GeolCarp_Vol49_No3_161

GEOLOGICA CARPATHICA, 49, 3, BRATISLAVA, JUNE 1998

161167

THE BREAKDOWN OF MONAZITE IN THE WEST-CARPATHIAN

VEPORIC ORTHOGNEISSES AND TATRIC GRANITES

IGOR BROSKA

and PAVOL SIMAN

Geological Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 842 26 Bratislava, Slovak Republic; geolbros@savba.savba.sk

Slovak Geological Survey, Mlynská dolina 1, 815 00 Bratislava, Slovak Republic

(Manuscript received June 26, 1997; accepted in revised form March 24, 1998)

Abstract: The complete breakdown of monazite was observed in metagranites of the Veporic Superunit while only

slight alteration of monazite occurs in unmetamorphosed Tatric granitoids (Tribeè Mts., Malá Fatra and Stráovské

vrchy Mts.). Monazite breakdown is probably a result of the reaction monazite+annite+anorthite+quartz+fluids giv-

ing apatite+allanite+muscovite. During monazite breakdown its margins are replaced outward by apatite corona,

allanite rim and REE-rich epidote. In extreme cases monazite cores are fully consumed by apatite which occupies the

place of the former monazite. The result of such breakdown is grains with apatite cores and the allaniteREE epidote

rims. The monazite breakdown in the Veporic Superunit occurred under conditions of amphibolite facies during an

Alpine metamorphic event, although the proccess of breakdown had probably already started during the Variscan

metamorphosis. In the case of monazite from Tatric granites initial breakdown of monazite was found in the context

of Variscan subsolidus granite alteration. Only restricted mobility of the REE is supposed during the breakdown of

monazite.

Key words: Alpine metamorphism, REE mobility, monazite, allanite, granite, metagranite.

Introduction

Monazite and allanite are two of the most frequent primary

magmatic LREE acccessory mineral phases of granitoids,

however, they show an antipathetic relationship either

monazite or allanite is present in granitoids, or one of them

strongly prevails in paragenesis (Lee & Dodge 1964; Lya-

khovich 1968; Gromet & Silver 1983; Broska & Uher 1991;

Montel 1993). Generally monazite is typical of S-type, Ca-

poor or peraluminious granitoid accessory mineral paragen-

esis, while allanite is reported mainly from I-type granitoids

(Snetsinger 1967; Parrish 1990).

Both monazite and allanite can also form during meta-

morphism, where they show the dichotomy known from the

felsic magmas. Accessory monazite is rare in the green-

schist facies, rare to scarce in amphibolite facies, and quite

abundant in the granulite facies of metamorphic rocks. On

the contrary, allanite or REE-rich zoisite is common at low-

er metamorphic grades (Overstreet 1967). However, in the

Ori Dome low-grade slates (Central Pyrenees) poikiloblas-

tic monazite was described, which nucleated on small detri-

tal grains during anchimetamorphic conditions. In green-

schist facies this monazite is replaced by allanite (Bons

1988). Metamorphic monazite, as grey Eu-rich monazite, is

also known from greenschist facies (Donnot et al. 1973;

Read et al. 1987), but monazite was also reported in stauro-

lite-kyanite metamorphic grade (Mohr 1984) or staurolite-in

isograde in conditions of 525

C and 3 kb (Smith & Barreiro

1990). Franz et al. (1996) described monazite in Bavaria

newly formed at ca. 450700

C in low pressure

metapelites. The possible origin of monazite from break-

down of allanite or allanite hornblende and apatite in the au-

gen gneisses from the Swedish-Norwegian province in Cpx-

in and Opx-on isograde showed Bingen et al. (1996).

The aim of the paper is to describe the monazite being re-

placed by allanite which we have found in the Western Car-

pathian granites and metagranites. The first replacement of

monazite by allanite was reported from pegmatite in North

Carolina (Murata et al. 1957) and some remarks on this al-

teration phenomenon in the alkalic complex of the Vish-

nevyje gory can be found in Yeskova & Ganzyeva (1964).

The origin of deuteric allanite and sphene during chloritiza-

tion of biotite in the Dartmoor Granite was described by

Ward et al. (1992). Secondary allanite as a product of chlori-

tization was also reported from the Bohus Granite in SW

Sweden (Eliasson & Petersson 1996). The recent work of

Finger et al. (1998) brings a modern and comprehensive de-

scription of monazite breakdown in localities from the Austri-

an part of the Alps and from the Southern Bohemian Massif.

