GeolCarp_Vol65_No2_131

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Introduction

Rare-element  granitic  pegmatites  represent  lithologically
unique rocks, some of the most evolved magmatic rocks on
the Earth, and principally the products of extreme magmatic
fractionation of parental granitic magma (London 2008, and
references therein). The fractionation processes in fluid-rich
environments  enabled  the  concentration  of  a  variety  of  rare
lithophile elements (Be, B, Ta, Nb, Li, Rb, Cs, etc.) and pre-
cipitation of their own minerals. Rare-element granitic peg-
matites usually occur in the Precambrian cratons and ancient
collisional zones. However, they are also common in the Pa-
leozoic to Cenozoic continent- and subduction-related colli-
sional terranes. In Europe, the youngest known rare-element
and other granitic pegmatites occur in Alpine-orogeny related,
post-collisional  fault  zones  between  the  continental  frag-
ments,  such  as  the  Periadriatic,  Aegean  and  Corsica-Apulia
zones,  together  with  coeval  granitic  rocks  and  other  related
plutonic  and  volcanic  members.  The  magmatic  province
along  the  Periadriatic  (Insubric)  Fault  System  comprises
Eocene  to  Oligocene  ( ~ 42  to  25 Ma;  e.g.  Scharbert  1975;
Romer  et  al.  1996;  Oberli  et  al.  2004;  Lustrino  et  al.  2011;

Rare-element granitic pegmatite of Miocene age emplaced in

UHP rocks from Visole, Pohorje Mountains (Eastern Alps,

Slovenia): accessory minerals, monazite and uraninite

chemical dating

PAVEL UHER

, MARIAN JANÁK

, PATRIK KONEČNÝ

and MIRIJAM VRABEC

Geological Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05 Bratislava, Slovak Republic;

puher@fns.uniba.sk; marian.janak@savba.sk

Dionýz Štúr State Geological Institute, Mlynská dolina 1, 817 04 Bratislava, Slovak Republic; patrik.konecny@geology.sk

University of Ljubljana, Faculty of Natural Sciences and Engineering, Department of Geology, Aškerčeva 12, SI-1000 Ljubljana, Slovenia

(Manuscript received October 30, 2013; accepted in revised form March 11, 2014)

Abstract: The granitic pegmatite dike intruded the Cretaceous UHP rocks at Visole, near Slovenska Bistrica, in the
Pohorje Mountains (Slovenia). The rock consists mainly of K-feldspar, albite and quartz, subordinate muscovite and
biotite, while the accessory minerals include spessartine-almandine, zircon, ferrocolumbite, fluorapatite, monazite-
(Ce), uraninite, and magnetite. Compositions of garnet (Sps

48—49

Alm

45—46

Grs + And

3—4

Prp

1.5—2

), metamict zircon with

3.5 to 7.8 wt. % HfO

[atom. 100Hf/(Hf + Zr) = 3.3—7.7] and ferrocolumbite [atom. Mn/(Mn + Fe) = 0.27—0.43,

Ta/(Ta + Nb) = 0.03—0.46] indicate a relatively low to medium degree of magmatic fractionation, characteristic of the
muscovite – rare-element class or beryl-columbite subtype of the rare-element class pegmatites. Monazite-(Ce) re-
veals elevated Th and U contents (

≤11 wt. % ThO

≤5 wt. % UO

). The monazite—garnet geothermometer shows a

possible precipitation temperature of ~ 495 ± 30 °C at P ~ 4 to 5 kbar. Chemical U-Th-Pb dating of the monazite yielded
a Miocene age (17.2 ± 1.8 Ma), whereas uraninite gave a younger ( ~ 14 Ma) age. These ages are comtemporaneous with
the main crystallization and emplacement of the Pohorje pluton and adjacent volcanic rocks (20 to 15 Ma), providing
the first documented evidence of Neogene granitic pegmatites in the Eastern Alps. Consequently, the Visole pegmatite
belongs to the youngest rare-element granitic pegmatite populations in Europe, together with the Paleogene pegmatite
occurrences along the Periadriatic (Insubric) Fault System in the Alps and in the Rhodope Massif, as well as the Late
Miocene to Pliocene pegmatites in the Tuscany magmatic province (mainly on the Island of Elba).

Key words: granitic pegmatite, spessartine-almandine, columbite, zircon, fluorapatite, monazite, uraninite, age, Pohorje,
Eastern Alps.

Pomella  et  al.  2011,  etc.),  mainly  tonalite  to  granodiorite
plutonic rocks, which occur in the belt from the Italian Alps
(Biella, Bergell, Adamello, Novate intrusions, etc.) to Slove-
nia  (Karavanke  Mts).  The  Oligocene  to  Miocene  granitic
rocks  of  the  Pannonian  area  (Zala  basin)  and  Sáva-Vardar
zones  as  well  as  the  Serbo-Macedonian  Massif  (Pamić  &
Balen 2001; Pamić et al. 2002; Benedek 2004; Kovács et al.
2007,  and  references  therein)  represent  a  possible  east  and
south-east  continuation  of  the  Periadriatic  magmatic  prov-
ince.  Occurrences  of  several  late  Cretaceous,  Paleogene  to
early Neogene granitic intrusions ( ~ 70 to 20 Ma) are reported
from the Rhodope Massif in Greece and Bulgaria (e.g. Kilias
& Mountrakis 1998; Soldatos et al. 2008; Pipera et al. 2013).
In  contrast,  the  monzogranites  of  the  Tuscany  province,
mainly  the  Monte  Capanne  pluton  (Elba  Island,  Italy),  are
younger  in  age,  Late  Miocene  to  Pliocene  intrusions  ( ~ 8  to
4.3 Ma;  Dini  et  al.  2002;  Peccerillo  2005).  The  Periadriatic,
Rhodope, and Tuscany granitic rocks contain associated peg-
matite dikes, in some places with rare-element mineralization
(e.g. Wenger & Armbruster 1991; Pezzotta 2000;  Alexandrov
et  al.  2001;  Aurisicchio  et  al.  2001,  2002;  Guastoni  et  al.
2008; Guastoni 2012).

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Dykes of aplites and granitic pegmatites were also described

in the Pohorje Mountains (Slovenia), the easternmost continu-
ation  of  the  Alpine,  Periadriatic  plutonic-volcanic  province
(e.g. Kirst et al. 2010). They contain tourmaline and beryl in
some places (Zupančič et al. 1994; Vrabec & Dolenec 2002).
The ages of the plutonic gabbros, tonalites, granodiorites, gra-
nitic porphyries and volcanic rocks (mainly dacites) of the Po-
horje Mts have been determined as Early to Middle Miocene
(20  to  15 Ma;  Fodor  et  al.  2008;  Trajanova  et  al.  2008),
younger than other Periadriatic magmatic rocks in the Western
and Central Alps. However, a detailed description of the min-
eral  composition,  age  determination  and  genetic  relations  of
the Pohorje granitic pegmatites is still lacking.

Consequently, the aim of our contribution is the charac-

terization of a newly discovered rare-element granitic peg-
matite  near  Visole,  in  the  SE  part  of  the  Pohorje  Mts.
Composional variations of accessory minerals, chemical dat-
ing of monazite and uraninite, as well as age relations to ad-
jacent  magmatic  rocks  and  other  Paleogene  to  Neogene
pegmatite  populations  in  the  broader  Aegean,  Periadriatic
and Apulian area are presented.

Geological background

The Pohorje Mountains in north-eastern Slovenia are lo-

cated  on  the  south-eastern  margin  of  the  Eastern  Alps
(Fig. 1). The area of the Pohorje Mts is built up of two major
tectonic  units  or  nappes  emplaced  during  the  Cretaceous.
The lower nappe represents the Lower Central Austroalpine
(Janák  et  al.  2004)  and  consists  of  medium-  to  high-grade
metamorphic rocks of continental crust, predominantly mica
schists, gneisses, marbles and metaquartzites.

