GeolCarp_Vol55_No5_397

397

THE TERTIARY EVROS VOLCANIC ROCKS (GREECE): PETROLOGY AND GEOCHRONOLOGY

GEOLOGICA CARPATHICA, 55, 5, BRATISLAVA, OCTOBER 2004

397409

Introduction

The geology of eastern Macedonia and Thrace in northeast-

ern Greece, is characterized by widespread Tertiary igneous

rocks, both volcanic and plutonic (Fig. 1). The magmatism

which produced these rocks was mostly calc-alkaline to

high-K calc-alkaline in character, with subordinate shosho-

nitic rocks. The volcanic rocks crop out mostly in the central

and eastern Hellenic Rhodope Massif (HRM) and Circum-

Rhodope Belt (CRB) (Fig. 1), and continue to the north

into Bulgarian territory (Yanev et al. 1998 and references

therein).

The volcanic products are associated with the intensive Ter-

tiary volcanic activity affected the Balkan Peninsula, and are

regarded as the result of the underthrusting of the African

plate below the southern European margin. Although the evo-

lution of the volcanism has been reconstructed in detail in the

central Aegean Sea (Innocenti et al. 1982; Fytikas et al. 1985;

Pe-Piper 1994), it has only partly been investigated (Innocenti

et al. 1984; Eleftheriadis 1995; Christofides et al. 2001) in

northeastern Greece.

Here, new petrological, geochemical, and geochronological

(K/Ar) data are presented for the Evros volcanic rocks (EVR)

in Thrace, and general aspects of their origin and evolution are

THE TERTIARY EVROS VOLCANIC ROCKS

(THRACE, NORTHEASTERN GREECE): PETROLOGY AND

K/Ar GEOCHRONOLOGY

GEORGIOS CHRISTOFIDES

, ZOLTÁN PÉCSKAY

, GEORGIOS ELEFTHERIADIS

TRIANTAFYLLOS SOLDATOS

and ANTONIOS KORONEOS

Department of Mineralogy, Petrology and Economic Geology, Aristotle University of Thessaloniki,

54124 Thessaloniki, Greece; christof@geo.auth.gr

ATOMKI, Institute of Nuclear Research, Hungarian Academy of Sciences, Bem tér 18/C, 4026 Debrecen, Hungary;

pecskay@moon.atomki.hu

(Manuscript received July 4, 2003; accepted in revised form April 19, 2004)

Abstract: The Tertiary Evros volcanic rocks (EVR) crop out in northeastern Greece (Thrace), in close association with

fault-controlled sedimentary basins, formed in an extensional regime. Three volcanic areas, called the Loutros-Feres-

Dadia, Kirki-Esimi and Mesti-Petrota after the corresponding basins, could be distinguished. The rock bulk chemistry

shows features of calc-alkaline to high-K calc-alkaline and, locally, shoshonitic rock series. Compositional variations

indicate magmatism of convergent margins. The EVR form lava flows, domes, dykes and abundant pyroclastics. Their

chemical composition ranges from basaltic andesite to rhyolite through andesite, trachyandesite, trachydacite and dacite.

The basaltic andesites are two-pyroxene rocks, while the andesites are either pyroxene andesites or biotite-hornblende

andesites. The trachyandesites and trachydacites have pyroxenes and biotite. The dacites mostly have biotite and horn-

blende and locally pyroxene. Rhyolites have mainly biotite and rarely hornblende. All the rocks are porphyritic with

glassy, holocrystalline or semicrystalline textures. The K/Ar ages range from 33.4 to 19.5 Ma, establishing an Oligocene

(33.425.4 Ma) and an Early Miocene (22.019.5 Ma) volcanic activity. Intercalations, however, of pyroclastic materi-

als with Priabonian clastic sediments indicate that the volcanic activity started earlier than the Oligocene. Two main

groups of rocks have been distinguished, the PxBt group comprising basaltic andesite, pyroxene andesites, trachyandesites

and trachydacites, and the HblBt group comprising hornblende-biotite andesite, dacite and rhyolite. On the basis of the

rock chemistry two parallel, sub-parallel or cross-cutting geochemical trends are distinguished, indicating different

evolutionary histories for them. The Sr isotopic composition differs in the two groups, with Sr I.R. ranging between

0.7057 and 0.7074 in the PxBt group, and between 0.7071 and 0.7080 in the HblBt group. The PxBt group was evolved

through an open system process (MFC mixing plus fractional crystallization) in which basaltic andesite and trachydacite

represent the basic and the acid end-members respectively. Although assimilation plus fractional crystallization is not

excluded, MFC between a basic end-member, similar to the HblBt andesites, and an acid end-member, having rhyolitic

composition, is suggested as a possible process for the evolution of the HblBt group. The parental magmas for the

evolution of the PxBt group originate in an inhomogeneous and strongly metasomatized mantle through a slight modifi-

cation of a primary basaltic melt. The parental magma for the evolution of the HblBt group could be a hybrid magma of

the PxBt group, which evolves, under different conditions, to give the HblBt group rocks. Although the involvement of

a mantle component cannot be excluded for the origin of the rhyolitic melts, partial melting of crustal material (amphibo-

lite, basalt, andesite, gneisses, pelites, greywackes), under various P-T conditions, are responsible for the genesis of

melts similar to the less evolved rhyolites.

Key words: Greece, Evros, geochemistry, petrology, volcanics, K/Ar age.

398

CHRISOFIDES, PÉCSKAY, ELEFTHERIADIS, SOLDATOS and KORONEOS

considered, aiming at the understanding of the volcanic histo-

ry of the area.

Geological setting

The EVR, which are named after Evros River (Fig. 1) and

the Evros County, crop out in the eastern parts of the HRM

and CRB in Thrace. The HRM is a polymetamorphic terrain

that extends along the Greek-Bulgarian borders and covers

eastern Macedonia and Thrace in Greece, and southern Bul-

garia. The HRM is situated between the Balkan belt to the

north and the Dinarides-Hellenides to the south-southwest. It

is bounded to the west by the Serbo-Macedonian Massif

(SMM), a structurally complex domain of predominantly

high-grade metamorphic rocks and numerous granitoids

mainly of Jurassic and Tertiary age. The HRM and SMM are

now regarded as a single major element of the Tethyan oro-

genic system (Burg et al. 1995) formed through deep level

subductionaccretion processes acting on Paleozoic-Mesozo-

ic precursors (Barr et al. 1999). The interpretation of Rhodope

as a fragment of pre-Alpine age (possibly of Hercynian or

Precambrian) is rejected (Ricou et al. 1998).