Total monazite breakdown in West-Carpathian metagran-

ites from the Veporic Superunit is described in this contribu-

tion. We also report a low-degree monazite alteration during

postmagmatic subsolidus activity of the fluids in non or (an-

chi)-metamorphic Tatric granites.

Geological setting

Migmatites with signs of a high degree of monazite break-

down belong to the Veporic basement which consists of three

basic lithotectonic units (Bezák 1994). The lower unit occurs

mainly in the southern part of the Veporic basement, the mid-

dle unit is thrust over the lower unit, the upper unit is present

162 BROSKA and SIMAN

in separate tectonic remnants beyond the studied area. The

lower unit consists of Lower Paleozoic metamorphites of the

greenschist facies (mica schists, albitic gneisses, chlorite-

muscovite schists). The middle unit comprises a broader

scale of metamorphites starting from the upper part of the

greenschist facies up to the upper part of the amphibolite fa-

cies. The age of the above mentioned metamorphites is uncer-

tain, but probably Proterozoic to Early Paleozoic. The studied

migmatites come from the locality Lipové village in the mid-

dle unit (loc. 4 in Fig. 1). According to Siman et al. (1996a)

the P-T conditions for the earliest metamorphism of the host

rocks with migmatite structure and with the tonalite composi-

tion (Fig. 2) were 680730

C at 400600 MPa and around

550600

C for a retrograde branch. The degree of Alpine

overprint is a matter of discussion, but the minimum tem-

perature estimate is T 480510

C and around 7 kbars (Si-

man et al. l.c.).

By contrast, only low degrees of monazite breakdown

were observed in the granites of the Tatric Superunit (Fig.

1). The Tatric granites which form the cores of the crystal-

line basement in the central Western Carpathians belong to

the two main Carboniferous granite groups: S-type granites

are the most widespread granite type, while I-type granites

(Petrík et al. 1994), which include mainly granitoids known

as the Sihla type sensu lato are less frequent (Broska &

Petrík 1993). No metamorphism, or only anchimetamor-

phism is known in these granites, but strong subsolidus

overprint of the primary mineral assemblage is their typical

phenomenon. Monazite alteration was found in the Tribeè

Granite (I-type), Malá Fatra Mts. and Malá Magura Granite

(both S-type). Biotite granite in the Tribeè Mts. occurs in

the form of veins 10.1 m in size which cut the undifferenti-

ated biotite tonalite host rocks near the Kozliov elevation

point. The occurrences in the Malá Fatra Mts. come from

the Bystrièka quarry (leucocratic granodiorite), in the Malá

Magura two mica granite showing monazite breakdown was

found in the Chvojnica Valley (Fig. 1).

Petrography and mineral composition

Migmatite from the Veporic Superunit

The host migmatites with a high degree of monazite

breakdown consist of well developed paleosom and neosom

up to 5 mm thick (Fig. 2). They are peraluminious meta-

greywacks (lacking Al

phases and containing quartz,

plagioclase, biotite, phengite, ±K-feldspar, chlorite). Synge-

netic ductile deformation associated with partial melting in

the whole hybrid complex was observed. Plagioclase forms

partly retrogressed to granoblastic aggregates of more or

less sodic grains filled with sericite±zoisite. In the most de-

formed places plagioclase is replaced by albite and/or seric-

ite felt. The maximum anorthite content is in the range of

to An

. Quartz represents mylonitic crushed grains or

it is recrystallized into granoblastic aggregates. K-feldspar

is found as cataclastic and from place to place shows per-

thitic texture. White mica has a phengitic composition, bi-

otite has Mg/(Mg+Fe) from 0.33 to 0.57, Al

varies from

0.6 to 1, TiO

is up to 3 wt. % (Siman et al. 1996a). Two

types of garnet occur in the migmatites. The older garnet has

almandine-pyrope compositions, the younger garnet forming

rims around older garnets (sometimes isolated grains) with

3340 % grossularite molecule (Siman et al. 1996a).

Granites from the Tatric

5KFAH

unit

The strong sericitization of plagioclases, chloritization

and epidotization of the biotites are characteristic alterations

of the main mineral assemblages in these Tatric granites.

