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Reconstruction of the primary stratigraphyand correlation of the Precambrian metamorphiccomplexes in the Rhodope massif

Evgenia Kozhoukharova

Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia; E-mail: evgkozh@geology.bas.bg

(Submitted: 14.11.2007; accepted for publication: 16.11.2007)

E. Êîæóõàðîâà – Ðåêîíñòðóêöèÿ ïåðâè÷íîé ñòðàòèãðàôèè è êîððåëÿöèÿ äîêåìáðèé-ñêèõ ìåòàìîðôè÷åñêèõ êîìïëåêñîâ â Ðîäîïñêîì ìàññèâå. Ëèòîëîãè÷åñêèé àíàëèç ìåòà-ìîðôè÷åñêèõ ïîðîä Ðîäîïñêîãî ìàññèâà, ñ ó÷åòîì ëàòåðàëüíûõ èçìåíåíèé ïåðâè÷íîãîñîñòàâà, ïîëèìåòàìîðôè÷åñêèõ ýôôåêòîâ è òåêòîíè÷åñêèõ äåôîðìàöèé, ïîêàçûâàåò ÷òîâåðõíÿÿ Ðîäîïñêàÿ íàäãðóïïà äî ìåòàìîðôèçìà ñîñòîÿëàñü òîëüêî èç äâóõ êîìïëåêñîâ:íèæíèé âóëêàíî-îñàäî÷íûé è âåðõíèé — èçâåñòêîâûé. Íèæíèé êîìïëåêñ ïîñëå ìåòàìîð-ôèçìà ñîñòîèò èç ìåòàîôôèîëèòîâ (ñåðïåíòèíèòîâ, àìôèáîëèòîâ, ìåòàãàááðîèäîâ, çàíè-ìàþùèõ íèæíèå ãîðèçîíòû), ñëþäÿííûõ ñëàíöåâ, ìðàìîðîâ, êâàðöèòîâ, äæåñïèëèòîâ, íà-çâàíûé çäåñü Ïåñòðàÿ ñâèòà. Âåðõíèé êîìïëåêñ ñîñòîèò èç ìðàìîðîâ ñ ïðîñëîÿìè ñëàíöåâ.Ðàçëè÷àþòñÿ äâà òèïà Ïåñòðîé ñâèòû: à. Çàïàäíîðîäîïñêèé (Ñàòîâ÷àíñêèé) òèï, ñ ïðåîáëà-äàþùèìè îôôèîëèòàìè â íèæíèõ ãîðèçîíòàõ è á. Öåíòðàëüíîðîäîïñêèé (Ëóêîâèöêèé) òèï,ñ ïðåîáëàäàíèåì îñàäî÷íûõ ïîðîä. Ïðåäñòàâëåíà íîâàÿ ñõåìà êîððåëÿöèè ëèòîñòðàòèãðà-ôè÷åñêèõ åäèíèö äîêåìáðèéñêèõ áëîêîâ â Þæíîé Áîëãàðèè.

Abstract. The lithological analysis of the metamorphic rocks in the Rhodope massif, taking intoconsideration the lateral variability of their primary composition, polymetamorphic effects andtectonic deformations, demonstrates that prior to the metamorphism the upper Rhodopian Su-pergroup is composed of two complexes: lower volcano-sedimentary and upper calcareous ones.The lower complex after the metamorphism is composed of metaophiolites (serpentinites, am-phibolites, metagabbroids) in the lower levels), mica schists, marbles, quartzites, jaspilites, calledVariegated Formation. The upper complex is composed of marbles interlayered with schists.There are two types of Variegated Formation: à. Western Rhodopian (Satovcha) type with ophi-olites prevailing in lower layers and b. Central Rhodopian (Lukovitsa) type with sedimentaryrocks prevailing. A new correlation scheme of the lithostratigraphic units from Precambrianblocks in South Bulgaria is presented.

Kozhoukharova, E. 2008. Reconstruction of the primary stratigraphy and correlation ofthe Precambrian metamorphic complexes in the Rhodope massif. — Geologica Balc., 37, 1—2; 19—31.

Key words: Precambrian; stratigraphy; metamorphism; protoliths; ophiolites; correlation.

Introduction

The stratigraphic column of every metamorphic com-plex represents superpositions of the lithological unitsthat have been established after metamorphic con-solidation of the basement. It usually differs fromthe primary column of the sedimentary complex. The

interregional correlations, based on lithological sim-ilarity and stratigraphical sequences, cannot be ap-plied due to the polymetamorphic alteration, tecton-ic deformations and unreliable age data of the meta-morphic formations.

The actual stratigraphic scale of the Rhodopemetamorphic basement (Kozhoukharov, 1988), used

GEOLOGICA BALCANICA, 37. 1—2, Sofia, Iun. 2008, p. 19—31.

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in the Geological Map of Bulgaria M 1:100 000, rep-resents also nowadays a real superposition of lithos-tratigraphic units without pretending to correspondcompletely to the primary one. The aim of this paperis to make an attempt to reconstruct the initial rela-tionships of the stratigraphical units as well to launcha new point of view for correlation of the Precam-brian blocks in South Bulgaria and Northern Greece.

The main factors having control on the featuresof metamorphosed lithostratigraphical units are:a) primary lateral variation of rock composition, ex-pressed mainly in the volcanogenic-sedimentary for-mations; b) superimposed polymetamorphic alter-ations in different facies; c) isoclinal folds and shearzones caused reverse or repeating of sequence. Litho-logical and petrological analysis and detailed struc-tural mapping were the principal methods for de-coding of the stratigraphic and tectonic inversions.

Precambrian complexesin the Rhodope massif

The Precambrian in Bulgaria is subdivided (Âåðãè-ëîâ è äð., 1963) into two different polymetamorphiccomplexes and the later investigations confirm theirexistence.

Prarhodopian Supergroup

The lower Prarhodopian Supergroup (PRS) is anancient infracrustal continental complex, consist-ing of highly reworked monotonous para-and ortho-gneisses, granite-gneisses, different migmatites (withporphyroblactic, lenticular, ptygmatic, stromatic,nebular texture), biotite and leptite gneisses. Miss-ing of marbles is a specific feature for this super-group.

