Correlation of metabasic rocks from metamorphic soles of the Dinaridic and the Western Vardar zone ophiolites ( Serbia ) : three contrasting pressure-temperature-time paths

The field, petrological-mineralogical, geochemical and geochronological data of the metamorphic sole rocks recorded beneath the Fruška Gora, Povlen (Tejići), Stolovi and Banjska ophiolites in the Western Vardar Zone (WVZ) and beneath the Zlatibor, Bistrica, Sjenički Ozren and Brezovica ophiolites in the Dinaridic ophiolite belt (DOB) in Serbia are compared. The focus has been made on metabasic rocks formed in contact with the oceanic crust members: cumulate gabbro and basalts of SSZ-type with E-MORB and OIB-signature and more evolved tholeiitic basalts of MOR-affinity. Amphibole, the major phase formed from the mafic sole components, depending on pressure-temperature conditions exhibits compositional variations. According to mineral assemblages, estimated P–T conditions and ages, the potential P–T paths are given: high pressure – low temperature blueschist facies assemblage (7–9 kbar and ~400°C and <300–350°C and 4–8 kbar), recorded only in the metamorphic sole at the Fruška Gora (WVZ); high pressure – high temperature amphibolite to granulite facies (8–10 kbar and >700–850°C), recorded in both domains, the WVZ (Banjska) and the DOB (Bistrica, Sjenički Ozren, Brezovica) and medium pressure – medium temperature amphibolite facies assemblages (~3.5–7 kbar and >350–650°C) recognized in the WZV (Tejići, Devovići) and the DOB (Zlatibor). The peak metamorphic conditions point to depths of the oceanic lithosphere detachment and its initial cooling at 10–30 km, but the ages and tectonic setting of ophiolites remain poorly constrained. The summarized data may be used as an important key in geodynamic evolution of the Mesozoic Tethyan ophiolites.


Introduction
Numerous ultramafic sequences worldwide comprise high to medium and low grade metamorphic sole rocks formed during the overthrusting of hot lithospheric fragments in intra-oceanic settings or within orogenic belts.Their presence is the clue in clarifying the nature of emplacement processes during intraoceanic subduction and post-obduction tectonic events.The creation of metamorphic sole is among the earliest event at the end of magmatic construction when tectonic processes take part in ophiolite evolution instead of igneous (JAMIESON 1986;GARFUNKEL 2006).The size of metamorphic sole, its age, thermal evolution and peak metamorphic condition can enable a better insight into the age and thermal properties of the ophiolite sequences during their emplacement.Moreover, it is of key importance in proceedings related to the ocean-realm evolution.
Well to slightly evolved metamorphic sole rocks occur beneath most of the Jurassic Tethyan-type ophiolites in the Western Vardar Zone (WVZ) and in the Dinaridic belt (DOB) in Serbia.The best preserved metamorphic sole rocks crop out within the DOB in association with the Zlatibor, Bistrica, Sjenički Ozren and the Brezovica ophiolites, and in the WVZ in association with the Fruška Gora (FG), Maljen, Povlen (Tejići), Stolovi and the Banjska ophiolites (Fig. 1).The majority of them comprise approximately 100-250 m thick assemblage of metasediments associated with high to medium grade metabasites.
The goal of this contribution is to make correlation sole amphibolites evolved beneath two ophiolite belts i.e. the DOB and the WVZ, on the basis of available geological, geochemical and geochronological data contributed with some new data related to the garnet amphibolites of Bistrica.

Geological setting
The closure of the Tethyan oceanic realm in the Central Balkan Peninsula since Early Jurassic time was followed by subduction of the oceanic lithosphere along convergent continental margins or within suprasubduction oceanic environments (KARAMATA 2006;ROBERTSON et al. 2009, and references there in).
The NW-SE trending DOB is bordered by the Drina-Ivanjica Unit to the east and the WVZ to the northeast and extends to the Dinaridic Carbonate platform to the west and related units to the southwest (Fig. 1).Southwards it enters Metohija Depression and continues to Albania and Greece.The dismembered ultramafic bodies are interpreted as fragments of subcontinental mantle or as supra-subduction (back arc) type.The former is mostly lherzolitic (± garnet) and the latter is lherzolitic (± spinel)-harzburgitic in composition (BAZYLEV et al. 2006a(BAZYLEV et al. , 2009)).The metamorphic sole at their base comprises high to medium grade amphibolites (rarely granulite) of 168 ± 1 Ma age (LANPHERE et al. 1975).

Material and Methods
Samples of amphibolites (with ± garnet) from Bistrica were investigated under the microscope and afterwards the freshest samples were selected for further study.Morphologies and chemical composition of mineral phases were identified using a JEOL JSM-6610LV Scanning Electron Microscope that was connected to an X-Max large Area Analytical Silicon drift in the Faculty of Mining and Geology in Belgrade.Quantitative mineral analyses were performed under high vacuum conditions, acceleration voltages 20 kV, step sequence 10 mm and external set of standards characteristic for each element.Mineral abbreviation used in text is done after KRETZ (1983).

The metamorphic sole rocks beneath the WVZ ultramafics
Mt. Fruška Gora.The metamorphic sole rocks crop out on the southern slope of the mountain inside the mélange composed of large blocks and fragments of sedimentary, igneous and volcaniclastic rocks set in a very low to low grade metamorphosed clayey-sandy matrix.Their age ranges from Triassic to Jurassic--Cretaceous (pre-Maastrichtian).Elongated dismembered ultramafic bodies, spinel harzburgitic (rarely lherzolitic) in composition, form the southern slopes of the mountain in the area Bešenovo-Jazak-Grgurevac.The smaller bodies of serpentinized harzburgite and dunite crop out at the northern slopes in the area between Beočin and Sremski Karlovci, also.Blocks and fragments of terrigenous and volcaniclastic rocks as well as basalts and rarely carbonate rocks from mélange were exposed to various metamorphic grade and transformed into phyllites, sericite-chlorite schists, green schists, metabasalts, metadolerite, calcschists, rarely marbles and blueschists (ALEKSIĆ & ČUČULIĆ-TRIFUNOVIĆ 1972;MILOVANOVIĆ et al. 1995;KORIKOVSKY & KARAMATA 2011).The actual size of these blocks cannot be estimated due to insufficient exposure of ultramafics and mélange.
