Thematic Article Petrogenesis and tectonomagmatic significance of volcanic and subvolcanic rocks in...

The Island Arc (2005) 14, 494–516

Blackwell Science, LtdOxford, UKIARThe Island Arc1038-48712005 Blackwell Publishing Asia Pty LtdDecember 2005144494516Thematic ArticleAlbanide–Hellenide ophiolitic mélangesE. Saccani and A. Photiades

*Correspondence.

Received 23 February 2005; accepted for publication 30 August 2005.© 2005 Blackwell Publishing Asia Pty Ltd

Thematic ArticlePetrogenesis and tectonomagmatic significance of volcanic and

subvolcanic rocks in the Albanide–Hellenide ophiolitic mélanges

EMILIO SACCANI1,* AND ADONIS PHOTIADES2

1Dipartimento di Scienze della Terra, Università di Ferrara, Via Saragat 1, 44100 Ferrara, Italy (email: [email protected]) and 2Institute of Geology and Mineral Exploration (IGME), 70 Messoghion Str., 11527 Athens, Greece

Abstract Ophiolitic mélanges associated with ophiolitic sequences are wide spread in theMirdita–Subpelagonian zone (Albanide–Hellenide Orogenic Belt) and consist of tec-tonosedimentary ‘block-in-matrix-type’ mélanges. Volcanic and subvolcanic basaltic rocksincluded in the main mélange units are studied in this paper with the aim of assessing theirchemistry and petrogenesis, as well as their original tectonic setting of formation. Basalticrocks incorporated in these mélanges include (i) Triassic transitional to alkaline within-plate basalts (WPB); (ii) Triassic normal (N-MORB) and enriched (E-MORB) mid-oceanicridge basalts; (iii) Jurassic N-MORB; (iv) Jurassic basalts with geochemical characteristicsintermediate between MORB and island arc tholeiites (MORB/IAT); and (v) Jurassicboninitic rocks. These rocks record different igneous activities, which are related to thegeodynamic and mantle evolution through time in the Mirdita–Subpelagonian sector of theTethys. Mélange units formed mainly through sedimentary processes are characterizedby the prevalence of materials derived from the supra-subduction zone (SSZ) environ-ments, whereas in mélange units where tectonic processes prevail, oceanic materials pre-dominate. In contrast, no compositional distinction between structurally similar mélangeunits is observed, suggesting that they may be regarded as a unique mélange belt extend-ing from the Hellenides to the Albanides, whose formation was largely dominated by themechanisms of incorporation of the different materials. Most of the basaltic rocks surfacingin the MOR and SSZ Albanide–Hellenide ophiolites are incorporated in mélanges. How-ever, basalts with island arc tholeiitic affinity, although they are volumetrically the mostabundant ophiolitic rock types, have not been found in mélanges so far. This implies thatthe rocks forming the main part of the intraoceanic arc do not seem to have contributedto the mélange formation, whereas rocks presumably formed in the forearc region arelargely represented in sedimentary-dominated mélanges. In addition, Triassic E-MORB,N-MORB and WPB included in many mélanges are not presently found in the ophioliticsequences. Nonetheless, they testify to the existence throughout the Albanide–HellenideBelt of an oceanic basin since the Middle Triassic.

Key words: Albanides, basalt, Hellenides, ophiolitic mélange, petrogenesis.

INTRODUCTION

Ophiolites are wide spread in the Albanide–Helle-nide Orogenic Belt and are generally found in twodistinct tectonic zones: the Mirdita–Subpelagonianzone and the Vardar–Axios zone (Fig. 1). In partic-

ular, the Mirdita–Subpelagonian zone includes dif-ferent ophiolitic sequences developed in both mid-oceanic ridge (MOR) and supra-subduction zone(SSZ) settings (Beccaluva et al. 1994; Bébien et al.2000; Bortolotti et al. 2002b; Robertson 2002;Saccani et al. 2004a). Although these two ophiolitictypes were formed in distinct geodynamic set-tings, they share a common subophiolitic mélangetectonically situated at their bases (Jones & Rob-ertson 1991; Bortolotti et al. 1996; Carosi et al.

Albanide–Hellenide ophiolitic mélanges 495

1996). In addition, in the Mirdita sector (Fig. 2a)both MOR and SSZ ophiolites share a commonsupra-ophiolitic mélange (known as the Simonimélange, Bortolotti et al. 1996), which is not foundin the Hellenide sector of the belt. Many of thesemélanges can be subdivided into distinct mappableunits based on the prevalence of sedimentary ortectonic processes (e.g. Kemp & McCaig 1984;Bortolotti et al. 2003, 2004b; Photiades et al. 2003;Saccani et al. 2003).

Mélange terranes are common in suture zonesand result from a combination of tectonic andsedimentary processes operating during accretionand obduction in intraoceanic and continental mar-gin convergent settings. Mélanges usually include‘mixed up’ materials derived from both oceanic andarc domains that are deposited and/or tectonicallyemplaced in a variety of environments (e.g. trenchaxis, accretionary prism, forearc region). Accord-ing to Tankut et al. (1998), the identification ofmaterials included in mélanges may provideimportant constraints for the recognition of theirsource areas, as well as for the interpretation of

the processes of incorporation of these materialsduring mélange formation. In addition, ophioliticmélanges often include igneous material thatcannot be found within the ophiolitic sequences.The study of these materials may thus provide anumber of constraints for the magmatic and geo-dynamic evolution of the oceanic basins fromwhich ophiolites derive: from continental riftingand break-up to the development of an oceaniclithosphere, its consumption in a converging set-ting and, finally, ophiolite emplacement.

The aim of the present paper is to document theoccurrence of volcanic and subvolcanic mafic rocksin the Subpelagonian zone mélange units, fromAlbania to Greece, in order to determine the chem-istry and petrogenesis of the lavas and the originaltectonic setting in which they formed, as wellas to provide further constraints for the processesof incorporation of these materials into thesemélanges. For these purposes, the main Mirdita–Subpelagonian zone mélange units will be investi-gated; they are the Rubik complex and the Simonimélange in Albania, and the Avdella, Koziakas,Agoriani and Argolis mélanges in Greece (Fig. 1).This paper is based on new data on approximately150 mafic volcanic and subvolcanic rocks from thenorthern Mirdita area, and the Avdella and Argolismélanges, as well as on data published by theauthors on the Koziakas (Saccani et al. 2003) andAgoriani (Photiades et al. 2003) mélanges.

GEOLOGICAL SETTING

The Albanide–Hellenide Orogenic Belt is com-posed of several westward-verging tectonostrati-graphic zones having different names in Albaniaand Greece (Fig. 1). These zones are commonlyreferred to five fundamental paleotectonic settings(Beccaluva et al. 1997; Robertson & Shallo 2000;Pe-Piper & Piper 2002): (i) the Adria continentalmargin; (ii) the Jurassic Mirdita–Subpelagonianophiolitic domain; (iii) the Korab–Pelagonian con-tinental margin; (iv) the Vardar–Axios ophioliticdomain; and (v) the Serbo-Macedonian (Rhodope)continental margin. The Adria continental marginis, in turn, represented by five tectonostrati-graphic zones (Fig. 1): (i) Sazani (in theAlbanides)/pre-Apulian (in the Hellenides); (ii)Ionian; (iii) Kruja/Gavrovo–Tripolis; AlbanianAlps/Parnassus; and (iv) Krasta–Cukali/Pindos.They mainly include sequences of Triassic–Paleocene neritic–pelagic carbonates topped byEocene–Miocene siliciclastic turbidites.

Fig. 1 Simplified tectonic map of the Albanide–Hellenide OrogenicBelt showing the main tectonostratigraphic zones. Modified from Saccaniand Photiades (2004; references therein). Boxes and relative letters indi-cate the investigated areas expanded in Figure 2.

O

T

GREECE

ALBANIA

F.Y.R.O.M.

B

S

K

N

0 200 km100

V

G

Ar

Ko

P

40 N

20 24E E

Albanian

Gavrovo

Ionian

Pre-Apulian

Pin

do

s

Krasta C

ukali

Mird

ita

Subpelagonian

Korab

PelagonianAxios

Vardar

Serbo-Macedonian

Alpsa)

b)

c)

d)

e)

Parnassus

Kr

T: TropojaG: GomsiqeK: KukesB: BulqizaS: Shebenik

P: PindosV: Vourinos

O: Othrys

Mainsubpelagonianophioliticmassifs

Ko: Koziakas

Kr: Korca

Ar: Argolis

Kruja

Sazani

38 N

496 E. Saccani and A. Photiades

The Mirdita–Subpelagonian ophiolitic domain isrepresented by the Mirdita (in the Albanides)/Sub-pelagonian (in the Hellenides) zone, which consistsof Jurassic (Chiari et al. 2004; references therein)ophiolites and related sedimentary rocks, whichare overthrust on the Adria continental marginunits to the west, and on the Korab–Pelagonianzone units to the east (Bortolotti et al. 2004b; ref-erences therein).

Ophiolites are represented by distinctsequences generated in both mid-oceanic ridgebasalt (MORB) and SSZ settings (Beccaluva et al.1984, 1994; Shallo 1994; Bébien et al. 2000; Saccaniet al. 2004a). In the Albanian sector, these ophio-litic sequences are magnificently exposed in twodistinct tectonic subunits, which are known as theWestern Belt and Eastern Belt ophiolites, where

the former includes both MORB and SSZ ophio-lites, and the latter consists of SSZ sequences(Bortolotti et al. 2002b, 2004b; Saccani et al.2004a). In contrast, in Greece, a clear distinctionbetween the two ophiolitic types cannot be made(Saccani & Photiades 2004).

The MORB-type ophiolites are characterized bya stratigraphic sequence, which includes, frombottom to top: (i) lherzolitic mantle tectonites; (ii)a layered mafic–ultramafic cumulitic sequence; and(iii) a volcanic sequence represented by pillow lavabasalts with high-Ti affinity (Beccaluva et al. 1994).These ophiolitic sequences are recognized in theMirdita Western Belt and in the Pindos Massif. Inaddition, MORB-type mantle lherzolites are foundin the Koziakas and Othrys Massifs (Photiadeset al. 2003; Saccani et al. 2003; references therein).

Fig. 2 Simplified geological maps of theinvestigated areas. (a) North–central Mirdita(modified from Bortolotti et al. 2002b); EOB,Eastern Ophiolitic Belt; WOB, Western OphioliticBelt; (*), occurrence of a mid-oceanic ridgebasalt dyke intruded in the mélange matrix. (b)Pindos Ophiolitic Massif (modified from Jones& Robertson 1991). (c) Koziakas Ophiolitic Mas-sif (modified from Saccani et al. 2003); (*),occurrence of boninitic dykes cross-cutting dif-ferent tectonic slices. (d) Agoriani OphioliticMassif (modified from Photiades et al. 2003). (e)Schematic reconstructed stratigraphic column ofnorth and central Argolis Peninsula (modifiedfrom Bortolotti et al. 2003).

