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Volume n° 6 - from P55 to PW06

32nd INTERNATIONAL GEOLOGICAL CONGRESS

EUROPEAN SUBCONTINENTAL MANTLE AS REVEALED BY NEOGENE VOLCANIC ROCKS AND MANTLE XENOLITHS OF

Leaders: Field Trip Guide Book - P69 Field Trip M. Lustrino, P. Brotzu, R. Lonis, L. Melluso, V. Morra - August 20-28, 2004 Post-Congress P69

P69_copertina_R_OK C 27-05-2004, 15:28:40 The scientific content of this guide is under the total responsibility of the Authors

Published by: APAT – Italian Agency for the Environmental Protection and Technical Services - Via Vitaliano Brancati, 48 - 00144 Roma - Italy

Series Editors: Luca Guerrieri, Irene Rischia and Leonello Serva (APAT, Roma)

English Desk-copy Editors: Paul Mazza (Università di Firenze), Jessica Ann Thonn (Università di Firenze), Nathalie Marléne Adams (Università di Firenze), Miriam Friedman (Università di Firenze), Kate Eadie (Freelance indipendent professional)

Field Trip Committee: Leonello Serva (APAT, Roma), Alessandro Michetti (Università dell’Insubria, ), Giulio (Università di Torino), Raffaele (Servizio Geologico Regione -Romagna, ) and Riccardo (CNR, Torino)

Acknowledgments: The 32nd IGC Organizing Committee is grateful to Roberto Pompili and Elisa Brustia (APAT, Roma) for their collaboration in editing.

Graphic project: Full snc - Firenze

Layout and press: Lito Terrazzi srl - Firenze

P69_copertina_R_OK D 27-05-2004, 15:34:40 Volume n° 6 - from P55 to PW06

32nd INTERNATIONAL GEOLOGICAL CONGRESS

EUROPEAN SUBCONTINENTAL MANTLE AS REVEALED BY NEOGENE VOLCANIC ROCKS AND MANTLE XENOLITHS OF SARDINIA

AUTHORS: M. Lustrino1 2, P. Brotzu3, L. Franciosi3, R. Lonis4, L. Melluso3, V. Morra3

1 Dipartimento di Scienze della Terra - Università degli Studi di Roma “La Sapienza” - Italy 2 Istituto di Geologia Ambientale e Geoingegneria (IGAG) CNR, Roma - Italy 3 Dipartimento di Scienze della Terra, Università degli Studi di Napoli “Federico II” - Italy 4 Progemisa S.p.A., - Italy

Florence - Italy August 20-28, 2004

Post-Congress P69

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Leaders: M. Lustrino, P. Brotzu, R. Lonis, L. Melluso, V. Morra

Introduction The Neogene Italian magmatism is one of the Earth’s most studied. It has attracted many researchers since XIX century because of the extremely complex Figure 1 - a) Simplifi ed geological map of Sardinia. 1= Plio-Pleistocene volcanic rocks; 2 = Oligo-Miocene geodynamic scenario in which it developed, as well as volcanic rocks; 3 = Cenozoic sedimentary cover; 4 = for the very wide chemical composition range of its Hercynian granitoids; 5 = Paleozoic and Precambrian igneous products (Lustrino, 2000a; Peccerillo, 2001; metamorphic rocks; 6 = Cambrian-Devonian Conticelli et al., 2002). metasandstones, metabasalts, metapelites (internal Many non-specialistic researchers believe that Italian nappes); 7 = Cambrian-Carbonifeous metasandstones, magmatism is concentrated only on the eastern border slates, metabasalts and metarhyolites (external nappes); 8 = Precambrian-Carboniferous metasandstones, quartzites, of the (from southern down to metapelites, orthogneiss, metalimestones (external zone); ’s Mt. Etna and the ). However, 9 = Main thrusts; 10 = Posada- line. b) Schematic it should be stressed that other loci of intense igneous occurrences of the main igneous of Italy. Volume n° 6 - from P55 to PW06 n° 6 - from Volume

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra compositions typicalofmantle-derived melts;2)the the mostmafi western Mediterraneanareaforseveral reasons:1) mantle, aswellthemagmaticevolution ofthe of thissectiontheEuropeansubcontinental interesting forinvestigating thegeochemicalsignature Studying theNeogenevolcanic rocksofSardiniais 2002). geochemical signatures(Lustrinoetal.,1996,2000, (with tholeiiticaffi to stronglyalkaline(mostlysodic)subalkaline Pleistocene volcanic rocks(~5-0.1Ma)aremildly Franciosi etal.,2003).Ontheotherhand,Plio- et al.,1997a;Lonis1997;Downes etal.,2001; related signatures(Morraetal.,1994,1997;Brotzu going fromtholeiitictocalcalkaline Lecca etal.,1997)aresubalkaline,withserialaffi al., 1981;Beccaluva etal.,1985;Morra1994; Araña etal.,1974;Savelli etal.,1979;Montigny et Oligocene-Miocene volcanic products(32-15Ma; volcanological andgeochemicalcharacteristics. The magmas withcompletelydifferent petrographic, and Plio-Pleistocenetimes. These phasesproduced distinct volcanic phasesduringOligocene-Miocene The islandofSardinia(Figs.1and2)recordstwo magmas. modifi the Alpine geodynamics,and2)theoriginof 1) theoriginofigneousactivity inrelationwith have beenproposedinordertoexplain two points: became clear, andalarge numberofhypotheses From thesestudies,acomplex petrologicalscenario 2000; Downes etal.,2001;Franciosi2003). 2000, 2002;Gasperinietal.,2000;Mattioli al., 1994,1997;Brotzu,Lustrinoet1996, available forthescientifi interpretations ofSardinianvolcanic rocksbecame half ofthe‘90sanincreasingnumberdataand being mostlyconfi petrological investigations, theonlyscientifi 32-0.1 Ma)was excluded fromdetailedgeochemical- up toafew yearsagotheSardinianmagmatism(~ Di Battistinietal.,1990;Montanini1994), With very few exceptions (e.g.,Cionietal.,1982; a majorstudyarea. model forthecircum-Tyrrhenian area,Sardiniaisthus In ordertoproposeacomprehensive magmatological (the westernborderofthe Tyrrhenian Sea)(Fig.1). Channel (inbetweenSicilyand ) andSardinia (the ), the Tyrrhenian abyssalplain,theSicilian activity duringtheNeogenearealso:northernItaly cation thataffected themantlesourcesofthese c rocksof both volcanic cycles have ned tothe‘70s.Fromsecond nity), withpeculiarwithin-plate c community(e.g.,Morraet , andsubduction- c papers c nity be investigated indetail. other circum-Mediterraneanigneousprovinces) can s.l. magmatism(arelatively commonfeatureinmany temporal transitionfromorogenics.l.toanorogenic mantle (theHercynian and Alpine orogenies);4)the events thatreworked theEuropeansubcontinental as theregion was involved intwo majortectonic composition; 3)theirgeographicpositioniscritical, only directinsightsintothesubcontinentalmantle associated withmantlexenoliths thatprovide the Plio-Pleistocene Sardinianvolcanic rocksareoften island fromnorthtosouthwithalengthofabout220 Sarda; the Oligo-Mioceneriftsystem(theso-called al., 1999andreferencestherein);2)theformationof back-arc basins(Doglionietal.,1999;Speranza opening oftheLigurian-Provençal andBalearic continental microplate,togetherwiththecoeval the eastward translationoftheSardinia- to: 1)thecounterclockwiserotationand,afterwards, including inSardinia. These extensional stressesled processes inthesouthernEuropeancontinentalcrust, caused, duringtheOligocene,faulting andrifting Carmignani etal.,1994;Lecca1997)that and extensional regimes (Hyppolite et al.,1993; Alpine compressionwas followed bytranstensive references therein). The Eocene-early Oligocene margin toward NNW(Beccaluva etal.,1994and Sea oceaniccrust)undertheEuropeancontinental the subductionof African oceaniccrust(theIonian formation ofthisbasinisconsideredtoberelated of theLigurian-Provençal asaback-arc basin. The moved eastwards inconsequenceoftheopening fi continental margin (Provence, ). This block was incrustalcontinuitywiththesouthernEuropean Up toOligocenetimes,theSardinia-Corsicablock al., 2002; Trua etal.,2002). Downes etal.,2001;Conticelli2002;Coulon al., 1999;Cebriàet2000;Lustrino subalkaline (tholeiiticandcalc-alkaline)(Turner et alkaline (sodictopotassicandultrapotassic) range ofchemicalcompositions,fromstrongly the last30Mabyamagmaticactivity withawide complex region whichhasbeencharacterizedduring The circum-Mediterraneanareaisageodynamically Africa (Gondwana) towards Europe(Laurasia). Orogeny andrelatedtotherelative movements of associated igneousactivity ispartofthe Alpine The openingoftheMediterraneanSeaand Regional geologicalsetting rst startedtorotatecounterclockwiseandthen Sardinian Trough) thatcrossesthewhole 27-05-2004, 15:39:02 Fossa EUROPEAN SUBCONTINENTAL MANTLE AS REVEALED BY NEOGENE VOLCANIC ROCKS AND MANTLE XENOLITHS OF SARDINIA P69

Figure 2 - Main outcrops of Plio-Pleistocene (dark grey) activity between 21 and 18 Ma (Beccaluva et al., and Oligo-Miocene volcanic rocks (light grey) 1985; Lecca et al., 1997; Morra et al., 1997). The km. The Fossa Sarda can be interpreted as an aborted products are subaerial and submarine, and mainly rift system. consist of andesite and dacite to rhyolite ignimbrites P55 to PW06 n° 6 - from Volume Orogenic magmatic activity associated with the and, subordinately, of basalt. The explosive and opening of these back-arc basins went from the the effusive products are interlayered and partially Trough to southern Sardinia in a time span contemporaneous. On S. Pietro and S. Antioco ranging from ~32 to ~ 15 Ma (Beccaluva et al., 1985; islands, as well as on the mainland (SW Martì et al., 1992; Morra et al., 1994; Lecca et al., Sardinia) peralkaline rhyolites have also been erupted 1997). The Sardinian volcanism occurred along and (Araña et al., 1974; Morra et al., 1994). within the Fossa Sarda and reached its climax of During the Langhian (~15 Ma) the eastward

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra Figure 3-SiO References given inthetext. Coulon etal.,1973;TS=Thisstudy. HMB=HighMgBasalt;HAB Al Basalt. B 97a=Brotzuetal.,1997a;F03Franciosi etal.,2003;C97=Conte,1997D76Dostal197673 1997 ;L97=Lonisetal.,M94Morra1994B97bBrotzu1997bD01Downes etal.,2001; (Table 1)-1-3.Representative analysesofOligo-Miocenevolcanic rocks ofSardinia.Sources:M97=Morraetal., 2 vs.K 2 O diagram(LeMaitre,2002)ofOligo-Miocenevolcanic rocks ofSardinia. 27-05-2004, 15:39:08 EUROPEAN SUBCONTINENTAL MANTLE AS REVEALED BY NEOGENE VOLCANIC ROCKS AND MANTLE XENOLITHS OF SARDINIA P69

(Table 1) - 2-3.

(Table 1) -2-3.

translation of the Sardinia-Corsica block Stopped. (e.g., Carminati et al., 1998; Doglioni et al., 1998).

As a consequence, also the opening of the Ligurian- The igneous activity in the embrional western P55 to PW06 n° 6 - from Volume Provençal and Balearic basins on the western side did not Stop: the youngest igneous of Sardinia Stopped. The oceanization processes rocks of the Oligo-Miocene volcanic cycle of Sardinia continued on the eastern side of Sardinia with (~ 15 Ma; south-west Sardinia; Araña et al., 1974; the opening of the Tyrrhenian Sea. The Sardinia- Morra et al., 1994) are contemporaneous with the Corsica block can be thus considered a continental Sisco lamproite in northwestern Corsica (~15 Ma; lithospheric portion isolated during the extensional Civetta et al., 1978) that marks the fi rst evidence of movements that produced a lithospheric boudinage the Tyrrhenian Sea’s opening.

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra Mediterranean areaandhasitscounterpartsinmany is acommonfeaturethroughouttheentirecircum- followed byPlio-Quaternaryanorogenic volcanism) Sardinia (theOligo-Mioceneorogenicvolcanic cycle The Cenozoic-Quaternarymagmaticevolution of . so-called RomanComagmaticProvince incentral- potassic toultrapotassicmagmaticactivity ofthe Sardinia), thusroughlycontemporaneouslywiththe southwest Sardinia)to~0.1Ma(,northern Oligo-Miocene cycle, from~5.3Ma(CapoFerrato; in Sardiniaabout10Maaftertheendof“orogenic” plate magmatism. This magmaticactivity developed Sarrabus areaintheSWsector)aswellwithin- in SWSardinia,N-Sorientedfault systeminthe development ofariftsystem(Campidanograben area, extensional movements resultedinthe In thewesternmostsectorofextending Tyrrhenian Figure 4-SiO References given inthetext. Pleistocene (black circles)volcanic rocks ofSardinia. Maitre, 2002)ofOligo-Miocene(whitecircles)andPlio- 2 vs.Na 2 O+K 2 O (TAS) diagram(Le Wörner, 2003;Lustrino,2003). and Hoernes,2000; Wedepohl, 2000;Bogaardand Pécskay etal.,1995;Liotard1999;Jung currently available (e.g., Wilson andDownes, 1991; CEVP) forwhichalarge set ofchemicaldatais Cenozoic European Volcanic (hereafter Sardinian volcanic rocksbelongtothewell-studied The Oligo-MioceneandthePlio-Pleistocene (Lustrino, 2003). other circum-Mediterraneanigneousprovinces 1) Earlysequences(~32-24Ma)consistingof follows (Leccaetal.,1997): The volcanic activity ofSardiniacanbeoutlinedas al., 1979;Beccaluva etal.,1985). concentrated inthe23-17Matimeinterval (Savelli et island alongthe Sardinia occurredonlyinthewesternsectorof The Oligo-Miocene(32-15Ma)volcanic activity of rocks ofSardinia The Oligo-Miocenevolcanic Fossa Sarda (Figs1and2)is 27-05-2004, 15:39:25 EUROPEAN SUBCONTINENTAL MANTLE AS REVEALED BY NEOGENE VOLCANIC ROCKS AND MANTLE XENOLITHS OF SARDINIA P69

small lava domes and subvolcanic intrusions, generally of andesitic composition; 2) From ~ 24 Ma, at the beginning of the Sardinian Rift system, the volcanic products were essentially dacitic to rhyolitic ignimbrites and subordinate lavas (Dostal et al., 1982); 3) The climax of effusive activity (21-18 Ma), during the maximum tectonic extension, was characterized by the effusion of more mafi c magmas, some of which with primitive character (Arcuentu and ; Brotzu et al., 1997a; Morra et al., 1997; Downes et al., 2001; Franciosi et al., 2003). 4) At ~ 15 Ma, the last activity was concentrated in the Sulcis Figure 5 - SiO2 vs. A.I. of the volcanic rocks of Sulcis. area (southwestern Sardinia) where also potassic peralkaline rhyolitic magmas were erupted (Araña Logudoro-Bosano. The Oligo-Miocene ignimbritic et al., 1974; Morra et al., 1994). Worth reminding products outcrop mainly in northwestern Sardinia (the is that in the Sulcis area (S. Pietro Island) is the Logudoro-Bosano area), associated with subordinate comendite type-locality (mildly-peralkaline rhyolite, calcalkaline andesitic rocks. In this area at least four MacDonald, 1974). volcanic phases have been identifi ed (Coulon, 1977; All these volcanic products have subalkaline affi nity Lecca et al., 1997). The oldest rocks consist of ash and (both tholeiitic and calcalkaline). The rocks show pumice fl ow deposits, variably welded, with rhyolitic mainly medium-K serial character; the more evolved composition. These products are overlaid by dacitic to rhyolitic lava domes. The youngest products are rocks (SiO2 > 55 wt%) tend to have high-K affi nity, in particular those from Logudoro-Bosano (northern again rhyolitic ignimbrites with variable degrees of Sardinia; Dostal et al., 1982; Lonis et al., 1997) and welding. The total thickness of this succession is Sulcis (Araña et al., 1974; Morra et al., 1994); a few > 700 m. The origin of these ignimbrites has been basaltic samples from the Arcuentu (Brotzu et al., related to partial melting of a crustal protolith with 1997a) and (Conte, 1997) districts (southern intermediate composition (Coulon et al., 1978). The Sardinia) fall within the low-K fi eld (Tab. 1; Fig. 3). extensive degree of partial melting in the crust could In summary, dacitic to rhyolitic ignimbrites are the have been caused by the ascent and the heat release of prevailing products of the Oligo-Miocene volcanic andesitic magmas (the associated andesitic sequences, activity, followed by andesitic, basaltic andesitic Coulon, 1977; Coulon et al., 1978). The least-evolved and, fi nally, basaltic lavas (Fig. 4). These rocks crop effusive rocks are found in erosion windows under the out in northern (the Anglona, Logudoro and Bosano ignimbritic covers in the Sindia and Montresta areas areas), central (Marghine) and southern Sardinia (the (northwestwern Sardinia). The volcanic sequence of Sindia (Lonis et al., 1997) is made up of basaltic to Arcuentu, Marmilla, Sarroch and Sulcis areas) andesitic lava domes and lava fl ows associated with Anglona. The volcanic products outcropping in local epiclastic breccias and ash fl ows. The evolution P55 to PW06 n° 6 - from Volume the Anglona sector are andesitic lava domes with of the volcanic suite has been modeled with an open small, interbedded ignimbritic levels overlaid by system fractional crystallization of plagioclase, volcaniclastic levels, pillow lavas and breccias of clinopyroxene, olivine and Ti-magnetite, starting andesitic composition. More to the top are welded from different parental high alumina basalts (HABs ignimbrites and, fi nally, small andesitic lava fl ows ; MgO < 7 wt%; Al O > 16 wt%). In the Montresta and pyroclastic levels of ash and pumice (Lecca et 2 3 area the outcropping rocks are mainly HABs and al., 1997). high magnesia basalts (HMBs; MgO > 7 wt%; Al2O3

