GeolCarp_Vol48_No5_303

GEOLOGICA CARPATHICA, 48, 5, BRATISLAVA, OCTOBER 1997

303–313

U-Au-Co-Bi-REE MINERALIZATION IN THE GEMERIC UNIT

(WESTERN CARPATHIANS, SLOVAKIA)

IGOR ROJKOVIČ

, MILAN HÁBER

and LADISLAV NOVOTNÝ

Faculty of Sciences, Comenius University, Mlynská dolina, 842 15 Bratislava, Slovak Republic

Geological Institute, Slovak Academy of Sciences Bratislava, Branch: Severná 5, 974 01 Banská Bystrica, Slovak Republic

URANPRES, Spišská Nová Ves, Slovak Republic

(Manuscript received November 28, 1996; accepted in revised form March 18, 1997)

Abstract:

Uranium mineralization occurs in a quartz vein with gold and REE minerals. The vein cuts the Early

Paleozoic rocks in the proximity of the granite body of the Humel Massif. The mineralization is represented by
uraninite, brannerite, arsenopyrite, pyrite, glaucodot, gold, galena, bismuth, bismuthinite, xenotime-(Y), rutile, sericite,
chlorite, apatite, monazite-(Ce) and tourmaline. Secondary minerals are represented by goethite, trögerite, zeunerite
and scorodite.

Key words:

Gemeric Unit, Early Paleozoic, quartz vein, U-Au-Co-Bi-REE minerals, element association.

Introduction

The mineralization was found 5.3 km south of Prakovce vil-
lage and 1.6 km east of Ovčinec Hill 1011.7 m, 100–200 m
north from main range of the Slovenské rudohorie Mts., at the
end of Zimná Voda Valley (Fig. 1). Gold was found in 1975
(Novotný & Čížek 1979) during prospecting for uranium
mineralization. Detailed prospecting for gold was made in
1992–95. Uranium mineralization associated with gold was
also found near Hnilec Granite in the Peklisko locality (Roj-
kovič & Novotný 1993).

Geological setting

The Early Paleozoic rocks are represented mostly by phyl-

lites and metatuffs of rhyolite in the area studied. Sediments
are represented by quartz-(chlorite)-sericite phyllite, meta-
quartzite, black phyllite and lydite. They belong to the Siluri-
an Bystrý Potok Formation of the Gelnica Group underlying
the Devonian Rakovec Group (Bajaník et al. 1981; Bajaník et
al. 1984; Ivanička et al. 1989). The Gelnica Group of the Ge-
meric Unit is characterized by a polygenetic and polycyclic
sedimentary history. It was formed by mesorhythmic sedi-
mentation of sandstone and claystone accompanied by acid
volcanism (Vozárová & Ivanička 1993). The age of the volca-
nism according to U-Pb dating of zircon from metarhyolite is
403 Ma (Cambel et al. 1990). The upper parts of the meso-
rhythms contain carbonates and lydite. According to Grecula
(1982), the Gelnica and Rakovec Groups represent a synchro-
nous development of the Early Paleozoic sedimentary basin
in the Volovec Group divided into the Betliar, Smolník and
Hnilec Formation and surrounding rocks of the mineraliza-
tion studied belong to the Betliar Formation of the Humel
Nappe. The Early Paleozoic sequences are metamorphosed
mostly in the chlorite zone of the green schist facies (Faryad
1991). The Gemeric Granite intruded into these sequences.
They are from 270 to 246, or 223 Ma old according to Rb-Sr
dating (Kovách et al. 1986; Cambel et al. 1990).

The quartz vein was found in two outcrops in a distance of

250 m from each other. The rocks in places underwent contact
metamorphism affected (Faryad 1991) by near (ca. 600 m) apo-
physis of the Humel Massif Granite (Figs. 1, 2).

Fig. 1.

Localization of Zimná Voda. Geology adapted after Bajaník et

al. (1984): 1 — metalydite, 2 — black phyllite, 3 — quartz-sericite
phyllite with black phyllite, 4 — metatuffite of rhyolite, 5 — meta-
quartzwacke with quartz phyllite and quartzite, 6 — coarse-grained
metaquartzwacke, 7 — Humel Granite Massif, 8 — zone of contact
metamorphosed rocks, 9 — faults, 10 — outcrops of vein.

304 ROJKOVIČ, HÁBER and NOVOTNÝ

U-Au mineralization is bound to parallel veinlets forming

stockwork up to 1 m thick, with an E-W direction, dipping 60–80

to the south in an outcrop with a length of only 30 m in the east-
ern occurrence of the vein. Wall rocks are represented by closer
grey-green psammitic phyllite and by sericitic metaquartzite.
Veinlets from 1 to 5 cm across are formed by fine-grained
brownish quartz with disseminated uraninite or torbernite.

The vein was confirmed by trenches in the length of 83 m

in the western part. Beyond this, it is cut by faults and its
continuation was not found yet. The vein is cut in depth of 5–
15 m by parallel fault as was confirmed by shallow drilling.
The extension of displacement in the underlying part of the
vein is not known (Fig. 2). The dominant wall rock is light
green sericitic phyllite with local light green fine-grained
sericitic metaquartzite or greenish-grey metagreywacke. Its
schistosity dips from 40

to 60

towards the north. The quartz

vein with an E-W direction dips 60–75

towards the south,

and measures from 5 to 30 cm across (10 cm in average). The
ore minerals including gold form irregular small local accu-
mulations or high-grade sections from 1 to 2 metres long in
fine-grained quartz of brown colour.

The vein is accompanied by zone of alteration from 2 to 8 m

wide represented by silicification and pyritization. Short
quartz veinlets of white colour from 5 to 15 cm across oriented
in conformity with the schistosity of the rocks also occur in
this zone. This quartz is accompanied only by rare pyrite. Au
content in these veinlets varies from 0.17 to 0.51 ppm in dis-
tance up to 2 m from the main vein.