In the south-eastern part, numerous eclogite bodies are

partly amphibolitized. An 8

×1 km body of metaultrabasic

rocks  is  located  in  the  vicinity  of  Slovenska  Bistrica  (the
Slovenska Bistrica Ultramafic Complex, SBUC; Janák et al.
2006) composed of serpentinized harzburgite and rarely gar-
net peridotite (Hinterlechner-Ravnik et al. 1991; Janák et al.
2006;  De  Hoog  et  al.  2009,  2011).  All  these  rocks  experi-
enced  high-  to  ultrahigh-pressure  metamorphism  (Hinter-
lechner-Ravnik  et  al.  1991;  Janák  et  al.  2004,  2006,  2009;
Sassi et al. 2004; Miller et al. 2005; Vrabec et al. 2012) re-
sulting  from  deep  subduction  of  continental  crust  (Janák  et
al.  2004;  Stüwe  &  Schuster  2010).  The  timing  of  HP/UHP
metamorphism  is  Cretaceous,  ca.  92—93 Ma  (Thöni  2002;
Miller et al. 2005; Thöni et al. 2008; Janák et al. 2009).

The upper nappe is formed by phyllites and other low-

grade metamorphic rocks and their Permo-Triassic sedimen-
tary  cover,  and  represents  the  Upper  Central  Austroalpine
(Janák  et  al.  2004).  This  nappe  stack  is  overlain  by  Early
Miocene sedimentary rocks that belong to the syn-rift basin
fill  of  the  Styrian  Basin.  The  Pohorje  Mts  represent  a  large
antiform with an ESE-WNW-striking axis (Kirst et al. 2010),
the  core  of  which  is  intruded  by  a  granodioritic  to  tonalitic
pluton  of  Miocene  age  ( ~ 20  to  15 Ma;  Altherr  et  al.  1995;
Fodor et al. 2008; Trajanova et al. 2008).

The investigated pegmatite occurs near Visole settle-

ment, ca. 5 km NW of Slovenska Bistrica (Fig. 1). The GPS

geographic coordinates of the pegmatite are as follows:
N 141 46°24.405’, E 15°31.590’. The pegmatite forms a dyke,
up to ~ 30 cm thick in serpentinite, within the SBUC. The con-
tacts between the pegmatite and host rock are sharp, without
assimilation or desilicification phenomena. The pegmatite
body is weakly zonal, the graphic K-feldspar (perthitic micro-
cline to orthoclase) + quartz, coarse-grained to blocky K-feld-
spar + albite(An

06—08

) + quartz + muscovite + garnet ± biotite

(Fig. 2a), and fine-grained saccharoidal albite-rich aplitic
zones can be distinguished.

Analytical methods

Polished thin sections of the granitic pegmatite were stud-

ied under polarizing microscope.

Chemical compositions and internal zoning of minerals

were investigated using the CAMECA SX 100 wave-length
electron microprobe housed at the Dionýz Štúr State Geo-
logical Institute, Bratislava.

Spessartine-almandine, zircon, ferrocolumbite and fluor-

apatite were measured with electron beam accelerated by
15 kV. Sample current and beam size varied according to min-
erals: spessartine-almandine was measured with 20 nA and
5 µm beam diameter, zircon and ferrocolumbite with 40 nA and
1—3 µm and fluorapatite with 20 nA and 3—5 µm. The counting
times of 10—20 s for main elements and 30—50 s for W, As, Th,
U, V, Cr, Sc, Y, and REEs were used. Monazite-(Ce) and ura-
ninite were also measured with the aim of obtaining age infor-
mation. Therefore the counting times of U and especially Pb were
enlarged to meet requirements for trace element analysis (80 s for
U, 300 s for Pb) and the beam current was adjusted to 180 nA and
spots were measured with 3 µm beam diameter. The detection
limits were 225 and 250 ppm for Th, 205 and 360 ppm for U,
95 and 100 ppm for Pb in monazite and uraninite, respectively.
The following standards were used for calibration of all detected
minerals: CaWO

(W L

α), barite (S Kα, Ba Lα), apatite (P Kα),

GaAs (As L

α), ferrocolumbite (Nb Lα), LiTaO

(Ta L

α), ortho-

clase (Si K

α, K Kα), TiO

(Ti K

α), ZrSiO

(Si K

α, Zr Lα),

HfO

(Hf L

α), ThO

(Th M

α), UO

(U M

β), Al

(Al K

α),

metallic V (V K

α), metallic Cr (Cr Kα), ScPO

(Sc K

α), YPO

(Y L

α), LaPO

(La L

α), CePO

(Ce L

α), PrPO

(Pr L

β),

NdPO

(Nd L

β), SmPO

(Sm L

β), EuPO

(Eu L

β), GdPO

(Gd L

α), TbPO

(Tb L

α), DyPO

(Dy L

β), HoPO

(Ho L

β),

ErPO

(Er L

β), TmPO

(Tm L

α), YbPO

(Yb L

α), LuPO

(Lu L

β), fayalite (Fe Kα), rhodonite (Mn Kα), willemite

(Zn K

α), forsterite (Mg Kα), wollastonite (Ca Kα), PbCO

(Pb M

α), albite (Na Kα), LiF (F Kα). We used empirically

determined correction factors applied to the following line
overlaps: Th

→U, Dy→Eu, Gd→Ho, La→Gd, Ce→Gd,

→Er, Gd→Er, Sm→Tm, Dy→Lu, Ho→Lu, Yb→Lu,

and Dy

→As (Konečný et al. 2004). The matrix effects were

corrected using the PAP procedure for all the analysed miner-
als. Spot analyses of monazite and uraninite were corrected for
mutual interferences and then the weighted average of appar-
ent  ages  were  calculated  following  the  statistical  method  of
Montel  et  al  (1996).  Moreover,  an  average  age  of  uraninite
was  also  calculated  by  the  alternative  methods  of  Ranchin
(1968), Cameron-Schiman (1978) and Bowles (1990).

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(Fig. 2b). In some places, small zircon and uraninite inclu-
sions were observed in the garnet crystals (Fig. 2b—e).

The garnet crystals are without distinct compositional

variations or trends in the main elements (Si, Al, Fe, Mn, Mg
and Ca) from core to rim. Analyses of garnet (Table 1) show
spessartine-almandine composition with slight dominance of
spessartine over almandine and negligible grossular, andra-
dite and pyrope end-members: spessartine attains 48 to 49,
almandine 45 to 46, grossular + andradite 3 to 4, and pyrope
1.5 to 2 mol %, the atomic Mn/(Mn + Fe

) ratio attains 0.51

to 0.52 (Table 1). However, central parts of the spessartine-
almandine garnet are slightly enriched in Y (0.005 to 0.013
apfu; 0.1 to 0.3 wt. % Y

), whereas the rims are usually

without detectable amounts of Y (

≤0.08 wt. % Y

). Con-

centrations of other measured elements in the garnet (P, Ti,
Sc, V, Cr, Zn, Na) are very low or under the detection limit
of the EMPA ( < 0.1 wt. % of oxide or

≤0.005 apfu).

Zircon forms rare euhedral crystals, usually 5 to 80 µm

across, as inclusions in the central parts of spessartine-almand-
ine (Fig. 2c—e), or scattered crystals in albite, K-feldspar or
quartz (Fig. 2f). Zircon in some places shows slightly irregular
zoning, probably due to metamictization. Locally, tiny anhe-
dral inclusions of uraninite (under 2 µm in size) were detected
in zircon crystals (Fig. 2d). The zircon crystals are enriched in

Table 1: Representative compositions of spessartine-almandine (wt. %)
from the Visole pegmatite.

