GeolCarp_Vol49_No4_261

GEOLOGICA CARPATHICA, 49, 4, BRATISLAVA, AUGUST 1998

261270

ZIRCON IN HERCYNIAN GRANITIC PEGMATITES

OF THE WESTERN CARPATHIANS, SLOVAKIA

PAVEL UHER

and PETR ÈERNÝ

Geological Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 842 26 Bratislava, Slovak Republic

Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba, R3T 2N2 Canada

(Manuscript received November 8, 1997; accepted in revised form March 24, 1998)

Abstract: Zircon is an uncommon but widespread accessory mineral in Hercynian barren to beryl-columbite rare-el-

ement granitic pegmatites of the Central Western Carpathians, Slovakia. BSE images show either homogeneous com-

position, or irregular to oscillatory zoning, and locally also two-stage crystal growth. Electron-microprobe analysis

reveals elevated Hf, locally also P, Y, REE, Al, Fe and Ca. Hafnium content and Zr/Hf ratio are proportional to the

fractionation degree of the host pegmatite; zircon from the barren pegmatites attains 1 to 8 wt.% HfO

(average 3 wt.%),

zircon from the beryl-columbite pegmatites contains 2 to 22 wt.% HfO

(average 7 wt.%). HfZr

-1

, Al

and

(Y,HREE,Fe)

(Zr,Hf)

are the possible substitution mechanisms. Calculation of the temperature of zircon satu-

ration gave T

≈

700 to 580

C, which corresponds to a primary magmatic origin of the zircon.

Key words:Western Carpathians, geochemistry, temperature of crystallization, granitic pegmatite, zircon.

Introduction

Zircon is one of the most widespread accessory minerals in a

great variety of igneous rocks, including the granitic pegma-

tites. Although the largest concentrations of zircon are affili-

ated with alkaline granites, syenites and their pegmatites, the

peraluminous granitic pegmatites of the LCT-family (Èerný

1991) usually contain a little zircon. Zircon is practically the

only Zr-rich phase in non-alkaline igneous environments;

baddeleyite ZrO

, elpidite Na

ZrSi

.3H

O and other com-

plex zirconosilicates occur only in highly alkaline suites.

Crystal morphology, internal texture and especially

geochemistry of igneous zircon are useful indicators of con-

ditions controlling the growth of zircon and consolidation of

its host rock. The current understanding of zircon is based

on the dependence between the pyramidal/prismatic ratio of

zircon crystals and temperature or the genetic type of parent

rock (Pupin 1980), on internal growth pattern detectable by

BSE and cathodolumiscence (Vavra 1990), and on chemis-

try (mainly the Zr/Hf ratio and distribution of U, Th, Y and

REE; Pupin 1992). The zircon-saturation experiments for

felsic magmas facilitate calculation of reasonable crystalli-

zation temperatures of zircon (Watson & Harrison 1983).

Pegmatitic zircon regarded commonly as a product of true

magmatic crystallization is also a potential petrological in-

dicator of cooling history, fractionation level and tempera-

ture. Its chemistry is more complex than that of zircon

from granites, as it shows large variations in Zr/Hf, P, Y,

REE, U, Th, Ca and other elements, depending on the frac-

tionaction level of the pegmatite, and on local chemical en-

vironment (Èerný et al. 1985; Kapustin 1985). However, the

geochemical and petrological significance of pegmatite zir-

con is still rarely utilized, and only regional studies based

on statistically adequate databases can reveal the correla-

tions between the properties of zircon and the characteris-

tics of host pegmatites. This paper is an attempt to contribute

to this line of study, using the example of zircon from 18 gra-

nitic pegmatites of the Western Carpathians (Fig. 1).

Parent granites and pegmatites

The West-Carpathian granitic pegmatites form dyke- to

lens-like bodies emplaced in the parent granitic rocks or in

adjacent amfibolite-facies lithologies, mainly metapelites-

metapsammites and rarely metabasalts. The parent granitic

rocks are Hercynian, mainly Lower Carboniferous biotite

and two-mica (leuco)tonalites, granodiorites, granites to

muscovite leucogranites, with orogenic calc-alkaline S- or

I-type affinities (Petrík et al. 1994).

Hercynian granitic pegmatites can be subdivided into two

principal genetic groups on the basis of the mineralogy and

geochemistry of their parent granites and the pegmatites

themselves (Uher 1994; Uher & Broska 1995):

(1) Pegmatites of S-type, monazite-bearing granites,

Moravany-type (PMOG).