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra Marghine. volcanic suite. are consideredtheparentalmagmasofwhole HMBs, representnear-primitive compositionsand with tholeiiticcharacter(Morraetal.,1997). The < 16wt%),basalticandesitesandrareandesite and lava fl the bottomtotop:basalticandesiticdomes into fourmainunitsby Assorgia etal.(1984).From continental andmarinesedimentsweredivided in southwesternSardiniaareintercalatedwith characterized bysequencesofandesiticlava fl fi followed bydensely-weldedignimbritesand, by ashandpumicefl Southward, thebottomofsequenceisrepresented Arcuentu. ash andpumicefl (Aquitanian-Burdigalian) and,fi welded ignimbrites,marineandcontinentalsediments nally, bypyroclastic fl Figure 6-SiO The volcanic sequencesof Arcuentu The central sectionofSardiniais ows (30-24Ma),effusive andexplosive 2 ow levels. vs. ow depositsfollowed bydensely- 87 Sr/ ow levels (ashandpumice). 86 Sr initialratiosofOligo-Miocenevolcanic rocks ofSardinia.References given inthetext. nally, bytheupper ows Marmilla. involvement ofcrustalassimilation. crystallization inclosedsystems,withoutstrong of themagmasdriven mainlybypolybaricfractional rocks, Brotzuetal.(1997a)proposedanevolution the basisoftraceelementvariations inthe Arcuentu and, fi Ma), effusive andpyroclastic andesites(~21-18Ma), products emplacedinsubmarinesettings(~23-21 Sardinia) theoutcroppingOligo-Miocenevolcanic Sarroch. area(Mattiolietal.,2000). Burdigalian sedimentarysuccessionofthe pillow lavas have beenrecognizedintheLower In southernSardinia,High-Mgnear-primary basaltic on thetopwithandesiticfl pile ofweldedignimbrites)occasionallyinterbedded pyroclastic fl (poorly-welded, strongly-porphyriticashandpumice 300 mthick)ismainlymadeupbypyroclastic units nally, basalticdykes andsills(~18-17Ma).On IntheSarrochdistrict(southernmost The volcano-sedimentary succession (~ ows, insomecasescovered byathick ows (Leccaetal.,1997). 27-05-2004, 15:39:31 EUROPEAN SUBCONTINENTAL MANTLE AS REVEALED BY NEOGENE VOLCANIC ROCKS AND MANTLE XENOLITHS OF SARDINIA P69

Figure 7 - 87Sr/86Sr vs. 143Nd/144Nd initial ratios of with subordinate basalts, outcropping in the Cixerri orogenic Oligo-Miocene and anorogenic Plio-Pleistocene graben, in the -Carbonia area and on S.Antioco volcanic rocks of Sardinia. References given in the text. Island. The effusive products are associated with UPV = Unradiogenic Pb Volcanics; RPV = Radiogenic subordinate pyroclastic and epiclastic breccias. The Pb Volcanics (see below). For comparison, the fi elds of Neogene Italian anorogenic (Mt. Etna, Hyblean Mts.) upper sequence consists of dacitic, rhyolitic and and orogenic (Aeolian Islands, Roman Comagmatic comenditic products, mainly in ignimbritic facies. The Province) volcanic rocks ) are also shown (References in sequence, outcropping in the Nuraxi Figus – Seruci Lustrino, 2000a and in the text). area and on S.Pietro and S.Antioco Islands, overlies Oligocene continental sediments in the northern rocks are prevailing pyroclastic and epiclastic Sulcis and the lower sequence in the Carbonia-Narcao andesitic breccias and conglomerates with subordinate area. All together, the Sulcis igneous rocks show an basalts of calcalkaline affi nity. Magmatic bodies with almost complete range of compositions from basalts intrusive rocks (gabbronoritic to gabbrodioritic in to rhyolite (with a limited SiO gap from ~58 to ~66 composition) and late-stage dykes have also been 2 wt%), the most SiO2-rich characterized by peralkaline found (Conte, 1997). Mineralogical, geochemical affi nity (Araña et al., 1974; Morra et al., 1994; Brotzu and Sr-isotope data indicate the presence of at least et al., 1997b) (Fig. 5). two rock groups evolved from different degrees of Here calcalkaline basaltic andesites, andesites and fractional crystallization and crustal contamination minor basalts (~ 28 to 17 Ma; lava domes and lava P55 to PW06 n° 6 - from Volume (at different depths) starting from different parental fl ows with associated pyroclastic and epiclastic magmas. deposits; Brotzu et al., 1997b) are overlaid by Miocene Sulcis. The Sulcis area is located in southwestern (~18 to 15 Ma) felsic rock (dacite to calcalkaline Sardinia, outside the Sardinian Rift. The volcanic rhyolites and comendites (Araña et al., 1974; Morra et products can be schematized into a “lower” and al., 1994; Brotzu et al., 1997b). Many andesitic rocks “upper sequence”. The fi rst sequence is made up by contain abundant basaltic enclaves, indicating local basaltic andesitic and andesitic lava domes and fl ows,

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra to peralkalinerhyoliteswithplagioclase(often G3) hololeucocratic(colourindex =2%)transitional accessory minerals. in G1dacites. Ti-magnetite andilmenitearethe also presentwiththelatterbeinglessabundant than Gabbronoritic glomerulesandandesiticlithicsare orthopyroxene andmicrophenocrystsofsanidine. with phenocrystsofplagioclase,clinopyroxene and G2) porphyritictoglomeroporphyriticrhyodacites magnetite, ilmeniteandapatite. fragments arepresent. Accessory phasesare Ti- gabbronoritic nodulesandandesitictoleucoandesitic ± orthopyroxene+clinopyroxene. IntheG1dacites olivine andlocallyplagioclase+biotiteamphibole up ofplagioclase+orthopyroxene +clinopyroxene ± index =15-20%)dacites,witheutaxitictextures, made G1) porphyritictoglomeroporphyritic(porphyritic (Morra etal.,1994): in composition)have beendivided intofi The rocksofthe“uppersequence”(dacitictorhyolitic chambers (Brotzuetal.,1997b). the recycling ofsettledcrystalsinzonedmagmatic in many lavas hasbeeninterpretedastheresultof mingling. The presenceofxenocrystic assemblages v groups ve rhyolitic ignimbritesofBurdigalianage(~19Ma) Neighboring areas. sanidine, plagioclaseandsubordinateanorthoclase. devitrifi G5) hololeucocraticrhyoliteswithglassy, partially are: Ti-magnetite, ilmenite,fayalite andzircon. of Na-amphiboleandaegirine. The accessoryphases sanidine, anorthoclase,quartzandmicrophenocrysts G4) phenocryst-poorcomenditesmadeupofNa- leucoandesitic blobs. magnetite andilmenite. They occasionallycontain and orthopyroxene. Accessory phasesare Ti- main phenocrysts,aswellrareclinopyroxene mantled byanorthoclase)andsanidineasthe Arcuentu andMontrestasamples.Dashedlinesrepresent MORB fl Figure 8-Nd/Pbversus sediments iscalculatedassuming1%byvolume offl and sediment/fl and D mixing between depletedmantle(S)andMORBfl of sedimentfl eclogite/fl calculated assuming2%byvolume offl (MF). Solidlinesrepresentdifferent percentagesof cated, groundmassandphenocrystsofNa- uid. Dottedlinesrepresentdifferent percentages Nd =3.26.Modifi uid, D uid partitioncoeffi uid (SF).Fluidfrom Altered MORBis High-Kcalcalkalinedaciticto Pb =0.01andD 206 ed fromFranciosi etal.(2003) Pb/ 204 Pb diagramsfor theMt. cients areD Nd =3.26.Fluidfrom uid and,for 27-05-2004, 15:39:37 Pb =0.51 uid uid EUROPEAN SUBCONTINENTAL MANTLE AS REVEALED BY NEOGENE VOLCANIC ROCKS AND MANTLE XENOLITHS OF SARDINIA P69 Volume n° 6 - from P55 to PW06 n° 6 - from Volume

Figure 9 - Simplifi ed geological sketch map of the “Upper sequence” of the Sulcis area. Modifi ed from Morra et al. (1994).

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra 1997; Brotzuetal.,1997b;Conte,Lonis of themagmas(Dupuyetal.,1974;Morra1994, variation ofSrisotopicratioswith thedifferentiation crystallization processes(AFC),asindicatedbythe been driven essentiallybyassimilationandfractional starting frombasalticparentalmelts,seemstohave evolution of Tertiary Sardinian effusive rocks, continental crust(Coulonetal.,1978),whilethe processes inthe related toanatectic ignimbrites hasbeen The genesisof rotation. block, justafterits of theCorsica-Sardinia lithospheric extension emplaced duringthe post-collisional suites have beenrelatedto the Tyrrhenian Seaand stages ofopening evidence ofthefi to lamproiticmeltsare of Langhianshoshonitic These two occurrences in north-eastCorsica. old Siscolamproite similar tothe15-Ma- features, roughly and petrographical lamproitic geochemical show shoshoniticto samples Sea. These in the Tyrrhenian Cornacya seamount,towards south-eastSardinia, unknown 12Maoldsubmerged volcano, namedthe of volcanic rocksdredgedalongapreviously Recently, Mascleetal.(2001)reportedanalyses subduction systemlinked thesetwo regions. allowed Rossietal.(1998)toproposethatthesame samples andSardinianOligo-Mioceneandesites of trace-elementabundance betweenthesedredged testify toanarc-typevolcanism. Similaritiesinterms along thewesternCorsicanmargin (Rossietal.,1998) andesitic rocksdredgedduringtheMARCOcruise More northeastward, Burdigalian(17.2-16Ma) northwards over thesouthernmargin ofCorsica. that theOligo-MioceneSardinianarcwas extending the MioceneSardinianignimbritesanddemonstrate occurrences representthenorthernequivalents of areas)byOttaviani-Spella etal.(1996). These have beenreportedinsouthCorsica(Balistraand Tre rst 1997). Initial normalized diagrams,Morraetal.(1997)proposed On thebasisoffl al., 2000)districts. and Marmilla(central-southernSardinia;Mattioliet 1997a; Downes etal.,2001;Franciosi2003) al., 2003), Arcuentu (southernSardinia;Brotzuetal., (northern Sardinia;Morraetal.,1997;Franciosi worldwide. HMBsarefoundonlyintheMontresta abundant insubduction-related geodynamicsettings The SardinianbasaltsaremostlyHABs,very source contaminationbysubductedsediments. variation ofrocksfrom Arcuentu was theeffect of Sr-, Nd-andO-isotope data,holdthattheisotopic However, Downes etal.(2001),on thebasisof al., 2003)(Fig.6). (Morra etal.,1997;Downes etal.,2001;Franciosi metasomatized byfl mantle sourceoftheMontrestaHMBs,variably a N-MORB-like spinel-bearinglherzoliteasthe responsible forthehigherSiO residual charactersofthe Arcuentu HMBswould be residual thanthoseoftheMontrestaHMBs. The Arcuentu HMBsspinel-bearingmantlesourcesmore crust. Brotzuetal.(1997a)proposedforthe (MacDonald, 1974)for peralkalinerhyolitesfromSulcis. Figure 10-FeO(tot) vs. Al 87 Sr/ 86 Sr rangesfrom0.70399to0.71127 uids fromsubductedoceanic at HREEpatterninchondrite- 2 O 2 3 andlower Al discriminationdiagram 2 O 27-05-2004, 15:39:43 3 , CaO, EUROPEAN SUBCONTINENTAL MANTLE AS REVEALED BY NEOGENE VOLCANIC ROCKS AND MANTLE XENOLITHS OF SARDINIA P69

FeO and TiO2 contents compared to the Montresta Sardinia) (Figs. 5 and 9). primary melts. Sr-isotope data for Oligo-Miocene volcanics have The peralkaline types of the Sulcis area represent about been available since the ‘70s (e.g., Dupuy et al., 10-15% by mass of the entire succession of the area 1974), but Nd-, O- and, in particular, Pb-isotope (basic to acid types) and ~30% by mass of the more data are still very scarce. The fi rst Nd and O data evolved compositions (Morra et al., 1994). Among all were reported by Downes et al. (2001) on Arcuentu the Oligo-Miocene products, the peralkaline types are rocks, while Pb-isotope data were reported by Caron <1%. The presence of such kind of lithologies in close and Orgeval (1996) and Franciosi et al. (2003) on spatial and stratigraphic relationships with calcalkaline andesite and HMBs from (north-west Sardinia), basic to acid rocks is a relatively uncommon feature. San Martino (Logudoro), (Sulcis), Peralkaline compositions [igneous rocks with molar

(central-southern Sardinia), Arcuentu and Montresta. excess of (Na2O+K2O) over Al2O3] are almost 143Nd/144Nd isotopic ratios of Arcuentu volcanic rocks exclusively confi ned to evolved compositions, both

range from 0.51270 (HMB) to 0.512185 (andesite); SiO2 oversaturated and undersaturated (i.e., trachytes, Montresta HMBs have more radiogenic 143Nd/144Nd, rhyolites, phonolites; MacDonald, 1974; Scaillet and MacDonald, 2003). The SiO oversaturated types are ranging from 0.51274 to 0.51271 (Fig. 7). 2 divided into comenditic trachyte, comendite (mildly Pb-isotope ratios on Montresta and Arcuentu HMBs peralkaline rhyolite), pantelleritic trachyte and range as follows: 206Pb/204Pb (18.609-18.707); 207Pb/ pantellerite (strongly peralkaline rhyolite). A chemical 206Pb (15.619-15.661); 208Pb/204Pb (38.408-38.747). distinction among these types is based mostly on FeO Caron and Orgeval’s (1996) results lie in the same and Al O content (MacDonald, 1974; Fig. 10). isotopic range (206Pb/204Pb (18.519-18.708); 207Pb/ 2 3 206Pb (15.640-15.679); 208Pb/204Pb (38.713-39.109). Compared to pantellerites, comendites are On the basis of such isotopic data, together with a characterized by a lower Agpaitic Index [A.I. = detailed study of incompatible trace-element ratios, (Na+K)/Al], generally lower FeO (< 7 wt%) and Franciosi et al. (2003) proposed a model to explain generally higher Al O (> 9 wt%). Comendites are the components involved in the genesis of HMBs and 2 3 generally transitional between pantellerites and the HABs from Montresta and Arcuentu. The geochemical non-peralkaline rhyolites in terms of FeO, MnO, and isotopic compositions of these magmas require Na O, TiO , Al O , CaO and MgO (MacDonald, an approximate degree of partial melting of 15% of a 2 2 2 3 1974). Peralkaline rocks occur in both continental and MORB-like, and input of two subduction components oceanic settings (e.g., Civetta et al., 1998; Kar et al., in the mantle wedge: 1) fl uids from subducted oceanic 1998; Ayalew et al., 2002). When present as relatively crust (altered MORB); 2) fl uids from subducted low-volume products, these magmas are believed sediments. Ratios among trace elements variably to represent end-products of protracted fractional compatible with fl uid and melt phases (i.e. Th/Pb, crystallization of alkali basalt magmas, whereas when Th/Nd and Sr/Nd) exclude the contribution of melts present in large volume and unrelated to mafi c and from subducted slab. Models based on isotopic ratios intermediate rocks, their origin is related to partial indicate that the pre-subduction depleted mantle melting of crustal rocks of basaltic to more silicic source of Sardinia magmas was enriched by less than compositions (see Scaillet and MacDonald, 2003 1% of both MORB fl uid and sediment fl uid released for a summary). Recently, experimental evidences of from a subducted slab (Fig. 8). genetic linkage between comendites and pantellerites Geochemical and isotopic compositions of Montresta have been highlighted by Scaillet and MacDonald volcanic rocks are homogeneous, while samples from (2003): strongly peralkaline pantelleritic melts can be Arcuentu show quite heterogeneous traits, consistent produced by protracted crystallization of high-silica with variations in mantle sources during the long (anatectic) comendites. P55 to PW06 n° 6 - from Volume time span (about 13 Ma) of volcanic activity in this The tectonic setting of peralkaline magmatism is . generally associated with within-plate oceanic (e.g., One of the most interesting aspects of the Oligo- hot-spot-related islands such as Ascension and the Miocene volcanic rocks of Sardinia is the spatial and Azores, or large, plume-related igneous provinces temporal relationships among calcalkaline mafi c to such as Iceland) or continental settings (sometimes intermediate rocks and the differentiated subalkaline evolving into continental rift systems, such as the to peralkaline rhyolites in the Sulcis area (south-west Afar). The relative scarcity of peralkaline magmatism