The CRB comprises a Late Paleozoic and Mesozoic mar-

ginal volcano-sedimentary narrow belt consisting of phyllites,

schists, crystalline limestones and marbles (Kauffman et al.

1976; Kockel et al. 1977; De Wet et al. 1989; Ioannidis

1998), bordering both the HRM to the southeast and the

Fig. 1. Geological sketch map of the central eastern Hellenic Hinterland. AZ Axios (Vardar) Zone; CRB Circum-Rhodope Belt;

SMM Serbo-Macedonian Massif; HRM Hellenic Rhodope Massif; UTU Upper Tectonic Unit; LTU Lower Tectonic Unit.

Plutonic and volcanic outcrops are shown. EVR Evros volcanic rocks. F.Y.R.O.M. Former Yougoslavian Republic of Macedonia.

SMM to the west (Fig. 1). It was subjected to a Late Jurassic

Early Cretaceous low-grade metamorphism associated with the

main CRB foliation, subparallel to the bedding (Vergely

1984). Ricou et al. (1998) reject the concept of a Mesozoic

CRB as a stratigraphic Rhodope cover. Instead they support

the idea of a two-fold classification as roof greenschists (Alexan-

droupolis and Mandrica schists roofing the eastern Rhodope)

and the western greenschists (Mesozoic Chalkidiki sediments).

Major thrust zones separate HRM into distinct geological

units. On the basis of geological and petrological criteria, the

western and central HRM is distinguished into an Upper Tec-

tonic Unit (UTU) or Sideronero Unit and a Lower Tectonic

Unit (LTU) or Pangeon Unit (Papanikolaou & Panagopoulos

1981; Mposkos 1989; Kilias & Mountrakis 1990), separated

by an approximately SSENNW striking thrust plane, the Nes-

tos thrust.

The metamorphic basement of the HRM is made up of

schists, gneisses and amphibolites, marbles and ultramafic

rocks. Its metamorphic history is rather complicated and is

characterized by an ultra high pressure metamorphism (Mpos-

kos et al. 2001; Liati et al. 2002), an eclogite-facies metamor-

phism, subsequently overprinted in the amphibolite-facies

metamorphism, followed by a greenschist-facies metamor-

phism (Liati & Seidel 1996 and references therein). The HRM

was not metamorphosed as a single geotectonic element but

rather consisted of different fragments subducted and exhumed

at different times (Liati et al. 2002). The metamorphism in

eastern Rhodope is significantly older (ca. 74 Ma) than in the

399

THE TERTIARY EVROS VOLCANIC ROCKS (GREECE): PETROLOGY AND GEOCHRONOLOGY

central part of it. The metamorphic basement of the HRM, par-

ticularly the eastern part, and CRB is covered by a clastic Lu-

tetian sequence consisting of basal conglomerates, sandstones

and nummulitic limestones.

A characteristic feature of the Tertiary evolution of the

HRM and the CRB is the presence, at their margins and on

them, of fault-controlled (depression) sedimentary basins,

formed under tensional tectonics, following an intense Eocene

orogenic phase, which affected all the Inner Hellenides. The

formation of the basins, with which the Tertiary magmatism is

associated, started in the Middle Eocene (Lutetian) and lasted

up to the Pliocene. The Evros area contains three large basins,

Maronia-Petrota, Kirki-Esimi and Feres-Soufli-Dadia (Fig. 2),

as well as a number of smaller basins (Papadopoulos 1979,

1980, 1982).

The change of the paleogeographical conditions, in the vari-

ous basins, started in the Late Eocene. The environment in the

Maronia-Petrota Basin was transitional and sub-aerial, and the

deposition of volcanic products continued right through the

Oligocene (Innocenti et al. 1984). The volcanic products com-

prise a series consisting of pyroclastic layers with intercala-

tions, at its basal part, of conglomeratic layers composed of

volcanic elements associated locally with lahars. In the upper

part of the series, lava flows predominate, overlying an ignim-

britic sequence (Frass et al. 1990).

In the Kirki-Esimi Basin, strong subsidence conditions per-

sist, with deposition of volcano-sedimentary products (marly

sandstones and claystones of Priabonian age dominate), fol-

lowed in places by intercalations of volcanic products, repre-

sented mainly by lava flows, domes, associated with rare vol-

canic agglomerates (Innocenti et al. 1984).

The Feres-Soufli-Dadia Basin is the widest and the most af-

fected by subsidence. Its geology comprises a Lutetian basal

clastic sequence, Priabonian sandstones, marls, and conglom-

erates, and an Oligocene sequence of marly and clayey sedi-

ments. The volcanic products, mostly sub-aqueous and sub-

aereal pyroclastic deposits, are intercalated in the Priabonian

and Oligocene sequence. Several ignimbritic units are seen in

the Oligocene sequence as well as lava flows, domes and

dykes.

Tertiary magmatic activity

The volcanic rocks are widespread in northeastern Greece

particularly in eastern Macedonia and Thrace (Fig. 1). Two

major volcanic provinces have been defined, one north of

Xanthi town, known as the Kalotycho volcanics (Eleftheriadis

& Lippold 1984; Innocenti et al. 1984; Eleftheriadis 1995),

and one in western Thrace, known as the Evros volcanic rocks

(EVR) (Rentzeperis 1956; Sideris 1973; Eleftheriadis et al.

1989; Frass et al. 1990; Karafoti & Arikas 1990; Arikas &

Voudouris 1998; Christofides et al. 2001).

According to geochronological and stratigraphic data the

volcanism in the area started in Middle Eocene times produc-

ing abundant pyroclastics and ignimbrites, although a few

Fig. 2. Geological map of the Evros volcanic rocks. K/Ar ages are shown.

400

CHRISOFIDES, PÉCSKAY, ELEFTHERIADIS, SOLDATOS and KORONEOS

andesitic products with supposed Priabonian age, crop out in

Feres-Dadia area (Skarpelis et al. 1987). The volcanic activity

culminated during the Late Oligocene (Innocenti et al. 1984)

with eruption of high-K calc-alkaline to shoshonitic volcanics

of mostly intermediate composition. Pyroclastics, interlayered

with Oligocene sediments, rhyolitic ignimbrites a few hun-

dreds meters thick, breccias, lava flows, dykes and domes of

basaltic andesite to rhyolite composition are also present. Vol-

canism ended in the Miocene with both acid and intermediate

volcanic products (Eleftheriadis et al. 1994; Innocenti et al.

1994; Vlahou et al. 2001).