Subduction related high pressure-low temperature metamorphic sole rocks were determined as crossiteschists by MILOVANOVIĆ et al. (1995) and later as glaucophane-riebeckite-pumpellyite-actinolite-epidote schists by KORIKOVSKY & KARAMATA (2011).They occur as large blocks on the northeastern slope of Mt. (stream Selište, ~2 km northern of the town Sremski Karlovci,) and on the western slope within the Upper Jurassic-Lower Cretaceous olistostrome mélange (KORIKOVSKY & KARAMATA 2011) as well as pebbles within the Maastrichtian basal conglomerates (e.g.Čitluk stream).The amphibole in the first occurrence is classified as crossite according to the classification of LEAKE et al. (1978).MILOVANOVIĆ et al. (1995) considered the mineral assemblage epidote + sodic amphibole + quartz to be formed under the epidote-blueschist subfacies or high-T epidote bearing segment of blueschist facies (see EVANS 1990) i.e. at the temperature of approximately 400°C and pressure 7-9 kbar.This pressure corresponds to metamorphism at a depth of about 30 km.
This study reveals the subduction of the oceanic crust of the Vardar Ocean during the Early Cretaceous time (Barremian-Aptian; 123 ± 5 Ma), probably beneath the continental crust situated northeast, which argues the existence of an eastward dipping subduction zone.The second occurrence contains zonal Na-amphibole of the glaucophane-riebeckite series, actinolite, pumpellyite, epidote, chlorite, and rarely quartz.KORIKOV-SKY & KARAMATA (2011) suggested that the mélange rocks along with the high-Ti subalkaline basalts and associated K-rich quartz-mica arkoses were buried to depths of 14-29 km by cold subduction.The same authors assumed that at pressure of 4-8 kbar and temperature below 340-350°C the mentioned rocks were transformed into glaucophane (riebeckite)-pumpellyite-actinolite-epidote-chlorite metasandstones and phyllites with high-pressure Mg-Si phengite.
Mt. Povlen (Tejići).The metamorphic sole rocks occur within an olistostrome mélange as fragments or large blocks beneath the ophiolite slab, which is exposed as a narrow, approximately 200 m wide and 800 m long zone.The ophiolite sequence, mainly composed of harzburgite (minor lherzolite) with typical tectonite fabric, gabbro, diabase and pillow-basalt associated with volcanic breccias and tuffaceous rocks, is tectonically emplaced to its present position during the late Upper Jurassic.
The metamorphic sole comprises greenschist to amphibolite facies mineral assemblages created by metamorphism of basic igneous rocks and their volcaniclastics along with sandy-silty (argillaceous) sediments.The low-grade metamorphic rocks are various greenschists, while higher-grade metamorphic rocks (garnet bearing amphibolite, amphibolite sensu stricto and epidote-bearing amphibolite) are exposed at the base of the ultramafic sequence (mostly harzburgite).Amphiboles within higher-grade metamorphic rocks are tschermakite, rarely magnesio-hornblende; primary plagioclase is almost completely replaced by epidote and prehnite whereas garnet porphyroblasts are almandine-rich.Biotite, chlorite, and actinolite are formed at the expense of amphibole due to retrograde metamorphic conditions.Amphibolitic rocks are followed by large blocks or fragments of augen gneisses and garnet mica schists metamorphosed under P-T condition of 435-550°C and 4.5 ± 0.5 kbar (SREĆKO-VIĆ-BATOĆANIN & VASKOVIĆ 2000).The P-T conditions of amphibolites estimated for a Grt-Hbl pair using the method of GRAHAM & POWELL (1984), PO-WELL & HOLLAND (1985) and PERCHUK & LAVRENTE-VA (1985) reveal a temperature range of 630 to 680°C and pressure of 6 ± 1.5 kbar (SREĆKOVIĆ-BATOĆANIN et al. 2002).The K-Ar age of sole rocks of 160-150 Ma (Tithonian/Callovian) reveals the time when protoliths were overthrusted by the hot ultramafic slab, and the beginning of the closure of the ocean basin (SREĆKOVIĆ-BATOĆANIN et al. 2002, 2010).The presence of metaclastic rocks assembled with metabasic rocks reveals the site of emplacement close to a major landmass.The presence of amygdales in pillow basalts and lack of deep water sediments additionally confirm this statement.
Devovići (Ušće).On the southwestern slope of the large Ibar ultramafic mass (Massif Radočelo), 5 km distant from Ušće, the metamorphic sole appears in a narrow tectonic zone (0.3-0.4 km wide and ~1 km long) within the serpentinized spinel harzburgite.A dense alternation of various low and medium to high grade metamorphic rocks derived from rocks of the diabase-chert formation were identified (POPEVIĆ 1973).Based on mineral assemblages in amphibolites next to ultramafics a temperature of about 600°C is suggested.The whole sequence subsequently underwent retrograde metamorphism.Data related to whole rock-and mineral chemistry are lacking.
Banjska.The Banjska Massif (20 × 8 km) is a relatively large body composed of clinopyroxene-poor spinel lherzolite (BAZYLEV et al. 2009).The metamorphic sole is developed as a zone of almost 20 m wide and 2 km long.It comprises high grade metamorphic rocks: clinopyroxene and/or hornblende (± clinozoisite) amphibolites with thin bands of garnet-cordieritesillimanite gneiss (MAJER et al. 1979;KORIKOVSKY et al. 2000a).Most of them underwent retrograde metamorphism and Fe-Mg-Ca metasomatic processes (KORIKOVSKY et al. 2000a).The high-temperature amphibole from amphibolites with up to 1.9% TiO 2 is classified as pargasite-tschermakite-hastingsite.Due to retrograde greenschist facies overprint it is mostly replaced by actinolite ± epidote.Replacements by chlorite ± sericite in garnet and cordierite, and plagioclase by saussurite or prehnite and pumpellyite have been noted.According to the garnet-biotite and garnet-cordierite thermometer of PERCHUCK (1989) and garnet-cordierite-sillimanite-quartz barometer of ARA-NOVICH & PODLESSKII (1989) gneisses formed within the temperature range of 650°C to 760-780°C at pressure of 6.7-6.9 kbar (KORIKOVSKY et al. 2000a).Pressure estimates are compatible with the arrangement of jadeite isopleths in clinopyroxene in the clinopyroxene-plagioclase-quartz assemblage after HOLLAND (1980) indicating the depth of the initial cooling and the onset of tectonic stabilization of the ultramafic mass at 24-25 km.
