GeolCarp_Vol60_No6_439

www.geologicacarpathica.sk

GEOLOGICA CARPATHICA, DECEMBER 2009, 60, 6, 439—448 doi: 10.2478/v10096-009-0032-1

Permian single crystal U-Pb zircon age of the Rožňava

Formation volcanites (Southern Gemeric Unit, Western

Carpathians, Slovakia)

ANNA VOZÁROVÁ

, MILOŠ ŠMELKO

and

ILYA PADERIN

Comenius University Bratislava, Faculty of Natural Sciences, Department of Petrology and Mineralogy, Mlynská dolina G,

842 15 Bratislava, Slovak Republic; vozarova@fns.uniba.sk

All-Russian Geological Research Institute (VSEGEI), Sredny prospect 74, 199 106 St.- Petersburg, Russia

(Manuscript received April 29, 2009; accepted in revised form October 2, 2009)

Abstract: Zircon populations from the Rožňava Formation volcanic rock complex have been analysed. Euhedral zir-
cons from the 1

volcanogenic horizon with fine oscillatory growth zoning, typical of magmatic origin, gave the aver-

age concordia age of 273.3 ± 2.8 Ma, with Th/U ratios in the range of 0.44—0.73. The Permian ages ranging from 266 to
284 Ma were identified in the wider, zoned or unzoned, central zircon parts, as well as in their fine-zoned oscillatory
rims. The average concordia age of 275.3 ± 2.9 was obtained from the euhedral zircon population of the 2

volcanogenic

horizon of the Rožňava Formation. The analyses were performed on zoned magmatic zircons in the age interval from
267 to 287 Ma, with Th/U ratios in the range of 0.39—0.75. In the later zircon population two inherited zircon grains
were dated giving the age of 842 ± 12 Ma (Neoproterozoic) and 456 ± 7 Ma (Late Ordovician). The magmatic zircon ages
document the Kungurian age of Permian volcanic activity and contemporaneous establishment of the south-Gemeric
basin. The time span of volcanic activity corresponds to the collapse of the Western Carpathian Variscan foreland which
expanded southward.

Key words: Permian, Kungurian, post-Variscan rifting, synsedimentary volcanism, U-Pb magmatic zircon ages, inherited
grains.

Introduction

An extensive rift system developed gradually within the fore-
land of the Western Carpathian part of the Variscan orogenic
belt  during  the  Carboniferous—Permian.  These  extensional
events post-dated the main Late Devonian—Carboniferous and
Serpukhovian-Bashkirian  orogenic  events  (Vozárová  1998).
Post-orogenic  rifting  also  propagated  across  the  entire
Variscan  orogen  and  its  retro-arc  continental  basement  part.
Following the main phases of Variscan compression, thermal
crust  relaxation  occurred  in  Late  Pennsylvanian—Cisuralian
times.  This  created  rifts  and  grabens  that  allowed  accumula-
tion of the first stage of post-orogenic sedimentation. Within
the  post-orogenic  basins  mainly  coarse-grained  continental
sedimentary  formations  were  formed,  associated  with  wide-
spread calc-alkaline, bimodal and/or continental tholeiitic vol-
canism.  The  fragments  of  Upper  Pennsylvanian-Permian
sedimentary  basin  filling  are  preserved  as  part  of  the  main
Western  Carpathian  Alpine  crustal-scale  superunits  (from
the N to S: Tatricum, Northern and Southern Veporicum and
Northern and Southern Gemericum) and several cover nappe
systems  (Fatric,  Hronic,  Turnaic  and  Bôrka  Nappe;
Vozárová & Vozár 1988).

Generally, the stratigraphic position as well as the correla-

tion of these coarse-grained continental sedimentary forma-
tions is not easy to prove, due to lack of relevant faunal and
plant remains. One of the best ways to resolve this problem is
dating of the associated volcanic rocks, as they form good
correlational horizons throughout widespread regional areas

(McCann et al. 2008; Vozárová et al. 2009a). Thus, the post-
tectonic coarse-grained volcano-sedimentary sequence of the
Southern Gemeric Unit is no exception. The Permian age of
this sequence is documented only by scarce biostratigraphic
data.  The  problem  studied  here  is  focused  on  zircon  single
grain  age  determinations  of  the  acid  volcanic  and  volcani-
clastic rocks. Such study enables dating of a principal stage
of  the  Variscan  post-tectonic  extensional  movements  in  the
area  of  the  Inner  Western  Carpathians  as  well  as  to  specify
the stratigraphic position of the associated Gočaltovo Group
sediments.

Geological setting

Within the Southern Gemeric Unit, the post-orogenic over-

step sequences are represented by the Permian continental to
near-shore,  lagoonal-sabkha  formations  of  the  Gočaltovo
Group  (Fig. 1).  They  unconformably  overlap  their  basement,
the Early Paleozoic Gelnica Terrane, consisting of the pre-Per-
mian  low-graded  rock  complexes  of  the  Gelnica  Group  and
Štós Formation (Vozárová & Vozár 1996). Generally, the sed-
iments of the Gočaltovo Group represent the relic of rift-relat-
ed sedimentary basin fillings, which originated with the initial
stage  of  the  post-Variscan  extension  and  crustal  relaxation.
The whole sequence is subdivided into two lithostratigraphic
units: the basal Rožňava Formation and the upper Štítnik For-
mation (Bajaník et al. 1981; Fig. 2). The studied volcanites are
an integral part of the basal Rožňava Formation.

440

VOZÁROVÁ, ŠMELKO and PADERIN

The characteristic lithological feature of the Rožňava For-

mation is the high content of mature detritus, represented by
the  presence  of  the  oligomictic  quartzose  conglomerates  and
sandstones, with indistinct stratification. The whole Rožňava
sequence  is  vertically  subdivided  into  two  regional  wide-
spread  larger  cycles,  with  conglomerate  strata  at  the  base  of
each cycle and a shaly-sandstone member among them. Sedi-
mentary  structures  supporting  stream  channel  deposits  are
dominant,  with  a  distinct  unimodal  transport  system.  Both
conglomerate horizons were associated with the calc-alkaline
rhyolite-dacite  subaerial  volcanism.  Their  relics  are  recently
indicated as the 1

and 2

volcanogenic horizons (Fig. 2).

