GEOLOGICA CARPATHICA, 49, 2, BRATISLAVA, APRIL 1998
EPITHERMAL TERTIARY Pb-Zn-Cu (Ag, Te) MINERALIZATION IN
THE ROZTOKY VOLCANIC CENTRE, ÈESKÉ STØEDOHOØÍ MTS.,
, JAROMÍR ULRYCH
, VLADIMÍR REIN
, JIØÍ BENDL
Institute of Geology, Academy of Sciences of the Czech Republic, Rozvojová 135, 165 02 Praha 6, Czech Republic
Institute of Rock Structure and Mechanics, Academy of Sciences of the Czech Republic, V Holeovièkách 41, 182 09 Praha 8, Czech Republic
Analytika, l.c., U Elektry 650, 198 00 Praha 9, Czech Republic
Czech Geological Survey, Klárov 3, 118 00 Praha 1, Czech Republic
(Manuscript received May 20, 1997; accepted in revised form December 11, 1997)
Abstract: The abandoned Roztoky silver-base metal deposit represents a scarce example of Tertiary sulphide vein-
type mineralization spatially and genetically associated with intraplate volcanic rocks of the Cenozoic West and
Central European Volcanic Province. The deposit is situated in the Tertiary Roztoky Volcanic Centre (RVC) of the
Èeské støedohoøí Mts., within the Ohøe (Eger) Rift. The main ore vein parallels an older bostonite dyke intersecting
the monzodiorite body, however, both are intersected by a younger trachyte dike. This suggests that the origin of the
mineralization is related to the development of the RVC. The
C values of vein carbonates indicate the influence of
but the O isotopic composition of hydrothermal fluids (calculated
values from 3 to 7
SMOW) shows the dominance of water with relatively shallow circulation. Sphalerite-galena sulphur isotopic
geothermometry yielded temperatures between 200 and 250
C and the presence of cubic hessite indicates tempera-
tures above 155
C. The calculated
values vary in the range 1.0
to 2.0 . The presence of banded colloform
sphalerite and chalcedony suggests lower temperatures. High lead isotope ratios of galena (
Pb about 19.03,
Pb about 15.67,
Pb about 39.17) can be a result of mobilization of lead either from Tertiary magmatic
rocks, which show similar lead isotope ratios and were probably derived from a sublithospheric HIMU mantle source,
or from upper-crustal rocks, e.g. local Upper Cretaceous sediments. The
Sr isotope ratios of the principal hy-
drothermal carbonates rhodochrosite (0.70524) and calcite-dolomite (0.70510) are higher than both the local primi-
tive magma derivatives and even the developed rocks of the RVC and indicate an admixture of Sr derived from local
crustal rocks. The volcanic rocks of the RVC were the dominant heat source during the formation of the ore deposit.
The hydrothermal deposit was formed during relatively shallow hydrothermal circulation of low to medium salinity,
O fluids supported by CO
influx of deep-seated origin.
Key words: Tertiary, Bohemian Massif, epithermal mineralization, stable isotopes, Sr isotopes, alkaline volcanics.
There have been numerous publications over the last several
decades concerning the post-Variscan mineralization related
to the Alpine metallogenic epoch in the Bohemian Massif.
The post-Variscan mineralization includes, according to Lo-
sert & Chrt (1962), Hanu & Krs (1963), Losert (1964), Krs
& Vondrová (1965), Legierski (1973), Èadek et al. (1975),
Baumann (1977), Pivec et al. (1984), Vanìèek et al. (1985),
Thomas & Tischendorf (1987), Èadek & Malkovský (1988)
and ák et al. (1990), various types of fluorite, barite, urani-
um and sulphide (base-metal) mineralization. The Roztoky
deposit represents a scarce example (together with Tertiary
mineralization in Badenweiler and Wiesloch localities in
Rhinegraben, Gehlen 1987) of the Tertiary sulphide vein-
type mineralization spatially and genetically associated
with volcanic and subvolcanic rocks in the whole Cenozoic
West and Central European Volcanic Province. The Ohøe
(Eger) Rift zone, which hosts the Roztoky Volcanic Centre
(RVC) and Roztoky deposit, also contains widespread fluo-
rite and barite mineralization with fluorite deposition con-
tinuing even subrecently and recently from thermal springs
(e.g. in Teplice and Dìèín).
The Au±Ag±Te±base metal deposits related to alkaline ig-
neous rocks, known from numerous metallogenic provinces
around the world, constitute one of important sources of pre-
cious and related metals. Well known examples of alkalic-
type epithermal mineralization include Cripple Creek, Colo-
rado; Colorado mineral belt; Montana alkalic province;
Porgera, Mt. Kare, and Ladolam, Papua New Guinea etc. (Ri-
chards 1995). Within the Cenozoic West and Central Europe-
an Volcanic Province the occurrence of a deposit of this type
is quite exceptional. The purpose of this study is to summa-
rize the essential facts concerning this poorly known deposit.
Geological setting of the Roztoky ore district
The Roztoky (Rongstock in German) village is better
known from the petrologic literature as the type locality of the
Tertiary monzodiorite (rongstockite after Tröger 1935) rather
than the Pb-Zn-Cu (Ag, Te) deposit.
140 PIVEC, REIN, ULRYCH, BENDL, DOBE
The RVC is the main volcanic centre of the Èeské støe-
dohoøí Mts. and represents the main strongly differentiated
volcanic complex within the NESW trending Ohøe Rift. Vol-
canic activity ranges from 42to 10 Ma and frequently reveals
a bimodal character (basanitetrachyte), cf. Wilson et al.
