GeolCarp_Vol53_No1_15

GEOLOGICA CARPATHICA, 53, 1, BRATISLAVA, FEBRUARY 2002

15 — 25

PALEOMAGNETISM OF METAMORPHIC ROCKS

FROM THE GEMERIDES (WESTERN CARPATHIANS)

JADWIGA KRUCZYK

, MAGDALENA KĄDZIAŁKO-HOFMOKL

, MARIA JELEŃSKA

IGOR TÚNYI

, UBOMÍR GAZDAČKO

and JACEK GRABOWSKI

Institute of Geophysics of the Polish Academy of Sciences, Ks. Janusza 64, 01 452 Warszawa, Poland

Geophysical Institute of the Slovak Academy of Sciences, Dúbravská cesta 9, 842 28 Bratislava, Slovak Republic

Geological Survey of the Slovak Republic, Werferova 1, 040 01 Košice, Slovak Republic

Polish Geological Institute, Rakowiecka 4, 00 975 Warszawa, Poland

(Manuscript received February 20, 2001; accepted in revised form June 13, 2001)

Abstract: The paper extends our previous study of metamorphosed Paleozoic rocks of the Gemeric Superunit (Kruczyk
et al. 2000) on four exposures of Paleozoic and two exposures of Triassic rocks. The anisotropy of magnetic susceptibil-
ity (AMS) results support the conclusion of previous study of its strong correlation with the tectonic Alpine fabric.
Paleomagnetic data, obtained here only for two exposures (one Paleozoic and one Triassic) fit the previous results which
indicate Middle Miocene remagnetization and subsequent rotations of respective tectonic blocks around local vertical
axes.

Key words: Gemeric Superunit, Paleozoic, Triassic, AMS, remagnetization, tectonic deformation.

Introduction

Our study of rock magnetism, AMS and paleomagnetic char-
acteristics  of  the  Gemeric  Superunit  began  with  research  on
Paleozoic  strongly  metamorphosed  rocks  (Kruczyk  et  al.
2000) from several chosen exposures: four of them lie along
the KMSZ (Košice-Margecany Shear Zone with character of
strike-slip  dextral  fault),  two  –  close  to  the  DSZ  (Dobšiná
Shear Zone parallel to the Transgemeric Shear Zone (TGSZ)
with character of strike-slip sinistral fault) and one – in the
middle of the unit. Each exposure represents a separate tecton-
ic  block  with  specific  succession  of  rotations.  The  results
show  evident  correlation  of  the  AMS  with  corresponding
shear  zones  and  remagnetization  of  rocks  during  the  Middle
Miocene,  followed  by  rotations  of  each  tectonic  fragment
around local vertical axes. The senses of rotations fit the char-
acter  of  shear  zones  close  to  the  respective  exposure:  clock-
wise (CW) rotations were observed in the exposures close to
the dextral KMSZ and counterclockwise (CCW) – for expo-
sures  close  to  the  sinistral  DSZ.  The  present  paper  extends
field of our study on Lower Paleozoic greenschists, phyllites
and metadiabases (four exposures) as well as Triassic metadia-
bases (one exposure) and marbles (one exposure).

The present paper finishes our study of Gemeric rocks, so

we will not only discuss the results of the second group of ex-
posures, but also compare them with that of the first group
(Kruczyk et al. 2000). At the end we will show our conclu-
sions concerning the paleomagnetic and tectonic implications
of our study.

Geological setting

Gemeric Superunit, being a part of the Inner Western Car-

pathians, is built up with Lower and Upper Paleozoic rocks as

well as Triassic rocks affiliated and divided according to indi-
vidual authors into various lithotectonic units.

Lower Paleozoic rocks are metamorphosed by regional

metamorphism  into  greenschist  and  amphibolite  (Grecula
1973; Dianiška & Grecula 1979; Hovorka et al. 1979; Faryad
1986;  Radvanec  1992)  facies.  They  suffered  ductile,  brittle-
ductile and brittle tectonization in shear zones trending NW-
SE  and  NE-SW.  Ductile  deformation  during  the  Variscan
orogeny  was  documented  with  the  foliation  planes  trending
NE-SW with moderate dips to the NW and N and brittle-duc-
tile  close  folds  of  south-vergence,  while  Alpine  overprint  is
characterized  by  fold-overthrust  structures  of  NW  vergency
and dips to the SE, representing the system of half-open to iso-
clinal folds with axial plane cleavage. Alpine structures origi-
nated in transpressional—transtensional shear zones with sinis-
tral shearing in the direction SW-NE and dextral shearing in
zones trending SE-NW (Grecula et al. 1991, Fig. 1). Shearing
caused mylonitization of rocks as well as their tectonic trans-
port  and  reduction.  According  to  geological  and  geochrono-
logical data the described shear zones have Alpine age 135 Ma
(Ar/Ar data from muscovite taken from the KMSZ; Maluski et
al.  (1993)  as  well  as  Dallmeyer  (1994)).  The  last  tectonic
record is characterized with brittle kink-folds having axes of
NW-SE and N-S directions as well as the joint systems.

