METAMORPHISM OF THE SEDIMENTARY ROCKS FROM THE WESTERN CARPATHIANS 367
GEOLOGICA CARPATHICA, 54, 6, BRATISLAVA, DECEMBER 2003
367375
ALPINE LOW-GRADE METAMORPHISM OF THE PERMIAN-TRIASSIC
SEDIMENTARY ROCKS FROM THE VEPORIC SUPERUNIT,
WESTERN CARPATHIANS: PHYLLOSILICATE COMPOSITION
AND CRYSTALLINITY DATA
BRANISLAV LUPTÁK
1
, MARIAN JANÁK
1
, DUAN PLAIENKA
1*
and SUSANNE TH. SCHMIDT
2
1
Geological Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05 Bratislava 45, Slovak Republic; branislav.luptak@savba.sk;
geolmjan@savba.sk
2
Département de Minéralogie, Rue des Maraîchers 13, 1211 Genève 4, Switzerland
*Present address: Department of Geology and Paleontology, Faculty of Natural Sciences, Comenius University Mlynská dolina,
842 15 Bratislava, Slovak Republic; plasienka@fns.uniba.sk
(Manuscript received December 10, 2002; accepted in revised form June 23, 2003)
Abstract: Alpine low-grade metamorphism related to Cretaceous orogeny has been investigated in the metasediments of
the Permian-Triassic cover in the Veporic Superunit, Western Carpathians. Metaclastic rocks and marbles show meta-
morphic grade of upper anchizonal to epizonal (greenschist facies) conditions according to the illite crystallinity mea-
surements. The chlorite thermometry of Cathelineau (1988) and Jowett (1991) yields a temperature of ca. 310330 °C in
the northern part and ca. 335380 °C in the central and eastern parts of the Veporic Superunit. A pressure of ca. 44.5 kbar
has been obtained from the white mica, K-feldspar and biotite-bearing rocks, supposing a temperature of ca. 380 °C. The
new results suggest higher temperature and lower pressure of the Alpine low-grade metamorphism than the previous
estimates. The P-T conditions of the Alpine low-grade metamorphism in the Veporic Superunit are in good agreement
with the observed deformational microtextures.
Key words: Alpine metamorphism, Western Carpathians, Veporic Superunit, Permian-Triassic cover, geothermobarometry,
crystallinity index.
Introduction
Vrána (1966) presented the first important petrographical and
mineralogical data on Alpine low-grade metamorphism in the
Veporic Superunit of the Western Carpathians. Plaienka et
al. (1989) first reported the conditions of low-grade metamor-
phism in Mesozoic metapelitic rocks of parautochthonous
cover sequences of the Veporic Superunit based on the illite
crystallinity. Their results prove epizonal metamorphic con-
ditions accompanied by ductile overthrust deformations in the
southern Veporic cover unit and decreasing metamorphic
grade from epizonal to anchizonal conditions in the northern
Veporic cover unit. No mineral chemical data have been pub-
lished by the authors mentioned above. Later on, Korikovsky
et al. (1992, 1997) discussed the conditions of Alpine an-
chimetamorphism in the Veporic Superunit.
This study presents results on Alpine metamorphism in the
Veporic Superunit complementary to those reported recently
by Lupták et al. (2000) and Janák et al. (2001).
The purpose of the present study is: (1) to determine the
mineral parageneses and composition of individual minerals
in the low-grade metasediments from the Permian-Triassic
cover of the Veporic Superunit, (2) to evaluate the P-T condi-
tions of Alpine metamorphism, and (3) to correlate these re-
sults with illite and chlorite crystallinity.
Geological setting
The pre-Tertiary complexes of the Central Western Car-
pathians (Plaienka et al. 1997) are composed of six main Slo-
vakocarpathian north-verging superunits: the Tatric, Veporic
and Gemeric thick-skinned basement/cover nappe stacks and
the Fatric, Hronic and Silicic detachment cover nappe systems
(e.g. Biely 1989; Tomek 1993; Plaienka et al. 1997). All
these units originated during the Cretaceous collisional short-
ening and stacking of the lower plate following the closure of
the Meliatic Ocean during the Late Jurassic and they may be
well correlated with the Austroalpine units of the Alps (Janák
et al. 2001).