Troglav.The Troglav Massif mainly consists of spinel harzburgite.Dunite and spinel lherzolite are subordinated.POPEVIĆ (1978) assumed that the Stolovi (east of the Troglav) and the Troglav represent parts of one large massif separated by the Ibar River valley.The metamorphic sole at its base has not yet been studied.
Rogozna.Metamorphic sole at the Rogozna Massif formed from basic igneous and sedimentary rocks mostly comprises schistose amphibolites and greenschists.Rare occurrences of mica schists and marbles are also noted.Rocks are highly hydrothermally altered during the Oligocene Pb-Zn-Ag mineralization processes.Amphibolite samples collected near the Crnac Pb-Zn-Ag mine and along the road section Jošanička creek -Leposavić consist of hornblende (replaced by secondary chlorite and fibrous actinolite) and plagioclase, partly replaced by epidote and preh-nite (PALINKAŠ et al. 2008).The Ar-Ar ages determined on amphibole and actinolite vary from 168.8 ± 3.9 Ma to 178.3 ± 6.7 Ma; the age of the hydrothermally altered amphibolite is 150.4 ± 10.2 Ma.This age implies the onset of intra-oceanic subduction-obduction processes (Lower to Middle Jurrasic i.e.Toarcian to Bajocian time) synchronous with the formation of Dinaridic and Albanian metamorphic soles (PALINKAŠ et al., loc.cit.).
An inverted metamorphic sole (150-200 m thick), mostly composed of metabasic rocks with subordinated gneisses and phyllites is exposed beneath the central part of the Zlatibor massif along the road section Čajetina-Rudine.Three temperature zones are recognized within it: I. hornblende-clinopyroxene-plagioclase, II.hornblende-chlorite-albite and III.actinolite-prehnite-pumpellyite (KORIKOVSKY et al. 2000b).Amphibole from metabasic rocks is tschermakite.According to the Grt-Pl thermometer of BLUNDY & HOLLAND (1990) the temperature range of 550-650°C is calculated for the first zone.In the second zone the temperature is estimated at 400-500°C based on the Grt-Phn thermometer of GREEN & HELLMAN (1982).For the third zone a temperature range of 300-350°C is assumed according to the petrogenetic grid for metabasic rocks within an accepted pressure of 3 to 3.5 kbar (after LIOU et al. 1987).The roughly estimated pressure according to Jd-concentration in clinopyroxene (after HOLLAND, 1980) is 3-3.5 kbar, too.It seems that this massif was tectonically stabilized and started to cool at much shallower depths (12-13 km) than the other Serbian ultramafic massifs (KOR-KOVSKY et al. 2000b).
Sjenički Ozren.This ultramafic massif (10 × 15 km) consists of spinel and plagioclase lherzolites in a nearly equal amount.The former comprises dunite, depleted spinel lherzolite and harzburgite; while within the latter a small gabbro bodies and thin veins occur (PO-PEVIĆ 1985;POPEVIĆ et al. 1996b;BAZYLEV et al. 2006b).The metamorphic sole up to 200 m thick is exposed in a few localities at the mountain's NNE and SE margin: Krajinovići, Brdo, Zmajevac, Gonje and Marina Ravan.Its contact with the ultramafics is tectonic and often followed by blastomylonitization, which led to the formation of low temperature minerals at the expense of primary minerals.In the contact aureole four zones were distinguished (POPEVIĆ, 1985;POPEVIĆ et al. 1996b;KORIKOVSKY et al. 1996).The fourth zone, next to the contact, is made up of garnet-clinopyroxene amphibolites, while further amphibolites sensu stricto, gabbro-amphibolites and greenschists occur.According to Grt-Cpx geothermometer of AI (1994) amphibolites of the fourth zone formed in the temperature range of 750-830°C at pressure of about 5-6 kbar, corresponding to depths from 18 to 22 km (KORIKOVSKY et al. 1996).The peak metamorphic conditions imply the emplacement of the Sjenički Ozren ultramafic mass in a solid-subsolid state (over 1000°C).

Discussion
The formation of metamorphic soles is directly related to the emplacement of ultramafics implying the overthrusting of hot oceanic lithosphere within intra-oceanic setting or orogenic belts.According to tectonic setting, relationships with adjacent geological units and main tectonic structures, a few models of sole formation have been recently proposed.Some of them for example are low-angle shearing and overthrusting of oceanic lithosphere in an intra-oceanic environment, overlapping mid-ocean ridge crest, obduction caused by roll-back subduction, transformactivated obduction and shearing superimpose onto an older contact aureole (e.g.KARAMATA 1968KARAMATA , 1988KARAMATA , 2006;;KARAMATA & LOVRIĆ 1978;WOODCOCK & RO-BERTSON 1977;ROBERTSON & KARAMATA 1994;SPRAY 1984;ROBERTSON & DIXON 1985;JONES et al. 1991;PARLAK & DELALOYE 1999;ROBERTSON & SHALLO 2000;WAKABAYASHI & DILEK, 2000;ROBERTSON et al. 2009).The field, petrological-mineralogical, geochemical and geochronological (K-Ar, Ar-Ar, U-Pb, Sm-Nd) studies of the evolved metamorphic sole rocks reveal valuable data on thermal conditions during intra-oceanic thrusting or during obduction onto passive continental margin.
Comparison of metamorphic sole rocks recorded in the WVZ and the DOB in Serbia offer data on the nature and emplacement of Mesozoic Tethyan ophiolites.However, each metamorphic sole as noted above relies on its own tectonic, structural and metamorphic characteristics.The focus of our comparison has been made only on mafic precursors from which various types of high to medium grade metamorphic rocks were formed.

