Electron-microprobe dating of monazites from Western Carpathian.pdf

Int J Earth Sci (Geol Rundsch) (2003) 92:86–98

DOI 10.1007/s00531-002-0300-0

ORIGINAL PAPER

F. Finger · I. Broska · B. Haunschmid · L. Hrasko

M. Kohút · E. Krenn · I. Petrík · G. Riegler · P. Uher

Electron-microprobe dating of monazites from Western Carpathian

basement granitoids: plutonic evidence for an important Permian

rifting event subsequent to Variscan crustal anatexis

Received: 30 August 2001 / Accepted: 24 July 2002 / Published online: 9 November 2002

Abstract Accessory monazites from 35 granitoid sam-

ples from the Western Carpathian basement have been

analysed with the electron microprobe in an attempt to

broadly constrain their formation ages, on the basis of

their Th, U and Pb contents. The sample set includes rep-

resentative granite types from the Tatric, Veporic and

Gemeric tectonic units. In most cases Lower Carbonifer-

ous (Variscan) ages have been obtained. However, a

much younger mid-Permian age has been recorded for the

specialised S-type granites of the Gemeric Unit, and

several small A- and S-type granite bodies in the Veporic

Unit and the southern Tatric Unit. This distinct Permian

plutonic activity in the southern part of the Western

Carpathians is an important, although previously little

considered geological feature. It appears to be not related

to the Variscan orogeny and is interpreted here to reflect

the onset of the Alpine orogenic cycle, with magma gen-

eration in response to continental rifting. The voluminous

Carboniferous granitoid bodies in the Tatric and Veporic

units comprise S- and I-type variants which document

crustal anatexis accompanying the collapse of a com-

pressional Variscan orogen sector. The Variscan magmas

were most likely produced through the remelting of a

subducted Precambrian volcanic arc-type crust which in-

cluded both igneous and sedimentary reworked volcanic-

arc material. Although the 2σ errors of the applied dating

method are quite large and typically ±10–20 Ma for

single samples, it would appear from the data that the Vari-

scan S-type granitoids (333–367 Ma) are systematically

older than the Variscan I-type granitoids (308–345 Ma).

This feature is interpreted in terms of a prograde tempera-

ture evolution in the deeper parts of the post-collisional

Variscan crust. In accordance with recently published zir-

con ages, this study shows that the Western Carpathian

basement must be viewed as a distinct “eastern” tectono-

magmatic province in the Variscan collision zone, where

the post-collisional crustal melting processes occurred

~20 Ma earlier than in the central sector (South Bohemian

Batholith, Hohe Tauern Batholith).

Keywords Western Carpathians · Monazite ·

Geochronology · Granitoids · Variscan orogeny ·

Permian rifting

Introduction

The ability of the present generation of electron micro-

probes to analyse Pb at the 0.1-wt% level accurately has

caused a renewed interest in the chemical age dating of

U- and Th-rich minerals. In particular, the abundant ac-

cessory mineral monazite has turned out to be extremely

suitable for this dating technique due to its mostly undis-

turbed U–Th–Pb system, with typically high radiogenic

lead contents and subordinate portions of common lead

(cf. Parrish 1990; Suzuki et al. 1991; Montel et al. 1996).

Although chemical dating of monazite with the elec-

tron microprobe (EMP) can, of course, not compete in

terms of precision and reliability with modern monazite

or zircon ages obtained by isotope dilution/mass spec-

trometry or SHRIMP, its application can be useful in

areas where little previous geochronological work has

been undertaken, in order to obtain a first quick over-

view. Here we report EMP monazite ages for basement

granitoids from the Western Carpathians. These granito-

ids have been investigated in recent years in some detail

with reference to their petrology, chemistry, possible

sources and tectonothermal environments (Petrík et al.