(2) Pegmatites of I-type, allanite-bearing granites, Pra-

ivá-type (PAOG).

Some granite-pegmatite suites reveal mixed characteris-

tics between (1) and (2), and it is still not clear whether

they represent a third independent granite-pegmatite associ-

ation, or only atypical members of (1) or (2). Only more pre-

cise geochemical and especially geochronological data

could solve this problem in the future.

The following paragenetic zones have been described in

West-Carpathian pegmatites (Dávidová 1978, 1981): (1)

aplitic, (2) feldspar-quartz-mica, (3) graphic, (4) blocky mi-

crocline, (5) blocky quartz, (6) quartz-(plumose) muscovite

and (7) albite; the first five zones are suggested primary mag-

matic, the zones (6) and (7) are believed to be autometasomat-

-2

-1

262 UHER and ÈERNÝ

ic (Dávidová, l.c.). The majority of pegmatites exhibit rela-

tively simple zoning, from graphic borders through intermedi-

ate blocky K-feldspar and/or coarse-grained K+Na-feldspar-

quartz-muscovice-(biotite) zone to quartz-(muscovite) core.

Late-magmatic albite-rich units (albitic aplite or cleave-

landite+quartz) replace in part the above zones; they occur

only in the more fractionated pegmatites, e.g. the Moravany

nad Váhom pegmatite (Uher 1991; Uher & Broska 1995).

PMOG bodies are muscovite- and garnet-rich, while PAOG

members are more primitive with both biotite and muscovite.

The most widespread coarse-grained quartz+K-feldspar±

albite+muscovite±biotite intermediate pegmatite zone or

blocky K-feldspar rich zone (Kunerad pegmatite) was sam-

pled for zircon. Other accessory minerals comprise almand-

ine-spessartine, fluorapatite, monazite-(Ce), xenotime-(Y),

uraninite, magnetite, gahnite, pyrite and arsenopyrite. Acces-

sory beryl, columbite-tantalite and rarely ferrotapiolite, Nb,

Ta-rich rutile, pyrochlore-group minerals and fersmite are

formed only in the more fractionated pegmatites. These latter

bodies belong to the beryl-columbite subtype of the beryl

type, LCT-family, rare-element-class granitic pegmatites (cf.

Èerný 1991). On the basis of the pegmatite zonality and

trace-element geochemistry of K-feldspar, the Tatric West-

Carpathian granitic pegmatites could be subdivided into three

groups: (1) simple feldspar-quartz-mica pegmatites of the

abyssal (barren) class, (2) zonal (graphicblockyequigranu-

larcore) feldspar-quartz-mica pegmatites, locally with meta-

somatic albite, of the muscovite class, and (3) zonal pegmatites

with metasomatic albite and/or quartz-muscovite zones and ac-

cessory Be, Nb-Ta minerals of the beryl-columbite subtype of

rare-element class (Dávidová 1997). The chemical composi-

tions of the studied barren and beryl-columbite granitic pegma-

tites are presented in Table 1A, B.

Methods

Zircon crystals were extracted from pegmatite samples by

crushing, sieving and concentrating in a heavy liquid. Elec-

tron-microprobe analyses were carried out in the wave-

length dispersion mode on a Cameca SX50 instrument at

the Department of Geological Sciences, University of Mani-

toba. The beam diameter of 12

m was used. An accelerat-

ing potential of 15 kV, beam current of 20 nA and counting

time of 20 s were applied for P, Si, Zr, Hf, Al, Fe, Sc, Y, Ca,

F and Cl, but 20 kV, 30 nA and 40 s, for Th, U, Ce, Sm, Tb,

Dy, Er and Yb. The following standards were used: mona-

zite (for P K

), zircon (Si K

, Zr L

), metallic Hf (Hf M

kyanite (Al K

), almandine (Fe K

), NaScSiO

(Sc K

YAG (Y L

), diopside (Ca K

), fluor-riebeckite (F K

tugtupite (Cl K

), ThO

(Th M

), UO

(U M

), REE3 (Ce

), REE2 (Sm L

, Y

), REE1 (Tb L

) and REE4 (Dy

Lb, Er L

). Data were reduced using the PAP routine (Pou-

chou & Pichoir 1985).

Some of the older data were obtained on the JEOL JCXA-

733 electron microprobe, at the Geological Survey of the

Slovak Republic, Bratislava; for analytical conditions see

Uher (1992).

