GeolCarp_Vol56_No6_493

GEOLOGICA CARPATHICA, DECEMBER 2005, 56, 6, 493—502

www.geologicacarpathica.sk

Th-U-Pb dating of monazite from the Cretaceous uranium

vein mineralization in the Permian rocks of the Western

Carpathians

IGOR ROJKOVIČ

and PATRIK KONEČNÝ

Faculty of Natural Sciences, Comenius University, Mlynská dolina, 842 15 Bratislava, Slovak Republic; rojkovic@fns.uniba.sk

Geological Survey of Slovak Republic, Mlynská dolina 1, 817 04 Bratislava, Slovak Republic; konecnyp@gssr.sk

(Manuscript received December 1, 2004; accepted in revised form June 16, 2005)

Abstract: Th-U-Pb dating of monazite confirms the Permian age 278 ± 11 Ma of rhyolite tuff in the Northern
Gemericum. This rock was a protolith for stratiform U-Mo mineralization formed during the Late Permian by ground
water. The Permian formations and stratiform mineralization are cut by younger vein and stockwork mineralization
near Novoveská Huta and Krompachy. The quartz vein with uranium mineralization in Krompachy is accompanied
by albite, rutile, sulphides, xenotime-(Y) and rare monazite-(Ce). Th-U-Pb dating of the vein monazite gives the
Cretaceous age 124 ± 10 Ma of remobilized vein uranium mineralization.

Key words: Gemericum, age, vein mineralization, electron microprobe monazite dating, rhyolite tuff.

Introduction

Monazite, a REE phosphate commonly occurs in acid mag-
matic and metamorphic rocks. Occurrence of monazite in
veins can explain hydrothermal processes. Hydrothermal
vein mineralization in the Slovenské rudohorie Mts has
long been discussed with regard to possible Hercynian and
Alpine origin. The aim of this study was dating of monazite
associated with uranium mineralization in this area.

The initial Th and U decay produce radiogenic Pb. On

assumption that all Pb is only of radiogenic origin and the
Th-U-Pb equilibrium was not disturbed by some geologi-
cal event, the present concentration of Pb in the monazite
is proportional to the age of radiogenic decay. The new
generation of microprobes released in the last decade al-
lows more precise measuring of low concentration of Pb in
monazite. The first experience with monazite dating and
formulation of the Th-U-Pb age calculations were brought
by Parrish (1990), Suzuki & Adachi (1991, 1994), Suzuki
et al. (1994) and Montel et al. (1996). Refinement of mea-
surement conditions, correction of peak overlapping be-
tween Th-U-Pb-Y described in Suzuki & Adachi (1998),
Fialin et al. (1999), Scherer et al. (2000), Pyle et al. (2002),
Nagy (2003), Cocherie & Albarede (2001) led to overall
improvement of monazite dating. The results of monazite
dating can be found in a growing number of papers such
as Cocherie et al. (1998), Suzuki & Adachi (1998), Finger
& Broska (1999), Williams et al. (1999), Nagy et al.
(2002), Finger et al. (2003), Kohn & Malloy (2004).

Geological setting

The Western Carpathians are divided from north to

south into Outer, Central (CWC) and Inner Western Car-

pathians. The CWC consist of the following belts: Pieniny
Klippen Belt, Tatra-Fatra Belt of core mountains, Vepor
Belt and Gemer Belt in the south (Plašienka et al. 1997).
The basement of the Gemericum sheet is composed of the
Lower Paleozoic metasediments and metavolcanics cut by
intrusions of small bodies of the Permian granites. This
basement is structurally closely confined to Late Paleozo-
ic volcano—sedimentary succession. The northern Gemeric
Carboniferous rocks are represented by the Dobšiná Group
(Vozárová & Vozár 1988).

The Krompachy Group represents the Permian rocks of

the northern Gemeric Unit (Bajaník et al. 1981).
The thickness of the Permian rocks near Novoveská Huta
is variable up to 2.5 km (Novotný & Mihá 1987). The
sediments represent mesocycles of a continental character
with the appearance of lagoonal lithofacies in the upper-
most part. Three formations were distinguished (Bajaník et
al. 1981):

1. the Knola Formation – coarse detritic sediments,
2. the Petrova Hora Formation – volcano-sedimentary

rocks,

3. the Novoveská Huta Formation – fine clastic sedi-

ments with evaporites.

The sedimentary rocks of the Knola Formation are repre-

sented by red polymict conglomerate, sandstone and aleu-
rolite formed in fanglomeratic, fluvial and limnic
lithofacies (Rojkovič et al. 1993).

Volcano-sedimentary rocks of the Petrova Hora Forma-

tion are represented by polymict to monomict conglomer-
ate, sandstone, aleurolite, tuffite, tuff and volcanics.
Sedimentary and volcanic rocks were formed in the conti-
nental environment. Rhyolite, dacite and andesite are ac-
companied by volcanoclastics.