The North Gemeric Upper Carboniferous formations

(Vozárová & Vozár 1988) are located in transgressive posi-
tion directly either on Rakovec Group (Bajaník 1962; Bajan-
ík et al. 1981) or Klátov gneiss-amphibolite complex. The
latter represents the tectonic overlier of the Rakovec Group,
the ductile shear zone of lower crust level. The transgressive
Upper Paleozoic sequences on the South of the Gemeric Su-
perunit (Máška 1957; Fusán 1959; Bajaník et al. 1981;
Vozárová & Vozár 1988) are overlain by the higher pressure
Bôrka Nappe (Leško & Varga 1980; Mello et al. 1983) affili-
ated to the Meliatic Unit.

16 KRUCZYK et al.

Fig. 1. Map of the shear zones of the Gemerides. RSZ – the Rejdová Shear Zone, DSZ – the Dobšiná Shear Zone, KMSZ – the Košice-
Margecany Shear Zone, TGSZ – the Transgemeric Shear Zone, HSZ – the Hodkovce Shear Zone. 1 – course of lithological units, 2 –
Variscan nappes, 3 – Alpine rejuvenated Variscan (?) shear zones, 4 – principal shear zones (Alpine), 5 – shear zones of lower order, 6
– faults with the character of pure shear (the youngest ones), black circles – sampling localities: C – Črmel, KV – Vyšný Klátov, J –
Jahodná, MA – Margecany, JA – Jaklovce, S – Slovinky, PD – Poráčska Dolina, H – Hnilčík, DO – Dobšinská Priehrada, ML –
Mlynky, GP – Gemerská Poloma, HD – Hajdova Dolina, SD – Šugovská Dolina (from Grecula et al. 1990, reprinted with permission).

Locality: Hnilčík (H) – quarry (Fig. 1)

Rocks of the Rakovec Group are represented by yellow-

green  to  violet-green  phyllites  with  intercalations  of  dark-
green metabasalt pyroclastics, often with calcite veinlets and
mineral assemblage chlorite, epidote, calcite, zoisite, hematite
and  rutile.  The  foliation  planes  310/30  are  accentuated  by
quartzy shear veins thick to 10 cm with local boudinage. Inter-
calation of greenish and violet lamina is a characteristic fea-
ture, similarly is their folding into open folds with b-axis 30/
10.  The  system  of  cleavage  planes  and  joints  has  directions
195/85 and 250/90.

Locality: Poráčska Dolina (PD) – Čierny bocian (Fig. 1)

Outcrop of strongly recrystallized metabasites of dark-green

to black-green colour with distinct block jointing 0/20 to 350/
20. They represent the tight overlier of strongly mylonitized
black phyllites. According to the amount of Fe-carbonates, the
metabasites are locally strongly weathered and have a brown-
ish appearance. They belong in all probability to the Zlatník
Formation of the North Gemeric Upper Carboniferous.

Locality: Slovinky (S) – quarry (Fig. 1)

The abandoned quarry contains laminated green-yellow to

violet-yellow phyllites with basalt pyroclastic bodies up to
several metres thick. They are representatives of the Rakovec
Group. Phyllites suffered brittle-ductile mylonitization in
planes 156/60 and are penetrated with the Riedel shears trend-

ing NW-SE to N-S, usually mineralized with quartz in thin
veinlets.

Locality: Hajdova Dolina (HD) – Smolník, 400 m to NE of

the agricultural cooperative farm

An outcrop of coarse-grained dark-green dolerites to basalt

metapyroclastics is present in a tight overlier of graphitic-seric-
itic phyllites with intercalations of psammites and lydites. They
are a constituent of a variegated volcanic complex (sensu Grec-
ula 1982). The mineral assemblage is chlorite, actinolite, calcite,
epidote, zoisite, albite ± pyroxene. In mesoscale only a joint sys-
tem of N-S trend with an inclination to both sides is observable.
In the tight overlier, graphitic-sericitic phyllites, the schistosity
156/56 is developed with the b-axis of the isoclinal fold 254/24.
Outcrop is located in the Transgemeric Shear Zone.