The basicity of the plagioclase is mainly An

30-20

, the biotite

in the Tribeè locality is relatively Mg-rich, with Fe/(Fe+Mg)

ranging from 0.40.5, on the other hand in the S-type gran-

ites from the Malá Magura and Malá Fatra Mts. there are

Fe-rich biotites with Fe/(Fe+Mg) above 0.6 and more Ti-

rich in comparison with the I-type in the Tribeè Mts. (Petrík

& Broska 1994; Broska et al. 1997). The Malá Fatra granite

almost lost its biotite due to its strong alteration to chlorite

and white mica and only part of the monazite grains inside

of biotite or former biotite are attacked by fluids and

Fig. 1. Geological outlines of the crystalline basement of the West-

ern Carpathians with the localities of the monazite breakdown ob-

servation. The light shaded area represents the granite bodies of

the Tatric units. The darker shade filling represents the areal distri-

bution of the hybrid complex in the Veporic Superunit, which is a

structure of host migmatites and orthogneisses with a high degree

of monazite breakdown (locality Lipové for example), arrows ap-

prox. indicate the position of the studied localities: 1 Tribeè

Mts., Velèice village, 750 m W from the elevation point Kozliov.

Outcrop on the slope. 2 Malá Fatra Mts. Kra¾ovany, Bystrièka

quarry. 3 Stráovské vrchy Mts., Suchý, Chvojnica Valley. 4

Slovak Ore Mts. Kokava/Rimavica, 2 km from Kokava direction to

oltýska, outcrop on the road near the village of Lipové.

Fig. 2. Example of migmatite structure from the Lipové locality

(hybrid complex, Veporic Superunit). Scale bar is 1 cm.

THE BREAKDOWN OF MONAZITE IN THE WEST- CARPATHIAN VEPORIC ORTHOGNEISSES 163

changed to allanite. The chemical compositions of the gran-

ites with altered monazites as well as migmatite from the

Veporic Superunit are presented in Table 1.

Monazite breakdown

Monazite, a common accessory phase in the migmatite

and metagranites from the Veporic Superunit is transformed

into apatite and allanite-epidote in the way which was first

observed and described in the Granatspitze Granite Tauern

Window, Penninic Unit, Eastern Alps (Finger et al. 1998)

(Fig. 3A). The size of grains is around 10

m but in some

cases monazite reaches up to 200

m. The monazite grains

are surrounded by tiny grains of apatite which always con-

tinues outwards as allaniteepidote, with irregular shapes

which often penetrate into the biotite grains (Fig. 3A). Cas-

es where only unhomogeneous apatite is surrounded by al-

lanite-epidote rim are also present, and in this case no mon-

azite remnants in the cores of the apatiteallaniteepidote

mineral complex have been observed. Such phenomena rep-

resent the last stage of the monazite transformation when

the monazite is completely replaced by newly-formed apa-

tite and allanite minerals (Fig. 3B). The rim forming allanite

consists of two principal phases the inner part which is

richer in REE elements, the outer part which has epidote

composition (Fig. 3A, Table 2). The inner part of allanite-

epidote phase respects the monazite morphology, the outer-

most epidote phase has low integrity, and often fills cracks

and spaces within sheets in the biotite.

During replacement the phosphorus anion from monazite is

fixed in apatite, REEs enter the allanite and epidote. The el-

ements nourishing the growing allanite, such as silica, iron

and aluminium as well as OH groups come from annite, and

calcium mainly from anorthite components. It is possible to

express the breakdown of monazite in the form of a hypothet-

ical reaction where hydrogen comes from dissociated water:

monazite + annite + anorthite + quartz + fluids = apatite +

allanite + muscovite (or K-feldspar)

or in chemical form:

3LaPO

+ KFe

(Si

AlO

)(OH,F)

+ 4CaAl

+ 3SiO

+ 4Ca

+ 2H

→

(PO

)

(OH,F) + 3CaLaFe

(OH,F) + KAl(Si

AlO

)(OH)

We suggest that the reaction was activated by the origin

of phosphoric acid on the monazite rim. The apatite, which

originated firstly on the monazite rim could later be the

transport medium for exsolvus of the REE from the mona-

zite outward into the allaniteepidote, is inhomogeneous

and free of the REE. Probably it was in gel form and per-

haps the recent mosaic or grained polycrystalic structure of

apatite (Fig. 3a,b) indicate this stage. In this sense the apa-

tite is the memory of the role of the phosphoric acid in the

monazite breakdown processes.

The monazite breakdown recorded in the Alps and the

Southern Bohemian Batholith is known only from the granite

lithologies which were overprinted by Alpine metamorphism

under amphibolite facies. On the other hand metapelite lithol-

ogy brings an opposite effect, when during these metamor-

phic conditions new monazite is formed Finger et al. (l.c.).