Andesite and dacite can be seen in the whole belt of the

Permian rocks, but they are more abundant in area of Krom-

494

ROJKOVIČ and KONEČNÝ

pachy and Jahodná near Košice. The volcanic rocks are
overlain by thick sequence of violet and green volcano-
clastics forming carbonatized sericite-chlorite and
quartz-sericite-chlorite shales. They are overlain by
bombs and lapilli tuffs, especially in Krompachy area.
Towards the south, epiclastics are more abundant and
the rocks gain the character of tuffitic conglomerate
(Rojkovič & Mihá 1991).

Acid volcanic and volcanoclastic rocks overlying

the andesite and dacite are abundant mainly in Petrova
Hora. They are represented mostly by psammitic tuffs,
ignimbrite and less by rhyolite. They are light green to
light grey moderately schistose rocks. Fragments or
phenocrysts are represented by quartz with magmatic
corrosion, potassium feldspar, plagioclase, biotite and
pseudomorphs of sericite after feldspars. Matrix with
dominant quartz is microgranoblastic or lepidoblastic if
sericite is more abundant. Ignimbrite shows typical tex-
tures with plastic deformation of glass fragments now
recrystallized. Zircon and tourmaline are frequent,
while monazite-(Ce), titanite and garnet are rare acces-
sory minerals.

The uppermost formation of the Krompachy Group is

the Novoveská Huta Formation, representing a com-
plete sedimentary mesocycle. The sediments are finer
upwards from basal polymict conglomerate through
sandstone to shale with evaporite horizons containing
carbonates, sulphates and halite. Sediments belong to
fanglomerate-fluvial facies, limnic facies up to products
of sea ingression with sulphates and halite.

All tectonic elements are Alpine, with prevalence of

northern vergency, and they form a uniform fold and
fault style of the regional structure (Rojkovič et al.
1993).

U-Mo mineralization is bound to the Petrova Hora

Formation in the whole Permian belt in the northern Ge-
mericum from Dobšiná in the west to Košice eastward.
The most important uranium mineralization occurs near
Novoveská Huta. Several occurrences of uranium min-
eralization of similar character as in Novoveská Huta
occur near Krompachy and Petrova Hora. Important ura-
nium deposit occurs in the eastern margin of this Permi-
an belt near Košice. Uranium deposits form mostly
stratiform (lenticular) and peneconcordant bodies in
sandstones and conglomerates with volcanoclastic ma-
terial and also directly in volcanic rocks.

The most important uranium mineralization in No-

voveská Huta area occurs in two horizons of the Petrova
Hora Formation. Ore bodies form lenses mostly concor-
dant to wall rocks. Planes concordant to the Alpine cleav-
age are also locally mineralized. The length of the lower
mineralized horizon is 4 km, the width varies from 200 to
600 m and the thickness reaches up to 80 meters. Lenticu-
lar ore bodies are several meters to tens of meters thick and
their area extends from tens to tens of thousands of square
meters. Intensive silicification, sericitization, carbonatiza-
tion, pyritization and increased apatite and tourmaline
contents characterize mineralized rocks. Uranium mineral-
ization is disseminated or forms veinlets.

Uraninite and molybdenite are dominant in the U-Mo

ores of both main horizons. They are accompanied by
U-Ti oxides, pyrite, apatite, chalcopyrite, tennantite, ga-
lena, sphalerite, arsenopyrite, ilmenite, rutile, leucoxene,
magnetite, hematite, covellite, marcasite, pyrrhotite, bou-
langerite, xenotime-(Y), monazite-(Ce), goethite, autunite
and torbernite (Rojkovič 1968, 1997). Primary stratiform
uranium mineralization was mostly formed at 100 to
150 °C according to the homogenization temperatures of
fluid inclusions. Fluid concentration reached 27 to 33
equiv. wt. % NaCl. Remobilized U-Mo mineralization was
formed at temperatures ranging from 320 to 240 °C with
maximum at 250 °C. Fluid inclusions suggest the pres-
ence of Mg, K, Na, Cl in fluids and fluid concentration
10 to 15 equiv. wt. % NaCl. The P-T parameters of the
Alpine metamorphic overprint of the Lower Paleozoic
rocks of Gemericum were estimated to 330—350 °C and
0.5—0.6 GPa. The metamorphism of the Permian rocks
was estimated to 270—300 °C and 0.3—0.4 GPa (Faryad
& Dianiška 1999).

The stratiform uranium mineralization is cut by young-

er high-grade mineralization. High-grade uranium miner-
alization rarely occurs in faults and schistosity planes
cutting the U-Mo mineralized horizons in the western
part of the Novoveská Huta deposit. Mineralization has a
disseminated, stockwork character containing fragments
of the ore-bearing horizons in the faults. Fault-related ore
0.1 to 2 m thick is situated some hundreds of meters from
its trans-section with the ore bearing horizons. Uranium
and molybdenum mineralization is represented by ura-
ninite, coffinite and molybdenite. Chalcopyrite, tennan-
tite, pyrite, galena, U-Ti oxides, montroseite, marcasite,
sphalerite, clausthalite, graphite, quartz and Fe-dolomite
are accompanying minerals.