Locality: Jaklovce (JA) – cut of railroad westwards from

the Jaklovce lime-kiln (Fig. 1)

Dark-green to black-green ultrabasic rocks, associated with

red-violet radiolarites of Ladinian age, outcrop in the railroad
cut.  They  have  blocky  disintegration.  Their  joints  are  filled
with chrysotile asbestos. The metamorphic schistosity is 328/
48.  Their  mineral  composition  is  plagioclase,  clinopyroxene
(augite),  magnetite  and  ilmenite.  The  red  radiolarites  often
contain joints healed with specularite. The rocks are a repre-
sentantive  of  a  Jurassic  mélange  belonging  to  the  Meliatic
Unit.  The  outcrop  is  located  on  the  crossing  of  the  Transge-
meric and Košice-Margecany Shear Zones.

PALEOMAGNETISM OF METAMORPHIC ROCKS 17

Locality: Šugovská Dolina (SD) – abandoned quarry in the

valley termination (Fig. 1)

Quarry contains coarse-crystalline grey-white to brownish-

white  limestones.  They  often  outcrop  with  metabasic  rocks
(glaucophanites) and black schists. The rocks are affiliated to
the Bôrka Nappe, to the Meliatic Unit of Triassic—Jurassic age.
The  carbonates  are  penetrated  with  the  following  system  of
planes and joints: 130/80 with striations 85/70, and 40/76 with
striations  8/70  and  300/70.  Discontinuities  are  often  healed
with calcite veinlets.

Experimental procedure

Experimental study was done in the three laboratories: the

Geophysical Institute of the SAS (GPI SAS) in Bratislava, the
Institute of Geophysics of the PAS in Warsaw (IGP PAS) and
the Polish Geological Institute in Warsaw (PGI). The natural
remanent  magnetization  (NRM)  was  measured  with  the  JR5
spinner  magnetometer  of  Agico  and  demagnetized  thermally
with a non-magnetic oven in Bratislava (MAVACS – system
of Geophysics Brno). The demagnetization results were analy-
sed in the IGP PAS and in PGI in Warsaw with the PDA-pro-
gram package (Lewandowski et al. 1997). The measurements
of the magnetic susceptibility and its anisotropy (AMS) were
performed with the KLY-2 susceptibility bridge of Geophysics
Brno  in  Bratislava  and  Warsaw,  the  monitoring  of  magnetic
mean susceptibility during the procedure of thermal demagne-
tization  of  NRM  was  done  in  Bratislava.  For  calculation  of
anisotropy parameters the ANISO 11 program (Jelínek 1977)
has  been  used,  the  results  were  further  analysed  in  the  IGP
PAS with the Spheristat 2.0 program of Pangea Scientific.

The anisotropy parameters that will be discussed later com-

prise (Tarling & Hrouda 1993):

– mean low-field susceptibility
Km = 1/3(Kmax + Kint + Kmin), where Kmax, Kint, Kmin

are the maximum, intermediate and minimum susceptibilities,
respectively.

– anisotropy parameter
P’ = exp

√ 2 (η

—

)

+ (

—

)

+ (

—

)

where

= lnKmax,

= lnKint,

= lnKmin,

√η

– shape parameter T = (2

—

)/(

—

)

the anisotropy ellipsoid is prolate (lineation prevails) if T<0,
and oblate (foliation prevails) if T>0.

– direction of the axis of maximum susceptibility Kmax:

pole to magnetic lineation:,

– direction of the axis of minimum susceptibility Kmin:

pole to magnetic foliation
Mean magnetic susceptibility was measured in GPI SAS after
each heating step during the thermal demagnetization proce-
dure in order to monitor mineralogical changes caused by heat-
ing.