The Cisuralian age of the Rožňava Formation is assumed on

the basis of the poor microfloral assemblage, with the predom-
inant  species  from  the  genera  Potonieisporites,  Striatodisac-
cites,  Vittatina  sp.  and  mainly  the  form  Triquitrites  additus
Wilson  et  Hoffmeister,  Potonieisporites  novicus  Bharadwaj,
Vittatina  costabilis  Wilson,  Reticulatisporites  reticulocingu-
lum (Planderová 1980).

Detailed petrological and geochemical investigations of the

Rožňava Formation volcanites have not been done systemati-

cally up till now. All previous analytical data have been sum-
marized  by  Vozárová  (in  Marsina  et  al.  1999  and  references
therein).  According  to  this,  the  volcanites  were  classified  as
calc-alkaline rhyolites/rhyolite-dacites and they are markedly
enriched in B, Zr and Rb and only slightly enriched in La and
Y and depleted in Ba, Sr and V. Results based on zircon typol-
ogy  indicate  the  A-type  high-temperature  alkaline  magma
(Broska et al. 1993).

The Cisuralian age of the magmatic event at 276 ± 25 Ma

has been, for the first time, determined for the Rožňava For-
mation  volcanites  by  monazite  dating  (Vozárová  et  al.
2008). Isolated relics of Silurian age, 421 and 431 Ma, found
within  the  Permian  monazite  cores  were  interpreted  as  the
inherited  relics  from  the  source  rocks,  extracted  from  the
Lower Paleozoic protolith.

Method of investigation

Zircon populations from two samples of the 1

and 2

vol-

canogenic horizons of the Rožňava Formation rock complex

Fig. 1. Geological scheme of the Štítnik—Jelšava area with localization of samples (modified after Bajaník et al. 1984 and Mello et al. 1996).

441

PERMIAN SINGLE CRYSTAL U-Pb ZIRCON AGE OF THE VOLCANITES (WESTERN CARPATHIANS)

Fig. 2. Gočaltovo Group lithostratigraphic scheme (modified after Vozárová &
Vozár 1988). Explanation: 1 – metaconglomerate; 2 – metasandstone; 3 – shale;
4 – crystalline dolomitic limestone; 5 – albitolite; 6 – phosphatic metasand-
stone; 7 – tuffaceous/sedimentary mixed rocks; 8 – rhyolite-dacite volcaniclas-
tics; 9 – rhyolite-dacite.

have  been  analysed.  The  zircons  have  been  separated  from
rocks by standard grinding, heavy liquid and magnetic separa-
tion analytical procedures. The internal zoning structures and
shapes of the half-sectioned zircon crystals mounted in epoxy
resin puck with chips of the TEMORA (Middledale Gabbroic
Diorite,  New  South  Wales,  Australia)  and  91500  (Geostan-
dard zircon) reference zircons, were first imaged by BSE and
CL, in order to reveal surface features for analytical spots po-
sitioning.  In  situ  U-Pb  analyses  were  performed  on  a
SHRIMP-II  in  the  Center  for  Isotopic  Research  (CIR)  at
VSEGEI in St.-Petersburg, Russia.

Each analysis consisted of 5 scans through the mass range,

the diameter of each spot was about 25 µm, and primary beam
intensity  was  about  6 nA.  The  data  have  been  reduced  in  a
manner similar to that described by Williams (1998, and refer-
ences  therein),  using  the  SQUID  Excel  Macro  of  Ludwig
(2000).  The  Pb/U  ratios  have  been  normalized  relative  to  a
value of 0.0668 for the

206

Pb/

238

U ratio of the TEMORA ref-

erence zircons, equivalent to an age of 416.75 Ma (Black &
Kamo 2003). Uncertainties given for individual analyses (ra-
tios and ages) are at the 1

σ level; but the uncertainties in cal-

culated concordia ages are reported at 2

σ levels. The

Ahrens-Wetherill (1956) concordia plot has been prepared us-
ing ISOPLOT/EX (Ludwig 1999).

Petrography and geochemistry of

volcanites

Rhyolites of the 1

volcanogenic horizon are

composed  of  the  light  coloured  silicate,  mainly
potassium  feldspars  and  less  present  sodium
reach plagioclases. In texture they are classified
as  a  fine-grained,  primary  aphanitic  to  micro-
crystalline  in  the  matrix,  with  the  evidence  of
small  phenocrysts  of

β-quartz and alkali feld-

spars,  mainly  represented  by  soda-poor  micro-
cline  or  microcline-perthite  (matrix/phenocrysts
ratio = 1 : 3). A sanidine type of the alkali feldspar
shape is evident in some samples. Occasionally,
they  contain  besides  alkali  feldspars  also  phe-
nocrysts  of  sodium  rich  plagioclases  (An

5—15

)

and frequently associated with scarce biotite.
These porphyritic textures indicate that crystalli-
zation of phenocrysts began prior to extrusion,
when magma was deeper situated. Zircon, mona-
zite, xenotime, apatite, rutile and Fe-Ti oxide are
present as accessory minerals.

The 1

volcanogenic horizon acid volcanites

are associated with volcaniclastics, frequently
with textures indicating ignimbrite or welded
tuffs, flattened lithic and glassy pumice mixed with
vitric material, with relics of deformed “fiam

”.

The 2

volcanogenic horizon acid volcanites

have very fine-grained primary texture of vitric/or
glassy appearance, which contains only small
amounts of phenocrysts (maximum 5 % of the
whole rock), consisting mainly of

β-quartz. They

frequently contain voids and recrystallized glassy
fragments, as the evidence of having been formed
in a surface environment with rapid cooling. Only

pyroclastic ash-falls are associated with the 2

volcanogenic

horizon rhyolites. They have primary very fine-grained vitro-
clastic textures and are commonly interbedded and mixed with
siliciclastic sediments, mostly conglomerates and sandstones.