The main elements of pegmatites and Rb, Sr, Ba (also Zr, Y,

Ce and Nb of sample SM-1) were analysed by XRF (Universi-

Fig. 1. Location of investigated pegmatites of the Western Carpathians. Locality abbreviations: see the Appendix.

ZIRCON IN HERCYNIAN GRANITIC PEGMATITES OF THE WESTERN CARPATHIANS 263

ty of Ottawa, Canada); Y, Ce, Zr, Hf, Nb and Ta by ICP-MS

(Memorial University of Newfoundland, St. Johns, Canada)

and Be, B, Ga and Sn by OES (Geological Institute of the Slo-

vak Academy of Sciences, Bratislava, Slovakia).

Results

Morphology and internal zoning

Zircon forms usually short prismatic crystals of the G

subtype, rarely prismatic-pyramidal G

to pure dipyramidal

A-type, or locally also L-S

1-5

(Fig. 2), according to the clas-

sification of Pupin (1980). The size of crystals is usually

0.10.5 mm, their colour is pale grey, pink to red, or brown-

ish. Three basic zoning and textural patterns of zircon could

be recognized:

(1) metamict unzoned to irregularly zoned grains with

abundant uraninite inclusions (at most of the localities, Fig.

3A, B),

(2) grains with metamict, unzoned, or irregularly zoned

central parts, locally with inclusions of uraninite, xenotime-

(Y) or monazite-(Ce), overgrown by a single or several non-

metamict zones with oscillatory compositional variations

(Fig. 3CE),

(3) semi-transparent to transparent, non-metamict crys-

tals, with oscillatory and locally sector zoning (Fig. 3F).

Chemistry

Representative compositions of zircon are shown in Table

2A, B. The most distinctive geochemical feature is the rela-

tively high abundance of hafnium as indicated by the content

of wt. % HfO

, weight Zr/Hf and atomic 100Hf/(Hf+Zr) ra-

tios. Some zircon crystals are relatively homogeneous but

others show a very broad variability in Hf contents. The Hf

concentration may also vary among crystals from a single

hand specimen. Generally, zircon from the barren pegmatites

has a lower Hf content than zircon from the beryl-columbite

bodies: 1.5 to 8.4 wt. % HfO

(average 2.98, Table 2A), ver-

sus 3.6 to 22.3 wt. % HfO

(average 6.93; Table 2B), respec-

tively. The HfO

content and atomic 100Hf/(Hf+Zr) ratio

could be (1) relatively constant across a single crystal, (2) ir-

regularly variable, or (3) increasing from the centre to the

rim. The Kamzík pegmatite zircon is an example of a very

rapid Hf-increase and two-stage growth: from ca. 3.5 to 8 wt.

% HfO

and 100Hf/(Hf+Zr) = 3.27.5 in the metamict centre

to 22 wt. % HfO

and100Hf/(Hf+Zr) = 22.1 in the oscillato-

rily zoned rim (Fig. 3C, D; Table 2B).

Locally, high P and Y+HREE abundances (up to 0.22 P and

0.18 Y+Dy+Er+Yb apfu) are introduced by heterovalent sub-

stitution (Y,HREE)

, based on the isostructural re-

lationship between xenotime-(Y) and zircon. In rare cases

elevated contents of Al (

≤

3.53 wt. % Al

, 0.13 Al apfu), Fe

(

≤

5.69 wt. % Fe

, 0.14 Fe apfu), U (

≤

2.72 wt. % UO

, 0.02

U apfu) and Ca (2.10 wt. % CaO, 0.08 Ca apfu) are observed.

The fluorine content of zircon is usually close to the analytical

detection limit (ca. 0.15 wt. % F); however, some composi-

tions from the beryl-columbite pegmatites contain 0.200.33

wt. % F, up to 0.03 apfu. The chlorine content is also below or

near microprobe detection limit (0.000.05 wt.% Cl), and only

exceptionally reaches 0.15 wt. % Cl (DU-1). In some places

the higher F and Cl contents are connected with low total com-

positions (

= 8997 wt. %) and metamict parts of zircon,

BM-3 BM-7 PI-25 SM-1

Z-3 MF-1

SiO

74.97 75.06 76.40 72.43 74.78 62.90

TiO

0.04

0.02

0.07

0.02

0.21

14.65 14.58 14.24 16.54 14.21 18.76

0.47

0.63

0.74

0.47

0.51

1.51

MnO

0.01

0.22

0.03

0.05

0.03

MgO

0.10

0.06

0.22

0.10

0.06

0.49

CaO

0.25

0.28

0.65

0.67

0.23

1.66

2.89

5.38

2.01

6.12

3.42

5.96

5.73

2.82

2.94

1.53

5.58

6.18

0.10

0.13

0.10

0.11

0.15

0.93

LOI

0.50

1.60

0.90

0.60

0.70

TOTAL

99.71 99.68 99.00 98.92 99.61 99.33

188

191

3.0 4.5

3.9 n.a. 3.1

2.1

103

379

202

302

118

2892

4.2

3.0

4.4

n.a. 3.8

5.4

16.0

19.0 n.a.