Methods used

The radioactivity of uranium minerals enables easy localiza-

tion of the vein and sampling of high-grade uranium ore con-
taining gold. Polished sections for X-ray microanalysis and
thin sections were made. Ore and rock-forming minerals were

studied by polarized microscope in transmitted as well as in re-
flected light and by scanning electron microscope (SEM). Dis-
tribution and textures of minerals were studied in vein as well
as in wall rock. They were analyzed by wave-dispersion X-ray
microanalysis (WDX), energy-dispersion X-ray microanalysis
(EDX) and by X-ray diffraction analysis (XRD). Quantitative
analyses of minerals were made by the JEOL JXA-733 Super-
probe and KEVEX DELTA using voltage 20 kV, current 20
nA(WDX) and 1.2 nA (EDX), beam diameter 3–5

m. All anal-

yses were corrected by ZAF-correction of Kevex Sesame and
Kevex Quantex software. Metal, sulphides and oxides of similar
chemical composition were used as standards.

The following analytical methods were used for geochemi-

cal characteristic of mineralization:
— chemical wet analysis and X-ray fluorescence analysis
(XFA) for major and minor elements of the rocks,
— P

by colorimetry,

— Rock-Eval pyrolysis for C

org

— atomic emission spectroscopy with induction coupled plas-
ma (AES-ICP) for the rare earth elements (REE),
— optical emission spectroscopy (OES) for the others ele-
ments.

Mineralogical characteristic

Uranium minerals and gold disseminated in brownish quartz

are visible to the naked eye in some places in the vein. Ura-
ninite, brannerite and arsenopyrite are the main ore minerals
disseminated in fine-grained quartz. They are accompanied by
pyrite, glaucodot, gold, galena, bismuth, bismuthinite, tetrahe-
drite, molybdenite, xenotime-(Y), monazite-(Ce), rutile, seric-
ite, chlorite, apatite and tourmaline.

Uraninite

is the main uranium mineral. Its surface is

often rough and porous. It forms colloform botryoidal aggre-
gates or concentric zonal aggregates (around 1 mm across) vis-

Fig. 2.

Western section of the vein. 1 — metaquartzite, 2 — phyllite, 3 — altered rock, 4 — ore vein, 5 — secretion veins, 6 — fault, 7 —

cleavage.

U-Au-Co-Bi-REE MINERALIZATION IN THE GEMERIC UNIT 305

ible macroscopically (Figs. 3, 4). Synaeresis fissures can often
be observed. Uraninite is closely associated with brannerite.
Concentric colloform aggregates are rimmed, enclosed and
filled with younger brannerite, xenotime-(Y), pyrite and arse-

Fig. 5.

Radial aggregate of brannerite crystals (grey) overgrowing

on zonal uraninite (white) in quartz (black). ZV 1a, SEM-BEI.

Weight %

Sample

Total

84.8

15.2 100.0

ZV 1.1

85.2

1.5

0.6

12.8 100.1

ZV 1.2

80.2

1.6

0.5

0.1

0.2

0.5

11.7

94.8

ZV 1.3

79.8

1.5

0.6

0.1

0.6

11.7

94.4

ZV 1.4

78.7

1.6

0.6

0.2

0.6

11.4

93.1

ZV 1.5

76.9

1.6

1.0

0.1

0.2

0.5

11.4

91.7

Table 1:

Chemical composition of uraninite.

Fig. 3.

Spheroidal uraninite overgrown by brannerite. ZV 2, SEM

-SEI.

Fig. 4.

Spheroidal aggregate of uraninite (white) in quartz (black) is

replaced from the margin by zeunerite (light-grey). ZV 1a, SEM-BEI.

Weight %

At. prop.

Sample

Ti Fe Ca Si

Total

UTi

55.4 22.3

22.3 100.0 1.00

2.00

ZV 1.1

52.3 21.4 0.7 1.7

22.3

98.4 1.03

1.97

ZV 1.2

52.8 21.6 1.3 1.4

22.7

99.8 0.99

2.01

ZV 1.3

52.0 20.7 0.2 1.5 0.1 21.6

96.1 1.01

1.99

ZV 1.4

50.2 21.5 1.4 1.6 0.1 22.5

97.3 0.96

2.04

ZV 1.5

52.8 20.0 1.1 1.4

21.5

96.8 1.04

1.96

ZV 1.6

51.8 20.4 0.1 1.5 0.2 21.5

95.5 1.01

1.99

ZV 1.7

53.9 21.4 0.3 1.5 0.2 22.4

99.7 1.01

1.99

Table 2:

Chemical composition of brannerite and UTi

Fig. 6.

Detail of spot from Fig. 5. Brannerite (light-grey) with ad-

mixture of rutile (dark-grey), xenotime-(Y) (grey) and overgrowing
uraninite (white in upper part) is cut by veinlets of gold (white in
central lower part). ZV-1a, SEM-BEI.

nopyrite (Fig. 5). WDX analysis has confirmed besides urani-
um presence of Pb, Fe, Si, Ca and Ti in uraninite (Table 1).

Brannerite

UTi

or (U,Ca,Th,Y)[(Ti,Fe)

] is a fre-

quent and abundant uranium mineral in the vein. It can be
seen with the naked eye as black columnar crystals up to
3 mm long. Crystals often form radial aggregates (Fig. 5).
They radially overgrow uraninite. They contain inclusions of
xenotime-(Y) and rutile (Fig. 6). Chemical composition cor-
responds to the ratio U : Ti = 1 : 2 and brannerite contains ad-
mixtures of Fe, Ca and Si (Table 2).

Rutile

TiO

forms irregular xenomorphic grains (10

m up

to 0.3 mm across). They are often associated with uraninite
and xenotime-(Y). This rutile was formed due to metamicti-
zation and the following alteration of brannerite to Ti oxides,
xenotime-(Y) and uraninite (Fig. 6). The rutile accompanied

306 ROJKOVIČ, HÁBER and NOVOTNÝ

by xenotime-(Y) contains a homogeneous admixture of Fe
and an increased content of Nb (1.1 wt. % Nb; Table 3).