Uranium mineralization occurs southwest from Krom-

pachy (Fig. 1), south of Jarček stream. Veinlets of quartz
several centimeters thick cut green sandstone of the No-
voveská Huta Formation. X-ray amorphous U-Ti oxides
are abundant in quartz veinlets accompanied by albite,
less by carbonate, columnar crystals of rutile, galena, py-
rite, chalcopyrite, xenotime-(Y) and rare monazite-(Ce)
(Rojkovič & Mihá 1991). Mineralization is accompanied
by red coloured alteration of sandstone due to hematite
pigment.

Carbon and sulphur isotopic composition display the

larger variabilities in stratiform U-Mo ores than in quartz-
carbonate veins with Cu mineralization.

S and

values vary in stratiform U-Mo ores from —32.7 to +2 .7 ‰
and from —27.1 to —0.5 ‰, respectively. The wide range of
the isotopic composition of C and S may be explained by
mixing of ore forming fluids derived from sedimentary
rocks with possible fluids of volcanic origin and by
their complex history (metamorphism and remobilization)
(Rojkovič 1997).

C values around —21 ‰ propose a

biogenic origin. Negative

S values may suggest bacte-

rial reduction or they are the result of partial isotopic
equilibration of hydrogen sulphide of volcanic origin with
sulphates derived from overlaying evaporites. The relative-
ly narrower ranges of

S and

C values from —18.8

495

Th-U-Pb DATING OF MONAZITE IN THE PERMIAN ROCKS OF THE WESTERN CARPATHIANS

to —4.6 and from —6.3 to —2.5 ‰, respectively,

in quartz-car-

bonate veins with copper mineralization suggest a deeper ho-
mogenized hydrothermal source of ore-bearing solutions
(Rojkovič et al. 1993). The prevalence of uranogene Pb is
typical for the stratiform U-Mo mineralization, whereas
thorogene

208

Pb is characteristic of quartz-carbonate veins

with copper mineralization (Zhukov & Rojkovič 1982).

Quartz-carbonate veins with copper mineralization were

formed later. The veins cut older stratiform U-Mo mineral-
ization. The older generation of the veins is represented in
places by siderite—sulphide mineralization. The younger
stage is represented by dominant Fe-dolomite and chal-
copyrite. Copper mineralization in the studied rocks is
represented by chalcopyrite and tennantite accompanied
by carbonates (mostly Fe-dolomite), quartz, pyrite, galena,
sphalerite, arsenopyrite, marcasite, boulangerite, claust-
halite, cinnabar, barite and tourmaline. Younger uraninite
occurs rarely. Quartz accompanying chalcopyrite displays
homogenization temperatures of fluid inclusions from 150
to 230 °C with maximum 180 to 190 °C and corresponds
to composition of CaCl

—NaCl—H

O and fluid concen-

tration ranging from 20.6 to 22.6 equiv. wt. % NaCl. The
less frequent solid phase is represented by carbonate.
Quartz of the third stage of hydrothermal vein mineral-
ization in Novoveská Huta gives T

hom

from 120 to

190 °C, 7.1 equiv. wt. % NaCl and Fe-dolomite of the
fifth stage gives T

hom

from 95 to 130 °C and 17.2 equiv.

wt. % NaCl (Rojkovič et al. 1993). Pb isotopic analysis
in galena of quartz-carbonate veins with copper miner-
alization gave a model age of lead 110 Ma (Háber &
Rojkovič 1989, according to Stacey & Kramers 1975).

Methods

Minerals were studied by polarizing microscope in

both transmitted and in reflected light and by scanning
electron microscope (SEM). They were analysed by
wave-dispersion X-ray microanalysis (WDX) and by
X-ray diffraction analysis (XRD). Microprobe analyses
(WDX) were performed with CAMECA SX100 in the De-
partment of Electron Microanalysis at Geological Survey
of Slovak Republic in Bratislava under the following
conditions: accelerating voltage 15 kV, beam current 20 nA
and beam diameter of about 1—5

µm. The obtained counts

were recalculated in oxides using the PAP correction. Natural
and synthetic standards were applied on calibration of the
microprobe: Al—Al

, Si—SiO

, P—apatite, Ca—wollasto-

nite, Y—YPO

, La—LaPO

, Ce—CePO

, Gd—GdPO

Yb—YbPO

, Sm—SmPO

, Pr—PrPO

, Er—ErPO

, Nd—NdPO

Lu—LuPO

, Ho—HoPO

, Dy—DyPO

, Tb—TbPO

, Pb—PbS,

U—UO

and Th—ThO

Microprobe analyses of monazites were performed

under different conditions. To obtain suitable counting
statistics for measurement of low lead concentration as
well as very precise measurement of U, Th and Y count-
ing times 70—130 s and the beam current 100—130 nA
were used. Measurement conditions and age calcula-
tions were described in more detail by Konečný et al.
(2004). Th-U-Pb ages were recalculated after Montel et
al. (1996) by MONDAT program (P. Konečný). The re-
sulting age of each sample was calculated as the
weighted average of individual ages, its errors are given
on 95 % confidence level (2

σ).