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra term of Mg# ofmafi mineral phases(e.g., An contentofplagioclaseand basic toacidroks,thecontinuouschemicalshiftof rocks. At Sulcis,wholerockchemicalvariation of associated withcalcalkalinebasictoacidvolcanic area canbeconsideredananomalousfeature,itsbeing this regard, theperalkalinemagmatismofSulcis tectonic settingsunrelatedtosubductionsystems.In comendites andpantelleritesastypicalproductsof magmas, allowed many authorstoconsider rare associationofcalcalkalineandesite-peralkaline in subduction-relatedsettingsandtheextremely rocks ofSardinia. References inthetext. normalized diagramofmafi Figure 11-Primitive mantle(SunandMcDonough,1989) of Furtei,,,,Bosa, Oligo-Miocene volcanic rocksoccurintheareas The mostimportantgoldmineralizationsrelatedto are associated. such asgold,copper, manganese,kaolineandzeolite, mineralizations exploited forindustrialpurposes, With theOligo-Miocenevolcanic rocksimportant and referencestherein). Brotzu etal.,1980;ScailletandMacDonald,2003, (e.g., theplagioclaseand/orclinopyroxene effect; which arelessperalkalinethancoexisting liquids peralkaline meltsafterremoval ofmineralphases 1 canbeobtainedfrommetaluminousorslightly- to theperalkalinecharacter: A.I. values higherthan In thissense,nogeodynamicmeaningcanbeascribed rhyolites orperalkalinetypes(comendites). cumulate, basalticmeltscanevolve uptosubalkaline Depending onthemineralogicalcompositionof sequence isgeneticallylinked (Morraetal.,1994). (Sulcis andesite=0.70711)suggestthatthewhole respectively) andbetweenacidintermediaterocks and peralkalinerhyolites(0.707450.70667, 87 Sr/ 86 c minerals),theoverall similarityin Sr isotopicratiosbetweensubalkaline c Plio-Quaternaryvolcanic associated withsilica,pyrite andlessersphalerite. sandwiched betweenandesitefl developed infl mineralisation ishostedinsheetedmicrofractures center, 5kmindiameter. The earliestphaseofgold Tertiary agesub-aerialcalcalkaline volcanic The Furtei Volcanic Complex (FVC)isamajor al., 1995;Dessiet1996). Sardinia) andOsilo(north-east(e.g.,Ciduet (central-southern Sardinia),Mt.Olesteddu(south-east view themostimportantlocalitiesarethoseofFurtei Montiferru andSarroch.Fromanindustrialpointof Figure 12-Nb/Nb*vs.Ba/NbandBafor Plio- compared withmafi volcanic rocks ofSardiniahave low Nb/Nb*(<1),coupled and PMstandfor rock andprimitive mantlevalues.This = Nb Pleistocene volcanic rocks ofSardinia(PSV)compared parameter refl normalized diagrams.ThemajorityofPlio-Pleistocene to otherEuropeananorogenicvolcanic rocks. Nb/Nb* R /Nb with higherBa/Nb(>20),but roughlysimilarBa, and Europe.Modifi PM /((K ects theNbanomalyinprimitive mantle- at-lying sediments and ignimbrite R c anorogenicvolcanic rocks fromItaly /K PM )*(La ed afterLustrinoetal.(2002). R /La PM ) 0.5 ; wheresubscriptsR ows. Goldis 27-05-2004, 15:39:47 EUROPEAN SUBCONTINENTAL MANTLE AS REVEALED BY NEOGENE VOLCANIC ROCKS AND MANTLE XENOLITHS OF SARDINIA P69

Figure 13 - 87Sr/86Sr vs. 143Nd/144Nd isotopic ratios for as 3.5 kilometres long and up to 1 kilometre wide, anorogenic Plio-Pleistocene volcanic rocks of Sardinia. with grades of up to 12 g/t gold in soils in the central UPV = Unradiogenic Pb Volcanics; RPV = Radiogenic area. Previous selective sampling of the individual Pb Volcanics (Lustrino et al., 2000). For comparison quartz-sulphide veins returned values typically the fi elds of Neogene circum-Mediterranean volcanic provinces are also shown. References in Lustrino et al. between 15 and 50 g/t, and as high as 220 g/t. (2002) and in the text. The Osilo epithermal vein district contains 1,600,000 tons, grading at 7.1g/t gold and 30g/t silver. This style of mineralisation is termed “stratabound” The kaolinitic deposits of Sardinia associated with and represents a large tonnage, low-grade (2g/t) gold Oligo-Miocene igneous rocks are developed on target. The average thickness of the mineralisation is primary volcanic rocks or allumo-silicatic rocks. 12-15 m, and average grades are 1.5-2.5 grams per ton Volcanic rocks at Romana (the Bosano area) show of gold, up to 5.4 g/t Au in a diamond drill hole. The a bimodal alteration. Mineral assemblage is made stratabound mineralisation is crosscut by the diatreme up of kaolinite and opal-calcedony-crystobalite; breccia, which is the predominant host to sub-vertical this assemblage replaces completely the original vuggy silica sulphide structures containing pyrite, mineralogy of the rock. Incidence of kaolinite on one enargite (copper sulphide) and gold mineralisation. hand and of crystobalite on the other is extremely Resources and reserves at Furtei (the mine started variable. Both components range between 0 and 80-

operating in 1997) are 9.3 million tons (Mt) at 2.08 g/t 95%, with complementary incidences. The scanty P55 to PW06 n° 6 - from Volume Au (about 20 tons of Au) and 15,000 tons of Cu. At economic interest for Romana kaolinitic deposits is the moment Furtei consists of an open-pit operation due to its great mineralogic variability (Novembre with a production facility capable of processing et al., 2003). Important kaoline deposits are found in 1,000,000 tons of ore annually. Currently the Furtei various areas of Sardinia (Romana, and mine produces about 780 kg of gold a year. Furtei), but only a few of them are currently exploited. The Monte Ollesteddu prospect was discovered in These deposits are mostly associated with pyroclastic 2000 as an extensive gold-in-soil anomaly, identifi ed facies and hydrothermal activity focused along faults

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Volume n° 6 - from P55 to PW06 P69 - P69 Figure 14- in thetext. Mantle IandII.References inLustrinoetal.(2002)and Asthenospheric Reservoir. EMIandEMII=Enriched Province (CEVP)arealsoshown. EAR=European igneous rocks oftheCenozoicEuropean Volcanic comparison thevaluesofanorogenicandorogenic for Plio-Pleistocenevolcanic rocks ofSardinia.For Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra The activity ismainlylocated along normalfaults Ma aftertheendofprevious orogenic magmatism. This magmatismdeveloped afterahiatusofabout10 both intheeasternandwesternsectorsofSardinia. island, thePlio-Pleistocenevolcanic activity occurs which outcroponlyalongthewesternsideof Unlike theOligo-Mioceneorogenicvolcanic rocks, Sardinia The Plio-Pleistocenevolcanic rocks of silicitization andargillifi with abundant MnandFeoxides,associatedwith sectors oftheisland,arefoundmostlyinstockwork in theOligo-Miocenevolcanic rocksinvarious Mn mineralizations,relatedtohydrothermalactivity associated withandesitic-daciticsub-volcanic bodies. (southern Sardinia)Cu,Moand Au mineralizationsare Sardinia), whereasintheSiliqua-Decimoputzuarea microdioritic intrusionsatCalabona(north-west Porphiry copperdepositsareassociatedwith (Ligas etal.,1996). interest. heulandite-rich occurrenceswithpotentialeconomic and Bosano)representthefi 2001; Lonisetal.,2002). These localities(Logudoro with riodacitic-rhyoliticignimbrites(e.g.,Cerrietal., several zeoliteoccurrences(clinoptilolite)associated Correlated toOligo-Miocenevolcanic rocksarealso Pietro island). 208 Pb/ 206 Pb vs. 207 cation phenomena(e.g.,San Pb/ rst Italianclinoptilolite/ 206 Pb isotopicratios - sector ofSardiniaare(Fig2): From northtosouth,thevolcanic areasintheeastern Patterson, 2001,andreferencestherein). and Downes, 1991;Hoernleetal.,1995; Wilson and proposed formany productsoftheCEVP(e.g., Wilson (i.e., passive riftingprocesses)as,instead,hasbeen genesis ofPlio-Pleistocenevolcanic rocksofSardinia being unlikely amantleplumeinvolvement inthe crustal controlonthegenesisofthismagmatism, of about70km(, 1984),indicateastrong the riftingprocesses,andlithosphericthickness Sea. The development ofmagmaticactivity onlyafter geodynamic evolution ofthewesternMediterranean structural evidence ofsuchtensilestressesduringthe the Oligo-MioceneFossa Sarda,istheclearest southwestern partandwhichpartiallyoverlaps Graben (Fig.1),whichcrosscutstheislandinits magmatic conduits(e.g.,atMt. Arci). The In somecases,thevents reactivated Oligo-Miocene to recent-version oftheOligoceneProvençal Basin. Tyrrhenian Sea,interpretedasthemiddle-Miocene related tothecoeval openingoftheback-arc Figure 15- after Lustrino,1999. crustal xenoliths arefromHallidayetal.(1993).Modifi Province (CEVP)andItalyarealsoshown. Scottishlower igneous rocks oftheCenozoicEuropean Volcanic comparison thevaluesofanorogenicandorogenic for Plio-Pleistocenevolcanic rocks ofSardinia.For The relative proportionofthevolcanic outcrops with afew tholeiiticcounterparts(basaltic andesites). hawaiites plusrarer alkalibasaltsandmugearites) These rocksconsistofmildly-alkalinelavas (mostly Pasini, 1973;Lustrino, 1999;Lustrinoetal.,2002). limestones anddolostones(,1939;Savelli and crystalline basement,aswellonMesozoic Volcanic rocksofthisdistrictrestonaPaleozoic 206 Pb/ (orBaroniearea;3.6-2.0Ma). 204 Pb vs. 207 Pb/ 204 Pb isotopicratios 27-05-2004, 15:39:52 ed EUROPEAN SUBCONTINENTAL MANTLE AS REVEALED BY NEOGENE VOLCANIC ROCKS AND MANTLE XENOLITHS OF SARDINIA P69

Figure 16 - Delamination, detachment and sinking of overthickened lithospheric root during the end of Hercynian orogeny. 1 = Future source of Cenozoic European Volcanic Province products, with within- plate geochemical features and strong asthenospheric

signature; 2 = Future P55 to PW06 n° 6 - from Volume source of the majority of the Plio-Pleistocene volcanic rocks of Sardinia (UPV group of Lustrino et al., 2000), with strong lower crustal and lithospheric signature.

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra hundreds ofmetersto1km,lyingonupperMalm mugearites), whosewidthvaries from several outcrop ofalkalinelavas (alkalibasalts,hawaiites, plateaus outcroppingover ~150 Km NW-SE trendingfaults andtheirproductsform the volcanic vents arelocatedalongNE-SWand is ~80%alkalineand~20%tholeiitic.Many of S. PietroBaunei et al.,2001). abundant occurrenceofmantlexenoliths (Beccaluva Pasini, 1973).Some localitiesarecharacterizedbythe the Oroseicanyon inthe Tyrrhenian Sea(Savelli and on thecontinentandinnow-submerged areaof volcanic activity was almostcontemporarytothat Finally, itisnoteworthy thatthebeginning ofthe largely overlapping (Beccaluva andMacciotta,1983). products, withtholeiiticandalkalineK/Arages saturation characterandgeographicpositionofthe correlation betweentimeofemplacement,silica Battistini etal.,1990;TS=ThisStudy. et al.,2000;M94=Montanini1994;DB90Di et al.,2000;L02=Lustrino2002;G00Gasperini Lustrino, 1999;L*00=2000;LLustrino Pleistocene volcanic rocks ofSardinia.Sources:L99= (Table 2)-1-2.=Representative analysesofPlio- , (2.6Ma). This isa5.5kmlong 2 . There is no is . There Barisardo Orosei-Dorgali volcanic area(Lustrino etal.,2002). volcanics beingadismemberedportionofthelarger the Orosei-Dorgali rocksfavor thehypothesisofthese Chemical, mineralogicalandstructuralsimilaritiesto NW-SE fault system,paralleltotheshoreline(Fig.2). not easilyrecognizableandthefl from afew metersupto~20m. The volcanic vent is al., 2000). The thickness ofthelimestonesisvariable limestones (Simboli,1963;Lustrino,1999;Lustrinoet represented bya50m Capo Ferrato fault roughlyparalleltotheshoreline(Fig.2). intrudes Paleozoic phyllitesandislocatedalongaNS 1965; Lustrinoetal.,1996,1999,2000). This neck small ultramafi Km to-evolved alkalinerocks(mugearitesandtrachytes; Sardinia. The mainrocktypesaremainlyintermediate- volcanic activity ofthePlio-Pleistocenecycle in Rio Girone 1937; Lustrino,1999;Lustrinoetal.,2000). rarer transitionalbasalticandesites(Fig.2;Lauro, The mainrocktypesarehawaiites/mugearites plus eastern SardiniaandrestsonHercynian granitoids. 2 ) islocatedsouthofS.PietroBauneiincentral- (noageavailable). This smalloutcrop(~5 (noageavailable). This smalloutcropis (5.3-2.3Ma). This representsthefi c xenoliths ofmantleorigin(Calvino, 2 neckofbasanitewhichhosts ow iscanalized ina 27-05-2004, 15:39:59 rst EUROPEAN SUBCONTINENTAL MANTLE AS REVEALED BY NEOGENE VOLCANIC ROCKS AND MANTLE XENOLITHS OF SARDINIA P69

(Table 2) - 2-2. cones (e.g., Logudoro, to the north) are tholeiitic (basaltic andesite) and alkaline lavas (hawaiites, Brotzu et al., 1975; Lustrino et al., 2000; Petteruti- mugearites) (Beccaluva et al., 1975; Lustrino, 1999; Lieberknecht et al., 2003). The volcanic rocks are Lustrino et al., 2000). present as dikes and ellipsoidal domes which rest on Montiferro (3.9-2.8 Ma). This volcanic complex Hercynian granitoids (Figs 1 and 2). (~400 Km2) is made up of mafi c (basanites, hawaiites, In the central-western sector, the scenario is more and mugearites) and differentiated products (trachytes complicated, with the presence of large volcanic and phonolites) present mainly as fl ows up to 300 complexes (e.g., Montiferro and Mt. Arci) and meters thick. The mafi c alkaline rocks host mafi c widespread basaltic plains (Campeda-Planargia- and ultramafi c nodules (both of mantle and cumulus ). Starting from north to south these are: origin), as well as crustal xenoliths (Di Battistini et al., Logudoro (2.4-0.1 Ma). The northernmost outcrops of 1990; Lustrino, 1999; Lustrino et al., 2000; Beccaluva the Plio-Pleistocene volcanic cycle of Sardinia are also et al., 2001; Authors’ unpublished data). the youngest ones (as young as 0.1 Ma). This district Gerrei area (3.8-2.1 Ma). The volcanic rocks is mostly made up of small central vents and cinder- belonging to this district (central-southern Sardinia; 2 spatter cones outcropping over an area of ~500 km Fig. 2) overlie Miocene marly-arenaceous or (Beccaluva et al., 1976; Lustrino, 1999; Gasperini et calcareous sediments (Lauro, 1937; Lustrino et al., al., 2000; Lustrino et al., 2000; Petteruti-Lieberknecht

1996, 2000; Lustrino, 2000c). This area includes P55 to PW06 n° 6 - from Volume et al., 2003). This district is the best known site in several outcrops: the lava plateau of about 50 Km2 Sardinia for fi nding mantle xenoliths (see below). of Giara di (2.76-2.05 Ma), Giara di Serri Campeda-Planargia-Abbasanta- basaltic (2.27±0.09 Ma), Pitzu Mannu (2.11±0.09 Ma), Mt. plains (3.7-3.5 Ma). These basic-to-intermediate lava Guzzini (2.62±0.11 Ma), Mt. Pizziogu (3.54±0.35 fl ows represent the widest Plio-Pleistocene volcanic Ma), Corona Arrubia (2.2±0.11 Ma), Taccu Idda- 2 plateau in Sardinia (~850 Km ; Fig. 2). These Taccu Maiore (2.08±0.25 Ma), Taccu Piccinnu volcanic rocks, partially covering other volcanic (2.62±0.24 Ma), and the Iras-Siddi- plateau complexes (e.g., Montiferro to the west) and cinder