Comparison of petrography and mineral composition
It can be recognized from the previous section that different species of amphibole are the major phase formed at the expense of the mafic sole components (Fig. 3).Depending on the conditions attained during the ophiolite emplacement a variety of metamorphic rocks were formed close to the contact (e.g.garnet and amphibole bearing granulite, clinopyroxene ± garnet amphibolite, corundum-bearing amphibolite, amphibolite sensu stricto and blueschist).Further from the contact a number of medium to low grade metabasic rocks have formed.Foliation within the last is defined by an arrangement of idiomorphic to sub-idiomorphic amphiboles.At the contact with ultramafics some amphibolite outcrops exhibit an alternation of amphiboleand plagioclase-rich bands (e.g.Tejići, Zlatibor, Bistrica, Brezovica).Generally, grain size ranges from 1-3 mm, although it can be below 0.5 mm.According to the available data the amphibole chemistry shows compositional variations with increasing temperature and pressure, ranging from actinolite to magnesiohornblende, tschermakite to edenite and magnesiohastingsite (Fig. 3), following the classification of LEAKE et al. (1997).Exceptions are blueschists from Mt. Fruška Gora -there amphibole corresponds to ferroglaucophane and magnesioriebeckite or to zonal Na-amphibole (glaucophane-riebeckite formed at the expense of older riebeckite) , and corundum amphibolites from Bistrica where amphibole is edenite to magnesio-hastingsite and pargasite in (Fig. 3).The individual amphibole grains are commonly compositionally homogeneous.
In the Fruška Gora area the replacement of riebeckite by glaucophane is characterized by an increase in Al, Mg, and Mg/(Mg + Fe 2+ ) ratio due to partial reduction of Fe 2+ through the prograde reaction Rbk + Chl + Ab→ Gln + O 2 .According to their composition the Na-amphiboles from those blueschists belong to a single genetic group (KORIKOVSKY & KARAMATA 2011).
The increase of Fe 3+ values and decrease in Al tot in some zoned amphiboles from the Tejići, Mt.Zlatibor, and Brezovica amphibolites could be related to changes in fO 2 (see SPEAR 1981) during metamorphism.However, the Fe 3+ content should be taken with caution due to limitation of EPMA to measure Fe 3+ (see DROOP 1987).The appearance of amphibole within the peripheral parts of the symplectite coronas (cpx + pl) evolved around garnets is noted for the first time in the Bistrica garnet amphibolites (Fig. 4).It is probably related to increase of total Fe content along with decrease of silica as can be seen from the data obtained from the spectrum 3 (Fig. 5).The chemistry of analyzed amphiboles (Table 1) coincides with the data of CHIARI et al. (2011): the Si content ranges between 6.52 and 6.72 apfu and Mg/(Mg+Fe 2+ ) ratio ranges from 0.782 to 0.793.It must be stressed out that the analyzed amphiboles are compositionally homogenous.The chemistry of amphiboles from the Bistrica garnet amphibolite, presented by MILOVANOVIĆ  (1988), deviates from new obtained data.Only one amphibole has homogenous tschermakitic composition, while the others correspond to magnesio-hastingsite and are characterized by lower Si content per formula unit (6.05-6.14)and higher Al VI (1.88-1.95apfu), Ti (0.24-0.27 apfu), and Na A (0.33-0.80 apfu) relative to the previously mentioned ones (Fig. 3).The amphibole grains from the garnet granulitic amphibolites of CHIARI et al. (2011) show identical Ti per formula unit (0.22-0.27).The garnet bearing amphibolites have lower Ti concentrations (0.10-0.13 apfu) that correspond to upper amphibolite to lower granulite facies conditions.Amphiboles from the studied amphibolite sensu stricto lack Ti as well as some from garnet clinopyroxene amphibolites of MILOVANOVIĆ (1988).Due to lack of available published data it is not possible to get a real insight into the Bistrica amphibole chemistry.However, an overall impression is that the com-positional changes in amphibole are controlled by temperature while the relatively high Al IV /Al VI ratio implies on moderate increase of pressure during metamorphism.
The occurrence of garnet in amphibolites is confined to the upper sections of the metamorphic soles in both ophiolite belts, with the exceptions of garnetfree amphibolites from the metamorphic soles of Rogozna, Devovići, Zlatibor, and Fruška Gora Mt.
The composition of garnet, its distribution and appearance in amphibolites is generally controlled by protolith bulk composition (i.e.Ca content) and by metamorphic conditions.The syn-kinematic and mostly cracked garnet porphyroblasts (<0.5 cm to 1-2 cm across) are commonly assembled with amphibole and often next to plagioclase accumulations or bands (Fig. 4).The appearance of the thin symplectite reaction rim (kelyphitic) in the Bistrica amphibolite taken on the right side of the road section, just behind the tunnel is reported for the first time (Figs.2, 4, 5).The garnets from Tejići and Bistrica show variable composition ranging between Alm 50.5-54.3Pyr 18.1-23.3Grs 9.2-15 Sps 10.4-12.1 in Tejići to Alm 31.5-50Pyr 21.5-50.7 Grs 15.4-24 Sps 0.9-5 in Bistrica (Table 1).The data for garnet chemistry in sole rocks of Sjenički, Ozren and Brezovica are lacking.According to KORIKOVSKY et al. (1996) and KARAMATA et al. (2000) it is almandine, rich in pyrope component (up to >40 %).All analyzed garnet grains from Tejići are weakly zoned (rims are slightly poorer in pyrope component, 2-4 %) and occasionally occur as inclusions in amphibole.In the Bistrica amphibolites two types of garnet can be recognized: homogenous i.e. unzoned (MILOVANOVIĆ 1988;CHIARI et al. 2011), reflecting the compositional equilibration, and zonal with notable increase of pyrope and decrease of almandine and grossularite components from core to rim (FED' KIN et al. 1996).The amphibole, clinopyroxene, and plagioclase are found as inclusions in the Bistrica garnets.The observed symplectite coronas around the Bistrica garnets consist of very tiny clinopyroxene, albite and amphibole grains (Fig. 5).The mineral relationships suggest that the garnet mostly grew at the expense of these minerals (higher contents of grossularite).