n.a. 20.2

18.4

7.44

3.47

6.57

2.00

2.40 14.50

5.16

2.34 15.83

4.00

3.21 23.62

12.85 21.11 28.19 19.00

9.33 12.81

0.48

1.22

1.32

n.a.

0.44

0.46

3.5

6.5

9.6

n.a. 1.9

<3.0

2.14

6.94

9.26 10.0

6.44

3.09

0.55

1.70

2.09

n.a.

1.16

0.35

BM-8

BM-21 PI-15

Z-5

NT-1 DU-1

SiO

79.15

76.37 79.06 71.65 74.89 70.27

TiO

0.02

0.03

0.02

0.01

0.06

0.03

12.53

13.75 12.29 16.20 14.25 15.68

0.36

0.50

0.82

0.58

0.66

0.76

MnO

0.02

0.13

0.17

0.11

0.08

MgO

0.11

0.09

0.06

0.07

0.16

0.17

CaO

0.19

0.40

0.16

0.60

0.29

0.81

3.92

3.81

2.96

6.59

4.07

6.23

2.48

3.84

2.34

2.39

4.44

3.88

0.10

0.06

0.52

0.13

0.68

LOI

1.00

0.90

0.80

0.30

TOTAL

99.88

99.88 98.84 99.52 99.83 98.89

202

184

485

146

249

281

n.a.

6.8

41.0 11.0 n.a. 12.6

142

125

283

101

n.a.

8.1

13.2

5.3 n.a.

7.0

n.a.

20.0

18.6

30.0 n.a.

43.0

1.13

21.79

0.69

7.00

2.01

5.97

1.68

8.03

0.92

3.42

4.01

7.49

9.01

19.90

5.71 23.07 11.12 41.90

0.80

0.97

0.61

2.26

0.70

4.09

n.a. 5.5 41

4.2 n.a. <3.0

0.77

7.07 45.48 17.55 25.55 13.06

0.19

0.93 11.75

4.66

4.72

6.77

Table 1A: Chemical composition of studied West-Carpathian bar-

ren granitic pegmatites (in wt.% main elements, ppm trace

elements). Locality abbreviations: see the Appendix.

Table 1B: Chemical composition of studied West-Carpathian ber-

yl-columbite granitic pegmatites (in wt.% main elements, ppm

trace elements). Locality abbreviations: see the Appendix.

-1

266 UHER and ÈERNÝ

titic zircons, the difference of T

after Hf-correction is negli-

gible, only 3 to 9

C higher for the studied pegmatites.

The temperature interval is ca. 700580

C and there are

no differences in T

between the barren and beryl-colum-

bite pegmatites (Table 3).

Discussion

Our results of zircon morphology and typology corroborate

the older data (e.g. Lyakhovich 1968; Pupin 1980): the crys-

tals are short prismatic to dipyramidal (mainly G

1-2

, rarely L

1-5

and A types) which indicate a relatively low crystalization

temperature. The pure dipyramidal {111} A-type zircon indi-

cates the lowest temperature (cf. Pupin, l.c.), it occurs only at

Moravany nad Váhom, in the most fractionated beryl-colum-

bite pegmatite in the Western Carpathians (Uher 1991; Uher &

Broska 1995). In contrast, the correlation between zircon typol-

ogy versus parent-rock composition does not work: the peralu-

minous quartz+alkali-feldspar+muscovite+(biotite) pegma-

tites contain mainly alkaline(G

, A, L

) types of zircon,

but and the clearly metaluminous blocky K-feldspar pegmatite

in Kunerad with bulk-rock A/CNK = 0.96 shows only alumi-

nous (L

) types of zircon, according to the classification of

Pupin (1980).