Cadomian, Hercynian and Alpine granitoid mag-mas and some generations of their aplite-pegmatitevein derivates, penetrate the complex, causing mig-matization, granitization, feldspathization andreheating, particularly intense in the deep zones. Asa result the whole rock complex has been enrichedwith components like Si, Al, Na, K, Ba, Rb, Cs andobtained geochemical character of granite-granodior-ite. The products of the later superimposed metaso-matic processes often are undistinguished from theearly Precambrian metamorphites. By this way thechemical alterations as well the deformations in someplaces changed considerably the features of the pro-toliths and depreciate the efforts for its recognitiononly by geochemical methods.

The Prarhodopian Supergroup builds up the coreof anticline and dome structures.

Stratigraphy of the Prarhodopian Supergroup. De-spite the overgone alterations with different age, arather clear stratification of the Prarhodopian Su-pergroup is observed. Strazhevo Group (Êîæóõàðîâ,1987) in Belareka dome (Eastern Rhodope block)

demonstrates the following sequence from base to top:biotite gneisses (Orlovo Formation), leptite gneisses(Gornoyuroutsi Formation) and porphyroblasticgneisses (Punovo Formation). The porphyroblasticgneisses are base and cover of the variegated materi-als of Botourche Group — serpentinites, amphibo-lites, mica schists and thin marble layers, becausethis group fills up a tight recumbent syncline (Ko-zhoukharova, 1999, Fig. 1). Therefore BotourcheGroup is not considered to be part of the Prarhodo-pian Supergroup as it was assumed in previous years(Áîÿíîâ è äð., 1963; Kozhoukharov, 1988).

Similar interrelations, but not so clearly expressed,are also observed in Tintyava dome.

The same stratigraphic sequence is observed inthe Northern Rhodope anticline (Central Rhodope),where these rocks have been described as part ofRhodopian Supergroup. The sequence upward is:biotite gneisses (Boykovo Formation), leptite gneisses(Bachkovo Formation) and porphyroblastic gneisses(as thin irregularly developed layer), covered by thevariegated Loukovitsa Formation.

Bogoutevo Formation in Chepelare region (Rho-dopian Supergroup), which is composed from high-ly migmatized biotite and two-mica gneisses and athin upper level of leptinite gneisses, builds up thecore of a reduced southvergent anticline, with bro-ken southern flank. Bogoutevo Formation overliesthere the variegated Chepelare Formation and is cov-ered by the variegated Vucha Formation, which is ofsimilar composition. The migmatized gneisses, dueto their intensive ductile and brittle deformations,do not show clear stratification. Nevertheless, theirrocks composition, geological position and interre-lations with the variegated formations, give us groundto consider that Bogoutevo Formation is a correlateof the Boykovo and Bachkovo Formations from theNorthern Rhodope anticline, as well is correspond-ing to Orlovo and Gornoyuroutsi Formations fromthe Eastern Rhodope block.

The stratigraphic sequence of biotite gneisses, lep-tite gneisses and porphyryblastic gneisses (the latterare in irregularly developed layered bodies) is ob-served as well in Gotse Delchev region, WesternRhodope. There the recumbent Debrene syncline(Êîæóõàðîâà, 1987) again destroys the normal strati-graphic sequence.

The cross-section of the basement in the Sakarblock is similar by composition to this in the EasternRhodope block. There the porphyroblastic gneissesfrom Punovo Formation continue in KostantinovskaMetaconglomerate Formation (Êîæóõàðîâ, 1991).

Most widely spread outcrops of PrarhodopianSupergroup are located in Madan-Davidkovo dome.There due to intensively developed migmatization andgranitization processes of variable age and due tothe internal isoclinal folding of the gneisses, clearstratification is not observe as it is in Belareka dome.In the eastern periclinal flank of the Madan-David-kovo dome the highly squeezed and deeply sunk Ar-dino syncline is located (Kozhoukharova, 1996;Ïðèñòàâîâà, Êîæóõàðîâà, 1999), filled with the var-

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iegated materials of Chepelare Formation (Rhodop-ian Supergroup) — amphibolites, serpentinites, schistsand marbles. Several isoclinal mesofolds of secondorder and shear zones complicate the flanks of Ar-dino syncline causing an alternation between PRSmigmatic gneisses and RS amphibolites, schists andmarbles. Due to this alternation, giving a wrong im-pression of normal sequence, is formed the so-calledVishnevo Formation. The latter demonstrates a tec-tonic style typical for highly migmatized metamor-phic terrains where a tectonic mixing of rocks, be-longing to different lithostratigraphic units, desig-nated by Çàãîð÷åâ (2003) as amalgamating, is ob-served.

Thus, the sequence: biotite gneisses, leptites, por-phyroblastic gneisses is repeated in the core of theanticline structures in several areas of the Rhodopemassif. Although the rock formations as lithostrati-graphic units have different names, they are one andsame by genesis and composition. The section ofStrazhevo Group (Belareka dome) is the most com-plete and therefore its names will be kept: à. biotitegneisses — Orlovo Formation, with analogs of Boyko-vo and Bogoutevo Formations, leptite gneisses — Gor-noyuroutsi Formation, with analog of Bachkovo For-mation and porphyroblastic gneisses — Punovo For-

mation, with continuation of Konstantinovo Meta-conglomerate Formation

Rhodopian Supergroup

The upper Rhodopian Supergroup (RS), a new trans-gressively deposited typical supracrustal variegatedcomplex, is built by metamorphosed volcanogenic-sedimentary rocks (Fig. 1). Its primary rocks were fly-schoid pelite-calcareous sediments (Variegated For-mation — VF), alternated with ophiolites in the lowerstratigraphic levels and ended by limestones (MarbleFormation — MF). The sediments were transformedinto biotite, muscovite and two-mica schists, marbles,calco-schists, quartzites. The primary ophiolitic rocksof the Precambrian Ophiolite Association in Rho-dopes (POAR): serpentinites, gabbros, low potassi-um-high magnesium tholeiites, tuffs and tuffites haveundergone polymetamorphic alteration in differentfacies and as a result talc-chlorite-actinolite schists,amphibolites, eclogites, pyroxenites, garnet-lherzolitesand metasomatic gabbroids were produced. The up-per part of the RS is built of thick layered marbles(Dobrostan Formation) with rare schist intercalationin upper levels (Belashtitsa Formation).