1994; Petrík and Kohút 1997; Petrík 2000 and references

therein). A correlation of the petrogenetic data with a

geochronological time scale is important in order to un-

) · B. Haunschmid · E. Krenn · G. Riegler

Institut für Mineralogie der Universität Salzburg,

Hellbrunnerstrasse 34, 5020 Salzburg, Austria

e-mail: friedrich.finger@sbg.ac.at

I. Broska · I. Petrík · P. Uher

Geological Institute of the Slovak Academy of Sciences,

Dubravska 9, 84225 Bratislava, Slovakia

L. Hrasko · M. Kohút

Dionyz Stúr Institute of Geology/

Geological Survey of Slovak Republic,

Mlynska dolina 1, 81704 Bratislava, Slovakia

✉

F. Finger (

Fig. 1 Distribution of granitoid

rocks in the Western Carpathian

basement and sample locations

of the present study. Abbrevia-

tions of basement massifs (“the

core mountains”): MK Malé

Karpaty Mts., PI Povazsky

Inovec Mts., T Tríbec Mts.,

S Suchy Massif, Z Ziar Mts.,

MF Malá Fatra Mts., VF Ve l k á

Fatra Mts., NT Nízke Tatry

Mts., VT Vysoké Tatry Mts.,

SR Slovenské Rudohorie Mts.

Inset shows the position of the

Western Carpathians ( star )

within the Alpine-Carpathian

orogen

derstand the processes involved in the basement evolu-

tion of the Western Carpathians.

ever, there are other authors who consider this phase of

Permo-Triassic extension as a direct consequence of late

Variscan plate tectonics, caused by back-arc spreading

behind a northward-dipping subduction system at the

southern Variscan fold belt flank (e.g. Stampfli et al.

2001).

Geological background

The Western Carpathian section of the Alpine-Carpathi-

an arc is commonly divided into three major, Alpine

basement-bearing tectonic units which were juxtaposed

through north-directed thrusting during the Upper Creta-

ceous. These are, from north to south, the Tatric, Veporic

and Gemeric units (Fig. 1). Traditionally, the Western

Carpathian basement is considered in a broad sense to be

“Variscan”. Basement granitoids are most abundant in

the Tatric and Veporic units. They are exposed in horst

structures which were exhumed during the Alpine oroge-

ny in the Eocene-Miocene, and they are termed the “core

mountains” (Fig. 1). Mostly an older roof of metamor-

phic material (orthogneisses, paragneisses and amphibol-

ites) is preserved around the granitoid bodies.

The effects of Alpine regional metamorphism were

relatively minor in the Tatric Unit at very low- to low-

grade PT conditions but reached amphibolite facies

grades in the Veporic Unit (Plasienka et al. 1999; Janak

et al. 2001). The latter constitutes a certain danger for

the method of monazite dating because of the potential

metamorphic disturbance of the U–Th–Pb system. The

basement of the Gemeric Unit consists mainly of low-

grade metamorphic formations with only small granite

bodies. Both experienced Alpine greenschist facies re-

gional metamorphism (Faryad 1992).

The post-Variscan history of the Western Carpathians

involved continental rifting in the Permian and the open-

ing of the Meliata Ocean in the Triassic (Plasienka et al.

1997). Many geologists regard this as the onset of the

Alpine orogenic cycle (e.g. Neubauer et al. 2000). How-

Lithology of the basement granitoids

Following the classification of Chappell and White

(1974), the Western Carphathian basement granitoids

have been divided into S-types and I-types (Cambel and

Petrík 1982; Petrík et al. 1994; Petrík and Kohút 1997;

Broska and Uher 2001). Most “core mountains” contain

both S- and I-type granite units (Fig. 1).

The S-type units comprise mainly granites to leuco-

granites and a few tonalites to granodiorites, and are

characterised by moderately peraluminous compositions.

They contain Al-rich biotite and, except for some tonal-

ites, primary muscovite and occasionally sillimanite or

garnet. According to the petrological investigations of

Petrík and Broska (1994), the S-type melts had low

water contents, reduced oxygen activities, and they de-

veloped a distinctive accessory mineral paragenesis of

apatite, monazite, ilmenite and zircon with dominant

(211) + (110) faces.

The I-type units comprise mainly tonalites and grano-

diorites with metaluminous to weakly peraluminous

(subaluminous) compositions. Mafic minerals are Al-

poor biotite ± hornblende. The accessory mineral par-

agenesis is typically zircon + allanite + magnetite +

sphene + epidote. Monazite is comparably rare. How-

ever, as shown in this study, small monazite grains can

mostly be found as well. Higher oxygen activities and

water contents have been inferred for the I-type melts by

Sr diagram, fields

for the S- and I-type granitoids cover almost the same

range, with Sr i from ~0.705 to 0.710, and εNd i from

–1 to –5. Similarly to the I-types, the S-types often

display high Sr and low Rb concentrations which point

to little evolved crustal sources, probably volcanic arc-

type crust. An exception are the S-type granites of the

Gemeric Unit which have significantly higher Rb/Sr and

Sr initial ratios (0.710–0.713) and were probably derived

from a more evolved, metasedimentary crustal source

(Petrík and Kohút 1997; Kohút et al. 1999; Petrík 2000).