Permian sequences of the Southern Gemeric Unit are de-

formed and recrystallized, within metamorphic grade attaining
P-T conditions from anchizone to the low-temperature part of
the greenschist facies (Šucha & Eberl 1992; Vozárová 1996;
Vozárová & Rojkovič 2000). The newly formed metamorphic
mineral assemblage is represented by the fine-grained aggre-
gate of quartz + phengite + chlorite ± albite and/or microcline,
associated with scarce biotite in some places. The multistage
tectonothermal events in the south-Gemeric Permian metarhy-
olites, from the Late Jurassic—Early Cretaceous (167 ± 12 and
136 ± 10 Ma), were deduced from the electron microprobe
monazite dating (Vozárová et al. 2008).

Six samples were selected for representative chemical anal-

yses, three from the 1

volcanogenic horizon and three from

the 2

volcanogenic horizon. All samples were analysed for

major and trace elements content including REE. Their chemi-
cal composition was determined by ICP/ICP SM Acme Labo-
ratories Ltd. in Canada.

As they are only slight petrographic differences, the chemi-

cal composition of the Rožňava acid volcanites from the two

442

VOZÁROVÁ, ŠMELKO and PADERIN

volcanogenic horizons is practically identical. The representa-
tive chemical analyses of the studied samples are given in Ta-
ble 1. As a consequence of metamorphic alteration that
presumably modified their chemistry, particularly the content
of fluid mobile elements such as K, Na, Si, Rb and Cs, the use
of classification based on mobile elements (TAS) has been
considered unreliable. Therefore, a diagram based on relative-
ly immobile elements Nb/Y vs. Zr/TiO

(Winchester & Floyd

1977 modified according to Pearce 1996) was preferred for
classification purposes (Fig. 3a). The two groups of volcanites
are calc-alkaline and rhyolitic in character, with SiO

contents

ranging from 68.03 to 76.77 wt. %, and fall into peraluminous
suite (A/CNK = 1.35—2.64; A/NK = 1.33—2.45). Very high
K

O/Na

O ratio is a result of secondary alteration processes.

Volcanic  rocks  are  generally  characterized  by  extremely  low
CaO  (0.01—0.03 wt. %),  MgO  (from  0.39  to  0.66 wt. %)  and
relative  low  Fe

(from 0.73 to 2.46 wt. %) contents. The

chondrite-normalized trace-elements variation diagram for the

studied samples (Fig. 3b) reflects strong negative anomalies of
Ba, Nb, Sr and Ti, and enrichment in Rb, Th, K, La, Ce, Nd,
Hf and Y. These broadly indicate their A-type affinity. Simi-
larly, based on the chondrite-normalized REE distribution
(normalizing values after Taylor & McLennan 1985; Fig. 3c)
the rhyolites are enriched in light REE, and have relatively un-
fractionated heavy REE with

Σ(La/Yb)

= 3.5 and

Σ(Gd/

Lu)

= 1.6. These features, together with the distinct negative

Eu-anomaly (Eu/Eu* = 0.48) are typical for A-type magma-
tites. Based on Y/Nb ratio, which ranges from 2.3 to 2.6 in all
studied samples, the Rožňava rhyolites correspond to non-oro-
genic A

-subtype, which could indicate the post-collisional

magmatic environment (Eby 1992). According to Eby’s inter-
pretation this magmatic subtype consists of granites emplaced
in a variety of tectonic environments, including post-collision-
al, post-orogenic and anorogenic settings. Negative Nb anom-
alies are a common feature of igneous rocks formed in
destructive margin settings and derived from arc crust

volcanogenic horizon

Locality Hrádok

Hrádok

Hrádok Šebeková Šebeková Šebeková

Sample

04-SM

06-SM

08-SM

01-SM

02-SM

05-SM

wt. (%)

SiO

74.38

74.53

76.77

74.82

74.83

68.03

13.47

12.86

12.95

14.25

14.47

17.49

2.46

0.73

2.00

2.32

0.84

1.61

MgO

0.58

0.23

0.47

0.66

0.39

0.56

CaO

0.01

0.03

0.02

0.01

0.02

0.09

0.16

0.05

0.04

0.13

0.11

7.08

8.68

4.64

5.41

7.71

8.31

TiO

0.23

0.18

0.17

0.19

0.28

0.03

0.04

0.03

0.02

MnO

0.03

<0.01

0.01

<0.01

0.00

<0.002 <0.002 0.00

0.00

<0.002

LOI

1.80

2.50

2.90

2.40

1.60

3.60

Total

100.16

99.93

100.00

100.15

100.21

100.03

ppm

10.1

9.2

9.1

9.9

9.5

13.1

20.5

18.5

19.6

21.2

21.6

150.4

99.8

111

108.7

112.5

128.8

7.9

1.5

2.3

5.8

4.6

1.7

1.3

1.4

1.5

1.6

1.7

21.6

24.3

23.8

20.7

20.1

28.9

4.7

6.3

4.1

3.7

5.7

3.2

3.4

2.7

3.2

2.7

4.2

323.6

323

268

310.4

306.9

446.6

49.9

48.6

54.1

55.1

50.8

41.4

62.5

51.5

58.4

52.7

53.9

136.7

105.3

114.7

109.3

104

113.4

16.23

13.11

14.07

13.77

13.52

15.49

61.5

48.7

50.8

52.9

50.3

59.1

11.3

9.21

9.16

9.8

9.2

11.01

0.78

0.76

0.6

0.71

0.66

1.08

9.89

8.33

8.34

8.97

8.44

8.93

1.39

1.43

1.39

8.92

7.84

8.59

9.3

8.89

7.53

1.7

1.67

1.84

1.77

1.69

1.47

5.02

4.82

5.32

5.29

4.3

0.8

0.75

0.86

0.79

0.78

0.72

4.76

4.54

5.07

5.04

4.93

4.55

0.7

0.72

0.76

0.71

0.69

Table 1: Rock chemical analyses of the Rožňava Formation 1

and 2

volca-

nogenic horizons acid metavolcanites.