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra stability fi out ondiffering initialcompositions. Above thegarnet of contrastingresultsfromexperimentalstudiescarried garnet-in curve isrepresentedby ashadedareabecause Lustrino (2001). may delaminate,detach andsinkintouppermantle. After (represented bygarnetamphiboliteoreclogite/granulite) gradient reaches acriticalvalue,restiticlower crust with laterincreaseindensityofrestiticmaterial.If too, lower crustallithologiesareforced tomeltpartially, continent collisionandthickening oflower crust.Here Arrow “2”:effect oftectonicpilingfollowing continent- to increasingvolumes ofgarnet substituting amphibole. aqueous porefl is forced tomeltpartiallybydehydration,notrequiring basaltic batches onamphiboliticlower crust,whensystem bold type:rock types. Arrow “1”:effect ofarrivalhot ± otherphases.Italics:stablemineralogicalassemblages; garnet producedbyreaction:amph+pl=melt±gtcpx coincides withtheappearanceofclinopyroxene and fi dehydration partialmelting.Below thegarnetstability breakdown ofamphibolemayform newgarnetduring saturated solidus,becauseexcesswater provided bythe interrupted bydottedline:H Lustrino, 2001for references). Continuousline,partly assemblages asdeducedfromseveral sources(see Figure 17-Compositephasediagramsfor amphibolitic basaltic andesitesandhawaiites. 1999; seebelow). The mostcommonrocktypesare abundant intheZepparaMannaarea(Lustrinoetal., 20 cmindiameter)ultramafi Almost allthealkalinelavas hostvariably-sized (upto (2.49-3.84 Ma;K/Aragesfrom Assorgia etal.,1983). eld, vapour-absentsolidus,representedbydashedline, eld, vapour-absentsoliduscoincideswithH uid. Assemblage increases indensity, due 2 O-saturated solidus.The c xenoliths, particularly xenoliths, c 2 O- Guspini and Plio-Pleistocenevolcanic cycles. of volcanic rocksbelongingbothtoOligo-Miocene rhyolites) arepresent,and2)thiscomplex ismadeup (Table 2) composition; differentiated products(bothSiO of Sardiniahave mainlymafi In summary, thePlio-Pleistocene volcanic rocks centimetric, disruptedmantlefragments. characterized bythepresenceofmillimetric-to- (Lustrino etal.,2000;Fig.2). This outcropis Graben, intrudingOrdovician metasandstones outcropping onthewesternbranchofCampidano alkaline neck(about20m)ofhawaiitic composition SiO peculiarities: 1)thisistheonlyplacewherefelsic 1999; Lustrinoetal.,2002). counterparts andshow atholeiiticcharacter(Lustrino, subalkaline rocksarelessprimitive thantheiralkaline types arealsofound(Lustrinoetal.,1996). The sodic affi rocks aremildly-to-stronglyalkaline,mainlywith rocks ofSardiniaarereportedin Table 2. The alkaline Representative analysesofPlio-Pleistocenevolcanic to rhyolite)arepresent(Figs.2,4). and phonolite)subalkalinetypes(tholeiiticbasalt basanite, hawaiite, mugearite,benmoreite,trachyte et al.,2003).Bothalkaline(basanite,alkalibasalt, et al.,1996,2000,2002,2003;Petteruti-Lieberknecht Battistini etal.,1990;Montanini1994;Lustrino oversaturated andundersaturated) occuraswell(Di 2 -oversaturated volcanic rocks(dacitesand . (noageavailable) This isavery small nity, althoughsomeslightlypotassic Mt. Arci al., 2003). 2000; Petteruti-Lieberknechtet (Lustrino, 1999;Lustrinoetal., andesites withtholeiiticaffi 2). The rocksareallbasaltic Gulf,respectively (Fig. and northernextremities ofthe limited outcropsatthesouthern available).zone- are These Mt. Arci productsshow two volcanic rocksofSardinia,the Among thePlio-Pleistocene Lieberknecht etal.,2003). 1994; Lustrino,1999;Petteruti- et al.,1982;Montanini (Beccaluva et dacitic torhyoliticlava fl Graben (Fig. the easternsideofCampidano volcanic complex locatedalong Capo Frasca- (3.8-2.6Ma). This isa c tointermediate 2), withabundant al., 1974; Cioni (noage 27-05-2004, 15:40:12 ows nity 2 - EUROPEAN SUBCONTINENTAL MANTLE AS REVEALED BY NEOGENE VOLCANIC ROCKS AND MANTLE XENOLITHS OF SARDINIA P69

The tholeiitic-alkaline association and its petrogenetic meaning was investigated in detail by Lustrino et al. (2002). As observed for other Italian (e.g., Hyblean Mts., Sicily; Beccaluva et al., 1998; Trua et al., 1998) and European volcanic rocks (e.g., Bas Languedoc, France; Dautria and Liotard, 1990; Liotard et al., 1999), the close spatial and temporal association of these two different lithologies, as well as similar incompatible trace-element ratios and overlapping Sr-Nd-Pb isotopic ratios have all been related to a single mantle source which melted to different degrees: about 3 to 6 % for mafi c alkaline rocks and about 8 to 12 % for tholeiitic rocks. The tholeiitic group is characterized by a slightly higher 87Sr/86Sr and lower 143Nd/144Nd than alkaline rocks, probably linked to some limited degree of crustal contamination during stagnation in magma chambers. Some of the most-evolved subalkaline volcanic rocks (e.g., rhyolites from Mt. Arci, in central Sardinia) appear to be mostly related to fractionation of tholeiitic magmas plus assimilation of crustal components via AFC processes (Montanini et al., 1994). Pure crustal anatectic partial melts with strongly Sr radiogenic compositions (87Sr/86Sr = 0.7053 to 0.7155) are also reported (Cioni et al., 1982; Montanini et al., 1994). Processes of magma mixing between basaltic s.l. and rhyolitic melts

produced intermediate dacitic compositions Figure 18 - SiO2 vs. TiO2 and SiO2 vs. K2O for glasses in the (Montanini et al., 1994). mantle xenoliths borne in Plio-Pleistocene volcanic rocks of Sardinia. HKT = High K O-TiO glasses from the xenoliths of The peculiarity of the great majority of 2 2 Sardinian Plio-Pleistocene volcanic rocks (> Zeppara Manna (Giara di Gesturi; Lustrino et al., 1999); LKT = Low K2O-TiO2 glasses from the xenoliths of Zeppara Manna 99% of outcrops) is their “transitional” character (Giara di Gesturi; Lustrino et al., 1999); Pozzomaggiore glasses between typical within-plate anorogenic from Dostal and Capedri (1976). products (e.g., “bell-shaped” incompatible trace-element patterns in primitive mantle- normalized diagrams) and subduction-modifi ed et al., 1996). 87Sr/86Sr isotopic ratios of the less compositions (e.g., relatively low HFSE content and evolved volcanic rocks range from 0.7031 to 0.7054,

high LILE/HFSE ratios; Figs. 11 and 12; Di Battistini but most samples cluster near 0.7044 ± 2; εNd show almost exclusively negative values clustering close et al., 1990; Lustrino et al., 1996, 2000, 2002). to –5; only a few samples (Rio Girone basanite, Abundant mantle xenoliths (e.g., Dostal and Capedri, P55 to PW06 n° 6 - from Volume Guspini hawaiite and Capo ferrato trachyte) reach 1976; Albuquerque et al., 1977; Dupuy et al., 1987; more radiogenic values (up to +5; Cioni et al, 1982; Rutter, 1987; Beccaluva et al., 1989, 2001; Lustrino et Lustrino, 1999; Gasperini et al., 2000; Lustrino et al., al., 1999) are often associated with alkaline products 2000, 2002; Petteruti-Lieberknecht et al., 2003; Fig. at different stages of evolution (from basanite to 13). trachyphonolite), testifying to the rapid ascent of The great majority of the Plio-Pleistocene volcanic magma and the existence of magma chambers at rocks of Sardinia is characterized by the least- subcrustal depths (Di Battistini et al., 1990; Lustrino uranogenic Pb-isotopic composition of the entire

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra low, ifany, Nbanomaly;the(Ba/Nb) characterized byBa-andSr-positive anomalywith (DMM metasomatizedby“tonalitics.l.” melts)are heterogeneous source.Partial meltsofthisnew source of 2and98%,respectively, couldproducea of lower crust,mixed withDMMinproportions lithologies: ameltderived from12%partialmelting melts derived frompartialmeltingoflower crustal source (DepletedMORBMantle),metasomatizedby Lustrino etal.,2000)mightderive fromaDMM-like volcanic rocks(theUPV; UnradiogenicPb Volcanics; the majorityofPlio-PleistoceneSardinianmafi It hasbeenproposed(Lustrinoetal.,inprep.)that Sardinia (Fig.15). the genesisofPlio-Pleistocenevolcanic rocksof proposed anactive roleofcontinentallower crustin Lustrino (1999,2000a)andetal.(2000) (Lustrino andDallai,2004). geochemical similaritieswithEMI-typebasalts Pleistocene volcanic rocksofSardiniasharemany (Lustrino etal.,2000). Worth notingisthatthePlio- Hercynian) modifi anomalies, hasbeenrelatedtoancient(Panafrican/ This peculiarity, coupledwithtraceelement 19.42). consumption ofwater-rich alteredoceaniccrust weakness zonesinthelithosphere,following the following continent-continent collision, and2) of thicknessthelithosphereduetocrustalstacking these processeswerefacilitated by:1)theincreasing affected bydelaminationanddetachment processes; Permian), theSardinianlithosphereprobablywas At theendofHercynian Orogeny (Carboniferous- Lustrino, 2000a). collisional stageoftheHercynian Orogeny (Fig. 16; of densemafi have possiblytaken placeviapost-collisionalsinking lithospheric mantlewithlower crustallithologiesmay represent sourcecontamination.Interactionofthe in thiscase,thelower crustsignatureisthoughtto (e.g., Baker etal.,1997),itshouldbenotedthat Masberg, 1998) andotherEM-Ibasaltsingeneral hypothesized forotherCEVProcks(e.g.,Jungand magmas duringtherisingtosurface hasbeen While aprocessoflower crustalcontaminationof calculated meltsis>1. circum-Mediterranean igneousprovince ( have relatively radiogenic basanite, Guspinihawaiite andCapoFerratotrachyte) data; Fig.14).Onlyavery few samples(RioGirone Lustrino etal.,2000,2002; Authors’ unpublished down to17.5;Lustrino,1999;Gasperinietal.,2000; c lower crustalkeel thickened duringthe cation oftheirmantlesources 206 Pb/ 204 Pb ratios(18.84to N ratiosofthese 206 Pb/ 204 Pb c of densityfrom~2.8upto3.8g/cm granulite/eclogite facies, withasubsequentincrease margin, thelowermost crustismetamorphosedinto materials alongacontinent-continentcollisional references therein).Intectonically-piledcrustal Moldanubian Oceans(seeLustrino,2000b,and before theclosureofRheicandMassifCentral- and Sr, coupledwith(Ba/Nb) Alà deiSardihawaiites show positive anomalyatBa Pleistocene Sardinianvolcanic rocks. The Concas- abundance iscloselysimilartothatoneofthePlio- Permian-Triassic age(~240Ma)whosetraceelement rocks. Traversa etal.(1997)reporthawaiitic dykes of abundances roughlysimilartotheOrosei-Dorgali Concas-Alà deiSardizone)show traceelement basic alkalinedykes fromnorth-eastSardinia(the to anorogenicigneousrocksofSardinia,some typical featureoflateHercynian post-collisional Notwithstanding thefact thathighBa/Nbisnota Wyllie, 1994;Rappand Watson, 1995). melting andgarnet same densityincreasewithamphibole to partiallymeltbydehydration,producingthe batches onamphiboliticlower crustforcesthesystem and/or garnet-granulite;2)thearrival ofhotbasaltic the totaldisappearenceofamphibole,toeclogite into garnet-bearingamphiboliteandeventually, with During thisprocess,amphiboliteismetamorphosed absent solidus,coincidingwiththegarnet-inline. amphibolite) starttomeltasthey passthevapor- continent collision,lower crustallithologies(i.e., 17): 1)duringtectonicpilingfollowing continent- result oftwo processes(seeLustrino,2001;Fig. into themantle. The densityincreasecanbethe mainly ofintermediate-to-uppercrust)andrecycled detached fromtheuppermostportion(madeup favored thesinkingofmafi et al.,1998; Tatsumi, 2000) This increaseindensity et al.,2003)obtainedonplagioclase,clinopyroxene currently inprogress.Preliminaryresults(Lustrino of Plio-Pleistocenevolcanic rocksofSardiniais An oxygenisotopicstudyonmineralseparates (Fig. 16). source forPlio-Pleistocenevolcanic rocksofSardinia stages ofthe Tyrrhenian Seaandcouldhave actedas mobilized alsomany Ma after, duringtheopening age modifi could representanexpression oftheHercynian- s.l.) crustal-derived partialmelts. Therefore, they DMM contaminatedbyafew percentsof(tonalitic be consideredaspartialmeltsofasourcemadeupby cation. Suchamantlecouldhave been ± pyroxene growth (Wolf and N >1. These products can c keel whichwas ± plagioclase 3 (e.g.,Gao 27-05-2004, 15:40:17 EUROPEAN SUBCONTINENTAL MANTLE AS REVEALED BY NEOGENE VOLCANIC ROCKS AND MANTLE XENOLITHS OF SARDINIA P69

Figure 19 - MgO vs. Al2O3 for whole rock xenoliths from Pozzomaggiore (Dupuy et al., 1987; Rutter, 1987; Beccaluva et al., 1989; 2001) and Giara di Gesturi (Lustrino et al., 1999).

18 and olivine separates (analyzed via laser fl uorination δ OSMOW values) fi nd a sort of similarity in the technique) limit their possible mantle sources. anomalous Sr-Nd-Pb ratios of the same volcanic Nine analyses on plagioclase separates from alkaline rocks (Gasperini et al., 2000; Lustrino et al., 18 (alkali basalt, mugearite and trachyte) and tholeiitic 2000, 2002). The high values of δ OSMOW of Plio- (basaltic andesite) lavas gave a relatively large range Quaternary Sardinian plagioclase, therefore, could 18 of δ OSMOW from 6.46 to 7.56‰ (average 6.95 ± be related to the presence of crustal material in their 0.36). Tholeiitic lavas show generally lower values mantle sources (Lustrino et al., 2003). (6.46-6.98‰; n = 4) compared to the alkaline ones (7.04-7.56‰; n = 5); no difference has been noted among plagioclase of alkali basalts and trachytes. The Lithospheric mantle of Sardinia Two clinopyroxenes from the tholeiitic basaltic as revealed by mantle xenoliths andesite of Capo Frasca (south-west Sardinia) are Ultramafi c inclusions are relatively common in Plio- 18 Pleistocene alkaline rocks (basanite, alkali basalt, characterized by relatively high δ OSMOW (6.74‰ ± 0.08). Two clinopyroxenes from Oligo-Miocene hawaiite) of Sardinia. These xenoliths span, in andesitic basalt of Marmilla (southern Sardinia) composition, from harzburgites/cpx-poor lherzolites P55 to PW06 n° 6 - from Volume 18 to lherzolite and rare wehrlites and pyroxenites show δ OSMOW = 7.02‰ ± 0.03, consistent with the results obtained by Downes et al. (2001) on (Rutter, 1987; Beccaluva et al., 1989, 2001; Lustrino et other clinopyroxene of Sardinian Oligo-Miocene al., 1999). The origin of the two latter types (wehrlites volcanic rocks. Liquidus olivine of Plio-Pleistocene and pyroxenites) has been related to cumulus volcanic rocks from Orosei-Dorgali and Planargia are processes, whereas the fi rst two types (harzburgites 18 to lherzolites) have been interpreted as upper mantle characterized by δ OSMOW = 5.55‰ ± 0.25. These preliminary results (the anomalously high residues variably affected by metasomatic processes.