Furthermore, a distinct group of small plutons broadly

matching the A-type granite classification (Collins et al.

1982; Eby 1990) has been recognised in the Western

Carpathians. These have been found in the Veporic and

Gemeric units but not in the Tatric basement, and have

been considered to be post-orogenic Variscan plutons

(Uher and Broska 1996). Boulders of such A-type gran-

ites have also been identified in the Cretaceous flysch of

the Klippen belt. The A-type melts were reduced, slight-

ly peraluminous and high in fluorine (Uher and Broska

1996).

Not included in our study are the granitoid ortho-

gneisses which occur in the metamorphic roof forma-

tions of the granitoids, because of their presumably com-

plex monazite systematics and the difficulty to distin-

guish between metamorphic and magmatic monazite ag-

es. According to Petrík and Kohút (1997), these rocks

are largely of the S-type.

Nd–

Devonian and Permian. It would appear from these data

that the S-type granitoids formed close to 350 Ma

(Shcherbak et al. 1990; Michalko et al. 1998) whereas

for the I-type granitoids much younger formation ages,

close to 300 Ma, have been suggested (Bibikova et al.

1988, 1990; Broska et al. 1990). However, these ages for

the I-type granitoids were often inferred from the

206 Pb/ 238 U ratios of data points considered as concordant

but having large errors in the 207 Pb/ 235 U ratios. Clearly,

these data bear a high uncertainty. Likewise, the geologi-

cal significance of some lower intersect ages (e.g.

Michalko et al. 1998) remains unclear. Recently, CL-

controlled single-grain zircon dating has provided ages

between ~360 and ~340 for S-type granites from the

Western Tatric Mts., and ages of ~335 and ~315 Ma for

I-type granitoids from the High Tatra (Poller et al.

1999b, 2000a). S-type granitoids from Velká Fatra gave

a concordant monazite age of 340±2 Ma and a zircon age

of 337±11 Ma (Kohút et al. 1997).

For one of the A-type plutons (Hroncok granite), zir-

con geochronology has provided both a mid-Permian,

upper intersect age (Kotov et al. 1996) and a Triassic,

lower intersect age (Putis et al. 2000). Zircons from an

A-type granite boulder in the Klippen belt provided a

well-defined five-point discordia with an upper intersect

age of 274±13 Ma (Uher and Puskharev 1994). All these

data suggest that the A-type granites in the Western

Carpathians are comparably young. Only the Gemeric

S-type granites have been considered to be of a similar

Permian age, based on Rb–Sr WR data (Cambel et al.

1989). For these granites, however, a Cretaceous intru-

sion age has also been considered possible (Vozár et al.

1996; Vozárova et al. 2000). Recently obtained single-

grain zircon ages confirm the Permian age estimate

(Poller et al. 2000c).

For orthogneisses from the Tatra Mts., protolith ages

of ~360–400 Ma have been determined (Poller et al.

2000a). The age of Variscan regional metamorphism in

the Tatra Mts. has been constrained at 356±7 Ma by con-

cordant zircon data from migmatitic paragneisses (Poller

and Todt 2000).

Previous geochronological data

Geochronological work on the Western Carpathian

granitoids commenced in the late 1950s with the K–Ar

method (Kantor 1959), followed by Rb–Sr mineral and

whole-rock data from the late 1960s onwards. Based on

this early work, it has been proposed that the basement

granitoids are between ca. 250 and 400 Ma old (Cambel

et al. 1990; Kohút et al. 1996 and references therein).

However, Král (1994) noted that, due to an incomplete

homogenisation of the Rb–Sr system during melting and

magma mixing effects, the Rb–Sr WR isochrons from

Carpathian granitoids are probably too old in many

cases, and not capable of providing reliable and precise

formation ages (see also discussion in Petrík 2000).

