GEOLOGICA CARPATHICA, 51, 2, BRATISLAVA, APRIL 2000
METAMORPHIC EVOLUTION OF GABBROIC ROCKS OF THE
BÓDVA VALLEY OPHIOLITE COMPLEX, NE HUNGARY
Laboratory for Geochemical Research, Hungarian Academy of Sciences, Budaörsi út 45., H-1112 Budapest, Hungary;
(Manuscript received June 22, 1999; accepted in revised form December 8, 1999)
Abstract: The Alpine polyphase metamorphic evolution path of the Bódva Valley Ophiolite Complex was recon-
structed using mineral paragenetic observations, mineral chemical and thermobarometric data obtained on metagabbroic
samples from boreholes in the Rudabánya Mts., NE Hungary. The dismembered ophiolite complex forms part of the
Meliata Unit of the Inner Western Carpathians. The recognizable, first blueschist facies event (min. 700800 MPa,
350500 °C) was followed by a nearly isothermal decompression to 400600 MPa in the greenschist facies. The
following metamorphic event was characterized by temperature increase up to 500600 °C in isobaric conditions to
the albite-epidote-amphibolite facies. The P-T path is best explained by subduction, which was followed by uplift
without any significant change in the temperature conditions. The late temperature increase might be caused by
thermal relaxation following subduction.
Key words: Inner Western Carpathians, Rudabánya Mts., ophiolite complex, gabbro, metamorphism.
Metamorphic features of ophiolites provide an effective tool
for reconstructing the tectonic conditions of closure of paleo-
ceanic branches. Rocks of mafic composition predominate in
ophiolite suites, and their intrusive members (mainly gabbros)
may form huge sequences up to a few hundred of meters in
thickness. Blueschists and other high-pressure metamorphic
rocks described as features of subduction zones occur
within two tectonic zones of the Western Carpathians: south of
the Pieniny Klippen Belt as pebbles in Cretaceous
conglomerates (e.g. Dal Piaz et al. 1995 and Faryad 1997) and
in the Meliata Unit (e.g. Kamenický 1957; Faryad 1995 and
Mello et al. 1998). Recent studies revealed that the metabasic
rocks occurring in the Meliata Unit in NE Hungary also show
blueschist facies metamorphism and a greenschist facies
overprint (Horváth 1997).
The aim of the present paper is to characterize the petrolo-
gy and the metamorphic P-T conditions of the gabbroic
rocks of the Bódva Valley Ophiolite Complex (BVOC), on
the basis of the metamorphic petrological results obtained
from representative sections of these rocks cored by the
boreholes Bódvarákó Br-4, Komjáti Ko-11 and Szögliget
Szö-4. These boreholes are located in the Rudabánya Moun-
tains along the Darnó Fault Zone, NE Hungary (Fig. 1).
The dismembered BVOC is related to the Meliata Unit
(Fig. 1), which is supposed to represent an oceanic suture
zone of the Vardar (s.l.)-Meliata ocean of TriassicJurassic
age in the Neotethyan realm, in the southern part of the In-
ner Western Carpathians (Mahe¾ 1986). Apart from the
blueschist facies metabasic and metasedimentary rocks, the
Meliata Unit consists of low grade, very low grade and un-
metamorphosed limestones, sandstones, phyllites, slates
and shales, which were mapped as a single tectonic unit
(Mock 1978). Structural investigations indicate that the var-
iously metamorphosed rocks are in tectonic contact within
the unit (Neubauer et al. 1992). Recently, Mock et al. (1998)
described the type locality of the Meliata Unit, near the vil-
lage of Meliata, as a tectonic half-window with repeated
discontinous tectonic slices. These slices are composed of
Jurassic deep-water shales with various large blocks of old-
er (mainly) Triassic rocks. The shales were most likely ac-
cumulated in an accretionary wedge.
The oceanic slivers of the Meliata Unit in NE Hungary
represent slices and small (from dm to 100 m in scale) frag-
ments embedded in the ductile Upper Permian Perkupa
Evaporite Formation found in the basal part of the non-
metamorphic Silica Nappe that forms the uppermost nappe
in the area studied (Fig. 1). The Silica Nappe is underlain by
the intermediate-high pressure/low temperature metamorphic
Torna Nappe (Árkai & Kovács 1986 and Kovács et al. 1996
97) and the Paleozoic rocks of the Gemeric Superunit. The
Silica and Torna Nappes and the Meliata Unit built up the
South Gemer nappe system of the Gemer-Bükk units of the
Pelsonia composite terrane (Kovács et al. 1996-97), also
known as the North Pannonian or ALCAPA (Alpine-Car-
pathian-Pannonian) Unit (Balla 1982; Csontos et al. 1992
and Csontos 1995) which was assembled with other West-
Carpathian units during the Miocene (Csontos 1995).