Crystal/position 1/center 1/mid1

1/rim1 2/center 2/mid2

2/rim2

0.00

0.05

SiO

36.46

36.34

36.75

36.67

36.31

36.33

TiO

0.05

0.04

0.03

0.04

0.05

20.02

20.44

20.16

20.05

20.15

20.03

0.22

0.07

0.00

0.30

0.08

1.46

1.36

0.51

1.02

1.35

1.52

FeO

19.71

20.00

20.42

20.37

20.14

19.98

MnO

21.06

20.72

21.01

21.12

20.71

21.08

ZnO

0.00

0.06

0.08

MgO

0.44

0.45

0.54

0.40

0.45

CaO

1.42

1.33

1.02

1.10

1.16

1.08

Total

100.84

100.75

100.44

101.07

100.67

100.73

Formulae based on 12 oxygen atoms. 8 cations and valence calculation

0.000

0.003

2.982

2.970

3.010

2.995

2.976

Al Z

0.018

0.030

0.000

0.005

0.024

0.021

Sum Z

3.000

3.010

3.000

0.003

0.002

0.003

Al Y

1.912

1.939

1.946

1.925

1.923

1.913

0.090

0.084

0.031

0.063

0.083

0.094

Sum Y

2.005

2.025

1.979

1.990

2.008

2.010

0.010

0.003

0.000

0.013

0.003

1.348

1.367

1.399

1.391

1.380

1.369

1.459

1.434

1.457

1.461

1.438

1.463

0.000

0.004

0.005

0.054

0.055

0.066

0.049

0.055

0.124

0.116

0.089

0.096

0.102

0.095

Sum X

2.995

2.975

3.011

3.010

2.992

2.990

Sps

48.9

48.3

48.4

48.7

48.3

49.1

Alm

45.2

46.0

46.5

46.4

45.9

Prp

1.8

1.9

2.2

1.6

1.8

Grs+And

4.2

3.9

3.0

3.2

3.4

3.2

Sum

100.0

Mn/(Mn+Fe

)

0.52

0.51

0.52

hafnium; they contain 3.5 to 7.8 wt. % HfO

(0.03 to

0.07 Hf apfu), atomic 100Hf/(Hf + Zr) ratio attains 3.3
to 7.7 (Table 2). Uranium concentrations vary between
0.4 and 2.6 wt. % UO

(0.003 to 0.018U apfu). The

slightly elevated contents of yttrium, 0.1 to 0.7 wt. %
Y

(

≤0.012Y apfu) and iron, up to 1.1 wt. % Fe

(

≤0.03Fe apfu) are also noteworthy. Consequently, zir-

con and garnet belong to the main mineral carriers of Y
and probably also HREEs in the Visole pegmatite.

Ferrocolumbite forms euhedral to subhedral crystals

of tabular shape in K-feldspar, albite and quartz, usually
15 to 100 µm across. The mineral shows two principal
types  of  internal  zoning,  visible  under  BSE  images:
(1)  regular  fine-scale  ( < 5 µm)  oscillatory  zoning  and
(2)  irregular  convolute  or  mosaic  zoning  (Fig. 3a—d).
Both  the  regular  and  irregular  zoning  reflected  mainly
Ta-Nb  variations  in  ferrocolumbite.  The  compositional
trend  of  primary,  regular  oscillatory  zoning  in  ferro-
columbite crystals is ambiguous: both increasing and de-
creasing of the Ta/Nb ratio from central to rim zones was
observed,  whereas  the  Mn/Fe  ratio  is  nearly  constant
(Table 3, Fig. 4a). The compositional variations of both
textural patterns reveal a distinctly Fe and Nb dominant
ferrocolumbite with relatively very low to moderate Mn
and  Ta  contents.  The  primary  ferrocolumbite  domains
with  regular  oscillatory  zoning  show  a more  uniform
Mn/(Mn + Fe)  ratio  (0.29  to  0.35),  but  a  variable  and
generally  higher  Ta/(Ta + Nb)  ratio  (0.11  to  0.29)  in
comparison to the secondary irregular domains, where
Mn/(Mn+Fe) ratio attains 0.27 to 0.43 and Ta/(Ta + Nb)
achieves 0.03 to 0.24 (Table 3, Fig. 4a). Concentrations
of other elements are relatively low and similar for both
textural  types  of  ferrocolumbite;  the  mineral  contains
0.7  to  2.3 wt. %  TiO

(0.03 to 0.10 apfu Ti), 0.1 to

0.5 wt. % ZrO

(

≤0.014 apfu Zr), and 0.1 to 0.4 wt. %

MgO (

≤0.034 apfu Mg). Concentrations of other measured

elements (W, Sn, Th, U, Sc, Y, La, Ce, Sb, Zn, Ca, Na) are
negligible or under the detection limit of the electron mi-
croprobe, generally

≤0.05 wt. % (Table 3). The charge bal-

ance calculated formulae of ferrocolumbite indicate
a presence of trivalent iron: Fe

/(Fe

+ Fe

) ratio attains 12

atomic % on average. The compositional variations of ferro-
columbite reflect single monovalent substitutions: TaNb

—1

MnFe

—1

, MgFe

—1

, as well as coupled Ti

(Fe

,Mn,Mg)

—1

(Nb,Ta)

—2

and/or Fe

Ti(Fe

,Mn,Mg)

—1

(Nb,Ta)

—1

substitu-

tion (Fig. 4b).

Fluorapatite forms euhedral to subhedral columnar crystals,

usually 150 to 250 µm in size, in association with albite,
K-feldspar, biotite, spessartine-almandine, and zircon (Fig. 3e).
Fluorapatite crystals are relatively homogeneous, they show
nearly end-member composition, where F/(F + OH) atomic ra-
tio attains 0.93 to 1. Elevated Mn concentrations substitution
(up to 1.4 wt. % MnO,

≤0.10 apfu Mn) document MnCa

—1

substitution, negligible Y, Fe and Na contents were also de-
tected (Table 4).

Monazite-(Ce) forms individual euhedral to subhedral

crystals,  usually  10  to  100 µm  across,  in  association  with
quartz,  feldspar  and  muscovite.  The  monazite  crystals  are
relatively  homogenous  or  they  show  compositional  zoning

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with irregular mosaic domains or nearly regular to irregular
concentric zonal pattern (Fig. 3f), due to variations of Th, U,
REEs and Ca concentrations. Moderate to relatively high Th
and U contents ( ~ 2 to 11 wt. % ThO

and ~ 1 to 5 wt. %

) are characteristic features of the monazite (Table 5).

The monazite represents a common Ce-dominant member
with Ce > Nd

≥La>Sm, Gd, Y, Pr>other REEs atomic pro-

portions (Table 5). Monazite displays relatively large varia-
tions of La/Nd (0.36 to 1.02), La/Sm (0.53 to 2.78), La/Gd
(0.71 to 4.23) and La/Y (0.91 to 15.7) atomic ratios. The
cheralite-type substitution [Ca(Th,U)(REE,Y)

—2

] is the domi-

nant exchange trend; it prevails over the huttonite-type sub-
stitution [(Th,U)Si(REE,Y)

-1

(P,As)

—1

] (Fig. 5). Very distinct

negative Eu-anomaly is typical for studied monazite, an aver-
age Eu/Eu* ratio achieves 0.015 (Fig. 6).

Uraninite occurs as rare euhedral inclusions, up to 15 µm

across, in albite and garnet or anhedral inclusions in zircon,
up  to  5 µm  across  (Fig. 2b,d,f).  Uraninite  crystals  are  com-
positionally  homogeneous  with  elevated  content  of  Th  (2.5
to  3.7 wt. %  ThO

, 0.025 to 0.037Th apfu) and they are

slightly enriched in Y, REEs, As, Pb and locally also Fe (Ta-
ble 6). Thorium shows a negative correlation to U (Fig. 7),
indicating thorianite-type substitution (ThU

—1

) in uraninite.

Magnetite was identified by EDS as scattered euhedral crys-

tals in K-feldspar or saccharoidal albite, in association with
garnet.