The breakdown of the monazite in the Tatric granites is

not so widespread, and the processes produce only small

fringes of allanite without an intercalated apatite zone.

However, the apatite zone is most probably also present in

the monazite-allanite grains, and is not detectable in the

studied samples only as a result of its small size. The pro-

cess of monazite breakdown is found in the S-type, granite

but also in the I-type, especially in the more evolved or dif-

ferentiated varieties of the Tatric Superunit.

Discussion

Because the subsolidus fluids were able to transform

monazite to allanite only in the restricted form (Ward et al.

1992; Eliasson & Petersson 1996), the high degree of mona-

zite breakdown from Lipové (Veporic Superunit) could be a

result of metamorphic processes. In the case of the primary

monazite from the non-metamorphic Tatric granites, where

only initial breakdown of monazite was observed, the mon-

azite breakdown should coincide with chloritization during

subsolidus pervasive alteration of these granites. On the

other hand, the high degree of monazite breakdown in the

Lipové migmatite suggests the overprint of monazite during

Magura

Tribeè Malá Fatra

Veporic

Superunit*

BGM-1

T-37

BMF-1

VM-4/90

SiO

66.58

72.60

68.26

64.34

TiO

0.67

0.15

0.34

0.91

16.32

13.61

16.71

15.91

0.83

1.33

2.49

2.84

FeO

2.83

0.64

n.d.

4.86

MnO

0.01

0.03

0.04

0.12

MgO

1.54

0.59

0.71

2.36

CaO

3.51

1.59

2.81

2.38

3.85

3.32

5.09

2.97

2.04

4.68

1.89

3.37

0.42

0.21

0.06

0.08

0.9

0.14

1.30

n.d.

0.44

1.16

n.d.

Total

99.94

100.05

99.70 100.14

n.d.

116

820

1020

n.d.

953

n.d.

13.5

5.4

n.d.

207

120

154

314

6.8

7.1

n.d.

12.6

17.8

2.3

n.d.

496

229

n.d.

251

*mezosom

Table 1: Chemical analyses of the host rocks of altered monazites.

Sample BGM-1 and BMF-1 represent granodiorites, sample T-37

is biotite monzogranite. VM-4/90 represents a typical migmatite to

orthogneiss of the hybrid complex of the Veporic basement.

164 BROSKA and SIMAN

metamorphosis, and it should be similar to the process

known from the Alpine terrain in the Tauern Window

(Granatspitz granite gneiss), Austro-Alpine Unit (Raabal-

pen Massif, Winnebach migmatite gneiss, Sulztal granite

gneiss, Zinken granite gneiss) and the Moravian Unit in the

Eastern Bohemian Massif (Witersfeld gneiss, Bitesch

gneiss) (Finger et al. 1998). The observed breakdown of

monazite in all the mentioned cases occurred in the am-

phibolite facies (500600

C and 47 kbar) (Finger et al.

1998 and references therein).

The monazite zoning (Fig. 3A, Table 2), indicating its

magmatic origin (Lipové locality) in the formerly felsic

magmatite of Devonian age, is also preserved during mona-

zite breakdown in the monazite cores. Felsic magmatites

from the early Variscan stage (Devonian age) are known,

apart from the Veporic hybrid complex, also in the Western

and Low Tatras, Ve¾ká Fatra (Petrík & Kohút in press). Af-

ter the emplacement of the Devonian felsic magma, intru-

sions of the layered magmas into shear zones are known

from this area, as a process accompaning the main Variscan

metamorphic event, which reaches amphibolite facies in

this area and with the formation of orthogneisses and mig-

matites. The breakdown of monazite in the Lipové meta-

granites, in this sense, started as a result of this prograde

metamorphism of the amphibolite stage and deformation

during thrusting together with the Hercynian thickening and

the following relaxation (Siman et al. 1996a,b), which is

dated by the main Variscan granite intrusions of the S-type

granites (Cambel et al. 1990) ca. 350330 Ma.

The P-T conditions during the Alpine metamorphism

which contributed to the breakdown of the monazite in the

Veporic Superunit, especially in its southern part, are being

widely discussed at present. In this region the Alpine meta-

morphic assemblages as well as the mineral zoning indicate

Table 2: Representative microprobe analyses of the grain 1 and 2 in the migmatite from Veporic Superunit. The points of analyses are in

the BSE images (see Fig. 3). The measure conditions: 20kV, 20 nA, 3 M beam diameter, using ZAF corection and natural and synthetic

standards. Jeol Superprobe 733.