Fig. 1. Geological map of the eastern part of the Slovenské rudohorie Mts (adapted according to Biely et al. 1996). 1 – Tertiary sedi-
ments, 2 – Neogene volcanic rocks, 3 – Mesozoic rocks, 4—6 – Gemericum: 4 – granite, 5 – Upper Paleozoic rocks, 6 – Lower Pale-
ozoic rocks, 7 – Paleozoic and Proterozoic? rocks of Veporicum, 8 – studied mineralization at NH – Novoveská Huta, Kr – Krompachy.

496

ROJKOVIČ and KONEČNÝ

Table 1: Chemical composition of monazite in Novoveská Huta in weight %.

Sample NH-847/569.5

No 1 2 3 4 5 6 7 8 9 10

0.74

0.88

0.50

0.56

0.82

0.81

0.94

0.53

0.69

0.57

0.82

16.87

15.54

17.24

16.81

16.83

16.06

16.22

16.07

17.51

16.86

17.71

16.43

31.31

30.48

31.12

30.88

30.67

31.19

30.87

31.12

31.21

31.37

31.26

31.07

3.08

3.33

3.15

3.11

3.02

3.14

3.19

3.33

3.22

3.09

3.13

3.29

11.03

11.09

10.62

10.66

11.16

11.58

11.18

11.50

10.64

11.08

10.50

11.30

1.33

1.43

1.14

1.32

1.22

1.45

1.60

1.31

1.18

1.24

1.16

1.49

1.00

1.08

0.85

0.92

0.76

1.09

0.97

0.96

0.80

0.98

0.77

1.00

0.00

0.07

0.00

0.08

0.05

0.08

0.00

0.04

0.00

0.08

0.01

0.13

0.30

0.19

0.17

0.09

0.28

0.16

0.29

0.22

0.15

0.02

0.20

0.35

0.29

0.23

0.44

0.49

0.02

0.62

0.49

0.23

0.18

0.64

0.43

0.29

0.00

0.10

0.00

0.05

0.13

0.00

0.16

0.00

0.02

0.06

0.00

0.08

0.13

0.08

0.04

0.00

0.07

0.03

0.10

0.00

0.13

0.03

0.00

0.17

0.04

0.00

PbO

0.07

0.08

0.06

0.08

0.07

0.08

0.07

0.06

0.05

0.08

0.05

0.04

0.01

0.02

0.06

0.04

0.06

0.05

ThO

4.95

5.32

5.30

6.02

6.06

4.30

4.70

4.45

5.60

4.25

5.44

4.78

0.00

SiO

1.04

1.08

1.35

1.41

1.42

0.85

0.92

0.80

1.35

0.91

1.34

0.98

CaO

0.28

0.34

0.17

0.29

0.32

0.34

0.18

0.27

0.17

0.32

27.44

27.25

26.90

26.98

26.78

27.76

27.35

27.82

26.66

27.76

27.11

26.95

Total

99.73

98.66

99.25

99.56

99.11

99.58

98.89

99.39

99.26

99.38

99.95

99.18

Cations on the basis of 4 O

0.016

0.019

0.011

0.012

0.018

0.017

0.020

0.012

0.015

0.012

0.018

0.250

0.233

0.258

0.251

0.252

0.238

0.242

0.238

0.263

0.250

0.263

0.246

0.461

0.453

0.462

0.457

0.456

0.458

0.465

0.462

0.461

0.462

0.045

0.049

0.047

0.046

0.045

0.046

0.047

0.049

0.048

0.045

0.046

0.049

0.158

0.161

0.154

0.162

0.166

0.162

0.165

0.155

0.159

0.151

0.164

0.018

0.020

0.016

0.018

0.017

0.020

0.022

0.018

0.017

0.016

0.021

0.013

0.015

0.011

0.012

0.010

0.014

0.013

0.011

0.013

0.010

0.013

0.000

0.001

0.000

0.001

0.000

0.001

0.000

0.001

0.000

0.002

0.004

0.002

0.001

0.004

0.002

0.004

0.003

0.002

0.000

0.003

0.005

0.004

0.003

0.006

0.000

0.008

0.006

0.003

0.002

0.008

0.006

0.004

0.000

0.001

0.000

0.001

0.002

0.000

0.002

0.000

0.001

0.000

0.001

0.002

0.001

0.000

0.001

0.000

0.001

0.000

0.002

0.000

0.002

0.001

0.000

0.001

0.000

0.001

0.000

0.001

0.000

0.001

0.000

0.001

0.000

0.045

0.049

0.055

0.056

0.039

0.043

0.041

0.052

0.039

0.050

0.044

0.000

0.042

0.044

0.055

0.057

0.058

0.034

0.037

0.032

0.055

0.036

0.054

0.040

0.012

0.015

0.007

0.012

0.014

0.015

0.008

0.011

0.007

0.014

0.935

0.936

0.925

0.923

0.922

0.943

0.937

0.946

0.919

0.944

0.925

0.928

Total

2.025

2.024

2.022

2.024

2.027

2.023

2.026

2.022

2.023

2.032

Fig. 2. Analysed monazite grains (mon), zircon (zir) with thin xe-
notime rim (xen) and biotite (bt) in rhyolite tuff, Novoveská Huta,
SEM—BEI.