Tirana

PRE-KARST

Skoder

a

PESHKOPIWINDOW

RUBIKCOMPLEX

PeshkopiSIMONIMÉLANGE

*

Burrell

KORAB

MO

LAS

SE

Mantle Crust

20 km

N

Ophiolitic rocks:

WOB

EOB

CretaceousLimestones

KRASTA-CUKALI

IONIAN

Kranea

b

10 km

MOLASSE

PINDOSFLYSCH

AVDELLA MELANGE

OPHIOLITICCRUSTALSECTION

N

MOLASSE

PERIDOTITES

3 km

Vitoumas

Prodromos

Dilofo

Exalofos

Pili

Mouzaki

Glikomilia

PINDOSFLYSCH

MO

LASSE

KO

ZIA

KA

S S

ER

IES

- CH

ER

TS

PE

RID

OTITE

S

TH

YM

IAM

A

SE

RIE

S

c

N

*

4 km

N

Paliouri

MOLASSE

PINDOSFLYSCH PERIDOTITES

THYMIAMASERIES

LIME

STO

NE

S

d

Leontari

Makrirachi

Agoriani

Thrapsimi

MOLASSE

Mid Triassic - Mid JurassicLimestones(Trapezona Unit)

ophiolitic olistostromeophiolite-derived

turbidites

200m

serpentinites

dolerite and pillow lava

Triassic radiolarites

carbonateconglomerates

Post-Ypresian flysch

UPPER MÉLANGE UNIT(ILIOKASTRON & ADHERES)

MIDDLE MÉLANGE UNIT(DHIMAINA UNIT)

WEDGED MÉLANGE UNITLOWER MÉLANGE UNIT(POTAMI FORMATION)

Radiolarian cherts

Early Triassic volcanics

Pelagic limestones(Turonian-Paleocene)

Neritic limestones(L. Jurassic-Cenomanian)

e

MANTLE

MANTLE

MA

NTLE

Filira

Rubik

MÉLANGE

MÉLANGE

KO

ZIA

KA

S S

ER

IES

- LIM

ES

TO

NE

S


The SSZ-type ophiolites generally include, frombottom to top: (i) harzburgitic mantle tectoniteswith dunite and chromitite pods and lenses in theirupper part; (ii) ultramafic cumulates; (iii) maficcumulates; (iv) a sheeted dyke complex; and (v) avolcanic sequence including massive and pillowedbasalts, basaltic andesites, andesites, dacites andrhyolites showing mainly low-Ti, island arc tholei-itic (IAT) and, subordinately, boninitic (very low-Ti) affinities (Beccaluva et al. 1994, 2005; Shallo1994; Bébien et al. 2000). Boninitic rocks arealso found as dykes cutting the whole ophioliticsequence. These ophiolitic sequences extensivelycrop out in the Mirdita Eastern Belt, in the Vouri-nos Massif and in the upper part of the sequenceof the Pindos Massif. In addition, SSZ-type mantleharzburgites are found in the Koziakas and OthrysMassifs (Photiades et al. 2003; Saccani et al. 2003;references therein).

Other SSZ-type ophiolites are found in the east-ern part of the Mirdita Western Belt (Bortolottiet al. 1996) and in the Pindos Massif (Saccani& Photiades 2004). They consist of volcanicsequences where pure MORB alternate withbasalts showing geochemical features intermedi-ate between MORB and IAT and are cross-cut byvery low-Ti basaltic dykes with boninitic affinity(Bortolotti et al. 1996, 2002b; Bébien et al. 2000;Hoeck et al. 2002; Saccani et al. 2004a).

Both MORB and SSZ ophiolites are thrust ontosubophiolitic mélange units throughout, with slicesof metamorphic soles usually intercalated inbetween, and are overlain by bedded radiolarites.In the Mirdita zone, ophiolites are overlain by aLate Jurassic–Early Cretaceous, supra-ophioliticmélange (the Simoni mélange) associated withflysch deposits (the Firza flysch). In contrast, Hel-lenides ophiolites are directly topped by Eocene–Miocene molasse deposits of the Meso-Hellenictrough, which are, in turn, locally covered by Qua-ternary deposits.

Thrust relationships between ophiolites and thesubophiolitic mélange are sealed by Barremian–Senonian carbonate deposits, whereas theemplacement of the whole ophiolitic nappe issealed by the upper Tertiary transgressive‘molasse’ deposits of the Meso-Hellenic trough(Bortolotti et al. 2004b).

MIRDITA ZONE MÉLANGE UNITS (RUBIK COMPLEX AND SIMONI MÉLANGE)

In the Mirdita zone, the subophiolitic mélange isrepresented by the Rubik complex (Fig. 2a), which

consists of an assemblage of thrust sheets derivedfrom both continental and oceanic domains (Bor-tolotti et al. 1996, 2004b; Robertson & Shallo 2000).According to Bortolotti et al. (2004b; referencestherein), the general succession consists of MiddleTriassic–Jurassic carbonate sequences locallyoverlain by pelites alternating with Aalenian–Bajocian to Bathonian cherts. In addition, slicesof ‘volcano-sedimentary’ sequences (Kodra et al.1993) occur; they consist of within-plate volcanicsequences (Shallo 1992) alternating with thin-bedded Anisian cherts (Kodra et al. 1993; Borto-lotti et al. 1996). Slices of lherzolites and associatedpolymictic breccias, including, in turn, serpen-tinite, basalt and gabbro clasts set in a shalymatrix also occur. Recently, Bortolotti et al.(2004a) reported the occurrence in the subophio-lite mélange of basalts with MORB affinity alter-nating with shales and radiolarites of Late Triassicage (Marcucci et al. 1994; Chiari et al. 1996). Inaddition, slices of Late Jurassic–Early Cretaceoussedimentary rocks are found at the base of theRubik complex. They are mainly represented byless-than-200-m-thick breccias, where serpen-tinites, gabbros, sandstones, Triassic basalts,Triassic radiolarites and limestones are found asclasts and/or olistoliths in a shaly or areniticmatrix.

The Simoni mélange (Fig. 2a) and the associatedFirza flysch represent a thick sedimentarysequence overlying both the Western and EasternOphiolitic Belts (Bortolotti et al. 1996, 2004b). Thismélange unconformably overlies the cherts, or,directly, the ophiolitic volcanics (Carosi et al. 1996),and is a typical ‘block-in-matrix-type’ mélange(approximately 200–300 m thick), which includesblocks ranging from several centimeters to severalhundred meters in size, set in a well-foliated shalymatrix. Both continent- and ocean-derived rocksare represented in the blocks (Kodra et al. 1996).They include (in order of abundance) sandstones,Triassic volcanics, Triassic cherts, carbonates(similar to those found in the Rubik complex) andminor metamorphic rocks (marbles and mica-schists). The ocean-derived material is repre-sented by all the lithologies of the ophiolitesequence (Bortolotti et al. 2004b). In particular,the mantle ultramafics are generally representedby serpentinized lherzolites; volcanics include bothpillowed and massive basalts, whereas gabbrosand plagiogranite are rare. Shallo (1991) reportedthe occurrence of both high-Ti and low-Ti basalticblocks, suggesting that the source area of theSimoni mélange included ophiolites from both the


Eastern and Western Belts. Bortolotti et al.(2004b) concluded that the Simoni mélange,formed from the Late Oxfordian to Tithonian andrepresenting a syn-emplacement mélange, origi-nated after the inception of ophiolite deformation.

AVDELLA MÉLANGE

The Avdella mélange (Jones & Robertson 1991)crops out extensively below the Pindos ophiolites(Fig. 2b) and consists of slices of both ocean- andcontinent-derived rocks. The slices are set in astrongly deformed shaly matrix showing tectonicrelationships with the surrounding lithologies. Thematrix of the mélange also includes pebbly debrisflow deposits, with pebbles of basalts, cherts, lime-stones, gabbros, siliciclastic turbidites, and peri-dotites, which are the same lithologies forming thelarge tectonic slices.

Different varieties of slices can be identified onthe basis of their lithology, the most representativeconsist of (i) Late Triassic massive and pillow-lavabasalts, locally interbedded with pelagic lime-stones and cherts; (ii) thick-bedded Late Triassicand Early Jurassic pelagic limestones and associ-ated carbonate breccias; (iii) cherts; (iv) siliciclas-tic turbidites possibly originated from a successionbelonging to the Paleozoic Pelagonian basement(Jones & Robertson 1991); and (v) ophiolitesequences, where peridotites prevail, but minorslices of sheeted dyke complex and pillow-lavabasalts can also be found. Below the Avdellamélange, an assemblage of slices mainly consistingof turbidites, with ophiolitic fragments alternatingwith carbonate turbidites, has been reported byKemp and McCaig (1984) and Jones and Robert-son (1991).

KOZIAKAS MÉLANGE

The Koziakas mélange (Fig. 2c) consists of stackedthrust-bounded slices, where the lowermost sliceis represented by Triassic–Jurassic cherty lime-stones topped by cherts. The main body of thismélange is represented by well-preserved volcanicsequences associated with, but not stratigraphi-cally related to, cherts (Saccani et al. 2003; Borto-lotti et al. 2004b). Radiolarian assemblagesindicate two distinct age ranges: Middle–Late Tri-assic and Middle–Late Jurassic (M. Chiari, pers.comm., 2005). Volcanic sequences include pillowedand massive lava varieties, which are frequentlycross-cut by dykes of various nature, includingboninitic dykes. Saccani et al. (2003) recognized

three main groups of volcanic rocks: (i) transi-tional–alkaline series (basalt, basaltic andesite,trachyandesites and trachytes); (ii) MORB; and(iii) boninitic basaltic andesites and andesites.

A slice of rocks of the Early CretaceousThymiama succession occurs at the base of theKoziakas mélange and consists of arenitic tur-bidites, shales and marls, where arenites includefragments of carbonates and ophiolites (gabbros,basalts, peridotites and cherts).

AGORIANI MÉLANGE

The Agoriani mélange (Fig. 2d) consists of a tec-tonosedimentary mélange, which contains bothcontinent-derived materials and fragments ofophiolitic basalts, gabbros, harzburgites, serpen-tinites, slivers of basalts linked to radiolariancherts, as well as basaltic blocks in the sedimen-tary matrix. Photiades et al. (2003) recognizedthree main volcanic series: (i) MOR-type basaltsand basaltic andesites; (ii) MORB/IAT intermedi-ate basalts; and (iii) very low-Ti (boninitic) basalticandesites and andesites. The radiolarian chertsassociated with the basalts show both LateTriassic and Middle Jurassic ages (M. Chiari, pers.comm., 2005). No age data are available for manyMOR-type basalts, but a Late Triassic age forsome of them can be reasonably hypothesized onthe basis of close analogies existing between theseand similar rocks from other localities of the Hel-lenides (e.g. the Argolis area, Saccani et al. 2004b).

ARGOLIS MÉLANGE

The Argolis mélange represents the southeastern-most ophiolitic nappe of continental Greece(Fig. 1). This mélange can be subdivided into fourtectonic units thrust onto the Trapezona unit of thePelagonian zone (Fig. 2e). These tectonic unitsinclude (from bottom to top) the Lower (PotamiFormation), Wedged, Middle (Dhimaina), andUpper (Iliokastron and Adheres) units (Bortolottiet al. 2003).

The Lower unit (Potami Formation; Fig. 2e)unconformably lies at the top of the Trapezona unit(Baumgartner 1985) and consists of a sedimentarymélange, which contains fragments of arenites,cherts, pelagic and shallow-water limestones, ser-pentinites, basalts and boninitic-type rocks (Dostalet al. 1991; Capedri et al. 1996). According toBaumgartner (1985), the continent-derived frag-ments derive from the topmost formations of theunderlying Trapezona unit. The age of the mélange


is still undefined, but Bortolotti et al. (2004b)suggested that it should reasonably be includedbetween the Late Oxfordian–Early Kimmeridgianand the Cenomanian.

The Middle unit (also known as the Dhimainaunit and corresponding to the Migdalitsa ophioliticcomplex) consists of a stack of ophiolitic slices, upto 400 m thick. The interpretation of this unit as atectonic mélange or a true ophiolitic nappe is stillcontroversial because of its highly dismemberedstructural setting. Recently, Bortolotti et al. (2003)interpreted this unit as a true ophiolitic nappe.Whatever the case may be, this unit consists ofscattered serpentinite slivers at the base andthrust sheets of pillow lavas and minor massivelavas and pillow breccias (Fig. 2e).

Radiolarian cherts are found as thin, scatteredintercalations in basalts, as well as at the top ofthe volcanic sequences. Radiolarian assemblagesindicate two distinct ages: Middle–Late Triassicand Early–Middle Jurassic (Bortolotti et al. 2003).Middle Triassic basalts display a clear MORBaffinity (Saccani et al. 2004b), thus representing aremnant of the oldest oceanic crust in the Helle-nide Belt.

The Wedged unit consists of tectonic sliceslocally intercalated between the Lower and Middleunits (Fig. 2e) in the central and northern Argolis.These slices contain volcanic sequences, up to100 m thick, which are characterized by highlyvesicular and porphyritic pillow lavas affected bylower grade greenschist oceanic metamorphism.