The Veporic Superunit (Fig. 1) is the middle of the three
major, south-dipping, thick-skinned basement/cover imbri-
cates. As a consequence of collisional thickening in the Creta-
ceous, the Veporic basement and its Permian-Triassic cover
experienced regional Alpine metamorphism. The dominant
Veporic macrostructure, a low-angle normal ductile shear
zone, is interpreted as a master detachment fault, which ex-
humed the Veporic core by east-vergent unroofing (Plaienka
et al. 1999).
The Veporic cover complexes are in marginal position on
the crystalline basement or are only locally preserved in the
central part. The Late Paleozoic-Mesozoic sedimentary cover
368 LUPTÁK, JANÁK, PLAIENKA and SCHMIDT
of the Veporic Superunit is subdivided into two parts (a)
the south-eastern and central Foederata Unit and (b) the
northern Ve¾ký Bok Unit.
The Foederata Unit is scarcely preserved. It consists of low-
to medium-grade metamorphosed and highly foliated and de-
formed rocks of sedimentary origin (Plaienka et al. 1997).
This unit includes Upper Permian continental clastics
(metasandstones and metaconglomerates), Scythian quartzites
and schists overlain by Middle to Late Triassic rocks, mostly
carbonates of a passive margin environment. No Jurassic sed-
imentary rocks have been observed.
The Ve¾ký Bok Unit comprises Permian red beds (¼ubie-
tová Group, Vozárová & Vozár 1988), Scythian quartzites,
Middle Triassic carbonate platform deposits, and Upper Tri-
assic, continental Carpathian Keuper Formation. The Rha-
etian and Lower Liassic littoral sedimentary rocks are super-
imposed by continuously deepening Upper LiassicLower
Cretaceous deposits with typical spotted marls, nodular, cher-
ty and siliceous limestones, radiolarites and thick Neocomian
dark marly limestones, which represent the syn- and post-rift
sequences (Plaienka et al. 1997).
The deformational structural association of the area covered
by the Foederata Unit is dominated by a flat or moderately
NE-dipping metamorphic/mylonitic foliation S
1
, which is
penetrative in both the topmost parts of the basement grani-
toids and in the Veporic cover units. The foliation planes show
a distinct stretching lineation L
1
plunging generally to the east.
This deformation stage AD
1
is completed by the moderately E-
to NE-dipping shear bands, which are mesoscopically penetra-
tive along the eastern margin of the Veporic dome (e.g. exten-
sional crenulation cleavage ECC, or C-type shear bands).
Tight to isoclinal folds F
1
are frequent only in the Triassic
marbles of the Foederata Unit, where they usually exhibit NW-
verging asymmetry and axes parallel to the elongation direc-
tion. The growth of newly formed metamorphic minerals with-
in the cover rocks is generally syn- to early post-kinematic
Fig. 1. Geological sketch map of the studied area with locations of investigated samples.
Fig. 2. Microphotographs of mineral assemblages and deformational
textures in the studied rocks. a Back-scattered electron (BSE) im-
age of the metamorphosed marly limestone (LUC7). b Microphoto-
graph of metamorphosed marly limestone with chlorite rich layer
(LUC7). c BSE image of authigenic white micas and subhedral K-
feldspars in marble (DOPO4). d BSE image of biotite and phengitic
white mica in Scythian schist (ZE4). e Microphotograph of crenula-
tion cleavage in the Carpathian Keuper slate (VAL1). f Micropho-
tograph of crenulation cleavage in the Scythian schist (DOPO2). g
Microphotograph of recrystallized quartz and white mica layers in
Scythian schist (MB3). h Microphotograph of chlorite porphyro-
blast in Scythian schist (ZE1). Wm white mica, Phn phengite.
▲
METAMORPHISM OF THE SEDIMENTARY ROCKS FROM THE WESTERN CARPATHIANS 369
Fig. 2.
370 LUPTÁK, JANÁK, PLAIENKA and SCHMIDT
with respect to the foliation S
1
, and pre- to syn-kinematic with
respect to the ECC planes.