Monazite occurrence

Monazite

Ce[PO

] was found in two rock samples.

Psammitic rhyolite tuff which was taken from drilling
core No. 847 of Uranium Survey in 569.5 m overlying
rhyolite in 583 m. Three monazite grains (up to 50 mm in
diameter) are enclosed in biotite (Fig. 2). Scanning elec-
tron microscopy in back-scattered electron image does
not show any zonality or inherited cores. No alteration of
monazite was observed. Monazite is accompanied in bi-
otite by zircon and apatite. Chemical composition shows
Th content up to 6 wt. % (Table 1).

In quartz veins near Krompachy monazite occurs in vein-

lets accompanied by xenotime-(Y) (Fig. 3). Monazite aggre-
gate 120

×20 µm with homogeneous grains (up to 20 µm)

without zonality (Fig. 4) was analysed. Chemical composi-
tion shows ThO

content up to 8 wt. % (Table 2). Analysed

grains from both occurrences correspond to monazite
(Fig. 5). Monazite from Novoveská Huta is closely bound

497

Th-U-Pb DATING OF MONAZITE IN THE PERMIAN ROCKS OF THE WESTERN CARPATHIANS

Table 2: Chemical composition of monazite in Krompachy in weight %.

Sample Kr

No 13 14 15 16 17 18 19 20
Y

0.31

0.44

0.50

0.22

0.26

0.51

0.36

0.71

3.40

3.00

3.08

3.70

3.69

2.46

3.05

2.70

27.31

26.27

26.21

28.03

27.87

24.02

26.79

24.17

4.49

4.60

4.65

4.47

4.26

4.61

5.13

4.90

19.06

20.85

20.80

18.20

18.42

22.30

22.67

21.81

4.55

5.16

5.10

3.84

3.99

6.17

5.41

6.35

2.37

3.02

3.12

2.09

2.24

3.66

3.08

4.05

0.03

0.01

0.07

0.03

0.08

0.10

0.00

0.19

0.28

0.55

0.45

0.14

0.34

0.68

0.31

0.53

0.65

0.00

0.30

0.16

0.39

0.01

0.26

0.03

0.04

0.16

0.07

0.02

0.17

0.16

0.00

0.09

0.01

0.10

0.00

0.03

0.19

0.12

0.00

PbO

0.05

0.03

0.05

0.04

0.06

0.03

0.08

0.09

0.25

0.11

0.16

0.13

0.09

0.31

ThO

6.96

4.82

4.61

7.85

7.92

4.81

2.88

4.27

0.00

SiO

0.34

0.22

0.44

0.43

0.22

0.23

0.19

CaO

1.02

0.73

0.70

1.15

1.18

0.87

0.56

0.78

27.88

28.71

28.45

27.85

28.10

28.52

28.36

28.91

Total

98.64

98.33

98.43

98.12

99.35

99.11

98.98

99.59

Cations on the basis of 4 O

0.007

0.009

0.011

0.005

0.006

0.011

0.008

0.015

0.050

0.044

0.045

0.055

0.054

0.036

0.045

0.039

0.402

0.382

0.383

0.414

0.408

0.348

0.390

0.346

0.066

0.067

0.068

0.066

0.062

0.066

0.074

0.070

0.274

0.296

0.262

0.263

0.315

0.322

0.305

0.063

0.071

0.070

0.054

0.055

0.084

0.074

0.086

0.032

0.040

0.041

0.028

0.030

0.048

0.041

0.053

0.000

0.001

0.000

0.001

0.000

0.002

0.004

0.007

0.006

0.002

0.004

0.009

0.004

0.007

0.008

0.000

0.004

0.002

0.005

0.000

0.003

0.000

0.002

0.001

0.000

0.002

0.000

0.001

0.000

0.001

0.000

0.002

0.001

0.000

0.001

0.000

0.001

0.000

0.001

0.002

0.001

0.003

0.064

0.044

0.042

0.072

0.043

0.026

0.038

0.000

0.013

0.009

0.018

0.017

0.009

0.007

0.044

0.031

0.030

0.050

0.051

0.037

0.024

0.033

0.949

0.966

0.960

0.952

0.950

0.955

0.954

0.958

Total

2.044

2.039

2.042

2.036

2.038

2.053

2.051

Fig. 3. Aggregate of U-Ti oxide (U-Ti) is cut by quartz veinlet (qz) with
monazite (mon) and xenotime (xen). Veinlet is rimmed by alteration
products of U-Ti oxide (a.p.) represented by Ti-oxide, Fe-hydroxide and
secondary uranium minerals. Reflected light, parallel nicols.

Fig. 4. U-Ti oxide (U-Ti) with veinlet of xenotime (xen) and anal-
ysed monazite (mon) rimmed by alteration products of U-Ti oxide
(a.p.). SEM—BEI.

498

ROJKOVIČ and KONEČNÝ

Fig. 5. Diagram of monazite composition from Novoveská Huta
and Krompachy.

to the huttonite line, while monazite from Krompachy
is slightly shifted towards the brabantite line (Fig. 6).
Th-U-Pb dating of monazite from Novoveská Huta gave
278±10.2 Ma (Table 3, Fig. 7) and Th-U-Pb dating of
vein monazite associated with uranium mineralization
in Krompachy gave 124±10.2 Ma (Table 3, Fig. 8).