Plaienka et al. (1997) infer that these nappes form the Meli-
ata Belt of the Inner Western Carpathians.
On the basis of sporadic biostratigraphic data from radiolar-
ites synchronous with pillow basalts the age of the magmatism
in the BVOC is thought to be Middle Triassic (Dosztály &
Józsa 1992). The main concern with the K/Ar data from the
BVOC (256 ± 26 Ma on amphibole, 233 ± 10 Ma on biotite,
115 ± 5 Ma on feldspar and 210 ± 12 Ma on whole rock, Árva-
Sós et al. 1987) is that the mineral chemical compositions (and
consequently, the eventual magmatic or metamorphic nature)
of the analyzed phases were not checked before the measure-
ments, so this may be the reason why there is a large scatter
between the results (from 110 Ma to 270 Ma). The blueschist
facies metamorphism occurred in middle Jurassic times (150
165 Ma, K/Ar and
Ar ages on phengite from the Slovak
part of the Meliata Unit, see Maluski et al. 1993 and Faryad &
Henjes-Kunst 1997). Such middle Jurassic data have not been
obtained from the BVOC rocks so far, notwithstanding that a
comparison between the Alpine metamorphic evolution of the
two areas is assumed (Horváth 1997).
Fig. 1. a Tectonic sketch map of the Alpine-Carpathian area. Box indicates the investigated area. b Geological map of the Agg-
telek-Rudabánya Mts. and adjacent areas with the localition of the boreholes investigated.
The boreholes studied are located in the Rudabánya Moun-
tains along the Darnó Fault Zone in NE Hungary. The profiles
of the boreholes where samples were collected are shown in
Fig. 2. Major element analyses are given in Table 1. Compre-
hensive studies of the geochemical character of the BVOC
rocks were performed by Réti (1985), Harangi et al. (1996)
and Horváth (1997), who all confirmed the MORB character
of the ophiolite complex in question, therefore we do not dis-
cuss this problem in detail in this paper.
Under a ca. 150 m thick Tertiary and Quaternary cover the
borehole Komjáti Ko-11 cut through an approximately
200 m thick metamafic complex which is built up predomi-
nantly of metagabbro and its finer-grained variant (metadol-
METAMORPHIC EVOLUTION OF GABBROIC ROCKS 123
metagabbros and metadolerites, the latter being present in a
smaller proportion, while the lower part is dominated by
metadolerites cut by several metabasalt veins. After a tec-
tonic contact at a depth of ca. 280 m, dolomite and evaporite
represent the Silica Nappe.
Among the boreholes studied, the borehole Bódvarákó
Br-4 displays the most complex geological profile. In the up-
per part, two serpentinite slices separated by thin (ca. 30 m)
dolomite and dolomitic marl layers are found. Below the
serpentinites, coarse-grained metagabbro and metabasalt
occur. The lower part of the section consists of sedimentary
rocks of the Silica Nappe, with 200 meters of Upper Permi-
an evaporite and a few tens of meters of Anisian Gutenstein
Summarizing the comprehensive description of the bore-
holes we can say that the metamafic rocks of the BVOC do
not form a single tectonic unit at present, as they are imbri-
cated with the unmetamorphosed sedimentary sequences of
the Silica Nappe, and the profiles of the studied boreholes
are quite different from each other.
In addition to macro- and microscopic investigations bulk
chemical and electron microprobe analyses were performed
to check the chemical composition of the major rock-form-
ing minerals and the eventual effects of the whole-rock
chemistry on them.
The major element chemical analyses were done by a Per-
kin-Elmer 5000 AAS, using lithium metaborate digestion in
the Laboratory for Geochemical Research, Hungarian Acade-
my of Sciences. Other methods such as gravimetric for SiO
O, permanganometric for FeO and volumetric for CO
were also applied.
Qualitative and quantitative chemical analyses of minerals
were carried out by a JEOL JXCA-733 electron microprobe
equipped with 3 WDS, using the measuring program of Nagy
(1984) in the Laboratory for Geochemical Research, Hungari-
an Academy of Sciences. The measuring conditions were
15 kV, 40 nA, defocused electron beam with a diameter of 5
m, measuring time 5 s. Matrix effects were corrected by
Fig. 2. Geological profiles of the studied boreholes Bódvarákó
Br-4, Komjáti Ko-11 and Szögliget Szö-4.
Table l: Representative bulk rock compositions from the BVOC
erite), described earlier by Réti (1985) as albite-gabbro and
-dolerite. The contact between this complex and the underly-
ing Upper Permian Perkupa Evaporite Formation belonging
to the Silica Nappe is tectonic. The metamafic complex is cut
by several, thin (ca. 3050 cm thick) albitite veins and a 50
cm thick metabasalt vein. Albitites represent metamorphosed
intermediate-acidic rocks which form small portion in com-
plete ophiolite sequences (see e.g. Coleman 1977).