The chemical composition of zircon shows increasing of

Hf from the barren to the beryl-columbite pegmatites; the av-

erage 100Hf/(Hf+Zr) is 2.77 and 6.67 respectively. Our data

are in good accordance with electron microprobe zircon

compositions from the barren pegmatites of the Malé Karpaty

Mts. (Gbelský 1979). The Hf abundance in zircon tends to be

proportional to the overall fractionation level of granitoid

magmas: correlation with alkali fractionation seems to be

poor (Èerný et al. 1985). Nevertheless, the lowest Zr/Hf val-

BM-3

PI-3

SM-1

Z-3

MF-1

center

rim

center

rim

center

rim

center

rim

center

rim

0.30

0.50

n.a.

0.10

0.31

0.50

0.16

0.15

0.14

SiO

32.24

29.20

31.08

29.64

32.18

30.99

32.39

33.37

32.10

32.56

ZrO

61.52

58.57

60.64

56.19

62.82

57.54

62.27

65.26

64.68

64.19

HfO

2.65

2.51

5.94

8.42

3.94

4.51

2.72

1.80

1.57

1.59

ThO

0.00

0.09

0.01

0.00

0.02

0.16

0.61

n.a.

0.19

0.67

0.96

0.07

0.31

0.68

0.05

0.13

0.00

0.06

0.08

0.06

0.00

0.08

0.22

0.00

0.03

0.26

0.08

0.00

n.a.

0.01

0.00

0.04

0.05

0.06

0.08

0.46

0.07

0.53

0.00

0.28

0.45

0.00

0.12

0.10

0.00

0.02

0.00

0.02

0.01

0.02

0.01

0.00

n.a.

0.08

0.00

0.04

0.00

0.07

0.01

0.00

n.a.

0.00

0.02

0.00

0.01

0.00

n.a.

0.02

0.00

0.10

0.08

0.00

0.06

0.03

0.05

n.a.

0.00

0.11

0.12

0.00

0.07

0.04

0.05

0.08

n.a.

0.00

0.04

0.14

0.03

0.05

CaO

0.08

0.27

0.01

0.06

0.00

0.15

0.02

0.00

0.03

0.05

n.a.

0.07

0.06

0.05

0.00

0.07

0.02

0.01

n.a.

0.02

0.06

0.01

0.00

0.01

0.00

Total

97.29

92.66

97.74

94.84

99.49

95.04

100.04

100.83

99.20

99.59

FORMULAE BASED ON 16 OXYGEN ATOMS

0.032

0.057

0.011

0.034

0.052

0.016

0.015

4.057

3.907

3.986

3.973

4.007

4.042

4.002

4.048

3.984

4.019

3.775

3.822

3.792

3.672

3.814

3.660

3.751

3.860

3.915

3.864

0.095

0.096

0.217

0.322

0.140

0.168

0.096

0.062

0.056

0.000

0.003

0.000

0.001

0.004

0.018

0.005

0.019

0.026

0.002

0.009

0.019

0.007

0.021

0.000

0.009

0.012

0.009

0.000

0.008

0.022

0.000

0.003

0.026

0.007

0.000

0.001

0.000

0.004

0.005

0.006

0.005

0.033

0.005

0.038

0.000

0.019

0.030

0.000

0.008

0.007

0.000

0.001

0.000

0.001

0.000

0.001

0.000

0.003

0.000

0.002

0.000

0.003

0.000

0.001

0.000

0.001

0.000

0.004

0.003

0.000

0.002

0.001

0.002

0.000

0.005

0.000

0.003

0.002

0.003

0.000

0.002

0.005

0.001

0.002

0.011

0.039

0.001

0.009

0.000

0.021

0.003

0.000

0.004

0.020

0.021

0.028

0.025

0.020

0.000

0.027

0.004

0.002

0.004

0.013

0.002

0.000

0.002

0.000

15.976

15.977

16.000

15.968

15.962

15.978

16.000

15.998

15.973

å cat.

7.997

8.020

8.002

8.014

7.994

8.008

7.999

7.998

8.001

7.997

Zr/Hf

20.3

20.4

8.91

5.82

13.9

11.1

20.0

31.6

36.0

35.2

Hf# %

2.45

5.41

8.06

3.54

4.39

2.50

1.58

1.41

1.43

Table 2A: Representative compositions of zircon from studied West-Carpathian barren granitic pegmatites (in wt.%). Sample abbrevia-

tions and locations: see the Appendix. Zr/Hf

weight ratio, Hf# % = 100Hf/(Hf+Zr) atom.