(Whalen  et  al.  1996).  The  origin  of  magma  of  the
Rožňava  felsic  volcanites  was  probably  connected
with  crustal  melting  associated  with  regional  post-
Variscan  extension  and  thermal  relaxation.  Its  com-
position presumably reflects source characteristics –
the  metasediments  and  metavolcanites  of  the  Lower
Paleozoic Gelnica Group. A non-orogenic geotecton-
ic interpretation may also be derived from the Nb /Y
(Fig. 3d) and Rb/(Yb + Ta) ratios and Rb/10:Hf:Tax3
referred  to  Pearce  et  al.  (1984)  and  Harris  et  al.
(1986)  discrimination  diagrams.  The  relative  enrich-
ment of Ce, Zr and Y is indicative for their compati-
bility  with  crustal  components  in  the  melt.  Negative
Ti,  Sr,  Ba  and  Eu  indicate  retention  of  plagioclases
and  accessory  minerals  during  partial  melting  (Col-
lins  et  al.  1982;  Pearce  et  al.  1984;  Whalen  et  al.
1996).

Zircon characteristics

Zircon characteristics are supplemented by electron

microprobe analyses, in addition to U-Th-Pb ion mi-
croprobe analyses performed on a SHRIMP-II in the
Center  for  Isotopic  Research  (CIR)  at  VSEGEI  in
St.-Petersburg,  Russia.  CAMECA  SX-100  electron
microprobe  at  Slovak  Geological  Survey,  Bratislava
was used for element concentration analyses. Si and
Zr together with elements such as Hf, Y, U, Th, P and
REE have been analysed (Table 2). La was below the
detection  limits.  The  operating  conditions  were  as
follows: 15 kV accelerating voltage, 40 nA beam cur-
rent, beam diameter 1—5 µm; standards – zircon (Zr,
Si), HfO

(Hf), apatite (P), YbPO

(Yb), wollastonite

(Ca), CePO

(Ce), ThO

(Th), YPO

(Y), Gd

(Gd); connecting period at 30 s (Si, Zr), 50 s (Hf),
110 s (Y) and 140 s (U, Th).

The analysed zircons exhibit composition zonation

trends of increasing HfO

and (UO

+ ThO

) concen-

trations and decreasing ZrO

/HfO

ratios from the

core to the rim of the crystals (Table 2). The HfO

443

PERMIAN SINGLE CRYSTAL U-Pb ZIRCON AGE OF THE VOLCANITES (WESTERN CARPATHIANS)

vol

c h

izo

lca

nog

ori

nal

ana

dar

k z

one

ight

ore

dar

k r

ight

ore

dar

k r

ight

ore

dar

k r

dar

k r

ight

ore

t. %

)

(wt

. %

)

t. %

)

t. %

)

t. %

)

t. %

)

t. %

)

(wt

. %

)

t. %

)

t. %

)

t. %

)

t. %

)

t. %

)

t. %

)

t. %

)

t. %

)

t. %

)

Tot

101

101.

.37

.91

.84

Fig. 3. Rožnava Formation acid volcanite characteristics based on the
chemical composition. a – Zr/TiO

(wt. %) vs. Nb/Y (ppm) dia-

gram after Winchester & Floyd (1977) modified by Pearce (1996).
b – Chondrite normalized (Thompson 1982) trace elements abun-
dances. c – Chondrite normalized REE patterns. Normalizing val-
ues are after Taylor & McLennan (1985). d – Variation Nb (ppm) vs.
Y (ppm) with indication of tectonic settings after Pearce et al. (1984).

Table 2:

Representative

magmatic

zircon

analyses

the

Rožňava

Formati

metarhyolites.

444

VOZÁROVÁ, ŠMELKO and PADERIN

abundance  of  these  zircons  range  from  0.77  to
2.03 wt. %  and  the  mean  of  1.29 wt. %  falls  in
the  field  of  Hf  (wt. %)  variation  in  the  zircon
associations  of  acid  magmatic  rocks  (Wark  &
Miller 1993; Hoskin & Ireland 2000; Hoskin &
Schaltegger  2003  and  references  therein).  The
variation  of  the  ZrO

/HfO

ratios in the zircon

assemblage ranges from 86 to 57 in the core and
from  78  to  42  in  the  rim.  The  Th/U  ratios  are
high, ranging from 0.42 to 0.89, typical for mag-
matic  rocks.  Based  on  chemical  composition  of
studied  zircons,  the  dominant  substitution  was
probably  the  simple  mechanism  (Hf

= Zr

)

combined with coupled substitution “xenotime”
mechanism [(Y, REE)

= Zr

+Si

] (Speer

1982), which is reflected in variations of Y con-
tents (from 0.1 to 0.8 wt. %) and

ΣREE abun-

dance (0.15—1.31 wt. %).

SHRIMP ages

Samples 8-SM and 2-SM from the 1

and the

volcanogenic horizons were dated from the

Rožňava Formation volcanic rock suite.

Sample 8-SM: Loc.: West of Štítnik town, for-

est road 550 m SW from the Hrádok Hill (810 m

Fig. 4. Selected CL zircon images from the Rožňava Formation 1

horizon

metavolcanites (sample no. 8-SM) and age data based on

206

Pb/

238

U ratios with

indication of measurement points.

altitude). Coordinates: N 48°92’020”, E 20°48’165”; 750 m
above sea level.

A typical feature of the majority of the studied 8-SM zircon

population is the presence of well developed growth zoning. It
is quite commonly observed that regular growth zoning is in-
terrupted  by  textural  discontinuities  along  which  the  original
zoning  is  resorbed  and succeeded by the growth of a newly-
zoned  zircon.  These  resorption  events  probably  reflect  inter-
ference  periods  of  Zr  undersaturation  in  the  magma.  Some
zircon crystals with bipyramidal sector zoning occur. The de-
velopment of sector zoning has been attributed to kinetic fac-
tors  and  changes  in  the  magmatic  environment  during  crystal
growth (Paterson & Stephens 1992) or to the relation between
growth  rates  and  lattice  diffusivity  (Watson  &  Liang  1995).
Vavra et al. (1996) referred sector zoning to rapidly fluctuating
and unequal growth rates related to the roughness of the growth
surface and degree of saturation of the growth medium.