The borehole Szögliget Szö-4 is located close to the only
surface exposure of the BVOC, at the Tilalmas-tetõ (-hill),
where Vitális (1909) described a strongly weathered met-
agabbro believed to be occurring as diorite dyke. The upper
portion of the metamafic complex is composed of mainly
using the method of Bence & Albee (1968). The following
standards were used for quantitative analysis: orthoclase (K,
Al, Si), synthetic glass (Fe, Mg, Ca), spessartine (Mn), rutile
(Ti) and albite (Na). Statistical (absolute) errors expressed as
are as follows: SiO
±0.05, FeO ±0.2, MgO ±0.1, MnO ±0.05, CaO
O ±0.03, and K
O ±0.02 %. Some analyses
were done at the Department of Petrology and Geochemistry
of the Eötvös University, Budapest, using an AMRAY 1830 I/
T6 scanning electron microscope, under operating conditions
of 15 kV accelerating voltage and 12 nA specimen current. In
order to avoid the effects of the different measuring systems,
repeated analyses of the same measuring points of some of the
samples were performed by both electron microprobe analy-
sers. The calculations of cation numbers for amphiboles fol-
low the scheme of Robinson et al. (1982).
Thin section studies reveal that despite the strong meta-
morphic effects most of the investigated metagabbro sam-
ples preserved their original magmatic textures. Neither
schistosity nor lineation could be observed. The investigated
samples can be divided into three main types, namely: met-
agabbros (and -dolerites), metabasalts and albitites.
Fig. 3. BSE images of textural features in the BVOC samples. Ab-
brevations are after Bucher & Frey (1994). a The stable associ-
ation of hornblende-chlorite-epidote in metagabbro, b relic
magmatic clinopyroxene rimmed by biotite and albite, c bi-
otite-epidote assemblage in metagabbro, d relic crossite in acti-
nolite, e actinolite core rimmed by zoned hornblende (Hbl
) with chlorite (arrow marks the chemical compositions pre-
sented in Fig. 4a).
METAMORPHIC EVOLUTION OF GABBROIC ROCKS 125
The dominant rock type of the studied boreholes is coarse-
grained (>5 mm) metagabbro. Its variants exhibit ophitic to
subophitic texture, and sometimes grade into finer-grained
(13 mm) metadolerite. Metagabbros and metadolerites con-
sist of actinolite, hornblende, epidote, albite, chlorite, quartz ±
clinopyroxene, blue amphibole, biotite, titanite, Fe-Ti-oxides,
apatite and zircon. In these rocks the association actinolite
and/or hornblende, epidote, chlorite, albite and quartz is the
dominant mineral assemblage (Fig. 3a). Clinopyroxene is a
relic magmatic mineral in the Szögliget and Bódvarákó gab-
bros. It shows pinkish pleochroism and is rimmed by amphib-
ole or biotite (Fig. 3b). Blue amphibole shows blue-violet ple-
ochroism, usually rims the brownish hornblende and occurs
also as fissure fillings. Actinolite with pale brown-green or
green pleochroism is abundant and rims both the hornblende
and the blue amphibole and contains them as relics as well
(Fig. 3d) or is rimmed by hornblende (Fig. 3e). Actinolite is
sometimes sprinkled with an aggregate of small, green euhe-
dral biotites. The other type of occurrence of biotite is brown
flakes together with epidote rimming clinopyroxene (Fig. 3b
and 3c). Biotite was found only in the Szögliget and Bód-
varákó gabbroic bodies, where relic clinopyroxene was pre-
served as well. Epidote is also abundant and shows euhedral
and subhedral forms. Two types of epidote can be seen: big
(up to 5 mm) crystals and smaller crystal aggregates, which
sometimes rim the bigger ones. Albite commonly displays
subhedral forms and is twinned occasionally. Chlorite is found
in the matrix and forms pseudomorphs after clinopyroxene.
Apatite, titanite, zircon and Fe-Ti-oxides were found as acces-
sory minerals. In some cases apatite and titanite form cm large
Metabasalts show intergranular or intersertal texture, with
matrix consisting of chlorite, albite, epidote and opaque min-
erals. Replacing phenocrysts and filling amygdules we can
find abundant actinolite, chlorite, calcite, minor albite, epi-
dote and biotite. The metabasalts are cut by numerous veins
filled usually by actinolite, calcite, and rarely calcite-epidote-
chlorite assemblage is found as well. The metabasalt complex
sometimes grade into metadolerites or cut them.
Albitites are present only in the Komjáti-11 borehole.