(1994). Mantle derived alkali basaltic rocks display primitive
Sr ratios in a range from 0.7032 to 0.7037 (Vokurka &
Bendl 1992; Bendl et al. 1993; Wilson et al. 1994). A sub-
lithospheric HIMU mantle plume could have been the source
of the magma (Wilson et al. 1994).
The RVC occurs at the intersection of the hypothetical cen-
tral faults of the Ohøe Rift, which is the main rift zone of the
Bohemian Massif, and the Labe tectono-volcanic zone (Ko-
pecký 1978). The RVC crops out in the deeply eroded Labe
(Elbe) Valley. The central diatreme of the RVC is filled main-
ly by breccia of trachytic composition with carbonate-bearing
groundmass. The carbonate component of this breccia was
assumed to be of carbonatite origin by Kopecký (1978,
1987a). Younger trachytes and phonolites intrude into the
breccia. Intrusive bodies of olivine nephelinite, basanites and
phonolites in the vicinity outside the mentioned breccia, may
belong to the RVC as well. The southwest part of the RVC is
limited by a local fault intruded by breccia of lamprophyric
The proper environs of the deposit consist of a hypabyssal
body of monzodiorite situated at the southern margin of the
RVC as a circular segment, about 200 m in diameter, bound-
ed by the local fault in the W and by a block of contact meta-
morphosed marlstones of Late Cretaceous age towards the
NE (Fig. 1). This monzodiorite segment probably represents
part of an originaly bigger elliptical body (Hibsch 1899).
Stocks with eliptic shape of similar composition (essexites)
and one of sodalite syenite occur scattered in the near vicinity.
More than 1,000 dykes forming a radiating system and rare
cone-sheets extend up to 15 km from the centre of the RVC.
The trachytic breccia of diatreme is probably younger than
the older generation of lamprophyres but older than tin-
guaites (a textural variety of phonolite) and nepheline syenite
porphyry dykes. The dyke system consists of lamprophyres
and felsic derivatives-semilamprophyres and common rock
dykes (Jelínek et al. 1989). Trachyte and bostonite dykes (in
Fig. 1) belong to the dyke system mentioned above.
The Tertiary Pb-Zn-Cu (Ag, Te) bearing hydrothermal
veins are located mostly within the monzodiorite segment
and only partly in its marlstone envelope (Pivec et al. 1984),
see Fig. 1. The host rock of the ore veins (i.e. monzodiorite)
was dated by the K/Ar method (whole rock) at 29.5 Ma (H.
Bellon, Orsay Univ. Paris, in Kopecký 1987b).
The ore deposit
The deposit is formed by three parallel mineralized veins (Piv-
ec et al. 1984). The main vein parallels a 3 m thick bostonite
dyke of NESW direction and dips steeply 7075
to the NW.
The main vein was mined in its southwestern part mainly in the
16th century and prospected in the northeastern part during the
1953 to 1956 period. The length of this vein is about 500 m
(Fig. 1); its maximum thickness reaches 0.6 m. The hydrother-
mal filling is more widespread in sections where the vein occurs
just at the contact between altered bostonite and monzodiorite.
Where the vein parallels the bostonite dyke in the contact
metamorphosed marlstones, replacements and impregnations
from 2 to 10 cm thick are typically developed. Faults trending
NWSE, NS and EW disrupt the bostonite dyke and ore
vein. Both the dyke and the vein are slightly displaced and
younger trachyte dykes crosscut them. This fact proves that
ore formation coincided with the development of the RVC.
In the vein filling, sphalerite prevails over galena. Pyrite,
chalcopyrite, tetrahedrite, and hessite are present in minor
amounts. The gangue is composed of rhodochrosite, dolomite
and calcite (from oldest to youngest). Quartz, chalcedony, and
barite are present in minor amounts. The position of the main
ore minerals in the paragenetic sequence is shown in Fig. 2.
The structure of the vein filling often indicates a cessation
of mineralization due to tectonic movements. The breccia
consists of fragments of pyritized contact-metamorphosed
marlstone, bostonite, and monzodiorite. These fragments are
usually coated by sphalerite and galena, and cemented by car-
bonate gangue. Transitions of breccia structure to cockarde
structure were found. A special type of the breccia structure
formed by sphalerite crystals (about 2 cm in diameter) float-
ing in the host carbonate is characteristic for this locality.
The presence of collomorphous aggregates (Schalen-
blende) of sphalerite and a banded structure are local only.
The ore minerals were analyzed using a JEOL XA 50 A
electron microprobe, equipped with EDAX 711, operating at
Fig. 1. Geological map of the Roztoky deposit. (Modified after Pivec
et al. 1984). (Common symbol for railway in the lower part of Fig.)
EPITHERMAL TERTIARY Pb-Zn-Cu (Ag, Te) MINERALIZATION 141
15 kV with a specimen current of 0.02 A. The standards used
were pure metals (Sb, Ag, Te, Cu, Au) and synthetic PbSe,
Te, ZnS, and GaAs.
O measurement on carbonates, the
conventional reaction with 100 % H
(McCrea 1950) was
used. Carbonates were, on the basis of their chemical compo-
sition, reacted at 25
C (calcite) or 100
C (rhodochrosite, do-
lomite) for 2 hours and corrections to measured
were made depending upon the chemical composition of car-
bonates and the temperature of reaction. The reproducibility
O measurements on carbonates was ±0.1 .