Arsenopyrite

FeAsS is relatively frequent and form aggre-

gates macroscopically visible with crystals of radial texture
from 1 to 5 mm long (Fig. 7). It fills interstices of the branner-
ite aggregates. Prismatic crystals and rhombic sections are vis-
ible under the polarizing microscope. Admixtures of Co, Ni
and Sb were found (Table 4). Arsenopyrite with distinctly in-
creased Co content (9 wt. %) corresponds to the Co variety of
arsenopyrite — danaite (Fig. 8).

Glaucodot

(Co,Fe,Ni)AsS forms grain aggregates and

prismatic crystals often of radial texture in quartz (Fig. 7).
They often show a cataclastic texture similar to arsenopyrite.

Skeleton-shaped crystals of glaucodot can be seen frequently.
It is lighter compared to arsenopyrite in reflected light. It
shows strong anisotropy of blue and orange colour. Fissures
of glaucodot are filled by bismuthinite, younger quartz, rarely
also by carbonate. Radial aggregates are interesting from the
genetic point of view. Euhedral cobaltite form their centre.
Transitional zone is formed by arsenopyrite and danaite. Glau-
codot forms a marginal part of the aggregate.

WDX analysis confirmed increased content of Ni in glau-

codot (comparing to data of literature). However, the total of
Fe + Ni does not exceed the Co content. The data obtained (Ta-
ble 5, Fig. 8) correspond well to a Co content from 16 to 25 %
Co given for glaucodot by Strunz (1970). Rudaschevsky in

Fig. 7.

Radial aggregate of zonal crystals of arsenopyrite and glau-

codot. The centre of the aggregate is represented by cobaltite grains,
the transitional zone by arsenopyrite and Co-arsenopyrite (danaite)
and the external part by glaucodot. Bismuthite (white) forms the rim
and veinlets in the aggregate. GR 8/2b, SEM-BEI.

Fig. 8.

Ternary diagram of Fe, Co and Ni content in arsenopyrite

(1), glaucodot (2) and cobaltite (3).

Weight %

Sample

Total

TiO

59.9

40.1

100

ZV 1

58.7

0.5

1.1

39.7

100

Weight %

Sample

Total

ZV-1

38.6 0

38.8

22.7

100.1

ZVH-1

34.8

0.8 0

45.4

18.9

99.9

ZVH-2

32.8

1.7

0.1

45.5

20.1

100.2

ZVH-3

32.9

1.9

0.1

45.2

19.6

99.7

ZVH-4

33.0

2.1

0.2

0.4

46.0

19.0

100.7

ZVH-5

32.7

2.1

0.2

0.7

45.7

19.5

100.9

ZVH-6

29.7

4.8

0.4

45.1

19.0

99.0

ZVH-25*

27.2

4.9

0.6

1.0

49.3

15.9

98.9

ZVH-26*

28.7

5.2

0.3

46.1

18.9

99.2

ZVH-24*

26.6

6.8

0.5

47.4

17.3

98.6

ZVH-23*

25.5

8.0

0.8

46.5

18.1

98.9

ZVH-22*

24.4

8.9

0.7

49.2

17.5

100.7

ZVH-7

23.4

9.1

2.0

47.9

18.7

101.1

ZVH-21*

23.1 10.6

0.4

46.5

18.3

98.9

Atomic proportion on 3 atoms

ZV-1

1.08 0

0.81

1.10

ZVH-1

1.02

0.02 0

1.00

0.97

ZVH-2

0.95

0.05 0

0.98

1.01

ZVH-3

0.96

0.05 0

0.98

1.00

ZVH-4

0.96

0.06

0.01

1.00

0.97

ZVH-5

0.95

0.06

0.01

0.99

ZVH-6

0.88

0.13

0.01 0

0.99

0.98

ZVH-25*

0.84

0.14

0.02

0.01

1.13

0.85

ZVH-26*

0.85

0.15

0.01 0

1.02

0.98

ZVH-24*

0.81

0.20

0.01 0

1.07

0.91

ZVH-23*

0.76

0.23

0.02 0

1.04

0.95

ZVH-22*

0.72

0.25

0.02 0

1.09

0.91

ZVH-7

0.69

0.25

0.06 0

1.05

0.95

ZVH-21*

0.69

0.30

0.01 0

1.04

0.96

*transitional zone of radial aggregate (see Fig. 7)

Table 3:

Chemical composition of rutile.

Table 4:

Chemical composition of arsenopyrite and Co-arseno-

pyrite (danaite).

U-Au-Co-Bi-REE MINERALIZATION IN THE GEMERIC UNIT 307

Borischanskaya et al. (1981) gives for glaucodot ratio of
Fe : Co from 65 : 35 to 35 : 65. It corresponds to a Fe content
from 11.86 to 22.15 wt. % and Co content from 12.58 to 23.24
wt. % Co. Ratio of Fe : Co from 65 : 35 to 100 : 0 correspond-
ing to less than 11.86 wt. % of Fe and from 23.24 to 35.41
wt. % of Co is given by Rudaschevsky in Borischanskaya et al.
(1981) for alloclasite. The zonality of grains not visible under
the polarizing microscope can be observed only with the scan-
ning electron microscope and it was confirmed by WDX anal-
ysis (Table 5). Increase of cobalt in external zones was ob-
served in the zonal aggregates of glaucodot. The central zone
shows a low content of Co in glaucodot due to the cobalt bond
in cobaltite. Variability of chemical composition is document-
ed in the ternary diagram of Co-Fe-Ni sulphoarsenides (Fig. 8).

Cobaltite

CoAsS forms irregular grain aggregates, rarely

euhedral grains in the centre of radial aggregates of Co-Fe-Ni
sulphoarsenides (Fig. 7). It shows high reflectivity, pinkish
white colour and isotropy. Its chemical composition is docu-
mented in Table 6 and the ternary diagram in Fig. 8.

Pyrite

FeS

forms rounded grains (up to 0.3 mm across) and

their aggregates. Intergrowths of octahedral and pentagonal
dodecahedron crystals are rare. They are more abundant in the
external part of the vein with a decreased content of arsenopy-
rite, gold and uranium minerals.