Fig. 1. Columns of the Variegated Formations in the Rhodope Massif

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The Variegated Formation with POAR is an im-portant stratigraphic marker for reconstruction ofthe internal structure of the basement. Everywherethe VF lies on the leptites or porphyroblastic gneiss-es of the Prarhodopian Supergroup and is coveredby marbles of Dobrostan Formation. It is also a goodindicator for the pre-metamorphic paleographic sit-uation as well for metamorphic evolution.

Lateral variation is a very specific feature of themetamorphosed lithostratigraphical units in partic-ular clearly expressed in VF. Three main factors areresponsible for this: primary composition, metamor-phism and tectonic deformations, which influencesomewhere is so strongly that delete the original ap-pearance of VF rocks and prevents the interregionalcorrelation.

1. Variation in the primary composition. In the areasof abundant basic volcanism the background sedi-mentation was suppressed and there only very thinrare calcareous or rich of aluminum pelite beds wereproduced. Amphibolites, amphibole-schists, numer-ous big and small serpentinite bodies dominate inthe lower layers of VF (Fig. 1).

On the same stratigraphic levels in other regionslike northern part of Central Rhodope (Northern

Rhodope anticline), the calcareous and aluminouspelites (future marbles and kyanite schists) are wide-ly spread. The amphibolites occupy also lower levels,but they build only thin beds, alternating with mar-bles and schists. The metamorphosed pelites withmarble intercalations dominate in the lower part ofVF, while the calco-schists and marbles — in the up-per ones. The comparative lithological analysis ofthe outcrops of the variegated formations (Fig. 1) aswell the stable features of gneisses from the sole andthe cover of marble, are enough convincing facts thatthe Variegated Formation in the Rhodope massif isthe one and the same. It is named as different unitsdepending on its levels in the metamorphic complex.

Two type of VF are distinguished: a. West Rhodopi-an (Satovcha) type and b. Central Rhodopian (Louk-ovitsa) type (Fig. 2).

A. West Rhodopian (Satovcha) type of VF representsa rock formation, formed in the region of active vol-canism where the volume of basic-ultrabasic orth-ometamorphites prevailed over the parametamorphi-tes (Fig. 2). It starts usually with ophiolites (serpen-tinites or amphibolites) lying directly on the gneissesof the Prarhodopian Supergroup. VF continues up-

Fig. 2. Main types of the Variegated Formation of in the Rhodope Massif

a b c

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wards like a thick sequence of layered and massivemedium- to coarse-grained amphibolites, amphibole-,actinolite- and actinolite-chlorite schists, interbed-ded by graphite-bearing garnet quartzites, magne-tite-hematite jaspilites and biotite schists. Serpentinitebodies of different dimensions associate with amphi-bolites. Dykes of fine-grained amphibolites, often en-riched of ore minerals, cross the layered amphibo-lites and serpentinites. Rare small xenoliths of gneisses,with sharp contours from the sole occur among theamphibolites. The chemical composition of amphib-olites corresponds to normal, high magnesium tholei-itic and komatiitic basalts.

Two-mica and kyanite bearing biotite schists fol-low the ophiolite packet. The calcareous layers —marbles and calco-schists appear relatively high inthe stratigraphic sequence and when cross-sectionin the field is short, the marbles often are missing.Sometimes because of this reason, such VF withoutmarbles have been refered to the Prarhodopian Su-pergroup, f. e. Botourche Group (Áîÿíîâ è äð., 1963;Kozhoukharov, 1988).

Furthermore in the regions of active volcanismon the base levels of VF some beds with differentthickness (2—3 to 200—300 m) of porphyroblasticgneisses are found. Its protoliths are believed to havebeen coarse-grained or fineclastic sands rather thanporphyritic granites. They presumably mark anabrupt change in paleoenvironmental setting beforethe forming of ophiolitic association. Thin layers (2—3 m) from coarse porphyroblastic gneisses are foundeven among schists on the base of VF just beneaththe amphibolites pack, which proves their sedimen-tary origin. Such outcrops are in the valley of Lozen-grad river in Eastern Rhodopes.

Satovcha type of VF is wide spread in WesternRhodope — valley of Mesta river, Satovcha syncline,Yakorouda district, also Vlahina Mts. In the EasternRhodopes (Fig. 2) — Belareka dome, Avren syncline,Chakalarovo syncline and Drangovo horst, the com-position of VF is similar but the typical basic metavol-canic rocks decrease while the large serpentinite bod-ies are frequent there.

The location of the most abundant metavolcanites,particularity in the Mesta valley, suggests for a pos-sible initial rifting of the ancient continent.

B. Central Rhodopian (Loukovitsa) type VF is observedin the northern part of the Central Rhodope Mts rep-resented in Loukovitsa Formation. It consist mainlyof alternating metapelites transformed into biotite-,muscovite-and two mica schists (some of them kyan-ite bearing), marbles, calco-schists and few quartzites(Fig. 2). Metapelites predominate in the lower levels ofthe VF, while marbles and calco-schists — in the upperones. The amphibolites — products of subvolcanic andvolcanic igneous activity built thin beds in lower partof the VF. These in some areas of the NorthernRhodope anticline are connect to subintrusive body,which crosses the leptite gneisses from the base of VF.

The correlation between the variegated formationsoutcropping in Rhodope Mts. shows identical com-

position and consistency in the sedimentary pack-age and the difference is only in the amount of basicand ultrabasic orthometamorphites.

2. Variation in the metamorphic facies of VF. TheVariegated Formation composition during the region-al metamorphism fall into different P/T conditions,crystallizes in respective metamorphic facies andobtains corresponding mineral association, oftenoutlining vertical or lateral zoning. Sometimes thealterations are principal isochemical and by meansof petrologic analysis it is possible to recognize theprimary sedimentary or magmatic composition ofmetamorphic rocks. Migmatization provokes someother problem. Usually it causes considerable sub-stantial change as feldspathization and quartzitiza-tion of rocks. For example mica-schists are trans-forming into gneisses, amphibolites — into metaso-matic gabbro-diorites, which are difficult to distin-guish from the true magmatic rocks. Sometimes suchhybrid products are described as magmatic metagab-bro and after its nowadays chemical composition thepaleodynamic setting was interpreted.