Phengite and chloritoid were found with apatite as an accesso-
ry phase in the albitite veins additionally to albite and chlorite
(Horváth 1997). Aggregates of chloritoid and matrix phengite
seem to be in equilibrium with each other, while chlorite was
found in the albite-rich matrix. Albite and apatite contain vary-
ing amounts of fluid inclusions, which may be the target of fu-
Results only from the gabbros and their diagnostic metamor-
phic mineral assemblages containing amphibole, biotite, chlo-
rite and epidote, are presented in this paper. The mineral
chemistry of preserved magmatic phases and the other meta-
morphic rocks (metabasalts and albitites) and their role in the
magmatic and/or metamorphic evolution of the BVOC will be
discussed separately. Cation numbers are calculated for 23 ox-
ygens for amphibole, 22 for biotite, 20 for chlorite and 12.5 for
Amphibole shows a wide range of chemical compositions
even in the same sample, and it looks heterogeneous locally in
some BSE images with varying Fe/Mg (Fig. 3a,d). Represen-
tative analyses of amphiboles are given in Table 2. Horváth
(1997) found evidence for the existence of several generations
of amphiboles: namely a magmatic, and two metamorphic
ones. The subdivision of Ca-amphiboles is based on the fact
that magmatic Ca-amphiboles are enriched in Ti, Al and Na,
and depleted in Si as compared to metamorphic amphiboles
(Mével 1988 and Sadek Ghabrial et al. 1996). Relic Na-am-
phiboles [riebeckite, according to the nomenclature of Leake
et al. (1997), Fig. 4c] and Ca-Na-amphiboles (winchite) to-
gether with actinolite and magnesiohornblende were found,
which formed the first evidence of polyphase metamorphism
in the BVOC (Horváth 1997). The preservation of relic mag-
matic or metamorphic amphiboles is a common phenomenon
in metabasic rocks. However we have to emphasize that mag-
matic amphiboles were not found in the Szögliget and Bód-
varákó samples. Beside these data new mineral chemical data
published in this paper reveals a systematic change in the min-
eral chemistry of metamorphic Ca-amphiboles depending on
the various P-T conditions experienced by the rock samples.
The metamorphic Ca-amphiboles from the Szögliget samples
are edenite-pargasite or magnesiohornblende according to the
nomenclature of Leake et al. (1997), while the Komjáti am-
phiboles fall into the actinolite or magnesiohornblende field
(Fig. 4a,b). Some relic barroisite and winchite (Na-Ca-am-
phiboles), with intermediate Na
(around 0.7) and Al
0.9) compared relatively to Na-amphiboles and hornblendes,
were also found (Fig. 5) in the Komjáti and Szögliget samples.
Two generations of metamorphic Ca-amphiboles were found
in the Komjáti samples, as was also shown by Horváth (1997).
This fact could also be the result of differences in the bulk
14.897 14.876 15.214 15.275 14.968 15.155 15.566 15.451
Table 2: Representative chemical compositions of amphiboles
from the BVOC.
chemistry of the samples occurring on the microdomain scale.
Taking into account that we found zoned Ca-amphiboles with
an actinolitic core rimmed by magnesiohornblende (Fig. 3e
and 4a) this interpretation is not supported by the author. We
think that the systematic change from actinolite to magnesio-
hornblende (Fig. 4a) is a result of changing P-T conditions and
can be used for geothermobarometric calculations. Horn-
blendes are usually richer in Al and poorer in Si compared to
actinolites (Table 2), while their Na
content is almost the
same (Fig. 5). These changes are reflected in the chemistry of
chlorites as well, but in the opposite order, as chlorites found
in equilibrium with hornblende have lower Al and higher Si
content than chlorites in equilibrium with actinolite (Table 3).
Fig. 4. Chemical compositions of Ca-amphiboles (a, b) and Na-
amphiboles (c). The arrow indicates the change in chemical com-
position observed in the Komjáti samples (Fig. 3e).
Fig. 5. Al
diagram for Na-Ca- (triangles) and Ca-amphib-
oles from Komjáti-11 (squares and circles) and Szögliget-4 (dia-
monds). Note that actinolites have lower Al
, but relatively the
content compared to hornblendes.
Table 3: Representative chemical compositions of minerals from
Biotite is the dominant mafic mineral in the Bódvarákó gab-
bros and it occurs in the Szögliget rocks as well. X
from 0.45 to 0.65 while the Ti content is up to 0.73 p.f.u. in
some analyses (average Ti content is between 0.5 and 0.6).
There is no chemical difference between the various textural
occurrences of biotite. Chlorite is a common mineral in the
studied rocks. It has X
values between 0.58 to 0.65 in all
rock samples. Epidote has a restricted chemical composition
with the pistacite content ranging from 20 % to 30 %. Plagio-
clase was found as pure albite. Representative analyses of bi-
otite, chlorite and epidote are listed in Table 3.