The identification of magnetic minerals was done through

the magnetic and non-magnetic methods. Magnetic methods
comprised: measurements of hysteresis parameters (Hc – co-
ercive force, Hcr – remanent coercivity, Ms – saturation
magnetization, Mr – saturation remanence) with the vibration
magnetometer VSM of Molyneaux (done in IGP PAS) and two

thermomagnetic methods. One, consisting of thermal decay in
a non-magnetic space of the isothermal remanence Ir acquired
in the field of 1 T during heating to 700 °C  in air was done in
the  IGP  PAS  with  the  non-commercial  TUS  device.  This
method  gives  values  of  blocking  temperatures  Tb’s  of  mag-
netic  minerals  present  in  the  rock,  observed  on  Ir-T  curves.
Another one, called the Lowrie method consists of thermal de-
magnetization of three components implied in the specimen in
three mutually perpendicular directions in fields of 0.1 T, 0.4
T and 1.3 T. Each component is carried by a mineral fraction
of  different  coercivity.  Temperatures  unblocking  the  respec-
tive component indicate the appropriate mineral – carrier of
this component (Lowrie 1990). This analysis, which is accom-
panied by the IRM (isothermal remanent magnetization) ac-
quisition  curves,  was  performed  in  the  PGI  in  Warsaw  with
the MMPM1 pulse magnetizer.

The non-magnetic methods comprised the optical microsco-

py and scanning electron microscopy (SEM) with microprobe.
The former was carried for the IGP PAS by J. Siemiątkowski
(PGI, Wrocław, Poland), the latter – by E. Starnawska (PGI
in Warsaw).

General characteristics of rocks

Exposures situated within the Rakovec Group

Hnilčík (H) – diabase pyroclastics and chloritic-sericitic

phyllites. Seven hand samples coming from two sides of the
quarry with different schistosity groups H1 and H2. The sup-
posed age of these rocks is Upper Devonian—Lower Carbonif-
erous (?). All methods of identification of magnetic carriers
indicate the presence of hematite: Tb temperatures observed
on Ir-T curves range between 650 and 690 °C (Fig. 2A), the
results of the Lowrie method show that the same temperatures
of about 690 °C unblock the soft, medium and high coercivity
fractions, IRM acquisition curves do not saturate in the high-
est field of the experiment, although the 90 % of saturation is
reached in the field of 0.4—0.6 mT (Fig. 3A), hysteresis curves
show the presence of high coercivity material (Table 1). The
presence of low coercivity fraction acquired in the 0.1 T, and
the dominance of the medium coercivity fraction acquired in
the 0.4 T suggests that the hematite grains are rather large.

Analysis of polished sections revealed the presence hema-

tite crystals of 2—18

µm and grains of pyrite of about 10 µm.

This was supported by the SEM and microprobe results.

Poráčska Dolina (PD) – greenschists. Five hand samples

of supposed Lower Paleozoic age (?). Thermomagnetic analy-
ses in zero field show the presence of hematite only, with Tb
of about 650—690 °C, Ir-T curves look identical as those for
Hnilčík (Fig. 2a). The three axis Lowrie thermal analysis re-
veals the presence of hard, medium and soft coercivity frac-
tions, all with blocking temperatures of 690 °C characteristic
for hematite, as it was observed in Hnilčík. In several samples
the low and medium coercivity fractions dominate over the
hard one. The presence of hematite components of varying
hardness is also reflected on the IRM acquisition curves (Fig.
3B,C). In specimens with prevailing soft and medium compo-

18 KRUCZYK et al.

nents  the  saturation  is  nearly  reached  at  0.8  T,  in  specimens
where  the  hard  component  dominates,  the  saturation  is  not
reached  even  in  the  highest  field  of  the  experiment  (1.4  T).
The values of coercivity and coercivity of remanence obtained
due  to  hysteresis  measurements  acquire  intermediate  values
(Table 1). These results imply presence of hematite in grains
of various sizes distributed within the rock.

Microscopic study reveal presence of post-ilmenite and

post-ilmenomagnetite  leukoxen  pseudomorphs  with  distinct
traces  of  tectonic  deformations  indicating  that  the  mineral
changes took place at temperatures of 250—300 °C (Dunlop &
Özdemir  1998).  Optically  identified  hematite  grains  have
lengths of 7—10

µm, and the SEM results confirm the presence

of large Fe-oxide grains with the Fe/O ratio of 69—71% / 27—
30 % given by the microprobe.