Eclogites and garnet lherzolites, related to ophio-lites, are characteristic HP-metamorphic products forthe VF. The eclogites are developed as layers parallelto the metamorphic foliation among amphibolites(Kozhoukharova, 1980) and by folding form boudi-nage structures. The Gr-lherzolites occur in serpen-tinites like thin bands in shear zones (Kozhoukharo-va 1966), but always in the stratigraphic level of theophiolites. The suggestions of some authors (Dercourt,Ricou, 1987; Burg et al., 1990; Dobretsov, 1991; Hay-doutov et al. 2004), that eclogites mark zone of sub-duction, deep thrusts or suture lines were not provedwith geological facts from the outcroping sectionsof the metamorphic basement of the Rhodope mas-sif. The hypothesis that the eclogites are formed indeep zones, uplifted in the upper levels of the crys-talline as external bodies is disproved by their stablestratigraphic level in the Variegated Formations. Theidea that HP-metamorphism developed within thewhole crystalline basement in zones of subduction,followed by later exhumation, is even more unaccept-able. The well preserved stratification and linear foldstructures exclude deformation in subduction zones.On the other hand the background amphibolite fa-cies of surrounding rocks and presence of big ser-pentinite bodies (regressive serpentinization amongmetamorphic complex is impossible) prove that thetemperature of the background regional metamor-phism does not exceed 580°C. For the moment, theconclusion for locally developed HP-metamorphismin narrow zones of friction on the background ofamphibolite facies (Kozhoukharova, 1999; Êîæó-õàðîâà, 2006) corresponds more closely to the realgeological situation.

The Phanerozoic dynamometamorphism, whichinflicts also different damage on the composition andtextures of the rocks are of particular importance. Itprovokes irregular destructive phenomena and re-gressive alteration, marked by a new greenschist

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parageneses: quartz, sericite, chlorite and albite inthe gneisses and amphibolites. For this reason VF insame places was announced as other different for-mation (for example diaphthoretic Parvenets com-plex — Èâàíîâ et all., 1984) or some mylonitizedmarbles in Central Rhodope, defined as Mesozoiclimestones (Ivanov, 1988).

3. Variation of tectonic characteristic of VF. Therock complex of the Rhodopian Supergroup withthe VF had been subjected to synmetamorphic fold-ing at least twice. As a result isoclinal fold struc-tures different in size and morphology were formed,which are typical for the deformed in ductile envi-ronment ancient metamorphic complexes. In thegeneral synmetamorphic structural plan, the dia-piric raised domes and linear positive structures areobserved, whose cores are built of gneisses of thePrarhodopian Supergroup. The synclinal spaces be-tween them contain the compressed deeply sunk sub-vertical, inclined and recumbent folds, filled by moreheavy rocks of the Rhodopian Supergroup. The limbsof main folds are complicated by isoclinal, similarand disharmonious mesofolds. Boudinage and rod-ding structures are also frequent. By this reason of-ten some lithostratigraphic units repeat in the pro-file, suggesting the illusion for normal primary se-quence. Examples for repeating of the lithostrati-graphical units is established in West Rhogopes (Êî-æóõàðîâà. 1987), Eastern Rhodopes (Kozhou-kharova, 1996, 1999), Central Rhodopes (Ïðèñòà-âîâà, Êîæóõàðîâà. 1999). At the boundary betweenlithological units often is observed also thin bedamalgamation.

In some areas within the migmatized gneisses (forexample Bogoutevo Formation in the valley of Che-pelare river), bordering with ophiolites from the VF,some rounded rootless bodies of amphibolitizedeclogites can be observed. These are cut like thin frag-ments from the basement of the synclines and formedunder the gravity collapse, described by Gorman etal. (1978) for analogical terrains (Fig. 3).

The lithological and stratigraphical analysis ac-cording to all mentioned above facts, points at thefollowing conclusions about VF:

— There was only one Primary Variegated Forma-tion in the Rhodopian Supergroup, but in depen-dence of its superposition in sequence it has differ-ent names like Chepelare, Vucha or Loukovitsa For-mation (Fig. 2). It is suggested that the VF shouldstay with the name Loukovitsa Formation. The ar-guments for this are: i) for the first time it has beendefined and described (Êîæóõàðîâà, Êîæóõàðîâ,1962) in the Northern Rhodope anticline, where laterwas nominated as Lukovitsa Formation; ii) the sameformation demonstrates there the most complete sec-tion with base (Bachkovo Formation) and cover (Do-brostan Formation), iii) the VF there is in normalstratigraphic position;

— Zhalty Chal and Gnesdare Formations of Bot-ourche Group, referåd to Prarhodopian Supergroup(Áîÿíîâ è äð., 1963; Koæóõàðîâ, 1987), are forma-

Fig. 3. Scheme of formation the deep synclines in VF withgravity collapse

tions of Satovcha type, set in an inclined syncline(Kozhoukharova, 1999) and it is correctly to referthem to Rhodopian Supergroup;

— The POAR is an integral part of VF. Nowhere itis present normally in the Prarhodopian Supergroup.Some serpentinite bodies occur among “gneisses”, butduring the geological revision it turned out that those“gneisses” are feldspatized mica-schists, often bear-ing relicts of kyanite;

— The boundary between VF of Rhodopian Su-pergroup and gneisses of Prarhodopian Supergroupis a transgressive one, consolidated during the re-gional metamorphism. POAR (with eclogites in it),occupies low stratigraphic levels of VF. It nowheremarks sutures, thrust surfaces, deep faults or sub-duction zones;

— The POAR is heterogeneous basic-ultrabasicmagmatic formation that has originated probably inactive marginal continental basins in an island arcsystem during Neoproterozoic. The serpentinites have