The Ve¾ký Bok Unit exhibits imbricated fold-and-thrust
structures developed during several deformation stages
(Plaienka 1995). Thrust stacking occurred in front of the Ve-
poric crustal wedge and in the rear of the detached Mesozoic
sedimentary complexes which later became the Fatric Krína
cover nappe system (e.g. Plaienka et al. 1997).
Petrography and deformational microtextures
The samples were collected from the central and marginal
parts of the Veporic Superunit (Fig. 1). Representative litho-
logical types (Fig. 2), namely Scythian metaquartzites, schists
and Middle to Late Triassic marbles were investigated. Lithol-
ogy, stratigraphic position and mineral assemblages of the
collected samples are listed in Table 1.
Metaquartzites and related schists contain mainly white
mica and quartz. K-feldspar and albite are present in various
amounts and chlorite can be found only sporadically in a few
samples. Tourmaline is the main accessory mineral.
Marbles are composed mainly of recrystallized calcite. Do-
lomite, albite, K-feldspar, quartz, white mica and chlorite are
also present.
Metaquartzites are entirely recrystallized, showing strong
preferred orientation of mica foliae. The detrital quartz grains
are flattened and stretched with undulose extinction in the
most deformed rocks. Grain size of recrystallized quartz in the
mica-poor layers is larger than in the mica-rich layers, because
in the latter, the grain growth was limited by mica grains pin-
ning at the quartz grain boundaries. Some quartz porphyro-
clasts show shape-preferred orientation due to dissolution
along boundaries parallel to foliation. The extent of the pres-
sure solution has been enhanced in some cases by the pres-
ence of deformation resistant magnetite grains. Both the face
and displacement controlled pyrite-type quartz fibres formed
in the pressure shadows.
Marbles exhibit various grain size and microstructures. Fo-
liation planes are defined by elongated coarse-grained relict
Sample
Lithology
Stratigraphic position, unit white mica Chl Qtz Dol Cal Ab Kfs Kln Tur Bt Ilm Rt Mag Hem KI ChC
DOPO1
metaquartzite
Scythian, Foederata
x
o
x
x
x
o
x
x
x
0.22 0.25
DOPO2
schist
Scythian, Foederata
x
o
x
x
x
x
x
x
x
-
-
DOPO4
marble
Triassic, Foederata
x
o
x
x
x
x
o
0.25
-
DOPO13
marble
Triassic, Foederata
x
x
x
x
x
0.23
-
MB3
schist
Scythian, Foederata
x
x
x
o
x
0.19
-
RR1
metaquartzite
Scythian, Foederata
x
x
o
x
x
0.26
-
TEL1
schist
Scythian, Foederata
x
x
x
x
x
x
0.17 0.15
TEL3
metaquartzite
Scythian, Foederata
x
o
x
x
x
x
0.25 0.25
TRE2
schist
Scythian, Foederata
x
o
x
o
x
x
0.26
-
ZB1
schist
Scythian, Foederata
x
x
x
x
0.21
-
ZB2
schist
Scythian, Foederata
x
x
x
x
o
x
0.23
-
ZE1
schist
Scythian, Foederata
x
x
x
x
x
o
x
x
x
0.14
-
ZE4
schist
Scythian, Foederata
x
x
x
x
x
x
x
0.26
-
LU6
schist
Carpathian. Keuper Fm., VB
o
o
o
x 0.29 0.22
LUC7
marly limestone Tithonian Neocomian, VB
o
x
x
x
x
x
0.30 0.22
VAL1
schist
Carpathian. Keuper Fm., VB
x
x
x
x
x 0.27 0.22
VB Ve¾ký Bok; KI Kübler index, air-dried °,2G CuK=; ChC Chlorite crystallinity (002) AD °,2G CuK=; AD air dried; x major phase recognized by
microscopy; o minor phase detected by X-ray.
Table 1: Lithology, stratigraphy and mineral assemblages of the studied samples. Mineral abbreviations after Kretz (1983).
calcite porphyroclasts and dynamically recrystallized fine-
grained calcite matrix, both showing shape preferred orienta-
tion. For the first set of grains clockwise and anticlockwise
twins are dominant. They become subparallel to the foliation
with increasing strain intensity. Dolomite porphyroclasts be-
have as rigid bodies and are concentrated with other insoluble
material on the zig-zag stylolitic boundaries. The authigenic
white mica and chlorite concentrate in thin layers together
with quartz, but they are also widespread as single flakes in
the marble oriented subparallel to the main foliation plane
(Lupták et al. 2001).