Associated minerals

Several phases associated with monazite were distin-

guished by polarizing microscope, scanning electron
microscope, wave-dispersion X-ray microanalysis and
by X-ray diffraction.

U-Ti oxides

Relatively homogeneous aggregates in polarizing and

electron microscope. They are distinctly darker in reflect-
ed light than enclosed rutile. They are dominant in the
Krompachy locality, where aggregates up to 2 cm were
found. It is accompanied by quartz gangue and encloses
columnar rutile and galena. It is cut by veinlets of younger
quartz accompanied by xenotime-(Y) and monazite-(Ce).
Xenomorphic U-Ti oxide is close to the chemical compo-
sition of UTi

– brannerite (Table 4). X-ray diffraction

of UTi

from Krompachy as well as electron X-ray dif-

fraction from Novoveská Huta confirmed the amorphous-
ness of the material. This is not a proof of metamictization
process, but it also excludes a presence of polymineral
crystalline aggregate of rutile (or other Ti-oxide) and ura-
ninite. U-Ti oxides are replaced by fine-grained often
zoned alteration products represented by Ti-oxides, iron
hydroxides and secondary uranium minerals.

Rutile

TiO

is grey with a brownish tint and abundant yel-

lowish brown internal reflection in reflected light. Rutile ex-
hibits bireflection and strong anisotropy (light grey-dark
violet brown). Rutile forms elongated grains (from 10 to
50 µm long), columns (from 0.02 to 0.2 mm long) and irregu-

Fig. 6. (REE + Y + P) vs. (Th + U + Si) plot of analysed monazite.

Fig. 7. Pb vs. Th* plots of monazite in rhyolite metatuff with isoch-
rons from 100 to 300 Ma and with regression line fitted by least
squares method. Near zero intersection of isochron is indicated by
equation. Th* includes measured Th plus Th equivalent of measured
U according to equation Th* = Th + 3.15 U (Nagy et al. 2002).

Fig. 8. Pb vs. Th* plots with isochrons and regression line as in
Fig. 7 of monazite in quartz vein with uranium mineralization.

499

Th-U-Pb DATING OF MONAZITE IN THE PERMIAN ROCKS OF THE WESTERN CARPATHIANS

Table 3: Monazite dating. Th, U, Pb and Y concentrations in monazite in weight %. Ages (T) calculated after model of Montel et al.

(1996). NH Novoveská Huta, Kr Krompachy.

Sample

2ó

(wt. %)

T (Ma)

2ó

(Ma)

NH-847/569.5

4.3490

0.0811

0.0703

0.0071

0.5822

275

± 35.2

NH-847/569.5 v

4.6757

0.0835

0.0858

0.0071

0.6936

321

± 32.3

NH-847/569.5 v

4.6542

0.0786

0.0815

0.0071

0.3937

322

± 32.8

NH-847/569.5

5.2879

0.1115

0.0774

0.0071

0.4423

261

± 28.6

NH-847/569.5

5.3285

0.0803

0.0826

0.0071

0.4397

285

± 29.1

NH-847/569.5

3.7779

0.0663

0.0651

0.0071

0.6487

283

± 40.3

NH-847/569.5

4.1341

0.0388

0.0640

0.0071

0.6395

260

± 38.0

NH-847/569.5

3.9130

0.0461

0.0659

0.0071

0.7395

276

± 39.4

NH-847/569.5

4.9228

0.0873

0.0783

0.0072

0.4207

288

± 30.9

NH-847/569.5 v

3.7374

0.0585

0.0700

0.0070

0.5403

324

± 40.8

NH-847/569.5

4.7835

0.0866

0.0752

0.0072

0.4519

280

± 31.9

NH-847/569.5

4.2024

0.0751

0.0730

0.0071

0.6459

295

± 36.1

Kr-6-114

6.1185

0.1131

0.0495

0.0071

0.2445

138

± 25.1

Kr-6-114

4.2315

0.1084

0.0351

0.0070

0.3435

117

± 35.2

Kr-6-114

4.0534

0.2493

0.0451

0.0070

0.3895

155

± 32.8

Kr-6-114

6.8973

0.1477

0.0424

0.0071

0.1711

102

± 22.0

Kr-6-114

6.9639

0.1904

0.0590

0.0072

0.2062

148

± 21.8

Kr-6-114

4.2225

0.1446

0.0331

0.0070

0.4009

101

± 34.2

Kr-6-114

2.5322

0.0942

0.0276

0.0070

0.2826

135

± 56.0

Kr-6-114

3.7482

0.3019

0.0318

0.0070

0.5587

± 34.0

Resulting age

NH-847/569

278±11.2 Ma

Kr-6

124±10.2 Ma

lar grains (mostly from 5 to 50 µm in size). WDX and EDX

analyses show a homogeneous distribution of iron and also in-

creased contents of niobium in rutile from Krompachy (Table 5).