ZIRCON IN HERCYNIAN GRANITIC PEGMATITES OF THE WESTERN CARPATHIANS 267

BM-8

PI-15

Z-5

DU-1

center

rim1

rim2

rim3

center

rim

center

rim

center

rim

0.94

0.34

0.17

0.05

3.86

0.20

0.16

0.12

0.14

0.61

SiO

31.12

31.69

32.01

31.00

23.23

29.14

31.26

30.57

31.65

29.31

ZrO

59.07

53.69

50.05

46.10

49.16

52.79

58.64

54.00

56.10

49.00

HfO

5.45

13.23

17.53

22.31

3.90

10.91

6.35

11.27

9.55

14.17

ThO

0.04

0.11

0.10

0.00

0.11

0.09

0.03

0.00

0.36

0.34

0.29

1.84

1.55

0.68

0.40

0.51

1.39

0.18

0.10

0.05

0.08

1.09

0.01

0.03

0.01

0.00

0.03

0.20

0.04

0.08

0.03

1.96

0.03

0.11

0.12

0.63

1.11

0.00

0.01

0.00

0.04

0.00

0.01

0.00

0.03

0.08

0.17

0.00

1.68

0.00

0.07

0.00

0.55

0.02

0.01

0.14

0.15

0.04

0.01

0.00

0.01

0.11

0.09

0.00

0.11

0.00

0.01

0.03

0.00

0.04

0.05

0.00

0.01

0.00

0.05

0.00

0.32

0.08

0.07

0.00

0.05

0.08

0.09

0.05

0.07

0.22

0.09

0.12

0.10

0.17

0.25

0.02

0.00

0.03

0.17

0.15

0.03

0.01

0.07

CaO

0.07

0.01

0.04

0.01

1.05

0.03

0.01

0.02

0.08

0.20

0.00

0.09

0.00

0.22

0.04

0.03

0.00

0.06

0.14

0.00

0.03

0.00

0.08

0.04

0.01

0.15

0.05

Total

97.73

99.81

100.53

99.99

89.11

95.41

97.64

96.64

99.13

96.95

FORMULAE BASED ON 16 OXYGEN ATOMS

0.101

0.037

0.019

0.006

0.462

0.023

0.017

0.013

0.015

0.069

3.953

4.066

4.136

4.127

3.282

3.964

4.020

4.045

3.944

3.659

3.359

3.153

2.993

3.387

3.501

3.677

3.484

3.496

3.215

0.198

0.485

0.647

0.848

0.157

0.424

0.233

0.426

0.348

0.544

0.001

0.003

0.000

0.004

0.003

0.001

0.000

0.010

0.009

0.058

0.047

0.019

0.012

0.015

0.042

0.027

0.015

0.008

0.013

0.182

0.002

0.005

0.002

0.000

0.005

0.019

0.004

0.008

0.003

0.208

0.003

0.011

0.012

0.061

0.112

0.000

0.001

0.000

0.005

0.000

0.001

0.000

0.003

0.009

0.011

0.000

0.126

0.000

0.005

0.000

0.039

0.001

0.000

0.007

0.002

0.000

0.005

0.004

0.000

0.005

0.000

0.001

0.000

0.002

0.000

0.002

0.000

0.015

0.004

0.003

0.000

0.002

0.003

0.004

0.002

0.003

0.010

0.004

0.005

0.004

0.007

0.011

0.001

0.000

0.001

0.007

0.006

0.001

0.000

0.003

0.010

0.001

0.006

0.001

0.159

0.004

0.001

0.003

0.011

0.029

0.000

0.037

0.000

0.098

0.017

0.012

0.000

0.024

0.060

0.000

0.007

0.000

0.019

0.009

0.002

0.032

0.011

16.000

15.963

15.957

16.000

15.883

15.974

15.986

15.998

15.943

15.929

å cat.

7.995

7.989

7.992

8.004

8.076

7.998

8.001

8.002

8.007

8.025

Zr/Hf

9.46

3.54

2.49

1.80

11.0

4.22

8.06

4.18

5.13

3.02

Hf# %

5.13

12.6

17.0

22.1

4.43

10.8

5.96

10.9

9.05

14.5

Table 2B: Representative compositions of zircon from studied West-Carpathian beryl-columbite granitic pegmatites (in wt.%). Sample

abbreviations and locations: see the Appendix. Zr/Hf

weight ratio, Hf# % = 100Hf/(Hf+Zr) atom.

ues are found in zircon from the complex Li,Cs,Ta-rich rare-

element pegmatites, e.g. Zambézia area, Mozambique (up to

hafnon, Correa Neves et al. 1974; Törnroos 1982, 1985),

Tanco, Canada (Èerný & Siivola 1980), Mixeriqueira, Bra-

sil (Cassedanne et al. 1985) or from highly evolved Li, Sn,

Nb, Ta, F-rich granites, e.g. Beauvoir, France (Wang et al.