These differences are probably in close relation with the protolith composition and proximity of the contact zone as can be confirmed by the ratio Al IV /Al VI .This ratio reflects moderate recrystallization of primary clinopyroxene grains within the granulite facies and resulted in Al VI enrichment, i.e.Tschermak component (Fig. 6b).The Jadeite component varies between 9.57 and 8.88 % in average in clinopyroxenes from garnet amphibolites studied by MILOVANOVIĆ (1988).Similar values are found in clinopyroxenes from garnet bearing granulitic amphibolite (9.96 %) while a lower value (6.43 %) is reported by CHIARI et al. (2011).MILOVANOVIĆ (1988) has reported also matrix metamorphic clinopyroxene with much lower Al 2 O 3 (0.11 wt.%).It should be emphasized that differences in clinopyroxene composition within the Bistrica metamorphic sole could be the result of nonsystematic sampling and use of different analytical techniques.The chemistry of clinopyroxene (associated with garnet) from the Sjenički Ozren amphibolites is similar to the above mentioned -rich in the Tschermak component (i.e.alumina).However, the Al 2 O 3 content is higher ranging from 5.8-6.0 wt.% and contain up to 1.3 wt.% Na 2 O (KORIKOVSKY et al. 1996).The clinopyroxene in the Banjska amphibolite is poorer in Al 2 O 3 (1.7-2.1 wt.%) and richer in Jadeite component (6-7 %).The clinopyroxenes in the Brezovica amphibolites are compositionally homogeneous and correspond to high temperature augite with < 8-10 % of Jadeite component (KARAMATA et al. 2000).The data of clinopyroxene chemistry for Sjenički Ozren, Banjska, Zlatibor, and Brezovica are not published.
The clinopyroxene is generally associated with plagioclase, amphibole and garnet at the immediate contact with ultramafics and are absent from amphibolite sensu stricto.Therefore, its presence and distribution is a function of bulk rock chemistry and particularly of metamorphic grade.The presence of clinopyroxene in garnet-free assemblages of Zlatibor and Bistrica is probably controlled by protolith Ca abundance.Plagioclase from amphibolites is mostly altered and replaced by prehnite or saussurite (Fig. 4).Albite (0-2 mol.%An), a common constituent of the Tejići garnet amphibolites, is probably formed as a low temperature retrograde phase.Rare unaltered plagioclase found in the Bistrica garnet amphibolite and amphibolite sensu stricto ranges in composition from 58.5-60.2mol.%An (Fig. 4).MILOVANOVIĆ (1998) reported almost pure anorthite in garnet pyroxene amphibolites, which has been recently classified as garnet bearing mafic granulites (MILOVANOVIĆ et al. 2004).FED' KIN et al. (1996) found that plagioclase enclosed in garnet has a composition of 30-33 mol.%An while matrix plagioclase is anorthite poor (An 3-4 mol.%) in the garnet clinopyroxene amphibolites.The composition of the plagioclase from the Zlatibor garnet-free amphibolite is 45-50 mol.%An in the contact zone, and 12-15 mol.%An in the mid zone.The plagioclase of the Sjenički Ozren clinopyroxene amphibolite ranges in composition from 50-80 mol.%An (KORIKOVSKY et al. 1996).Further from the contact plagioclase is strongly zoned and poorer in An (15-25 mol.%).Generally, in the majority of metabasic rocks occurred further from the contact, the plagioclase have <10-30 mol.%An what enables the determination of P-T conditions.

Correlation of P-T conditions and age of metamorphism
The P-T conditions during metamorphic events are closely related to the thermal properties of the ophiolite sequences and to the rigidity of protoliths.The pressure is directly proportional to the depth.There-  fore various pressures can indicate various depths of detachment of the oceanic lithosphere as well as the depth of initial cooling.A gradual increase of P-T conditions with advancing movement of the ophiolite slab was recorded in some minerals through changes in their chemistry (e.g.Tejići, Bistrica, Fruška Gora).WAKABAYASHI & DILEK (2000) assumed considerable thinning of ophiolites after the sole formation, in cases when the estimated depths greatly exceed the thickness of ophiolites.
Based on P-T estimates for mineral assemblages in metabasic rocks of the WVZ and the DOB three types of metabasic soles can be distinguished (Fig. 7a, Table 2, 3): a) high pressure -low temperature blueschist facies assemblage, only recorded in the metamorphic sole at the Fruška Gora (WVZ).A temperature of approximately < 300-350°C and ~400°C and pressure of 4-8 kbar and 7-9 kbar respectively, corresponding to depths of about 14-29 km and 30 km, are estimated.These estimations are based on the petrogenetic grid for low-temperature metabasic rocks of moderate and high pressures of LIOU et al. (1987) for the glaucophane-riebeckite + pumpellyite assemblage.This assemblage is controlled by the reactions: NAKAJIMA et al. 1977) and by the stability field of natural glaucophane (MARESH 1977), which is in the upper limit range of 6-9 kbar and 400-450°C.The stability field for Na-amphibole is well constrained at pressure range of 5-9 kbar for the temperature range of 300-600°C (e. g.HOLLAND & POWELL 1988;HOL-LAND 1988;HOFFMAN 1972;MARUYAMA et al. 1986;BROWN 1974BROWN , 1977;;BROWN & FORBES, 1986).Generally, in this stability field the composition of Na-amphibole is pressure dependent.Accordingly, the estimation of MILOVANOVIĆ et al. (1995) for the assemblage ferroglaucophane (former crossite) + phengite + epidote can be considered realistic.Crossite is pressure dependent and very useful as it divides low-P riebeckite from high-P ferroglaucophane.Although the term crossite is not used anymore for the amphibole nomenclature of LEAKE et al. (1997) it was used due to its above described nature.
The K-Ar age of 123 ± 5 Ma for the blueschist implies the Early Cretaceous subduction of the oceanic crust beneath the northeastern continental crust (MI-LOVANOVIĆ et al. 1995).
b) high pressure -high temperature granulite to amphibolite facies characterize the metamorphic soles in both, the WVZ (Banjska) and the DOB (Bistrica, Sjenički Ozren and Brezovica) domains.