Euhedral zircons with fine oscillatory zoning, typical of

magmatic  origin  (Fig. 4),  gave  an  average  concordia  age  of
273.3 ± 2.8 Ma (Probability of concordance = 0.90; MSWD of
concordance = 0.016;  n = 10;  Fig. 5),  with  Th/U  ratios  within
the  range  of  0.44—0.73  (Table 3).  The  Permian  ages  ranging
from  266  to  284 Ma  were  determined  in  the  wider  zoned  or
unzoned central parts of the zircon crystals, as well as in their
fine growth oscillation zoned rims.

Sample 2-SM: Loc.: West of Gočaltovo village, 50 m N of the

Šebeková Hill (643 m altitude). Coordinates: N 48°92’180”,
E 20°48’020”; 630 m above sea level.

Zircon population from the sample 2-SM contains crystals

with fine oscillatory growth zoning and less with sector zon-
ing (Fig. 6). A special case is local modification of magmatic
zircon by the magmatic phenomena, which tend to disrupt

the concentric oscillatory zoning and to develop irregular do-
mains in zircon, thus cutting discordantly growth zoned do-
mains.

The occurrence of xenocrystic zircons is a common feature

in sample 2-SM. Zircon xenocrysts occur as cores mantled by
newly grown magmatic zircons (Fig. 6). Xenocrystic cores are
recognized from their rims by geometrically irregular surfac-
es, which truncate internal zoning or separate sub-rounded un-
zoned or chaotically zoned cores.

The average concordia age of 275.3±2.9 (Probability of

concordance = 0.85; MSWD of concordance = 0.035; n = 10)
was obtained from the euhedral zircon population of the sam-
ple 2-SM (Fig. 7). The analyses were performed from oscilla-
tory zoned magmatic zircons in the age interval from 267 to
287 Ma, with Th/U ratios within the range of 0.39—0.75
(Table 3).

From the studied zircon population, two inherited zircon

grains were dated, which gave 842 ± 12 Ma  (Neoproterozoic)
and 456 ± 7 Ma (Late Ordovician) age (Table 3). They could be
either  supracrustal  and/or  magmatic  in  origin.  Presumably
they  were  incorporated  in  the  Permian  magmatic  event  from
the  underlying south-Gemeric  basement,  in  which  the  Upper
Ordovician metavolcanites of the Bystrý potok Formation (the
Gelnica Group) contain Neoproterozoic inherited zircon cores
(Vozárová et al. 2009b).

Discussion and conclusions

The obtained in situ U-Pb (SHRIMP) zircon ages clearly

document the timing of post-Variscan extensional rifting in
the internal zone of the Variscan Western Carpathians. The

445

PERMIAN SINGLE CRYSTAL U-Pb ZIRCON AGE OF THE VOLCANITES (WESTERN CARPATHIANS)

Fig. 5. Rožňava Formation 1

horizon metavolcanites concordia di-

agram of zircon age data (sample no. 8-SM).

Table 3: Rožňava Formation metavolcanites ion microprobe zircon data.

Gemeric Unit

Gočaltovo Group

Rožňava Formation

206

ppm

232

Th/

238

ppm

206

Pb*

206

Pb/

238

Age (Ma)

207

Pb/

206

Age (Ma)

Discor-

dant

8-SM_1.1(core)

0.03

614

310

0.52 23

274.6

±4.2

287

±37

8-SM_2.1(rim)

0.00

135

0.44 5

272.6

±5

288

±76

8-SM_3.1(rim)

0.23

541

245

0.47 20.1

272.9

±4.1

269

±57

–1

8-SM_4.1(rim)

0.42

253

178

0.73 9.69

280.2

±4.5

271

±87

–3

8-SM_5.1(core)

0.11

151

0.61 5.17

250.9

±4.5

250

±83

8-SM_6.1(core)

0.16

710

341

0.50 26.5

273.1

±4.2

262

±68

–4

8-SM_7.1(core)

0.00

0.44 1.21

265.8

±6.5

292

±150

8-SM_8.1(core)

0.26

741

375

0.52 26.8

265.5

±4

255

±49

–4

8-SM_9.1(core)

0.21

463

310

0.69 16.9

268

±4.1

265

±61

–1

8-SM_10.1(core)

0.17

379

256

0.70 14.3

275.7

±4.3

252

±76

–9

8-SM_11.1(core)

0.25

204

123

0.62 7.92

284.1

±4.7

264

±95

–7

2-SM_1.1(rim)

140

0.47 5.36

281.1

±4.8

350

±110

2-SM_2.1(rim)

164

0.52 6.26

280.8

±4.9

290

±68

2-SM_3.1(rim)

0.06

0.39 1.51

279.1

±6.4

219

±150

–22

2-SM_4.1(rim)

169

0.50 6.24

272.1

±4.6

344

±77

2-SM_5.1(core)

0.16

447

398

0.92 16.8

275.9

±4.2

228

±62

–17

2-SM_6.1(core)

0.10

445

505

1.17 53.4

842

±12

835

±23

–1

2-SM_6.2(rim)

174

0.54 6.68

281.9

±4.7

300

±68

2-SM_7.1(core)

0.03

170

0.46 10.7

455.9

±7.2

422

±68

–7

2-SM_7.2(rim)

0.09

368

190

0.54 13.7

272.8

±4.2

284

±50

2-SM_8.1(rim)

0.10

251

183

0.75 9.01

263.4

±4.4

239

±68

–9

2-SM_9.1(rim)

0.18

289

209

0.75 10.5

267.2

±4.2

225

±66

–16

2-SM_10.1(rim)