Analytical methods
15 white K-mica-bearing samples of various lithologies and
stratigraphic locations (Table 1) were prepared for X-ray pow-
der diffraction following the procedures recommended by
Kisch (1991). They were initially hammer-crushed followed
by further, gentle disaggregation using a Sieb Mill for less
than 30 s. Carbonate was removed by treatment with 5% ace-
tic acid. Slides of oriented <2
µ
m fractions were prepared by a
pipette method following the sedimentation of disaggregated
samples in distilled water (Brindley & Brown 1984), keeping
the specimen thickness of 5 mg/cm
2
. Measurements were
made using a Siemens D-5000 diffractometer (University
Basel) at 40 kV, 30 mA and CuK
α
radiation. Air-dried sam-
ple mounts were scanned in the range of 2°21° 2
θ
with a
scanning rate of 0.03°2
θ
/20 s. Illite and chlorite crystallini-
ty data (Kübler 1967, 1968; Frey 1987; Árkai 1991; Árkai et
al. 1995; Warr 1996), i.e. the half-height width values of the
first basal reflection of muscovite (Kübler index KI) and
the second basal reflection of chlorite (ChC) were calculated
using the Siemens profile fitting package DIFFRACPlus: Pro-
file plus v. 1.06. The KI values for the diagenetic zone/an-
chizone and the anchizone/epizone boundary are 0.42° a nd
0.25°
∆
2
θ
CuK
α
, respectively (see Frey 1988; Dalla Torre &
Frey 1997).
The chemical composition of selected minerals was ob-
tained from polished thin sections by wavelength-dispersive
METAMORPHISM OF THE SEDIMENTARY ROCKS FROM THE WESTERN CARPATHIANS 371
spectroscopy method using a Jeol JXA-8600 electron-micro-
probe at the Institute of Mineralogy and Petrology, University
of Basel. The operating conditions were set at an acceleration
voltage of 15 kV and a 10 nA beam current. Natural and syn-
thetic standards were used and the data were reduced by the
PROZA routine.
Results
Electron microprobe data
Due to the fine grain size of samples studied by the X-ray
diffraction method, microprobe data were obtained only on 11
samples. The compositions of authigenic white mica, chlorite,
feldspar and biotite are presented below:
White mica
Representative analyses of white mica are shown in Ta-
ble 2. Si ranging from 6.33 to 6.53 a.p.f.u. and Fe/(Fe+Mg)
ratio of 0.460.74 are characteristic for the K-white micas in
metaclastics. The K-white mica of the marble is characterized
by 6.71 Si a.p.f.u. and Fe/(Fe+Mg) lower than 0.01. All K-
white mica analyses from the investigated samples plot paral-
lel to, but below the Tschermak exchange vector (Fig. 3). This
indicates the presence of some ferrimuscovite component
(Hunziker et al. 1986). The Na content is constantly low, the
K content is more variable and the interlayer occupancy clus-
ters around the theoretical mica value of 2.0 (Fig. 3). The sum
of octahedral and interlayer cations shows a higher value than
the theoretical one in some cases. This can be explained by
the presence of noticeable Fe
3+
amount.