Table 4: Chemical composition of U-Ti oxides in Krompachy in

weight %.

Sample

Kr6b

Kr12a

Kr12b

SiO

0.97

0.79

0.86

0.85

TiO

34.84

33.97

33.91

33.96

ThO

4.42

6.64

4.30

3.69

49.91

49.68

50.44

51.29

1.14

1.64

2.34

1.59

0.57

0.17

0.25

0.43

0.04

0.00

0.01

0.33

0.00

0.41

0.00

CaO

1.67

1.68

PbO

0.88

0.56

0.53

0.64

Total

94.85

95.12

94.31

94.46

Cations on the basis of 6 O

0.071

0.058

0.063

1.904

1.875

1.868

1.877

0.073

0.111

0.072

0.062

0.807

0.812

0.822

0.839

0.062

0.091

0.129

0.088

0.022

0.007

0.010

0.017

0.002

0.000

0.013

0.000

0.011

0.000

0.130

0.131

0.132

0.017

0.011

0.013

Total

3.098

3.096

3.106

3.102

Table 5: Chemical composition of rutile in Krompachy in weight %.

Sample

Kr6b

Kr12b

Kr6a

TiO

93.85

90.65

89.86

89.57

ThO

0.00

0.02

0.00

0.04

0.01

0.14

2.27

2.75

3.10

1.86

4.62

5.05

4.86

Total

97.98

97.58

97.69

97.67

Cations on the basis of 2 O

0.973

0.957

0.951

0.949

0.000

0.024

0.029

0.033

0.013

0.033

0.037

0.035

Total

1.009

1.014

1.016

1.017

Xenotime Y[PO

] occurs in quartz veinlets around

0.1 mm thick cutting homogeneous U-Ti oxide (Fig. 4).

Xenotime forms thin rims around accessory zircon in the

Permian rhyolite tuff in Novoveská Huta (Fig. 2). Clusters

and veinlets of xenotime-(Y) are abundant in other occur-

rences of the mineralized Permian rocks.

Heavy rare earth elements (HREE) from Gd to Yb are

also present in the xenotime besides the dominant Y

and P due to their close ionic radii to Y (Table 6). It

contains higher uranium and lower thorium contents

compared to monazite. Zonality of xenotime-(Y) re-

flects variability of radioactive elements and rare earth

elements contents.

Galena PbS forms admixtures up to 0.05 mm in size en-

closed in U-Ti oxides. Its identification was confirmed by

WDS chemical composition corresponding to Pb

0.99

1.01

500

ROJKOVIČ and KONEČNÝ

Quartz and albite (Table 7) represent dominant gangue

minerals.

Discussion

Uranium mineralization in the Permian sequences of the

Gemericum of the Western Carpathians is related to the Per-
mian acid volcanic and volcanoclastic rocks. Acid volca-
nites and their tuffs are the potential “protoliths” of U, Mo,
Cu and associated elements accumulations. The new results
of Th-U-Pb dating of monazite confirm the age of monazite
in the Permian tuff of rhyolite from Novoveská Huta (drill-
ing hole 847, 569.5 m) 278± 11.2 Ma. U-Pb dating of zir-
cons in metarhyodacite from Čierny Balog and Bacúch
(Slovakia) shows ages of 278± 11 and 255± 2 Ma (Ko-
tov et al. 1996). The Permian age of zircon 284± 3 Ma is
also known from metavolcanics of “Porphyrmaterialschief-
er” from the Tauernfenster in Austria (Söllner et al. 1991).

A substantial part of uranium in the non-mineralized

volcanic rocks and their tuffs is bound to the matrix, but

Table 6: Chemical composition of xenotime in Krompachy in weight %.

its distribution is irregular. Irregular distribution is docu-
mented by histograms of uranium content and by fission
tracks (Rojkovič et al. 1991). Low-grade ores were formed
during diagenesis after uranium release from devitrificated
tuffs and tuffitic rocks. Stratiform mineralization started
during the Upper Permian shortly after deposition and
burial by overlying sediments within aquiferous horizons
of permeable rocks. Ground water in oxidic and acid con-
ditions took part in leaching and transport of U. Accumu-
lations of pyrite, uraninite, Mo and Cu sulphides were
formed, due to mixing of oxidative meteoric solutions
with solutions derived from reducing hot springs (H

S),

and partly with organic matter. U-Pb isotopic dating of
the low-grade stratiform uranium mineralization gave
240± 30 Ma in Novoveská Huta (Arapov et al. 1984). Sim-
ilar ages of uranium mineralization were found in the Per-
mian rocks of the Alps. Uranium mineralization near Val
Vedello in Italy gives from 249 to 240 Ma (Cadel et al.
1987). U-Pb discordia dating of uranium mineralization
from Valais in Switzerland indicates the primary age of
crystallization around 255 Ma (Eikenberg et al. 1989).