0.46

188

117

0.64 7.37

286.9

±4.8

282

±120

–2

average  concordia  ages  of  273 ± 2.8  or  275 ± 2.9 Ma  corre-
spond to the Kungurian (the latest Cisuralian according to the
International Stratigraphic Chart, Gradstein et al. 2004). This
magmatism  coincided  with  evolution  of  the  Cisuralian  rift
system,  post-dating  the  Devonian-Mississippian  accretion  of
the  Neoproterozoic/Early  Paleozoic  peri-Gondwana  derived
microplates (Gotic Terrane – Stampfli et al. 2001a; Hun Ter-
rane – Stampfli et al. 2002; Galatian Terrane – von Raumer
& Stampfli 2008), with polyphase colliding into the southern
margin  of  Laurussia.  The  Western  Carpathian  Variscides,  as
an  easterly  continuation  of  the  Austro-Alpine  Domain  of  the

Alps, were a part of this geodynamic system. The final stage
of the Variscan collision shifted crustal blocks of the Central
Western Carpathian Crystalline Zone on to the terranes of the
Northern Gemeric Zone, where tectonically squeezed out rel-
ics of island arc and oceanic crustal fragments were preserved,
on the Cambrian-Ordovician Gelnica Terrane margin
(Vozárová 1998).

The change of regional stress patterns was coincident with

termination of orogenic activity in the Variscan orogenic belt
and  was  followed  by  major  dextral  translation  between
Gondwana  and  Laurussia  (Ziegler  1990;  Ziegler  &  Cloe-
tingh 2004). The Variscan orogenic belt of the Western Car-
pathians  during  the  post-Variscan  evolution  was  deeply
truncated  with  its  superimposed  system  of  the  Pennsylva-
nian-Permian  wrench-induced  troughs.  The  Pennsylvanian-
Cisuralian  collapse  of  the  Western  Carpathian  Variscan
internides, of which relics are preserved in the Alpine tecton-
ic  superunits:  Tatricum,  Veporicum,  Zemplinicum  and
Hronicum, is documented to have expanded southward over
time (Vozárová 1996, 1998). The Cisuralian collapse of the
southern  foreland  is  reflected  within  the  Permian  sequence
of the Southern Gemeric Unit.

Rifting, after rapid sedimentation of coarse-grained mature

sediments,  was  associated  with  synsedimentary  magmatic
activity.  It  is  well  documented  in  the  lithostratigraphic  se-
quence  of  the  Gočaltovo  Group  (Fig. 2).  Polystage  regional
uplift  coincided  with  regional  cyclic  sedimentation,  as  well
as with the polyphase volcanic activity in the context of the
1

and 2

volcanogenic horizons (Vozárová 1977). This up-

lift was probably induced by a complex combination of
wrench-related lithospheric deformation and magmatic infla-
tion of the lithosphere.

Permian Basin-and-Range basin type rifting was postulated

for the Central Western Carpathians by Dostal et al. (2003)

446

VOZÁROVÁ, ŠMELKO and PADERIN

Fig. 6. Selected CL zircon images from the Rožňava Formation 2

horizon (sample

no. 2-SM) metavolcanites and age data based on

206

Pb/

238

U ratios with indication of

measurement points.

Fig. 7. Concordia diagrams of zircon age data from the Rožňava
Formation 2

horizon metavolcanites (sample no. 2-SM).

in the Hronic Unit. According to their interpre-
tation  this  rifting  followed  the  collision  of  the
Paleo-Tethys ridge with the trench bordering the
southern  margin  of  Laurussia  (in  the  sense  of
tectonic model of Stampfli 2001a,b). The south-
Gemeric Rožňava Formation acid metavolcanites
do not appear to be directly related to the mafic
rocks. They were connected with crustal melting,
but is not excluded that the melting was triggered
by  an  elevated  temperature  gradient  caused  by
ascending  basaltic  magma,  as  is  supposed  by
Dostal et al. (2003).

The approximately equal zircon ages of the

two volcanogenic horizons remain an open ques-
tion, since it could be presupposed that in the
case of normal lithostratigraphic sequence, the
2

horizon volcanites might be younger then the

ones. The presented SHRIMP zircon ages

show reverse trend, that means 273 ± 2.8 Ma con-
cordia age for the 1

horizon volcanites and

275 ± 2.9 Ma zircon age for the 2

one. Both cor-

respond to the Kungurian age and the age differ-
ence is within the calculated standard deviation
and standard analytical error.

Considering these age data, the Permian development of the

south-Gemeric sedimentary basin was rapidly pulsating in ex-
tensional  stages,  following  cyclicity  in  sedimentation  and
synsedimentary  volcanic  activity.  The  Rožňava  Formation
sedimentary sequence could have been formed in a relatively
short  lived  transtensional  event,  within  the  Kungurian  time
span, not more than five and half million years long. A rapid
subsidence  coincides  with  the  pulsating  stage  of  extensional
movements and was associated with synsedimentary volcanic
activity. Referring to recent thickness of the Rožňava Forma-
tion rock sequence with calculation its diminishing due to dia-
genetic and metamorphic changes, the presumed sedimentation
rate was relatively high, between 7 and 10 cm/yr. After the ini-
tial rapid sedimentation and synsedimentary tectonic activity,
the  Permian  (Guadalupian-Lopingian)  sedimentary  evolution
of  the  south-Gemeric  basin  had  significantly  less  dynamic
conditions. This is reflected in the absence of volcanic activity
and  coarse-grained  sediments  within  the  sedimentary  se-
quence of the Štítnik Formation.

Two inherited grains were dated within the cores of the

magmatic zircons from the sample 2-SM (Fig. 6). Both were
presumably derived from the melted south-Gemeric basement
rocks.  The  age  of  the  Neoproterozoic  inherited  grain
(842 ± 12 Ma)  fully  corresponds  to  the  dominant  detrital  zir-
con ages coming from the Gelnica Group metasediments (un-
published  results).  Similarly,  the  majority  of  the  inherited
grains within the magmatic zircon cores of the Cambrian/Or-
dovician Gelnica Group metavolcanites confirm the same age
(Vozárová  et  al.  2009b).  The  second  inherited  grain  of  the
Middle/Late Ordovician age (456 ± 7 Ma) corresponds well to
the youngest in situ U-Pb zircon ages of the metavolcanites of
the Gelnica Group (Vozárová et al. 2009b).