The Upper unit is represented by the Iliokastronmélange that crops out in the central–northern andsouthern Argolis and by the Adheres mélange thatsurfaces only in the southern Argolis.

The Iliokastron mélange consists of foliatedblocks of harzburgites within a sheared matrix ofserpentinized harzburgite and dunite, up to 300 mthick. It also includes meter-sized, lens-shapedblocks of basalts, boninitic rocks (Capedri et al.1996) and various exotic blocks (marble, meta-graywacke, micaschist and amphibolite). This unitcorresponds to a tectonic mélange that tectonicallyoverlies the post-Ypresian flysch of the LygourionMesoautochthon, as well as the Adheres mélange(Bortolotti et al. 2002a, 2003; references therein).

Nevertheless, the Adheres mélange that devel-oped during the Eocene ensialic tectonic phase,tectonically overlies the Middle unit (Dhimainaunit) and mainly consists of a sedimentarymélange, which is characterized by a disruptedturbiditic succession of siltstones, sandstones andmarls affected by strong pervasive deformations

(Bortolotti et al. 2003). This mélange incorporatesblocks of various nature, including Triassic volca-nics, Middle–Late Jurassic radiolarites, Jurassicand Cretaceous limestones, andesites, Jurassicgranodiorites, serpentinites and various basalts.Finally, both Iliokastron and Adheres mélangesare tectonically overlain by Kimmeridgian–Maastrichtian carbonate slices of the Faniskosunit, which are covered, in turn, by an Eocenicflysch. A Cretaceous–Eocene ‘Mesoautochthonous’cover seals the tectonic relationships between thedifferent mélange units (Bortolotti et al. 2003).

ANALYTICAL TECHNIQUES

Bulk-rock major and trace element analyses wereperformed by X-ray fluorescence (XRF) and byinductively coupled plasma–mass spectrometry atthe Department of Earth Sciences at the Univer-sity of Ferrara, Italy. Chemical compositions aregiven in Tables 1–3. The XRF analyses were per-formed with an ARL Advant-XP automated spec-trometer using the matrix correction methodsproposed by Lachance and Trail (1966). Accuracyand detection limits were determined using a setof international standards, run as ‘unknown’.Accuracy was better than 3% for Si, Ti, Ca and K;7% for Al, Mn, Mg, Na and P; and better than 6%for trace elements, with the exception of Ba (8%),Th (10%) and Nb (13%). Detection limits for traceelements were Zn, Cu, Sc, Ga, Ba = 5 p.p.m.; Ni,Co, Cr, V, Rb = 1 p.p.m.; and Pb, Sr, Zr, Y = 2 p.p.m.

Inductively coupled plasma–mass spectrometryanalyses were performed using a VG ElementalPlasma Quad PQ2 Plus spectrometer. Accuracywas in the range 2–7 (relative percentage), withthe exception of Nb (12%), Ta (16%) and U (9%).Detection limits were Sc = 0.29 p.p.m.; Nb, Hf,Ta = 0.02 p.p.m.; Th, U = 0.01 p.p.m.; and rareearth elements (REE) < 0.07.

Volatiles were determined as ‘loss on ignition’(LOI) at 1000°C, whereas CO2 was determined bya simple volumetric technique (Jackson 1958)using standard amounts of reagent grade CaCO3

and 20 reference samples with different CO2 con-tents for calibration; the mean relative percentageerror obtained was 2.4%.

GEOCHEMICAL TYPES

All samples studied in the present paper areaffected by variable degrees of ocean-floor


Table 1 Bulk-rock major and trace element analyses of selected volcanic and subvolcanic rocks from the Rubik complexand Simoni mélange (Mirdita zone) and from the Avdella mélange (Pindos, Greece)

Sample:Rock:Type:Note:Age:

Rubik complex Simoni mélange Avdella mélangeAL129

BA VLT

AL130

VLT

02/AL6B

M/I Block

02/AL10B

N-M Dyke†

03/19B

E-M Block L.Tr

03/20B

E-M Block L.Tr

03/22B

E-M Block L.Tr

EP15BA

VLT Block

EP16BA

VLT Pillow

EP3B

N-MBlock

EP14B

WPBSlice

Tr

EP24B

WPBSlice

Tr

X-ray fluorescence analysesSiO2 55.32 54.81 45.03 48.41 52.06 50.63 51.59 53.40 54.11 47.23 46.61 44.47TiO2 0.18 0.39 0.82 0.75 1.15 1.04 1.67 0.27 0.27 1.99 1.89 1.72Al2O3 10.46 15.10 15.70 14.12 16.96 15.54 13.00 14.94 12.85 15.57 17.76 16.24Fe2O3 1.03 1.34 1.12 0.92 0.84 0.96 1.05 0.81 0.90 1.43 1.31 1.61FeO 6.89 8.94 7.50 6.12 5.60 6.38 6.97 5.38 6.00 9.55 8.74 10.70MnO 0.14 0.15 0.14 0.15 0.39 0.42 0.21 0.14 0.15 0.22 0.24 0.20MgO 11.77 5.57 13.20 7.26 8.39 10.81 5.94 13.16 16.20 6.56 9.10 12.88CaO 10.57 7.69 8.84 17.62 5.37 6.34 9.46 3.64 2.99 11.09 5.84 4.23Na2O 1.75 3.03 2.55 1.21 4.82 4.21 5.43 4.28 2.59 3.68 4.73 3.16K2O 0.12 0.05 n.d. n.d. 0.43 0.35 0.01 0.03 0.01 0.30 0.33 0.33P2O5 0.20 0.11 0.06 0.07 0.10 0.10 0.12 n.d. n.d. 0.17 0.35 0.40LOI 1.57 2.82 4.31 3.54 3.23 3.68 4.39 3.93 3.89 2.18 3.09 4.04Total 100.00 100.00 99.29 100.17 99.36 100.46 99.83 99.98 99.97 99.97 99.99 99.98Mg# 75.5 52.6 75.8 67.9 72.7 75.1 60.3 81.4 82.8 55.1 65 68.2Zn 82 84 66 55 92 102 73 61 86 87 92 113Cu n.d. n.d. 86 56 93 93 74 n.d. n.d. n.d. n.d. n.d.Sc n.d. n.d. 27 27 45 40 34 n.d. n.d. n.d. n.d. n.d.Ga n.d. n.d. 8 18 18 15 11 n.d. n.d. n.d. n.d. n.d.Ni 116 22 154 54 31 32 173 53 262 93 110 178Co 38 33 43 36 39 43 33 32 36 44 40 56Cr 777 38 253 155 217 157 247 111 690 282 176 170V 252 323 183 215 260 285 278 173 165 311 150 141Rb 2 2 n.d. n.d. 10 7 2 n.d. n.d. 6 5 9Ba 57 30 40 29 68 60 85 9 9 83 107 112Pb 2 9 n.d. n.d. n.d. n.d. n.d. 5 3 9 4 3Sr 79 8 95 40 141 111 150 49 40 151 337 310Zr 27 30 29 48 69 64 122 30 29 140 142 173Y 6 12 27 26 23 27 35 10 11 48 25 26Inductively coupled plasma–mass spectrometry analysesSc 80.2 77.7 32.5 32.3 47.5 44.7 45.2 127 35.0 17.9La 0.61 0.90 0.77 1.94 3.41 4.10 6.22 0.82 2.68 45.2Ce 1.31 2.27 2.77 5.45 8.03 11.4 17.0 1.92 7.64 93.5Pr 0.16 0.31 0.55 0.87 1.12 1.41 2.55 0.27 1.59 10.6Nd 0.79 1.66 3.80 5.05 5.77 6.98 13.00 1.36 8.19 39.4Sm 0.33 0.66 1.79 1.81 1.93 2.27 3.65 0.46 2.45 7.27Eu 0.14 0.19 0.69 0.62 0.70 0.79 1.30 0.14 0.98 1.32Gd 0.45 0.95 2.58 2.41 2.36 2.69 4.52 0.70 2.71 6.77Tb 0.11 0.19 0.52 0.48 0.40 0.48 0.78 0.14 0.52 0.92Dy 0.89 1.52 3.29 3.00 2.67 3.17 5.23 1.02 3.32 5.19Ho 0.22 0.36 0.77 0.70 0.61 0.72 1.00 0.24 0.73 1.01Er 0.74 1.18 2.14 2.01 1.68 2.01 3.04 0.72 1.92 2.63Tm 0.12 0.18 0.30 0.29 0.28 0.32 0.45 0.11 0.28 0.37Yb 0.97 1.50 2.10 2.02 1.77 2.00 2.58 0.77 1.62 2.05Lu 0.16 0.23 0.29 0.29 0.26 0.26 0.36 0.11 0.21 0.27Nb 0.54 0.46 0.64 1.79 2.39 2.21 5.10 1.96 1.17 21.3Hf 0.45 0.63 1.10 1.32 1.86 1.79 2.89 n.d. 1.59 0.35Ta 0.06 0.05 0.10 0.25 0.32 0.29 0.44 0.14 0.11 1.28Th 0.15 0.26 0.07 0.18 0.18 0.16 0.25 0.21 0.16 11.7U 0.06 0.12 0.06 0.06 0.71 0.28 0.10 0.08 0.06 1.19Ti/V 4 7 28 22 28 23 38 9 10 38 75 73Zr/Y 4.5 2.5 1.1 1.8 3 2.3 3.5 3 2.7 2.9 5.7 6.6Nb/Y 0.09 0.04 0.02 0.07 0.10 0.08 0.14 0.20 0.02 0.82Th/Ta 2.36 5.43 0.70 0.71 0.56 0.54 0.58 1.46 1.46 9.14(La/Sm)N 1.20 0.89 0.28 0.69 1.14 1.17 1.10 1.16 0.71 4.01(La/Yb)N 0.45 0.43 0.26 0.69 1.38 1.47 1.73 0.77 1.19 15.81

†Dyke intruded in the mélange matrix. Normalization values for rare earth element ratios are from Sun and McDonough (1989).B, basalt; BA, basaltic andesite; E-M, enriched mid-oceanic ridge basalt (MORB); L.Tr, Late Triassic; LOI, loss on ignition; Mg#, molar

Mg/(Mg + Fe) × 100; M/I, MORB/island arc tholeiite intermediate; n.d., not detected; N-M, normal MORB; Tr, Triassic; VLT, very low-Ti;WPB, within plate basalts.