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been obduced like fragments of hydrated ocean crustand later have been cut and covered by low K, high Tiand Fe tholeiitic, magmas (Êîæóõàðîâà, 1984, 1985)in a supra-subduction setting. The geochemical sig-nature of basic protoliths does not lead to a indisput-able decision about affinity of metabasic rocks to somegeodynamic zone as MORB, IAT or OIB (Kozhou-kharova, Daieva, 1990; Çàêàðèàäçå è äð., 1993; Áà-çûëåâ è äð., 1999; Haydoutov et al., 2004; Õàéäóòîâè äð., 2003) and probably hints their supra-subduc-tion origin in an island arc/back-arc system, with iden-tifiable arc-related and rifting/sea-floor spreadingmagmatic products (Bonev et al., 2006);

— The basic magmatism is autochthonous one andit is proved by the subintrusive bodies and dykes cross-ing leptite gneisses of the Prarhodopian Supergroup,as well as by the xenoliths of leptites among the ortho-amphibolites;

— The eclogites always are connected with am-phibolites of VF. Some small bodies, found in gneiss-es near the contact between VF and gneisses fromthe foot, got there as result of gravity collapse or amal-gamation;

— The eclogites are crustal metamorphic prod-ucts and they are displayed along local shear zonesof friction among the amphibolites and serpentinitesin the same stable stratigraphic level of VF (Ko-zhoukharova, 1996, 1999). They are not producedwithin subduction zones.

— The age of VF and ÌF by fossil data is Rifean(Êîæóõàðîâ, Òèìîôååâ 1989; Êîæóõàðîâ, Êîí-çàëîâà, 1990). Corresponding age is defined by theabsolute age data for the basic magmatism: Neopro-terozoic — 610 Ma in the Central Rhodope (Arka-daskiy et al., 2003) and 572 Ma in the Eastern Rho-dope (Carrigan et al. 2003).

The age of the gneisses of the Prarhodopian Su-pergroup is still under discussion. The Phanerozoicmetasomatic processes, related to the influence ofthe Hercynian and Late Cretaceous/Paleogene gran-itoid magmatism, have caused strong thermal andsubstantial impacts. The data of the absolute age ofthe protoliths and metamorphism cover very wide in-terval from Precambrian to Paleogene. For the por-phyroblastic gneises from Panovo Formation (Belare-ka dome) there are reported 1700-1800 Ma (Peyche-va, v. Quadt, 1995), interpreted as the age of the de-trital zircon from sedimentary formations and 305-319 Ma for the intrusive Paleozoic granites. Precam-brian age of the ancient sediments — 3230 Ma and560 Ma (Liati, Gebauer, 1999) and 670—560 Ma (Li-ati, 2005) is reported for analogous gneisses in North-ern Greece.

Correlations of metamorphosedlithostratigraphical units in thePrecambrian blocks of South Bulgaria

The generalized stratigraphic column of the prima-ry lithological units (Fig. 4) represents two groups.The lower group — a continental infracrustal com-

Fig. 4. Generalized lithostratigraphic column of the Precam-brian in the Rhodope Massif

plex (PRS) is best represented in Strazhevo Group inEastern Rhodopes and may be used as an etalon forthe stratigraphy of the PRS. It is divided on threesubgroups: biotitic gneisses of Orlovo Formation, lep-tite gneisses of Gornoyuroutsi Formation and por-phyroblastic gneisses of Punovo Formation. OrlovoFormation is comparable with Bogutevo and Boyko-vo Formations and the Gornoyurutsi Formation —with Bachkovo Formation from the Central Rhodopes.Pockets of porphyroblastic gneisses, identical ofPunovo Formation, occur on the same stratigraphiclevel in some places.

Vishnevo Formation consisting of gneisses, mica-schists, marbles and amphibolites is a mixed one be-cause of the folding and tectonic amalgamation.

The upper group — a supracrustal complex RSis devided of: i) Variegated Formation with meta-morphosed analogs Botourche Group, Chepelare,Vucha and Loukovitsa Formations (Fig. 4) and ii)Marble Subgroup (Dobrostan and Belashtitsa For-mations).

The whole metamorphic basement in Sredna GoraZone was refered to Prarhodopian Supergroup(Âåðãèëîâ è äð., 1963). It includes undivided ArdaGroup and undivided Botourche Group (Geologi-

4 Geologica Balcanica, 1—2/2008

26

cal Map of Bulgaria M 1:100 000: Ihtiman, Pana-gyurishte, Kazanluk mapsheets). But lithological fea-tures of Botourche Group are in line with Variegat-ed Formation — Satovcha type of RS and only gneissesof Ardino Group correspond to PRS (Fig. 5).

The Ograzhdenian Supergroup, outcropping in SWBulgaria, also is believed to be a correlate to PRS(Zagorchev, 1993, 2001). In our opinion Ograzhde-nian Supergroup is composed by migmatite gneissesof PRS and Variegated Formation — Satovcha type ofRS. The latter is represented there of chloritoid andkyanite bearing mica-schists, amphibolites, serpen-tinites. The migmatization and feldspathization insome places is so strong that transforms the mica-schists to enriched of white mica gneisses, where relictsof kyanite have been preserved. Among such “gneiss-es” lie the serpentinite bodies, cut by pegmatite veins.

Some remarks about correlation of themetamorphites from Rhodope Massif —South Bulgaria and Northern Greece

Irrespectively of different principles for subdivisionof metamorphic complexes in Rhodope from SouthBulgaria and Northern Greece, it is possible for themoment to make enough satisfactory correlationscheme (Fig. 6).

The Asenitsa group of RS, including Belashtitsaand Dobrostan Marble Formations in NorthernRhodopes corresponds to Menikio and Bos Dag units(Fig. 6) in Northern Greece after fossil and lithos-tratigraphical data (Zachos, Dimadis, 1983; Zagor-chev,1994; Kozhoukharov, 1994a, b).

The marbles from “Upper group of Pangaion unit”(Papanikolaou, Papadopoulos, 1981), and the mar-ble from “upper group of Sidironero units” are cor-relates of Dobrostan Marble Formation of RS.

The Variegated Formation of RS is correlated withNimpheas unit (Zagorchev, 1994). Amphibolites andschists from “Lower group of Pangeon units” (Papan-ikolaou, Papadopoulos, 1981), kyanite and garnet bear-ing mica schists from “Lower group of Sidironerounits”, as well as complex Kimi from “Upper tectonicunits” in Eastern Rhodopes (Mposkos, 1989) also cor-respond to the Variegated Formation of RS too.