At the Banjska domain the chemistry of amphiboles from the metabasic members, (belong to the pargasitetschermakite-hastingsite series, with up to 1.9 wt.% TiO 2 ) imply temperature conditions which coincide with the maximum temperature of 760-780°C calculated for the garnet-cordierite-sillimanite gneisses, which occur as thin layers within the immediate contact with ultramafics (KORIKOVSKY et al. 2000a).The pressure of 6-7 kbar, estimated according to the jadeite isopleths in clinopyroxene from the clinopyroxene + plagioclase + quartz assemblages is also in accordance with the pressure calculated for the gneisses using the Grt-Crd-Sil-Qtz geobarometer of ARA-NOVICH & PODLESSKII (1989).This pressure corresponds to a depth of 24-25 km.The amphibolites from the Bistrica domain (DOB) were the subject of a few researches.The P-T estimates for garnet-clinopyroxene granulitic amphibolite, garnet amphibolites and corundum-bearing amphibolites are almost consistent and range from 740 to 830°C and 8-10 kbar.The amphibolites sensu stricto are metamorphosed under T-P of 600-650°C and 3.5 to 7 kbar.FED' KIN et al. (1996) pointed out that the retrograde stage of the thermal evolution of the Am+Cpx+Pl amphibolite was probably periodically interrupted by tectonic movements caused by the rapid ascent of the Bistrica complex.According to the Am-Cpx-Pl geothermobarometry and estimated P-T changes four phases or depth levels are distinguished.The peak metamorphic condition for the Bistrica garnet-bearing granulitic amphibolite, garnet clinopyroxene amphibolite, and amphibolite sensu stricto is estimated according to the amphibole -plagioclase geothermometer of HOLLAND & BLUNDY (1994).The temperature was calculated for the assumed pressures of 6 to 12 kbar and the pressure estimates were based on the Grt-Am-Pl-Qtz geobarometer of KOHN & SPEAR (1990) for the temperature range of 600 to 900°C.The average P-T value resulted from the intersection of lines for calculated temperatures and pressures (taking into consideration the average error of the applied method).The obtained temperature of 808°C ± 40°C and pressure of 9.5 ± 0.9 kbar corresponds to the lower part of the granulite facies (Fig. 7a).These results are in accordance with the data of MILOVANOVIĆ (1988) and FED' KIN et al. (1996).
The K-Ar age of the Bistrica amphibolite ranges from 168 to 174 ± 14 Ma (Table 3).The high PT conditions of the Bistrica garnet pyroxenite and its age of 146 ± 4.9 Ma (Nd-Sm) imply the subduction of oceanic crust ensued by exhumation and cooling in a subduction channel (BAZYLEV et al. 2006a): the exhumation can arise during SSZ-spreading and rollback of the subducting oceanic slabs and culminate in tectonic emplacement over a continental margin prior to the Tithonian-Berriasian time (see ROBERTSON et al. 2009).
The P-T conditions of the amphibolites comprising Cpx+Am+Pl (up to 80 % An) assemblage from the Sjenički Ozren (DOB) were calculated following the Hbl-Pl thermometer of JAQUES et al. (1982).The estimated peak metamorphic conditions of 750-830°C and 5-6 kbar (according to Al-in Hbl geobarometer and high pyrope content in garnet) imply a depth of 18-22 km (Table 3).The age of those amphibolites and of the Banjska metamorphic sole remains unknown.
The inverted zonal metamorphic sole at the subduction-accretion complex of Brezovica (DOB) is characterized by metamorphic imprint of igneous basic rocks to amphibole schists and amphibolite varieties in the temperature range from 350-500°C in the third zone to 500-600°C in the second zone.The maximum metamorphic peak of 600-670°C is attained in the first A zone to 700-750°C in the first B zone at almost isobaric condition (7-9 kbar).On the basis of P-T calculations two subdomains are recognized: the southwestern part with upper amphibolite facies (Borov Vrh, Malo Borče and Jezerina) and the northeastern part with greenschist to medium amphibolite facies conditions (locality Krst).Both show evidence of localized retrogressive reactions related to the subsequent uplift, cooling and thrusting of ultramafics: clinopyroxene and hornblende → actinolite and epidote; garnet → chlorite and epidote; plagioclase → saussurite.
The difference in the temperature imprint of these two subdomains, originally metamorphosed at almost the same depth, suggests that the ultramafic part of a single harzburgite mass had a different temperature.It should be stressed out that garnet, the usual source of information about prograde metamorphism, shows  (1967,1969,1970); P -PERCHUK (1989,1990) 1978) and162-169 Ma (OKRUSH et al. 1978).
At the Tejići domain (WVZ) the Am-Grt geothermometer (Table 2) gave an average temperature range of 620-670°C at an assumed pressure of 5.5 ± 1 kbar.This P-T range is similar to that obtained for the garnet-free clinopyroxene amphibolites in DOB (Table 3).The garnet mica schist displays lower P-T range (500 ± 50°C at 3-5 kbar) and could be assigned to uplift of hot ultramafic body (SREĆKOVIĆ- BATOĆANIN & VASKOVIĆ 2000).
The K-Ar age measured on amphibole and mica ranges from 157.6 ± 10 to 160.1 ± 7.1.
Based on mineral assemblages in amphibolites next to the ultramafic body at the Devovići domain a temperature of about 600°C is reported by POPEVIĆ (1973).
An inverted contact metamorphic aureole underneath the large Zlatibor ultramafic mass comprises three metamorphic zones.A temperature range of 300-350°C and pressure of 3-3.5 kbar for the third marginal zone (actinolite + pumpellyte + prehnite) is assumed using the petrogenetic grid for low temperature metabasites of LIOU et al. (1987).The remarkable progressive change in mineral assemblages within metabasites is realized in the transition to the second zone.It is characterized by the break down of pumpellyite and prehnite, replacement of actinolite rim by tschermakite, appearance of phengite (Si up to 3.38-3.41apfu, MgO up to 3.3 wt.%, FeO up to 2.9 wt.%), and an increase of anorthite component in plagioclase (7-15 %).The presence of rare intercalations of phyllites and paragneisses in metabasic members with mica and garnet (4-16 % of pyrope component from core to rim and decrease of grossular from 21-8 % and spessartine component from 15-7 %) allowed the Grt -Phn thermometer of GREEN & HELL-MAN (1982) to be used.A temperature range of 400-500°C was estimated (KORIKOVSKY et al. 2000b).The first zone with almost homogenous magnesiohornblende and tschermakite having a slightly elevated Ti concentration, plagioclase (20-50 % An) and rare augite with less than 2-3 % of jadeite component implies shallower depths when compared to the Brezovica aureole.The Grt-Pl thermometer of BLUNDY & HOLLAND (1990) gave temperatures of 550-650°C.The low concentration of jadeite component in clinopyroxene enabled rough estimation of pressure of 3-3.5 kbar at a temperature of ~650°C (Table 3).According to all these estimations KORIKOVSKY et al. (2000b) summarized that the Zlatibor massif was tectonically stabilized and started to cool isobarically at depths of approximately 12-13 km.