Gold

Au. Gold is visible even with the naked eye in the

high-grade ore in the western section of the vein. It was found
only after separation in the sample from the western part of the
vein (135 grains). Grains from 2 to 100

m (rarely up to

400

m) can be observed under the polarizing microscope.

The grains are oval, lobe-form or they fill fissures and inter-
granular space in older minerals. Section across octahedral
crystals can rarely be seen (Figs. 9, 10). It occurs in quartz,
uraninite, brannerite and rarely also in arsenopyrite, glaucodot
and bismuthinite (Fig. 9). It overgrows, encloses and cuts pre-
vious minerals. For example uraninite from sample GR-6a/11
of 0.104 g weight contains 0.56 g.t

-1

Au. Intergrowths of ura-

ninite and arsenopyrite from sample GR-6a/13 of 0.089 g
weight contain 5.31 g.t

-1

. The largest grains (over 100

m), in

oxidation products of the vein with abundant goethite and
scorodite, are most probably of supergene origin. The content
of the gold ranges from 773 to 999/1000 (Table 7a–b, Fig. 11).

Distribution of gold was also studied during the dressing.

The abundance of gold grains, their size, composition and
form were studied after grinding and separation (Table 8).
The surface of the grains is different: flakes, sinuous, smooth
or, elongated lobe-likes, isometric grains, rarely euhedral of
octahedral form (Fig. 10).

Bismuth

occurs rarely. It is associated with bismuthinite in in-

tergranular space of glaucodot as irregular grains up to 50

across. Content of 99.8 wt. % Bi was confirmed by EDX analysis.

Bismuthinite

is mostly associated with glaucodot. It

forms needle-like and tabular crystals in quartz (Fig. 12) or
more frequently it fills fissures or intergranular space of aggre-
gates of Co-Fe-Ni sulphoarsenides (Fig. 13). It shows reflec-
tivity close to galena in the polarizing microscope, white co-
lour and strong anisotropy. Prismatic sections also show
longitudinal cleavage. An increased content of Sb (up to
11.6 wt. %) was observed. Its composition is close to horo-
betsuite. An increased content of Pb (up to 5.5 wt. %) was

Weight %

Sample

Total

ZVH-8

8.0

16.3

10.8

46.7

19.2

101.0

ZVH-9

7.5

18.3

8.9

44.2

19.2

98.1

ZVH-10

7.7

18.6

8.9

45.3

18.5

99.0

ZVH-11

7.6

18.9

9.4

45.4

18.4

99.7

ZVH-12

6.7

19.8

8.2

47.1

19.7

101.5

ZVH-13

7.0

20.0

8.8 0.1

46.0

17.7

99.6

ZVH-14

6.9

21.4

8.0

46.5

18.2

101.1

ZVH-15

6.8

22.3

6.5

46.6

19.2

101.4

ZVH-16

6.0

22.9

6.9

45.3

19.5

100.6

ZVH-17

7.9

23.9

5.8

45.3

17.1

100.0

ZVH-20*

6.0

24.0

5.8

45.6

19.2

100.6

ZVH-18

5.6

24.1

6.0

46.2

18.5

100.4

ZVH-19

5.3

24.5

5.6

45.6

18.6

99.6

Atomic proportion on 3 atoms

ZVH-8

0.24

0.46

0.30

1.03

0.98

ZVH-9

0.23

0.52

0.25

0.99

1.01

ZVH-10

0.23

0.53

0.25

1.02

0.97

ZVH-11

0.23

0.54

0.27

1.01

0.96

ZVH-12

0.20

0.55

0.23

1.03

1.00

ZVH-13

0.21

0.57

0.25

1.03

0.93

ZVH-14

0.20

0.60

0.23

1.03

0.94

ZVH-15

0.20

0.62

0.18

1.02

0.98

ZVH-16

0.18

0.64

0.19

0.99

1.00

ZVH-17

0.24

0.68

0.17

1.02

0.90

ZVH-20*

0.18

0.67

0.16

1.00

0.99

ZVH-18

0.17

0.68

0.17

1.02

0.96

ZVH-19

0.16

0.70

0.16

1.01

0.97

*marginal zone of radial aggregate (see Fig. 7)

Weight %

Sample

Total

ZVH-28*

28.2

4.0

45.1

19.0

100.3

ZVH-27*

29.7

3.4

2.6

45.1

18.7

99.5

ZVH-29*

29.9

3.6

2.6

44.9

19.2

100.2

ZVH-30*

30.2

3.2

2.3

46.3

19.2

101.2

Atomic proportion on 3 atoms

ZVH-28*

0.79

0.12

0.11

1.00

0.98

ZVH-27*

0.84

0.10

0.07

1.01

0.98

ZVH-29*

0.84

0.11

0.07

0.99

ZVH-30*

0.84

0.09

0.06

1.01

0.98

*central zone of radial aggregate (see Fig. 7)

Table 5:

Chemical composition of glaucodot.

Table 6:

Chemical composition of cobaltite.

also found. Chemical composition is documented by Table 9
and by a ternary diagram of Bi–Sb–Pb minerals (Fig. 14).

Molybdenite

MoS

was found only as a rare mineral. Dis-

seminated flakes of molybdenite in quartz are up to 20

long and up to 5

m across. It is closely associated with arse-

nopyrite and uraninite. In spite of the small size of grains,
WDX analysis has confirmed the identification of molybden-
ite (Table 10).

308 ROJKOVIČ, HÁBER and NOVOTNÝ

Fig.10.

Separated gold grains from sample GR-6a-12/4. A frag-

ment of gold octahedron can be seen on the left in the upper part.
SEM-SEI.

Fig. 11.

Correlation plot of Au and Ag in gold.