Sample
DOPO1 DOPO1 DOPO2 DOPO2 DOPO4 DOPO4
MB3
MB3
ZB1
ZB1
ZB2
ZE4
DOPO2
ZE4
analysis #
Phn2
Phn3
Phn1
Phn3
Phn2
Phn3
Phn2
Phn3
Phn2
Phn6
Phn2
Phn3
Bt5
Bt4
SiO
2
47.58
47.89
47.21
47.23
50.35
50.88
47.94
47.76
45.67
44.99
46.39
45.74
36.32
36.47
Al
2
O
3
28.31
28.44
27.03
27.91
29.28
28.56
28.10
27.59
28.40
27.53
27.89
27.66
15.90
17.48
TiO
2
0.88
0.80
1.14
1.26
0.96
0.21
1.31
0.69
1.01
1.23
0.98
0.98
3.03
3.11
MgO
2.46
2.62
2.23
2.05
3.97
4.37
2.00
1.93
1.59
1.39
1.76
2.18
9.97
10.14
FeO
4.00
4.00
6.47
5.83
0.03
0.07
6.12
6.39
7.48
7.18
7.10
6.68
19.04
17.16
MnO
0.00
0.01
0.00
0.03
0.00
0.00
0.00
0.02
0.00
0.01
0.03
0.03
0.14
0.06
CaO
0.01
0.04
0.00
0.00
0.11
0.10
0.00
0.02
0.02
0.00
0.01
0.01
0.00
0.01
Na
2
O
0.14
0.20
0.16
0.16
0.15
0.13
0.08
0.12
0.11
0.07
0.03
0.14
0.05
0.05
K
2
O
11.52
11.62
11.31
11.39
11.79
11.68
11.52
11.46
11.00
11.26
10.68
11.37
10.15
9.18
Total
94.89
95.62
95.55
95.85
96.64
96.00
97.07
95.98
95.28
93.66
94.88
94.79
94.59
93.65
Si
6.50
6.50
6.49
6.45
6.61
6.71
6.47
6.53
6.33
6.35
6.42
6.36
5.60
5.57
Al
iv
1.50
1.50
1.51
1.55
1.39
1.29
1.53
1.48
1.68
1.65
1.58
1.64
2.40
2.43
Al
vi
3.06
3.05
2.87
2.94
3.14
3.15
2.94
2.97
2.96
2.93
2.97
2.90
0.49
0.72
Ti
0.09
0.08
0.12
0.13
0.10
0.02
0.13
0.07
0.11
0.13
0.10
0.10
0.35
0.36
Mg
0.50
0.53
0.46
0.42
0.78
0.86
0.40
0.39
0.33
0.29
0.36
0.45
2.29
2.31
Fe
2+
0.46
0.45
0.74
0.67
0.00
0.01
0.69
0.73
0.87
0.85
0.82
0.78
2.45
2.19
Mn
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.02
0.01
Ca
0.00
0.01
0.00
0.00
0.02
0.01
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Na
0.04
0.05
0.04
0.04
0.04
0.03
0.02
0.03
0.03
0.02
0.01
0.04
0.02
0.02
K
2.01
2.01
1.98
1.99
1.98
1.97
1.98
2.00
1.94
2.03
1.89
2.02
2.00
1.79
Fe/(Fe+Mg)
0.48
0.46
0.62
0.62
0.00
0.01
0.63
0.65
0.73
0.74
0.69
0.63
0.52
0.49
X(Ca)
0.000
0.003
0.000
0.000
0.007
0.007
0.000
0.001
0.002
0.000
0.001
0.000
0.000
0.001
X(Na)
0.018
0.026
0.021
0.021
0.019
0.016
0.010
0.016
0.015
0.009
0.004
0.018
0.007
0.008
X(K)
0.981
0.971
0.979
0.979
0.974
0.977
0.990
0.983
0.983
0.991
0.995
0.981
0.993
0.991
Table 2: Representative chemical analyses of authigenic white mica and biotite. Formulae calculated on the basis of 22 oxygens.
Fig. 3. Microprobe analyses of white K-micas plotted in Si-Al
tot
and
Na-K diagrams.
Chlorite
Mean analyses of authigenic-metamorphic chlorite are
shown in Table 3. The chemical data were screened through a
quality-control grid according to criteria proposed by Foster
(1962) and Zane et al. (1998). The number of tetrahedral alu-
minium atoms is 2.322.75. The Si content of the chlorites is
5.255.68 a.p.f.u. and the Fe/(Fe+Mg) ratio ranges from 0.19
to 0.55. Mn and Ti contents are negligible.
Biotite and feldspars
Representative analyses of biotite are shown in Table 2. Ti
contents up to 0.36 a.p.f.u. are characteristic for these biotites.
The feldspars are albite and K-feldspar (Table 4).