The porphyroblastic and leptite gneisses (PRS) inRhodopes are analogs to: augen gneisses and lep-tites from “Lower group of Pangaion Unit” (Papan-ikolaou, Papadopoulos, 1981) or Nevrokopi unit —(Zagorchev, 1994). “Lower group of Sidironero unit”as well the leptites from “Lower tectonic units” inEastern Rhodopes (Mposkos, 1989) also correspondto leptites of PRS.

The three lithological units from Falacron Mts.(Chatzipanagis, 1990): i) upper calcareous units —

Fig. 5. Correlation lithostratigraphic columns of the Precambrian blocks in South Bulgaria

27

Fig. 6. Correlation lithostratigraphic columns of the Precambrian blocks in the Rhodope Massif and northernGreece

marbles and dolomites; ii) transitional units — schists,marbles, gneisses, amphibolites, eclogites and iii) low-er units — monotonous quartz-feldspar muscovite andbiotite gneisses, coarse-grained augen gneisses cor-respond respectively to i) Dobrostan Marble Forma-tion, ii)Variegated Formation of RS and iii) leptitesand coarse porphyroblastic gnesses of PRS.

The information about two metamorphic units inthe Pelagonian zone (Dumurdzanov and Stojanov,1988) in Macedonia let a possibility for lithologicalcorrelation between Rhodope and Pelagonian mas-sifs. The oldest rocks — 669—713 Ma of Greece (An-ders et al., 2005) are a part of the same metamorphicbasement.

It is reasonable also to search for a lithologicalrelation between Rhodope Massif and Apuseni Mts.(Romania). After a summary by Krautner (1997) thePrecambrian polymetamorphic basement is outcrop-ping in some Pre-Variscan Terranes. In Somes Ter-rane two-mica schists and leptito-amphibolite forma-

tion are assigned. Carpian Terrane, constituted of Baiade Aries Group, consists of mica-schists and carbon-ate formations, the later is an alternation of calciteand dolomite marbles, amphibolites, mica-schists andquartzites. In Codru Terrane the Codru amphiboliteFormation of 524 Ma is outcropping. Nevertheless ofcomplicate nappe system in Apuseni Mts., a litholog-ical similarity between mentioned above formationsand Rhodopian Supergroup appears.

Conclusion

1. The actual lithological, petrological and tectoni-cal analysis confirms that the Precambrian metamor-phic complexes in Southern Bulgaria are one com-mon lithological system, composed of two metamor-phic complexes that are different in lithology andage: Prarhodopian and Rhodopian Supergroups withrelatively well preserved stratigraphic sequence.

28

Fig

. 7.

Map

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ion

of t

he m

etam

orph

ic c

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2. The Prarhodopian Supergroup is an infracrustalgneiss complex from ancient continental crust withthe following lithostratigraphic sequence from baseto top: biotite gneisses — Orlovo Formation, leptitegneisses — Gornoyuroutsi Formation, porphyroblas-tic gneisses — Punovo Formation and does not con-tain variegated formations. Part of the Prarhodopi-an Supergroup are also the analogous gneiss forma-tions - Boykovo and Bogoutevo Formations (corre-lates to Orlovo Formation) and Bachkovo Formation(corresponding to Gornoyuroutsi Formation) whichare placed in the cores of the anticline structuresand have been described earlier as a part of the Rhodo-pian Supergroup.3. Transgressively deposited Rhodopian Supergroupis composed mainly of variegated Loukovitsa For-mation (with correlates are Vacha and ChepelareFormations) and marble-schists Asenitsa Group withDobrostan and Belashtitsa Formations.

4. The Ophiolite association is stratigraphically re-lated to the Variegated Formation only.5. The methamorphic rocks from Sredna Gora zoneand Ograzhdenian Supergroup are composite com-plexes, that contain formations, which lithologicallybelong either to Prarhodopian or to Rhodopian Su-pergroup.6. The main structural plan of the crystalline base-ment of the Rhodope massif, demonstrated by thedistribution of the lithological formation, is charac-terized by fold structures (Fig. 7).

The correlations between crystalline blocks inBalkan terranes is a main aim for the regional ge-ologists. The realization is difficult because of in-dividual deformation development of every tecton-ic unit. An effort for reconstruction of the primarycomposition and stratigraphy of the lithostrati-graphical units will be favorable for interregionalcorrelation.

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Õàéäóòîâ, È., Êîë÷åâà, Ê., Äàèåâà, Ë. À., Ñàâîâ, È. 2003.Íàëè÷èå íà áîíèíèòîâ òèï ìàãìàòèçúì ñðåä ïúñòðèòåñâèòè îò Èçòî÷íèòå Ðîäîïè. — Ãåîõèì., ìèíåð. è ïåò-ðîë., 40; 55—72.

E. Êîæóõàðîâà – Ðåêîíñòðóêöèÿ íà ïúðâè÷íàòà ñòðàòèãðàôèÿ è êîðåëàöèÿ íà äîêàì-áðèéñêèòå ìåòàìîðôíè êîìïëåêñè â Ðîäîïñêèÿ ìàñèâ. Ñòðàòèãðàôñêàòà ñõåìà íà âñåêèìåòàìîðôåí êîìïëåêñ ïðåäñòàâÿ ðåàëíèòå, âèäèìè ñóïåðïîçèöèîííè îòíîøåíèÿ íà ëèòî-ëîæêèòå åäèíèöè, â êîèòî ñà îòðàçåíè ïðåòúðïåíèòå äåôîðìàöèè, íî òÿ ïî÷òè âèíàãè ïîâå-÷å èëè ïî-ìàëêî ñå ðàçëè÷àâà îò ïúðâè÷íàòà ñòðàòèãðàôñêà ïîñëåäîâàòåëíîñò. Äîñòîâåð-íîñòòà íà ìåæäóðåãèîíàëíèòå êîðåëàöèè, çàòðóäíåíè ïîðàäè òåêòîíñêèòå íàðóøåíèÿ, íå-ðàâíîìåðíèòå ïîëèìåòàìîðôíè èçìåíåíèÿ è íåñèãóðíîñòòà íà èçîòîïíèòå äàííè çà âúçðà-ñòòà íà ñêàëèòå, èçèñêâàò ìàêñèìàëíî âúñòàíîâÿâàíå íà ïðåäìåòàìîðôíèÿ âèä íà ïðîòîëè-òèòå è òåõíèòå âçàèìîîòíîøåíèÿ. Ïîäîáíà ñòðóêòóðíî-ïåòðîëîæêà ðåêîíñòðóêöèÿ å âúçìîæ-íà åäâà ñëåä íàòðóïâàíå íà íåîáõîäèìàòà è äîñòàòú÷íà èíôîðìàöèÿ ÷ðåç ñïåöèàëèçèðàíè,ïîíÿêîãà ïðîäúëæèòåëíè ðàçðàáîòêè.