Slovinky (S) – phyllite greenschists. Nine hand samples of

supposed Lower Paleozoic age. Thermal analyses show pres-
ence of hematite with Tb’s of 650—690 °C, with the thermo-

Fig. 2. Results of thermomagnetic analysis performed in the non-
magnetic field. Ir – remanence acquired in the field of 1 T in arbi-
trary units, T – temperature in °C. A – Ir-T curve for H; B – Ir-T
curve for HD; C – Ir-T curve for JA.

magnetic Ir-T curves similar to that for Hnilčík (Fig. 2A). Ac-
cording to the Lowrie method the hard coercivity fraction pre-
vails in all specimens, in some of them the hard and medium
coercivity fractions is accompanied by the low coercivity frac-
tion with much lower intensity and unblocking temperature of
about 350 °C (Fig. 3D). Dominance of the high coercivity
component is reflected on the curves of the IRM acquisition
that do not reach saturation in the highest fields available
(same Figure). Hysteresis parameters (Table 1) are characteris-
tic for hematite.

According to the microscopic study hematite occurs mainly

within the laminae in the form of pallets of 5—21

µm – Fig.

4A – lower part. The elongated grains of Fe-oxides are also
revealed by the SEM, their Fe/O ratio being 70—71 % /29—
30 %. Fig. 4A – upper part shows the SEM image of tabular
and elongated grains of hematite present in the K rocks.

Exposure situated within the Gelnica Group

Hajdova Dolina (HD) – metadiabases and schists. Four

hand samples of supposed Lower Paleozoic age. Both thermo-
magnetic analyses show the presence of magnetite with Tb’s
of about 580 °C and mineral with Tb’s of 350—400 °C, perhaps
post-pyrite Fe-oxide or Fe-sulphide sometimes accompanied
by goethite with Tb of 150—200 °C (Fig. 2B and Fig. 3E). Ac-
cording to the IRM acquisition curves the prevailing low coer-
civity mineral reaches saturation in the fields of 0.2—0.3 T
(Fig. 3E). Hysteresis parameters for metadiabases (samples 34
and 35) are characteristic for magnetite, those for schists (sam-
ple 32) indicate the presence of maghemite (Table 1).

The results of optical microscopy indicate presence of post-

ilmenomagnetite pseudomorphs of 100—500

µm. The SEM

analysis indicates presence of titanite, small grains of Fe-ox-
ides with the Fe/O ratio obtained through the microprobe be-
ing 58 %/38 % and also presence of sulphur. It suggests that
the magnetite identified through magnetic methods may be of
post-pyrite origin.

Exposures situated within the Meliatic Unit

Jaklovce (JA) – metadiabases, six hand samples, sup-

posed age – Lower and Middle Triassic. For the JA speci-
mens only thermomagnetic analysis in the compensated mag-
netic field was performed because their remanences acquired
in consecutive external fields according to the Lowrie method
were too high to be measured. The Ir-T curves show the pres-
ence of magnetite with Tb’s of about 570—580 °C, Fig. 2C.
Values of hysteresis parameters (Table 1) support this conclu-
sion.

According to the optical microscopy the metadiabases are

only weakly metamorphosed – the fine albite and chlorite-
epidote veins implicate the beginning of metamorphic process-
es. Skeletal magnetites characteristic of deep oceanic basalts
(Freeman 1986) occur in grains of 7—17

µm, in some of them

processes of oxidation into maghemite have begun (Fig. 4B –
lower part). The SEM results show the presence of skeletal as
well as dendritic magnetite or maghemite grains (Fig. 4B –
upper part) with Fe/0 ratio 66—69 %/28—31 %.

PALEOMAGNETISM OF METAMORPHIC ROCKS 19

Šugovská Dolina (SD) – metamorphosed carbonates (mar-

bles). Four hand samples with assumed age of Middle Trias-
sic. Specimens were too weak for thermomagnetic analysis in
the non-magnetic field to be done therefore only the Lowrie
method was applied to them. The results indicate the presence
of two minerals: goethite with Tb of about 100 °C and a min-
eral with Tb of about 400 °C, probably fine-grained magnetite
or maghemite (Fig. 3F), the same is seen on the IRM acquisi-
tion curves showing its increase in the whole range of avail-
able fields. Hysteresis parameters (Table 1) support the con-
clusion about the presence of high coercivity minerals in the
studied rocks. The mean susceptibility Km is very low ranging
from —10 to 11

×10

—6

SI. Negative Km values observed in sev-

eral specimens indicate the dominance of diamagnetic miner-
als in them.

The pigment with cherry red colouring, identified as Fe-hy-

droxides is visible in the optical microscope.

Summary: The magnetic properties of the Paleozoic rocks from the Ra-
kovec Group are connected mainly with hematite, whereas in the Gelni-
ca rocks magnetite/maghemite probably of post-pyrite origin, pyrrhotite
and goethite were identified. The Triassic rocks from the Meliata Group
carry magnetite/maghemite (JA) and goethite accompanied by magne-
tite or maghemite (SD).