U–Pb zircon ages, which have been obtained from

a few localities over the past 12 years, also suggest that

the Western Carpathian granitoids formed between the

The sample set for the present study

Figure 1 illustrates where the samples for the present

study have been taken. The sample locations and brief

rock descriptions are given in Table 1. Representative

granite types from the different “core mountains” were

selected, so that a systematic comparison of I-type and

S-type subunits could be made. Although the I-type

granitoids contain on average less and smaller monazite

than the S-types granitoids, only a few of the major

I-type bodies could not be dated because no monazite

was found (e.g. the Shila tonalite which is widespread in

the Slovenské Rudohorie Mts., or the Dumbier granite

from the Nízke Tatry Mts.).

In the Tatric Unit, representative I- and S-type gran-

itoids were collected from the Malé Karpaty Mts., Tríbec

Petrík and Broska (1994). However, in several cases a

clear distinction between S- and I-type granitoids is not

possible, and continuous gradations seem to exist be-

tween both groups (Cambel and Petrík 1982).

Sr and Nd isotope data (Petrík and Kohút 1997;

Kohút et al. 1999; Poller et al. 1999a; Petrík 2000; Poller

et al. 2001), together with the widespread presence of

inherited zircon components (e.g. Broska et al. 1990;

Michalko et al. 1998; Poller et al. 1999b), suggest that

both the S-type and I-type granitoids were derived main-

ly from crustal sources. In the

Table 1 The dated samples: locations (cf. Fig. 1) and brief petro-

graphic characteristics (references: 1 Macek et al. 1982; 2 Broska

and Uher 1988; 3 Broska et al. 2000; 4 Broska and Gregor 1992;

5 Broska et al. 1997; 6 Kohút 1992; 7 Uher et al. 1994; 8 Petrík

et al. 1995; 9 Hrasko et al. 1997; 10 Finger and Broska 1999)

Sample

Location

Brief characteristics

Type Ref.

Tatric Unit

ZK-50/97 Malé Karpaty Mts., Zelezná Studnicka quarry

Ms–Bt granodiorite (“Bratislava granite”) S

MM-3

Malé Karpaty Mts., Harmónia, small, abandoned quarry

Bt granodiorite (“Modra granite”)

PI-14/85 Povazsky Inovec Mts., Moravany nad Váhom, Striebornica valley

Ms–Bt granodiorite

PI-6/85

Povazsky Inovec Mts., Hlohovec, Stará Hora, road-cut

Leucotonalite

T-18

Tríbec Mts., Drsna valley, 2,500 m SE from Krnca village

Bt granodiorite

T-87

Tríbec Mts., 1,500 m SE from Krnca village, forest road-cut

Bt tonalite

T-37

Tríbec Mts., Velcice 2,800/2,000 m from elevation point Malá Kurna

Leucogranite

T-33

Tríbec Mts., elevation point Javorovy hill

Ms granite injections into mylonites

PGS-2

Suchy Mts., upper end of the Liest’any valley

Pegmatoid leucogranite

Z-4/89

Ziar Mts., abandoned Brezany quarry

Bt granite

BMF-1

Malá Fatra Mts., Bystricka quarry

Bt granodiorite

BMF-8

Malá Fatra Mts., Lipovec, Hoskora valley

Ms–Bt granite

VF-308 Velká Fatra Mts., Stanova valley, forest road-cut

Bt granodiorite (“Kornietov type”)

VF-639 Velká Fatra Mts., Blatná valley, natural outcrop

Bt granodiorite (“Kornietov type”)

VF-385 Velká Fatra Mts., Nizná Lipová, cliff on ridge

Ms–Bt granite (“Lipová type”)

VF-700 Velká Fatra Mts., Lower Matejkovo valley, prospecting gallery

Ms leucogranite (“Lubochna type”)

VF-356 Velká Fatra Mts., Upper Matejkovo valley, abandoned quarry

Bt tonalite (“Smrekovica type”)

ZK-3/89 Nízke Tatry Mts., 100 m W of terminus of the funicular to Chopok hill Bt granite

ZK-25

Nízke Tatry Mts., road Sopotnica-Hronov, end of Sopotnica valley

Bt granodiorite

ZT-11

Western Tatra, cliff next to the highest Rohace lake

Leucogranodiorite

High Tatra Mts., Strbské Pleso, cliff of waterfall “Skok”

VT-1

Bt tonalite

KJ-3

High Tatra Mts., Dolina Rybiego, Potoku valley, Poland

Leucotonalite

Klippen belt, Siroká, 1,700/2,840 m from elevation point Turfkov Ziar Granite boulder

BP-11

(851 m)