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra anhydrous four-phase assemblageiassociatedwiththe Giara diGesturiandOrosei-Dorgali outcrops)isthe Only inrarecases(<1%ofstudiedxenoliths fromthe and, morerarely, plagioclase. olivine andtiny quenchmicrolitesofclinopyroxene including clinopyroxene andspinelrelicts,skeletal melt pockets. The latteraremadeupbyaglassymatrix 2) al., 1989). unstrained olivine andorthopyroxene (Beccaluva et of strainedclinopyroxene andspinel,aswell in afi rarely, orthopyroxene) grains(2-5mminsize)set 2) smaller clinopyroxene andspinel(~1mm). lamellae ofclinopyroxene) upto8mminsize,with orthopyroxene (thelatteroftenwithexolution 1) Three arethemostcommontextures observed: pyroxenites andgabbroicnodules. (Rutter, 1987;Beccaluva etal.,1989),togetherwith of incipientpartialmelting(marginal sieve texture) to 4cmlong),usuallycorrodedandwithevidence often associatedwithblackaugitemegacrysts (up Especially intheLogudoroarea,xenoliths are 1989, 2001;Lustrinoetal.,1999). (Dupuy etal.,1987;Rutter, 1987;Beccaluva etal., (cpx-rich lherzolite)torelatively depletedharzburgite values closetomodelfertilelherzolite(Niu,1997) facies, andthewhole-rockcompositionvaries from The xenoliths show exclusively aspinelequilibration et al.,1989,2001). (e.g., Pozzomaggiore;Dupuyetal.,1987;Beccaluva 1999; Lustrinoetal.,1999)toabout20cmindiameter centimeters (e.g.,RioGironeandGuspini;Lustrino, The overall sizeofthexenoliths rangesfromafew different localities. well asintexture have beenreportedamongthe differences inmodalandchemicalcomposition,as western Sardinia;Lustrino,1999).Nosystematic Sardinia; Lustrinoetal.,1999)andGuspini(central- small occurrencesareatRioGirone(south-eastern central-southern Sardinia;Lustrinoetal.,1999).Other Beccaluva etal.,1989)andGiaradiGesturi(Gerrei, al., 1989,2001),Mt. Arci (central-southernSardinia; Montiferro (central-westernSardinia;Beccaluva et 1970; Beccaluva etal.,1989,2001;Lustrino,1999), Dorgali area(central-easternSardinia;Brotzuetal., Beccaluva etal.,1989;Lustrino,1999),Orosei- et al.,1977;Dupuy1987;Rutter, 1987; Sardinia; DostalandCapedri,1976; Albuquerque are: PozzomaggioreandLogudoroarea(northern The typicalmantlexenoliths localitiesinSardinia Pyrometamorphic Porphyroclastic Protogranular ne-grained recrystallizedmatrix(<2mm) , withgrainsofolivine and , withlarge olivine (and,more with spongyclinopyroxene and Olivine cm inwidth,sometimescross-cutthexenoliths. common. GreenCr-diopside veins, ofabout0.5to1 oxidation rimsaroundthexenoliths arerelatively has beenobserved (Lustrinoetal.,1999).Reddish crystallization nearthecoolersurface ofthexenolith) zoned titaniferousclinopyroxene (probablydueto the RioGironexenoliths, growth ofhourglass- shape ofthexenolith. Sometimes,particularlyin fi undersaturated hostlava anddeveloping arimof enstatite grains(mostlikely reactingwiththesilica- generally sharp,but in somecasesresorptionof The contactsbetweenxenoliths andhostlava are 2001). et al.,1999)andOrosei-Dorgali (Beccaluva etal., Beccaluva etal.,1989),GiaradiGesturi(Lustrino Pozzomaggiore (Logudoro; Albuquerque etal.,1977; glass poolsunrelatedtohostlava arereportedfrom et al.,1999;Beccaluva etal.,2001).Interstitial presence ofhydrousphaseslike phlogopite(Lustrino forsterite content(Fo kink banding. At thecontactwithhostlava, the exhibits curved boundaries,aswellas, sometimes, (0.01-0.24 wt%).Olivine ismostlycoarseandoften wt%) andlow CaO(0.02-0.16wt%)andMnO composition (Fo euhedral andfortheirhigherforsterite(Fo olivine) differ fromprimaryolivine intheirbeing olivine includedinpyrometamorphic glass(secondary similar totheuncorrodedolivine. The crystallitesof in glass(Lustrinoetal.,1999),arecompositionally exchange. Rarerelictsofolivine, partiallyenclosed olivine inthegroundmass,suggestingMg/Fereaction relict phaseinthemeltpockets. Enstatiteisalways glass, andonlyvery rarely asapartiallycorroded found asaquenchphaseinthepyrometamorphic Cr# rangingfrom22.6to4.5.Orthopyroxene isnever values ofcoexisting primaryolivine, withvariable range inMg#isnarrow (91.6-89.5),overlapping the showing exsolution lamellaeofclinopyroxene. The Orthopyroxene banding. size; 3)anhedralshape;4)commonpresenceofkink 1) higherFo content(~91versus ~ 80); 2)larger distinguished fromliquidusolivine onthebasisof: commonly foundinhostlavas andcanbeeasily nucleated. Disruptedmantleolivine grainsarevery depth ofequilibrationwherethesemicrolitespossibly 1997). The higherCaO couldberelatedtoashallower related olivine (e.g.,Girodetal.,1981; Yaxley etal., wt%), asgenerallyreportedforworldwide glass- CaO (0.1.-0.30wt%)andlower FeO(6.71-8.61 ne-grained roundedolivine) producedanirregular : Primaryolivine hasaquiteconstant : Orthopyroxene isenstatite,often 91.5-89.3 80-74 ), withhighNiO(0.26-0.66 ) overlaps withthevalues of 93-91 27-05-2004, 15:40:21 ) and EUROPEAN SUBCONTINENTAL MANTLE AS REVEALED BY NEOGENE VOLCANIC ROCKS AND MANTLE XENOLITHS OF SARDINIA P69

(Table 3) = EMP analyses of glasses in the mantle in reaction with SiO2-undersaturated host lava. The result of this reaction process is: orthopyroxene + xenoliths from Giara di Gesturi (Lustrino et al., 1999; L 99) and Pozzomaggiore SiO2-undersaturated melt = olivine ± clinopyroxene ± spinel ± glass (e.g., Arai and Abe, 1995). If (Dostal and Capedri, 1976; DC 76). orthopyroxene is Cr-rich (enstatite in harzburgite), in pyrometamorphic glass; 5) exsolved lamellae P55 to PW06 n° 6 - from Volume its instability produces typical podiform chromitite in larger orthopyroxene. Spongy-textured and zones. relict clinopyroxene have been interpreted as Clinopyroxene: Clinopyroxene can be found as: incipient partial melting of the xenoliths, probably a 1) small interstitial grains between larger olivine consequence of the thermal shock after incorporation and orthopyroxene; 2) clouded by opaque grains into host lava and the pressure release en route to the and minute green spinel inclusions; 3) spongy- surface (e.g., Albuquerque et al., 1977; Lustrino et al., textured crystals; 4) relict and quenched microlite 1999). Clinopyroxene straddles the fi eld of diopside

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra Cr 0.32 wt%)and Al al., 2001). The in glassalsoshows higher TiO glasses show higherMg#upto93.3;clinopyroxene observed. As notedforolivine, euhedralmicrolitesin variations (92.8-88.2and20.6-3.7,respectively) were olivine andorthopyroxene, widerMg#andCr# (2000), whereasthehigh- volcanic rocksofSardiniadefi plot closetotheRPVfi are confi 0.70263 to0.70455;clinopyroxene fromharzburgite separates ofCr-diopside fromlherzoliterange lower Na 1987). Spinelrangesfromchromiferous(Cr Fe-rich blackoxiderim,upto0.5mmthick(Rutter, host lava, Cr-rich spineltendstoreactformamore phase andeuhedralcrystallite.Incontactwiththe with hostlava; 5)associatedwithglassbothasrelict intergrowths withorthopyroxene, mostlyatcontact between olivine grains;4)invermicular symplectitic spongy clinopyroxene; 3)smallroundgrainswithinor pyroxene crystals; 2) smallocthaedraassociatedwith (often intriplepointjunctions)orincluded leaf orvermicular crystalhabitatgrainboundaries black toreddishbrown grains(upto4mm)withholly variations even in thesamexenolith. Itoccursas:1) and harzburgite [(La/Yb) (Wo and endiopside,withonlyasmallvariation inFeO diopside veins haslow CaOandthehighestNa enriched incpx-poorlherzolite[(La/Yb) Lustrino etal.,unpublisheddata). Also from 0.70418to0.70431;Beccaluva etal.,2001; cpx-rich lherzolite[(La/Yb) Clinopyroxene REEpatternsrangefromnearlyfl are lessenriched(2-3timeschondrite;Rutter, 1987). ranges from3to7timeschondrite,whereasHREE compared toLREEandHREE;abundance are spoon-like, withadepletionofMREE(Eu,Gd) Chondrite-normalized REEpatternsofCr-diopside clinopyroxenes plotclosetotheUPVfi data). Low- Beccaluva etal.,2001;Lustrinounpublished clinopyroxene fromharzburgite (0.51259to0.51252; ratios aremuchmoreuniformandlessradiogenicfor from lherzolite(0.51323to0.51253)whereasthese show arelatively widerangeforclinopyroxene 2001). The spongypyroxene shows low TiO Spinel Lustrino etal.(2000). Pleistocene volcanic rocksofSardiniadefi 2 O 42-49 3 (1.15-1.34wt%).Clinopyroxene fromtheCr- : Spinelshows widetextural andchemical En ned tothemoreradiogenicend( 2 O (down to0.3wt%;Beccaluva etal., 87 43-53 Sr/ Fs 86 87 Sr, high- Sr/ 2 4-8 O 86 3 ). Comparedtothecoexisting (2.9-3.8wt%),andthehighest Sr isotopicratiosmeasuredon 143 N 87 =~7-18](Beccaluva et eld ofPlio-Pleistocene N Nd/ Sr/ =~0.25-10]toLREE- ned byLustrinoetal. 86 144 Sr, low- 2 Nd clinopyroxenes (0.3-2wt%)and N eld ofPlio- =~4.5-5.0] 143 143 Nd/ Nd/ 2 nd by ned 87 O 2 (0.26- Sr/ 3 144 144 45.5 at in 86 2 Nd Nd O. Sr wt%; Al wt%, high Al Glass the garnet-peridotitemicafromkimberlites. glasses show SiO norm; DostalandCapedri,1976) The GiaradiGesturi leucite normative (2.5-3.7ne-norm;0.09-0.14lc- glass compositionsofPozzomaggiorearenepheline- corundum-normative (Lustrinoetal.,1999). The normative feldspars,andtwo ofthemarealso Gesturi isquartz-normative with47.8to71.1CIPW The glassinthemantlexenoliths fromGiaradi (Lustrino, 1999;Beccaluva etal.,2001). 3%) areassociatedwithsmallinterstitialglassyblebs plagioclase microlites(Anupto77%,Orlower than feldspar (Anlower than5%,Orupto57%)and 1977; Lustrinoetal.,1999).Insomecases,alkali with clinopyroxene andspinel(Albuquerque etal., glass unrelatedtothehostbasaltisalways associated and spinel(Lustrinoetal.,1999). Worth notingisthat with euhedralmicrolitesofolivine, clinopyroxene contain clinopyroxene andspinelrelicts,together In thelattercaseitmaybedevoid ofcrystalsormay pods andinmeltpockets (pyrometamorphic glass). mostly ascrosscuttingveinlets and/orasinterstitial lava, theglassinmantlexenoliths ofSardiniaoccurs 1989) alongthecontactbetweenxenolith andhost 13.6 wt%),variable TiO TiO from sp-bearingmantle,beingcharacterizedbyhigher phases. The composition falls inthefi suggesting possibleequilibriumwiththeothersilicate roughly similartocoexisting olivine andpyroxenes, (Lustrino etal.,1999). Their Mg#(89.5-88.3)are and olivine andasveinlets cuttingorthopyroxene grains (~1mm)alongthecontactwithorthopyroxene having equilibrium grainboundaries,and2)anhedral (0.5 mmlong)inlarger orthopyroxene crystals phlogopite occur:1)euhedraldeformedstringers pyrometamorphic glass. Texturally, two typesof Manna xenoliths. Itwas never foundclosetothe orthopyroxene andolivine insomeZeppara wt%; Lustrinoetal.,1999)occursinorbetween (Cr Phlogopite be analyzed. in thespongyclinopyroxene relictaretoosmallto (spinel). Both“moltenphase”andspinelocthaedra clinopyroxene intoCr-poor liquidandCr-rich phase phase, subsequenttotheincongruentmeltingof clinopyroxene areinterpretedasanewly formed to 82.4.Spinelocthaedraassociatedwithspongy ranges from9.3to62.4,whileMg#vary from63.2 2 2 O and Al : excluding “jacket glass”(e.g.,Edgaretal., 3 11.1wt%; Al 2 O : High-Ti phlogopite(TiO 3 2 18.8wt%),FeO-rich,toaluminous O 3 2 aswellbylower SiO O 3 2 (18.0-23.1wt%)andCaO(5.9- rangingfrom51.55wt%to58.75 2 O 3 54.9wt%),MgO-rich.Cr# 2 (0.76-3.72wt%),alkalies eld ofphlogopite 2 comparedto 2 3.22-4.72 27-05-2004, 15:40:29

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(0.94-7.25 wt %), and extremely variable Na2O/K2O. the peridotitic assemblage, which variably reacted Glasses from the Pozzomaggiore xenoliths have with the preexisting phases, or 2) in situ partial

generally lower SiO2 (48.13-52.38 wt%), Al2O3 (2.95- melting of peridotitic phases due to decompression

8.30 wt%), FeO (2.54-2.90 wt%) and Na2O (0.57-0.77 after incorporation within the host lava. In the fi rst wt%), coupled with higher MgO (14.02-16.08 wt%) case the glass formation may have predated, or and CaO (22.22-23.60 wt%) than the glasses from been coeval with, magmatic activity, while, in the Giara di Gesturi. The most striking aspect of the latter second case, it is necessarily contemporaneous with

glasses is their bimodal distribution of K2O and TiO2. magmatic activity. Indeed, glasses can be divided into (Lustrino et al., Both LKT- and HKT-type glasses show fractional

1999): (a) low K2O-TiO2 (LKT) type [average K2O crystallization-type paths in Harker-type diagrams,

and TiO2 = 0.07 wt% and 0.68 wt%, respectively, considered by Lustrino et al. (1999) evidence CaO (av. 11.36 wt%), MgO (av. 4.88 wt%) and FeO of crystallization of the microlites (olivine ±

( av. 5.06 wt%)], and (b) high K2O-TiO2 (HKT) type clinopyroxene ± spinel) from a parental melt. [average K2O and TiO2 = 2.51 wt% and 3.14 wt%, The presence of spongy pyroxene, glassy blebs almost respectively, CaO (av. 7.91 wt%), MgO (av. 3.00 exclusively associated with diopside and spinel, and

wt%) and FeO (3.71 wt%)] (Tab. 3; Fig. 18). the high CaO and Al2O3 and low Na2O and K2O of (Table 3) the LKT glasses, have all been considered evidence of non-modal partial melting of peridotite (Lustrino The LKT glasses show a subalkaline character and et al., 1999), with diopside and spinel being the fi rst basaltic-andesite-to-andesite composition, whereas phases to be consumed, as evidenced by several the HKT group is more alkali-rich and straddle the experiments (e.g., Baker and Stolper, 1994). fi eld of mugearite and trachyandesite. These observations agree with the experiments performed by Doukhan et al. (1993) and Raterron In terms of Mg# (assuming a Fe2O3/FeO ratio = 0.15) these glasses range from a primitive liquid et al. (1997) on early partial melting (EPM) in composition (Mg# = 71.1) to relatively evolved pyroxenes. types (Mg# = 41.9), with the LKT glasses having Incongruent melting of diopside and spinel cannot generally higher Mg# than the HKT ones. Mg# of explain the high K2O (up to 4.6 wt%) and TiO2 (up to Pozzomaggiore glasses are very high (90.1-92.3). 3.7 wt%) of HKT glasses, nor the high TiO2 both of The existence of glasses with approximately the the enclosed diopside and spinel (up to 5.32 and 0.8 same chemical composition as plagioclase has been wt%, respectively). The high TiO2-K2O phlogopite related to the incipient partial melting of the xenolith is likely to be involved in the genesis at least of the at pressure-temperature conditions overlapping those HKT glasses. of the fi eld of stability of plagioclase-lherzolite In conclusion, the presence of glassy patches in the (5-10 kbar; < 1000 °C; Albuquerque et al., 1977). Giara di Gesturi xenoliths is not consistent with On the other hand, glass patches with compositions metasomatic processes, but only with thermo-baric approaching that of clinopyroxene seem to confi rm disequilibrium of the phases. On the other hand, the the hypothesis that this phase was affected by presence of phlogopite laths requires processes which melting processes together with spinel, as originally metasomatized the Sardinian subcontinental mantle. hypothesized by Dostal and Capedri (1976) and The relatively high SiO2 of the glasses (higher than Albuquerque et al. (1977). The high Ti content of SiO2 of diopside) was related to the incongruent some glasses has been alternatively related to the melting of clinopyroxene and spinel, with involvement in the melting processes of a Ti-rich crystallization of a virtually SiO2-free phase (new phase like rutile (Albuquerque et al., 1977) or spinel) according to the reaction cpx + sp ± phl ⇒ ol phlogopite (Lustrino et al., 1999). + sp + cpx + glass (Lustrino et al., 1999). Dupuy et al. (1987) proposed for the glass in the Whole rock composition: More that 75 % of P55 to PW06 n° 6 - from Volume mantle xenoliths from Pozzomaggiore an origin by inclusions in Plio-Pleistocene alkaline volcanic rocks the breakdown of amphibole during the ascent of the of Sardinia are harzburgite-lherzolite, therefore these xenoliths, even if this phase has never been found in compositions have the greatest relevance. On the Sardinian mantle xenoliths. basis of their mineralogy, modal proportions, mineral Basically, the glasses in mantle xenoliths may have compositions, textures and chemical compositions, derived from: 1) infi ltration of material, external to the Sardinian xenoliths belong to Frey and Prinz’s (1978) group I (or Cr-diopside series). The Mg# of