Grain

Sample

VM-2

Mineral

mnz

aln

REE-ep

aln

REE-ep

Position

SiO

0.39

0.45

0.33

1.83

32.00

31.06

40.26

0.21

32.54

36.15

36.04

30.47

30.43

30.84

39.33

0.00

41.68

0.00

CaO

1.00

0.72

0.88

52.15

11.79

11.69

19.71

54.23

12.54

20.88

21.75

11.38

11.15

13.32

0.00

3.99

3.53

0.00

7.21

5.41

3.93

26.23

27.18

28.17

0.00

8.98

8.57

0.00

6.45

0.22

0.00

3.68

3.92

3.74

0.00

1.49

1.47

0.08

0.00

10.63

11.82

10.83

0.00

4.79

4.53

0.34

0.00

3.19

0.61

0.42

2.92

3.57

2.87

0.00

0.88

0.98

0.11

0.00

0.35

0.15

0.14

2.76

3.17

2.22

0.00

0.27

0.23

0.00

4.65

3.68

3.02

0.00

0.65

0.30

0.31

0.00

0.14

0.00

ThO

3.97

3.56

3.57

0.00

0.22

0.83

0.00

1.92

0.00

1.30

0.19

0.42

0.00

1.04

16.33

18.01

21.78

0.02

22.42

27.24

26.95

FeO

0.00

0.66

12.57

11.64

6.51

0.00

10.00

6.49

7.13

MnO

0.00

0.16

0.18

0.09

0.00

MgO

0.00

0.23

0.30

0.51

0.00

0.37

0.07

0.06

TiO

0.00

0.24

0.26

0.06

0.00

0.20

0.15

PbO

0.77

0.13

0.12

0.00

Total

100.42

100.24

100.56

95.01

94.32

93.35

89.76

96.14

97.33

97.37

96.57

0.015

0.017

0.013

0.321

3.114

3.028

3.423

0.036

2.952

2.971

2.968

0.992

0.999

5.843

0.000

6.125

0.000

0.041

0.030

0.036

9.804

1.229

1.221

1.795

10.086

1.219

1.838

1.919

0.161

0.158

0.188

0.000

0.143

0.127

0.000

0.241

0.164

0.119

0.369

0.383

0.395

0.000

0.320

0.306

0.000

0.214

0.007

0.000

0.052

0.055

0.052

0.000

0.053

0.052

0.002

0.000

0.146

0.163

0.148

0.000

0.166

0.158

0.010

0.000

0.103

0.018

0.012

Sm0.039

0.047

0.038

0.000

0.030

0.033

0.003

0.000

0.011

0.004

0.035

0.040

0.028

0.000

0.003

0.000

0.095

0.075

0.062

0.000

0.034

0.016

0.014

0.000

0.007

0.000

0.035

0.031

0.000

0.005

0.018

0.000

0.040

0.000

0.011

0.002

0.004

0.000

0.215

1.873

2.069

2.182

0.004

2.397

2.638

2.616

0.000

0.097

1.023

0.949

0.463

0.000

0.759

0.446

0.491

0.000

0.013

0.015

0.006

0.000

0.033

0.044

0.065

0.000

0.050

0.009

0.007

0.000

0.018

0.019

0.004

0.000

0.014

0.009

0.008

0.001

0.000

THE BREAKDOWN OF MONAZITE IN THE WEST- CARPATHIAN VEPORIC ORTHOGNEISSES 165

a progressive trend of metamorphism (Méres & Hovorka

1991; Kováèik et al. 1996). According to Kováèik et al.

(1996), the Alpine regional metamorphism occurred at tem-

peratures estimated between 350 and 500

C and under low

to medium pressure conditions (300 MPa) i.e. in greenschist

metamorphic conditions. According to these authors, the

Alpine regional metamorphism is characterized by infiltra-

tion metamorphism and relatively high fluid pressure,

which could have contributed to the reduction of lithostatic

pressure. The model implying convective fluid flows, oper-

ating due to higher heat flow as well as differences in per-

meability of the rocks, seems to fit the geodynamic interpre-

tation of the Alpine metamorphism of the southern Veporic

Superunit (Kováèik et al. 1996). On the other hand the latest

geothermobarometric calculations give higher P-T condi-

tions during peaks of metamorphism: 550600

C and 800

1000 MPa (Janák et al. 1997; Plaienka et al. 1997), which

represents the amphibolite facies (epidoteamphibolite sub-

facies). According to Plaienka et al. (1997), the Alpine

metamorphism in the southern Veporic Superunit was

caused by burial of the Veporic basement as well as its Per-

momesozoic cover during the Cretaceous collisional events.