The volcanism of northeastern Greece, including the EVR,

was developed after the thickening/uplift of the Hellenic Oro-

gen and its subsequent extensional collapse. It shows a bimo-

dal character, in the sense that intermediate (andesitic) and

acid (rhyolitic) compositions dominate while compositions in

between them (latitic) are restricted. This bimodal character is

atypical for convergent plate margins but common for mag-

matism related to lithospheric delamination or continental rift-

ing (Yanev et al. 1998). If the volcanic products in the Bulgar-

ian Rhodope Massif (Harkovska et al. 1989) and the Aegean

volcanism (Fytikas et al. 1985) are considered, it is obvious

that there is a southward migration of the volcanic activity.

Pamiæ et al. (2002 and references therein) reviewing the

geophysical, geological, petrological and geochemical data of

the Late Paleogene magmatic associations of the Periadriatic

SavaVardar Magmatic Belt (PSVMB), including the Helle-

nides, support the view that the geodynamic evolution of

these magmatic associations was related to the Africa-Eurasia

Suture Zone, which was dominated by break-off of the sub-

ducted lithospheric slab of the Mesozoic oceanic crust, at

depths of 90100 km.

Petrography

The EVR comprise intermediate and acid rocks (Fig. 2),

which have been classified according to the TAS (Total Alkali

vs. Silica) diagram of Le Maitre (1989) as basaltic andesites,

andesites, trachyandesites, dacites, trachydacites, and rhyo-

lites (Fig. 3). The trachyandesites are further subdivided into

Fig. 3. Total alkali vs. silica (TAS) classification of the Evros vol-

canic rocks (after Le Maitre 1989).

Fig. 4. a Columnar jointing in rhyolites from Loutros-Feres-Dadia area. b Lahar from Mesti area.

latites (5 samples) and benmoreites (2 samples) according to

O and K

O contents. Here, we use the general term tra-

chyandesites. For simplicity three volcanic areas could be dis-

tinguished (Fig. 2): a Loutros-Feres-Dadia, b KirkiEsi-

mi, c Mesti-Petrota, corresponding to the host depression

basins. In each area both intermediate and acid lavas are

present in association with pyroclastics. In the northeastern

and southwestern parts of the Loutros-Feres-Dadia area the

acid rocks, mostly rhyolites, dominate while in the middle

part andesite and to a lesser extent dacite are the prevailing

rock-types. Lava flows and domes, in some cases exhibiting

columnar jointing (Fig. 4a), are very often associated with py-

roclastics. The latter, in most cases, are intruded or covered by

the former. In the Kirki-Esimi area the most widespread rock

is andesite, often with columnar jointing. Rhyolites are

present in the form of a dense net of NWSE trending dykes

in the northeastern part of the area. The overall width of the

dykes varies from a few tens of centimeters to hundreds of

meters whereas their length extends from tens of meters to

some kilometers. Dacites occur mostly in the eastern part of it,

west of Esimi village. In the Mesti-Petrota area, andesite is

again the prevailing rock followed by dacite and rhyolite.

401

THE TERTIARY EVROS VOLCANIC ROCKS (GREECE): PETROLOGY AND GEOCHRONOLOGY

Fig. 5. Microphotographs from the Evros volcanic rocks. a Pyroxene andesite (crossed Nicols); b Hornblende-biotite andesite

(crossed Nicols); c Rhyolite with perlitic texture (parallel Nicols); d Rhyolite with sphaerolitic texture (parallel Nicols).

Rhyolitic ignimbrites, strongly welded, tuffs and lahars

(Fig. 4b) are widespread.

All rocks show porphyritic texture with groundmass rang-

ing between 40 and 80 wt. %. Phenocrysts are more abundant

(20 to 60 wt. %) in basaltic andesites and andesites than in

dacites and rhyolites (30 to 50 wt. %). Basaltic andesites con-

tain mainly plagioclase (An

) and clino- and orthopy-

roxene phenocrysts, set in a semicrystalline to hollocrystalline

groundmass (Fig. 5a). Andesites are distinguished into two

groups namely the pyroxene andesites and the biotite-horn-

blende andesites (Fig. 5b). Hornblende-biotite andesites are

found mainly in the Kirki-Esimi and Loutros-Feres-Dadia ar-

eas. Trachyandesites and trachydacites have pyroxenes and bi-

otite. Dacites and rhyolites consist of plagioclase (An

sanidine (Or

7565

), quartz, biotite and subordinate hornblende

set in a glassy or semiglassy matrix, which very often exhibits

very nice perlitic and sphaerolitic textures (Fig. 5c,d). Apatite,

titanite and zircon are accessories in all rocks. More informa-

tion on the petrography and geology of the EVR can be found

in Rentzeperis (1956).

Two groups of rocks could be distinguished, on the basis of

their mineralogy. The first group consists of the basaltic

andesites, the pyroxene andesites, the trachyandesites and the

trachydacites and it will be hereafter referred to as the PxBt

group since it is characterized by the presence of

pyroxenes±biotite. The second group comprises the biotite-

hornblende andesites, the dacites and the rhyolites, and will

be referred to as the HblBt group.

Analytical techniques

The rock analyses were performed by XRF following

Browns et al. (1973) method. Pressed pellets were used. The

operating conditions were 60 kV and 40 mA. A Cr tube was

used for major elements, a Rh tube for Nb, Zr, Y, Sr and Rb,

and a Au tube for the other trace elements.

Minerals were analysed by Energy Dispersive Spectrometry

(EDS) at the laboratory of Electron Microscopy, University of

Thessaloniki, Greece. Mineral phases were imaged with back-

scattered electrons (BSE) and quantitatively analysed using a

LINK AN 1000 EDS microanalyser attached to a JEOL JSM-

840 Scanning Electron Microscope. The operating conditions

were 15 kV accelerating potential, beam current 3 nA, surface

electron beam 1 µm

and counting time 80 seconds. The ZAF-

4/FLS software provided by LINK was used for corrections.

Minerals (albite, orthoclase, diopside, wollastonite, olivine,

periclase) and pure metals were used as standards.

K/Ar age determinations were performed at the ATOMKI

Institute for Nuclear Research of the Hungarian Academy of

Sciences, Debrecen. Both whole rock (lavas and a few tuffs)

and biotite separates were analysed.

402

CHRISOFIDES, PÉCSKAY, ELEFTHERIADIS, SOLDATOS and KORONEOS

Table 1: K/Ar dating of selected samples from the Evros volcanic rocks.

Representative rock samples of about 1 kg each were col-

lected, on the basis of their freshness and purity. After crush-

ing, approximately 20 g of the 300200 µm size fraction was

taken, washed and oven dried. A portion of it was ground in

an agate mortar and used for potassium analysis. Powdered

samples were treated with a mixture of acids (HF, HNO

and

) in teflon beakers and finally dissolved in 0.2 M HCl.