Veporic Unit

PH-9

Slov. Rud. Mts, Road Poltár-C ˇ eské Brezovo, first quarry on east side

Bt granite

ZK-19

Ms–Bt granite (“Rimavica type”)

KRO-2

Slov. Rud. Mts., Krokava, road cut 500 m below the chalet

Leucogranite vein in Rimavica granite

VG-100 Slov. Rud. Mts., Ráztocno, cliff 1 km S of Klenovsky Vepor hill

Leucogranodiorite

DL-1A

Slov. Rud. Mts., 7 km NNE Hrinová, small quarry in Slatina valley

Leucogranite dike in Sihla tonalite

VG-87

Slov. Rud. Mts., Kamenistá valley, Hroncok gamekeeper

Mylonitised leucogranite (“Hroncok type”) A

KS-1

Slov. Rud. Mts., Klenovec village, borehole KS-1, depth 528–531 m

Ms–Bt granite (“Klenovec type”)

VM-605 Nízke Tatry Mts., main ridge, 1 km W from the Král’ova Hol’a

Strongly sheared leucogranite

VM-609 Nízke Tatry Mts., southern slope of Orlová saddle, 1,750 m a.s.l.

Coarse-grained mylonitised granite

Gemeric Unit

GZ-1

Slovenské Rudohorie, Hnilec cliff, 800 m from Peklisko elevation point Leucogranite

GZ-3

Slovenské Rudohorie, Hnilec, 220 m NE from elevation point Surovec Leucogranite

GZ-15

Slov. Rud. Mts., Betliar, cliff 3,250 m SW from elevation point Volovec Leucogranite

Road Kosice-Zlata Idka, 13 km W Kosice, borehole ID-2, depth 132 m Bt-tourmaline granite

Mts., Povazsky Inovec Mts., Malá Fatra Mts., Velká

Fatra Mts., Vysoké Tatry (High Tatra) Mts., and the

Tatric part of the Nízke Tatry (Low Tatra) Mts. Samples

of S-type granites were taken from the Ziar and Suchy

massifs, and an S-type granitic boulder from the Klippen

belt was sampled as well (BP-11).

In the Veporic Unit we investigated the A-type

Hroncok granite (VG-87), a leucocratic dike (DL-1A)

considered as related to the major I-type unit in the Slov-

enské Rudohorie Mts. (Shila granite), and representative

samples from the main S-type granite units of this area

(ZK-19, ZK-100). Furthermore, small S-type granite bod-

ies and dikes from the Slovenské Rudohorie Mts. were

sampled (PH-9, KRO-2, KS-1). From the Král’ova Hol’a

Massif (Veporic part of the Nízke Tatry Mts.), two S-type

granite samples were collected (VM-605 and VM-609).

In the Gemeric Unit four granite samples from the

Hlinec, Betliar and Zlata Idka stocks were examined.

Results

General aspects

Between 3 and 18 monazite analyses were carried out

per sample. All obtained Th, U and Pb concentrations

are given in the Appendix, together with the calculated

model ages and 2σ errors. It can be seen from this com-

pilation that for single samples, the monazite model ag-

es of all analysis points are mostly consistent with each

other and overlap within their 2σ errors. There were

only two exceptions. In sample T-33 one monazite

showed significantly older model ages in its centre. This

obviously inherited core has been excluded from the

average age calculation. In sample DL-1, single monaz-

ite analyses give unrealistically low ages, deviating by

more than 2σ from the mean value. We attribute this to

local lead loss or Alpine age recrystallisation/over-

Slov. Rud. Mts., 5 km SW Murán, 850 m NW elevation point 1,018

growth effects and omitted these in the average calcula-

tions as well. Since isotope ratios cannot be determined,

however, we are aware that minor effects of inheritance,

common lead presence or lead loss on the mean age can

not be ruled out with certainty, and one has to rely on

the (fortunately well-established) empirical rule that, in

the case of the mineral monazite, these effects are usual-

ly not large.

Furthermore, it should be mentioned that in the

Veporic granites the monazites often showed marginal

alterations with the growth of secondary apatite and alla-

nite, as a consequence of the Alpine reheating (Broska

and Siman 1998). For dating, only the largest and best

preserved monazite relics were used in such cases, and

analyses points were placed at least 10 µm away from

the alterations.