Preparation of SO
S measurements on sulphides
was done by combusting with CuO at 770
C in a vacuum
(Grinenko 1962). The reproducibility of
on sulphides was ±0.15 . All stable isotope measurements
were done using a Finnigan MAT 251 mass spectrometer.
Sr for the
Sr ratio measurement was isolated on
quartz columns filled with Bio Rad cation exchange resin.
Mass spectrometry was done by a Finnigan MAT 262 mass
spectrometer. A double Re filament ionization technique
was used. The measured
Sr ratios were standardized
to the value 0.1194 for
Fluid inclusions were studied utilizing doubly polished
plates, 0.20.3 mm thick, by optical microthermometry on a
Chaixmeca heating and freezing stage (Poty et al. 1976). The
stage was calibrated for temperatures between 100
C by Merck chemical standards, the melting point of
distilled water, and phase transitions in natural pure CO
Results and discussion
Sulphide minerals of ore veins and their crystal chemistry
Pivec et al. (1984) did not detect the presence of silver min-
erals proper in spite of the deposit being known as a silver
mine, even though they mentioned the content of 0.14 wt. %
Ag in the galena. New microprobe data and reflected light
microscopy studies have shown that (besides silver-bearing
tetrahedrite with 3.3 wt. % of Ag), the main silver mineral is
cubic hessite, which forms minute inclusions mainly in gale-
na and, to a lesser extent, in sphalerite. The cubic form was
identified on the basis of the isotropic behavior of hessite in
reflected light. Hessite has been known in the Bohemian
Massif in the Variscan vein mesothermal Au-deposits only
(Morávek 1992). The chemical composition of the studied
ore minerals is presented in Table 1. Pivec et al. (1984) also
reported contents of In (250300 ppm), Ga (15 ppm) and Ge
(2 ppm) in sphalerites.
The presence of color banded zones in colloform sphalerite
together with the presence of chalcedony seems to indicate
rather lower temperatures of deposition. However, the occur-
rence of cubic hessite indicates temperatures of deposition
C (Strunz 1982).
The geochemistry of hydrothermal carbonates
The chemical composition of carbonates from the main
ore vein in Roztoky was studied by Pivec et al. (1984) and
from sulfidic and barren veinlets by Kopecký et al. (1987).
On the basis of the C and O isotope data of carbonates, Ko-
pecký et al. (1987) suggest their low-temperature (late-stage
C4) hydrothermal carbonatite origin (sensu Le Bas 1977)
and connect them with a presumed hidden carbonatite intru-
sion, in the trachytic vent.
The prevailing pinkish to grey carbonate of the main ore
vein is rhodochrosite with a dolomite admixture (MnO =
39.25 wt. %). The younger carbonate filling is represented by
fine-grained calcite intergrown with dolomite (about 1:1).
This second most frequent type of carbonate gangue in the
vein, contains 9.05 wt % MgO and 43.20 wt. % CaO (bulk
analysis). Pure manganoan calcite (4.90 wt. % MnO) was
found in small amounts only. The
REE (99.8130.8 ppm)
(Table 2) as well as mildly higher SrO (1,2001,500 ppm)
and BaO (2,1508,800 ppm) (Ulrych et al. 1997), contents of
the carbonates are too low for speculation about their carbon-
atite origin (cf. Kopecký 1987a). The higher contents of Sr
and Ba in carbonates of hydrothermal veins should be inter-
preted cautiously because many carbonates from common
ore-bearing veins with no carbonatite affinity show a similar
composition to those at Roztoky. For example, the Sr content
derived from altered aluminosilicates of the host rocks in-
creases with the intensity of wall-rock alteration from old
(100 ppm Sr) to young (2,000 ppm Sr) hydrothermal carbon-
ates in ore veins of the Pøíbram ore district (Cílek et al. 1984).
The REE contents of dolomite from an ultramafic lampro-
phyre dyke (polzenite, Ralsko Hill, northern Bohemia) the
REE contents in carbonate (201 ppm) found until
now in the Bohemian Massif (Ulrych et al. 1997 are given
in Table 2 for comparison). Pure calcite phases from sövite
contain generally higher
REE, Sr and Ba contents e.g.
calcite from sövite, Kaiserstuhl:
REE 733 ppm; calcite from
REE 7511,751 ppm, Sr 7501,900, Ba
7,00014,500 ppm; dolomite from sövite, Fen:
ppm, Sr 5,0006,900 ppm, Ba 360500 ppm (Möller et al.
1980). Contents of
REE in late magmatic carbonatite prod-
ucts are even much higher. An ankeritic carbonatite with
REE 11,57013,078 ppm and ankeritic carbonatite with flu-
orite, barite and quartz with
REE 33,33664,550 ppm were
described from the Amba Dongar carbonatite, India, by
Viladkar & Dulski (1986).
Fig. 2. The schematic succesion of the hypogene vein minerals of
the Roztoky deposit. (Modified after Pivec et al. 1984).
142 PIVEC, REIN, ULRYCH, BENDL, DOBE
Carbonatites are commonly characterized by higher
amounts of incompactible elements like Sr, Ba, REE, Zr, U,
Th, Zr, Hf, Nb, Ta, P and F. High contents of these elements
were not detected either in vein carbonates or in the trachyt-
ic breccia of the diatreme in Roztoky. The chemical compo-
sition of the carbonates thus does not support the idea of
Kopecký (1987a) of their association with a hidden sövite
intrusion in deeper sections of the RVC.