Weight %

Atomic propor. on 1000

Sample Au

Ag Hg Cu Bi Total Au Ag Hg Cu Bi

ZV 1.1

92.9 3.1 2.6 0

0.9

99.5 911

ZV 1.2

95.2 2.7 2.0

0.3 0.4

100.6 921

ZV 1.3

94.3 3.0 2.4

0.1 0.6

100.4 915

ZV 1 h

93.2 5.7 0.5 0

99.4 896

ZV 2 h

91.6 5.7 0.9 0

98.2 890

101

ZV 3 h

86.4 10.7 1.7 0

98.8 803

181

ZV 4 h

91.2 5.7 0.6

0.3

97.8 884

100

ZV 5 h

96.5 3.5 0.8

0.2

101.0 924

ZV 6 h

92.7 5.4 0.6

0.3

99.0 890

At.p./1000

Sample

Total

ZV 1.4

98.7

1.3

100.0

977

ZV 1.5

98.9

1.2

100.1

978

ZV 1.6

99.0

1.1

100.1

980

ZV 7 h

97.7

2.3

100.0

959

ZV 8 h

97.8

2.2

100.0

961

ZV 9 h

85.8

13.4

99.2

778

222

ZV 10h

85.9

13.8

99.7

774

226

ZV 11h

93.8

6.2

100.0

893

107

ZV 12h

99.9

0.1

100.0

999

ZV 13h

89.8

10.2

100.0

828

172

ZV 14h

93.1

7.0

100.1

880

120

ZV 15h

91.1

8.9

100.0

849

151

ZV 16h

97.3

2.7

100.0

952

ZV 17h

92.5

7.5

100.0

871

129

ZV 18h

96.9

2.7

99.6

951

ZV 19h

98.0

2.0

100.0

964

ZV 20h

87.0

14.0

101.0

773

227

ZV 21h

93.5

5.6

99.1

901

ZV 22h

90.5

9.6

100.1

838

162

ZV 23h

92.1

7.9

100.0

864

136

Table 7a:

Chemical composition of gold (WDX analyses).

Table 7b:

Chemical composition of gold (EDX analyses).

Sample

gold

size of

form of gold

grains

grains (

m) on 1000

GR-6a/11

30-300

910-920

flakes, isometric

GR-6a/12

30-200

860-970

grains, elongated

GR-6a/13

30-150

860-990 lobe-like, sinuous

Table 8:

Distribution of gold separated from ground samples.

Fig. 9.

Section of octahedral crystal of gold (white) in uraninite

(grey). ZV 1b, SEM-BEI.

Galena

PbS small rare grains have been found in quartz in as-

sociation with bismuthinite with increased Pb content (Fig. 12).

Tetrahedrite

is rare. It forms irregular grain

aggregates and veinlets in quartz associated with arsenopy-
rite. Its chemical composition is documented by Table 11.

Apatite

[F|(PO

)

] forming short columnar crystals

(0.1

0.08 mm) accompanies ore minerals, sericite (aggre-

gates up to 1 mm across) and chlorite in the quartz vein.

Xenotime-(Y)

Y[PO

] can be observed as small admix-

tures in brannerite (Fig. 6). It fills fissures and cavities of con-
centric colloform aggregates of uraninite accompanied by
brannerite and quartz (Fig. 15). Besides the dominant ele-
ments (Y and P) the heavy rare earth elements (HREE) from
Gd to Yb with ionic radii close to Y are present (Table 12).

U-Au-Co-Bi-REE MINERALIZATION IN THE GEMERIC UNIT 309

Fig. 12.

Tabular bismuthinite with small grains of galena (marked

with arrow) in quartz. GR 8/2b, SEM-BEI.

Fig. 13.

Bismuthite in intergranular space and fissures of zonal ar-

senopyrite and glaucodot. GR 4/2, SEM-BEI.

Fig. 14.

Ternary diagram of Bi, Sb and S in bismuth (1), bismuth-

inite (2) and Sb-bismuthinite (3).

There is a higher proportion of uranium than thorium in
xenotime-(Y) comparing to monazite-(Ce).

Monazite-(Ce)

Ce[PO

] is the main mineral of light rare

earth elements (LREE). Disseminated grains of monazite-
(Ce) up to 0.2 mm across can be observed in mineralized and
altered rocks. Th content in monazite-(Ce) ranges from 0.9 to
4.5 wt. % (Table 13).

Quartz

SiO

is the dominant gangue mineral. It is of brown

colour. Grains are mostly xenomorphic, of mosaic texture,
from 0.05 to 0.1 mm rarely up to 1 mm across and they show
undulatory extinction. Prismatic crystals with pyramidal tops
can also be seen.

Tourmaline

Na(Mg,Fe,Mn,Li,Al)

(BO

)

(OH,F)

[Si

forming columnar crystals (from 0.03 to 0.4 mm long) of green
colour with typical pleochroism, is abundant mainly in hydro-
thermally altered phyllite with monazite-(Ce).

Goethite

a-FeOOH and limonite occur as colloform bot-

ryoidal aggregates from 0.05 to 2 mm across in fissures and
cavities. They replace pyrite, and pseudomorphs of goethite

after euhedral pyrite can be observed.

In the outcrops, the vein is characterized by the presence of

iron hydroxides, and by the presence of secondary minerals of
yellow and yellowish-green colour. These are weathering
products of uranium minerals and arsenopyrite alteration.

Trögerite

[UO

|AsO

]

.6H

O ? forms yellow coat-

ings of samples with abundant uraninite, brannerite and arse-
nopyrite. It also forms pseudomorphs after colloform and
spheroidal uraninite up to 1 mm across. However EDX analy-
sis of mineral with moderately increased content of Fe does
not exclude the presence of kahlerite Fe[UO

|AsO

]

.12H

or metakahlerite (Table 14).

Zeunerite

Cu[UO

|AsO

]

.10H

O is rare in strongly weath-

ered samples with goethite. It is characterized by deep green
internal reflection and distinct cleavage under the polarizing
microscope (Fig. 16). It is in close paragenetic association
with goethite. The identification of zeunerite was confirmed
by EDX analysis (Table 15).

Scorodite

[AsO

].2H

O is often associated with

Fig. 15.

