 Ma (Table 4). Accumulation of andesitic
lava flows, agglomerates and tuffs followed this stage. The
centre of the andesitic volcanism may be related to the loca-
tion of the subvolcanic andesitic intrusions found in the Mád
23 drillhole (Fig. 5). Radiometric ages for the subvolcanic
andesite and andesitic lava flows are between 11.8 and 11.5
Ma (Table 4). K-Ar data for the rhyolite domes and dacitic ex-
trusions of the fifth volcanic period of the area range from 10.8
to 9.8 Ma (Table 4).
In the area northeast of Mád, the hydrothermal alteration of
rhyolitic tuffs of the fourth and fifth volcanic stages represents
shallow acid-sulphate steam-heated zones of low sulphidation
type epithermal systems (Molnár et al. 1999). The typical al-
teration minerals are kaolinite and alunite associated with si-
licification. However, the steam-heated alteration zones also
contain N-S and NE-SW oriented quartz veins containing 1.7—
2.4 g/t Au in some places (Csongrádi & Zelenka 1995). Some
of these veins have quartz pseudomorphs after bladed calcite
suggesting that they were formed in a deeper position com-
pared to a steam-heated alteration level, during boiling of near-
neutral hydrothermal solutions (at around 180—200 °C, at a
depth of 100—160 m below the paleogroundwater table; Mol-
nár & Bajnóczi 1997). Field and paragenetic observations sup-
port a shallow steam-heated alteration which overprinted the
earlier wall rock alteration and vein formation. Thus we con-
Table 4: K-Ar ages of volcanic rocks and hydrothermal minerals from the Mád area. Reference: 1 – Pécskay et al. (1986); 2 – Itaya et al. (1996).
type of hydro-
Type of rock
stage, domes and
Tállya, Kopasz Hill
Mád, Harcsa Hill
5th volcanic stage
domes and flows
Mád, Király Hill
Mád, Mogyorós Hill
Mád, Mogyorós Hill
VOLCANISM AND HYDROTHERMAL ACTIVITY IN THE TOKAJ MTS 311
(Fig. 5). The oldest radiometric date is 12.2 Ma from a biotite
sample of a dacitic lava flow (Table 5). The K-Ar ages for the
rhyolitic lava flows in the uppermost levels of the volcanic se-
quence are between 11.7 and 11.3 Ma (Table 5).
The ignimbrite, rhyolitic tuff and re-deposited felsic tuff
units of the area are the host rocks of several acid-sulphate
steam-heated alteration zones. These are characterized by
strong silicification in their centre surrounded by an alunite-
kaolinite alteration halo (Molnár & Pécskay 2000). The K-Ar
ages from alunite samples of these alteration centres have es-
sentially the same range, between 12.4 and 10.4 Ma, as those
for the volcanic rocks of the area (Table 5). This indicates that
hydrothermal activity occurred at different periods of time in
different localities, most probably related to different eruptions
from the felsic volcanic centres.
Summary and conclusions
The results of detailed K-Ar dating indicate that polystage
volcanism of the Tokaj Mts took place between 15.2 and 9.4
clude that hydrothermal activity was extensive and had multi-
ple stages in the area northeast of Mád. In addition, between
the major mineralization stages the level of paleogroundwater
table changed significantly due to erosion and/or tectonic up-
K-Ar ages for alunite samples from various localities show a
rather wide range, between 11.7 and 10.9 Ma (Table 4). The
differences of these ages extend beyond the range of their stan-
dard deviation; therefore, radiometric ages also indicate the
multiple and extended nature of hydrothermal activity in the
area. Comparison of ages from alunite with those of volcanic
rocks supports the idea that each volcanic period generated its
own hydrothermal activity, and that this occurred in different
paleorelief settings. However, the youngest dacitic volcanic
rocks exposed on the Cigány Hil (Fig. 5, samples 832 and 880)
In the area of Szerencs Hills, felsic pyroclastic rocks and
rhyolitic-dacitic domes and lava flows occur at the surface
Fig. 5. Geological sketch-map of the southern part of the Tokaj Mts (redrawn after Gyarmati et al. 1976), with the location of samples for
K-Ar dating from the Mád and Szerencs areas.