The potassium analysis was carried out by flame photometry

with a Na buffer and Li internal standard. Multiple runs of in-

ter-laboratory standards (Asia 1/65, LP-6, HD-B1) indicated

the accuracy and reproducibility to be within 23 %.

For argon analysis the samples were wrapped in aluminium

foil and copper sieve, preheated for about 24 h at 150200

in a vacuum. The argon was extracted at about 1500

C in Mo

crucibles, in a previously backed stainless steel vacuum sys-

tem. Reactive gases were purified by Ti and SAES getters and

liquid nitrogen traps. Argon was analysed using an isotope di-

lution method (

Ar spike was added from gas pipette system)

in a 15 cm radius sector-type mass spectrometer, used in static

mode, with a single collector system designed and constructed

by Balogh (1985), at the Institute of Nuclear Research of the

Hungarian Academy of Sciences (ATOMKI), Debrecen, Hun-

gary. Carefully checking of mass discrimination of the mass

spectrometer is routinely carried out with atmospheric argon

before the samples are run in the mass spectrometer. Details of

the instruments, the applied methods and results of calibration

have been described elsewhere (Balogh 1985).

Atomic constants suggested by Steiger & Jäger (1977) were

used for calculating the ages. All analytical errors represent

one standard deviation (i.e. 68 % analytical confidence level).

Since we base our analytical errors on the long term stability

of instruments and on the deviation of our results obtained on

standard samples from the interlaboratory mean the analytical

errors are likely to be overestimated.

K/Ar geochronology

The K/Ar ages obtained range from 33.4 to 19.5 Ma (Fig. 2;

Table 1), which enabled us to broadly distinquish two periods

of volcanic activity: a) in the Oligocene (33.425.4 Ma) and

b) in the Early Miocene (22.019.5 Ma). K/Ar ages reported

by Innocenti et al. (1984), range between 33 and 24 Ma. Mi-

ocene ages are reported for the first time for the EVR. Howev-

er, volcanic activity of this age is documented by K/Ar and

Rb/Sr dating on both whole rock and minerals on Samothraki

Island (Fig. 1) (Eleftheriadis et al. 1994; Vlahou et al. 2001)

and on Limnos Island (Innocenti et al. 1994) in the northern

Sample

Rock-type

Area*

SiO

(wt.%)

Dated

fraction**

Ar rad %

Ar rad

(ccSTP/g)

´ 10

K/Ar age

(Ma)

± Error

FLE3

Basaltic andesite

LFD

53.87

w.r.

0.80

45.0

0.613

19.60

0.86

FKR40

Basaltic andesite

LFD

54.98

w.r.

1.01

64.4

1.259

31.66

1.26

MES3

Basaltic andesite

55.77

w.r.

1.44

59.2

1.320

29.12

1.18

FG101

Andesite (Px)

LFD

55.53

w.r.

1.73

37.4

1.415

20.92

1.00

FKP30

Andesite (Px)

LFD

57.49

w.r.

2.13

38.5

2.517

30.15

1.42

MAA1

Andesite (Px)

57.90

w.r.

1.75

76.3

1.948

28.39

1.09

MSR12

Andesite (Px)

58.61

w.r.

1.59

42.6

1.365

21.92

0.99

CEP16

Andesite (Px)

58.90

w.r.

1.81

47.7

1.926

27.20

1.17

FK31

Andesite (Bt-Hbl)

LFD

60.40

w.r.

2.52

79.5

2.837

28.73

1.10

MSR13

Andesite (Bt-Hbl)

60.73

w.r.

1.64

36.7

1.628

25.42

1.22

FT2

Andesite (Bt-Hbl)

LFD

61.16

w.r.

2.09

75.6

2.646

32.29

1.24

AK6

Andesite (Bt-Hbl)

62.25

w.r.

1.74

72.7

2.171

31.83

1.23

FKP31

Trachyandesite

LFD

55.12

w.r.

2.89

73.2

3.124

27.58

1.07

FP6

Trachyandesite

LFD

58.18

w.r.

1.84

68.1

2.208

30.68

1.20

FL14

Trachyandesite

LFD

59.99

w.r.

2.26

73.2

2.612

29.46

1.14

MAS20

Trachydacite

63.81

w.r.

4.26

77.3

4.988

29.89

1.15

MAS21

Trachydacite

64.10

w.r.

4.31

85.3

5.006

29.61

1.12

FI10

Dacite

LFD

65.70

w.r.

2.00

39.5

2.624

33.40

1.55

FK30

Dacite

LFD

66.79

w.r.

1.92

36.0

2.182

29.00

1.42

FLE1

Dacite

LFD

68.23

w.r.

2.39

81.1

3.026

32.28

1.23

FT1

Dacite

LFD

68.79

w.r.

1.94

59.1

2.540

33.35

1.35

CEP14

Dacite

6.05

89.2

6.984

29.44

1.11

FLK5

Rhyolite

LFD

69.22

w.r.

3.06

71.8

2.511

20.99

0.82

FPL1

Rhyolite

LFD

71.09

w.r.

3.49

69.1

3.657

26.77

1.05

FF21

Rhyolite

LFD

71.36

w.r.

3.72

71.7

3.197

21.96

0.85

FLE2

Rhyolite

LFD

71.54

w.r.

2.16

55.9

2.824

33.26

1.36

FL10

Rhyolite

LFD

71.69

w.r.

6.85

77.5

5.228

19.53

0.75

FD20

Rhyolite

LFD

72.16

w.r.

3.69

74.2

4.043

27.98

1.08

FLY1

Rhyolite

LFD

79.09

w.r.

2.71

43.3

3.248

30.58

1.37

CEP17

Rhyolite

LFD

6.65

87.1

8.009

30.70

1.16

CEP18B

Rhyolite

LFD

7.03

41.1

7.800

28.30

1.29

CEP19

Rhyolite

LFD

7.23

69.9

7.182

25.37

0.99

CEP21A

Rhyolite

LFD

6.36

87.3

7.525

30.16

1.14

CEP21B

Rhyolite

LFD

6.32

86.3

7.122

28.77

1.09

* LFD Loutros-Feres-Dadia; KE Kirki-Esimi; MP Mesti-Petrota. ** w.r. whole-rock; Bt biotite

403

THE TERTIARY EVROS VOLCANIC ROCKS (GREECE): PETROLOGY AND GEOCHRONOLOGY

Table 2: Major and trace element XRF analyses of selected samples from the Evros volcanic rocks.