Needle-like aggregate of xenotime-(Y) forms veinlet in

uraninite. GR 2/1. SEM-BEI

310 ROJKOVIČ, HÁBER and NOVOTNÝ

Association of elements

The uranium accumulation in Zimná Voda is accompanied

by distinctly increased contents of Au, B, La and Y (Ta-
ble 17). The average content of Au in the whole vein is 25, 28
ppm and maximal content of Au reaches 164 ppm. Au con-
tents range from 0.11 to 17. 8 ppm in the surrounding rocks
and from 15 to 40 cm from vein.

Moderately are increased contents of Ag, Co, Cu, Mo, Ni,

Pb, W and Zr. Quartz veins with U-Au-REE mineralization in
the Slovenské rudohorie Mts. cut the Early Paleozoic se-
quences. They show significant enrichment with U, Au, Cu,
Pb, Ca, Y, P, Th, Ag, Co, Sr, La and Mo compared to black
phyllites and lydites (Rojkovič et al. 1995). This enrichment

Weight %

Atomic proportion on 3 atoms

Sample

Total

ZV 17h

79.1

0.3

2.3

17.9

99.6

1.97

0.02

0.10

2.91

ZV 18h

78.6

0.4

1.6

2.1

17.5

100.2

1.97

0.04

0.09

2.86

ZV 7 h

78.4

1.8

20.6

100.8

1.82

0.07

3.11

ZV 5 h

78.3

0.4

1.3

1.8

17.0

98.8

2.01

0.03

0.08

2.85

ZV 4 h

78.2

0.4

0.8

1.8

17.2

98.4

2.00

0.03

0.02

0.08

2.87

ZV 6 h

78.1

1.6

17.2

96.9

2.03

0.07

2.90

ZV 16h

78.0

0.5

1.4

2.2

17.6

99.7

1.95

0.04

0.09

2.87

ZV 14h

77.7

0.5

1.3

2.3

17.7

99.5

1.95

0.04

0.03

0.10

2.88

ZV 9 h

77.6

0.5

1.6

2.2

17.8

99.7

1.93

0.04

0.09

2.89

ZV 15h

77.5

0.5

1.1

2.1

17.6

98.8

1.95

0.04

0.03

0.09

2.89

ZV 10h

77.5

0.5

1.2

2.2

17.8

99.2

1.93

0.04

0.03

0.09

2.90

ZV 8 h

77.5

1.3

20.9

99.7

1.79

0.05

3.16

ZV 13h

77.3

0.6

1.3

2.4

17.5

99.1

1.94

0.05

0.03

0.10

2.87

ZV 12h

77.0

0.5

1.3

2.1

17.7

98.6

1.94

0.04

0.03

0.09

2.90

ZV 11h

76.5

0.5

1.1

2.2

17.6

97.9

1.93

0.04

0.03

0.09

2.91

ZV 2 h

75.6

1.8

22.1

99.5

1.70

0.07

3.23

ZV 3 h

75.3

1.9

21.7

98.9

1.71

0.07

3.21

ZV 19h

72.9

0.7

3.8

5.1

18.2

100.7

1.77

0.05

0.09

0.21

2.88

ZV 23h

68.2

0.5

2.9

9.7

18.6

99.9

1.62

0.04

0.07

0.39

2.88

ZV 24h

67.9

10.6

22.6

101.1

1.46

0.39

3.15

ZV 26h

67.3

11.6

22.4

101.3

1.44

0.43

3.13

ZV 21h

67.0

0.6

4.4

9.9

18.9

100.8

1.57

0.05

0.10

0.40

2.88

ZV 25h

66.9

11.4

22.4

100.7

1.44

0.42

3.14

ZV 20h

66.8

0.5

5.5

7.6

21.2

101.6

1.48

0.04

0.12

0.29

3.07

ZV 22h

66.4

0.5

5.5

10.0

18.2

100.6

1.59

0.04

0.13

0.41

2.83

ZV 27h

62.6

0.5

4.2

11.3

22.4

101.0

1.34

0.03

0.09

0.41

3.13

Table 9:

Chemical composition of bismuthinite.

Table 10:

Chemical composition of molybdenite.

Weight %

Atomic prop.

Sample

Total

ZV 12b.1

56.8

44.9

101.7

0.89

2.11

ZV 12b.2

55.4

44.1

99.5

0.89

2.11

ZV 12b.3

58.7

44.5

103.2

0.92

2.08

ZV 12b.4

56.7

45.6

102.3

0.88

2.12

Table 11:

Chemical composition of tetrahedrite.

Weight %

Sample

Total

ZV 4/2

38.3

4.9

1.8

31.6

0.2

24.1

100.9

ZV 4/3

38.4

4.7

2.0

31.6

0.1

23.5

100.3

Atomic proportion on 29 atoms

ZV 4/2

10.1

1.5

0.5

4.3

12.5

ZV 4/3

10.2

1.4

0.5

4.4

12.4

Table 12:

Chemical composition of xenotime-(Y).

Weight %

Sample

Total

YPO

48.4

16.8 34.8

100

ZV 1

28.2

5.3

0.9

21.4 37.2

100

Atomic proportion on 2 atoms

ZV 1

0.58 0.06 0.08 0.01 1.27

trögerite (?). It forms light-green and yellow-green powder
coatings in samples with abundant arsenopyrite. It replaces
arsenopyrite (Fig. 17). Its identification was confirmed by
EDX analysis (Table 16).

U-Au-Co-Bi-REE MINERALIZATION IN THE GEMERIC UNIT 311

reflects the presence of apatite, xenotime-(Y), uraninite, gold
and arsenopyrite in veins. W also shows a local increase.

Origin of mineralization

Quartz veins with U-Au-REE mineralization occur close to

the Humel Granite but also in proximity to the Hnilec Granite
(Varček 1975; Rojkovič & Novotný 1993). They show a spa-
tial and partly also material relationship to the Gemeric gran-

Table 13:

Chemical composition of monazite-(Ce).