Table 2 Bulk-rock major and trace element analyses of selected volcanic and subvolcanic rocks from the Koziakas† andAgoriani‡ mélanges

Sample:Rock:Type:Note:

Koziakas mélange Agoriani mélange6B

WPBMLF

13B

WPBMLF

9B

WPBPillow

37B

N-MPillow

24B

E-MPillow

29B

VLTDyke§

EK 1c B

WPBBlock

EK 1j B

N-MBlock

EK 1aB

M/IBlock

EK 2i B

M/I Block

EK 1bBA

VLT Block

EK 5BA

VLT Block

X-ray fluorescence analysesSiO2 44.50 45.56 48.80 45.87 47.30 51.69 51.33 43.78 44.88 44.47 52.19 53.82TiO2 1.72 2.24 1.13 2.03 2.12 0.42 2.92 0.92 0.77 0.79 0.14 0.32Al2O3 16.21 15.92 15.97 17.98 15.34 15.67 15.48 16.87 17.22 17.18 10.19 14.96Fe2O3 1.30 1.79 1.07 1.46 1.80 1.35 0.96 1.14 1.16 1.13 1.14 1.34FeO 8.69 11.90 7.13 9.73 12.03 8.97 6.40 7.61 7.72 7.56 7.59 8.91MnO 0.21 0.22 0.12 0.17 0.21 0.16 0.20 0.14 0.16 0.14 0.19 0.18MgO 7.36 6.30 9.32 6.37 5.86 7.01 3.04 11.16 11.61 11.15 16.04 6.98CaO 11.49 8.79 8.30 11.02 8.38 8.42 6.40 14.27 12.48 13.89 10.42 8.28Na2O 2.26 3.62 3.42 3.48 3.76 3.31 6.34 1.29 1.62 1.39 0.37 1.61K2O 0.67 0.35 1.25 0.03 0.67 0.34 0.73 0.01 0.04 0.01 0.03 0.20P2O5 0.31 0.47 0.29 0.23 0.32 0.09 0.57 0.19 0.13 0.17 0.08 0.06LOI 5.28 2.84 3.20 1.63 2.20 2.54 5.62 2.62 2.18 2.12 1.58 3.31Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00Mg# 60.1 48.6 70.0 53.9 46.5 58.2 45.8 72.3 72.8 72.4 79.0 58.3

Zn 79 106 67 77 98 n.d. 120 42 77 64 52 73Ni 52 35 98 154 47 30 29 208 231 290 323 21Co 47 47 34 47 48 38 22 41 48 46 49 36Cr 130 28 270 297 78 97 24 531 534 655 1162 41V 251 307 278 265 370 304 227 215 192 183 197 302Rb 8 6 17 n.d. 6 4 5 n.d. n.d. n.d. n.d. 5Ba 153 138 167 10 151 50 135 23 26 31 31 34Pb 6 6 2 6 2 5 8 7 5 5 7 7Sr 305 289 466 140 275 161 300 329 75 100 23 115Zr 139 245 118 157 174 15 368 47 5 26 4 18Y 59 39 25 43 42 10 49 25 24 24 6 11Inductively coupled plasma–mass spectrometry analysesSc 97.9 45.3 40.3 49.3 55.5 57.1 20.8 54.0 28.2 35.5 48.9 50.2La 28.2 17.0 14.9 2.01 12.5 1.45 45.6 1.42 0.04 0.24 0.35 1.12Ce 59.8 37.6 29.6 9.42 28.8 2.51 104 3.99 0.32 1.15 0.70 2.17Pr 8.12 5.15 3.61 2.12 4.09 0.38 10.6 0.81 0.16 0.41 0.12 0.36Nd 35.2 22.4 15.2 12.9 22.5 2.25 43.1 5.34 1.79 2.91 0.53 1.59Sm 8.01 5.47 3.35 4.56 6.37 0.88 10.4 2.29 1.28 1.56 0.22 0.61Eu 2.80 1.81 1.13 1.65 2.03 0.37 3.15 0.81 0.51 0.66 0.09 0.24Gd 8.14 5.92 3.60 5.62 5.81 1.46 10.5 3.27 1.66 2.54 0.39 0.96Tb 1.36 0.99 0.61 1.10 1.10 0.27 1.65 0.68 0.42 0.54 0.09 0.20Dy 8.31 5.80 3.60 6.93 6.81 2.00 8.83 4.45 2.97 3.58 0.70 1.43Ho 1.72 1.16 0.76 1.50 1.58 0.54 1.73 0.97 0.72 0.82 0.19 0.36Er 4.35 3.17 2.00 4.21 4.32 1.66 4.59 2.74 1.93 2.31 0.61 1.09Tm 0.64 0.45 0.31 0.63 0.73 0.27 0.66 0.42 0.32 0.37 0.11 0.19Yb 3.99 2.92 2.19 4.13 4.94 2.05 3.76 2.57 2.00 2.22 0.77 1.29Lu 0.59 0.43 0.33 0.63 0.80 0.35 0.61 0.39 0.30 0.33 0.13 0.21Nb 46.2 26.4 24.9 1.10 14.9 1.20 52.4 1.25 0.15 0.08 0.46 0.66Hf 5.11 7.31 2.70 6.43 5.68 1.39 10.2 1.90 0.62 0.84 0.23 0.69Ta 2.53 1.67 1.45 0.12 1.13 0.57 3.71 0.19 0.10 0.05 0.06 0.20Th 2.71 1.88 1.54 0.06 1.49 0.82 6.92 0.09 0.01 0.01 0.08 0.26U 0.57 0.40 0.45 0.02 0.49 0.73 1.60 0.03 0.01 0.01 0.04 0.12

Ti/V 44 45 25 47 35 9 82 26 25 27 4 7Zr/Y 2.4 6.3 4.7 3.6 4.2 1.5 7.6 1.9 0.2 1.1 0.7 1.7Nb/Y 0.78 0.68 0.99 0.03 0.36 0.12 1.08 0.05 0.01 0.00 0.08 0.06Th/Ta 1.07 1.12 1.07 0.50 1.32 1.43 1.86 0.49 0.05 0.18 1.42 1.30(La/Sm)N 2.27 2.01 2.88 0.29 1.26 1.06 2.83 0.40 0.02 0.10 1.05 1.18(La/Yb)N 5.07 4.19 4.88 0.35 1.81 0.51 8.70 0.40 0.01 0.08 0.33 0.62

†Data from Saccani et al. (2003); ‡data from Photiades et al. (2003); §dyke cross-cutting within-plate (e.g. sample 31) and enriched mid-oceanic ridge basalt (E-MORB; e.g. sample 26) sequences. Normalization values for rare earth element ratios are from Sun and McDonough(1989).

B, basalt; BA, basaltic andesite; E-M, E-MORB; LOI, loss on ignition; Mg#, molar Mg/(Mg + Fe) × 100; M/I, MORB/island arc tholeiiteintermediate; MLF, massive lava flow; n.d., not detected; N-M, normal MORB; VLT, very low-Ti; WPB, within plate basalts.


Table 3 Bulk-rock major and trace element analyses of selected volcanic rocks from the Lower, Wedged, Middle and Upperunits of the Argolis Peninsula

Sector:Sample:Rock:Type:Note:

Lower unit (Potami Formation) Wedged unit Middle unit (Dhimaina unit)North

307BA

VLT Block

South345 A

BA VLT Block

SouthF81B

VLT Olist.

SouthF87B

VLT Olist.

SouthF88B

VLT Olist.

SouthF91BA

VLT Olist.

Central416B

WPB Block

North 471B

WPB Pillow

North 476B

WPB Pillow

Central396B

WPB Breccia

Central411 A

B WPB MLF

Central413B

WPB MLF

CentralR13

B WPBPillow

X-ray fluorescence analysesSiO2 54.03 52.17 50.58 48.85 51.82 53.61 37.94 36.15 36.12 47.96 42.20 43.46 47.83TiO2 0.18 0.47 0.31 0.15 0.52 0.18 1.20 1.03 1.01 2.20 2.23 2.28 2.84Al2O3 10.50 14.91 15.02 9.14 16.04 11.14 11.50 9.47 9.38 14.44 12.01 14.20 12.69Fe2O3 1.05 1.08 0.98 0.68 0.86 0.82 0.64 0.86 1.05 1.42 1.11 1.41 1.28FeO 7.01 7.19 6.52 4.55 5.76 5.44 4.24 5.72 7.03 9.46 7.39 9.38 8.54MnO 0.16 0.23 0.14 0.16 0.15 0.21 0.23 0.24 0.24 0.20 0.57 0.15 0.33MgO 14.91 12.64 12.35 20.49 13.57 16.53 9.81 7.06 6.95 8.17 9.71 5.95 10.06CaO 7.11 4.23 7.14 10.38 5.39 7.19 20.41 25.46 24.77 8.69 14.28 12.66 7.28Na2O 0.53 2.85 2.98 0.40 1.55 0.76 2.72 1.43 1.45 3.81 3.48 3.55 4.63K2O 1.31 0.20 0.64 0.98 0.10 1.28 0.51 0.66 0.78 0.54 0.31 0.49 0.08P2O5 0.02 0.05 0.03 0.01 0.05 0.02 0.22 0.15 0.19 0.34 0.33 0.33 0.45LOI 3.15 3.95 3.32 4.22 4.18 2.82 10.55 11.74 11.00 2.76 6.35 6.15 3.96Total 99.96 99.97 99.99 100.01 99.99 100.00 99.98 99.98 99.97 99.99 99.97 100.01 99.98CO2 n.a. n.a. n.a. n.a. n.a. n.a. 9.30 10.64 10.26 n.a. 5.80 3.58 n.a.CaO* 8.59 11.91 11.71 6.89 8.10

Mg# 79.1 75.8 77.1 88.9 80.8 84.4 80.5 68.7 63.8 60.6 70.1 53.0 67.7

Pb 2 5 4 3 6 4 4 3 3 2 3 4 8Zn 25 102 39 45 51 50 24 48 50 95 105 98 115Ni 162 71 80 338 94 205 76 176 132 122 111 53 23Co 46 33 33 51 28 46 22 42 35 37 42 36 38Cr 604 133 65 1320 98 726 240 734 765 176 302 40 19V 235 256 289 217 204 212 237 200 226 315 322 338 365Rb 16 5 7 8 3 13 6 8 10 8 4 6 3Sr 54 163 198 116 131 76 210 230 222 338 270 152 111Ba 674 58 49 144 31 147 147 117 128 144 136 102 88Zr 10 25 16 3 22 11 51 45 45 184 143 180 261Y 6 13 12 3 11 5 18 13 13 38 35 36 52

Inductively coupled plasma–mass spectrometry analysesSc 43.7 29.8 36.9 42.7 31.5 35.7 34.1 19.9 18.8 45.3 43.0 31.8 16.4La 1.60 3.16 1.20 0.26 1.31 2.04 15.8 10.9 10.9 12.8 14.4 19.8 24.5Ce 2.73 7.49 3.48 0.68 3.93 4.73 32.3 25.2 25.9 31.1 36.8 44.9 63.1Pr 0.29 0.82 0.37 0.06 0.51 0.43 3.52 3.14 2.98 4.32 4.63 5.65 7.50Nd 1.29 3.83 1.91 0.30 2.49 1.53 14.7 13.5 12.9 20.4 21.2 25.0 34.4Sm 0.44 1.10 0.72 0.15 0.88 0.46 3.10 2.85 2.79 5.18 5.13 5.51 7.94Eu 0.17 0.44 0.16 0.07 0.26 0.12 1.01 0.97 0.95 1.74 1.71 1.90 2.40Gd 0.62 1.38 1.09 0.39 1.16 0.57 3.50 3.02 3.30 5.95 5.25 5.57 7.26Tb 0.11 0.27 0.25 0.07 0.22 0.11 0.53 0.47 0.46 0.94 0.88 0.87 1.16Dy 0.93 1.88 2.09 0.67 1.75 0.77 3.83 3.05 2.92 5.94 5.82 5.42 7.49Ho 0.24 0.43 0.51 0.16 0.37 0.19 0.79 0.60 0.58 1.13 1.14 1.12 1.50Er 0.73 1.27 1.59 0.53 1.12 0.60 2.38 1.53 1.54 3.15 3.01 2.89 3.86Tm 0.13 0.19 0.24 0.07 0.15 0.09 0.32 0.21 0.19 0.46 0.43 0.39 0.52Yb 0.91 1.34 1.88 0.56 1.04 0.70 2.39 1.37 1.34 2.71 2.40 2.52 3.43Lu 0.14 0.18 0.25 0.08 0.15 0.10 0.32 0.17 0.21 0.39 0.35 0.36 0.49Nb 0.89 0.68 1.02 0.30 0.43 1.06 16.7 9.49 8.92 13.6 14.2 20.1 19.9Hf 0.40 0.85 0.59 0.07 0.76 0.37 2.09 1.88 1.57 3.95 3.82 4.56 6.16Ta 0.19 0.10 0.12 0.14 0.05 0.13 0.67 0.39 0.36 0.49 0.49 0.67 0.78Th 0.32 0.23 0.48 0.05 0.19 0.62 1.82 0.99 0.91 0.97 1.03 1.62 2.14U 0.16 0.13 0.24 0.02 0.06 0.39 0.66 0.62 0.63 0.50 1.97 1.82 1.02