Basaltic

Andesite

Trachy-

Andesite

andesite

(Px)

andesite

dacite

(Hbl-Bt)

Rock-type

Sample

FLE3

FG101

FG100

MAS20

AK3

Dacite

FT1

Rhyolite

FD20

SiO

(wt.%)

53.87

55.53

56.68

63.81

61.27

68.79

72.16

TiO

0.81

0.90

0.79

0.49

0.55

0.28

16.83

17.65

17.67

14.62

16.03

15.05

13.41

8.00

7.75

7.00

4.15

5.44

2.32

1.64

MnO

0.10

0.11

0.10

0.09

0.05

0.02

MgO

4.76

1.77

2.22

2.08

3.53

1.59

0.98

CaO

8.97

8.35

8.04

3.99

4.74

4.82

2.32

3.26

2.84

3.40

2.27

4.08

3.48

1.63

0.99

2.10

2.93

5.29

2.19

2.38

4.63

0.17

0.20

0.24

0.25

0.14

0.07

LOI

2.19

2.91

0.92

2.47

1.72

0.66

2.95

Total

99.95

100.11

99.99

99.51

99.68

99.80

100.09

Nb (ppm)

146

187

193

194

134

145

146

390

487

489

454

296

314

327

184

112

214

168

114

117

101

105

130

166

154

126

595

534

507

995

470

572

430

Aegean Sea. The products of the Oligocene volcanism are

much more widespread than those of the Miocene. However,

more, shorter, periods of activity could be distinguished, if de-

tails of the stratigraphy and the spatial distribution of the vol-

canic products are taken into account. Moreover, intercala-

tions of pyroclastic materials with Priabonian clastic

sediments indicate that the volcanic activity started earlier

than the Oligocene, possibly in the Middle Eocene.

Within a single volcanic area (basin), the maximum differ-

ence in age (w.r.) is observed in the Loutros-Feres-Dadia area,

where the age of the intermediate and acid rocks ranges be-

tween 32 and 20 Ma and 33 and 20 Ma respectively. In the

Kirki-Esimi area, the age of the intermediate rocks (no data

are available for the acid rocks) ranges between 32 and

22 Ma, and in the Mesti-Petrota area between 29 and 27 Ma.

In the last area the age of the acid rocks is about 30 Ma. It is

obvious, according to the available data, that the volcanic ac-

tivity continued up to the Miocene with the most recent volca-

nic products limited to the Loutros-Feres-Dadia area. A tem-

poral gap of about 3 Ma has been noticed between the

Oligocene and the Miocene volcanic activity.

Bimodality is present in each volcanic period, with re-

peated acid and intermediate phases having, in general, simi-

lar ages. Compared with the east Rhodope volcanism in Bul-

garia (Yanev et al. 1998) the Evros volcanism seems to follow

it. However, in the Evros area the volcanic activity continues

up to the Early Miocene. Moreover, it culminated during the

Late Oligocene.

Geochemistry

The analysed EVR have a wide spectrum of silica content,

ranging from 54 to 79 wt. % (Table 2). They show features of

orogenic volcanic rocks, such as the absence of Fe enrich-

ment, the low TiO

content (<0.90 wt. %), and the K

O/Na

ratios, which is close to unity for many silicic rocks. Their

bulk chemical compositions indicate affinities of calc-alkaline

to high-K calc-alkaline and shoshonite series (Fig. 6), charac-

teristic of subduction related rock series (Wilson 1989).

The two groups of rocks, namely PxBt and HblBt, men-

tioned in the Petrography section, clearly define two separated

geochemical trends, which could be distinguished on various

variation diagrams such as on the K

O, P

and MgO dia-

grams (Fig. 7). In the PxBt group, two samples from the Ma-

ronia area, showing shoshonite composition, deviate from the

general potash trend. In the variation diagrams all major ele-

ments, except K

O, decrease with increasing silica content in

both groups. P

behaviour is different in the two groups, in-

creasing in the PxBt and decreasing in the HblBt group. In

Fig. 8 the compositional variations of selected trace elements

are shown. The distinction of the analysed rocks into the two

above mentioned trends is obvious also in nearly all trace ele-

ment diagrams. Rb, Ba, Ce and Nd increase with silica in both

groups, although the last two show some scatter in the HblBt

group. Sr and Zr increase in the PxBt group and decreases (Sr)

or remains constant (Zr) in the HblBt group. Cu and V de-

crease in both groups. Y decreases in the PxBt group and is

405

THE TERTIARY EVROS VOLCANIC ROCKS (GREECE): PETROLOGY AND GEOCHRONOLOGY

both groups the Sr I.R. increases with silica, ranging between

0.7057 and 0.7074, and between 0.7071 and 0.7080 in the

PxBt and the HblBt group respectively.

Discussion

Mineralogy, major and trace element geochemistry, and Sr

isotope composition of the rocks investigated, tend to support

the following: i) the existence of two distinct rock groups, the

PxBt and the HblBt, which have different evolutionary paths,

ii) basaltic andesites, pyroxene andesites, trachyandesites and

trachydacites constitute the first group while the second group

comprises biotite-hornblende andesites, dacites and rhyolites.

iii) the members of each group are the results of a single evo-

lutionary process, iv) the existence of an evolutionary rela-

tionship between the two groups is ruled out as indicated by

the parallel, sub-parallel or cross-cutting trends of various ele-

ments of them.

The isotopic composition of each group favours an open

rather than a closed system process. In particular the PxBt

group could be the result of a mixing or an MFC (mixing plus

fractional crystallization) process with high r (rate of mixing

or assimilation/rate of crystallization) value, in which the ba-

saltic andesites represent the basic end-member, while the

acid end-member is represented either by the trachydacites or

by a composition close to it. The shoshonitic rocks are exclud-

ed from the above procedure. Their origin and evolution is not

discussed here due to the limited data available. However, the

origin of similar potassic rocks, reported by Soldatos et al.

(1998) from Vrondou (NE Greece) was ascribed to partial

melting of an enriched mantle wedge under different condi-

tions of pressure and/or composition. On the other hand an

AFC (assimilation plus fractional crystallization) is ruled out

since a fractionation process with low r, controlled mainly by

plagioclase accumulation, would result in decreasing of Sr to-

wards the more evolved rocks. The behaviour of MgO,

3tot

, CaO, Y and V implies the involvement of clinopy-

roxene and/or hornblende as residual phases. However, taking

into account that Al

remains generally constant and that

hornblende is absent from the liquid phase it seems more

probable that clinopyroxene, among the mafic minerals, has

played an important role during fractionation.