Acknowledgments: The financial support of the Slovak Re-
search and Development Support Agency (Project ID: APVV-

447

PERMIAN SINGLE CRYSTAL U-Pb ZIRCON AGE OF THE VOLCANITES (WESTERN CARPATHIANS)

0438-06) and of the Scientific Grant Agency of the Ministry
of Education of the Slovak Republic and the Slovak Academy
of Sciences (Project ID: VEGA 2/0072/08) is gratefully ac-
knowledged. The authors would like to thank I. Broska, I.
Petrík and the unknown reviewer, who constructively enabled
significant improvement of the manuscript.

References

Bajaník Š., Vozárová A. & Reichwalder P. 1981: Lithostratigraphic

classification of Rakovec Group and Late Paleozoic sediments
in the Spišsko-gemerské rudohorie Mts. Geol. Práce, Spr. 75,
27—56 (in Slovak).

Bajaník Š., Ivanička J., Mello J., Pristaš J., Reichwalder P., Snopko

L., Vozár J. & Vozárová A. 1984: Geological map of the Slo-
venské rudohorie Mts. – eastern part 1 : 50,000. D. Štúr Inst.
Geol., Bratislava.

Black L.P. & Kamo S.L. 2003: TEMORA 1: a new zircon standard

for U-Pb geochronology. Chem. Geol. 200, 155—170.

Broska I., Vozár J., Uher P. & Jakabská K. 1993: Zircon typology

from the Permian rhyolite-dacite and their volcaniclastics
(Western Carpathians). In: Rakús M. & Vozár J. (Eds.): Geody-
namic evolution and deep structure of the Western Carpathians.
D. Štúr Inst. Geol., Bratislava, 151—158 (in Slovak).

Collins W.J., Beams S.D., White A.J.R. & Chappel B.W. 1982: Na-

ture and origin of A-type granites with particular reference to
southeastern Australia. Contr. Mineral. Petrology 80, 189—200.

Dostal J., Vozár J., Keppie J.D. & Hovorka D. 2003: Permian volcan-

ism in the Central Western Carpathians (Slovakia): Basin-and-
Range type rifting in the southern Laurussian margin. Int. J. Earth
Sci. (Geol. Rundsch.) 92, 27—35. doi: 0.1007/s00531-002-0307-6.

Eby N.G. 1992: Chemical subdivision of the granitoids. Petrogene-

sis and tectonic implication. Geology 20641—644.

Gradstein F.M., Ogg J.G., Smith A.G., Bleeker W. & Lourens L.J.

2004: A new geological time scale with special reference to Pre-
cambrian and Neogene. Episodes 27, 2, 83—100.

Harris N.B.W., Pearce J.A. & Tindle A.G. 1986: Geochemical char-

acteristics of collision-zone magmatism. Geol. Soc., Spec. Publ.
19, 67—81.

Hoskin P.W.O. & Ireland T.R. 2000: Rare Earth chemistry of zircon

and its use as a provenance indicator. Geology 28, 627—630.

Hoskin P.W.O. & Schaltegger U. 2003: The composition of zircon

and igneous and metamorphic petrogenesis. Rev. Mineral.
Geochem. 53, 27—62. doi: 10.2113/0530027.

Ludwig K.R. 1999: User’s manual for Isoploths/Ex, Version 2.10. A

geochronological toolkit for Microsoft Excel. Berkeley Geo-
chronology Center, Spec. Publ. No. 1a, 2455 Ridge Road, Ber-
keley CA 94709, USA.

Ludwig K.R. 2000: SQUID 1.00, A User’s Manual. Berkeley Geo-

chronology Center, Spec. Publ. No. 2, 2455 Ridge Road, Berke-
ley, CA 94709, USA.

Marsina K., Bodiš D., Havrila M., Janák M., Káčer Š., Kohút M.,

Lexa J., Rapant S. & Vozárová A. 1999: Geochemical atlas of
Slovak Republic. Part III: Rocks. Geol. Surv. Slovak Republic —
Ministry of Environment of Slovak Republic, Bratislava, 1—135.

McCann T., Kiersnowski, Krainer K., Vozárová A., Peryt T., Opluštil

S., Stollhofen H., Schneider J., Wetzel A., Boulvain F., Dusar
M., Török Á., Haas J., Tait J. & Körner F. 2008: Permian. In:
McCann T. (Ed.): The geology of Central Europe. Volume 1:
Precambrian and Palaeozoic. Geol. Soc. London, 531—598.

Mello J., Elečko M., Pristaš J., Reichwalder P., Snopko L., Vass D. &

Vozárová A. 1996: Geological map of the Slovak Karst
1:50,000. Geol. Surv. Slovak Republic, Bratislava.

Paterson B.A. & Stephens W.E. 1992: Kinetically induced composi-

tional zoning in titanite: Implication for accessory-phase/melt
partitioning of trace elements. Contr. Mineral. Petrology 109,
373—385.

Pearce J. 1996: Sources and settings of granitic rocks. Episodes 19,

120—125.

Pearce J.A., Harris N.B.W. & Tindle A.G. 1984: Trace element dis-

crimination diagrams for the tectonic interpretation of granitic
rocks. Geol. Soc., Spec. Publ. 7, 14—24.

Planderová E. 1980: New result about age of “Rožňava Železník”

Group. Geol. Práce Spr. 60, 143—168 (in Slovak).

Speer J.A. 1982: Zircon. Rev. in Mineralogy 5 (2

ed.), 67—112.

Stampfli G.M., Borel G.D., Cavazza W., Mosar J. & Ziegler P.A.

2001a: Palaeotectonic and palaeographic evolution of the west-
ern Tethys and Peri-Tethyan domain. Episodes 24, 222—228.