C and O isotopic composition
of the hydrothermal carbonates
To corroborate the model of hidden carbonatite intrusion,
seventeen carbonate samples representing seven genetically
different types of carbonate occurrences in the RVC were an-
alyzed for carbon and oxygen isotopes by Kopecký et al.
(1987). From this sample set, only one analysis, a carbon-
atized monzodiorite xenolith from the pseudotrachyte brec-
cia, plots within the field of primary igneous carbonatites
(PIC) as defined by Taylor et al. (1967) and Deines & Gold
(1973). All other samples possess higher
ues (see Fig. 3), plotting in the field of carbonatite associat-
ed carbonates, which generally do not represent primary ig-
Numerous hydrothermal carbonates from various hydro-
thermal ore veins of the Bohemian Massif, which clearly do
not have any carbonatite affinity, plot in the same field,
some even within the PIC field (e.g. some hydrothermal car-
bonates of the West Bohemian uranium deposits, some car-
bonates of polymetallic veins in the Jihlava ore district,
etc.). This coincidence can be easily explained by the fact
that the isotopic composition of a carbonate plots in the
O space as a result of the influence of three inde-
pendent factors: (i) the
O values of the hydro-
thermal fluid; (ii) temperature of deposition; and (iii) the na-
ture of the carbon species in the fluid. When an independent
temperature estimate can be obtained most uncertainties are
eliminated since the
O characteristics of hydro-
thermal fluids can be calculated. Only in the cases where an
independent thermometry indicates magmatic temperatures
and the calculated fluid composition plots within and/or
close to the PIC, can a carbonatite affinity be assumed.
The temperature of deposition of hydrothermal carbonates
of the studied Roztoky sulphide deposit probably did not
C, because carbonate deposition postdates sul-
phide deposition, for which sphalerite-galena sulphur isoto-
pic thermometers indicate temperature in the range of 200 to
C (see below). Fluid inclusion homogenization tem-
peratures exhibit a similar range (220
New carbon and oxygen isotopic determinations on car-
bonates from the main vein of the Roztoky sulphide de-
posit have shown similar
C but lower
O values when
compared with data for sulphide-bearing veinlets reported
by Kopecký et al. (1987; see Fig. 3). If a temperature of
deposition between 200 and 280
C for the carbonates of
the main vein is accepted,
values from ca. 3.0 to
values from ca. 3 to 7
can be calculated.
Table 1: Composition of ore minerals from the Roztoky deposit
(in wt. %).
n of anal.
100.69 100.38 100.50 100.01 100.08 100.93
Number of ions per formula unit
0.994 12.982 0.012
2.000 29.000 3.000
This carbon isotopic composition of hydrothermal fluids is
within the range accepted for deep-seated carbon (5 ± 2
Ohmoto 1986) near its upper limit. Since the carbon isotopic
composition in the same range can also be produced by mixing
of different sources, adjacent contact-metamorphosed Upper
Cretaceous marlstones, representing the dominant carbon res-
ervoir in the host-rocks, were also analysed. Samples collected
in a 1100 m long profile perpendicular to the contact of monzo-
diorite segment show
C values in the range from +1.48 to
O values in the range from +15.7 to +2.8
(SMOW), see Fig. 3 in Chaloupková (1986). Carbonate phases
from contact metamorphic pyroxene and albite-epidote horn-
felses close to the contact show the lowest
ues, while the more distant, less influenced Upper Cretaceous
host rocks plot near the upper limit of the above mentioned
EPITHERMAL TERTIARY Pb-Zn-Cu (Ag, Te) MINERALIZATION 143
range. Mass balance calculation shows that the dominant por-
tion of the carbonate-carbon which was released from the host
rock sedimentary sequence as a result of decarbonation and hy-
drothermal mobilization had
C values in the range from +2
to 2 while the hydrothermal fluid which formed the gangue
of sulphidic veins ranged from 3 to 5 . This shows that im-
portant proportion of CO
in the hydrothermal fluids was de-
rived from another, probably deep-seated source.
The calculated oxygen isotopic composition of hydrother-
mal water is extremely low, indicating the dominance of low-
O water (with respect to its low to medium salinity proba-
bly groundwater from Cretaceous sediments) in the
O plot for various carbonates from the Roz-
toky volcanic center. The field of Primary Igneous Carbonatites
(PIC) is after Taylor et al. (1967) and Deines & Gold (1973) and
the field for normal Upper Cretaceous sedimentary rocks after
Hladíková et al. (1979).
Table 2: REE contets of carbonates from Roztoky ore veins, and in
ultramafic lamprophyre (polzenite), Ralsko Hill (in ppm). 1
rhodochrosite, main ore vein, Roztoky; 2 dolomite-calcite, main
ore vein, Roztoky; 3 dolomite, polzenite dike, Ralsko Hill, north-
ern Bohemia (Analyst: P. Povondra, Charles University, Prague).
hydrothermal fluid. Hydrothermal circulation also decreases
the original sedimentary
O signature of the Upper Creta-
ceous host marlstones in the whole contact aureole up to a
distance of several hundred meters from the monzodiorite in-
trusion. This significant shift in the
O of host rocks locally
down to +2.8 (SMOW) cannot be explained by decarbon-
ation reactions and requires extensive water/rock interactions
under high water/rock ratios.