Crystal/Position 1/center1 2/center 3/center 4/center

4/rim

6/center

7/rim

0.16

0.55

0.35

0.31

0.20

0.12

0.31

0.19

0.20

0.19

0.33

0.19

SiO

33.12

32.67

31.99

32.14

32.05

32.17

31.84

ZrO

61.63

59.98

59.86

58.47

54.42

59.71

58.43

HfO

3.77

3.62

3.65

3.49

7.83

3.73

3.49

ThO

0.00

0.06

0.00

0.05

0.39

1.46

1.31

2.41

2.56

0.82

2.51

0.00

0.09

0.08

0.00

0.04

0.00

0.87

0.79

0.97

1.04

0.00

0.04

0.03

0.00

0.10

0.72

0.46

0.47

0.35

0.11

0.51

0.09

0.00

0.09

0.00

0.29

0.32

0.28

0.38

0.37

0.25

0.29

0.13

0.10

0.13

0.24

0.14

0.13

0.05

CaO

0.00

0.03

0.00

0.07

0.00

Total

99.87

99.68

98.29

99.12

99.25

98.26

98.75

Formulae based on 4 oxygen atoms
P

0.004

0.014

0.009

0.008

0.005

0.003

0.008

0.003

0.006

0.003

1.022

1.014

1.010

1.011

1.023

1.014

1.007

0.928

0.908

0.922

0.897

0.847

0.917

0.901

0.033

0.032

0.033

0.031

0.071

0.034

0.031

0.000

0.003

0.010

0.009

0.017

0.018

0.006

0.018

0.000

0.003

0.000

0.001

0.000

0.021

0.019

0.023

0.025

0.000

0.001

0.000

0.002

0.012

0.008

0.006

0.002

0.009

0.001

0.000

0.001

0.000

0.003

0.004

0.002

0.003

0.001

0.002

0.001

0.000

0.001

0.000

0.002

0.000

Sum cat.

2.000

2.007

2.006

2.007

100Hf/(Hf+Zr)

3.43

3.40

3.46

3.34

7.73

3.58

3.33

Table 2: Representative compositions of zircon (wt. %) from the Visole pegmatite.

Monazite—garnet geothermometry

Measured yttrium concentrations in mon-

azite and garnet, calcium content in garnet
and adjacent albite, and calculated X

fluorapatite, together with estimated pres-
sure and fH

O of the Visole pegmatite were

used  to  determine  the  temperature  condi-
tions  employing  the  monazite—garnet  ther-
mometer (Pyle et al. 2001). The pressure of
the  pegmatite  emplacement  was  estimated
as  4—5 kbar,  consistent  with  emplacement
of  adjacent  granitic  rocks  of  the  Pohorje
pluton  according  to  the  Al-in-hornblende
barometer (Altherr et al. 1995; Fodor et al.
2008). Relevant f H

O ( ~ 1500 to 2100 bar)

was calculated according to Holland &
Powell (1998). The calculated temperatures
attain ~ 495 ± 30 °C for the central as well
as rim parts of the garnet crystals.

Chemical dating of monazite and ura-
ninite

Dating of monazite and uraninite based

on high  Th  and/or  U  content,  together  with
measurable  amounts  of  Pb  and  negligible
content  of  common,  non-radiogenic  lead
(Bowles 1990; Montel et al. 1996, and refer-
ences therein) has been applied to determine
the  age  of  the  Visole  pegmatite.  Concentra-
tions  of  U,  Th  and  Pb  in  monazite  and  ura-
ninite  were  measured  using  the  electron

microprobe as described above, and the age was calculated ac-
cording to the Montel et al. (1996) and Konečný et al. (2004)
procedure. The resulting age is the weighted average of a
group of apparent ages (from point analysis). All measured
and calculated data are given in Table 7 and Fig. 8.

The results of monazite dating show an average age of

17.2 ± 1.8 Ma, obtained from 48 spot analyses (Fig. 7). Dat-
ing of uraninite shows an average age of 14.2 ± 0.2 Ma (9 mea-
surements).  Similar  average  ages  have  been  obtained  from
alternative  methods  of  uraninite  age  calculations,  namely
14.5 ± 0.3 Ma  of  Ranchin  (1968), 12.5 ± 0.5 Ma  of  Cameron-
Schiman (1978), and 13.9 ± 0.3 Ma of Bowles (1990).

Discussion

Mineral composition

The investigated accessory minerals (spessartine-almand-

ine, zircon, ferrocolumbite, fluorapatite, monazite-(Ce), ura-
ninite) represent an assemblage which belongs to the
muscovite – rare-element class or the most primitive, beryl
type and beryl-columbite subtype within the rare-element
class of granitic pegmatites, according to the recent classifi-
cation of Černý & Ercit (2005). Beryl, as the index mineral
of this subtype was not identified in the studied Visole peg-

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sular + andradite, and

≤2 mol % py-

rope  molecule)  is  analogous  to  the
garnets in (muscovite)-rare-element
granitic  pegmatites  (e.g.  Gbelský
1980;  Baldwin  &  von  Knorring
1983;  Černý  et  al.  1985;  Wise  &
Brown  2010).  The  relatively  uni-
form  and  homogeneous  composi-
tions

spessartine-almandine

crystals without any distinct com-
positional variations or trends from
center to rims and weak oscillatory
zoning illustrate only small fluctua-
tions in Fe, Mn and other elements
during the relatively rapid and short
crystal growth.

Besides slightly elevated Y con-

tent,  the  chemical  composition  of
zircon  from  the  Visole  pegmatite
also  shows  Hf-enrichment  (up  to
7.8 wt. %  HfO

) and U (up to

2.6 wt. % UO

), which is a typical

feature of zircon in evolved granitic
pegmatites  and  highly  fractionated
leucogranites  (e.g.  Černý  et  al.
1985;  Uher  &  Černý  1998;  Breiter
et al. 2006; Breiter & Škoda 2012).

The degree of Nb-Ta fraction-

ation  in  ferrocolumbite  of  the  Vi-
sole  pegmatite  is  low  to  moderate
as shown by the clear predominance
of  Fe/(Fe + Nb)  and  Ta/(Ta + Nb)
ratios  (0.27  to  0.43  and  0.03  to

Table 3: Representative compositions of primary and secondary domains of ferrocolumbite
(wt. %) from the Visole pegmatite

Population

Primary Primary Primary Primary Second. Second. Second. Second.

Crystal/Anal.

1.1

1.3

1.6

3.2

1.7

1.12

2.1

3.7

0.00

0.13

0.00

47.24

55.69

33.20

64.01

51.13

73.33

60.32

67.68

31.76

22.85

46.53

13.94

27.29

4.41

17.60

10.84

TiO

1.67

1.59

1.47

1.98

1.76

1.44

1.65

1.19

SnO

0.00

ZrO

0.35

0.14

0.15

0.10

0.00

0.47

0.06

0.16

0.17

0.09

0.14

0.11

0.00

0.10

0.08

0.00

0.06

0.08

0.07

0.00

0.08

0.06

0.00

0.11

0.08

0.00

2.40

2.50

2.39

1.34

3.38

1.96

2.14

0.02

FeO

10.95

11.28

9.87

11.98

10.66

13.11

11.59

11.10

MnO

5.28

5.85

5.14

6.45

5.45

5.92

6.28

8.40

ZnO

0.00

0.08

0.09

0.00

MgO

0.30

0.22

0.20

0.18

0.26

0.29

0.14

0.25

Total

100.19

100.41

99.09

100.44

100.51

100.53

100.29

99.62

Formulae based on 3 cations. 6 O atoms and valence calculation
W

0.000

0.002

0.000

1.353

1.530

1.032

1.694

1.427

1.863

1.624

1.791

0.547

0.378

0.870

0.222

0.458

0.067

0.285

0.173

0.080

0.073

0.076

0.087

0.082

0.061

0.074

0.052

0.000

0.011

0.004

0.005

0.004

0.003

0.000

0.014

0.002

0.000

0.003

0.004

0.003

0.000

Sum B

1.991

1.988

1.987

2.011

1.976

1.994

1.997

2.018

0.002

0.001

0.002

0.000

0.001

0.002

0.001

0.000

0.002

0.000

0.114

0.124

0.059

0.157

0.083

0.096

0.001

0.580

0.573

0.568

0.586

0.551

0.616

0.577

0.543

0.283

0.301

0.299

0.320

0.285

0.282

0.317

0.416

0.000

0.003

0.004

0.000

0.028

0.020

0.021

0.016

0.024

0.012

0.022

Sum A

1.009

1.011

1.013

0.988

1.025

1.005

1.003

0.983

Mn/(Mn+Fe)

0.290

0.305

0.302

0.332

0.287

0.320

0.433

Ta/(Ta+Nb)

0.288

0.198

0.457

0.116

0.243

0.035

0.149

0.088

Fig. 4. Compositional variation of ferrocolumbite from the Visole pegmatite (atomic proportions). a – Quadrilateral columbite-tantalite
diagram; b – Substitution Ti vs. M

(F Mn + Mg) + M

(Nb + Ta) diagram.