Sample Kr

1 2 3 4 5 6 7

36.59

35.78

36.38

37.81

39.00

38.70

36.47

0.07

0.00

0.18

0.01

0.48

0.63

0.15

0.12

0.17

0.32

0.62

1.89

1.86

1.39

1.07

0.57

0.81

1.67

2.34

2.10

2.41

1.92

1.87

2.16

2.42

6.74

7.27

6.04

5.63

6.29

5.83

6.84

Tb2O3

1.32

1.55

1.00

1.09

1.16

1.22

1.35

8.67

8.41

8.11

7.79

8.25

7.67

9.01

0.93

1.28

1.64

1.46

1.36

1.08

1.23

3.59

3.89

4.28

4.25

3.42

3.93

3.33

0.62

0.63

0.59

0.79

0.49

0.56

0.70

2.67

2.36

2.56

3.01

2.06

2.55

2.25

0.56

0.71

0.37

0.83

0.51

1.21

0.31

ThO

0.42

0.39

1.44

1.31

0.25

0.61

0.08

0.19

0.24

0.86

0.91

0.26

0.55

0.12

0.48

0.34

0.00

0.20

0.24

0.50

1.06

33.86

33.46

33.26

32.94

34.12

33.88

33.34

Total

101.42 100.90 100.48 101.13 100.02 101.76 100.81

Cations on the basis of 4 O

0.676

0.667

0.680

0.705

0.716

0.710

0.682

0.001

0.000

0.002

0.000

0.006

0.008

0.002

0.004

0.008

0.023

0.022

0.017

0.013

0.007

0.010

0.020

0.028

0.025

0.029

0.023

0.022

0.025

0.029

0.078

0.084

0.070

0.065

0.072

0.067

0.080

0.015

0.018

0.012

0.013

0.014

0.016

0.097

0.095

0.092

0.088

0.092

0.085

0.102

0.010

0.014

0.018

0.016

0.015

0.012

0.014

0.039

0.043

0.047

0.037

0.043

0.037

0.007

0.009

0.005

0.006

0.008

0.028

0.025

0.027

0.032

0.022

0.027

0.024

0.006

0.008

0.004

0.009

0.005

0.013

0.003

0.012

0.011

0.002

0.005

0.001

0.002

0.007

0.002

0.004

0.001

0.053

0.038

0.000

0.022

0.026

0.055

0.118

0.994

0.992

0.989

0.978

0.997

0.988

0.992

Total

2.064

2.050

2.011

2.039

2.035

2.068

2.133

501

Th-U-Pb DATING OF MONAZITE IN THE PERMIAN ROCKS OF THE WESTERN CARPATHIANS

Table 7: Chemical composition of albite in Krompachy in weight %.

Sample

Kr 12a

1 2

SiO

68.66

68.64

68.10

19.63

19.23

19.63

MgO

0.00

0.01

0.00

CaO

0.02

0.04

0.36

FeO

0.07

0.06

0.01

BaO

0.00

11.85

11.68

11.46

0.05

0.07

Total

100.28

99.71

99.63

Cations on the basis of 8 O

2.991

3.005

2.986

1.008

0.992

1.014

0.000

0.001

0.000

0.001

0.002

0.017

0.003

0.002

0.000

1.001

0.991

0.974

0.003

0.004

Total

5.007

4.996

The Alpine tectono-metamorphic processes created

structures in which hydrothermal fluids could circu-
late. U-Mo mineralization from low-grade stratiform
mineralization was remobilized and concentrated
(Rojkovič 1997). Sericitization, silicification and dep-
osition of apatite preceded the remobilization. Charac-
teristic for this process are veinlets and disseminated
uraninite, coffinite and U-Ti oxides including branner-
ite. They are accompanied by pyrite, molybdenite,
chalcopyrite, galena, pyrrhotite, montroseite, xeno-
time-(Y), monazite-(Ce) and quartz. This mineraliza-
tion is close by age and composition to remobilized
stratiform U-Mo mineralization in volcanoclastic and
volcanic rocks mentioned before. Remobilized U-Mo
mineralization was formed at temperatures ranging from
320 to 240 °C with maximum at 250 °C (Rojkovič et al.
1993). Hydrothermal solutions have mobilized during
compression associated with continental collision
similarly as Early to middle Cretaceous quartz-anker-
ite-sulphidic veins (Hurai et al. 2002). According to
the U-Pb dating, the age of high-grade uranium ore near
faults gave the Alpine age of 130± 20 Ma (Arapov et al.
1984). The Cretaceous age of uranium ore remobilization
in the Permian rocks (from 80 to 110 Ma) is known
from several deposits (Mittempergher 1972; Petra-
scheck et al. 1977; Lancelot et al. 1984). The results
of Th-U-Pb dating of vein monazite from Krompachy
associated with uranium mineralization confirm the
age of 124± 10.2 Ma.

Recent results of Th-U-Pb dating of monazite con-

firm the Permian age of acid volcanism and the Creta-
ceous age of remobilized vein uranium mineralization.

Acknowledgments:

The study was supported by Project

503 at the Ministry of the Environment and Grant VEGA
1/1026 / 04. The development of monazite dating method
was supported by Project 12—01—9 / 100 at the Ministry
of the Environment, SR. This manuscript benefited great-
ly from the reviews of I. Petrík, M. Svojtka and G. Nagy.

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