Ti/V 4.6 11.4 6.6 4.2 15.9 5.1 39.6 42.1 35.8 43.1 48.3 45.5 48.6Zr/Y 1.6 1.9 1.3 1.0 1.9 2.0 2.8 3.5 3.4 4.8 4.0 5.0 5.0Nb/Y 0.14 0.05 0.08 0.09 0.04 0.20 0.91 0.74 0.66 0.36 0.40 0.56 0.38Th/Ta 1.70 2.31 3.83 0.35 3.82 4.91 2.72 2.55 2.54 1.96 2.10 2.40 2.74(La/Sm)N 2.37 1.86 1.08 1.13 0.96 2.87 3.29 2.46 2.53 1.60 1.81 2.32 1.99(La/Yb)N 1.26 1.69 0.46 0.33 0.90 2.08 4.73 5.69 5.83 3.40 4.31 5.61 5.12


Table 3 Continued

Sector:Sample:Rock:Type:Note:

Middle unit (Dhimaina unit) Upper unit (Iliokastron and Adheres units)North

459B

E-M Pillow

CentralR9B

E-M Pillow

CentralR12

B N-M

Pillow

North313B

N-MMLF

North479B

N-MMLF

CentralR1BA

N-M Pillow

CentralR6B

N-M Pillow

CentralR7B

N-M Pillow

North306B

VLTClast

South339Z

B VLTClast

South378B

VLTClast

South393B

VLTClast

South344B

WPBClast

South363 B

N-MClast

X-ray fluorescence analysesSiO2 49.11 43.15 47.26 44.61 49.00 52.26 46.39 41.60 48.75 48.01 46.24 46.28 45.50 46.59TiO2 2.09 1.40 1.77 1.57 1.10 1.59 1.00 1.41 0.14 0.38 0.18 0.36 1.07 0.95Al2O3 12.73 13.86 13.89 13.19 14.53 14.24 15.05 13.33 22.73 12.95 8.55 9.32 13.64 17.15Fe2O3 1.37 1.14 1.73 1.49 1.18 1.06 1.10 1.45 0.79 0.87 0.93 0.66 1.01 1.12FeO 9.14 7.62 11.54 9.92 7.88 7.04 7.36 9.67 5.30 5.79 6.18 4.42 6.74 7.50MnO 0.28 0.14 0.22 0.14 0.18 0.13 0.14 0.14 0.13 0.21 0.17 0.11 0.22 0.15MgO 8.38 9.70 8.92 8.15 11.29 7.19 8.37 6.38 8.13 19.85 25.55 18.11 6.36 10.72CaO 8.77 13.61 8.58 12.12 8.51 8.53 11.85 16.48 4.55 4.16 5.79 16.78 13.10 9.86Na2O 4.49 2.74 2.96 3.18 3.00 5.03 3.46 2.76 0.62 1.88 0.12 0.29 2.28 1.96K2O 0.24 0.27 0.05 0.07 0.42 0.03 0.30 0.11 4.46 0.99 0.29 0.01 2.09 1.23P2O5 0.19 0.19 0.23 0.15 0.11 0.13 0.08 0.12 0.02 0.04 0.02 0.02 0.33 0.10LOI 3.20 6.12 2.82 5.38 2.79 2.77 4.87 6.53 4.35 4.85 5.96 3.61 7.63 2.64Total 100.00 99.94 99.97 99.96 99.98 99.98 99.97 99.98 99.97 99.98 99.97 99.97 99.98 99.96CO2 n.a. 2.49 n.a. n.a. n.a. n.a. n.a. 4.38 n.a. n.a. n.a. n.a. 5.50 n.a.CaO* 10.44 10.91 6.10Mg# 62.0 69.4 57.9 59.4 71.9 64.5 66.9 54.0 73.2 85.9 88.1 88.0 62.7 71.8Pb 5 4 2 2 3 3 3 2 2 4 2 7 7 3Zn 126 67 115 73 58 88 61 84 31 27 91 25 66 64Ni 42 101 70 65 94 52 81 67 53 54 869 269 91 120Co 51 35 40 35 40 40 35 38 30 30 72 37 21 39Cr 30 271 153 120 258 133 231 139 66 81 1739 574 268 343V 423 289 378 311 272 249 229 328 181 265 162 218 233 212Rb 5 6 2 3 6 3 5 4 45 15 5 2 32 16Sr 146 106 74 79 229 103 137 99 137 88 11 33 129 256Ba 130 60 66 47 56 52 48 50 2822 187 18 10 129 426Zr 127 77 118 80 59 88 49 62 8 17 4 9 64 53Y 45 21 37 29 21 33 20 27 9 10 3 4 18 19Inductively coupled plasma–mass spectrometry analysesSc 36.1 17.7 22.4 45.6 19.0 22.5 18.1 20.5 31.6 31.6 29.5 32.1 29.1 35.5La 14.1 9.84 5.53 5.05 2.65 3.52 2.39 3.42 0.56 1.09 0.31 0.82 15.09 2.64Ce 33.0 22.9 16.9 14.0 8.86 12.0 8.06 10.2 1.22 2.93 0.78 2.76 33.6 8.27Pr 4.31 2.79 2.49 2.03 1.45 1.86 1.29 1.52 0.13 0.40 0.08 0.39 3.96 1.26Nd 19.8 12.4 12.3 10.5 7.79 10.2 7.12 8.63 0.59 2.32 0.42 2.06 16.9 6.73Sm 5.39 3.05 4.06 3.18 2.49 3.46 2.42 2.87 0.32 0.87 0.24 0.73 3.73 2.39Eu 1.62 0.91 1.35 1.10 0.93 1.23 0.91 1.06 0.11 0.36 0.09 0.21 1.13 0.89Gd 5.60 3.01 4.28 3.81 2.63 3.72 2.78 3.45 0.45 1.33 0.36 0.99 3.76 2.89Tb 1.06 0.56 0.93 0.77 0.62 0.78 0.56 0.69 0.10 0.23 0.07 0.21 0.54 0.50Dy 6.98 3.40 6.14 5.09 3.81 5.38 3.80 4.61 0.77 1.82 0.71 1.48 3.47 3.48Ho 1.56 0.76 1.36 1.12 0.87 1.17 0.85 1.07 0.19 0.41 0.17 0.32 0.67 0.75Er 4.38 2.07 3.80 3.15 2.38 3.02 2.36 2.89 0.61 1.30 0.54 1.04 1.87 2.22Tm 0.68 0.30 0.56 0.50 0.29 0.46 0.32 0.40 0.10 0.20 0.09 0.14 0.25 0.29Yb 3.90 1.99 3.40 2.93 2.12 2.86 2.24 2.84 0.72 1.42 0.58 1.12 1.74 2.09Lu 0.61 0.29 0.54 0.43 0.32 0.41 0.30 0.44 0.10 0.19 0.09 0.13 0.23 0.29Nb 18.8 9.96 4.26 4.82 1.66 2.16 1.52 2.11 0.76 0.67 0.52 0.52 18.1 1.44Hf 4.03 2.55 2.84 2.51 1.70 2.79 1.97 2.41 0.32 0.84 0.20 0.54 2.13 1.51Ta 0.64 0.42 0.22 0.28 0.11 0.12 0.13 0.13 0.18 0.20 0.17 0.14 0.78 0.16Th 1.86 1.15 0.25 0.39 0.07 0.29 0.14 0.27 0.17 0.18 0.13 0.14 1.78 0.09U 0.63 1.34 0.09 0.19 0.02 0.27 0.10 1.14 0.08 0.06 0.05 0.02 0.37 0.01Ti/V 30.7 32.2 28.9 31.9 24.8 39.3 27.5 29.6 4.7 9.1 7.3 10.3 32.4 27.5Zr/Y 2.8 3.8 3.2 2.7 2.7 2.7 2.4 2.3 1.0 1.7 1.3 2.2 3.5 2.8Nb/Y 0.42 0.48 0.11 0.16 0.08 0.07 0.07 0.08 0.09 0.07 0.15 0.12 0.99 0.08Th/Ta 2.89 2.75 1.14 1.40 0.67 2.34 1.09 2.08 0.91 0.89 0.76 0.95 2.30 0.53(La/Sm)N 1.69 2.08 0.88 1.03 0.69 0.66 0.64 0.77 1.13 0.81 0.84 0.73 2.61 0.71(La/Yb)N 2.59 3.55 1.17 1.24 0.90 0.88 0.77 0.86 0.55 0.55 0.39 0.53 6.23 0.91

Normalization values for rare earth element ratios are from Sun and McDonough (1989).B, basalt; BA, basaltic andesite; CaO*, CaO recalculated after subtraction of CaO in calcite; E-M, enriched mid-oceanic ridge basalt (E-

MORB); LOI, loss on ignition; Mg#, molar Mg/(Mg + Fe) × 100; M/I, MORB/island arc tholeiite intermediate; MLF, massive lava flow; n.a.,not analyzed; N-M, normal MORB; Olist., olistolith; VLT, very low-Ti; WPB, within plate basalts.


hydrothermal metamorphism and/or secondaryalteration. Nonetheless, many authors (e.g.Beccaluva et al. 1979; Pearce & Norry 1979)have demonstrated that concentrations of someincompatible elements (such as Th, U, Ta, Nb,REE, P, Hf, Zr, Ti and Y) and transition metals(such as Ni, Co, Cr and V) are relatively immobileduring alteration or metamorphic processes andcan thus be effectively used to describe the pri-mary geochemical features of ophiolitic rocks. Inaddition, in many of the samples from the Argolismélange, alteration has commonly resulted in thecrystallization of secondary calcite; consequently,the CaO content has been recalculated by sub-tracting the CaO contained in calcite (Table 3).

The volcanic and subvolcanic mafic rocksincluded in the Subpelagonian ophiolitic mélangesshow a wide range of geochemical characteristics(Tables 1–3); in fact, four main geochemical groupscan be identified: (i) transitional–alkaline rocksgenerated in within-plate settings (WPB); (ii)high-Ti MORB; (iii) very low-Ti (boninitic) basaltsand basaltic andesites, and (iv) basalts withgeochemical features intermediate betweenMORB and IAT; hereafter defined, according toSaccani et al. (2004a), as MORB/IAT intermediatebasalts.

TRANSITIONAL–ALKALINE ROCKS

This group consists of both pillowed and massivelavas from all the investigated localities, and ismainly represented by basalts and basaltic andes-ites (Tables 1–3). A subordinate occurrence of tra-chyandesites and trachytes genetically related tothis group has been reported for the Koziakasmélange (Saccani et al. 2003).

The transitional–alkaline nature of these rocksis evidenced in the Ti/Y vs Nb/Y diagram ofFigure 3, where it can be observed that Nb/Yratios range from 0.4 to 2.0. They are charac-terized by relatively high TiO2 (1.01–2.92 wt%),P2O5 (0.15–0.57 wt%), Zr (45–368 p.p.m.), Y (13–59 p.p.m.) and Ti/V ratios (Fig. 4a), as well as highCr content in the less evolved basalts (up to765 p.p.m. with Mg# = 63.8). The incompatible ele-ment abundance of mafic volcanic rocks (Fig. 5a)is characterized by decreasing patterns, from Rbto Yb, which are similar to those of typical within-plate tholeiites and alkali basalts. As shown inFigure 5b, these basaltic rocks display significantlight REE (LREE) enrichment with respect toheavy REE (HREE), which is exemplified by theirLaN/YbN ratios, ranging from 3.40 to 15.81.

Saccani et al. (2003) reported that in the Kozia-kas Massif, basaltic rocks found as massive lavaflows curiously display slightly different geochem-ical features with respect to their pillowed ana-logs. The former display higher FeOt, V and Yenrichment and lower P2O5 enrichment withdecreasing Mg#, in comparison with the lattervarieties. Massive lavas are characterized byfairly constant CaO/Al2O3 ratios, whereas pillowlavas display decreasing CaO/Al2O3 ratios withdecreasing Mg#. In addition, massive lavas havemoderate Nb positive anomalies, which are notobserved in pillow lavas. Saccani et al. (2003) have

Fig. 3 Ti/Y vs Nb/Y diagram for volcanic and subvolcanic rocks fromthe Mirdita–Subpelagonian mélange units. Modified from Pearce (1982).A, within plate; B, mid-ocean ridge; C, volcanic arc; MORB/IAT, mid-oceanic ridge basalt/island arc tholeiite; N-MORB, normal MORB; T-MORB, transitional MORB; WPB, within-plate basalts.