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0.24,  respectively).  Such  values  are  typical  for  the  most
primitive, fluorine-poor populations of beryl-columbite sub-
type  pegmatites,  for  example  in  the  Separation  Rapids
group,  Ontario  (Tindle  &  Breaks  1998)  or  Topsham  area,
Maine  (Wise  et  al.  2012).  On  the  contrary,  fractionation
trends  of  the  Nb-Ta  oxide  minerals  in  more  evolved  beryl-
columbite  pegmatites  also  attain  Ta-  and  Mn-rich  members
of  the  columbite,  tapiolite  and  wodginite  group  minerals
(Černý  et  al.  1986;  Černý  1989;  Tindle  &  Breaks  1998;
Novák et al. 2000, 2003; Chudík et al. 2011). The textural re-
lationships  of  the  Visole  ferrocolumbite  indicate  its complex
origin: a primary magmatic character of the regular oscillatory
zones,  which  are  partially  replaced  by  younger,  late-mag-
matic to post-magmatic, secondary irregular zones, presum-
ably  originating  from  dissolution-reprecipitation  of  the
primary ferrocolumbite crystals. Such complicated texture of
columbite-group  minerals  reflects  a magmatic  to  subsolidus
evolution of the patental rocks as described in many granitic
pegmatites  (Van  Lichtervelde  et  al.  2007;  Rao  et  al.  2009;
Chudík et al. 2011, etc.).

Fluorapatite is the most common phosphate phase in phos-

phate-poor granitic pegmatites of the LCT family, derived

Table 4: Representative compositions of fluorapatite (wt. %) from
the Visole pegmatite.

Crystal/Position

X1Core

X2Core

X2Rim

Analyse

41.38

41.48

41.22

0.08

0.09

0.08

SiO

0.03

0.00

0.09

0.31

0.27

0.29

0.15

0.11

0.14

0.09

0.10

0.00

FeO

0.21

0.25

0.20

MnO

1.44

0.99

0.88

CaO

52.92

54.32

54.00

0.20

0.16

0.15

0.00

0.13

0.10

3.83

3.47

3.51

O=F

–1.61

–1.46

–1.48

Total

99.18

99.94

99.24

Formulae based on 13 anions and OH+F = 1 apfu
P

2.989

2.973

2.972

0.004

0.003

0.000

0.008

Sum T

2.996

2.977

2.984

0.014

0.012

0.013

0.005

0.003

0.004

0.003

0.000

0.015

0.018

0.014

0.104

0.071

0.063

4.838

4.927

0.033

0.026

0.025

Sum M

5.016

5.062

5.048

Sum cat.

8.012

8.039

8.032

0.000

0.071

0.055

1.034

0.929

0.945

Sum X

1.034

1.000

11.966

12.071

12.055

* H

O – calculated on ideal stoichiometry S, Al, La, Mg, Sr, Ba,

Pb, K, Cl below detection limit.

Fig. 5. Monazite-(Ce) Th + U + Si vs. REE + P + As substitution dia-
gram from the Visole pegmatite (atomic proportions).

Fig. 6. Monazite/chondrite normalized diagram of REE from the
Visole pegmatite (weight proportions). Chondrite values after Taylor
& McLennan (1985).

from low-P granitic magmas. On the contrary, Fe-Mn-Ca and
Li-Na-Al phosphate phases (mainly triplite, graftonite,
beusite, sarcopside, priphyline, amblygonite, montebrasite)
are developed in P-rich rare-element granitic pegmatites (e.g.
Černý & Ercit 2005; London 2008). Very high F/(F + OH) ra-
tio ( > 0.9) and elevated Mn content (

≤0.1 apfu) in the Visole

fluorapatite document a slight to moderate degree of mag-
matic fractionation; the values are very comparable to primary
magmatic apatite compositions from numerous granitic peg-
matites (Piccoli & Candela 2002, and references therein).

The Eu/Eu* is distinctly low in the studied monazite

(0.015 in average). Such negative Eu-anomalies indicate an

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Table 5: Representative compositions of monazite-(Ce) (wt. %) from the Visole pegmatite.

Anal.

29.32

28.59

29.22

29.57

28.31

28.73

28.70

0.11

0.09

0.11

0.12

0.11

0.24

0.23

SiO

0.64

0.23

0.51

0.43

0.31

0.76

0.39

0.35

ThO

7.58

1.95

7.43

10.94

3.84

9.53

5.28

4.04

2.78

1.65

1.02

2.54

1.10

1.11

4.99

1.20

4.64

3.03

2.12

1.41

1.50

2.11

1.77

0.49

9.27

5.53

9.86

9.43

7.61

9.54

9.88

9.50

21.23

18.52

23.23

21.97

21.60

22.84

23.29

24.17

2.73

3.12

3.09

2.80

3.23

3.00

3.06

3.42

10.55

15.14

11.68

9.72

14.40

11.15

10.60

13.59

3.93

9.82

4.87

4.88

8.38

4.61

4.81

7.27

0.02

0.00

0.05

0.02

0.00

3.11

7.61

3.28

3.36

5.71

3.04

3.06

3.76

0.39

0.61

0.26

0.30

0.38

0.28

0.26

0.19

1.34

1.50

0.83

0.66

0.78

0.87

0.74

0.35

0.15

0.11

0.07

0.04

0.00

0.04

0.00

0.50

0.29

0.28

0.30

0.25

0.35

0.31

0.26

0.11

0.09

0.05

0.12

0.10

0.08

0.07

0.09

0.62

0.12

0.14

0.15

0.11

0.13

0.16

0.06

0.08

0.09

0.07

0.05

0.11

0.08

FeO

0.00

0.78

0.00

CaO

1.86

0.67

1.46

2.54

0.96

1.73

2.09

1.02

PbO

0.01

0.00

0.01

0.00

0.02

0.01

Total

100.96

99.47

99.82

101.08

100.08

99.76

99.84

98.92

Formulae based on 4 oxygen atoms
P

0.965 0.986 0.962 0.971 0.988 0.955 0.967 0.976

0.002 0.002 0.002 0.002 0.002 0.005 0.005 0.005

0.025 0.009 0.020 0.017 0.012 0.030 0.016 0.014

Sum B

0.992 0.997 0.985 0.990 1.002 0.991 0.987 0.995

0.067 0.018 0.067 0.098 0.034 0.086 0.048 0.037

0.024 0.015 0.009 0.022 0.010 0.010 0.044 0.011

0.096 0.064 0.045 0.029 0.032 0.045 0.038 0.011

0.133 0.081 0.145 0.137 0.111 0.140 0.145 0.141

0.302 0.270 0.338 0.316 0.312 0.333 0.339 0.356

0.039 0.045 0.045 0.040 0.046 0.044 0.044 0.050

0.146 0.215 0.166 0.136 0.203 0.159 0.150 0.195

0.053 0.134 0.067 0.066 0.114 0.063 0.066 0.101

0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.000

0.040 0.100 0.043 0.044 0.075 0.040 0.040 0.050

0.005 0.008 0.003 0.004 0.005 0.004 0.003 0.002

0.017 0.019 0.011 0.008 0.010 0.011 0.010 0.005

0.002 0.001 0.001 0.001 0.000 0.000 0.000 0.000

0.006 0.004 0.004 0.004 0.003 0.004 0.004 0.003

0.001 0.001 0.001 0.002 0.001 0.001 0.001 0.001

0.007 0.001 0.002 0.002 0.002 0.001 0.002 0.002

0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001

0.000 0.000 0.026 0.000 0.000 0.000 0.000 0.000

0.077 0.028 0.062 0.107 0.041 0.074 0.089 0.044

0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

Sum A

1.017 1.006 1.035 1.016 0.999 1.017 1.024 1.008

La/Nd

0.91

0.38

0.87

1.00

0.55

0.88

0.96

0.72

La/Sm

2.52

0.60

2.17

2.07

0.97

2.22

2.20

1.40

La/Gd

3.32

0.81

3.34

3.12

1.48

3.50

3.59

2.81

S, Al, Sr below detection limit.