The K-Ar age of the Zlatibor metabasites is 160 Ma (KARAMATA & LOVRIĆ, personal communication) what is consistent with the ages obtained for the Tejići and the Brezovica metamorphic sole.
Based on mineral assemblages, estimated P-T conditions, zoning in mineral phases and obtained ages, the potential P-T-t paths are given for metabasic rocks from the WVZ and the DOB metamorphic sole (Fig. 7b).The retrograde assemblages indicating the overprint of high-to medium grade metabasites are low-temperature mineral phases of greenschist facies.
The tectonic settings that could be parental to the Serbian southwestern part of DOB (e. g.Bistrica) are assigned to the ocean thrusting and subsequent intraoceanic subduction.At the beginning the metamorphism operated at a depth ≥30 km (≥10 kbar and ~800 ± 50 °C).The appearance of corona texture and medium-PT mineral phases imply a short-lived high-PT event and subsequent fast exhumation of the ophiolitic sequence; at another domain the intra-oceanic subduction of SSZ-type, operating in various depths, was responsible for the development of metamorphic soles.Thus, the garnet clinopyroxene bearing metabasites of the Bistrica represent the deepest subducted slab (~30 km).Further northwest, the peak metamorphic condition of various types of amphibolites imply the shallower burial of subducted slabs -ranging from 18-25 km (Sjenički Ozren and Banjska) over 18-15 km (Tejići) until 12-13 km (Zlatibor).

Composition and Correlation of protoliths and tectonic implication
Generally, the ocean units of the Dinaridic and the Western Vardar Zone belt comprise sub-ophiolite mélange thrust by an ophiolite unit with a metamorphic sole at its base.Within them the different types of basaltic rock and rarely gabbros were metamorphosed under various metamorphic conditions.
The blueschists of the Fruška Gora are considered to be a relic of the subducted oceanic unit (MILO-VANOVIĆ et al. 1995).Recalculation of data reflects on prevailing of basaltic trachyandesitic composition instead of trachybasaltic (Fig. 8b).The ratios of incompatible elements (Ti, Zr, Y) suggest an MORB-and CAB-affinity (Fig. 8a).The latter was reported by MI-LOVANOVIĆ et al. (1995) as VAB-affinity (due to lack of data for Nb it is not possible to discriminate between Nb-Zr-Y).The Zr/Y ratio ranges from 4.01 to 5.95.The REE patterns normalized to chondrite values after SUN & MCDONOUGH (1989) show medium LREE enrichment (La N /Yb N = 1.41-3.43),no marked Eu-anomaly (Eu/Eu* = 0.84-1.13)and high SREE content (187.7-253.3)with two exceptions (85.8 and 116.6).All analyzed rocks are high-TiO 2 , Zr and Y type basaltic rocks enriched in alkalis (Fig. 8b, h).The relations between compatible and incompatible elements presented on spider diagrams normalized to the average N-MORB and average OIB (Fig. 8e) indicate a very strong negative Sr-anomaly relative to adjacent elements.In respect to the average N-MORB they are much more enriched in LILE and slightly in HFSE as compared with the average OIB (Fig. 8d).Actually, the reexamination of blueschist geochemistry has shown characteristics very similar to OIB (Fig. 8d; Fig. 8e).The strong negative Sr-anomaly as has been many times encountered in MORB and OIB environments (see HOFMAN 1997) could be a result of seawater-basic magma interaction i.e. alteration prior to subduction.During the high-P low-T metamorphism the LILE elements behave as immobile (e.g.BEBOUT 1995BEBOUT , 2007;;BEBOUT et al. 1999).Therefore, the blueschists probably originate from rocks whose composition is similar to OIB.
The metabasic rocks from the Tejići show the tholeiitic trachybasaltic to basaltic trachyandesitic composition (Fig. 8b).According to the ratio of Ti, Zr and Y they plot within MORB and CAB field (Fig. 8a).The Zr/Nb ratios (5.59-1.91)are lower than in the typical N-MORB (~32).The chondrite normalized REE patterns for garnet amphibolite (GA) and amphibolite sensu stricto (A) differ in LREE abundance (Fig. 8f).The former is much more enriched in LREE (70-100× chondrite values; La N /Sm N = 1.93) than the latter (~10× chondrite values; La N /Sm N = 0.77) with almost flat REE.The Eu-anomaly is absent (Eu/Eu* = 0.91-1).The La N /Yb N is 3.15 (GA) and 0.77 (A).The slight to moderate enrichment in LREE could be assigned to pre-metamorphic basalt-seawater interaction.The N-MORB normalized trace element patterns (Fig. 8g) are characterized by a negative slope from Rb to Sr and nearly smooth pattern from Zr-Y: the more mobile elements i.e.LILE are variably enriched; whereas, the HFSE have an N-MORB abundance.The (Nb/La) PM ratio (1.04-1.45)precludes sediment contribution.The Nb/Y is 0.46 (GA) and 0.19 (A).The Zr/Nb of 5.59 for the GA and 1.51 for the A and Ce/Y of 1.38 (GA) and 0.36 (A) ratios and Ti/Y vs. Zr/Y relation (see PEARCE & GALE 1977) indicate an E-MORB affinity as summarized also by SREĆKOVIĆ-BATOĆANIN et al. (2002).
The texture, mineral chemistry and geochemical composition (high Mg#, low SiO 2 /Al 2 O 3 values, REE pattern, and positive Eu anomalies) of the Bistrica metabasic sole rocks are consistent with a cumulate gabbro and evolved tholeiitic basalts originated in MORtype setting (BAZYLEV et al. 2003(BAZYLEV et al. , 2009;;MILOVANOVIĆ et al. 2008).The geochemical data of the Bistrica and the Zlatibor metabasic sole rocks are not published.
According to data of CHIARI et al. (2011) three types of basaltic rocks are recognized in the Zlatibor aureole.The first two have N-MORB, E-MORB or P-MORB affinities and their origin is assigned to partial melts derived from depleted mantle that was variably influenced by an OIB-component erupted in seamount or off-axis tectonic settings.The third one of CAB affinity originates in an island or a continental arc orogenic setting -the enrichments in Th and Yb are recognized as indicators of the SSZ-imprint.