Stampfli G.M., Mosar J., Favre P., Pillevuit A. & Vannay J.C. 2001b:

Permo-Mesozoic  evolution  of  the  western  Tethyan  realm:  the
Neotethys/East  Mediterranean  connection.  In:  Ziegler  P.A.,
Cavazza  W.,  Robertson  A.H.F.  &  Crasquin-Soleau  S.  (Eds.):
Peri-Tethys memoir 6: Peritethyan rift/wrench basins and passive
margins, IGCP 369, Paris. Mém. Mus. Nat. Hist. 186, 51/108.

Stampfli G.M., von Raumer J. & Borel G.D. 2002: The Paleozoic

evolution of pre-Variscan terranes: From Gondwana to the
Variscan collision. In: Martinez-Catalan J.R., Hatcher R.D. Jr.,
Arenas R. & Diaz-Garcia F. (Eds.): Variscan-Appalachians dy-
namics: The building of the Late Paleozoic basement. Geol. Soc.
Amer., Spec. Pap. 364, 263—280.

Šucha V. & Eberl D.D. 1992: Postsedimentary alteration of the Per-

mian sediments in the northern Gemericum and Hronicum of the
Western Carpathians. Miner. Slovaca 24, 399—405 (in Slovak).

Taylor S.R. & McLennan S.M. 1985: The continental crust: its com-

position and evolution. Blackwell, Oxford, 1—312.

Thompson R.N. 1982: British Tertiary volcanic province. Scot. J.

Geol. 18, 49/107.

Vavra G., Gebauer D., Schmidt R. & Compston W. 1996: Multiple

zircon growth and recrystallization during polyphase Late Car-
boniferous to Triassic metamorphism in granulites of the Ivrea
zone (Southern Alps): An ion microprobe (SHRIMP) study.
Contr. Mineral. Petrology 122, 337—358.

von Raumer J.F. & Stampfli G.M. 2008: The birth of Rheic Ocean –

Early Paleozoic subsidence patterns and subsequent tectonic
plate scenarios. Tectonophysics 461, 9—20.

doi: 10.1016/j.tecto.2008.04.012
Vozárová A. 1977: Petrography of Late Paleozoic sediments of the

SE part of the Spišsko-gemerské rudohorie Mts. Západ. Karpaty,
Ser. Min., Petr., Geoch., Metal. 3, 147—174.

Vozárová A. 1996: Tectono-sedimentary evolution of Late Paleozoic

basins based on interpretation of lithostratigraphic data (Western
Carpathians, Slovakia). Slovak Geol. Mag. 3—4, 251—271.

Vozárová A. 1998: Late Carboniferous to Early Permian time interval

in the Western Carpathians: Northern Tethys Margin. Geodiver-
sitas 20, 4, 621—641.

Vozárová A. & Rojkovič I. 2000: Permian lacustrine phosphatic

sandstone in the Southern Gemeric Unit, Western Carpathians,
Slovakia. Geol. Carpathica 51, 265—278.

Vozárová A. & Vozár J. 1988: Late Paleozoic in West Carpathians.

Monogr., D. Š. Inst. Geol., Bratislava, 1—314.

Vozárová A. & Vozár J. 1996: Terranes of West Carpathians –

North Pannonian Domain. Slovak Geol. Mag. 1, 61—83.

Vozárová A., Konečný P., Vozár J. & Šmelko M. 2008: Upper Juras-

sic—Lower Cretaceous tectonothermal events in the Southern
Gemeric Permian rocks deduced from electron microprobe dating
of monazite (Western Carpathians, Slovakia). Geol. Carpathica
59, 2, 89—102.

Vozárová A., Ebner F., Kovács S., Kräutner H.-G., Szederkenyi T.,

Krstić B., Sremac J., Aljinovic D., Novak M. & Skaberne D.
2009a: Late Variscan (Carboniferous to Permian) environments in

448

VOZÁROVÁ, ŠMELKO and PADERIN

the Circum Pannonian Region. Geol. Carpathica 60, 1, 71—104.
doi: 10.2478/v10096-009-0002-7.

Vozárová A., Šarinová K., Larionov A., Presnyakov S. & Sergeev S.

2009b: Late Cambrian/Ordovician magmatic arc type volcanism
in the Southern Gemericum basement, Western Carpathians,
Slovakia: U-Pb (SHRIMP) data from zircons. Int. J. Earth Sci.
doi: 10.1007/s 00531-009-0454-0 (in print).

Watson E.B. & Liang Y. 1995: A simple model for section zoning in

slowly grown crystals: Implication for growth rate and lattice
diffusion with emphasis on accessory minerals in crustal rocks.
Amer. Mineralogist 80, 1179—1187.

Wetherill G.W. 1956: Discordant uranium-lead ages. Trans. Amer.

Geophys. Union 37, 320—326.

Whalen J.B., Jenner G.A., Longstaffe F.J., Robert E. & Gari

py C.

1996: Geochemical and isotopic (O, Nd, Pb and Sr) constraints

on A-type granite petrogenesis based on the Topsails igneous
suite, Newfoundland Appalachians. J. Petrology 37, 1463—1489.

Williams I.S. 1998: U-Th-Pb geochronology by ion microprobe. In:

McKibben M.A., Shanks III W.C. & Ridley W.I. (Eds.): Appli-
cations of microanalytical techniques to understanding mineral-
izing processes. Rev. Econ. Geol. 7, 1—35.

Winchester J.A. & Floyd P.A. 1977: Geochemical discrimination of

different magma series and differentiation products using immo-
bile elements. Chem. Geol. 20, 325—343.

Ziegler A.M. 1990: Phytogeographic patterns and continental config-

urations during the Permian Period. In: McKerrow W.S. &
Scotese C.R. (Eds.): Palaeozoic palaeogeography and biogeog-
raphy. Geol. Soc. London, Mem. 12, 263—379.

Ziegler A.M. & Cloetingh S. 2004: Dynamic processes controlling

rifted basins. Earth Sci. Rev. 64, 1—2, 1—50.