312 PÉCSKAY and MOLNÁR
Table 5: K-Ar data for fresh rocks and hydrothermal mineral from the Szerencs area. Reference: 1 – Pécskay et al. (1986).
Fig. 6. Summary of K-Ar data from the various volcanic and hydrothermal centres of the Tokaj Mts. Shaded boxes: range of K-Ar data;
Empty boxes: range of K-Ar data +/- standard deviations.
type of hydro-
Type of rock and
Abaújszántó Sulyom Hill
Domes and flows
Golop, drillhole 51.2-
52.0 m (Somos Hill)
Monok Őr Hill
Monok, Kassa Hill
Monok, Kassa Hill
Szerencs, Fekete Hill
VOLCANISM AND HYDROTHERMAL ACTIVITY IN THE TOKAJ MTS 313
Ma (Fig. 6). This extended magmatism generated several hy-
drothermal systems in different parts of the region and there
was repeated hydrothermal activity in some areas.
The K-Ar ages for the oldest hydrothermal systems are be-
tween 13.0 and 12.2 Ma (Fig. 6). These systems are related to
intermediate (andesitic-dacitic) eruption centres characterized
by subvolcanic bodies which locally intruded into stratovolca-
no and caldera-like structures in the northern part of the Tokaj
Mts. Among these volcanic centres, the hydrothermal activity
may be connected to the emplacement of dacitic intrusions at
Rudabányácska. However, in the caldera-like structure near
Regéc, hydrothermal alteration can be related to the evolution
of an andesitic volcanism and extrusion of the dacite occurred
after the hydrothermal mineralization. At Telkibánya, hydro-
thermal activity appears to be contemporaneous with andesitic
and rhyolitic magmatism. The identical K-Ar ages for strongly
altered (K-metasomatized) rocks with greater than 8 wt. %
O content and hydrothermal minerals from the same areas,
indicate that such datings of completely altered rocks can be
used to determine the ages of hydrothermal activity with a high
confidence. The same ages for strongly altered (K-metasoma-
tized) rocks, adularia, and alunite from some of these occur-
rences indicate that acid-sulphate steam-heated alteration at
shallow levels was contemporaneous with adularia-sericite
mineralization in the deeper levels of the same hydrothermal
In the southern part of the Tokaj Mts (in the vicinity of Mád
and in the Szerencs Hills area), the ages of hydrothermal
alunite are between 12.1 and 10.4 Ma; thus, the hydrothermal
systems of this area are slightly younger compared to those of
the northern part of the Tokaj Mts (Fig. 6). In agreement with
this, hydrothermally altered areas in the southern Tokaj Mts are
also less eroded in comparison to the northern Tokaj Mts. In
the southern Tokaj Mts, the hydrothermal activity had an ex-
tended and polystage nature, suggesting that the felsic eruption
centres that were active at different times generated several in-
dependent hydrothermal systems. Succeeding hydrothermal
pulses at some localities are also recognized on the basis of an
overprint of contrasting mineral assemblages.
Acknowledgments: The National Science and Research Fund
(OTKA) No. T 029898 Project supported this work as well as
the Project Jap-26 of the Hungarian-Japanese Science and
Technology Agreement. The authors also express their thanks
to Dr Tibor Zelenka (Geological Survey of Hungary) for
countless discussions during this work and to Prof. David H.
Watkinson (Carleton U., Ottawa), Dr Jeffrey W. Hedenquist
(Ottawa), Dr Jaroslav Lexa (Geological Survey of Slovakia,
Bratislava) and to Dr Kadosa Balogh (Nuclear Research Cen-
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