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Fig. 4 V vs Ti/1000 diagrams (Shervais 1982) for volcanic and sub-volcanic basaltic rocks from (a) Mirdita–Subpelagonian mélange unitsand (b) Mirdita–Subpelagonian ophiolites (modified from Beccaluva et al.2005; references therein). E-MORB, enriched MORB; MORB/IAT, mid-oceanic ridge basalt/island arc tholeiite; N-MORB, normal MORB; WPB,within-plate basalts.

Ti/V = 10 20

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interpreted these geochemical differences asreflecting different crystallization orders in thetwo textural varieties – namely, early crystalliza-tion of plagioclase and clinopyroxene in the mas-sive types, and the predominance of clinopyroxeneover plagioclase crystallization in the pillowedtypes. In contrast, transitional–alkaline basalticrocks from all other localities do not display anygeochemical difference among different texturaltypes.

The overall geochemical data indicate a transi-tional–alkaline affinity for these rocks, which isvery similar to that of Triassic WPB from variouslocalities of the Hellenides (Pe-Piper 1998; Pe-Piper & Piper 2002).

HIGH-TI, MID-OCEANIC RIDGE BASALTS

This group is represented in all the investigatedareas and consists of pillowed and massive lavas,dykes and blocks showing basaltic composition,with silica ranging from 41.60 wt% to 52.26 wt%.Their subalkaline, MORB affinity is exemplified inthe Ti/Y vs Nb/Y plot (Fig. 3), as well as by the Ti/V ratios (Shervais 1982), which range from 22 to47 (Fig. 4a).

These rocks are characterized by rather variablechemical composition (Tables 1–3) and fraction-ation degrees (Mg# = 75.1–46.5). Nonetheless, theoverall geochemical features are similar to thoseof basalts generated at MOR (Le Roex et al.

Fig. 5 Normal mid-oceanic ridge basalt(MORB)-normalized incompatible elementand chondrite-normalized rare earth elementpatterns for volcanic and subvolcanic rocksfrom the Mirdita–Subpelagonian mélangeunits. Normalizing values are from Sun andMcDonough (1989). (a,b) Transitional–alkaline basalts; (c,d) enriched MORB; (e,f)normal MORB; (g,h) very low-Ti boniniticrocks; (i,j) MORB/island arc tholeiite interme-diate basalts.

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La Ce Pr NdPmSmEu Gd Tb Dy Ho Er TmYb Lu

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1983, 1985; Haase et al. 1997), having TiO2

content = 0.75–2.12 wt%, P2O5 = 0.07–0.32 wt%,V = 212–423 p.p.m., Zr = 47–174 p.p.m. and Y = 19–48 p.p.m. This group can be subdivided into twogeochemically distinct subgroups on the basis ofthe incompatible and REE abundance: enriched-MORB (E-MORB) and normal-MORB (N-MORB).

Enriched-MORB are represented by blocks inthe Rubik complex and pillow lavas in the Koziakasmélange, and MORB in the Subpelagonianmélanges by their Nb/Y ratios in the Argolis Mid-dle unit. They can be distinguished from N, whichare higher than 0.3, and by their slightly higher Ti/V ratios (Fig. 4a; Tables 1–3). Incompatible ele-ment display patterns (Fig. 5c) regularly decreasefrom low field strength elements (LFSE) to highfield strength elements (HFSE), with no U and no,or very slight, Nb depletions. These basalts showLREE enrichment similar to typical E-MORB(Sun & McDonough 1989), with LREE abundanceranging from 10- to 70-fold that of chondrite(Fig. 5d). They are also characterized by higherLFSE abundance than typical N-MORB, appear-ing in general similar to that of average E-MORB(Sun & McDonough 1989).

Normal-MORB include massive and pillow lavasequences, as well as various dykes and blocksfrom all the investigated mélange units. They arecharacterized by Nb/Y ratios definitely lower(0.02–0.26) than those of E-MORB from the samemélange units (Fig. 3a). These basalts generallyshow rather flat incompatible element patternsrelative to typical N-MORB (Sun & McDonough1989), with variable Nb depletion and, commonly,marked U depletion (Fig. 5e). REE abundancevaries from 6- to 30-fold that of chondrite, anddisplays flat profiles (Fig. 5f) with variable LREEdepletion. These basaltic rocks display close chem-ical analogies with N-MORB from the Mirdita(Saccani et al. 2004a; references therein) andPindos (Jones et al. 1991; Saccani & Photiades2004) ophiolites, as shown in Figure 4b.

VERY LOW-TI (BONINITIC) BASALTS AND BASALTIC ANDESITES

This group is represented by dykes, pillow lavasand blocks from all the investigated mélange units,with the exception of the Argolis Middle andWedged units.

The rocks studied in the present paper rangefrom basalts to basaltic andesites, and have silicacontents varying from 46.24 to 55.32 wt%. None-

theless, andesites have been reported in the Koz-iakas mélange by Saccani et al. (2003). The verylow TiO2 contents (0.14–0.52 wt%) and Ti/V ratios(Fig. 4a; Tables 1–3) are similar to those of typicalboninitic rocks from various ophiolitic complexes(Beccaluva et al. 1984, 2005; Beccaluva & Serri1988; Pearce 2003).

The P2O5 (0.06–0.17 wt%), Zr (3–30 p.p.m.) andY (3–13 p.p.m.) contents, with Mg# from 88.9 to52.6, are very low, in accordance with typical bon-initic compositions. Concentrations of compatibleelements, such as Ni (21–869 p.p.m.), Co (28–72 p.p.m.) and Cr (38–1739 p.p.m.) (Tables 1–3),are considerably higher in the less evolved basaltsand relatively low in the more evolved rocks, pos-sibly reflecting the fractionation of mafic phases(olivine, Cr–spinel and clinopyroxene) at the initialstages of crystallization.

These rocks are generally very depleted inHFSE, which are between 0.03- and 0.80-foldthose of the N-MORB compositions (Fig. 5g),whereas LFSE concentrations are fairly enrichedwith respect to typical N-MORB. The great vari-ability of LFSE concentration observed in theserocks (Fig. 5g) possibly reflects the effects of sec-ondary alteration. REE concentration varies from0.6- to 10.0-fold chondritic abundance, and most ofthe samples display U-shaped patterns typical ofboninites (Fig. 5h), with LaN/SmN and SmN/YbN

ratios ranging from 1.03 to 2.87 and from 0.36 to0.81, respectively.

The overall geochemical features of these rocksare very similar to those of boninitic mafic lavasfound in the forearc regions of oceanic island arcs(Crawford et al. 1989; Falloon & Crawford 1991),as well as to those of very low-Ti basaltic rocksfound in many ophiolitic complexes, and implymagma source(s) modified by subductionprocesses (Pearce 1982, 2003). In particular, theyshow close analogies with boninitic rocks fromthe Albanide–Hellenide ophiolites (Saccani et al.2004a; references therein), as shown in Figure 4b.

MID-OCEANIC RIDGE/ISLAND ARC THOLEIITE INTERMEDIATE BASALTS

This group exclusively includes basaltic rocks(SiO2 = 44.47–45.03 wt%), representing blocksincluded in the Rubik complex and Agorianimélange. They show geochemical characteristicsthat are intermediate between those of high-TiMORB and those of typical low-Ti IAT from manyophiolitic complexes (Beccaluva et al. 1984, 1994,2005; Saccani et al. 2004a). In particular, the TiO2


content varies from 0.77 to 0.82 wt%, Zr = 5–29p.p.m., Y = 24–27 p.p.m. and P2O5 = 0.06–0.17 wt%.These MORB/IAT intermediate geochemicalfeatures are also evidenced by the Ti/V ratios(Fig. 4a), which are in the range 8–28 (presentstudy and Photiades et al. 2003). Despite a consid-erable variation in the geochemical characteristicsof these basalts, the Mg# is relatively uniform andhigh (Mg# = 75.8–72.4), suggesting a scarce mag-matic evolution.

HFSE are generally depleted with respect toN-MORB (Sun & McDonough 1989) and mostof the samples analyzed in this paper exhibitremarkable Th, U, Nb, La and Ce depletion(Fig. 5i). The strong Nb depletion is also evi-denced by very low Nb/Y ratios, whereas the Ti/Yratios are slightly lower than those observed inMORB and similar to those of the boninites stud-ied in the present paper (Fig. 3). These basalts arecharacterized by medium to heavy REE patterns(Fig. 5k) quite similar to those of N-MORB(Fig. 5f), as well as by amounts of enrichment (10–12-fold those of the chondritic abundances) similarto those observed in MORB with a similar degreeof fractionation. However, they are typically char-acterized by severe LREE depletion (LaN/SmN = 0.02–0.28).

According to Pearce (1983), the strong depletionof Th, U, Nb and LREE, with respect to the N-MORB composition (Fig. 5i), as well as the verylow Zr/Y ratios (0.2–1.1) and the high Cr content(253–655 p.p.m.) account for a genesis in an SSZsetting.

Moreover, these basalts chemically correspondwith basalts found in some ophiolitic sequencesof Albania and Greece (Fig. 4b) – namely, the‘medium-Ti’ ophiolites from the Mirdita WesternOphiolite Belt (Bortolotti et al. 1996, 2002b), the‘intermediate-Ti and -Zr’ ophiolites of southernAlbania (Hoeck et al. 2002) and the upper pillowseries of the Aspropotamos complex in the PindosMassif (Saccani & Photiades 2004).

PETROGENESIS AND TECTONOMAGMATIC SETTINGS

The Subpelagonian mélange units include fourmain groups of mafic volcanic and subvolcanicrocks: (i) transitional–alkaline basalts, which arebest equated to WPB; (ii) high-Ti basalts – similarto MORB – which include, in turn, both N- and E-types; (iii) very low-Ti basalts and basaltic andes-ites similar to boninites; and (iv) MORB/IATbasalts.

According to Pearce and Norry (1979) andPearce (1983), the compositional differencesbetween these magma types could be primarilyrelated to different source characteristics that areassociated, in turn, with distinct tectonomagmaticsettings of formation, as the variation in lavachemistry is a function of mantle compositionrather than shallow-level crustal processes. Unfor-tunately, the genetic relationships between rockswithin each single chemical group cannot be estab-lished, therefore it will not be possible to evaluatetheir petrogenetic evolution in detail. The petroge-netic discussion here will therefore be restrictedto an identification of the possible mantle sourcesof the distinct lava groups and their related tec-tonic setting of formation. In particular, the overallREE and HFSE contents, and their degree ofdepletion or enrichment, are usually considered adistinctive geochemical characteristic of magmatypes and their related mantle sources (Pearce2003; references therein).

The transitional–alkaline basalts display incom-patible element and REE characteristics(Fig. 5a,b) very similar to those of oceanic islandbasalts (OIB) from various modern seamounts (LeRoex et al. 1983, 1985; Lipman et al. 1989; Haase& Devey 1996), suggesting that this basalt repre-sents seamount material formed by magma gener-ation associated with mantle plumes.

The Th/Yb and Ta/Yb ratios are included in theMORB–OIB array (Fig. 6), thus indicating thatthese rocks were generated from an enriched man-tle source in within-plate oceanic settings – that is,without any influence from continental crust mate-rial. The Zr/Y ratios (2.4–7.6), which are in thetypical range of values for within-plate OIB(Pearce 1982), confirm this conclusion.

The variable enrichment in LREE with respectto HREE observed in these rocks (Fig. 5b;Tables 1–3) suggests that they were generatedfrom variably enriched mantle sources. Haase andDevey (1996) have modeled the possible mantlesource of variably enriched rocks from the EasterSea Mount Chain using the (Dy/Yb)N vs (Ce/Yb)N

diagram of Figure 7. This diagram is then used tomodel the mantle sources of transitional–alkalinebasalts from the Subpelagonian mélange units,and shows that the intraplate rocks studied in thepresent paper are consistent with low-degree(approximately <5–7%) partial melting of a theo-retical plume source.