important  role  of  magmatic  fractional  crystallization  during
monazite growth and effective separation from feldspar-rich,
residual magma probably of granitic composition, where Eu
in divalent form is preferentially bounded in feldspars, espe-
cially  Ca-bearing  plagioclase.  Strong  negative  Eu-anomaly
(Eu/Eu*  ~ 10

—2

magnitude) is a characteristic feature of gra-

nitic rocks that originated from melting of crustal rocks (Bea
1996). Moreover, distinct variations in La/Nd, La/Sm, La/Gd,
and La/Y ratios also document an effective fractionation of
REEs during monazite precipitation.

Uraninite is a relatively widespread

accessory  mineral  in  peraluminous
leucogranites as well as abyssal to rare-
element  granitic  pegmatites  (e.g.  Bea
1996;  Černý  &  Ercit  2005;  McKechnie
et al. 2012). The Visole pegmatite con-
tains euhedral uraninite inclusions in al-
bite  and  spessartine-almandine  and
minute  anhedral  inclusions  in  zircon
from  this  pegmatite.  The  euhedral  ura-
ninite  shows  Th-rich  compositions  (2.5
to 3.7 wt. % ThO

), which are a charac-

teristic feature of magmatic uraninite
(usually with 1 to 20 wt. % ThO

; Bea

1996; Finch & Mukarami 1999; Förster
1999;  Hazen  et  al.  2009;  Petrík  &
Konečný  2009),  in  contrast  to  Th-poor
uraninite  (usually  < 0.5 wt. %  ThO

)

from hydrothermal and sedimentary oc-
currences  (e.g.  Alexandre  &  Kyser
2005;  Deditius  et  al.  2007).  Analogous
primary  magmatic  inclusions  of  ura-
ninite  in  garnet  have  been  locally  de-
scribed  from  peraluminous  granites
(Petrík  &  Konečný  2009)  and  granitic
pegmatites (Sen et al. 2009; Lima et al.
2012).  On  the  contrary,  the  anhedral
uraninite inclusions in zircon are proba-
bly  products  of  subsolidus  degradation
of the metamict host mineral.

Age of the pegmatite

Both monazite and uraninite show

Miocene  ages  between  ca.  20  and
14 Ma.  Our  results  of  monazite  chemi-
cal dating (17.2 ± 1.8 Ma) are consistent
with LA ICP-MS dating of zircon in to-
nalite  from  the  eastern  part  of  the  Po-
horje  pluton  with  a  concordant  age  of
18.6 ± 0.1 Ma  (Fodor  et  al.  2008),  and
K-Ar ages (20.3 ± 1.1 Ma to 14.9 ± 0.6 Ma;
Fodor et al. 2008; Trajanova et al. 2008)
of  biotite,  amphibole  and  feldspar  from
gabbros, tonalites, granodiorites, granitic
porphyries  and  volcanic  rocks  (mainly
dacites)  of  the  Pohorje  Mountains.  The
younger  age  of  the  uraninite  ( ~ 14 Ma)
is  probably  due  to  episodic  partial  loss

of Pb. Therefore, age dating of the Visole pegmatite reveals
its origin during the Miocene calc-alkaline plutonic-volcanic
activity.

Our dating results represent the first direct evidence of

Neogene  granitic  pegmatites  in  the  Pohorje  Mountains  as
well  as  in  broader  area  of  the  Eastern  Alps.  Populations  of
Alpine,  Paleogene  to  Neogene  granitic  pegmatites  are  rela-
tively scarce in Europe, in comparison to the Paleozoic and
Precambrian  pegmatite  fields.  They  are  concentrated  only
along the young Alpine-orogen related, post-collisional fault

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Fig. 8. Monazite chemical dating from the Visole pegmatite.
a – Age histogram (Ma); b – Pb vs. Th* diagram (wt. %).
Th* = Th + 3.15U (wt. %).

Fig. 7. Th vs. U substitution diagram of uraninite from the Visole
pegmatite (atomic proportions).

Position/Anal.

in Ab/1

in Gar/2

in Gar/3

in Gar/4

0.19

0.15

0.18

0.16

SiO

0.08

0.07

0.10

0.26

ThO

3.00

3.20

2.45

3.66

90.65

90.24

90.98

88.90

0.97

0.51

0.42

0.56

0.20

0.17

0.14

0.19

0.36

0.30

0.37

0.36

0.04

0.08

0.09

0.40

0.32

0.24

0.33

0.23

0.19

0.31

0.32

0.36

0.27

0.20

0.27

0.14

0.19

0.11

0.38

0.19

0.16

0.19

0.54

0.49

0.48

0.49

0.12

0.11

0.12

0.20

0.21

0.17

0.16

0.11

0.12

0.15

0.05

FeO

0.00

0.81

0.86

1.92

PbO

0.17

0.16

Total

98.14

97.74

97.77

98.30

Formulae based on 2 oxygen atoms
As

0.004

0.003

0.005

0.011

0.031

0.033

0.025

0.037

0.907

0.905

0.911

0.871

0.023

0.012

0.010

0.013

0.003

0.002

0.003

0.006

0.005

0.006

0.001

0.006

0.005

0.004

0.005

0.004

0.003

0.005

0.004

0.003

0.004

0.002

0.003

0.002

0.006

0.003

0.002

0.003

0.008

0.007

0.002

0.003

0.002

0.001

0.002

0.001

0.000

0.031

0.032

0.071

0.002

Sum cat.

1.017

1.028

1.049

U/Th

29.3

27.4

36.4

23.5

Table 6: Representative compositions of uraninite (wt. %) from the
Visole pegmatite.

S, P, Al, La, Ho, Ca, Sr below detection limit.

zones between the continental fragments, such as the Peri-
adriatic, Aegean, and Corsica-Apulia zones.

A province of Oligocene granitic pegmatites, locally con-

taining rare-element mineralization with beryl, columbite,
euxenite, vigezzite and other Nb-Ta-(Ti-Y-REE) phases, ga-
dolinite, schorl-elbaite, monazite, xenotime, etc., occurs to-

gether  with  Paleogene  granitic  rocks  along  the  Periadriatic
(Insubric) line in the Central and Western Alps (e.g. Wenger
&  Armbruster  1991;  Aurisicchio  et  al.  2001;  Guastoni  et  al.
2008;  Guastoni  2012).  The  radiometric  age  of  the  pegmatite
crystallization  along  the  Insubric  line  (Isorno-Orselina  and
Monte  Rosa  zones)  was  determined  by  the  isotopic  U-Pb
method  on  monazite  and  xenotime  in  the  interval  of  29  to
25 Ma,  whereas  the  Rb-Sr  as  well  as  Ar-Ar  muscovite  and
biotite dating yielded cooling ages of 25 to 19 Ma (Schärer et
al. 1996). Analogous isotopic U-Pb results on monazite, xeno-
time  and  zircon  (29.2  to  26.2 ± 0.2 Ma)  were  obtained  from
aplites and pegmatites along the Centovalli line, Italy (Romer
et al. 1996). A slightly older age of 32.7 ± 3.2 Ma has been ob-
tained by total U-Th-Pb m-PIXE method on cheralite from the
beryl  (emerald)  and  Nb-minerals  bearing  pegmatites  of  the
Vigezzo Valley, Italy (Guastoni & Mazzoli 2007).