Weight %

Sample

ThO

SiO

CaO

PbO

Total

ZV 4p.1

31.6

15.3

5.2

14.0

2.8

2.2

1.6

0.6

26.1

99.4

ZV 4p.2

25.3

7.60

5.3

19.4

5.3

3.1

4.5

0.9

26.7

98.0

ZV 4p.3

31.5

12.6

4.8

16.7

3.4

2.9

0.3

27.8

100.1

ZV 4p.4

30.8

14.6

5.1

15.1

3.5

2.5

1.2

0.5

26.4

99.8

ZV 4p.5

28.3

13.2

4.7

15.9

3.7

2.5

0.7

25.9

97.4

ZV 4p.6

27.8

12.2

4.8

11.1

2.6

2.7

1.2

1.9

0.3

0.7

0.3

31.2

96.9

ZV 4p.7

29.3

12.7

4.7

12.9

2.9

3.0

0.9

2.0

0.2

0.4

0.2

31.0

100.2

ZV 4p.8

28.0

12.6

5.0

12.7

3.0

3.2

1.5

1.8

0.3

0.5

0.3

29.6

98.4

ZV 4p.9

29.0

11.6

5.2

13.9

2.6

2.5

2.0

0.7

0.5

0.2

28.5

99.1

ZV 4p.10

28.3

14.2

4.5

12.6

2.8

1.3

1.9

0.3

0.4

29.2

98.2

Atomic proportion on 2 atoms

-2

ZV 4p.1

0.49

0.24

0.08

0.21

0.04

0.03

0.02

0.93

2.04

ZV 4p.2

0.39

0.12

0.08

0.29

0.08

0.04

0.96

2.01

ZV 4p.3

0.47

0.19

0.07

0.24

0.05

0.04

0.96

2.03

ZV 4p.4

0.47

0.22

0.08

0.23

0.05

0.04

0.01

0.94

2.04

ZV 4p.5

0.45

0.21

0.07

0.24

0.05

0.04

0.02

0.94

2.03

ZV 4p.6

0.40

0.18

0.07

0.16

0.04

0.01

0.04

1.04

1.97

ZV 4p.7

0.42

0.18

0.07

0.18

0.04

0.01

0.04

1.02

1.99

ZV 4p.8

0.41

0.19

0.07

0.18

0.04

0.01

0.04

1.00

1.99

ZV 4p.9

0.43

0.17

0.08

0.2

0.04

0.03

0.02

0.04

0.98

2.01

ZV 4p.10

0.42

0.21

0.07

0.18

0.04

0.01

0.04

1.00

2.00

ites with increased content of U, Sn, Th and B. The important
sources of metals were probably the surrounding sediments
such as black phyllites, lydites and associated phosphates
(Rojkovič et al. 1995). Black phyllites and lydites were a
probable source of Au, Ag, Mo, Cu (partly U), and associated
phosphates were a probable source of REE in veins. Sedi-
ments with increased contents of organic matter, P, U, W, Mo
and REE are the probable source of the similar vein U-Au
mineralization near Hoehensteinweg in Germany (Dill 1982).
The copper vein mineralization is accompanied by uraninite,

Fig. 16.

Aggregate of zeunerite (white). ZV 12a, SEM-SEI.

Fig. 17.

Scorodite (grey) replaces arsenopyrite (white) from mar-

gin and along fissures. ZV 1a, SEM-BEI.

312 ROJKOVIČ, HÁBER and NOVOTNÝ

Varček (1975) presumed a temperature of vein uranium min-

eralization in the Spišsko-gemerské rudohorie Mts. from 330
to 220

C according to decrepitation temperatures. The ho-

mogenization temperature of fluid inclusions in quartz associ-
ated with uranium mineralization in Zimná Voda gives T

hom

from 300 to 450

C and T

hom

from 240 to 280

C for quartz as-

sociated with younger sulphides. Uranium is probably trans-
ported in chloride and fluoride complexes at temperatures
from 300 to 600

C (Redkin et al. 1989).

Gemeric granites show large isotopic heterogeneity. The

strontium isotopes were homogenized in the period from 270
to 223 Ma and standard interpretation identifies the time of ho-
mogenization with the time of granite intrusion. The younger
(Cretaceous) age data are rather a result of the later alterations
than polyphase origin (Kovách et al. 1986; Cambel et al.
1990). However Rb-Sr dating 101 ± 5 Ma of Rochovce Gran-
ite (Kovách et al. 1986) with disseminated U-Ti-REE miner-
alization confirms the Cretaceous age of granite. As reliable
U-Pb dating of vein uranium mineralization is missing nei-
ther its Permian nor its Cretaceous age can be excluded.

Goethite, limonite and scorodite were formed during super-

gene processes. Gold was mobilized and large grains were
formed.

Acknowledgments:

Many thanks are due to rock and mineral

analysis, SEM photographs to Pavol Siman, Patrik Konečný,
František Caňo and Jozef Stankovič from Geological Survey in
Bratislava, ubica Puškelová, Júlia Kotulová and Ivan Križáni
of Geological Institute of the Slovak Academy of Sciences in
Bratislava. This study was partly supported by Slovak Grant
Agency by Project GA 2 1082: “Hercynian magmatism and
rare element mineralization in the Western Carpathians”. This
paper is contribution to IGCP Project No. 373 “Correlation,

Table 17:

Contents of trace elements (in ppm) in vein and wall rocks.

B Corg Co

692

281

139

421

43 4075

1336

79 224

352 421

164 2880

800

960

134 1800

106

234 6050 11852 155 270

836 1910

a—average (Au from 43, the others from 10 samples), m—maximum

Table 14:

Chemical composition of trögerite (?).

Weight %

Sample

Total

49.4

0.0 15.5

33.2

+H 1.9

FeU

43.7

5.1 13.7

35.2

+H 2.2

FeU

46.8

5.5 14.7

31.4

+H 1.6

YZV 1

55.2

2.5 22.3

20.1

100.1

Atomic proportion on 5 atoms

Total

YZV 1

2.02

0.39 2.59

5.00

trögerite,

kahlerite,

metakahlerite

Table 15:

Chemical composition of zeunerite.