The protoliths of the sole metabasic rocks of the Brezovica are identified as moderate to high-Mg, low-Ti and moderate to high-Ti low-K tholeiitic basalts (KARAMATA et al. 2000).Among them three sub-types are distinguished: strongly LREE depleted (La N /Sm N = 0.44 ± 0.22), moderately LREE depleted (La N /Sm N = 0.73 ± 0.13) and LREE enriched (La N /Sm N = 1.51 ± 0.36).The first two sub-types have geochemical feature similar or close to N-MORB while the third is transitional between enriched MORB (T-type) and OIB.Following their age (Table 3) the N-MORB basalts are recognized as products of an early oceanic stage or later paleo-oceanic products, whereas the third (T-MORB-OIB), the oldest one closely linked to the initiation of oceanic basin and continental fragmentation, is SSZ-type.They show similar features with those within the northwest and southern continuation of DOB (Krivaja-Konjuh, Borja, Mirdita-Pindos) concerning their LREE abundance, TiO 2 , P 2 O 5 as well as with metabasalts of E-MORB affinity in WVZ (e.g.Tejići).

Conclusions
The correlation of data collected from the available literature related to the metabasic sole rocks developed at the base of the ophiolites of DOB and WVZ with contribution of new data for the Bistrica metabasic rocks allow to summarize and conclude that: 1. Spatial relation and comparison of mineralogical, petrological and geochemical data as well as P-T conditions of metabasic sole rocks between the WVZ and the DOB ophiolites, with the exception of Fruška Gora, confirmed their common origin; 2. The different types of metabasic sole rocks occur at the base of obducted ophiolites as thrust or collided sheets, large blocks and fragments within the subophiolitic mélange; 3. Metamorphic structures (i.e.foliation) of the majority of metabasites are parallel to basal thrust faults beneath the overlying peridotites; the same feature is confirmed in the metasediment interlayers occurring within; 4. The zonal composition of amphiboles and garnets from some metamorphic soles (e.g.Tejići, Zlatibor, Sjenički Ozren and Brezovica) are controlled by temperature; the relatively high Al IV /Al VI ratios in amphiboles imply mostly the moderate increase of pressure during metamorphism; due to pressure drop and a subsequent short thermal increase the garnet from the Bistrica granulitic amphibolite show corona textures; 5. The metamorphic peak conditions recognized based on mineral assemblages and chemistry of minerals, determined: a) a high-P -low-T epidote-blueschist facies at 4-8 kbar and <300-350°C to 7-9 kbar and ~400°C (Fruška Gora); b) a high-PT amphibolitegranulite to amphibolite facies at 8-10 kbar and >700-850°C (Banjska, Bistrica, Sjenički Ozren and Brezovica); c) a greenschist to medium-PT amphibolite facies at ~3.5-7 kbar and >350-650°C (Tejići, Devovići and Zlatibor).
6. Major, trace and rare earth element distribution and elemental ratios within metabasic rocks bear geochemical affinities of cumulate gabbro and basalts of SSZ-type (E-MORB and OIB signature) or more evolved tholeiitic basalts of MOR-affinity (e.g.Bistrica); the E-MORB -OIB affinity can be linked to the rifting in an oceanic spreading center, partially affected by a plume-mantle component in both domains (WVZ and DOB); the east-dipping intraoceanic subduction (SCHMID et al. 2008;CHIARI et al. 2011) was responsible for the evolution of the metabasic sole rocks at different metamorphic grades; according to available data it probably started at the end of Early Jurassic (178 Ma) leading to development of back-arc SSZ oceanic basins in the Middle-Late Jurassic; 7. The depth of metamorphism, i.e. the depth of detachment varies from 10 to 30 km.
8. The still hot overlying ultramafics were responsible for the creation of an inverted metamorphic sole during intra-oceanic obduction (KARAMATA et al. 2000;ROBERTSON et al. 2009 and reference therein); 9.At the Fruška Gora domain the different rocktypes from the olistostrome mélange including subalkaline basalts were buried to the depths of 14-30 km by cold subduction.The generated blueschists are represented by two different mineral assemblages: glaucophane(riebeckite) + pumpellyite + actinolite + epidote at its west slope and ferro-glaucophane (earlier crossite) + riebeckite + albite + epidote + phengite at its eastern slope; 10.The reported K-Ar age range is between 174 and 146 Ma and spans almost 30 Ma.
11.The estimated P-T conditions and mineral assemblages depicted in metabasic sole rocks in the Serbian Dinaridic and the Western Vardar ophiolites are mostly in accordance with the majority of metamorphic sole metabasites developed in their northwestern and western continuation in Bosnia (e.g.Krivaja-Konjuh, Borja, Ozren, Kozara) and Croatia ("Sava Zone" or WVZ) where blueschist facies metabasic rock occur as remnant of cold subduction within the sub-ophiolitic mélange (Medvednica & Motajica, see BELAK & TIBIJAŠ 1998 ) along with its east-ern occurrence at Mt. Fruška Gora.Additionally, the metabasic sole rocks are spatially related with those exposed further south in Albania (Mirdita zone) and in Greece (Pindos zone).
This correlation reveals the need to further clarify various aspects of metamorphic sole formation, particularly for those which have not yet been studied and whose age remains uncertain.

Fig. 7
Fig. 7. a) P-T ranges of the metabasic rocks from the WVZ and DOB metamorphic sole.Reaction curves: Am-in, Amout and Grt-in (ERNEST & LIOU 1998); Prp-in, Jd+Qtz and An-out (GREEN & RINGWOOD 1967); Cpx-in, Opx-in (MU-KHOPADHYAY & BOSE 1994); titanite-ilmenite and rutile (LIOU et al. 1996); Prh (FREY et al. 1991); b) Assumed P-T-t paths for the DOB and WVZ metamorphic sole rocks operated during the intra-oceanic subduction and cold subduction within the northern part of the WVZ or Sava Zone (SZ) -Fruška Gora.Inlet in the upper left corner shows the depth of metamorphism (a) and (b) begining of subduction related to scrutinized domains with different rock types.The P-T-t path of slow-subduction of young oceanic lithosphere is after PEACOCK et al. (1994).

Table 1 .
Representative mineral chemistry of the Bistrica amphibolites used in thermobarometry.
of prograde zoning growth.It is reflected in an increase of Mg and decrease in Ca component from core to rim.It is almandine rich with up to 24 % of pyrope component in the outer shells in the second to nearly 40 % in the first distinguished zone. evidence