1992), Central Eastern Desert, Egypt (Renno 1995) and

Suzhou, China (Wang et al. 1996). However, the maximum

Hf-values in zircon from relatively primitive beryl-colum-

bite the Kamzík pegmatite (2022 wt. % HfO

) exceed the

Hf-content in zircon from the Tanco as well as some Zam-

bézia district complex pegmatites with up to 18 and 21 wt.

% HfO

, respectively (cf. Èerný & Siivola l.c., Törnroos

l.c.). This could be explained by a local extreme fraction-

ation of hafnium, accumulated in very thin (< 50

m) outer

zones; the Tanco zircon is largely homogeneous in this re-

spect (Èerný & Siivola 1980). However, the Col Dret pegma-

tite from France is another example of Hf-rich zircon (up to

26 wt. % HfO

) in a relatively less evolved beryl-columbite

pegmatite (Fontan et al. 1980).

The substitution diagrams (Fig. 4AD) show possible

mechanisms of iso- and heterovalent isomorphous substitu-

tions from the routine HfZr

-1

to the xenotime- (Y,HREE,

Fe)

(Zr,Hf)

and berlinite-type Al

substi-

tution. All these substitutions are close to the 1:1 substitution

vector with high correlation coefficients R = 0.780.94.

The calculation of zircon saturation temperature (T

) was

previously applied mainly to granites (Watson & Harrison

1983), not to pegmatites. Experimental data were obtained

only for temperatures above 700

C; however, Watson and

Harrison expected a linear extrapolation of the saturation line

for t < 700

C. Thus, it is also possible to calculate meaningful

for granitic pegmatites. Our T

= 700 to 590

C are in good

accordance with experimental data on pegmatite solidifica-

-1

-2

268 UHER and ÈERNÝ

Fig. 4. Substitution diagrams of zircon, atoms per formula unit (apfu). A HfZr

-1

; B and C (Y,HREE,Fe)

(Zr,Hf)

; D

. The diagonal lines indicate 1:1 substitution vector.

stage evolution is observed with metamict Hf-poor central zone

and oscillatorily zoned, transparent, Hf-rich outer zone.

(2) The Hf contents of zircon from the more primitive,

barren pegmatites are lower than those in zircon from more

evolved, beryl-columbite bodies. A local extreme fraction-

ation at the end of zircon crystallization led to the crystalli-

zation of thin oscillatory zones (1050

m) very enriched in

Hf (822 wt. % HfO

(3) A good positive correlation between P and Y+HREE

indicates limited incorporation of the isostructural compo-

nent of xenotime-(Y); possible substitution mechanisms

are: HfZr

-1

, (Y,HREE,Fe)

(Zr,Hf)

and Al

tion (cf. London 1992). In addition, our results for zircon so-

lidification correspond to the crystallization interval of ho-

mogeneous K-feldspar in coexistence with albite-oligoclase

(T = 625 to 565

C) for the feldsparsquartzmica zone of

the Povaský Inovec pegmatites, Western Carpathians

(Dávidová 1994).

Conclusions

(1) Zircon shows variable internal structures; crystals are un-

zoned, and irregularly or oscillatorily zoned. Locally, a two-

-1

-2

-1

-2

-1

0.1

0.2

0.3

0.7

0.8

0.9

Zr apfu

Hf apfu

0.1

0.2

0.75

0.85

0.95

Zr+Hf apfu

Y+HREE+Fe apfu

0.1

0.2

0.3

0.7

0.8

0.9

1.1

Si apfu

0.1

0.2

0.3

0.7

0.8

0.9

1.1

Si apfu

Al+

ZIRCON IN HERCYNIAN GRANITIC PEGMATITES OF THE WESTERN CARPATHIANS 269

(4) The application of saturation temperature (T

) to zircon

from granitic pegmatites, gave realistic results of ca. 700 to

580

C, which are in accordance with other experimental data

as well as previous two-feldspar geothermometry results.