Intrusions of late Cretaceous, Paleogene to early Miocene

granitic rocks and related pegmatites are widespread in the

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Rhodope  Massif  of  the  Aegean  Zone,  Greece  and  Bulgaria
(e.g. Kilias & Mountrakis 1998; Soldatos et al. 2008; Pipera
et  al.  2013).  Locally,  Paleogene  rare-element  granitic  peg-
matites  with  beryl  (emerald)  and  columbite-group  minerals
were described, for example, the Rila emerald-bearing peg-

Table 7: Measured and corrected element concentrations and chemical ages of monazite and uraninite calculated by Montel et al. (1996).

Sample/
Crystal/Point

wt. %

Ucor

wt. %

Pbcor
wt. %

Th 2σ

U 2σ

Pb 2σ

Age (Ma) ± Ma (1σ)

Monazite

Vi-11A/Mnz1/1

6.6584

2.5440

0.0518

3.6545

2.4668

0.0053

0.0368

0.0217

0.0055

8.3

9.5

Vi-11A/Mnz1/2

6.8724

2.0823

0.0467

2.6343

2.0026

0.0108

0.0373

0.0197

0.0055

18.5

9.5

Vi-11A/Mnz1/3

6.5002

1.7280

0.0354

2.3948

1.6526

0.0026

0.0363

0.0182

0.0055

5.0

8.8

Vi-11A/Mnz2/1

1.6698

1.0291

0.0277

2.0326

1.0097

0.0069

0.0211

0.0152

0.0055

32.1

25.8

Vi-11A/Mnz2/2

1.7163

1.4795

0.0250

2.3883

1.4596

0.0003

0.0213

0.0170

0.0055

0.9

11.3

Vi-11A/Mnz2/3

1.6705

1.7814

0.0339

3.0169

1.7620

0.0025

0.0211

0.0183

0.0055

7.9

13.6

Vi-11A/Mnz2/4

3.7126

0.6706

0.0182

1.0190

0.6275

0.0048

0.0283

0.0137

0.0054

19.0

21.4

Vi-11A/Mnz2/5

3.3254

1.0960

0.0211

1.5267

1.0574

0.0029

0.0271

0.0155

0.0054

9.8

15.2

Vi-11A/Mnz2/6

3.3736

1.0167

0.0177

1.1831

0.9776

0.0031

0.0273

0.0152

0.0055

10.8

16.1

Vi-11A/Mnz3/1

6.5312

0.9852

0.0347

1.6657

0.9094

0.0097

0.0364

0.0150

0.0054

23.3

13.1

Vi-11A/Mnz4/1

7.0708

1.3520

0.0397

2.1618

1.2700

0.0085

0.0377

0.0165

0.0054

17.3

11.1

Vi-11A/Mnz4/2

6.9462

1.1500

0.0304

1.6406

1.0694

0.0049

0.0374

0.0157

0.0054

10.8

12.4

Vi-11A/Mnz4/3

6.7646

1.0736

0.0305

1.6057

0.9951

0.0057

0.0371

0.0155

0.0055

13.1

12.6

Vi-11A/Mnz4/4

5.6341

1.0319

0.0196

0.5416

0.9665

0.0081

0.0339

0.0152

0.0054

21.1

14.2

Vi-11A/Mnz4/5

7.8113

0.9915

0.0361

1.6655

0.9009

0.0090

0.0395

0.0150

0.0055

19.0

11.7

Vi-11A/Mnz4/6

6.2849

1.1357

0.0228

0.7206

1.0628

0.0083

0.0357

0.0157

0.0054

19.5

12.8

Vi-11A/Mnz5/1

5.9603

1.1018

0.0202

0.4710

1.0327

0.0089

0.0349

0.0157

0.0054

21.9

13.4

Vi-11A/Mnz5/2

5.6102

1.0531

0.0231

0.6103

0.9880

0.0110

0.0338

0.0153

0.0054

28.3

14.2

Vi-11A/Mnz5/3

9.6117

2.3708

0.0388

1.1099

2.2593

0.0147

0.0439

0.0209

0.0055

19.7

7.5

Vi-11A/Mnz5/4

5.8688

1.4954

0.0249

0.8494

1.4273

0.0098

0.0345

0.0171

0.0054

21.2

11.9

Vi-11A/Mnz5/5

5.8267

1.2753

0.0185

0.7184

1.2077

0.0048

0.0344

0.0163

0.0054

11.2

13.0

Vi-11A/Mnz5/6

9.0976

1.3160

0.0280

0.8394

1.2105

0.0075

0.0426

0.0165

0.0055

13.2

9.6

Vi-11A/Mnz5/7

4.1892

1.0355

0.0164

0.6877

0.9869

0.0058

0.0298

0.0153

0.0055

17.8

17.1

Vi-11A/Mnz5/8

5.4729

1.0999

0.0206

0.6083

1.0364

0.0087

0.0335

0.0155

0.0054

22.4

14.1

Vi-11B/Mnz1/1

2.9026

1.1188

0.0245

1.8491

1.0851

0.0036

0.0257

0.0155

0.0054

12.7

17.2

Vi-11B/Mnz1/2

2.7429

1.1113

0.0282

2.0800

1.0795

0.0051

0.0250

0.0155

0.0055

18.6

20.6

Vi-11B/Mnz1/3

2.7640

0.9572

0.0182

1.5828

0.9251

0.0003

0.0251

0.0148

0.0054

1.3

12.5

Vi-11B/Mnz2/1

8.2279

1.0965

0.0354

1.7301

1.0011

0.0069

0.0405

0.0155

0.0054

13.6

10.8

Vi-11B/Mnz2/2

7.1601

1.2694

0.0347

1.8262

1.1863

0.0069

0.0379

0.0162

0.0054

14.3

11.3

Vi-11B/Mnz2/3

6.6512

1.2046

0.0332

2.1661

1.1274

0.0026

0.0366

0.0159

0.0054

5.7

9.9

Vi-11B/Mnz2/4

7.2051

1.0285

0.0409

1.7515

0.9449

0.0139

0.0379

0.0152

0.0054

30.8

12.2

Vi-11B/Mnz2/5

7.8887

1.1306

0.0331

1.7451

1.0391

0.0050

0.0397

0.0157

0.0054

10.0

11.5

Vi-11B/Mnz2/6

7.6380

1.1106

0.0358

1.7208

1.0220

0.0084

0.0391

0.0155

0.0054

17.4

11.3

Vi-11B/Mnz2/7

5.8890

1.0730

0.0324

1.8447

1.0047

0.0065

0.0345

0.0153

0.0054

16.3

13.6

Vi-11B/Mnz2/8

6.6579

1.2211

0.0426

2.1020

1.1439

0.0128

0.0367

0.0160

0.0054

28.0

12.0

Vi-11B/Mnz2/9

8.3723

1.0869

0.0451

1.6589

0.9898

0.0172

0.0409

0.0155

0.0054

33.7

10.8

Vi-11B/Mnz2/10

8.0745

1.0380

0.0322

1.6432

0.9443

0.0048

0.0402

0.0153

0.0054

9.9

11.5

Vi-11B/Mnz3/1

3.6593

2.7400

0.0293

1.3115

2.6976

0.0129

0.0281

0.0224

0.0054

24.0

10.2

Vi-11B/Mnz3/2

4.6382

4.4625

0.0371

1.3971

4.4087

0.0182

0.0309

0.0300

0.0054

22.2

6.7

Vi-11B/Mnz4/1

3.1304

0.7112

0.0165

0.7230

0.6749

0.0073

0.0264

0.0139

0.0054

31.1

23.5

Vi-11B/Mnz4/2

5.7897

0.8042

0.0177

0.3437

0.7370

0.0081

0.0343

0.0143

0.0053

22.4

15.0

Vi-11B/Mnz4/3

4.8698

0.7331

0.0226

0.9735

0.6766

0.0078

0.0317

0.0139

0.0053

25.0

17.4

Vi-11B/Mnz4/4

4.6832

0.7439

0.0191

0.4822

0.6896

0.0099

0.0312

0.0140

0.0053

32.4

17.8

Vi-11B/Mnz4/5

6.6620

1.1383

0.0295

1.2761

1.0610

0.0085

0.0367

0.0156

0.0054

19.0

12.3

Vi-11B/Mnz4/6

3.5614

0.7548

0.0161

0.5947

0.7135

0.0075

0.0279

0.0141

0.0054

29.2

21.3

Vi-11BMnz5/1

3.5501

1.1065

0.0156

0.3896

1.0653

0.0092

0.0277

0.0154

0.0053

30.2

17.7

Vi-11B/Mnz5/2

4.0571

0.8995

0.0173

0.6979

0.8524

0.0068

0.0293

0.0146

0.0054

22.7

18.3

Vi-11B/Mnz5/3

3.8955

0.9903

0.0155

0.4369

0.9451

0.0081

0.0288

0.0149

0.0054

26.4

18.0

Uraninite

Vi-11B/Urn1/1

2.6395

79.9392

0.1683

0.7606

79.9086

0.1610

0.0236

0.3997

0.0061

14.3

0.6

Vi-11B/Urn1/2

2.9394

79.5689

0.1681

0.7525

79.5348

0.1604

0.0245

0.3979

0.0061

14.3

0.6

Vi-11B/Urn1/3

2.9768

79.4774

0.1694

0.7124

79.4429

0.1621

0.0247

0.3975

0.0061

14.4

0.6

Vi-11B/Urn2/1

3.1819

79.3887

0.1607

0.4202

79.3518

0.1561

0.0253

0.3971