Exposure

Sample
number

(µA.m

)

(µA.m

)

(mT)

Hcr

(mT)

magnetic mineral

H1+H2

40
41
42

1.49
5.55
9.98

0.47
4.72
9.04

127
140

180
175

hematite

10
11

1.76
1.36
1.30
0.45

1.15
0.96
0.73
0.13

75
73
71
29

100

110

hematite

12
14
20

7.03
0.97

10.58

6.54
0.67
8.51

256
287
384

325
450
375

hematite

32
34
35

0.21
1.18
1.24

0.06
0.20
0.42

21.5

6.5

16.5

200

38
50

magnetite/maghemite

4
5

2440.8

3861.7

151.0

367.8

4
9

15
55

magnetite/maghemite

27
28
29

0.34
0.18
0.23

0.04
0.04
0.05

17.5
26.5

130
200
200

goethite and
magnetite/maghemite

Table 1: Hysteresis parameters of rocks from this study.

Locality

× 10

–6

Kmax

magnetic lineation

D/I

Kmin

pole to magn. fol

D/I

P’

Tectonic lineation

L corresponding to magnetic

lineation

Tectonic foliation

S corresponding to

magnetic foliation

RAKOVEC GROUP (Paleozoic)

300–560

249/13

15/61

1.10–1.22

290–740

56/8

163/65

1.10–1.29

660–780

61/7

168/58

1.05–1.13

130–470

50/29

177/39

1.01–1.08

GELNICA GROUP (Paleozoic)

100–850

103/63

scattered

248/22-scattered

1.004–1.02

none

MELIATA GROUP (Triassic)

–11–11

scattered

1.03–1.13

none

S2 (?)

25000–96000

87/4

358/15

1.04–1.09

L2–L3

none

Table 2: Susceptibility and AMS results compared with tectonic data.

AMS study

The magnetic low field susceptibility of the studied rocks

show  differences  corresponding  to  the  different  lithologies:
from diamagnetic marbles from SD to strongly ferrimagnetic
ultrabasic  rocks  from  JA.  The  appropriate  ranges  of  the  Km
are cited in Table 2 together with values of anisotropy parame-
ter P’. The lowest values of P’ are to be find in HD where it
ranges from about 1.005 to 1.02. The anisotropy ellipsoids are
rather  oblate,  although  some  manifest  weak  prolateness  (see
Fig. 5A). The prevailing P’ values for the Rakovec and Melia-
ta localities are situated between 1.002 and 1.15, the less nu-
merous group has P’ between 1.25 and 1.32 in Rakovec and
1.20  and  1.30  in  Meliata.  Anisotropy  ellipses  are  prolate  in
PD, prolateness prevails also in JA. In the SD rocks of both
shapes occur in similar proportions and in H and S rocks, ob-
late ellipsoids are in the majority (Fig. 5B,C).

The directions of Kmax and Kmin axes are shown in Table

2 together with tectonic lineations (L) and foliations (S) which
correspond  to  the  magnetic  fabric.  According  to  Návesňák
(1993) there are in the Gemerides three systems of mylonitic
schistosity S2, S3, S4 and two lineations L2 and L3, caused by
the Alpine tectonics. The most characteristic lineation L2 (azi-
muth 230—240° or 60° with a low dip) is associated with the
TGSZ zone, mylonitic foliation S2 (azimuth of about 165° and
dip of about 40° with a scatter from 0° to 70°) and foliation S3
(azimuth of 293°—335° and low dip) are due to compression
linked with the TGSZ and other, parallel shearing zones. The
lineation  L3  reflecting  the  East  Carpathian  system  trends  to
290° or 100° with a shallow dip. The foliation S4 (azimuth of
230°—235° and dip of about 45°) is associated with the KMSZ
zone (see also Kruczyk et al. 2000). Fig. 6 and Fig. 7A,B show
the magnetic lineations and foliations compared with the tec-
tonic ones. These figures include, apart of the results from the
present study, the appropriate results of the previous investiga-
tions  (Kruczyk  et  al.  2000)  as  well.  The  correspondence  be-
tween the magnetic and tectonic lineations (L2 and L3 shown
as crosses on Fig. 6) is clear: magnetic lineation remains very
close to the L2 in five localities (both wings of H: H1 and H2,
PD, S, DO, ML) in one (MA) it is close to the L3, in one (JA)
the magnetic lineation lies between the two tectonic ones. In