372 LUPTÁK, JANÁK, PLAIENKA and SCHMIDT
X-ray diffraction of the < 2
µµµµµ
m fraction
X-ray powder diffraction patterns of oriented <2
µ
m frac-
tion show that illite-muscovite and chlorite±quartz, albite and
K-feldspar are the main phases present. Sample TEL1 con-
tains a subordinate amount of paragonite. Calibrated KI and
ChC values have been used to determine relative changes in
Sample
LUC7
VAL1
TEL1
ZE1
analysis #
(n = 8)
(n = 5)
(n = 7)
(n = 9)
SiO
2
27.00
28.61
27.98
25.30
Al
2
O
3
22.06
22.72
22.53
22.71
TiO
2
0.07
0.12
0.03
0.06
MgO
12.05
25.12
24.91
16.99
FeO
25.94
10.42
10.45
22.06
MnO
0.27
0.04
0.45
0.21
CaO
0.02
0.00
0.00
0.01
Na
2
O
0.01
0.00
0.00
0.01
K
2
O
0.23
0.08
0.02
0.04
Total
87.64
87.10
86.39
87.39
Si
5.68
5.57
5.51
5.25
Al
iv
2.32
2.43
2.49
2.75
Al
vi
3.14
2.79
2.74
2.81
Ti
0.01
0.02
0.01
0.01
Mg
3.77
7.29
7.32
5.26
Fe
2+
4.56
1.70
1.72
3.83
Mn
0.05
0.01
0.08
0.04
Ca
0.01
0.00
0.00
0.00
Na
0.00
0.00
0.00
0.00
K
0.06
0.02
0.01
0.01
Fe/(Fe+Mg)
0.55
0.19
0.19
0.42
T(°C)
312±30
329±8
340±8
380±10
T(°C)*
319±30
325±8
335±8
382±10
T(°C) Cathelineau (1988); T(°C)* Jowett (1991)
Sample
DOPO2 DOPO4
MB3
ZB2
ZE4
LUC7
analysis #
Kfs1
Kfs4
Kfs10
Kfs1
Kfs1
Ab7
SiO
2
64.67
63.60
63.04
62.79
62.46
67.57
Al
2
O
3
18.14
18.38
19.04
19.29
18.77
21.18
TiO
2
0.03
0.00
0.00
0.00
0.00
0.00
MgO
0.01
0.01
0.00
0.00
0.01
0.41
FeO
0.00
0.00
0.03
0.15
0.13
0.38
MnO
0.08
0.00
0.00
0.00
0.00
0.03
CaO
0.00
0.16
0.00
0.02
0.00
0.21
Na
2
O
0.78
0.26
0.78
0.60
0.80
8.26
K
2
O
17.03
17.40
17.02
16.57
17.04
0.21
Total
100.74
99.82
99.91
99.42
99.21
98.25
Si
2.99
2.97
2.94
2.94
2.94
2.97
Al
0.99
1.01
1.05
1.06
1.04
1.10
Ti
0.00
0.00
0.00
0.00
0.00
0.00
Mg
0.00
0.00
0.00
0.00
0.00
0.03
Fe
2+
0.00
0.00
0.00
0.01
0.01
0.01
Mn
0.00
0.00
0.00
0.00
0.00
0.00
Ca
0.00
0.01
0.00
0.00
0.00
0.01
Na
0.07
0.02
0.07
0.05
0.07
0.70
K
1.00
1.04
1.01
0.99
1.02
0.01
An
0.000
0.007
0.000
0.001
0.000
0.014
Ab
0.065
0.022
0.065
0.052
0.067
0.970
Or
0.935
0.970
0.935
0.947
0.933
0.017
Table 4: Representative chemical analyses of authigenic feldspars.
Formulae calculated on the basis of 8 oxygens.
Table 3: Mean chemical analyses of authigenic chlorites. Formulae
calculated on the basis of 28 oxygens, assuming all Fe as Fe
2+
.
Fig. 4. Diffractograms of some illite-muscovite-rich clay fractions
showing the first two basal reflections. Samples are arranged with
increasing (downwards) metamorphic grade according to their illite
crystallinity values. Impurities include chlorite, quartz and
K-feldspar (TEL1).
Fig. 5. KI variation in the investigated metasediments from the
western to the eastern part of the Veporic Superunit.
metamorphic grade (see the part Analytical methods). The
calibrated values for the studied samples are presented in Ta-
ble 1. The KI data range from 0.14 to 0.30 °
∆
2
θ
and ChC
from 0.15 to 0.25 °
∆
2
θ
. Representative diffractograms from
various lithologies (Fig. 4) illustrate decreasing KI with in-
creasing metamorphic grade. Figure 5 shows the difference
and variation of KI from the western to the eastern part of the
Veporic Superunit.