Carbon and oxygen isotope study therefore shows that the
volcanic activity and especially the intrusion of the monzo-
diorite body into a shallow crustal level at Roztoky caused
extensive circulation of heated low to medium salinity low-
O fluids which formed the sulphidic veins and altered the
host rocks. An important proportion of the carbonate carbon
of the hydrothermal fluids forming the sulphidic veins had a
C composition in the deep-seated range and was not de-
rived from the Upper Cretaceous sediments.
S isotopic composition of the sulphides
Sulphur isotopic compositions of both galena and sphaler-
ite from the main vein show narrow ranges of
from 4.4 to 3.1
for galena (5 samples) and from 2.5 to
for sphalerite (5 samples). Deposition of these sul-
phides in the main vein is usually not contemporaneous. This,
together with the frequent presence of spherical structures
formed by the different colored zones of sphalerite, makes the
application of sphalerite-galena sulphur isotope thermometry
problematic. In such case the sphalerite-galena sulphur iso-
tope thermometry can yield reliable data only in environ-
ments, where the
values had minimum variability
during the period in which the minerals were precipitated.
Two pairs with the most intimate textural relationships be-
tween sphalerite and galena yielded sphalerite-galena sulphur
isotopic temperatures of 218 and 226
C (± 25
C) (using the
equation of Ohmoto & Rye 1979).
S-dominated fluids during sulphide deposi-
values in the range 1.0 to 2.0
can be cal-
culated. No exact conclusion concerning the sulphur source
can be made, because no accurate information concerning
the sulphur isotopic composition of the RVC rock and adja-
cent country rocks is available. The isotopic composition of
this source sulphur of hydrothermal fluids is slightly shifted
from the range typical for average uncontaminated mantle
(ca. 0.5 to +0.5 ; Ohmoto 1986).
Pb isotopic composition of the galena
The Pb isotopic composition of the galena from the Roz-
toky deposit was reported by Legierski (1973). Vanìèek et al.
(1985), based on small but systematic differences in lead iso-
tope ratios of some localities studied by both Legierski and
Doe & Zartman (1979), introduced correction factors to the
data of Legierski (1973) to align both data sets. Pb isotope ra-
tios reported in this paper are those of Vanìèek et al. (1985).
The lead isotopic ratios of galena from the Roztoky de-
posit are high (
Pb about 19.03,
Pb about 39.17).
144 PIVEC, REIN, ULRYCH, BENDL, DOBE
Lead with this isotopic composition can be derived direct-
ly from alkaline basic to intermediate magmatic rocks of the
RVC. Wilson et al. (1994) reported
Pb isotope ra-
tios of primitive Tertiary mafic volcanic rocks of the Èeské
støedohoøí Mts. area in the range from 19.4 to 20.0 and sug-
gested that the source of magmas is a sublithospheric
HIMU mantle plume. With respect to the well-known re-
gional enrichment of Upper Paleozoic and Upper Creta-
ceous sedimentary rocks of this region in U and Th (Lepka
1980), the lead could have been derived from this upper
crustal source as well.
Sr ratio of the hydrothermal carbonates
For the rhodochrosite of the main vein of the Roztoky de-
Sr ratio of 0.705237 ± 0.000009 (2
) and for
the calcite with dolomite admixture from the same vein, a
Sr ratio of 0.705104 ± 0.000010 (2
) were obtained.
Sr ratios of primitive basaltic volcanic rocks of
the Czech part of the Cenozoic Central European Volcanic
Province, which can be used as an estimate of the mantle ar-
ray in this region, range from 0.7031 to 0.7037 (Vokurka &
Bendl 1992; Bendl et al. 1993; Wilson et al. 1994). The
rocks of the RVC yielded slightly higher and wider initial
Sr range (0.7037 to 0.7045; Ulrych et al. in prep) indi-
cating probable minor contamination by crustal material.
For the marine Cretaceous sedimentary rocks of this region
which represent, besides the rocks of RVC, another important
reservoir of Sr, no
Sr determinations exist. The average
ratio for Turonian marine carbonate sediments can be esti-
mated at close to 0.7074 (Burke et al. 1982).
Sr ratios obtained for hydrothermal carbonates indi-
cate that the Sr content of hydrothermal fluids was most prob-
ably a mixture of Sr derived from the rocks of the RVC and of
Sr originating from local crustal rocks, probably Upper Creta-
ceous sediments. Direct carbonatite origin of studied hy-
drothermal carbonates is less probable.
Fluid inclusion study
Fluid inclusions were studied in sphalerite and rhodoch-
Sphalerite contains a large number of inclusions but the
majority are unsuitable for microthermometry due to their
opaque nature. The measured inclusions are 5 to 20
O-rich, two phase, with vapour phase between 5 and
20 vol. %. Two generations of inclusions have been distin-
guished. Probably pseudosecondary inclusions have homoge-
nization temperatures (Th) in the range of 221 to 285
Fig. 4) and melting temperatures of ice (Tm) 1.4 to 7.0
i.e. salinity of the fluid is 2.4 to 10.4 wt. % NaCl equiv. (Bod-
nar 1993). An exceptional distinct group of inclusions shows
lower Tm of ice, from 12.6 to 15.4
C, corresponding to sa-
linity from 16.5 to 18.9 wt. % NaCl equiv. The homogeniza-
tion temperature of abundant secondary inclusions are be-
tween 151 and 212
C and their salinity ranges from 1.4 to 4.6
wt. % NaCl equiv. (Tm = 0.8 to 2.8
C). The eutectic tem-
peratures of the inclusions in sphalerite were not observed
due to the dark colour of the mineral.