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra REE and(Tb/Yb) like patterns,withrelative depletioninthemiddle is negatively correlatedwithSiO and alkalies).MgOrangesfrom37.4to47.7wt% to-strongly depletedinbasaltcomponents(Ti, Al, Ca, and McDonough(1989),thesexenoliths areslightly- Compared totheprimitive mantleestimatebySun 0.15) rangefrom88.3to92.8). Megacrysts Beccaluva etal.,2001). 0.70460 and0.51256-0.51252,respectively; only foronesample)thanharzburgites (0.70385- TiO the xenoliths (calculatedassumingaFe [(La/Yb) with ageneralenrichmentinLREErelative toHREE Beccaluva etal.,2001)displayslarge variations, REE wholerockcontent(Dupuyetal.,1987; (Table 4) characterized bylower clinopyroxene isotopicdata:lherzolitesaregenerally Whole rockisotopiccompositionmimicsthe agents REE-andincompatibleelements-rich. harzburgite; 2)interactionwithmetasomatizing from theperidotiticmatrix,withformationof partial meltingandextraction ofbasalticcomponents two-stage process:1)depletionbyvarying degrees of mantle xenoliths (e.g.,Downes, 1990)isevidence ofa aspect, relatively commoninmany otherworldwide (Montiferro harzburgites; Beccaluva etal.,2001). This highest of clinopyroxene tolower absoluteabundance. The al., 1999;Beccaluva etal.,2001)(Tab. 4;Fig.19). CaO (0.54-3.62wt%)(Dupuyetal.,1987;Lustrino unpublished data). mesostructures (Beccaluva etal.,1989; Authors’ melting andexsolution lamellaewithperthite-like pressure disequilibriumismirroredbyincipient (e.g., IrvingandFrey, 1984;,1999). Lower- pressure (~9-15kbar)andtemperatureofformation relatively high Al andNacontentindicatesahigh of mantlexenoliths (diopsidetoendiopside). Their clinopyroxene (mostlytitaniferoussalite)andthat composition different fromthatofthehostlava These megacrysts are Al-augites, withachemical studied byRutter(1987)andBeccaluva etal.(1989). and higher 2 (0.02-0.15wt%), Al Σ N REE isfoundinthemostdepletedxenoliths ratio~4-18].Somesamplesdisplayspoon- : Clinopyroxene megacrysts have been 143 Nd/ 144 N <1thatmimictheREEcontent Nd (0.51302;analysesavailable 87 Sr/ 2 O 3 86 (0.34-4.12wt%)and Sr (0.70308-0.70423) 2 (42.5-46.5wt%), 3+ /Fe 2+ ratio= a strongLigurianaccent). as wellinitssounds(theinhabitantsstillspeakwith Ligurian specialitiesaspanisse,farinate andburidde) from the Tunisian cuscus,sidebywithsuch sovereign) andinitsfl colours ofthehousesinCarloforte(namedafter tastes andcharacteristicswhichcanstillbeseeninthe century. That iswhySanPietrohasLigurianand Arab had beenforcedtosettlein Tunisia duringtheXVI it uponthedescendantsofLigurianfamilies that 1736. CharlesEmmanuelIIIofSavoy thenbestowed This islandremaineduninhabitedforcenturiesuntil . Itsrecenthistoryisjustasrichandunique. once landedonitsshoresduringhisjourney to from alegend whichnarrateshow theapostlePeter “Accipitrum Insula”.Itspresentnameisderived the Greeks“Hioera”or“Nesos”;Romans many names:thePhoenicianscalledit“Inosim”, The islandhasavery longhistoryandhashad Its coastlineisaseriesofraggedandsandyareas. of Sardiniaandishalfanhouraway fromSulcis. San PietroIslandissituatedatthesouth-easterntip the fi on SanPietroIsland.Duringdinner, presentationof Sardinia), about100kmwestofCagliari.Nightspent Go ontoCarloforte(SanPietroIsland,south-west about 1.5hoursoffl Departure fromRomeandarrival atCagliariafter Field TripItinerary General overview ofmany lithologiesandoutcrops. Trip aroundSanPietroIslandwitharented boat. h. 10.30-14.00 Stop 2.2a: geodynamic implicationsofthistypemagmatism. the originofperalkalinemagmasandpossible Well-evident are bigcolumnarjoints.Discussionon locality ofcomendites(mildlyperalkalinerhyolites). Stop isatasitecalledCommenda,whichthetype Open quarryofcomenditiclavas atkm7.4. This h. 9.15-9.45.(N39°08’46’’; E8°15’45’’) Stop 2.1: Departure fromCarloforteath.9.00 volcanic rocks) (Miocene metaluminoustoperalkalinefelsic eld tripitineraryandanice-breaker party.

ying. DAY 1 DAY 2 avours (suchascascà,derived

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Stop 2.2b: DAY 3 (in case of bad weather) - h. 10.00-11.00 (Plio-Pleistocene volcanic rocks and mantle (N39°09’23’’; E8°13’44’’) at km 11.0. xenoliths) Stratifi ed comenditic lava fl ows of Cala Fico with Departure from Iglesias at h. 9.00. columnar joints. Visit to the LIPU (Italian League for the Protection of Birds) oasis. Stop 3.1: h. 10.00-10.30 (N39°32’22’’; E8°38’09’’) Stop 2.2c: Visit to the Guspini neck (hawaiite) with spectacular (in case of bad weather) - h. 11.15-11.45 columnar jointing. Capo Sandalo with a swim and box lunch. (Stops 2.2b and 2.2c are alternatives to Stop 2.2a). Stop 3.2: h. 11.00-12.00 (N39°43’15’’; E8°43’53’’) Stop 2.3: Abandoned obsidian quarry (rhyolites of Mt. Arci) h. 15.30-15.45 (N39°11’20’’; E8°25’20’’). in between the towns of Uras and Siris/. Basal contact of comenditic rhyolites on the road to Short walk (10-15 minutes). Portovesme (Nuraxi or Conca-is-Angius); possibility of seeing the retinitic level of the ignimbrite. Stop 3.3: h. 12.30-12.45 (N39°41’45’’; E8°48’27’’) Stop 2.4: On the road between and . 16.10-17.30 (N39°10’52’’; E8°29’21’’) Spectacular example of a cooling structure in basalt. Locality: Mt. Sirai. Overview of San Pietro and Sant’Antioco Islands and of the Sulcis area from the top of the Seruci ignimbrite. Discussion on Stop 3.4: peralkaline magmatism. Visit to the Archaeological h. 13.30-15.30 Museum at Villa Sulcis of Carbonia. Arrival at the village of near the tholeiitic The museum, situated in a park which also includes plateau of Giara di Gesturi (central Sardinia). botanical gardens, houses archaeological material Box lunch. Guided visit to the Nuragic dating back to 6,000 BC, which documents the pre- Complex. nuraghic, nuraghic, and Phoenicio-Punic periods, up Around 1500 BC, a group of settlers arrived in to the Roman and post-classical ages. On display are a Sardinia from a still-unknown place and spread number of grave furnishings from the Phoenician and rapidly throughout the island, taking with them Punic necropoli on Mt. Sirai; the reconstruction of a advanced building techniques, beautiful Hellenistic “trophet”, a cemetery-sanctuary devoted to children, pottery and what appears to be a fairly well-developed with cinerary urns and original carved steles. The religion. Obsessed, as Sardinians have always museum also offers visitors a “touchscreen” system been, with protecting themselves from invasion, for a virtual tour of Mount Sirai, the famous Punic the Nuragic people built roughly 30,000 circular archaeological site, founded around 720 BC by the fortifi ed dwellings, strategically located so that each Phoenicians and conquered in the 6th century by the could easily see its neighbor. Today, 7000 of these Carthaginians. Stay the night at Iglesias. megalithic structures survive, and they are unlike any Iglesias is a little town in south-west Sardinia. It is a other ruins in the world. The most important complex town full of art, traditions and hospitality; the mines is Su Nuraxi, in Barumini, centered around are the most important testimony of a glorious and a three-story tower built 3500 years ago. This site was rich history. The city centre is magical: you feel like recently added to UNESCO’s World Heritage List. you’re living in the , so walk and see the The complex consists of circular defensive towers Volume n° 6 - from P55 to PW06 n° 6 - from Volume castle, the Cathedral, the walls, but also look up at in the form of truncated cones built of dressed stone, the balconies, the windows and the people. For more with corbel-vaulted internal chambers. Extended and than three thousand years this land has given life strengthened in the fi rst half of the 1st millennium and prosperity to its inhabitants through its mining under Carthaginian pressure, it is the fi nest and activities. most complete example of this remarkable form of prehistoric architecture. According to others these ruins represent palaces or temples around which

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra code/archeologia/LINGUA/EN). www.sardi.it/indexuk.htm; http://www.sardegna.com/ huts. (moreinformationcanbefoundat:http:// the fortresswas thevillage,madeupofcircular to theMiddleBronze Age (~1450b.C.). Around superimposed rooms(originally3)goingbackagain diameter atthebaseof10meters;itconsiststwo meters high(originallyitwas over 18meters),witha and two entrances. The centraltower iscurrently14 rectilinear raisedembankmentsconnectingthem, barbican whichhas7towers, withjustasmany 4 towers. This bastioniswithinalarge hexagonal has acentraltower surroundedbyabastionwith 230 metersabove thesurroundingland. This nuraghe a “polilobato”nuraghe,placedonplateausituated or lessfromaround3500yearsago.“SuNuraxi”is age isnotwellconstrained,but they shouldbemore stone (oftenPlio-Pleistocenetholeiiticbasalt). Their werebuilt with superimposedblocksof were villages,primarilymadeupofhuts. The h. 9.15-9.45 Stop 4.1: Departure fromBosaMarinaath.9.00 rocks andmantle xenoliths) (Oligo-Miocene ignimbrites,Pliocenealkaline civil andmilitaryarchitecture. streets andsquaresisafascinating example of of Serravalle, built in1112,overlooks itsorderly is ofancientCarthaginianorigin. The medieval castle River; itistheonlyriverside town inSardinia,andit monuments. Bosaissituatedatthemouthof Temo and historicaldowntown, richinchurchesand its splendidpastthroughoutthemainstreets capitals ofSardiniaandstillpreserves signsof A smallmarinetown, Bosaisoneoftheancient Bosa Marina(north-westSardinia). and clinopyroxene megacrysts. Spendingthenightat alkaline sodiclavas withabundant mantlexenoliths Pozzomaggiore (Logudoro,northernSardinia) h. 17.30-18.00(N40°23’21’’; E8°40’49’’) Stop 3.5: with abundant mantlexenoliths). Observation of Visit toanabandoned quarryofMontiferro(hawaiite h. 11.30-12.15(N40°13’22’’; E8°36’33’’) Stop 4.2: north-western SardiniauptoCapoMarangiu. Visit tothegiant ignimbriticdepositsofBosaand

DAY 4

Stop 4.5 domes andbasaniticlavas. Moving towards thetown ofCuglieri,visitphonolitic Stop 4.4 an abandonedquarryofphonolite. Montiferro igneouscomplex atBaddeUrbara. Visit to Staying thenightatBosaMarina. and gabbroicnodules. Teprera (Montiferro)withabundant mantlexenoliths northern Sardiniawithspectacularcolumnarjoints. Basaltic lava fl h. 13.30-14.30(N40°19’54’’; E9’33’07’’) Stop 5.2: mantle xenoliths. Exploited spatterconeofIttireddu(Logudoro)with h. 10.30-11.30(N40°32’41’’; E8°54’31’’) Stop 5.: Departure fromBosaMarinaath.9.00 xenoliths) (Plio-Pleistocene volcanic rocks andmantle Stop 4.3 sandstone. Boxlunchatthetown ofSanLeonardo. the contactbetweenPliocenelava andMiocene Gulf ofthe Angels. Itisregarded bymany asoneof has morethan6milesoffi Poetto Beach,locatedontheoutskirtsofCagliari, in andaroundCagliari.Herearesomeofthem: are various interestingtouristsightsand attractions architecture andamarvelous beachnearby. There “City oftheSun”,withsomeinterestingmedieval aesthetically pleasingcity, oftenreferredtoasthe is locatedonthesouthernendofisland.Itan city foundedbytheancientPhoenicians. The city Cagliari, thecapitalcityofSardinia,isavery old trip. Arrival atCagliariafterabout3-4hours.Endofthe (SuGologone,centralSardinia). in theafternoonforswimming.Stayingnightat with columnarjointsandmantlexenoliths. Freetime district, north-easternSardinia).Basalticlava fl Box lunchatCalaGonone(Orosei-Dorgali igneous h. 15.00-16.00(N40°17’’12’’; E9°38’29’’) Stop 5.3: Departure fromOlienaat9.00. -h.16.00-17.00 Abandoned quarryofPunta -h.15.00-15.30(N40°12’06’’; E8°35’28’’) -h.14.15-14.45(N40°09’30’’; E8°37’48’’) ows neartheCedrinoRiver in central- DAY 5 DAY 6 ne whitesandfacing the

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the world’s top beaches. Lined with kiosks and cafés, Sardinia probably came from the Italian mainland the beach attracts sun worshippers by day, and serves and, in particular, from Etruria. Those who populated as a vibrant meeting place for young people at night. the central region of the island around the salt lakes Archaeological Sights/Medieval Architecture. A 2nd of Cabras and S. Giusta, arrived, it seems, from the century Roman amphitheater and the 13th-century Iberian Peninsula by way of the . Cathedral of Santa Cecilia are here. Cagliari also Those who founded their settlements around the gulf hosts Sardinia’s National Archaeological Museum. of Cagliari were never one single people, but actually San Michele, an impressive medieval castle perched several peoples. on top of a hill, enables you take in a magnifi cent view As time passed, the Sardinian peoples became of the city in its entirety. The Marina and Stampace united in their language and customs, yet remained areas of the city - two of the four quarters into which politically divided into various smaller tribal states. the town was divided in the Middle Ages - have Sometimes they banded together, while other times some wonderful examples of medieval architecture, they were at war with one another. Tribes lived in including several churches. Also, there are extensive villages made up of thatched, round, stone huts, ruins of the ancient Phoenician city of Nora just similar to the present day “pinnate” of shepherds. outside Cagliari. From about 1500 B.C. onwards the villages were built at the foot of mighty truncated-cone fortresses (often General information on Sardinia reinforced and enlarged with battlement towers) Though it has been inhabited since prehistory (the fi rst called “nuraghi”. human settlements date back to 6.000 - 5.000 B.C.), The boundaries of tribal territories were guarded by Sardinia never developed a unifi ed population. Traces smaller, lookout nuraghi erected on strategic hills of settlement are therefore extremely fragmentary, as commanding a view of the enemy. Today some 7000 lots of little villages throughout the island even today nuraghi dot the Sardinian landscape. attest. Villages, which are an expression of the civil-social Ancient history order, were organized into communities and according Around 1000 B.C. the Phoenicians began to land to tribal groups of modest size. on the shores of Sardinia with increasing frequency. The age of the was a period of Setting sail from Lebanon, on their trade routes as far independence, but also of relative isolation from afi eld as Britain they needed safe anchorages for the the larger cultural movements in the Mediterranean night or to weather a storm. area. The Nuraghi, with their peculiar architectural With the local chieftain’s consent the more common structure, are the most representative sign of that ports of call were those later named as: Caralis, Nora, past. Bithia, Sulcis, Tharros, Bosa, Torres and . They A typical trait of Sardinian archaeology is the lay out soon became important markets, and after a while of the monuments and architectural works: they are real towns were established, inhabited by Phoenician spread out all over the countryside, in harmony with families who traded on the open sea and with the the natural environment. Nuragic Sardinians inland. The Nuraghi, as well as other evidence from the past, In 509 B.C., in view of the Phoenician expansion such as Domus de Janas, holy wells and temples, inland becoming ever more menacing and penetrating, the giants’ tombs, the big stones fi xed in the ground the native Sardinians attacked the coastal cities held (betili or megalithic menhirs) make Sardinia a kind of by the enemy who, in order to defend themselves, “open-air museum”. called upon for help. These signs are very frequent. On the whole island The Carthaginians, after a number of military there are, in fact, about 7000 Nuraghi and hundreds of campaigns, overcame the Sardinians and conquered archaeological monuments. the most mountainous region, later referred to as P55 to PW06 n° 6 - from Volume Barbarian or Barbagia. Prehistory For 271 years, the splendid Carthaginian or Punic Sardinia is one of the most ancient lands in Europe, civilization fl ourished alongside the fascinating local visited way back from the Palaeolithic period, though Nuragic culture. inhabited permanently by man only much later, in the In 238 B.C. the Carthaginians, defeated by the Neolithic age, around 6000 B.C. Romans in the fi rst Punic War, surrendered Sardinia, The fi rst men to settle in and Northern which then became a . The Romans