22 KRUCZYK et al.

four  localities  (C,  KV,  HD,  J)  two  of  which  (HD  and  J)  are
characterized by low anisotropy (see Table 3 in Kruczyk et al.
2000 and Table 2 of this study) Kmax directions have interme-
diate—high inclinations and do not show a straightforward rela-
tionship either with the L2 or with L3 lineations. The magnetic
foliation  planes  for  the  rocks  of  this  study  (Fig.  7A)  corre-
spond to the tectonic foliation S2 (H1) or S3 (H2, PD). In S
and JA – the magnetic foliation does not correlate with any of
the  tectonic  ones,  which  corresponds  to  their  relatively  low
anisotropy suggesting a low degree of deformation. No corre-
lation  of  magnetic  and  tectonic  fabrics  was  observed  in  HD
which has very low P’ values indicating that the HD rocks are
hardly deformed. Fig. 7B shows the relations of magnetic and
tectonic foliations obtained in the previous study (Kruczyk et
al. 2000). It implies relations of magnetic foliations of locali-
ties situated along the KMSZ (C, J, MA) with the S4 foliation,
which does not appear in the present study, and relation of the
magnetic foliations of other localities with S2 and S3 as is ob-
served here.

Paleomagnetic results, discussion and summary

The specimens were demagnetized thermally. The majority

of them responded well to the treatment (Fig. 8) giving Zijder-
veld  diagrams  approaching  origin.  The  principal  component
analysis revealed that the NRM is either single component or
composed  of  two.  Unfortunately,  the  obtained  characteristic
directions are highly scattered and only in two cases (HD and
JA) have we been able to calculate the mean exposure direc-
tions  with  reasonable  confidence  parameters,  (see  Table  3).
The directions obtained (in situ in both cases) differ in declina-

Fig. 5. Parameter of anisotropy P’ plotted against the shape pa-
rameter T. A – Hajdova Dolina; B – Hnilčík, Poráčska Dolina
and Slovinky; C – Jaklovce and Šugovská Dolina.

Loc.

N/n

D/I [°]

In situ

D/I [°]

corr.

[°]

pol

∆D=Do-Dr

[°]

localities influenced by the dextral East-Carpathian shearing system

6/7

313/-60

127 CW

3/6

190/-65

4 CW

5/8

109/72

25/62

65%

N 19 CW

localities influenced by the sinistral West-Carpathian shearing system

9/12

320/51

303/61

45%

N 63 CCW

5/8

68/70

2/61

45%

N 4 CCW

3/17

347/71

N 19 CCW

localities influenced by both shearing systems

3/5

275/65

N 92 CCW

3/10

18/63

278

N 12 CW

mean inclination calculated for Gemerides

Table 3: Mean directions for Gemerides with rotation angles Geo-
graphic position: 20.5°E, 48°N.

Reference data:
E after Besse & Courtillot (1991) for Stable Europe, 10—20 Ma D = 6, I = 62.
CS after Balla (1987) for Central Slovakia, rad. age 11—17 Ma D = 10, I = 64
Loc. – locality, N/n – number of hand samples/number of specimens taken for
calculations, D/I in situ – declination/inclination before tectonic correction for
bedding or schistosity, D/I corrected – declination/inclination after tectonic cor-
rection (45% or 65% untilting)

, K – parameters of Fisher statistics, pol –

polarity of specimnes taken for calculations (N – normal, R – reverse), CW –
clockwise, CCW – counterclockwise, Do – declination obtained in this study,
Dr – reference declination,

∆D – angle of local rotation.

PALEOMAGNETISM OF METAMORPHIC ROCKS 23

tions and have inclinations of 63° with

of 7° for JA, and

71° with

of 14° for HD indicating the Tertiary age of re-

magnetization. They are shown in Table 3 and Fig. 9 together
with the results obtained in our previous study (Kruczyk et al.
2000) in order to enable the wholesome paleomagnetic analy-
sis for the region. As is easily seen, the new results follow the
pattern observed previously. The mean inclination calculated
from means for all exposures combined, labeled G in Table 3,
is 64°. Very similar values are found for the Neogene volcanic
Middle Miocene rocks from Central Slovakia (Balla 1987) and
Neogene  rocks  from  the  East  Slovak  Basin  (Márton  et  al.
2000): mean inclination calculated for the purpose of this pa-
per from data of the cited paper of Balla for Central Slovakia
(CS)  is  64°,  and  declination  10°,  the  results  of  the  study  by
Márton et al. (2000) gave inclination of 63° and different dec-
linations for different localities. These values agree well with
the reference data for the Stable Europe Middle Miocene rocks
(E) (Besse & Courtillot 1991) with the inclination of 62° and
declination of 6°. The E and CS data are included in Table 3
and Fig. 9. Repeating the procedure applied in Kruczyk et al.
(2000) we tried to fit the results obtained for HD and J to the E
result. It may be done rotating independently both fragments
represented  by  our  exposures  respectively  by  12°  CW  (JA)
and 19° CCW (HD) – see Table 3.