The relationship between the chemistry and KI values of
micas has been discussed by Árkai et al. (2002). They found a
correlation between the KI and celadonite content of white K-
METAMORPHISM OF THE SEDIMENTARY ROCKS FROM THE WESTERN CARPATHIANS 373
mica. Increasing Si content (Fig. 6a) and decreasing Al
iv
/
(Al
iv
+Fe
2+
+Mg) ratio (Fig. 6b) of white K-mica with increas-
ing KI were also observed in samples from the Foederata
Unit.
Thermobarometry
To determine the temperature conditions, the chlorite ther-
mometer of Cathelineau (1988) based on Al
iv
substitution in
chlorites was used, together with its modified version by
Jowett (1991). Both thermometers gave only slightly different
results, showing an increase in temperature from ca. 310 to
380 °C (Table 3). Lower (~310330 °C) temperatures were
obtained from chlorites of the Ve¾ký Bok Unit compared to
those from the Foederata Unit (~335380 °C). Although the
chlorite thermometry is mostly inaccurate in sedimentary
rocks (e.g. Schmidt et al. 1997), since it was calibrated for
volcanic rocks (Cathelineau 1988), the increasing trend of
metamorphic temperatures in the studied units is obvious and
corresponds with the obtained phyllosilicate crystallinity
data.
In the easternmost part of the Foederata Unit, pressure was
estimated in the K-feldspar and biotite-bearing schists from
the reaction: 3Cel = Phl + 2Kfs + 3Qtz + 2H
2
O (Fig. 7), using
the computer program THERMOCALC v. 3.1 (Powell & Hol-
land 1988) and the internally consistent thermodynamic
Fig. 6. Relations between KI of white K-micas and their chemical
compositions from the Foederata Unit. Electron microprobe data
used in diagrams represent average chemical analyses of white K-
mica (n number of analyses). Samples (from bottom-left to top-
right): ZE1 (n = 3), TEL1 (n = 7), MB3 (n = 6), ZB1 (n = 6), DOPO1
(n = 3), ZB2 (n = 3), DOPO4 (n = 4), TRE2 (n = 3), ZE4 (n = 4).
Fig. 7. Pressure and temperature conditions calculated from the re-
action 3Cel = Phl + 2Kfs + 3Qtz a 2H
2
O with thermodynamic data
of Holland & Powell (1998) and chlorite thermometry (Cathelineau
1988; Jowett 1991).
dataset of Holland & Powell (1998). A pressure of ca. 4
4.5 kbar at a temperature of ~380 °C was obtained from the
intersection with the chlorite geothermometer (Fig. 7).
Discussion
In general, the illite crystallinity method has been used
mainly to set the beginning of metamorphism. Its accuracy de-
creases from the anchizone towards either diagenesis or epi-
zone (Kübler & Jaboyedoff 2000). The effect of the detrital
micas and illite-smectite on the KI decreases with burial and
disappears almost completely in the anchizone (Kübler & Ja-
boyedoff 2000).
The presented KI data point to metamorphic conditions of
the upper anchizone (samples from the Ve¾ký Bok Unit), but
most of the samples (Foederata Unit) belong to the anchizone/
epizone transition and epizone.
Plaienka et al. (1989) estimated the temperature of Alpine
metamorphism at ca. 350 °C in the Veporic cover rocks. By
contrast, Korikovsky et al. (1992) obtained lower tempera-
tures ranging between ca. 200 and 300 °C. Our KI and chlo-
rite thermometry results together with microtextural observa-
tions suggest higher metamorphic temperatures than the
previous estimates. Pressure conditions obtained by Mazzoli
et al. (1992) from the b
0
spacing in K-white micas gave up to
12 kbar and Korikovsky et al. (1997) assumed 89 kbar from
the phengite barometer of Massone & Schreyer (1987). This
study, however, suggests that pressure during the Alpine low-
grade metamorphism (at ca. 380 °C) was probably not so
high, not exceeding ca. 4.5 kbar in the cover metasediments.