Amphibole-bearing assemblages have often been proposed
as potential geothermobarometers, because the paragenesis
of amphibole-plagioclase is very common in metabasic
rocks, and is stable over a very wide P-T range (e.g. Spear
1993). There are several potential geothermobarometers used
METAMORPHIC EVOLUTION OF GABBROIC ROCKS 127
in metamorphic petrology involving various Ca-amphiboles
and Ca-bearing plagioclase (e.g. Plyusnina 1982 and Holland
& Blundy 1994). However, only a few can be applied to albi-
te-bearing metabasic rocks. Albite may be in equilibrium
with Ca-amphibole even at 600 °C at low pressures as shown
by Spear (1993).
In this study the empirically calibrated (Na,Ca)-amphib-
ole-albite-chlorite-epidote-quartz geothermobarometer of
Triboulet (1992) was used in the system SiO
O. It considers two equilibria with
tremolite-edenite and tremolite-(pargasite, hastingsite) end
members, respectively. The results of mineral chemical anal-
yses obtained from amphiboles and coexisting epidote and
chlorite give way to the calculation of two arrays of lnK
(distribution coefficience) isopleths. The calculation proce-
dure of lnK
values follows the scheme described by Tribou-
let (1992). The isopleths for these equilibria intersect at high
angles and define a P-T value for the end-member composi-
tions of amphibole in the above mentioned assemblage. Ad-
ditionally the geothermobarometer of Gerya et al. (1997) was
also used. It requires only the chemical compositions of am-
phiboles in P-T calculations using the isopleths of the Al and
the Si contents of amphiboles.
The P-T conditions for the earliest blueschist facies event is
poorly constrained, because the assemblage Na-amphibole +
epidote + albite + quartz is stable over a wide range in the P-T
field. Minimum pressure of 700800 MPa at temperatures
around 350500 °C were obtained using the experimental
work of Maruyama et al. (1986) for the blueschist-greenschist
transition. For actinolites from the Komjáti-11 samples we ob-
tained pressures of 400600 MPa from the Na
content of the
actinolites (0.40.7) which is an empirical geobarometer pro-
posed by Brown (1977), and temperatures between 350 and
400 °C with the same pressure range using the geothermoba-
rometer of Triboulet (1992). This is in good agreement with
the results of Horváth (1997). The Na
content of the meta-
morphic hornblende is between 0.4 and 0.7 for the Szögliget
and Komjáti amphiboles. For these assemblages the P-T con-
ditions are 400600 MPa and 500600 °C for Komjáti-11, and
500700 MPa and 550600 °C for the Szögliget-4 gabbros. In
the Szögliget samples there is only a trace for the earlier blue-
schist and greenschist facies event observed and better pre-
served in the Komjáti-11 gabbros. For the Bódvarákó samples
the P-T conditions are poorly constrained. The occurrence of
biotite-epidote assemblage replacing magmatic clinopyroxene
implies temperatures around 400450 °C at 400600 MPa
(Bucher & Frey 1994). In some samples small, green biotite
can be seen on large actinolite crystals as a newly formed
phase which confirms the results stated above. The results of
the thermobarometric calculations and the inferred P-T path
for the BVOC gabbros are given in Fig. 6.
The metamorphic evolutionary path and the petrological
features of the BVOC gabbros were determined using repre-
sentative samples from 3 boreholes from the Rudabánya
Mountains, NE Hungary. The obtained metamorphic petrolog-
ical results are partly in good agreement with the earlier state-
ments of Horváth (1997), and in some places amplify them.
The first part of the P-T path (Fig. 5) shows clockwise shape
and is a general feature of P-T paths from subduction zones
with a high-medium pressure low-temperature blueschist fa-
cies event followed by greenschist facies with nearly isother-
mal decompression. This fact is supported by the occurrence
of some Na-Ca-amphiboles, which formed after the Na-am-
phiboles, but before the greenschist facies overprint. The tem-
perature increase from greenschist facies to albite-epidote-am-
phibolite facies (according to Evans 1990), well documented
by the continous chemical changes in Ca-amphiboles (from
actinolite to magnesiohornblende), can be explained by two
solutions: 1 a separate metamorphic event caused by intru-
sion of a hot magmatic body, or 2 a thermal relaxation fol-
lowing subduction. There is no evidence for a major magmatic
event after subduction which could have caused contact meta-
morphism in this area, so the first solution is thought to be in-
appropriate. The second solution is heavily favoured by the
author, because various rates of uplift for different portions of
the downgoing slab even in the same subduction zone seem to
be a reasonable feature. This interpretation is supported by the
continuous change in amphibole chemistry from the Komjáti
samples and the microtextural observation of hornblende re-
placing actinolite in various samples. Similar changes in am-
phibole chemistry were reported by Dobmeier (1998) from the
western Alps, where actinolite was found in the cores of some
amphiboles which were replaced at the rims by hornblende. In
that case the temperature increase was accompanied by a pres-
sure increase as well, which was not observed in the BVOC.