Similar transitional and alkaline Triassic volca-nic rocks are documented in several localities ofthe Hellenides, and are interpreted as having


originated in intraplate oceanic island settings(Capedri et al. 1997; Pe-Piper 1998; referencestherein). Although transitional–alkaline basaltsstudied in the present paper are not unequivocallydated, it is reasonable to assume that they origi-nated in a similar tectonic setting. This conclusionhas also been postulated for transitional–alkalineand alkaline volcanic rocks included in the Avdella(Jones & Robertson 1991), Koziakas (Saccani et al.2003) and Agoriani (Photiades et al. 2003)mélanges.

The chemistry of the high-Ti basalts generallysuggests melt generation in a MOR tectonic set-

ting. According to Pearce and Norry (1979), theZr/Y ratios (1.8–4.2) indicate that these rocks orig-inated from partial melting of primary or slightlyenriched mantle sources. This conclusion is inagreement with the occurrence in this groupof both the N- and E-type MORB describedpreviously.

The elemental ratios plotted in Figure 6 for theN-MORB studied in the present paper are verysimilar to those of modern primitive N-MORB(Sun & McDonough 1989), and are generally com-patible with a genesis from primary magmas orig-inating from depleted N-MORB-type suboceanicmantle sources, with no influence of enriched OIB-type material. In the model shown in Figure 7(Haase & Devey 1996), the N-MORB are compat-ible with variable degrees of partial melting of atheoretical depleted MORB mantle source.

In contrast, E-MORB from the various Subpel-agonian mélange units display Th/Yb vs Ta/Yb vari-ations (Fig. 6) that plot in the middle of the MORB–OIB array and are very similar to those observedin modern primitive E-MORB (Sun & McDonough1989); therefore, they possibly represent meltsderived from more enriched sources or, alterna-tively, from lower degrees of partial melting whencompared with N-MORB. The general enrichmentin large ion lithophile elements and LREEobserved in Figure 5c,d is in accordance with thisconclusion. Analogous basalts from the Easter SeaMount Chain (Haase et al. 1997) and Easter micro-plate rift (Haase 2002) have been interpreted asoriginating from depleted mantle sources variablymetasomatized by OIB-type components. In themodel presented in Figure 7 (Haase & Devey 1996),although one sample displays quite a high (Ce/Yb)N

ratio, E-MORB are generally compatible with atleast 9% partial melting of a theoretical mixedplume/MORB mantle source.

Fig. 6 Th/Yb vs Ta/Yb diagrams (Pearce1982) for basaltic rocks from (a) Rubik com-plex and Simoni mélange, Avdella mélange,Koziakas mélange, and Agoriani mélange; and(b) Argolis mélange units. Compositions ofmodern normal mid-oceanic ridge basalts (N-MORB), enriched MORB and oceanic islandbasalts (×) are from Sun and McDonough(1989).

BONINITEN-MORB

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E-MORB

OIB

0.001

0.01

0.1

1

10

0.01 0.11 10Ta/Yb (p.p.m.)

WPB

BONINITE

E-MORB

WPB

MORB - OIB

Arra

y

Upper (Iliokastron & Adheres) Unit

Middle (Dhimaina) UnitWedged Unit

Lower Unit (Potami Fm.)

BONINITE

E-MORB

N-MORB

N-MORB

Th/

Yb

(p.p

.m.) 1

2

3

N-MORB

E-MORB

OIB3

2

1

a) b)

Fig. 7 (Dy/Yb)N vs (Ce/Yb)N diagram and partial melting model (Haase& Devey 1996) for mid-oceanic ridge basalts (MORB) and transitional–alkaline basaltic rocks from the Mirdita–Subpelagonian mélange units.(�), normal MORB; (�), enriched MORB; (�), transitional–alkalinewithin-plate basalts.

0.8

1

1.2

1.4

1.6

1.8

0 2 31 4

(Ce/Yb)N

3%

20%15%

MORB sourceMixed source

Plume source

10%

9%

8%

7%

10%

5%

10%

7%

5%

6%

5 6

(DyYb)N

R9


Ratios of highly incompatible trace elements aregenerally influenced little by small extents of frac-tional crystallization, and are believed to reflecteither the source characteristics or the degree ofpartial melting (Saunders et al. 1988). The Y/Nbvs Zr/Nb ratio diagram of Figure 8 is then usedfor depicting the influence of a plume source onMORB composition. E-MORB plot on the mixingline between OIB source and depleted N-MORBsource components (Sun & McDonough 1989), andmost of them plot close to the typical E-MORBcomposition. In contrast, elemental ratios for theN-MORB indicate a lower or absent influence froman OIB source component with respect to the E-MORB (Fig. 8). Modern analogs are found in theSouthwest Indian (Le Roex et al. 1983) and Amer-ican–Antarctic Ridges (Le Roex et al. 1985), wherethe chemical composition of basalts ranges frompure plume-type (Bouvet mantle plume) OIB topure MORB (Fig. 8). Alternatively, E- and N-MORB may have derived from a common mantlesource, where the former represent melts derivedfrom a lower degree of partial melting with respectto those of the latter. However, the difference in

the Th/Ta and Th/Tb ratios of the two basalticseries suggests that they likely represent meltsderived from compositionally distinct mantlesources. In fact, the (Th/Ta)/(Th/Tb) ratios are <3.0and >3.0 for E-MORB and N-MORB, respectively.E-MORB from various localities of the Hellenidesshowing similar geochemical characteristics havebeen related by many authors to the interactionbetween the uprising depleted oceanic astheno-sphere and OIB-type plume material during theinitial stage of oceanic spreading (Jones & Robert-son 1991; Robertson & Karamata 1994; Pe-Piper1998; Saccani et al. 2004b).

The MORB/IAT intermediate basalts haveLREE concentrations (Fig. 5k) and Zr/Y ratios(<2.0) significantly lower than those of MORB,suggesting that they originated by partial meltingof mantle sources that were more refractory withrespect to the MORB source. Similar REE pat-terns are observed in some SSZ ophiolitic basaltsfrom southern Chile (Klein & Karsten 1995), thePhilippines (Yumul 1996) and Albanides–Helle-nides (Bortolotti et al. 2002b; Saccani et al. 2004a),which are considered the product of the melting ofan SSZ mantle wedge that had already undergoneMORB extraction. Moreover, the marked LREEdepletion (LaN/SmN = 0.02–0.28) of these basalts,coupled with medium HREE concentrations simi-lar to those of MORB, suggest that the SSZ mantlewedge did not undergo any significant enrichmentby subduction-related fluids, except water.

The very low-Ti (boninitic) basaltic rocks showmore pronounced HREE and HFSE overalldepletion coupled with variable LREE relativeenrichment when compared with MORB andMORB/IAT intermediate basalts (Fig. 5). This iscommonly interpreted as resulting from a highdegree of partial melting of progressively morerefractory mantle sources variably enriched in themost incompatible elements (LREE and LFSE)from subduction-derived hydrous fluids (Pearce1982, 1983; Beccaluva & Serri 1988). In particular,high degrees of melting of progressively refrac-tory sources under hydrous conditions result in aTi decrease with a (La/Sm)N increase (Beccaluva& Serri 1988), as can be observed in Figure 9.

Similar petrogenetic interpretations have beenproposed for analogous MORB/IAT basalts andvery low-Ti boninitic rocks from the northernMirdita, Pindos and Vourinos ophiolitic complexes(Beccaluva et al. 1994; Bortolotti et al. 2002b;Saccani & Photiades 2004; Saccani et al. 2004a). Inparticular, Saccani et al. (2004a) have suggestedthat MORB/IAT intermediate basalts from Mird-

Fig. 8 Y/Nb vs Zr/Nb diagram for mid-oceanic ridge basalts (MORB)and transitional–alkaline basaltic rocks from the Mirdita–Subpelagonianmélange units. Compositions of modern normal (N)-MORB, enriched (E)-MORB and oceanic island basalts (×) are from Sun and McDonough(1989). Arrows represent the compositional variation of ocean-floorbasalts erupted in the vicinity of the Bouvet mantle plume from the South-west Indian Ridge (SWIR, data from Le Roex et al. 1983) and from theAmerican–Antarctic Ridge (AAR, data from Le Roex et al. 1985). (�), N-MORB; (�), E-MORB; (�), transitional–alkaline within-plate basalts.

0

2

4

6

8

10

12

14

16

0 5 10 15 20 25 30 35 40 45 50 55

N-MORB

E-MORB

OIB

Zr/Nb (p.p.m.)

Y/Nb (p.p.m.)

MORB-Plumemixing line

SWIR

AAR


ita and Pindos represent 8–10% partial melting ofa lherzolitic source that had experienced some 20%previous MORB-type melt extraction. Boninitesfrom Mirdita and Vourinos originated from high-degree (30–35%) partial melting of the samesource or lower (10–20%) partial melting of arefractory harzburgitic source produced after theextraction of MORB/IAT primary melts; in bothcases, an enrichment in LREE by subduction-related fluids has been postulated (Saccani et al.2004a).

SUMMARY OF THE DISTRIBUTION OF MAFIC ROCK TYPES IN DIFFERENT MÉLANGE UNITS

A summary of the distribution and relative abun-dance of mafic volcanic and subvolcanic rocks inthe different mélange units of the Subpelagonianzone is presented in Table 4.

In the Rubik complex, N-MORB, MORB/IATbasalts and boninites are found. In addition, WPBhave been described previously (Carosi et al.1996). It should be noted that a MORB dyke(Fig. 10) cross-cutting the matrix of the mélangebelow the Western Ophiolitic Belt has been foundnear Rubik (Fig. 2a). In this area, the Rubik com-plex mainly consists of a locally laminated, shalymatrix including small (5–20 cm) blocks of veryaltered basalts and thin layers (1–2 cm) of arenites(Fig. 10).

Fig. 9 Ti vs (La/Sm)N diagram for mid-oceanic ridge basalts (MORB),MORB/island arc tholeiite (IAT) and boninitic basaltic rocks from theMirdita–Subpelagonian mélange units (simplified from Beccaluva & Serri1988). MORB and boninites from both modern oceanic environments andophiolites from various localities are reported for comparison (see Bec-caluva & Serri 1988 for references). (�), boninite; (�), MORB/IAT; (�),normal MORB; (�), enriched MORB.

32100

5,000

10,000

15,000

(La/Sm)N

20,000

Ti (p·p·m·)

Boninites

MORBs

54

Table 4 Occurrence of the different basaltic types in the main Mirdita–Subpelagonian mélange units

Mélange unit Mélange type WPB E-MORB N-MORB MORB/IAT Boninite

Rubik complex Tectonosedimentary X – X† X XSimoni mélange Tectonosedimentary – X‡ – –Avdella mélange Tectonosedimentary X X X – XKoziakas mélange Tectonic X X X – X†

Agoriani mélange Tectonosedimentary (X)§ – X§ X¶ X¶

Argolis Lower unit Sedimentary – (X) – – XArgolis Wedged unit Tectonic X – – – –Argolis Middle unit Tectonic X X†† X†† – –Argolis Upper unit Tectonic‡‡ and sedimentary§§ – (X) (X) – X

†Occurrence of dykes cross-cutting the mélanges; ‡Triassic age (M. Chiari, pers. comm., 2005); §tectonic slivers; ¶blocks in matrix; ††bothTriassic and Jurassic volcanic sequences (Bortolotti et al. 2003); ‡‡Iliokastron unit; §§Adheres mélange.

–, missing rock type; E-MORB, enriched mid-oceanic ridge basalt; IAT, island arc tholeiite; N-MORB, normal MORB; WPB, within platebasalts; X, occurring rock type; X, volumetrically prevailing rock type; (X), very subordinate occurrence.

Fig. 10 Close view of a mid-oceanic ridge basalt dyke (Dy) intrudingthe Rubik complex near Rubik. In this area, the mélange consists oflaminated shaly matrix (LM) including basaltic blocks (BB) and areniticlayers (A). Photograph by M. Chiari.