Abundant large, 10 to 40
m, two-phase inclusions with
vapour phase to vol. 30 % have been found in carbonate.
They occur mainly in isolated groups and are considered to
be primary. They are also water-rich, Th are in the range be-
tween 228 and 277
C and salinity from 1.5 to 10.9 wt. %
NaCl equiv. (Tm = 0.9 to 7.4
C). The eutectic tempera-
tures have values between 22.0 and 29.2
C, and indicate
that NaCl is the dominant salt of the solution.
If we take into account that the deposit was formed under
hydrostatic pressure conditions in a depth not exceeding
800 m, then the pressure correction between the Th and tem-
perature of trapping is less than 10
C (Potter 1977) and the
Th of the primary and pseudosecondary inclusions are close
to temperatures of the formation of the minerals.
In the diagram Th (homogenization temperature) versus sa-
linity (Fig. 4) three fields of fluid inclusion data can be distin-
guished. Secondary inclusions in sphalerite have distinctly
lower Th and salinity. The majority of the data of sphalerite
and carbonate lie in the same field and indicate that the hy-
drothermal fluid responsible for the formation of sphalerite
and carbonate was low-saline at a temperature below 300
The inclusions with salinity of about 17 wt. % NaCl equiv.
form a separate cluster of data and seem to be uncommon.
The geological position of the base metal deposit and its
close spatial affinity to the rock suite show that the ore veins
represent an integral part of the RVC. This conclusion is
supported by the young trachyte vein cutting both the bosto-
nite dyke and the parallel ore vein (Pivec et al. 1984).
The revision of the chemical composition of ore minerals
in the Roztoky deposit demonstrates that the silver-bearing
minerals are cubic hessite forming inclusions mainly in gale-
na and the minor silver-bearing tetrahedrite.
According to Kopecký (1987a), ore-bearing carbonate vein
material represents products of the residual solutions derived
from a hypothetical carbonatite intrusion. There are, however,
no unambiguous proofs for this interpretation. From the pa-
Fig. 4. Homogenization temperatures versus salinity of fluid inclu-
sions in sphalerite and carbonate from the main ore vein of the
EPITHERMAL TERTIARY Pb-Zn-Cu (Ag, Te) MINERALIZATION 145
rameters of the hydrothermal fluids studied, only the C isoto-
pic composition lies in the range typical for deep-seated car-
bon. The very low
O values of the hydrothermal fluids (3
to 7 vs. SMOW) indicate the dominance of meteoric wa-
ter in the ore fluid. The radiogenic lead isotope ratios of the
galena prove the upper crustal origin of the lead, outside the
rocks of the RVC. Similarly, the
Sr isotope ratios of the
hydrothermal carbonates which are slightly higher than those
of the RVC and higher than the local mantle range indicate an
admixture of Sr derived from crustal rocks.
The low REE, Sr and Ba contents of both the carbonates of
ore veins and trachytic breccia of diatreme do not indicate
their carbonatite origin. The simple ore vein character (no
cone-sheets Kopecký 1987a), dominance of sulfidic min-
erals and composition of sulphidic and carbonate minerals in
the ore veins, their textural (collomorphous) and structural
(cockarde) arrangement, lack of any silicate and scarcity of
barite and fluorite practically exclude a carbonatite affinity
for the Roztoky sulphidic ore veins.
The temperature of deposition probably reached a maxi-
mum of 200280
C during the main ore stage (presence of
cubic modification of hessite, data of sphalerite-galena sul-
phur isotopic thermometer, fluid inclusion homogenization
temperatures) with a decrease in the younger stages.
The presented data, especially the low
O values of the
hydrothermal fluids, indicate that the Roztoky sulphide de-
posit is a result of circulation in an upper crustal hydrother-
mal system in which the rocks of the RVC acted dominantly
as a heat source driving (with the support of influx of deep-
, cf. Paèes 1974) the movement of pore waters
from local Cretaceous sedimentary rocks.
Most parametres of the Roztoky deposit agree with fea-
tures of epithermal deposits defined by Pirajno (1992). It is
formed at low temperature from dominantly meteoric hy-
drothermal fluids having moderate to low salinity (in the
early stages of mineralization higher than 5 wt.% NaCl
equivalent which is supposed by Pirajno l.c. as maximum).
The deposit is volcanically hosted and clearly related to vol-
cano-plutonic activity. The present authors suggest processes
analogous to those proposed by Richards et al. (1991) for the
Porgera gold deposit, where it is supposed that the metals in
the epithermal system were derived largely from leaching of
earlier disseminated ores at depth. The presence of fine-
grained chalcedonic quartz, calcite and other carbonates,
quartz pseudomorphs and hydrothermal breccias are com-
mon features. The element association with the ore elements
such as Au, Ag, As, Sb, Te, Pb, Zn and Cu corresponds to ep-
ithermal deposits. Ore textures including open-space filling,
crustification, colloform banding and comb structures are
Acknowledgement: The research was partly funded by the
Grant Agency of the Czech Academy of Sciences, Grant
No. A 3111601. The authors would like to thank J. G. Str-
nad for review of the earlier draft of the manuscript. Special
thanks go to T. Armbrustmacher and M. Novák, who im-
proved the English considerably and to J. Hedenquist for
many helpful comments.
Baumann L., 1977: Zur Frage varistischen und postvaristischen
Mineralization in sächsischen Erzgebirge. Freiberg. Forsch. -
H., C209, 1528.