Fig. 6. Inferred P-T path of metamorphosed gabbroic rocks from
the BVOC (broken arrow represents an alternative P-T path). A:
amphibolite facies, AEA: albite-epidote-amphibolite facies, EBS:
epidote-blueschist facies, GS: greenschist facies (facies bound-
aries after Evans 1990), Gln/Act: glaucophane-actinolite transi-
tion after Maruyama et al. (1986), Gln/Bar: glaucophane-bar-
roisite transition after Ernst (1979), Bio: biotite-in reaction after
Bucher & Frey (1994), Actinolite-hornblende transition after
The timing of the metamorphic events outlined above are
slightly controversial in the BVOC. Sporadic K/Ar measure-
ments (Árva-Sós et al. 1987) yield widely scattered ages be-
tween 270 and 110 Ma. The main concern with the K/Ar data
is that the mineral chemical compositions of the analyzed
phases were not checked before the measurements, and the
formation conditions of the minerals were not cleared (mag-
matic, metamorphic events or even weathering). The oldest
ages were obtained on amphiboles from the Szögliget Szö-4
borehole (256 ± 26 Ma) or on whole rock specimens (200225
Ma) from the Bódvarákó gabbros. Biotite K/Ar age from a sam-
ple from the Bódvarákó Br-4 borehole yields 233 ± 10 Ma, and
Ar/Ar data from the same sample shows 240 ± 2 Ma (Balogh,
pers. comm.). This age data provides evidence for an Late Per-
mian-Early Triassic metamorphic event in the BVOC, which
is in contradiction to the Middle Triassic opening of the Melia-
ta ocean proposed by various authors (e.g. Kovács et al. 1996
97 and Plaienka et al. 1998) and the Middle-Late Jurassic
subduction of the Meliata oceanic basin (Maluski et al. 1993;
Faryad & Henjes-Kunst 1997). Further isotope geochronologi-
cal data on minerals, the magmatic or metamorphic origin of
which is well constrained, are needed to solve this controver-
sy. The other major question is the exact timing of the imbri-
cation of the BVOC into the basal part of the Silica Nappe. It
is certain that this event took place after the complex meta-
morphic evolution of the BVOC, because the Silica Nappe is
not effected by regional metamorphic events (Árkai &
Kovács 1986). The author believes that the new metamor-
phic petrological data presented in this paper will help to
clarify some parts of the tectonic evolution of the North Hun-
garian area still in obscurity, even though that it raises more
questions about the affinity of the BVOC nowadays related
to the Meliata Unit.
The Alpine polyphase metamorphic evolution path of the
Bódva Valley Ophiolite Complex was reconstructed using
mineral paragenetic, mineral chemical and thermobarometric
results obtained on metagabbroic samples from boreholes in
the Rudabánya Mts., NE Hungary. The first recognizable,
blueschist facies event (min. 700800 MPa, 350500 °C)
was followed by nearly isothermal decompression to 400
600 MPa in the greenschist facies. The following metamor-
phic event was characterized by temperature increase up to
500600 °C in isobaric conditions. This means that the meta-
morphism reached even the albite-epidote-amphibolite facies
of Evans (1990). The P-T path outlined above can be best de-
scribed by a subduction to at least 25 km of crustal depth,
which was followed by an uplift without any significant
change in the temperature conditions. The late temperature in-
crease was caused by thermal relaxation following subduction.
Acknowledgements: This paper forms part of the PhD work
of the author performed in the Laboratory for Geochemical
Research, Hungarian Academy of Sciences. Prof. Péter Árkai
provided knowledge about metamorphic petrology and sup-
ported me throughout this study. Reviews and critical com-
ments by F. Koller (University of Vienna) and two anonymous
referees are greatfully acknowledged. Discussions with Dr.
S.W. Faryad (University of Koice) were constructive and im-
proved the presentation. The author is indebted to Mr. S. Józsa
(Department of Petrology and Geochemistry, Eötvös Universi-
ty, Budapest) for the sampling and to Dr. S. Kovács (Academ-
ic Research Group, Department of Geology, Eötvös Universi-
ty, Budapest) for his valuable advice. Thanks are due to V.
Varga for the whole rock analyses and Dr. K. Gál-Sólymos
(Department of Petrology and Geochemistry, Eötvös Universi-
ty, Budapest) for some of the electron microprobe analyses.