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra representatives ofthepeoplegatheredinassembly “judice”) himselftodecidebut wereamatterforthe issues ofnationalinterestwerenotfortheking(or same timedemocratic,sinceallthemostimportant the propertyofmonarch.Butthey wereatthe not patrimonial,but independentsinceitwas not “judicative”, constitutedasovereign kingdom, Each oneofthesefourSardinianstates,called “king”) oftheirown “logo”orstate. becoming “judices”(inSardinian“judikes” means the lieutenantsgainedtheirindependence,inturn or Logudoro, andGallura. Around 900, his fourlieutenantsinthemeréieofCagliari, Torres the island,assignedhiscivil andmilitarypowers to magistrate, inordertoprovide abetterdefenceof one bythecoastaltowns andcities. The provincial more ruinouswithtime. Their inhabitantsabandoned on theSardinianshoresbegan in710andgrew ever The continualraidsandattacksbytheIslamicBerbers and militarypowers. magistrate assumedoverall command,with bothcivil was forcedtodefendherself;thus,theprovincial occupation ofSicily. Sardinia remainedisolatedand andpartofFrance.In827they began their From 640to732the Arabs occupiedNorth Africa, religious traditions;oneofitskingswas Ospitone. established itself,withSardinian–heathen,lay, and sixth century, ashort-lived independentdomainre- the Barbagiaregions. Here,towards theendof Christianity spreadthroughouttheisland,except in the Easternmonastivism ofthefollowers ofSt.Basil, command ofa“dux”. Along withtheByzantinesand in Forum Traiani (nowadays Fordongeanus) underthe Caralis (Cagliari)andcontrolledbyanarmystationed called “merèie”,governed byamagistrateresidingin Byzantine. The islandwas divided intodistricts Eastern EmperorJustinian,andSardiniathusbecame place some30kmfromCarthage-bythetroopsof In 534the Vandals were defeatedat Tricamari -a with othercoastalcitiesofSardinia. on Latiumthemainland,occupiedCaralis,along fast, the Vandals of Africa, ontheirreturnfromaraid In 456 A.D., whentheRomanEmpirewas sinking Medieval History language andcivilization. the mountainswho,netherless,adoptedLatin years andwas oftenopposedbytheSardiniansfrom The RomandominationinSardinialasted694long thereby bringingdown theNuragiccivilization. their armies,even penetratedtheBarbagiaregion, enlarged andembellishedthecoastalcitiesand,with followed induecoursebyself-government (Viceroy) kingdom of“SardiniaandCorsica”,whichwas granted legislative autonomy(aparliament)tothe In 1353PereIVof Aragon, called“theCerimonious”, its Iberianorigins. into anentirelyCatalancity, whichstilltodaydisplays In 1354the Aragons seized andreshapedit “Sardinia andCorsica”,partoftheCrown of Aragon. between thekingdomof Arborea andthekingdomof In 1353,forreasonsofstatesurvival, war broke out Sardinia andCorsica”. the cityofSassari,namingthem“thekingdom Pisan territoriesofCagliariandGallura,alongwith campaign whichlastedayearorso,occupiedthe with thekingsof Arborea and,following amilitary In 1323JaumeIIof Aragon formedanalliance Sicily. he wishtoconquerPisanSardiniainexchange for peasants ofCatalonia),promisinghimsupportshould up ofthekingdoms Aragon and Valencia, plusthe king oftheCrown of Aragon (aconfederationmade Pope enfeoffed ittotheCatalanJaumeIIJust, a hypothetical“regnum SarduniaeetCorsicae”. The over thepossessionofSicily, establishedpropriety out in1282betweenthe Angevins andthe Aragons diplomatically the War ofthe Vespers, whichbroke In 1297,PopeBoniface VIII inordertosettle Oristano asitscapital. marine republicofPisa.Itlastedsome520years,with the politicalandculturalinfl The kingdomof Arborea was almostalways under the territory. Dante’s, was driven outbythePisanswhooccupied when thelast“giudice”Nino Visconti afriendof The kingdomofGalluraendedintheyear1288, became anautonomouscity-. Serra family of Arborea, whilethecityofSassari up betweentheDorianfamily ofGenoaandtheBas- “giudicessa” Adel Asia. The territorywas divided and cametoanendin1259,onthedeathof The kingdomof Torres, too,was pro-Genoese, became acolony ofPisa. alliance ofSardinian-Pisanforces. The territorythen its capital,S.Igia,was stormedanddestroyed byan pro-Genoese. Itwas broughttoanendin1258when The kingdomor“giudicato”ofCagliariwas politically etc. own chancelleries,own stateemblemsandsymbols, own laws (cartasdelogu),itsown nationallanguages, and tradingaffairs; eachhaditsown parliament,its own fortifi called “coronadelogu”.Eachkingdommannedits ed boundariestoprotectitsown political uence ofthepowerful 27-05-2004, 15:40:55 EUROPEAN SUBCONTINENTAL MANTLE AS REVEALED BY NEOGENE VOLCANIC ROCKS AND MANTLE XENOLITHS OF SARDINIA P69

and judicial independence (Royal Hearing). Italy, the Dukes of Savoy left and took refuge in From 1365 to 1409 the kings or “giudici” of Arborea, Cagliari for some fi fteen years. Mariano IV, Ugone III, Mariano V (assisted by his In 1847 the Sardinians spontaneously renounced their mother Eleonora, the famous giudicessa regent) autonomy and “melded” with in order and Guglielmo III (Eleonora’s French grandson) to have a single parliament, a single magistracy and a succeeded in occupying very nearly all of Sardinia single government in Turin. except the Castle of Cagliari (today Cagliari and In 1848 the Wars of Independence broke out for the Alghero). Unifi cation of Italy and were led by the kings of In 1409 Marti the Younger, king of Sicily and heir to Sardinia for thirteen years. Aragon, defeated the judicable Sardinians at In 1861 the was made part of the and conquered once and for all the entire land. Shortly newly-founded Italian nation . afterwards he died in Cagliari of malaria, without an Contemporary Era heir, and consequently the passed In 1946, by popular referendum, Italy became a into the hands of the Trastàmara Castilians - and in Republic. Sardinia - administered since 1948 by particular Ferran I of Antequera and his descendants special Statute - is today one of the twenty Italian --with the Compromise of Caspe in 1412. regions, with 1,700,000 inhabitants spread out over the provinces of Cagliari, , Oristano and Modern History , retracing more or less the territories of the In 1479, as a result of the unifi cation enacted by four ancient and glorious judicable states. Ferran II of Aragon and Isabel of Castile (the so-called “Catholic king and queen”), married ten years earlier, Acknowledgments the Crown of Spain was born. Even the “kingdom of Sardinia” (which in the new title was separated from The Authors wish to thank all the Sardinian people Corsica since that island had never been conquered) for their hospitality and warmth demonstrated during became Spanish; with the state symbol that of the all the fi eld trips to the island. Special thanks also to Four Moors. Following the failure of the military Antonio Assorgia for having introduced ML, LM, ventures against the Muslims of (1535) and RL and VM to the magic igneous world of Sardinia. (1541) Carlos V of Spain, in order to defend MIUR (PRIN 2002; VM) and CNR grants (Agenzia his Mediterranean territories from the pirate raids of 2000; ML and VM) are acknowledged. the African Berbers, fortifi ed the Sardinian shores with a system of coastal lookout towers. The kingdom of Sardinia remained Iberian for References cited approximately four hundred years, from 1323 to Albuquerque C.A.R., Capedri S. and Dostal J. (1977). 1720, assimilating a number of Spanish traditions, Mineralogy of spinel peridotite inclusions of alkali- customs, linguistic expressions and lifestyles, basalts from Sardinia. Geol. Soc. Am. Bull. 88, 1493- nowadays vividly portrayed in the folklore parades 1496. of S. Efi sio in Cagliari (May 1st), by the Cavalcade Arai S. and Abe N. (1995). Reaction of orthopyroxene on Sassari (next to last Sunday in May) and by the in peridotite xenoliths with alkali-basalt melt and its Holiday of the Redeemer in Nuoro (August 28th). implication for genesis of Alpine-type chromitite. Am. In 1708, as a consequence of the Spanish War of Mineral. 80, 1041-1047. Succession, the rule of the kingdom of Sardinia Assorgia A., Brotzu P., Morbidelli L., Nicoletti M. and passed into the hands of the Austrians, who had Traversa G. (1984). Successione e cronologia (K/Ar) landed on the island. degli eventi vulcanici del complesso -alcalino In 1717, cardinal Alberoni, minister of Felipe V of Oligo-Miocenico Dell’arcuentu (Sardegna centro- Spain, reoccupied Sardinia. occidentale). Per. Mineral. 53, 89-102. P55 to PW06 n° 6 - from Volume In 1718, with the Treaty of , the kingdom of Assorgia A., Maccioni L. and Macciotta G. (1983). Sardinia was handed over to the Dukes of Savoy, Carta geopetrografi ca del vulcanismo Pliocenico della princes of Piedmont, who rendered it perfect from Sardegna centromeridionale. Regione autonoma della imperfect bestowing upon itthe “summa potestas”, Sardegna, Assessorato all’industria that is the authority to stipulate international treaties. Ayalew D., Barbey P., Marty B., Reisberg L., Yirgu The kingdom was then Italianised. G. and Pik R. (2002). Source, genesis, and timing of In 1799, as a consequence of the in giant ignimbrite deposits associated with Ethiopian

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra Vogelsberg, centralGermany. basanitic totholeiiticvolcanic rocksfromtheMiocene Bogaard P.J.F. and Wörner G.(2003).Petrogenesisof 1576. for theIbleanvolcanism, Sicily. a transtensionaltectonicsetting:anintegrated model (1998). Nephelinitictotholeiiticmagmagenerationin Giudice A., MacciottaG., Tassinari R.and Vaccaro C. Beccaluva L.,SienaF., ColtortiM.,DiGrande A., Lo Soc. Geol.It. Quaternarie dellaSardegna centro-occidentale. nord-occidentale). - LevulcanitiPlioquaternaiedelLugudoro(Sardegna Beccaluva L.,MacciottaG.and Venturelli G.(1976). It. Min.Petr. M.te Arci (Sardegna centro-occidentale). and Venturelli G.(1974).Ilmassicciovulcanicodi Beccaluva L.,DeriuM.,MaccioniMacciottaG. 293-308. Dati geochimiciepetrografi Beccaluva L.,MacciottaG.and Venturelli G.(1975). Sardinia (Italy). clinopyroxene megacrysts ofalkalinebasiclavas from O. (1989).Harzburgite-lherzolite xenoliths and Beccaluva L.,Macciotta,G.,,F. andZeda, Sardegna -assessorato all’industria Sardegna centro-orientale. geopetrografi Beccaluva L.andMacciottaG.(1983).Carta geodynamic signifi magmatism ofthewesternMediterraneanandits and SienaF. (1994). The Cainozoiccalcalkaline Beccaluva L.,ColtortiM.GalassiB.,MacciottaG. problems. C.A. (1985).GeochronologyinSardinia:resultsand Beccaluva L.,Civetta L.,MacciottaG.andRicci Mineral. Petrol. evidence fromSardinianperidotitexenoliths. evolution oftheEuropeanlithosphericmantle:new Siena F., Vaccaro C.and Wilson M.(2001).Multistage Beccaluva L.,BianchiniG.,ColtortiM.,Perkins W.T., 2811-2827. diamond aggregates. the compositionofhigh-pressuremantlemeltsusing Baker, M.B.andStolper, E.M.(1994).Determining Hybridization. for plume-lithosphereinteractionandpolybaricmelt intraplate volcanism, Sana’a, Yemen: implications Macpherson C.G.(1997).PetrogenesisofQuaternary Baker J.A.,MenziesM.A., Thirlwall M.F. and 66, 142-1448. continental fl Rend. Soc.It.Min.Petr. 30,1069-1080. ood basalts. ood ca delvulcanismoPliocenicodella 94,1437-1457. J. Petrol. Chem.Geol. 142,284-297. cance. Boll. Soc.Geol:It Geochim. Cosmochim. Acta 36,1359-1390. Geochim. Cosmochim. Acta Boll. Geofi Regione autonomadella 77,331-345. ci sullevulcanitiPlio- J. Petrol. J. J. Petrol. 40,57-72. s. . Appl. . 95,339-350. 44,569-602. Rend.Soc. 39,1547- Contrib. Boll. 58, 36,

heritage inthePliocenepost-collisionalvolcanism of R. and Tonarini S.,(1982).Miocenecalc-alkaline Cioni R.,ClocchiattiDiPaola G.M.,Santacroce Appl. Geochem.10,517-530. exploration forgold intheOsiloarea,Sardinia,Italy. Dack L.andGijbelsR.(1995).Hydrogeochemical Cidu R.,Fanfani L.,Shand P., Edmunds W.M., Van’t Contrib. Mineral.Petrol.140,404-421. rocks fromLogudoro(NorthernSardinia,Italy). (2001) ZeolitisationofOligo-Miocenevolcaniclastic Cerri G.,CappellettiP., Langella A. andde’ GennaroM. 47. volcanique tertiaire. précieux deSardaigneoccidentaleetleurencaissant des minéralisationsàmétauxdebaseet Caron C.andOrgeval J.J.(1996).Origineduplomb 160, 667-679. to anew evolutionary model. central Mediterraneanbasins:aforward modelingtest R. (1998). The two-stage openingofthewestern- Carminati E., Wortel M.J.R.,MeijerP.Th. andSabadini Geof. Teor.Boll. Appl. compression andextension intheSardinianbasement. Funedda A., OggianoG.andPasci S.(1994). Tertiary Carmignani L.,BarcaS.,DisperatiFantozzi P., costa orientalesarda. Nuova manifestazionedivulcanismorecentepressola Calvino F. (1965).IbasaltidiRiuGirone(). Naz. Lincei evidence oftheBosetivolcanic complex, G., (1980). Volcanological andmagmatological Brotzu P., MorbidelliL.,PiccirilloE.M.and Traversa 66, 151-184. volcanic complex (SWSardinia,Italy). evolution ofcalcalkalinemagmasfromthe Arcuentu Traversa G.andFranciosiL.(1997a).Petrology Brotzu P., LonisR.,MellusoL.,Morbidelli Cagliari (Sardegna sud-orientale). G. (1975).IldistrettovulcanicodiCapoFerrato Brotzu P., Ferrini V., MorbidelliL.and Traversa Mineral. nelle lave basaltichedelsettoreOrosei-Dorgali. Sui mineralidiaggregati nodulariultrafemicipresenti Brotzu P., DiSabatinoB.andMorbidelliL.(1970). characteristics. (Italy): petrology, geochemistryandSr-isotope Tertiary volcanic complex ofNarcao,SW-Sardinia (1997b). The orogenicbasalt-andesitesuitesfromthe Brotzu P., Callegari E.,Morra V. andRuffi of Sardinia. Brotzu (ed)(1997). The Tertiary calcalkalinevolcanism . 45,1-26. 34,99-118. 47,317-366. Per. Mineral., Spec.Issue, vol66 Per. Mineral. C. Rend. Acad. Sci.Paris La Ric.Scient. 36,5-62. 66,101-150. Rend. Sem.Sci.Univ. Earth Planet.Sci.Lett. 8,1218-1243. Per. Mineral. Atti Accad. 323,41- 27-05-2004, 15:40:59 n R. ni Per. Per.