Bendl J., Vokurka K. & Sundvoll B., 1993: Strontium and neodymium
isotope study of Bohemian Basalts. Mineral. Petrol., 48, 3545.
Bodnar R.J.,1993: Revised equation and table for determining the
freezing point depression of H
O-NaCl solutions. Geochim.
Cosmochim. Acta, 57, 683684.
Burke W.H., Denison R.E., Hetherington E.A., Koepnick R.B.,
Nelson N.F. & Otto J.B., 1982: Variation of seawater
throughout Phanerozoic time. Geology, 10, 516519.
Cílek V., Proke S., kubal M., Hladíková J., mejkal V. & ák K.,
1984: Geochemistry of hydrothermal carbonates of the
Pøíbram uranium deposit. In: S. Polák & J. Litochleb (Eds.):
Vlastivedný sborník Podbrdska. Okresní archív a muzeum,
Pøíbram, 26, 79102 (in Czech).
Èadek J., Syka J., Vavøín I. & Veselý T, 1975: The conditions of
metal accummulation in sediments. Unpublished Report,
Geological Survey, Prague (in Czech).
Èadek J. & Malkovský M., 1988: Fluorite in the vicinity of Tep-
lice-Spa in Bohemia a new type of fluorite deposit. In: E.
Zachrisson (Ed.): 7th IAGOD symposium Proceedings, Lulea
Sweden., Schweizerbartsche Verlagsbuchandlang, Stuttgart,
Deines P. & Gold D.P., 1973: The isotopic composition of carbon-
atite and kimberlite carbonate and their bearing on the isotopic
composition of deep-seated carbon. Geochim. Cosmochim.
Acta, 37, 17091733.
Doe B.R. & Zartman R., 1979: Plumbotectonics I. The Phanerozo-
ic. In: H. Barnes (Ed.): Geochemistry of hydrothermal ore de-
posits. J. Wiley, New York, 270.
Gehlen von K., 1987: Formation of Pb-Zn-F-Ba mineralizations in
SW Germany: A status report. Fortschr. Miner., 65, 87113.
Grinenko V.A., 1962: Preparation of sulphur dioxide for sulphur iso-
tope analysis. Zhur. Neorgan. Chim., 7, 24782483 (in Russian).
Hanu V. & Krs M., 1963: Paleomagnetic verification of Neoidic
age of hydrothermal mineralization in Kruné hory Mts. and
Slavkovský les. Vìst. Ústø. Úst. Geol., 38, 119122 (in Czech).
Hibsch J.E., 1899: Der Doleritstock und das Vorkommen von Blei-
und Silbererzen bei Rongstock im böhmischen Mittelgebirge.
Verh. K.-kön. geol. Reichsanst., 11, 204210.
Hladíková J., Èadek J., mejkal V. & Vavøín I., 1979: Isotopic study
of oxygen and carbon in carbonates of the Bohemian Creta-
ceous Basin. Sbor. Geol. Vìd, Ø LG, 20, 3748 (in Czech).
Chaloupková M., 1986: Geochemistry of the contact of the Roz-
toky volcanic body. M.Sc. Thesis, Charles University. Praha,
190 (in Czech).
Jelínek E., Souèek J., Tvrdý J. & Ulrych J., 1989: Geochemistry and
petrology of alkaline dyke of the Roztoky volcanic centre,
Èeské støedohoøí Mountains, ÈSSR. Chem. Erde, 49, 201217.
Kopecký L., 1978: Neoidic taphrogenic evolution and young alka-
line volcanism of the Bohemian Massif. Sbor. Geol. Vìd, Ø. G,
Kopecký L., 1987a: The Roztoky pseudotrachyte caldera in the Èeské
støedohoøí Mts., Czechoslovakia. In: L. Kopecký (Ed): Proceeding
on carbonatites and alkaline rocks. Geol. Survey, Prague, 119156.
Kopecký L., 1987b: Young volcanism of the Bohemian Massif. Part 1.
Geol. Hydrometalurg. Uranu, 11, 3067 (in Czech).
Kopecký L., mejkal V. & Hladíková J., 1987: Isotopic composi-
tion and origin of carbonates in alkaline-metasomatic and
cognate rocks of the Bohemian Massif, Czechoslovakia. In:
Kopecký L. (Ed.): Proceeding on carbonatites and alkaline
Krs M. & Vondrová N., 1965: Paleomagnetic of the Neoidic miner-
146 PIVEC, REIN, ULRYCH, BENDL, DOBE
alization on the Geschieber vein in Jáchymov. Vìst. Ústø. Úst.
Geol., 40, 167173 ( in Czech).
Le Bas M.J., 1977: Carbonatite-nephelinite volcanism. J. Wiley In-
tersci. Pub., London, 1347.
Legierski J., 1973: Model ages and isotopic composition of ore
leads of the Bohemian Massif. Èas. Mineral. Geol., 18, 123.
Lepka F., 1980: Review of the average contents of U and Th in
sedimentary and magmatic rocks of the Bohemian Massif.
Geol. Hydrometalurg. Uranu, 4, 352 (in Czech).
Losert J., 1964: Tertiary and Quaternary volcanic metallogenetic
zones of central Europe, their character and deposits in
Czechoslovakia. XXII. Intern. Geol. Congres, V. Genetic
problems of ores, 405417.