The field work and the sampling were supported by Grant No.
T 019431 given by the Hungarian Scientific Research Fund
(OTKA), Budapest to S. Kovács. The study received financial
help from the Grant No. T 022773 given by the Hungarian Sci-
entific Research Fund (OTKA), Budapest to P. Árkai.
Árkai P. & Kovács S. 1986: Diagenesis and regional metamorphism
of the Mesozoic of the Aggtelek-Rudabánya Mountains
(Northeast Hungary). Acta Geol. Hung. 29, 349373.
Árva-Sós E., Balogh K., Ravasz-Baranyai L. & Ravasz Cs. 1987: K-
Ar dates of Mesozoic igneous rocks in some areas of Hungary.
A. r. Hung. Geol. Inst. 1985, 295307 (in Hungarian with En-
Balla Z. 1982: Development of the Pannonian basin basement
through the Cretaceous-Cenozoic collision: a new synthesis.
Tectonophysics 88, 61102.
Bence A.E. & Albee A. 1968: Empirical correction factors for elec-
tron microanalysis of silicates. J. Geol. 76, 382403.
Brown E.H. 1977: The crossite content of Ca-amphibole as a guide
to pressure of metamorphism. J. Petrology 18, 5372.
Bucher K. & Frey M. 1994: Petrogenesis of metamorphic rocks.
Springer, Berlin, 1318.
Coleman R.G. 1977: Ophiolites. Springer, Berlin, 1229.
Csontos L., Nagymarosy A., Horváth F. & Kováè M. 1992: Tertiary
evolution of the Intra-Carpathian area: a model. Tectonophys-
ics 208, 221241.
Csontos L. 1995: Tertiary evolution of the Intra-Carpathian area: a
review. Acta Vulcanol. 7, 113.
Dal Piaz G.V., Martin S., Villa I.G., Gosso G. & Marschalko R.
1995: Late Jurassic blueschist facies pebbles from the Western
Carpathian orogenic wedge and palestructural implications for
Western Tethys evolution. Tectonophysics 14, 874885.
Dobmeier C. 1998: Variscan P-T deformation paths from the south-
western Aiguilles Rouges massif (external massif, western
Alps) and their tectonic implication for its tectonic evolution.
Geol. Rdsch. 87, 107123.
Dosztály L. & Józsa S. 1992: Geochronological evaluation of Meso-
zoic formations of Darnó Hill at Recsk on the basis of radiolar-
ias and K-Ar data. Acta Geol. Hung. 35, 371394.
Ernst W.G. 1979: Coexisting sodic and calcic amphiboles from
high-pressure metamorphic belts and the stability of barroisitic
amphibole. Mineral. Mag. 43, 269278.
Evans B.W. 1990: Phase relations of epidote-blueschists. Lithos
Faryad S.W. 1995: Phase petrology and P-T conditions of mafic
blueschists from the Meliata unit, Western Carpathians, Slova-
kia. J. Metamorphic Geol. 13, 701714.
Faryad S.W. 1997: Petrology and geologic significance of high-
pressure metamorphic rocks occurring as pebbles in the Creta-
ceous conglomerates of the Klippen Belt (West Carpathians,
METAMORPHIC EVOLUTION OF GABBROIC ROCKS 129
Slovakia). Eur. J. Mineralogy 9, 547562.
Faryad S.W. & Henjes-Kunst F. 1997: Petrological and K-Ar and
Ar age constraints for the tectonothermal evolution of
the high-pressure Meliata Unit, Western Carpathians (Slova-
kia). Tectonophysics 280, 141156.
Gerya T.V., Perchuk L.L., Triboulet C., Audren C. & Sezko A.I.
1997: Petrology of the Tumanshet zonal metamorphic com-
plex, Eastern Sayan. Petrology 5, 503533.
Harangi Sz., Szabó Cs., Józsa S., Szoldán Zs., Árva-Sós E., Balla M.
& Kubovics I. 1996: Mesozoic igneous suites in Hungary: Im-
plications for genesis and tectonic setting in the northwestern
part of Tethys. Int. Geol. Rev. 38, 336360.
Holland T.J.B. & Blundy J. 1994: Non-ideal interactions in calcic
amphiboles and their bearing on amphibole-plagioclase ther-
mometry. Contr. Mineral. Petrology 16, 433447.
Horváth P. 1997: High-pressure metamorphism and P-T path of the
metabasic rocks in the borehole Komjáti-11, Bódva Valley
area, NE Hungary. Acta Mineral. Petrogr. 38, 151163.
Kamenický J. 1957: Triassic serpentinites, diabases and glau-
cophanic rocks from Spisko-Gemerské Rudohorie. Geol.
Práce, Zo. 45, 157 (in Slovak).