374 LUPTÁK, JANÁK, PLAIENKA and SCHMIDT
Higher, amphibolite facies conditions of Alpine metamor-
phism (up to 620 °C and 10 kbar) were reached in the deeper
tectonic units of the Veporic core complex (Lupták et al.
2000; Janák et al. 2001), suggesting a metamorphic gradient
of ca. 15 °C/km.
Conclusions
Our results suggest that the studied metasedimentary rocks
in the Veporic Superunit were metamorphosed in upper an-
chizonal to epizonal (greenschist facies) conditions. The tem-
perature ranges from approximately 310330 °C in the north-
western parts of the Veporic cover, including the Ve¾ký Bok
Unit, up to approximately 335380 °C in the central and east-
ern parts (Foederata Unit). The estimated pressure conditions
reached about 4.5 kbar. Alpine metamorphism caused com-
plete recrystallization of former clay minerals and the growth
of newly formed white mica, chlorite and feldspars. These
data suggest that the Alpine regional metamorphic grade in-
creased from the Mesozoic cover to the underlying Late Pale-
ozoic and basement rocks in the Veporic Superunit, which is
consistent with a metamorphic core complex structure and the
Cretaceous tectonometamorphic evolution of this area out-
lined by Plaienka et al. (1999); Lupták et al. (1999, 2000)
and Janák et al. (2001).
Acknowledgments: This work is dedicated to late Martin
Frey who encouraged and supported new studies on Alpine
metamorphism in the Western Carpathians. We thank W.B.
Stern (Basel) for his help with X-ray measurements. The first
manuscript greatly benefited from the critical remarks by R.
Ferreiro Mählmann. Reviews by P. Árkai, A. Vozárová and
C. Mazzoli further clarified the paper and are greatly appreci-
ated. The research has been financially supported by the Slo-
vak Grant Agency for Science (Project No. 3167) and the Slo-
vak Agency for Support of Science and Technology APVT
(Project No. 20-020002) which is gratefully acknowledged.
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Locality
Sample
Description
Foederata Unit
DOBINÁ BROOK VALLEY
west of Dobiná town behind the Vyná Maa (Foederata) settlement
(DOPO)
DOPO1
fine-grained metaquartzite
DOPO2
micaceous intercalation (shist) within metaquartzite
DOPO4
banded (grey and pinkish layers) marble (Wetterstein type)
DOPO13
grey marble (Reifling type)
MALÁ BÔROVÁ MASSIVE
southern slope of the Malá Bôrová massive NW from the Klenovec town
(MB)
MB3
micaceous intercalation (schist) within fine-grained metaquartzite
RUINÁ DAM
eastern margin of the water dam near its vent
(RR)
RR1
micaceous metaquartzite
TELGÁRT
north of Telgárt, ca. 1100 m above sea level
(TEL)
TEL1
white mica, chlorite, quartz and plagioclase (± K-feldspar) schist
TEL3
fine-grained metaquartzite
TRESTNÍK MASSIVE
quarry located NE from the Tresník hill
(TRE)
TRE2
micaceous intercalation (schist) within metaquartzite
ZBOJSKÁ SADDLE
quarry in the saddle Zbojská (road from Brezno to Tisovec)
(ZB)
ZB1
micaceous greenish intercalation (schist) within metaquartzite
ZB2
white mica, chlorite, quartz and K-feldspar schist
ZELINOVÁ VALLEY
Zelinova valley (SW of Rejdová village)
(ZE)
ZE1
white mica, chlorite, quartz and plagioclase (± K-feldspar) schist
ZE4
fine-grained micaceous intercalation (schist) in metaquartzite
Ve¾ký Bok Unit (Luèatín Unit)
¼UBIETOVÁ and LUÈATÍN
Vôdka valley and the road between ¼ubietová and Luèatín villages
(LU and LUC)
LU6
fine-grained violet schist (Carpathian Keuper Fm.)
LUC7
metamorphosed micritic marly limestone
VALASKÁ VILLAGE
rock cliff above a dead arm of the Hron river (road from Valaská to Brezno)
(VAL)
VAL1
fine-grained violet schist (Carpathian Keuper Fm.)
Appendix
Localities and samples description.
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