Before going on to discuss the evolution of the HblBt

group, it is worth noting that the extensive outcrop of the rhy-

olitic rocks argues against the genesis of the rhyolitic magma

Fig. 9. Inter-element variation diagrams for the Evros volcanic rocks. Trends are shown by shaded arrows.

406

CHRISOFIDES, PÉCSKAY, ELEFTHERIADIS, SOLDATOS and KORONEOS

through a simple fractional crystallization of an andesitic

magma. Rather it favours the existence of an anatectic rhy-

olitic magma, which could be the acid end-member mixed

with a basic end-member, having composition similar to that

of the HblBt andesites, through a possible MFC process to

give the HblBt group including the less acid rhyolites. This

means that some of the rhyolites are hybrid rocks. On the oth-

er hand the absence of mingling phenomena argues in favour

of an AFC process.

Following the previous discussion the parental magmas for

the evolution of the PxBt group are the basaltic andesite and

the trachydacite (Fig. 3) or a similar magma. The relatively

low values of Sr isotopes, the low silica content and the spider

diagram patterns of the basaltic andesite show genesis from an

enriched mantle. The precursor of the basaltic andesite mag-

mas could probably be a basaltic magma, which underplated

crust, became contaminated and underwent high pressure

fractionation (olivine, pyroxene). Fractionation took place at

the base of the crust since primary magmas usually do not

reach the earths surface in environments with thick continen-

tal crust due to their density. This explains the comparative

rarity of basaltic lavas in continental margin arcs (Wilson

1989). The trachydacite magma could not be the result of

crustal melting since its composition does not fit the field of

any experimental crustal melts (Fig. 11). Its high LILE con-

tent and its relatively high Sr isotopes suggest an origin by

partial melting of a strongly metasomatized mantle. This

means that the mantle in the area was inhomogeneous, which

has been reported by many authors (e.g. Christofides et al.

1998; Pe-Piper et al. 1998). Moreover, in the Maronia area

monzonitic rocks having high LILE values, outcrop (Papa-

dopoulou et al. 2001).

For the HblBt group evolution hornblende-biotite andesites

and rhyolites (Fig. 3) are regarded as the parental magmas.

The latter is regarded as the parental magma if the evolution

process is MFC. The hornblende-biotite andesites could also

be genetically related to an inhomogenous metasomatized

mantle by the same procedure as discussed above for the PxBt

group. Its Sr isotope composition precludes a common origin

with the basaltic andesite since melting of the same mantle

under different degree of melting would give melts with the

same isotope composition. The starting point (hornblende-bi-

otite andesites) of the trend of this group is nearly always

found on the PxBt evolution line (Figs. 7, 8, 9). Taking this

into account and the similar spider diagram patterns of the two

types of andesites, the parental magma of the hornblende-bi-

otite andesite could be a hybrid magma of the PxBt group,

which evolves, under different conditions (e.g. higher P

) to

give the HblBt group rocks.

The Sr isotopic composition of the rhyolites (I.R. ranges

from 0.7069 to 0.7080) does not exclude an origin by partial

melting of an enriched mantle. Moreover, it is widely accept-

ed that such an inhomogeneous and enriched mantle exists in

the broader area. On the other hand, for the genesis of such

rhyolitic melts, extremely large masses of this mantle, under a

very low degree of melting are needed. Hence, the origin of

Fig. 10. MORB-normalized spider diagrams (normalization after

Pearce 1983) of selected samples from the Evros volcanic rocks.

a PxBt group; b HblBt group; c comparison of andesites of

the two groups.

Fig. 11. Plot of the trachydacites and rhyolites on the Al

(Na

O+K

O+CaO)Na

O+K

OCaO+FeO+MgO diagram. Shaded

areas represent experimental melts. See text for explanation.

407

THE TERTIARY EVROS VOLCANIC ROCKS (GREECE): PETROLOGY AND GEOCHRONOLOGY

the rhyolitic melts, at least the more acid ones, could be relat-

ed to partial melting of crustal rocks.

In the Rhodope Massif and the broader area crustal rocks

having silica contents greater than 60 % exist, the Sr isotopic

ratios of which ranges between 0.7066 and 0.7372 (recalculat-

ed from Soldatos et al. (2001) on the basis of 30 Ma). Numer-

ous melting experiments are reported in the literature, which

have been carried out on rocks representing the composition

of the crust (tonalites, gneisses, basalts, andesites, amphibo-

lites, pelites, greywackes) under various P-T conditions, and

which have produced melts with variable SiO

content.

These experimental melts plot on the diagram Al

(Na

O+K

O+CaO)Na

O+K

OCaO+FeO+MgO of Fig. 11,

along with the composition of the rhyolites. The diagram

shows that a variety of rocks could give crustal melts, similar

to the rhyolites. In particular, rocks of amphibolitic and basal-

tic to andesitic composition, melted under pressure of 0.1

2.2 GPa and temperature of 9001050 °C (Beard & Lofgren

1991; Rapp et al. 1991; Rapp & Watson 1995), gneisses,

melted under pressure of 0.11.5 GPa and temperature of

8251040 °C (Beard et al. 1994; Gardien et al. 1995), as well

as pelites and greywackes, melted under pressure of 0.1

0.7 GPa and temperature of 825950 °C (Vielzeuf & Hollo-

way 1988; Gardien et al. 1995; Patino Douce & Beard 1996;

Montel & Vielzeuf 1997), can produce such melts.

Conclusions

The Evros volcanic rocks, comprising acid and intermediate

types, have chemical characteristics typical of orogenic do-

mains and belong to the calc-alkaline and high-K calc-alka-

line rock series with some samples exhibiting shoshonite

composition. They are closely associated with the formation

of fault-controlled sedimentary basins, formed in an exten-

sional regime.

Their chemical composition ranges from basaltic andesite

to rhyolite through andesite, trachyandesite, trachydacite and

dacite. The basaltic andesites have ortho- and clinopyroxene,

while the andesites are pyroxene and hornblende-biotite

rocks. The dacites have mostly biotite and hornblende. The

rhyolites have mainly biotite and rarely hornblende.

On basis of K/Ar geochronology two main periods of vol-

canic activity, an Oligocene (33.425.4 Ma) and a Early Mi-

ocene (22.019.5 Ma), could be broadly distinguished. The

volcanism should have started earlier, probably in the Middle

to Late Eocene, since volcanic products are intercalated with

Priabonian clastic sediments.

Two main groups of rocks have been distinguished, the

PxBt group with pyroxenes and biotite as the main ferromag-

nesian mineral constituents, and the HblBt group having horn-

blende and biotite. The two groups establish their own

geochemical trends, which are cross-cutting, parallel or sub-

parallel, indicating different evolutionary histories for them.