Losert J. & Chrt J., 1962: Neoidic platform metalogenetic province
of the Bohemian Massif. Vìst. Ústø. Úst. Geol., 37, 210214
McCrea J.M., 1950: On the isotopic chemistry of carbonates and a
paleotemperature scale. J. Chem. Phys., 18, 849857.
Morávek P., 1992: Gold in the Bohemian Massif. Czech Geol. Sur-
vey, Praha, 1248 (in Czech).
Möller P., Morteani G. & Schley F., 1980: Discussion of REE distribution
patterns of carbonatites and alkalic rocks. Lithos, 13, 171179.
Ohmoto H., 1986: Stable isotope geochemistry of ore deposits. In:
J.W. Valley, H.P. Taylor Jr. & J.R. ONeil (Eds): Stable isotopes
in high temperature geological processes. Reviews in Mineralo-
gy , 16, 491560.
Ohmoto H. & Rye R.O., 1979: Isotopes of sulfur and carbon. In:
Barnes H.L. ( Ed.): Geochemistry of hydrothermal ore depos-
its. 2nd ed. J. Wiley, New York, 509567.
Paèes T., 1974: Springs of carbon dioxide in northwestern Bohe-
mia. Field-trip guide, Internat. Symposium on Water-Rock-In-
teraction. Academia, Prague.
Pirajno F., 1992: Hydrothermal Mineral Deposits. Springer Ver-
lag, Berlin Heidelberg, 1709.
Pivec E., Chrt J., Kapar P. & Ulrych J., 1984: Neoidic polymetal-
lic mineralization in Roztoky nad Labem. Studie ÈSAV, Aca-
demia, Praha, 10, 164 ( in Czech).
Potter R.W.II., 1977: Pressure corrections for fluid-inclusion ho-
mogenization temperatures based on the volumetric proper-
ties of the system NaCl-H
O. U.S. Geol. Survey J. Res., 5,
Poty B., Leroy J. & Jachimowicz L., 1976: Un nouvel appareil
pour la mesure des temperatures sous le microscope:
Linstallation de microthermometrie Chaixmeca. Bull. Soc.
Franc. Minéral. Cristallogr., 99, 182186.
Richards J.P., 1995: Epithermal Gold Deposits. Shortcourse 23.
Miner. Assoc. Canada, 1400.
Richard J.P., McCulloch M.T., Chappel B.E. & Kerrich R., 1991:
Sources of metals in the Porgera gold deposit, Papua New
Guinea: Evidence from alteration isotope, and noble metal
geochemistry. Geochim. Cosmochim. Acta, 55, 565580.
Strunz H., 1982: Mineralogische Tabellen. 8. Aufl. Geest & Portig
K.-G., Leipzig, 1621.
Taylor H.P., Jr., Frenchen J. & Degens E.T., 1967: Oxygen and car-
bon isotope studies of carbonatites from the Laacher district
West Germany, and Alnö district, Sweden. Geochim. Cosmo-
chim. Acta, 31, 407430.
Thomas R. & Tischendorf G., 1987: Evolution of Variscan mag-
maticmetallogenetic processes in the Erzgebirge according
to thermometric investigation. Z. Geol. Wiss., 15, 2542.
Tröger W.E., 1935: Spezielle Petrographie der Eruptivgesteine.
Ein Nomenklatur-kompendium. Verlag. Deutsch. Mineral Ge-
sell., Bonn, 1360.
Ulrych J., Pivec E., Fiala J. & Lang M., 1983: Petrology of the alkaline
subvolcanic rocks from the Roztoky area Èeské støedohoøí Mts.
Rozpr. Ès. Akad. Vìd, Ø. Mat. Pøír. Vìd., 184.
Ulrych J., Pivec E., Rutek J., Höhendorf A., Balogh K. & Bendl J.,
(in prep.): Rhyolite dike differentiates in the Roztoky intru-
sive centre, Èeské støedohoøí Mts.: Primary or secondary.
Ulrych J., Pivec E., Povondra P. & Bendl J., 1997: Geochemical
and isotope characteristic of representative carbonates in
young alkaline volcanites from northern Bohemia. J. Czech
Geol. Soc., 42, 2632.
Vanìèek M., Patoèka F., Pomourný K. & Rajlich P., 1985: The use
of isotopic composition of ore lead in metallogenic analysis
of the Bohemian Massif. Rozpr. Ès. Akad. Vìd, Ø. Mat. Pøír.
Vìd, 95, 1114.
Viladkar S.G. & Dulski P., 1986: Rare earth element abundances in
carbonatites, alkaline rocks and fenites of the Amba Dongar
complex, Gujarat, India. Neu. Jb. Mineral. Mh., 3748.
Vokurka K. & Bendl J., 1992: Sr isotope geochemistry of Cenozoic
basalts from Bohemia and Moravia. Chem. Erde, 52, 179187.
Wilson M., Rosenbaum J.R. & Ulrych J., 1994: Cenozoic magma-
tism of the Ohøe rift, Czech Republic: Geochemical and man-
tle dynamics. Abstr. Internat. Volcanolog. Congress IAVCEI,
Ankara 1994, 1.
ák K., Èadek J., Dobe P., mejkal V., Reichmann F., Vokurka K.
& Sandstat J.S., 1990: Vein barite mineralization of the Bohe-
mian Massif: sulfur, oxygen and strontium isotope and fluid
inclusion characteristics and their genetic implications. Pro-
ceedings of the symposium on barite and barite deposits.
Geological Survey, Prague, 3549.