Table 3 presents, apart of paleomagnetic directions, also the

rotation angles for all the exposures. They are grouped accord-
ing to their situation against the main shearing zones. The pa-
leomagnetic declinations in the exposures KV, J and GP reveal
clockwise  rotations  suggesting  the  influence  of  the  dextral
East-Carpathian  system.  The  AMS  results  confirm  this  con-
clusion  in  the  case  of  J  (Fig.  7A,  Table  3  in  Kruczyk  et  al.

Fig.  6.  Results  of  the  AMS  analysis:  comparison  of  directions  of
magnetic  (black  squares)  and  tectonic  (crosses)  lineations    for  all
exposures combined.  L2 and L3 – appropriate directions of tec-
tonic lineations (see text),  remaining letters denote respective ex-
posures as in Fig. 1.

2000).  The  paleomagnetic  declination  of  the  exposures  DO,
ML, HD and MA were rotated anticlockwise (CCW) suggest-
ing that they were influenced by the sinistral West-Carpathian
system. This conclusion is supported by the AMS results ob-
tained for ML and DO, whereas in the case of MA the AMS
shows  distinct  correlation  with  the  dextral  East-Carpathian
system (Fig. 6, Fig. 7A and Table 2). The declination of the
exposure JA is rotated clockwise (CW), whereas the direction
of its lineation lies between tectonic lineations of both systems
and magnetic foliation does not correlate with any of the tec-
tonic ones (Fig. 6, Fig. 7B and Table 2). We therefore suppose
that MA and JA are influenced by both shearing systems. The
results  of  AMS  study  obtained  for  KV,  GP  and  HD,  despite
their either clockwise (KV and GP) or anticlockwise (HD) ro-
tations, do not show any distinct correspondence with the tec-
tonic fabric.

The above discussion proves that the studied Gemeric rocks

of various ages, at least those that give reasonably grouped di-
rections of characteristic remanence, became remagnetized
during the Middle Miocene, prior to the rotations of individual
fragments of the unit. The rotations were due to the tectonic

Fig. 7. Results of AMS analysis:  comparison of magnetic foliation
planes  (thin  lines)  with  tectonic  foliation  planes  (thick  lines).  A  –
for  the  exposures  of  the  previous  study;  B  –  for  the  exposures  of
this study. S2, S3, S4 – tectonic foliation planes (see text), remain-
ing letters denote respective exposures as in Fig.1.

PALEOMAGNETISM OF METAMORPHIC ROCKS 25

grouped characteristic components of NRM. The mean expo-
sure inclinations lie between 61° and 71° and differ in declina-
tions. The NRM has normal polarity in all except two expo-
sures, in two exposures demagnetization took place during
folding (see Kruczyk et al. 2000) which shows that remagneti-
zation was not synchroneous in all places.

3. Mean inclination for Gemerides calculated from the expo-

sure means labeled G is 64° and agrees with reference data for
the Stable Europe and data from other Slovak regions for the
Middle Miocene meaning that all the studied rocks became re-
magnetized in this period.

4. After remagnetization the tectonic blocks represented by

the respective exposures were rotated due to the Alpine tecton-
ic activity: blocks related to KMSZ rotated clockwise, blocks
related to TGSZ rotated anticlockwise, in two cases the influ-
ence of both systems is observed.

Acknowledgments: The work was done in the frame of the
scientific cooperation between the Slovak Academy of Scienc-
es, Polish Academy of Sciences and Polish Geological Insti-
tute, with the support of the Institute of Geophysics of the Pol-
ish Academy of Sciences, Project 5/2000 as well as Project
6.20.1225.00.0 of the Polish Geological Institute and Project
VEGA No. 5136/98 of the Geophysical Institute of the Slovak
Academy of Sciences. The authors thank Mgr. D. Gregorová
for performing measurements of anisotropy of susceptibility.

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