The Sr isotopic composition ranges between 0.7057 and

0.7074 in the PxBt group, and between 0.7071 and 0.7080 in

the HblBt group.

The PxBt group could be the result of an MFC process in

which basaltic andesite and trachydacite represent the basic

and the acid end-members respectively. MFC between a basic

end-member with a composition similar to that of the HblBt

andesites, and an acid end-member with rhyolitic composi-

tion, could be the possible processes for the evolution of the

HblBt group although AFC is not excluded. The parental

magmas for the evolution of the PxBt group are the products

of partial melting of an inhomogeneous and strongly metaso-

matized mantle after having been slightly modified.

The parental magma of the HblBt group could be a hybrid

magma of the PxBt group, which evolves, under different

conditions to give the HblBt group rocks. Although the in-

volvement of a mantle component cannot be excluded for the

origin of the rhyolitic melts, it is suggested that partial melting

of crustal material (amphibolite, basalt, andesite, gneisses,

pelites, greywackes) under various P-T conditions could give

melts similar to the composition of the less evolved rhyolites.

Note: This paper was presented at the XVIIth Congress of

Carpathian-Balkan Geological Association held in Bratisla-

va, SR, in September 2002.

References

Arikas K. & Voudouris P. 1998: Hydrothermal alterations and min-

eralizations of magmatic rocks in the southeastern Rhodope

massif. In: Christofides G., Marchev P. & Serri G. (Eds.): Ter-

tiary magmatism of the Rhodopian region. Acta Vulcanol. 10,

2, 353365.

Balogh K. 1985: K-Ar dating of Neogene volcanic activity in Hun-

gary. Experimental technique, experiences and methods of

chronological studies. ATOMKI Reports D/1, 277288.

Barr S.R., Temperley S. & Tarney J. 1999: Lateral growth of the

continental crust through deep level subduction-accretion: a re-

evaluation of central Greek Rhodope. Lithos 46, 6994.

Beard J.S. & Lofgren G.E. 1991: Dehydration melting and water-

saturated melting of basaltic and andesitic greenstones and am-

phibolites at 1, 3 and 6.9 kb. J. Petrology 32, 365401.

Beard J.S., Lofgren G.E., Sinha A.K.& Tollo R.P. 1994: Partial

melting of apatite-bearing charnokite, granulite and diorite:

Melt compositions, restite mineralogy and petrologic implica-

tions. J. Geophys. Res. 99, 2159121603.

Brown G.C., Hughes D.J. & Esson J. 1973: New XRF data retrieval

techniques and their application to U.S.G.S. standard rocks.

Chem. Geol. 2, 223229.

Burg J.-P., Godfriaux I. & Ricou L.E. 1995: Extension of the Me-

sozoic Rhodope thrust units in the VertiskosKerdyllion

Massifs (Northern Greece). C.R. Acad. Paris Sci. 320 (IIa),

889896.

Christofides G., Pécskay Z., Eleftheriadis G., Soldatos T. & Koro-

neos A. 2001: Petrology and K/Ar geochronology of the Ter-

tiary Evros volcanic rocks, Thrace, northeastern Greece.

PANCARDI 2001, Proc. II Abstracts, DP6-7.

Christofides G., Soldatos T., Eleftheriadis G. & Koroneos A. 1998:

Chemical and isotopic evidence for source contamination and

crustal assimilation in Hellenic Rhodope plutonic rocks. In:

Christofides G., Marchev P. & Serri G. (Eds.): Tertiary magma-

tism of the Rhodopian region. Acta Vulcanol. 10, 2, 305318.

De Wet A.P., Miller J.A., Bickle M.J. & Chapman H.J. 1989: Geol-

ogy and geochronology of the Arnea, Sithonia and Ouranopolis

intrusions, Chalkidiki Peninsula, Northern Greece. Tectono-

physics 161, 6579.

Eleftheriadis G. 1995: Petrogenesis of the Oligocene volcanics

408

CHRISOFIDES, PÉCSKAY, ELEFTHERIADIS, SOLDATOS and KORONEOS

from Central Rhodope massif (N Greece). Eur. J. Mineral. 7,

11691182.

Eleftheriadis G. & Lippolt G.J. 1984: Alterbestimmungen zum oli-

gozänen Vulcanismus der Süd-Rhodopen (Nord-Griechen-

land). Neu. Jb. Geol. Paläeont. Mon. 3, 179191.

Eleftheriadis G., Christofides G., Mavroudchiev B., Nedyalkov R.,

Andreev A. & Hristo L. 1989: Tertiary volcanics from the East

Rhodopes in Greece and Bulgaria. In: Kolkovski B. (Ed.): Pro-

ceedings of the 1

Bulgarian-Greek Symp. Smolyan 1987.

Geologica Rhodopica 1, 1, 202217.

Eleftheriadis G., Pe-Piper G., Christofides G., Soldatos T. & Esson

J. 1994: K-Ar dating of the Samothraki volcanic rocks, Thrace,

North-Eastern Aegean (Greece). Bull. Soc. Geol. Greece 30, 1,

205212.

Frass A., Hegewald S., Kloos R.-M., Tesch Ch. & Arikas K. 1990:

Geology of the Graben of Petrota (Thrace, NE Greece). In: Sol-

datos K. (Ed.): Proceedings of the 2

Hellenic-Bulgarian

Symp., Thessaloniki 1989. Geologica Rhodopica 2, 2, 5063.

Fyticas M., Innocenti F., Manetti P., Mazzuoli R., Peccerillo A. &

Villari L. 1985: Tertiary to Quaternary evolution of volcanism

in the Aegean region. In: Dixon J.E. & Robertson A.H.F.

(Eds.): The geological evolution of Eastern Mediterranean.

Geol. Soc. Spec. Publ. No 17, Blackwell Scientific Publica-

tions, 687699.

Gardien V., Thompson A.B., Grujic D. & Ulmer P. 1995: Experi-

mental melting of biotite+plagioclase+quartz±muscovite assem-

blage and implications for crustal melting. J. Geophys. Res.

100, 1558115591.

Harkovska A., Marchev P., Machev Ph. & Pécskay Z. 1998: Paleo-

gene magmatism in the Central Rhodope Area, Bulgaria A

review and new data. In: Christofides G., Marchev P. & Serri

G. (Eds.): Tertiary magmatism of the Rhodopian region. Acta

Vulcanol. 10, 2, 199216.

Harkovska A., Yanev Y. & Marchev P. 1989: General features of

the Paleogene orogenic magmatism in Bulgaria. Geol. Balcani-

ca 19, 1, 3772.