0.0061

13.9

0.6

Vi-11B/Urn2/2

2.8147

79.5823

0.1628

0.4018

79.5496

0.1590

0.0242

0.3980

0.0061

14.2

0.6

Vi-11B/Urn2/3

2.1510

80.2243

0.1654

0.3293

80.1993

0.1636

0.0220

0.4011

0.0061

14.5

0.6

Vi-11B/Urn2/4

3.1790

78.7474

0.1635

0.4128

78.7105

0.1590

0.0253

0.3939

0.0061

14.3

0.6

Vi-11B/Urn2/5

2.8960

79.0024

0.1612

0.4096

78.9688

0.1572

0.0244

0.3951

0.0061

14.1

0.6

Vi-11B/Urn2/6

3.2168

78.4043

0.1586

0.4401

78.3670

0.1537

0.0254

0.3922

0.0061

13.9

0.6

matite in Bulgaria shows Late Eocene Ar-Ar phlogopite age
of 34.2 ± 0.4 Ma (Alexandrov et al. 2001).

On the other hand, Late Miocene to Pliocene pegmatites

are associated with granitic rocks in the Tuscany magmatic
province, mainly in the Monte Capanne pluton of the Island

143

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of  Elba.  Rare-element  granitic  pegmatites  with  Li-bearing
tourmalines (schorl to fluorelbaite) and Nb-Ta oxide minerals
(mainly members of columbite and euxenite group minerals)
form  dikes  and  fillings  of  miarolitic  vugs  in  parental
monzogranites  (Pezzotta  2000;  Aurisicchio  et  al.  2002;
Guastoni et al. 2008; Guastoni 2012). The granitic rocks and
related pegmatite dikes of the island of Elba were emplaced
during  the  Late  Miocene  (Tortonian  to  Messinian),  ~ 8  to
6.7 Ma ago, as determined by the Rb-Sr and Nd whole-rock
and mineral-rock isochron dating (Ferrara & Tonarini 1985;
Dini  et  al.  2002,  and  references  therein).  Similar  pegmatite
and aplite dykes cut monzogranites in the adjacent plutons of
Montecristo (7.1 Ma; Innocenti et al. 1997) and Giglio islands
( ~ 5 Ma;  Peccerillo  2005).  However,  the  youngest  plutonic
activity  of  the  Tuscany  magmatic  province  terminated  dur-
ing the Pliocene at 4.5 to 4.3 Ma ago, while volcanism of the
Roman and Tuscan provinces has been active up to the Qua-
ternary (Dini et al. 2002; Peccerillo 2005).

Pegmatite source and evolution

The mineralogical character of the Visole pegmatite, rich in

Al-rich  silicate  minerals  (muscovite,  spessartine-almandine),
indicate  its origin  from  a peraluminous  magma  source.  The
Miocene age of the Visole pegmatite is consistent with the ad-
jacent  Pohorje  pluton.  Consequently,  a  direct  origin  of  such
magma  by  fractionation  of  the  Pohorje  calc-alkaline  grano-
diorites-tonalites  is  not  probable.  However,  we  can  assume
the formation  of  small  leucogranitic  stocks  which  possibly
originated  by  partial  anatexis  of  a peraluminous  metapelitic
protolith  due  to  intrusion  of  the  Pohorje  pluton.  Metapelitic
rocks  (gneisses,  micaschists)  overprinted  by  Cretaceous
HP-UHP  metamorphism  are  widespread  lithologies  around
the Pohorje pluton (e.g. Janák et al. 2004, 2009; Krenn et al.
2009;  Kirst  et  al.  2010).  Successive  fractionation  of  the
leucogranite  magma  from  these  satellite  bodies  around  the
Pohorje  pluton  resulted  in  formation  of  the  pegmatite  melt
which escaped and intruded into the host metamorphic rocks.
Such a petrogenetic scenario corresponds to recent knowledge
concerning the origin of evolved granitic pegmatites with rare-
element specialization (London 2008 and references therein).

An application of the monazite—garnet geothermometry

(Pyle et al. 2001) indicates a temperature of  ~ 495 ± 30 °C (at
estimated 4 to 5 kbar pressure) for precipitation of the mona-
zite—garnet—apatite—plagioclase  assemblage.  Such  tempera-
tures are common for the solidification of evolved pegmatite
magma (London 2008 and references therein). However, the
geothermometer  was  calibrated  for  the  mineral  equilibrium
in metamorphic rocks (metapelites) and the resulting temper-
atures represent only approximate values.

Conclusions

The Miocene granitic pegmatite intruding UHP metamor-

phic rocks at Visole in the Pohorje Mts, shows a muscovite –
rare-element, or rare-element, beryl-columbite and LCT
geochemical affinity (sensu Černý & Ercit 2005). Chemical
dating of monazite and uraninite ( ~ 17 to 14 Ma) clearly re-

veals  the  Miocene  age  of  the  pegmatite,  the  emplacement
and solidification of which was coeval with the calc-alkaline
plutonic and volcanic activity in the Pohorje Mountains. The
Visole pegmatite represents the first documented example of
rare-element granitic pegmatite of Miocene age in the East-
ern  Alps  and  it  belongs  to  the  youngest  populations  of  gra-
nitic  pegmatites  in  Europe.  It  is  younger  than  Paleogene
pegmatite populations in the Rhodope Massif and along the
Periadriatic  (Insubric)  line  but  older  than  the  Late  Miocene
to Pliocene pegmatites of the Tuscany magmatic province.

The apparently negative Eu-anomaly of monazite and the

composition  of  minerals  document  an  important  role
of magmatic  fractionation  from  a  parental  granitic  source.
However,  the  pegmatite  did  not  originate  directly  from  the
adjacent  tonalitic-granodioritic  rocks  of  the  Pohorje  pluton.
The pegmatite magma was probably generated by magmatic
fractionation  of  possible  small  satellite  leucogranitic  stocks
around the Pohorje pluton. They originated from partial ana-
texis  of  a  peraluminous  metapelitic  source  during  emplace-
ment of the Pohorje tonalite-granodiorite pluton.

Acknowledgments: The authors thank A. Guastoni, R. Škoda
and  I.  Petrík  for  constructive  criticism  and  suggestions  that
improved the manuscript. The paper has also benefitted from
discussion  with  M.  Kováč.  This  work  was  financially  sup-
ported by the Slovak Research and Development Agency un-
der  the  contract  Nos.  APVV-0080-11,  APVV-0557-06,  and
APVV-VVCE-0033-07 SOLIPHA, and the Slovak Scientific
Grant Agency VEGA (Grant No. 2/0013/12).

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