Àêòóàëíàòà ñòðàòèãðàôñêà ñõåìà íà ìåòàìîðôíèÿ êîìïëåêñ â Ðîäîïñêèÿ ìàñèâ è ñúñåä-íèòå îáëàñòè, ïðèëîæåíà â Ãåîëîæêàòà êàðòà íà Áúëãàðèÿ (Kozhoukharov, 1988), ñúùî òàêàïðåäñòàâÿ äíåøíèòå ñóïåðïîçèöèîííè îòíîøåíèÿ íà ëèòîñòðàòèãðàôñêèòå åäèíèöè, áåçíÿêîãà äà å ïðåòåíäèðàëà çà àäåêâàòíîñò íà ïúðâè÷íèòå. Ïðîâåäåíèòå ïåòðîëîæêè èçñëåä-âàíèÿ çà âúçñòàíîâÿâàíå íà ïðåäìåòàìîðôíèÿ ñúñòàâ íà ñêàëèòå, óòî÷íÿâàíåòî íà ñòðàòèã-ðàôñêîòî è ñòðóêòóðíî ïîëîæåíèå íà îôèîëèòîâàòà àñîöèàöèÿ è ðàçøèôðîâàíåòî íà ðåäè-öà ïîëåãíàëè ãúíêè (Æúëòè÷àëñêà, Àâðåíñêà, Àðäèíñêà, Äåáðåíñêà ñèíêëèíàëà) ïðè÷èíÿâà-ùè íà ìíîãî ìåñòà ïîâòîðåíèÿ â ëèòîëîæêèÿ ïðîôèë, íàïðàâè âúçìîæåí òîçè ïúðâè îïèòçà ðåêîíñòðóêöèÿ íà ïúðâè÷íàòà ñòðàòèãðàôèÿ è íà òàçè áàçà ïðîâåæäàíå íà êîðåëàöèÿ ñúññúñåäíèòå îáëàñòè.

Ðåçóëòàòèòå îò ëèòîëîæêèÿ è ñòðóêòóðåí àíàëèç ñà îáîáùåíè â ñëåäíèòå ïî-âàæíè èç-âîäè:

1. Ïîòâúðæäàâà ñå íàëè÷èåòî íà äâà ðàçëè÷íè ïî ëèòîôàöèåñ êîìïëåêñà:1.1 Ïðàðîäîïñêà íàäãðóïà – äîëåí èíôðàêðóñòàëåí êîíòèíåíòàëåí êîìïëåêñ, ñúñòîÿù

ñå îò íÿêîëêîêðàòíî ïðåðàáîòåíè ìîíîòîííè ïàðà è îðòîãíàéñè, ãðàíèòîãíàéñè, ìèãìàòè-

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òè, áèîòèòîâè è ëåïòèòîâè ãíàéñè. Ëèïñâàò ïúñòðè ñâèòè ñ ìðàìîðè è îôèîëèòè. Ïðè÷èñ-ëÿâàíàòà êúì íàäãðóïàòà Ïúñòðà Áîãóòåâñêà ñâèòà îò Áåëîðå÷êîòî ïîäóâàíå å â òåêòîíñêîïîëîæåíèå, èçïúëâà ïîëåãíàëà ñèíêëèíàëà è íå ïðèíàäëåæè êúì Ïðàðîäîïñêàòà íàäãðóïà.Êîìïëåêñúò ñå ðàçêðèâà â ÿäðàòà íà ãîëåìèòå ïîçèòèâíè ñòðóêòóðè, èçâåñòíèòå êàòî Áåëî-ðå÷êî ïîäóâàíå, Òèíòÿâñêî ïîäóâàíå, Êåñåáèðñêà àíòèêëèíàëà, Ìàäàí-Äàâèäêîâñêî ïîäó-âàíå, Ñåâåðíîðîäîïñêà, Ñðåäíîðîäîïñêà è Þæíîðîäîïñêà àíòèêëèíàëè, þãîçàïàäíàòà ÷àñòíà Çàïàäíèòå Ðîäîïè è Ïèðèí.

Åòàëîííàòà ñòðàòèãðàôñêà ïîñëåäîâàòåëíîñò íà Ïðàðîäîïñêàòà íàäãðóïà å ïðåäñòàâåíàíàé-äîáðå â Áåëîðå÷êîòî ïîäóâàíå îòäîëó íàãîðå: à. Îðëîâñêà ñâèòà — ïðåîáëàäàâàùèáèîòèòîâè ãíàéñè, ñ êîðåëàòè Áîéêîâñêà è Áîãóòåâñêà ñâèòà îò Öåíòðàëíèòå, Çàïàäíè Ðî-äîïè è Ïèðèí; á. Ãîðíîþðóøêà ñâèòà — ëåïòèòîâè ãíàéñè ñ êîðåëàò Áà÷êîâñêà ñâèòà îòÖåíòðàëíè, Çàïàäíè Ðîäîïè è Ïèðèí è â. Ïúíîâñêà ñâèòà ñúñ ñïîðàäè÷íî ðàçâèòèå âÖåíòðàëíèòå è Çàïàäíè Ðîäîïè, íî øèðîêî â Ñàêàðñêèÿ áëîê, ïðåìèíàâàùà â Êîíñòàíòè-íîâñêàòà ìåòàêîíãëîìåðàòíà ñâèòà;