Acknowledgements: This study was supported by the

NSERC Research Grant and Major Installation Grant #311-

1727-17 to PÈ, by the Dean of Science, University of Mani-

toba (Winnipeg, Canada) a Post-Doctoral Fellowship to PU

and by the Scientific Grant Agency (VEGA) of the Ministry

of Education of the Slovak Republic and the Slovak Acade-

my of Sciences, Grant #4078 to Igor Petrík (Geological Inst.,

Slovak Acad. Sci., Bratislava). Constructive comments by

Igor Broska (Geological Inst., Slovak Acad. Sci., Bratislava)

and assistance by Ron Chapman, Frantiek Caòo, Marián

Dubík, Karol Horák and Ivan Holický during microprobe and

SEM work are gratefully acknowledged. We also thank Ron

Hartree, Mike Tubrett and ¼ubica Pukelová for XRF, ICP-

MS and OES results.

Appendix: Sample locations, (Be)-beryl-, (CT)-

columbite-tantalite-bearing pegmatites:

BM-1: quartz-feldspars-muscovite-(CT) pegmatite. Bratislava, Kramer

quarry, Malé Karpaty Mts.

BM-3: quartz-feldspars-muscovite-biotite pegmatite. Bratislava, Rössler

quarry, Malé Karpaty Mts.

BM-7: saccharoidal albite-quartz-muscovite pegmatite. Bratislava, Kam-

zík Hill A, Malé Karpaty Mts.

BM-8: quartz-feldspars-muscovite-(Be, CT) pegmatite. Bratislava, Kam-

zík Hill B, Malé Karpaty Mts.

BM-21: quartz-feldspars-muscovite-(Be) pegmatite. Bratislava, Dúbrav-

ka, E of vábsky Hill, Malé Karpaty Mts.

PI-3: quartz-feldspars-muscovite pegmatite. Praice, Duchonka,

So¾nisko Hill, Povaský Inovec Mts.

PI-15: quartz-feldspars-muscovite-(Be, CT) pegmatite. Moravany nad

Váhom, Striebornica Ridge, Povaský Inovec Mts.

PI-15Ab: saccharoidal albite-quartz-muscovite-(CT) pegmatite. Mora-

vany nad Váhom, Striebornica Ridge, Povaský Inovec Mts.

PI-22: quartz-feldspars-muscovite pegmatite. Bojná, Hradná Valley,

southern quarry, Povaský Inovec Mts.

PI-25: quartz-feldspars-muscovite pegmatite. Podhradie, eleznica Val-

ley, W of Hrabový Hill, Povaský Inovec Mts.

SM-1: quartz-feldspars-muscovite pegmatite. Valaská Belá, Ve¾ké Bystré

forest, SuchýMalá Magura Mts.

Z-3: quartz-feldspars-muscovite-(Be) pegmatite. Sklené, quarry at S

slope of Háj Hill, iar Mts.

Z-5: saccharoidal albite-quartz-muscovite-(CT) pegmatite. Ráztoèno,

forest over Uhlisko gamekeepers lodge, iar Mts.

MF-1: K-feldspar blocky pegmatite. Kunerad, Kunerad Valley, Malá

Fatra Mts.

S2A: Quartz-feldspars-muscovite-(CT) pegmatite. Brusno, Sopotnica

Valley, Nízke Tatry Mts.

S2B: Quartz-feldspars-(CT) pegmatite. Brusno, Sopotnica Valley, Nízke

Tatry Mts.

NT-1: Quartz-feldspars-muscovite-(Be, CT) pegmatite. Brusno, E of

Ve¾ká Chochu¾a Hill, Nízke Tatry Mts.

NT-4: Quartz-feldspars-muscovite-(CT) pegmatite. Dúbrava, PA-9Z

adit, antimony deposit, Nízke Tatry Mts.

DU-1: Quartz-feldspars-biotite-(Be, CT) pegmatite. Dúbrava, dumps of
the antimony deposit, Nízke Tatry Mts.

References

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Table 3. Zircon saturation temperatures (T

) of the studied West-

Carpathian pegmatites.

Sample T

(° C)

Bratislava, Rössler Quarry (BM-3)

611

Bratislava, Kamzík Hill A (BM-7)

645

Bratislava, Kamzík Hill B (BM-8)

603

Bratislava, Dúbravka (BM-21)

646

Moravany, Striebornica (PI-15)

585

Podhradie, eleznica Valley (PI-25)

694

Valaská Belá, Ve¾ké Bystré (SM-1)

624

Sklené, Háj Quarry (Z-3)

596

Ráztoèno, Uhlisko (Z-5)

644

Kunerad, Kunerad Valley (MF-1)

585

Brusno, Ve¾ká Chochu¾a Hill (NT-1)

606

Dúbrava, Sb-deposit, dumps (DU-1)

673