All the samples from the Simoni mélangetreated in the present paper display E-MORBaffinity and are Late Triassic in age (M. Chiari,pers. comm., 2005). Nonetheless, Shallo (1991)reported the occurrence of both high-Ti and low-Ti (IAT) basaltic blocks.

On the basis of data presented in the presentpaper and data from other published studies(Kemp & McCaig 1984; Jones & Robertson 1991;Jones et al. 1991), the Avdella mélange includes alarge variety of rock types, with the exception ofMORB/IAT basalts, which are, however, found inthe overlying ophiolitic sequence (Saccani & Pho-tiades 2004). It should be noted that the occur-rence of boninitic blocks and pillow sequences hasnever been documented before in this mélangeunit.

The Koziakas mélange is a tectonic mélange con-sisting of a packet of stacked thrust-bound slices,representing distinct volcanic sequences, fre-quently cross-cut by dykes of various nature,sometimes topped by radiolarian cherts. Thesevolcanic sequences consist of three composition-ally distinct groups of mafic lavas: transitional–alkaline WPB, E-MORB and N-MORB. Boniniticbasaltic andesites are found as dykes cutting indi-vidual volcanic sequences. However, in the Filiraarea (Fig. 2c) boninitic dykes cross-cut stackedslices of E-MORB and WPB sequences, as well astheir relative tectonic contact, thus suggestingthat they have been intruded after the emplace-ment of these slices (Saccani et al. 2003).

The Agoriani mélange is a tectonosedimentarymélange (Photiades et al. 2003) and includes alarge variety of basaltic rocks: WPB and N-MORBin the tectonic slivers; and MORB/IAT and boni-nitic basalts in blocks included in the sedimentarymatrix. The first are volumetrically very subordi-nate, whereas the latter largely prevail. Photiadeset al. (2003) have observed that MORB/IATbasalts in the Agoriani mélange display closegeochemical similarities to the same rock types involcanic sequences from the north (Bortolotti et al.1996, 2002b) and south (Hoeck et al. 2002) Mirditaophiolites.

The Argolis mélange displays a very compositescenario of compositions and types of basalticrocks. The Lower unit, which is dominated by sed-imentary processes, is almost entirely composed ofboninitic rocks and very subordinate E-MORB.The Wedged unit, which is a tectonic slice at thebase of the Middle unit (Fig. 2e), is exclusively rep-resented by volcanic sequences with transitionalwithin-plate affinity. The Middle unit is the most

significant mélange unit in Argolis and consists ofa tectonic mélange with slices representing dis-tinct volcanic sequences showing both Triassic andJurassic ages (Bortolotti et al. 2003; Saccani et al.2004b). Basaltic sequences included in it aremainly represented by both E- and N-MORB andsubordinate transitional–alkaline WPB. Both theE- and the N-MORB equally show Triassic andJurassic ages.

The Upper unit consists of both tectonic(Iliokastron unit) and sedimentary (Adheres unit)mélanges and is largely composed of boniniticblocks and scarce E- and N-MORB.

DISCUSSION AND CONCLUSION

According to Tankut et al. (1998), different mate-rials included in mélanges may provide importantconstraints for evaluating the contribution, natureand evolution of the possible source areas, as wellas for the interpretation of the processes of theincorporation of these materials during mélangeformation. Materials from the arc (mainly SSZ-type rocks) are, generally, deposited in the trenchaxis, accretionary prism, forearc region and back-arc, although by a variety of sedimentary pro-cesses during both subduction and obductionphases. In contrast, materials from the subductingplate (MORB and OIB) are tectonically incorpo-rated into mélanges through thrusting that juxta-poses different segments of the oceanic basinduring both subduction and obduction. Moreover,materials from the back-arc (both MORB and SSZrocks) may eventually be tectonically incorporatedduring obduction.

The data presented in the present paper indi-cate that a compositional (in terms of rock types)distinction between mélange units in which sedi-mentary or tectonic processes prevail can beobserved (Table 4). Mélange units formed mainlythrough sedimentary processes are characterizedby the prevalence of materials derived from SSZsettings (boninites and MORB/IAT basalts),whereas in those mélanges where tectonic pro-cesses prevail, oceanic materials (MORB and OIB)predominate. In contrast, there is no composi-tional distinction between structurally similarmélange units from the different sectors of theAlbanide–Hellenide Ophiolitic Belt. This impliesthat the Subpelagonian mélanges may be regardedas a unique mélange belt (extending from Helle-nides to Albanides, and possibly to Dinarides), theformation of which was largely dominated by the


mechanisms of the incorporation of the differentmaterials.

All mafic volcanics surfacing in the Albanide–Hellenide ophiolites (Saccani et al. 2004a; refer-ences therein), with the only exception being IAT,are found in the subophiolitic mélanges studied inthe present paper. However, IAT are volumetri-cally the most abundant rock types among theSubpelagonian ophiolites (e.g. Mirdita EasternOphiolitic Belt, Pindos, Vourinos); therefore, theirabsence implies that the rocks forming the majorportion of the intraoceanic arc did not contributeto the mélange formation. In contrast, the largeoccurrence of boninites and MORB/IAT basaltsin mélanges dominated by sedimentary processes(Table 4) suggests that the contribution of theupper plate is restricted to the forearc region. Inaddition, in the Koziakas mélange, boninitic dykescross-cut mélange portions consisting of tectoni-cally juxtaposed E-MORB and OIB sequences(Saccani et al. 2003). The occurrence of largemasses of OIB sequences indicate that thesemélange portions most likely originated from thesubducting plate materials in accretionary wedgesduring subduction; therefore, it can be supposedthat this boninitic magmatism affected the fore-most portion of the forearc setting.

The occurrence in the Rubik area of a MORBdyke intruding the sedimentary matrix of theRubik complex (Fig. 10) indicates that this mag-matism was active during (or after) the formationof this mélange. According to Saccani et al. (2004a;references therein), MORB, MORB/IAT and bon-initic magmatisms may have developed towardsthe back-arc during an incipient arc spreadingstage (see below). In consequence, the origin ofthis portion of the mélange from a back-arc/innerarc setting can be postulated. In general, theoccurrence of boninitic and MORB dykes in somesubophiolitic mélanges leaves few doubts aboutthe persistence of these magmatic events during(or soon after) the emplacement of some mélangeportions. This is in agreement with the ages ofmetamorphic soles, which are similar to those ofthe ophiolitic sequences, thus suggesting thatobduction occurred almost contemporaneouslywith the formation of the ophiolitic sequences(Bébien et al. 2000; references therein).

One of the main objectives of the present studyis to evaluate the nature and tectonic significanceof magmatic events that occurred in the Subpelag-onian sector of the Tethys, as revealed by theoceanic crust material included in the differentmélange units. From the data presented above, it

results that the ophiolitic mélanges studied in thepresent paper include Jurassic N-MORB, MORB/IAT and boninitic basalts, which are very similarto their equivalents represented in the Jurassicophiolites (Fig. 4b), together with fragments ofTriassic N- and E-MORB sequences and Triassictransitional–alkaline WPB, which are not cur-rently found in the Mirdita–Subpelagonian ophi-olitic sequences.

These materials are then very useful for depict-ing the magmatic and geodynamic evolution of theMirdita–Subpelagonian Oceanic Basins. In fact,the various Triassic magmatic rocks included inthese mélanges, together with the associatedJurassic rock types, as well as with their ophioliticanalogs, provide further constraints for improvingand integrating the tectonomagmatic and geody-namic models proposed for the Mirdita and Sub-pelagonian Jurassic ophiolites.

Models for the tectonomagmatic evolution ofthe Subpelagonian branch of the Tethys (Pindosocean) in the Hellenide sector have previouslybeen suggested by some authors on the basis ofTriassic magmatic rocks from various tectoniczones of the Hellenides (Pe-Piper 1998); the occur-rence of Triassic ophiolitic sequences in the Argolismélange (Saccani et al. 2004b); and the petroge-netic characteristics of Jurassic ophiolites (Saccani& Photiades 2004; Saccani et al. 2004a; referencestherein). Models for the Mirdita sector of the Pin-dos ocean, based on the petrologic and geologicalcharacteristics of the Albanian ophiolites havebeen proposed by Beccaluva et al. (2005) and Dileket al. (2005). On the basis of the data presented inthe present paper, these models can be integratedas summarized below.

From the Late Paleozoic–Early Triassic, theextensional tectonics affecting Gondwana trig-gered the rifting of the continental lithospherebetween the forthcoming Adria and Pelagonianmicroplates. The associated magmatic activity wascharacterized by the formation of shoshonitic andcalc-alkaline series (Bébien et al. 1978; Pe-Piper1998) with subduction-related geochemical charac-teristics inherited from a Hercynian subductionbelow Gondwana (Pe-Piper 1998; referencestherein). This rifting was also characterized by theeruption of chemically enriched alkaline basalts,suggesting that an OIB-type mantle source hadbeen active since the Early(?)–Middle Triassic(Jones & Robertson 1991; Pe-Piper 1998). The old-est dated MORB (Bortolotti et al. 2003, 2004a)indicate that the persisting extension between theAdria and Pelagonia microplates lead to the upris-


ing of a primitive asthenosphere and generation ofthe early oceanic crust, starting from the MiddleTriassic (Fig. 11a). The variable interactionbetween the uprising primitive asthenosphere andthe OIB-type mantle source(s) resulted in the gen-eration of E-MORB as the oceanic basin formed.Subsequently, the oceanic crust evolved to N-MORB composition as a consequence of partialmelting of pure suboceanic mantle (Saccani et al.2004b). At this stage, enriched transitional–alka-line basalts may have erupted either onto thepassive continental realms or in oceanic islands(Pe-Piper 1998). During the Jurassic, the oceanicspreading involved only suboceanic mantle sourcesand their partial melt derivatives, as indicated bythe absence of E-MORB and WPB coupled withthe massive occurrence of N-MORB, nowrecorded by the ‘western-type’ ophiolites (Bec-caluva et al. 1994; Bébien et al. 2000; Saccani et al.2004a). Starting from the Middle Jurassic(Fig. 11b), the tectonic regime was dominated byintraoceanic convergence associated with develop-ment of the SSZ magmatism now represented bythe IAT ophiolites of Mirdita and Vourinos (Bec-

caluva et al. 1984, 1994; Hoeck et al. 2002; Saccaniet al. 2004a). At this stage, an E-MORB crust andWPB (seamounts) may have been tectonicallyemplaced in the forearc. Afterwards (Fig. 11c), theprogressive slab roll-back led to mantle diapirismtoward the forearc and incipient arc spreadingassociated with partial melting of variablydepleted mantle sources with production ofMORB, MORB/IAT and boninitic magmas in bothforearc and inner arc regions (Beccaluva et al.2005). The age of the metamorphic soles (Sprayet al. 1984; Bébien et al. 2000) and much tectonicevidence (Bortolotti et al. 2004b) indicate thatobduction was initiated, contemporaneously withthe formation of the SSZ crust, during the Middle–Late Jurassic (Fig. 11c). During obduction, anN-MORB crust was incorporated into the sub-ophiolitic mélange mainly by tectonic processes,whereas rocks from the forearc region (MORB/IAT and boninites) were incorporated mainlythrough sedimentary processes. The present-daysetting of the Mirdita–Subpelagonian ophiolites(Fig. 11d) was reached in the lower Eocene (Dileket al. 2005).

ACKNOWLEDGEMENTS

This research was supported by M.I.U.R (ProjectPRIN 2003) and by funds granted by the Univer-sity of Ferrara and by I.G.M.E. of Athens. Theauthors are grateful to V. Bortolotti, M. Fazzuoli,A. Kodra and G. Principi for providing some of thesamples from the Mirdita mélange units; L. Bec-caluva for scientific discussion; and M. Chiari fordiscussions on radiolarian ages. Many thanks go toR. Tassinari for analytical support. M. Shallo isgratefully acknowledged for his constructive com-ments. We thank Y. Dilek, Y Ogawa, V. Bortolottiand P. Spadea for inviting this contribution to thisspecial volume.

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