1.2 Ðîäîïñêà íàäãðóïà — ãîðåí òðàíñãðåñèâíî îòëîæåí ñóïðàêðóñòàëåí âóëêàíîãåííî-ñåäèìåíòåí êîìïëåêñ, ñúñòîÿù ñå îñíîâíî îò äâå ëèòîôàöèàëíè åäèíèöè: à. Ïúñòðà ñâè-òà: òîëåèòîâè âóëêàíèòè è òóôè, ñåðïåíòèíèòè, ãàáðà (Îôèîëèòîâà àñîöèàöèÿ), ïåëèòè,êâàðöèòè, âàðîâèöè, ìåòàìîðôîçèðàíè â àìôèáîëèòè, ïèðîêñåíèòè, åêëîãèòè, ãðàíàòîâèëåðöîëèòè, ñëþäåíè øèñòè, êàëêîøèñòè è ìðàìîðè, ïðåäñòàâåíè â Ëóêîâèøêàòà, Âú÷àí-ñêàòà, ×åïåëàðñêàòà, Ãíåçäàðñêàòà è Æúëòè÷àëñêàòà ñâèòà è á. Êàðáîíàòíà ñâèòà —äîìèíèðàíà îò êàëöèòîâè è äîëîìèòîâè âàðîâèöè, ïðîñëîÿâàùè ñå ñ ïåëèòè, ìåòàìîðôî-çèðàíè â ìðàìîðè è øèñòè, ïðåäñòàâåíè â Àñåíîâãðàäñêàòà ãðóïà (Äîáðîñòàíñêà è Áåëà-ùåíñêà ñâèòà.)

2. Ïúñòðàòà ñâèòà å ðàçâèòà â äâà ëèòîëîæêè òèïà: à. Çàïàäíîðîäîïñêè (Ñàòîâ÷àíñêè) âðàéîíè ñ àêòèâíà âóëêàíñêà äåéíîñò, êúäåòî â íèñêèòå ñòðàòèãðàôñêè íèâà ïðåîáëàäàâàòâóëêàíèòè è òåõíèòå òóôè, à íîðìàëíàòà ñåäèìåíòàöèÿ å ñïîäàâåíà, ïîðàäè êîåòî âàðîâè-öèòå è ïåëèòèòå ñà ðåäóöèðàíè, à íà ìåñòà äîðè ëèïñâàò è á. Öåíòðàëíîðîäîïñêè (Ëóêî-âèøêè), ïðåîáëàäàâàò ñåäèìåíòèòå, à íèâàòà íà âóëêàíèòèòå â ñúâðåìåííèÿ ïðîôèë ñà ìàð-êèðàíè îò òúíêè àìôèáîëèòîâè ïëàñòîâå;

3. Ðîäîïñêàòà îôèîëèòîâàòà àñîöèàöèÿ å õåòåðîãåííà áàçèò-óëòðàáàçèòîâà ôàðìàöèÿ,êîÿòî èìà îïðåäåëåíî ñòðàòèãðàôñêî ïîëîæåíèå â íèñêèòå íèâà íà Ïúñòðàòà ñâèòà — Ðî-äîïñêà íàäãðóïà. Íåéíèÿò ãåíåçèñ å ñâúðçàí ñ âåðîÿòíà îáäóêöèÿ íà ôðàãìåíòè îò ñåðïåí-òèíèçèðàíà îêåàíñêà êîðà â îêðàéíè êîíòèíåíòàëíè áàñåéíè â ñóïðà-ñóáäóêöèîííà îáñòà-íîâêà. Ñåðïåíòèíèòèòå ñà ïîêðèòè îò íèñêîêàëèåâè òîëåèòîâè âóëêàíèòè è òåõíèòå òóôè èòóôèòè. Íåîïðîòåðîçîéñêèÿò áàçè÷åí âóëêàíèçúì å àâòîõòîíåí, ôîðìèðà ñóáèíòðóçèâíèìàëêè òåëà è äàéêè, ñå÷àùè ëåïòèòîâèòå ãíàéñè è âêëþ÷âàùè êñåíîëèòè îò òÿõ;

4. Åêëîãèòèòå è ãðàíàòîâèòå ëåðöîëèòè ñà êîðîâè ìåòàìîðôíè ïðîäóêòè íà îôèîëèòèòåè ñà îáðàçóâàíè “in situ” â òåñíè çîíè íà òðèåíå â îáñòàíîâêà íà ëîêàëíî ïîâèøåíè òåìïå-ðàòóðà íàëÿãàíå ïðè ôîíîâ ìåòàìîðôèçúì â àìôèáîëèòîâ ôàöèåñ. Ëèïñâàò äàííè ìåòà-ìîðôíèÿò êîìïëåêñ äà å ïîïàäàë â ñóáäóêöèîííà çîíà. Çàïàçåíàòà äîáðà ñòðàòèôèöèðà-íîñò íà Ðîäîïñêàòà íàäãðóïà, íåíàðóøåíèòå äîáðå î÷åðòàíè ëèíåéíè ãúíêîâè ñòðóêòóðè èëèïñàòà íà äàííè öåëèÿò êîìïëåêñ äà å ïðåìèíàë ïðåç âèñîêè Ò/Ð óñëîâèÿ íà êðèñòàëèçà-öèÿ è âïîñëåäñòâèå äà å ïðåòúðïåë òîòàëíà äèàôòîðåçà, êàêòî è íåâúçìîæíîñòòà äà å ïðî-òåêëà åäíà êúñíà ñëåäåêëîãèòèçàöèîííà ñåðïåíòèíèçàöèÿ íà îãðîìíèòå ñåðïåíòèíèòîâèìàñèâè èçêëþ÷âà ñóáäóêöèîíåí åòàï íà ìåòàìîðôíèÿ êîìïëåêñ.

5. Ìåòàìîðôíèòå ñêàëè îò Ñðåäíîãîðñêàòà çîíà è Îãðàæäåíñêàòà íàäãðóïà ñà ñúñòàâíèêîìïëåêñè îò ñêàëíè ôîðìàöèè, ñúîòâåòñòâàùè ïî ëèòîôàöèåñ íà ÷àñòè îò Ïðàðîäîïñêàòàè Ðîäîïñêàòà íàäãðóïà.