Kovács S., Szederkényi T., Árkai P., Buda Gy., Lelkes-Felvári Gy. &
Nagymarosy A. 199697: Explanation to the terrane map of
Hungary. Ann. Géol. pays Hellén. 37, 271330.
Leake B.E., Woolley A.R., Arps C.E.S., Birch W.D., Gilbert M.C.,
Grice J.D., Hawthorne F.C., Kato A., Kisch H.J., Krivovichev
V.G., Linthout K., Laird J., Mandarino J., Maresch W.V., Nick-
el E.H., Rock N.M.S., Schumacher J.C., Smith D.C., Stephen-
son N.C.N., Ungaretti L., Whitaker E.J.W. & YouzhiI G. 1997:
Nomenclature of Amphiboles: Report of the subcommittee on
Amphiboles of the International Mineralogical Association
Commission on New Minerals and Mineral Names. Mineral.
Mag. 61, 295321.
Mahe¾ M. 1986: Geological structure of Czechoslovak Carpathians.
VEDA, Bratislava, 1503 (in Slovak).
Maluski H., Rajlich P. & Matte Ph. 1993:
Ar dating of the In-
ner Carpathian Variscan Basement and Alpine mylonitic over-
printing. Tectonophysics 223, 313337.
Maruyama S., Cho M. & Liou J.G. 1986: Experimental investiga-
tions of blueschist-greenschist transition equilibria: Pressure
dependence of Al
contents in sodic amphiboles a new
geobarometer. Geol. Soc. Amer. Mem. 164, 116.
Mello J., Reichwalder P. & Vozárová A. 1998: Bôrka Nappe: high-
pressure relic from the subduction-accretion prism of the Meli-
ata ocean (Inner Western Carpathians, Slovakia). Slovak Geol.
Mag. 4, 261274.
Mével C. 1988: Metamorphism in oceanic layer 3, Gorringe Bank,
Eastern Atlantic. Contr. Mineral. Petrology 100, 496509.
Mock R. 1978: Some new knowledge about southern part of the
West Carpathians. In: Vozár J. (Ed.): Paleogeographic devel-
opment of the West Carpathians. Geol. Inst. Dionýz túr, Brat-
Mock R., Sýkora M., Aubrecht R., Ovoldová L., Kronome B.,
Reichwalder P. & Jablonský J. 1998: Petrology and stratigra-
phy of the Meliaticum near the Meliata and Jaklovce villages,
Slovakia. Slovak Geol. Mag. 4, 223260.
Nagy G. 1984: Computer programs for quantitative electron micro-
probe analysis developed for geological applications. EU-
REM84: Proc. 8th Eur. Congr. on Electron Microscopy,
Neubauer F., Fritz H., Boja A.V., Janák M., Puti M. & Reich-
walder P. 1992: Kinematics of the blueschist-bearing nappe:
The Meliata Unit of the Western Carpathians. Terra Abstr.,
Terra Nova 4, 77.
Plaienka D., Grecula P., Puti M., Kováè M. & Hovorka D. 1997:
Evolution and structure of the Western Carpathians: an over-
view. In: Grecula P., Hovorka D. & Puti M. (Eds.): Geological
evolution of the Western Carpathians. Miner. SlovacaMono-
Plyusnina L.P. 1982: Geothermometry and geobarometry of plagio-
clase-hornblende bearing assemblages. Contr. Mineral. Petrol-
ogy 80, 140146.
Réti Zs. 1985: Triassic ophiolite fragments in an evaporitic me-
lange, Northern Hungary. Ofioliti 10, 411422.
Robinson P., Spear F.S., Schumacher J.C., Laird J., Klein C.,
Evans B.W. & Doolan B.L. 1982: Phase relations of metamor-
phic amphiboles: natural occurrence and theory. In: Veblen
D.R. & Ribbe P.H. (Eds.): Amphiboles: Petrology and Experi-
mental Phase relations, Rewiews in Mineralogy 9B. Miner.
Soc. Amer. 127.
Sadek Ghabrial D., Árkai P. & Nagy G. 1996: Alpine polyphase
metamorphism of the ophiolitic Szarvaskõ complex, Bükk
Mountains, Hungary. Acta Mineral. Petrogr. 35, 99128.
Spear F.S. 1993: Metamorphic phase equlibria and pressure-temper-
ature-time paths. Miner. Soc. Amer., 1799.
Triboulet C. 1992: The (Na-Ca) amphibole-albite-chlorite-epidote-
quartz geothermobarometer in the system S-A-F-M-C-N-H
An empirical calibration. J. Metamorphic Geol. 10, 545556.
Vitális I. 1909: Geologic outline of the Bódva-Rónaköz region.A. r.
Hung. Geol. Inst. 1907, 4558 (in Hungarian).