Innocenti F., Kolios N., Manneti P., Mazzuoli R., Peccerillo A., Rita

F. & Villari L. 1984: The evolution and geodynamic signifi-

cance of the Tertiary orogenic volcanism in Northeastern

Greece. Bull. Volcanol. 47I, 2537.

Innocenti F., Kolios N., Manneti P., Rita F. & Villari L. 1982: Acid

and basic Late Neogene volcanism in central Aegean Sea: its

nature and geotectonic significance. Bull. Volcanol. 45, 8797.

Innocenti F., Manneti P., Mazzuoli R., Pertusati P., Fytikas M. &

Kolios N. 1994: The geology and geodynamic significance of

the island of Limnos, North Aegean Sea, Greece. Neu. Jb.

Geol. Paläeont. Mh. 11, 661691.

Ioannidis M.N. 1998: Geological investigation of the Neo-Palaeo-

zoic to Lower Jurassic meta-sediments and the Upper Jurassic

limestones of Nea Makri, Alexandroupolis, Evros County. Un-

publ. Ph.D. thesis, Aristotle University of Thessaloniki 1190

(in Greek with English summary).

Karafoti M. & Arikas K. 1990: Petrography and geochemistry of Ter-

tiary volcanic rocks between Loutra and Fere (Thrace, northeast-

ern Greece). In: Soldatos K. (Ed.): Proceedings of the 2

Hellenic-Bulgarian Symp., Thessaloniki 1989. Geologica

Rhodopica 2, Aristotle University Press, Thessaloniki, 2, 227240.

Kauffman G., Kockel F. & Mollat H. 1976: Notes on the strati-

graphic and paleogeographic position of the Svoula formation

in the innermost zone of the Hellenides (Northern Greece).

Bull. Soc. Géol. France 18, 2, 225230.

Kilias A. & Mountrakis D. 1990: Kinematics of the crystalline se-

quences in the Western Rhodope massif. In: Soldatos K. (Ed.):

Proceedings of the 2

Hellenic-Bulgarian Symp., Thessaloniki

1989. Geologica Rhodopica 2, 2, 100116.

Kockel F., Mollat H. & Water W.H. 1977: Erläuterungen zur geolo-

gischen karte der Chalcidiki und angrenzender gebiete

1:100,000 (Nord Griechenland). Bundesanstalt für geowissen-

schaften und Rohstoffe, Hannover.

Le Maitre R.W. 1989: A classification of igneous rocks and glossa-

ry of terms. Blackwell Scientific Publications, 1193.

Liati A. & Seidel E. 1996: Metamorphic evolution and geochemis-

try of kyanite eclogites in central Rhodope, northern Greece.

Contr. Mineral. Petrology 123, 293307.

Liati A., Gebauer D. & Wysoczanski R. 2002: U-Pb SHRIMP-dat-

ing of zircon domains from UHP garnet-rich mafic rocks and

late pegmatoids in the Rhodope zone (N Greece): evidence for

Early Cretaceous crystallization and Late Cretaceous metamor-

phism. Chem. Geol. 184, 281299.

Montel J.M. & Vielzeuf D. 1997: Partial melting of metagreywack-

es, II. Compositions of minerals and melts. Contr. Mineral. Pe-

trology 128, 176196.

Mposkos E. 1989: High-pressure metamorphism in gneisses and

schists in the East Rhodope zone (N Greece). Miner. Petrology

41, 2539.

Mposkos E., Kostopoulos D. & Krohe A. 2001: Ultrahigh-pressure

metamorphism from the Rhodope metamorphic province,

northeastern Greece: a preliminary report on a new discovery.

EUG 11. J. Conf. Abstracts 6, 341.

Pamiæ J., Balen D. & Herak M. 2002: Origin and geodynamic evo-

lution of Late Paleogene magmatic associations along the Peri-

adriaticSavaVardar magmatic belt. Geodynamica Acta 15,

209231.

Papadopoulos P. 1979: Geological map of Greece, Alexandroupolis

sheet, scale 1:50,000. IGME, Athens.

Papadopoulos P. 1980: Geological map of Greece, Ferre-Peplos

sheet, scale 1:50,000. IGME, Athens.

Papadopoulos P. 1982: Geological map of Greece, Maronia sheet,

scale 1:50,000. IGME, Athens.

Papadopoulou L., Christofides G., Bröcker M., Koroneos A., Solda-

tos T. & Eleftheriadis G. 2001: Petrology, geochemistry and

isotopic characteristics of the shoshonitic plutonic rocks from

Maronia area, West Thrace, Greece. Bull. Geol. Soc. Greece

XXXIV, 3, 967976.

Papanikolaou D. & Panagopoulos A. 1981: On the structural style of

the Southern Rhodope. Geol. Balcanica 11, 1322.

Patino Douce A.E. & Beard J.S. 1996: Effects of P, f(O

) and Mg/Fe

ratio on dehydration melting of model metagreywackes. J. Pe-

trology 37, 9991024

Pearce J.A. 1983: Role of the sub-continental lithospere in magma

genesis at active continental margins. In: Hawkesworth C.J. &

Norry M.J. (Eds.): Continental basalts and mantle xenoliths.

Shiva, Nantwich, 230249.

Peccerillo A. & Taylor T.S. 1976: Geochemistry of Eocene calc-al-

kaline volcanic rocks from Kastamonu area, Northern Turkey.

Contr. Mineral. Petrology 58, 6381.

Pe-Piper G. 1994: Lead isotopic compositions of Neogene volcanic

rocks from the Aegean extensional area. Chem. Geol. 118, 2741.

Pe-Piper G., Christofides G. & Eleftheriadis G. 1998: Lead and

neodymium isotopic composition of Tertiary igneous rocks of

northern Greece and their regional significance. In: Christofides

G., Marchev P. & Serri G. (Eds.): Tertiary magmatism of the

Rhodopian region. Acta Vulcanol. Spec. vol. 10, 2, 255263.

Rapp R.P. & Watson E.B. 1995: Dehydration melting of metabasalt

at 8-32 kbar: implications for continental growth and crust-

mantle recycling. J. Petrology 36, 891931.

Rapp R.P., Watson E.B. & Miller C.F. 1991: Partial melting of am-

phibolite/eclogite and the origin of Archean trondhjemites and

tonalities. Precambrian Res. 51, 125.

Rentzeperis P. 1956: Tertiary volcanics of Evros County. Ph.D the-

sis, Aristotle University of Thessaloniki, Greece, 182.

Ricou L.E., Burg J.-P., Godfriaux I. & Ivanov Z. 1998: Rhodope