The average ages for all dated samples are compiled

in Table 2. For six granitoids of this sample set, zircons

ages became recently available as well (see annotations

in Table 2). The chemical monazite ages match with

these zircon ages in all cases. This suggests that the ob-

tained monazite ages can be generally taken as reliable

and geologically meaningful.

Table 2 Average monazite ages (errors at 95% C.L.) for single

samples considered as dating granite formation

Location

Sample

Type

Age (Ma)

Tatric Unit

Malé Karpaty Mts. (MK)

ZK-50/97

355±18

MM-3

345±22

Povazsky Inovec Mts. (PI)

PI-14/85

364±17

PI-6/85

323±22

Tríbec Mts. (T)

T-18

357±13

T-87

352±17

T-37

331±22

T-33

273±17

Suchy Massif (S)

PGS-2

342±13

Ziar Mts. (Z)

Z-4/89

348±22

Malá Fatra Mts. (MF)

BMF-1

342±18

BMF-8

336±9

Velká Fatra Mts. (VF)

VF-308

333±24

VF-639

348±21

VF-385

348±18

VF-700

343±12

VF-356

308±30 a

Nízke Tatry Mts. (NT)

ZK-3/89

362±27

ZK-25

326±31

Vysoké Tatry Mts. (VT)

ZT-11

347±24 b

VT-1

327±28 c

KJ-3

317±15 d

Klippen Belt

BP-11

348±22

The S-type granitoids

Veporic Unit

Slov. Rudohorie Mts. (SR)

PH-9

357±21

ZK-19

352±13

KRO-2

367±34

The data show that at least two generations of S-type

plutons are present in the Western Carpathian basement

– Permian and Lower Carboniferous ones. Permian ages

were obtained for all four investigated samples of gran-

ites from the Gemeric Unit. Additionally, the S-type

granites VM-609 from the Nízke Tatry and KS-1

(Klenovec granite) from the Slovenské Rudohorie Mts.

(both Veporic Unit) gave a Permian age. Finally, a simi-

larly young age (273±17 Ma) was obtained for a distinct,

small S-type granite occurrence in the Tríbec Massif

(Tatric Unit), which was already considered as relatively

younger on geological grounds because it intruded late

Variscan mylonites.

All other investigated S-type granites from the Ve-

poric and Tatric units provided much higher chemical

monazite ages. The highest values were obtained from

S-type granites from the Povazsky Inovec Massif

(364±17 Ma) and the Slovenské Rudohorie Mts.

(369±30 Ma), whereas the lowest (in this Lower Car-

boniferous group) was obtained for the Kornietov grano-

diorite from the Velká Fatra Mts. (333±24 Ma). How-

ever, the relatively high errors inherent to the method of

EMP monazite dating do not allow it to be resolved

whether the Lower Carboniferous S-types intruded in

two or more independent pulses between ~360 and

330 Ma, or all very close to ~350 Ma. In any case, the

monazite ages confirm the previous view, which was

mainly based on Rb–Sr whole-rock dating and few zir-

con data, that in the Western Carpathians an important

phase of S-type granite formation occurred at the begin-

ning of the Carboniferous.

VG-100

369±30

DL-1A

321±18

VG-87

263±19 e

KS-1

266±16

Nízke Tatry Mts. (NT)

VM-605

359±17

VM-609

269±22

Gemeric Unit

Slov. Rudohorie Mts. (SR)

GZ-1

272±11

GZ-3

276±13

GZ-15

273±13

Eastern part

263±28 f

Annotations a–f refer to zircon ages obtained from the same rock

type

a 304±2 Ma (Poller et al. 2000b)

b 363±11 Ma (Poller et al. 1999b)

c 332±15 Ma (Poller et al. 1999b)

d 315±5 Ma (Poller et al. 1999b)

e 278±11 Ma (Kotov et al. 1996)

f 265±20 Ma (Poller et al. 2000c)

The I-type granitoids

The investigated I-type granitoid samples provided

chemical monazite ages between 345±22 Ma (Modra

Massif, Malé Karpaty) and 308±30 Ma (tonalite Velká

Fatra Mts.). However, these values are not in agreement

with the earlier concepts based on zircon dating, accord-

ing to which most I-type granitoids in the Western

Carpathians formed at ~300 Ma (see compilation in

Petrík and Kohút 1997). Some of the I-types, e.g. sam-

ples MM-3, T-37 and ZK-25, provided monazite ages

which, within their errors, would be even compatible

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