Weight %

Sample

Total

CuU

6.5

48.9

6.4

36.1 +H 2.1

CuU

6.8

50.8

6.6

34.1 +H 1.7

CuU

6.0

44.8

14.1 33.2 +H 1.9

CuU

6.2

46.4

14.6 31.2 +H 1.6

ZV 12.1

1.5

57.8

0.2

20.5 14.9 94.9

ZV 12.2

1.1

58.3

0.1

21.7 15.1 96.3

ZV 12.3

1.0

59.7

0.1

22.3 15.5 98.6

torbernite,

metatorbernite,

zeunerite,

metazeunerite

Table 16:

Chemical composition of scorodite.

Weight %

Atomic prop.

Sample

Total

FeAsO

24.2

32.5

41.6 +H 1.75

ZV 1

28.9

35.8

1.7

33.7

100.1

1.04

0.96

brannerite, molybdenite and gold in Mitterberg in Austria. It is
a mobilization product of low-grade stratabound uranium min-
eralization in the Permian “Violet Serie” (Paar 1976).

The association of minerals such as uraninite, brannerite,

molybdenite, tourmaline, apatite and monazite-(Ce) represent
the older mineralization in the aureole of the Humel Granite
Massif. Sulphidic minerals as arsenopyrite, glaucodot, cobal-
tite, tetrahedrite, bismuth, bismuthinite and galena represent
the younger phase of mineralization. Characteristic is accu-
mulation of Co–Fe–Ni sulphoarsenides (arsenopyrite, glau-
codot, cobaltite) and bismuth minerals. Mineralization of the
U-Au-Bi-Co-REE association was not described yet in the
Western Carpathians.

The xenotime-(Y) is distinctly younger than the uranium

mineralization and apatite in the vein studied. Remobilized
xenotime-(Y) is often formed by release of Y and HREE from
the uraninite lattice and by the following reaction with the
mobile phosphates (Oberthür 1987).

Anatomy and Magmatic-Hydrothermal Evolution of Ore-Bear-
ing Felsic Igneous Systems in Eurasia”.

References

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

classification of Rakovec Group and Late Paleozoic in
Spišsko-gemerské rudohorie (ore mountains). Geol. Práce, Spr.,
75, 27–56 (in Slovak, English summary).

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

L., Vozár J. & Vozárová A., 1984: Geological map of Sloven-
ské rudohorie Mts., eastern part, 1:50,000, GÚDŠ, Bratislava.

Borischanskaya S.S, Vinogradova R.A. & Krutov G.A., 1981: Min-

eraly nike a i koba ta. Izd. Moskovskogo universiteta, Moskva,
1–220 (in Russian).

Cambel B., Krá J. & Burchart J., 1990: Isotope geochronology of

the Western Carpathians crystalline complexes. VEDA, Brat-
islava, 1–183 (in Slovak).

U-Au-Co-Bi-REE MINERALIZATION IN THE GEMERIC UNIT 313

Dill H., 1982: Geologie und Mineralogie des Uranvorkommens am

Hoehensteinweg bei Poppenreuth (NE-Bayern) — Ein Lagers-
taettenmodell. Geol. Jb. (Hannover), 50, 83.

Faryad S. W., 1991: Pre-Alpine metamorphic events in Gemeric

Unit. Miner. slovaca, 23, 395–402.

Grecula P., 1982: Gemericum — segment of the Paleotethyan riftog-

enous basin. Miner. slovaca, Monografia (Bratislava), 1–263
(in Slovak).

Ivanička J., Snopko L., Snopková P. & Vozárová A., 1989: Gelnica

Group-Lower Unit of Spišsko-gemerské rudohorie Mts. (West
Carpathians), Early Paleozoic. Geol. Carpathica, 40, 483–501.

Kovách A., Svingor E. & Grecula P., 1986: Rb-Sr izotopic ages of

granitoids from the Spišsko-Gemerské rudohorie Mts. Western
Carpathians. Eastern Slovakia. Miner. slovaca, 18, 1–14.

Novotný L. & Čížek P., 1979: New occurrence of uranium-gold

mineralisation to the south of Prakovce village in Spišsko-ge-
merské rudohorie Mts. (Eastern Slovakia). Miner. slovaca, 11,
188–190 (in Slovak, English abstract).

Oberthür T., 1987: Mineralogy and geochemistry of phosphate min-

erals and brannerite from the proterozoic Carbon Leader Reef
gold and uranium placer deposit, Witwatersrand, South Africa.
Monograph.

Series on Mineral Deposits, Gebrüder Borntrae-

ger,

Berlin-Stuttgart, 27, 129–142.

Paar W., 1976: Telluride der Gold-Nasturan Paragenese von Mitter-

berg (Salzburg). Neu. Jb. Mineral., Mh., 193–202.

Redkin A.F., Savelyeva N.I., Sergeyeva E.I., Omelyanenko B.I.,

Ivanov I.P. & Khodakovsky I.L., 1989: Investigation of ura-
ninite (UO

2(c)

) solubility under hydrothermal conditions. Sci.

Géol., Bull.,

42, 329–334.

Rojkovič I. & Novotný L., 1993: Uranium mineralization of Ge-

mericum (Western Carpathian). Miner. slovaca, 25, 368–370
(in Slovak, English abstract).

Rojkovič I., Puškelová ., Khun M. & Medve J., 1995: U-REE-Au

in veins and black shales of the Gemeric Unit, Slovakia. In:
Pašava J., Kříbek B. & Žák K., (Eds.): Mineral deposits: From
their origin to their environmental impacts. A. A. Balkema, Rot-
terdam, Brookfield, 789–792.

Strunz H., 1970: Mineralogische Tabellen. Akademische Velagsges-

sellschaft,

Geest & Portig K.-G., Leipzig 1–621.

Varček C., 1975: Mineralogical investigation of uranium mineraliza-

tion in the central part of the Spišsko-gemerské rudohorie Mts.,
Manuscript, URANPRES

Spišská Nová Ves, 1–214 (in Slovak).

Vozárová A. & Ivanička J., 1993: Lithogeochemistry of Early Pale-

ozic metasediments in Southern Gemericum. Západ. Karpaty,
Sér. Mineral., Petrogr., Geochém., Metalogen.,

16, 116–149 (in

Slovak, English summary).