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Monte Arci (Sardinia, Italy). J. Volcanol. Geotherm. peridotite inclusions in basalts from Sardinia. Contrib. Res. 14, 133-167. Mineral. Petrol. 54, 245-254. Civetta L., D’Antonio M., Orsi G. and Tilton G.R. Doukhan N., Doukhan J.-C., Ingrin J., Jaoul O. and (1998). The geochemistry of volcanic rocks from Raterron P. (1993). Early partial melting in pyroxenes. island, Sicily Channel: petrogenesis and Am. Mineral. 78, 1246-1256. characteristics of the mantle source region. J. Petrol. Downes H. (1990). Shear zones in the upper mantle 39, 1453-1491. - relation between geochemical enrichment and Civetta L., Orsi G., Scandone P. and Pece R. deformation in mantle peridotites. Geology 18, 374- (1978). eastwards migration of the Tuscan anatectic 377. magmatism due to anticlockwise rotation of the Downes H., Thirlwall M.F. and Trayhorn S.C. (2001). Apennines. Nature 276, 604-606. Miocene subduction-related magmatism in southern Conte A.M. (1997). Petrology and geochemistry of Sardinia: Sr-Nd and oxygen isotopic evidence for tertiary calcalkaline magmatic rocks from the Sarroch mantle source enrichment. J. Volcanol. Geotherm. district (Sardinia, Italy). Per. Mineral. 66, 63-100. Res. 106, 1-21. Conticelli S., D’Antonio M., Pinarelli L. and Dupuy C., Dostal J. and Bodinier J.L. (1987). Civetta L. (2002). Source contamination and mantle Geochemistry of spinel peridotite inclusions in basalts heterogeneity in the genesis of Italian potassic and from Sardinia. Mineral. Mag. 51, 561-568. ultrapotassic volcanic rocks: Sr-Nd-Pb isotope data Dupuy C., McNutt R.H. and Coulon C. (1974) from Roman province and southern. Tuscany Mineral. Détermination de 87Sr/86Sr dans le andésites Petrol. 74, 189-222. Cénozoiques et les laves associées de Sardaigne Nord- Coulon C. (1977). Le volcanisme calco-alcaline Occidentale (Italie). Geochim. Cosmochim. Acta 38, cénozoique de Sardaigne (Italie): pétrographie, 1287-1296. géochimie et genèse des laves andesitiques et des Edgar A.D., Lloyd F.E., Forsyth D.M. and Barnett ignimbrites. Signifi cation geodinamique. Thèse Univ. R.L. (1989). Origin of glass in upper mantle xenoliths Marseille. from the Quaternary volcanics of Gees, west Eifel, Coulon C., Dostal J. and Dupuy C. (1978). Petrology Germany. Contrib. Mineral. Petrol. 103, 277-286. and geochemistry of the ignimbrites and associated Franciosi L., Lustrino M., Melluso L., Morra V. and lava domes from N.W. Sardinia. Contrib. Mineral. D’Antonio M. (2003). Geochemical characteristics Petrol. 68, 89-98. and mantle sources of the Oligo-Miocene primitive Coulon C., Megartsi M., Fourcade S., Maury R.C., basalts from Sardinia. Ofi oliti in press. Bellon H., Louni-Hacini A., Cotten J., Coutelle A. Frey F.A. and Prinz M., (1978). Ultramafi c inclusions and Hermitte D. (2002). Post-collisional transition from San Carlos, Arizona: petrologic and geochemical from calc-alkaline to alkaline volcanism during the data bearing on their petrogenesis. Earth Planet. Sci. Neogene in Oranie (Algeria): magmatic expression of Lett. 38, 129-176. a slab breakoff. Lithos 62, 87-11. Gao S., Luo T.C., Zhang B.R., Hang H.F., Han Y.W., Dautria J.M. and Liotard J.M. (1990). Les basaltes Zhao Z.D. and Hu Y.K. (1998). Chemical composition d’affi nite’ tholeiitique de la marge Mediterraneenne of the continental crust as revealed by studies in east Francaise. C. R. Acad. Sci. Paris 311, 821-827. China. Geochim. Cosmochim. Acta 62, 1959-1975. Di Battistini G., Montanini A. and Zerbi M. (1990). Gasperini D., Blichert-Toft J., Bosch D., Del Moro A., Geochemistry of volcanic rocks from southeastern Macera P., Télouk P. and Albarède F. (2000). Evidence Montiferro. N. Jahrb. Miner. Abh. 162, 35-67. from Sardinian basalt geochemistry for recycling of Doglioni C., Harabaglia P., Merlini S., Mongelli F., plume heads into the Earth’s mantle. Nature 408, Peccerillo A. and Piromallo C. (1999). Orogens and 701-704. slabs vs. their direction of subduction. Earth Sci. Rev. Girod M., Dautria J.M. and De Giovanni R. (1981). 45, 167-208. A fi rst insight into the constitution of the upper P55 to PW06 n° 6 - from Volume Doglioni C., Mongelli F. and Pialli G. (1998). mantle under the Hoggar area (southern Algeria): Boudinage of the Alpine belt in the Apenninic back- the lherzolite xenoliths in the alkali basalts. Contrib. arc. Mem. Soc. Geol. It. 52, 457-468. Mineral. Petrol. 77, 66-73. Dostal J., Coulon C. and Dupuy C., (1982). Cainozoic Halliday A.N., Dickin A.P., Hunter R.N., Davies G.R., andesitic rocks of Sardinia (Italy). In Thorpe (ed) Dempster T.J., Hamilton P.J. and Upton B.G.J. (1993). Andesites, 353-370. Formation and composition of the lower continental Dostal J.M. and Capedri S., (1976). Uranium in spinel crust: evidence from Scottish xenolith suites. J.

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra lithosphere interactions. characteristics andimplicationsforasthenosphere- Rhon area(centralGermany): petrology, mantlesource cenozoic alkalinerift-typevolcanic rocksfromthe element andisotope(Sr, Nd,O)geochemistryof Jung S.andHoernes(2000). The major- andtrace- genesis. constraints onpartitioncoeffi abundances inmegacrysts andtheirhostbasalts: Irving A.J. andFrey F.A. (1984). Trace element 15-35. from Ascension island, south Atlantic Ocean. south Atlantic island, from Ascension Origin ofdifferentiated volcanic andplutonicrocks Kar A., Weaver B.,Davidson J.andColucciM(1998). 177. mantle sources. continental alkalineandtholeiiticbasaltstheir (central Germany). Constraintsontheoriginof Cenozoic mafi element systematicsandisotopegeochemistryof Jung S.andMasberg P. (1998).Major- andtrace- 99, 27-53. the Provence, southernFrance. paleostresses timechangesintheOligocenebasinsof Guieu G.(1993). Tectonic-stratigraphic recordof Hyppolite J.C., Angelier J.,Bergerat F., NuryD.and western andcentralEurope. mantle upwellingbeneaththeeastern Atlantic and Seismic andgeochemicalevidence forlarge-scale Hoernle K.,Zhang Y.S. andGrahamD.,(1995). Geophys. Res. e prospettive tecnico-economiche. Caratteristiche geogiacimentologicheegeochimiche al vulcanismooligo-miocenicodellaSardegna. and UrasI.(1966).Idepositidicaolinoassociati Ligas P., Padalino G.,Palomba M., Tamanini M. 66, 7-61. and riftingstagesinSardinia:areview. Brotzu P. (1997).Oligo-Miocene volcanic sequences Lecca L.,LonisR.,LuxoroS.,MelisE.,SecchiF. and 236 pp. and glossaryofterms. Le Maitre(ed)(2002).Igneousrocks– A classifi 10, 33-81. (nota III).IbasaltidiOroseieDorgali. rocce vulcanichepost-MiocenichedellaSardegna Lauro C.(1939).Studiogeologicopetrografi Mineral. 8 (nota I).LacolatabasalticadiBariSardo. rocce vulcanichepost-MiocenichedellaSardegna Lauro C.(1937).Studiogeologicopetrografi 39, 1009-1024. Geochim. Cosmoch. Acta , 109-121. 98,581-607. c volcanic rocksfromthe Vogelsberg J. Volcanol.Res. Geotherm. 2nd ed.Cambridge Univ. Press J. Volcanol. Geotherm.Res. Nature cients andmegacryst Tectonophysics 48,1201-1221. 374,34-39. Proc. Int.Congr. Per. Mineral. Per. Mineral. J. Petrol. J. co delle co delle co 86, 151- cation 226, Per. Per.

I end-member. Lustrino M.andDallaiL.(2004).OntheoriginofEM- 143-144. of Sardinia. isotope compositionofPlio-Quaternaryvolcanic rocks F. andPetterutiLiebercknect A.M. (2003).Oxygen Lustrino M.,MellusoL.,Morra V., DallaiL.,D’Amelio district (NESardinia,Italy). study fromtheOrosei-Dorgali Pliocenevolcanic transition fromalkalinetotholeiiticmagmas:acase Lustrino M.,MellusoL.andMorra V. (2002). The Sardinia (Italy). the genesisofPlio-Pleistocenevolcanic rocksfrom of lower continentalcrustandlithosphericmantlein Lustrino M.,MellusoL.andMorra V. (2000). The role 68, 13-42. xenoliths fromcentralSardinia(Italy). of glassanditsrelationshipswithphlogopiteinmantle Lustrino M.,MellusoL.andMorra V. (1999).Origin realm. Inst.Geophys. Cenozoic igneousactivity inthecircum-Mediterranean Lustrino M.(2003).Spatialandtemporalevolution of petrology. Lustrino M.(2001).Debatedtopicsofmodernigneous Petrogr. Acta volcanic rocksfromcentral-southernSardinia. Lustrino M.(2000c).Petrogenesisoftholeiitic 42, 724-757. evolution ofthecircum-ItalianRealm. Lustrino M.(2000b).Phanerozoicgeodynamic Mediterranean area:areview. the NeogenetoPresentevolution ofthewestern Lustrino M.(2000a). Volcanic activity during PhD Thesis, Università diNapoliFederico II the evolution oftheEuropeansubcontinentalmantle. volcanic rocksfrom Sardinia:possibleimplicationson Lustrino M.(1999).PetrogenesisofPlio-Quaternary Sindia (centralSardinia). petrology of Tertiary orogenicvolcanic rocksfrom Secchi F. (1997).Plagioclasetextures, mineralogyand Lonis R.,Morra V., LustrinoM.,MellusoL.and Euroclay ,Italy, 22-26June2003. Case Fresu(, northernSardinia).Proc.10 and BrotzuP. (2003) The clinoptilolitedepositof Lonis R.,FerciaM.L.,GhiaraMorbidelliP. 423-433. la sourcemantellique. (France): contaminationcrustaleethétérogénéitéde (1999). BasanitesetnéphélinitesduBas-Languedoc Liotard J.M.,BriqueuL.,DautriaJ.M.andJakniB. Iglesias Centenario dell’AssociazioneMineraria Sarda, , 99-114. Per. Mineral. Proc. 4°Forum FIST-Geoitalia, Bellaria 43,1-16. N. Jahrb. Miner. Abh. Earth Planet.Sci.Lett. PolishSci. Acad. 70,1-26. Bull. Soc.Geol.France Per. Mineral. Lithos Ofi oliti 63,83-113. 179,85-100. 25,87-101. 66,185-210. 180,259-270. Int. Geol.Rev. Per. Mineral. M-28(363) , 188pp. 27-05-2004, 15:41:03 Miner. 170, th ,

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231-232. Stromboli volcanoes: petrogenetic, geodynamic and Lustrino M., Melluso L., Morra V. and Secchi F. volcanological implications. Mineral. Petrol. 73, 93- (1996). Petrology of Plio-Quaternary volcanic rocks 105. from central Sardinia. Per. Mineral. 65, 275-287. Pécskay Z., Edelstein O., Seghedi I., Szakàcs A., Martì J., Mitjavila J., Roca E. and Aparicio A. (1992). Kovacs M., Crihan M. and Bernard A. (1995). K-Ar Cenozoic magmatism of the Valencia Trough (western datings of Neogene-Quaternary calc-alkaline volcanic Mediterranean): relationship between structural rocks in Romania. Acta Vulcanol. 7, 53-61. evolution and volcanism. Tectonophysics 203, 145- Petteruti Lieberknecht A.M., Fedele L., D’Amelio 165. F., Lustrino M., Melluso L. and Morra V. (2003). Mascle G.H., Tricart P., Torelli L., Bouillin J-P., Rolfo Plio-Pleistocene ingeous activity in Sardinia (Italy). F., Lapierre H., Monié P., Depardon S., Mascle J. and Geophys. Res. Abstr. 5, 7260. Peis D. (2001). Evolution of the Sardinia channel Rapp R.P. and Watson E.B. (1995). Dehydration (western Mediterranean): new constraints from a melting of metabasalt at 8-32 kbar: implications for diving survey on Cornacya seamount off SE Sardinia. continental growth and crust-mantle recycling. J. Mar. Geol. 179, 179-202. Petrol. 36, 891-931. Mattioli M., Guerrera F., Tramontana M., Raffaelli Raterron P., Bussod G.Y., Doukhan N. and Doukhan G. and D’Atri M. (2000). High-Mg Tertiary basalts J.C. (1997). Early partial melting in the upper mantle: in southern Sardinia (Italy). Earth Planet. Sci. Lett. an A.E.M. study of a lherzolite experimentally 179, 1-7. annealed at hypersolidus conditions. Tectonophysics MacDonald R. (1974). Nomenclature and 279, 79-91. petrochemistry of the peralkaline oversaturated Rossi P., Guennoc P., Réhault J.P., Arnaud N., Jakni extrusive rocks. Bull. Volc. 54, 78-83. B., Poupeau G., Tegyey M., Ferrandini J., Sosson Montanini A., Barbieri M. and Castorina F. (1994). M., Beslier M.O., Rollet N. and Gloaguen R. (1998). The role of fractional crystallization, crustal melting Importance du volcanisme calco-alcalin Miocène sur and magma mixing in the petrogenesis of rhyolites la marge sud-ouest de la Corse (campagne MARCO). and mafi c inclusion-bearing dacites from the Monte C. R. Acad. Sci. Paris 327, 369-376. Arci volcanic complex (Sardinia, Italy). J. Volcanol. Rutter M.J., (1987). The nature of the lithosphere Geotherm. Res. 61, 95-120. beneath the Sardinian continental block: mantle and Montigny R., Edel J.B. and Thuizat R. (1981). deep crustal inclusions in mafi c alkaline lavas. Lithos Oligo-Miocene rotation of Sardinia: K-Ar ages and 20, 225-234. paleomagnetic data of Tertiary volcanics. Earth Savelli C., Beccaluva L., Deriu M., Macciotta G. Planet. Sci. Lett. 54, 261-271. and Maccioni L., (1979). K/Ar geochronology and Morra V., Secchi F.A. and Assorgia A. (1994). evolution of the Tertiary “calc-alkalic” volcanism of Petrogenetic signifi cance of peralkaline rocks from Sardinia (Italy). J. Volcanol. Geotherm. Res. 5: 257- Cenozoic calcalkaline volcanism from SW Sardinia, 269. Italy. Chem. Geol. 118, 109-142. Savelli C. and Pasini G. (1973). Preliminary results of Morra V., Secchi F.A.G., Melluso L. and Franciosi L. K-Ar dating of basalts from eastern Sardinia and the (1997). High-Mg subduction-related Tertiary basalts in gulf of Orosei. Giornale di Geologia 39, 303-312. Sardinia, Italy. Lithos 40, 69-91. Scaillet B. and MacDonald (2003). Experimental Nimis P. (1999). Clinopyroxene geobarometry of constraints on the relationships between peralkaline magmatic rocks, part 2: structural geobarometers for rhyolites of the Kenya Rift Valley. J. Petrol. 44, 1867- basic to acid, tholeiitic and mildly alkaline magmatic 1894. systems. Contrib. Mineral. Petrol. 135, 62-74. Shaw J.E., Baker J.A., Menzies M.A., Thirlwall M.F. Novembre D., Di Sabatino M., Pasculli A., Iezzi G. and Ibrahim K.M. (2003). Petrogenesis of the largest and Baliva A. (2003). Valorizzazione dei caolini di intraplate volcanic fi eld on the Arabian plate (Jordan): P55 to PW06 n° 6 - from Volume Romana (Sassari). Proc. I Congr. Nazionale AIGA, a mixed lithosphere-asthenosphere source activated by , 19-20 Feb. lithospheric extension. J. Petrol. 44, 1657-1679. Panza G.F. (1984). Structure of the Lithosphere Speranza F. (1999). Paleomagnetism and the Corsica- Asthenosphere system in the Mediterranean region. Sardinia rotation: a short review. Boll. Soc. Geol. It. Ann. Geophys. 2, 137-138. 118, 537-543. Peccerillo A. (2001). Geochemical similarities Sun S.S. and McDonough W.F. (1989). Chemical and between the Vesuvius, Phlegraean fi elds and isotopic systematics of oceanic basalts: implications for

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Volume n° 6 - from P55 to PW06 P69 - P69 Leaders: M.Lustrino,P. Brotzu,R.Lonis,L.Melluso,V. Morra Pearson D.G.andNowell G.M.(1999).Magmatism Turner S.P., PlattJ.P., George R.M.M.,Kelley S.P., Volcanol. Geotherm.Res. of Marsiliseamount(southern Tyrrhenian Sea). F. (2002). Volcanological andpetrologicalevolution Trua T., SerriG.,MaraniM.,Renzulli A. andGamberi 307-322. Hyblean Plateau,Italy. from thetholeiiticandalkalinevolcanic rocksofthe African plate:geochemicalandisotopicevidence evolution ofthelithosphericmantlealongn. Trua T., EsperançaS.andMazzuoliR.(1998). The Mineral. dei Sardialignment(northernSardinia-Italy). Hercynian basicdyke magmatismoftheConcas-Alà Traversa G.,RoncaS.andPasquali C.(1997).Post- 2000gc000094/fs2000gc000094.html. 2000, http://146.201.254.53/publicationsfi component inthemantle. complementary accumulationoftheEnrichedMantleI by crustaldelaminationinsubductionzonesand Tatsumi Y. (2000).Continentalcrustformation Geol. Soc.Long. Spec.Publ. the oceanbasins”,Saunders A.D., NorryM.J.(eds), mantle compositionsandprocesses.In“Magmatismin 66,233-262. Contrib. Mineral. Petrol. Geochem. Geophys.Geosyst., 114,441-464. 42,313-345. nal/articles/ 131, Per. Per. J. J. processes. Victoria, Australia, andtheirrelevance tomantle T.J. (1997).Glassesinmantlexenoliths fromwestern Yaxley G.M.,Kamenetsky V., GreenD.H.andFalloon 369-383. central Europe. extension-related alkalinemagmatisminwesternand Wilson M.andDownes H.(1991). Tertiary-Quaternary 140, 180-189. plume volcanism (CECV). of MiocenetholeiitesinthecentralEuropeanCenozoic Wedepohl K.H.(2000). The compositionandformation domain SESpain. associated withorogeniccollapseoftheBetic-Alboran temperature andtime. melting ofamphiboliteat10kbar:theeffects of Wolf M.B.and Wyllie P.J. (1994).Dehydration- Geol. Soc. Am. Spec.Paper “mantle plumes:theiridentifi central EuropeInErnstR.E.andBuchanK.L.(eds) Tertiary-Quaternary volcanic province ofwesternand instabilities intheuppermantle:evidence fromthe magmatism relatedtoshort-wavelength convective Wilson M.andPatterson R.(2001).Intraplate Earth Planet.Sci.Lett. J. Petrol. J. Petrol. Contrib. Mineral. Petrol. 32,811-849. 352,37-58. 40,1011-1036. Contrib. Mineral. Petrol. cation throughtime”. 148, 433-446. 27-05-2004, 15:41:07 115,

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