The possibility of the temperature exceeding 500

C in

some parts of the southern Veporic Superunit is also indicat-

ed by Krá¾ et al. (1996). The Alpine metamorphism in this

sense triggered the intensive breakdown of the monazite

(Fig. 3) as in the case of the Alpine terraine because the am-

phibolite facies was reached, which seems to be a neccessa-

ry condition for extensive development of this process (Fin-

ger et al. 1998). Although the high degree of monazite

breakdown reflects both the Late-Variscan and Alpine meta-

morphic events in a hybrid complex (the Lipové locality),

the contribution of Alpine metamorphism was more signifi-

cant which is the reason for monazite instability with areal

distribution in the southern Veporic Superunit. The mona-

zite breakdown is observable not only in the hybrid com-

plex (Fig. 1) but this phenomenon is also known in the adja-

cent area. Recently Hrako et al. (1997) described apatite

with allanite rim in Klenovec granites and also in the Rima-

vica Granite (oral communication).

The age of the Alpine metamorphism which caused the

monazite breakdown was determined as around 110 Ma by the

Ar/

Ar method on amphiboles. Then, after the metamorphic

peak conditions, the Veporic Superunit was uplifted and younger

Ar/Ar ages of around 88 Ma are connected with the emplace-

ment of higher superficial nappes (Kováèik et al. 1996).

REE mobility: The monazite breakdown indicates a mo-

bility of the rare earth elements, but it seems that it was in

restricted form and the mobilization of REEs was on a local

scale only. It could be stated that the monazite grains pre-

served features of their primary magmatic zonality with in-

creasing LREE (La, Ce) towards the rim of the grains and

decreasing yttrium (Table 2), while the REE whole rock pat-

terns of the studied samples in the Tatric granites show no

significant anomalies (Broska et al. 1997). The diffusion of

the REE was continual which is evident from the REE pat-

tern of the monazite and its breakdown products, newly

formed allanite (Fig. 4). The rapid decrease of REE in al-

lanite to REE-epidote in the small distance to the outermost

rim of brokendown monazite also suggests that only limited

mobility of REE occurred.

Fig. 3. The BSE images of the analyzed grains from the magmatite (Hybrid complex, locality Lienica). The number of analyses are the

curent position of the analyses from Table 2. AGrain 1 consists of a monazite core (Mnz), apatite transition zone (Ap) and rim of allan-

ite-REE epidote (Aln). BGrain 2 has an apatite core and allanite-REE epidote rim. The analyses of grains A and B are given in Table 1.

Fig. 4. REE pattern of the monazite core and the newly-formed al-

lanite in the metagranite of the Veporic Superunit.

166 BROSKA and SIMAN

Conclusion

The replacement of primary magmatic monazite by meta-

morphic allanite and apatite was observed in the Lipové

migmatite and other metagranites from the Veporic Supe-

runit (Western Carpathians). The Alpine metamorphic event

caused the widespread breakdown of primary monazite in

the Veporic Superunit, although we presume that the mona-

zite transformation started already during the late-Variscan

orogenesis. The replacement is accompanied by formation

of a transition zone between these mineral phases which

consist of apatite. Apatite was formed from phosphoric acid

and it acted as a transport medium for the rare earth ele-

ments outward from monazite. Sometimes total breakdown

of monazite occurred. In this case monazite completely dis-

appeared and only apatite remains in the core of grains over-

grown by allanite and REE epidote. The monazite reaction

with biotite and anorthite which produced the allanite may

have been triggered by fluids with higher activity of phos-

phorus. The P-T conditions of this replacement were esti-

mated for amphibolite facies.

A much lower degree of monazite breakdown was ob-

served in the Tatric granites. In this case we concluded that

the monazite alteration coincided with pervasive alteration

of granites in the subsolidus stage.

Acknowledgement: This research was supported by Project

No. 150 of Lise-Meitner stipendium (Austria) and (Ga 4078

VEGA Slovak Acad. Sci.). The authors are thankful for crit-

ical comments and discussion with Prof. Dr. F. Finger from

Salzburg University, and also wish to thank Dr. Igor Petrík

from the Geological Institute of the Slovak Academy of Sci-

ances who helped improve the final version of the paper.

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