B17_copertina_R_OK C August 20-28,2004 Florence -Italy

Field Trip Guide Book - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg Pre-Congress AND CONTACT AUREOLE EMPLACEMENT MECHANISMS PETROLOGY, (EASTERN ALPS): DI RIES-RIESERFERNER INTRUSION OFVEDRETTE THE PERIADRIATIC 32 Volume n°2-fromB16toB33 GEOLOGICAL CONGRESS nd INTERNATIONAL B17 28-05-2004, 17:18:34 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, Como), Giulio Pavia (Università di Torino), Raffaele Pignone (Servizio Geologico Regione Emilia-Romagna, Bologna) and Riccardo Polino (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

B17_copertina_R_OK D 20-05-2004, 14:36:28 Volume n° 2 - from B16 to B33

32nd INTERNATIONAL GEOLOGICAL CONGRESS

THE PERIADRIATIC INTRUSION OF VEDRETTE DI RIES - RIESERFERNER (EASTERN ALPS): PETROLOGY, EMPLACEMENT MECHANISMS AND CONTACT AUREOLE

AUTHORS: B. Cesare1,2, A.M. Fioretti2, C. Rosenberg3

1Dipartimento di Mineralogia e Petrologia, Università di Padova - Italy 2C.N.R. Istituto di Geoscienze e Georisorse, Sezione di Padova - Italy 3Department of Geology, Freie Universität, Berlin - Germany

Florence - Italy August 20-28, 2004

Pre-Congress B17

B17_R_OK A 20-05-2004, 14:41:48 Front Cover: The Collalto - Hochgall (3436 m a.s.l.) is the highest peak of the Vedrette di Ries massif. It is composed of fine-grained tonalite.

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Leaders: B. Cesare, A.M. Fioretti, C. Rosenberg

Introduction this contact aureole. During the Oligocene the Alpine chain was the centre During the fi eld trip we will show the key outcrops of an extensive magmatism, mainly represented by of the pluton, discussing both the results and the new calc-alkaline, which resulted in a series of plutons ideas arising from detailed structural, petrologic and situated along and adjacent to the Periadriatic geochemical investigations performed over the past Lineament. These intrusives are hence referred to as twenty years. “Periadriatic plutons”. Geologic and topographic maps With an outcrop length of approximately 40 km, 1:25.000 topographic map, sheet n. 035 “Valle Aurina and a vertical exposure of 2500 m from base to roof, - Vedrette di Ries”, Ed. Tabacco. Vedrette di Ries (Rieserferner) represents one of the Cammelli F. (1994) Alpi pusteresi. Guida best exposed plutons worldwide (Figure 1). escursionistico-alpinistica. Available also in The intrusion of the pluton is characterised by three German, Ed. Athesia. major pulses of tonalitic to granodioritic composition, Carta Geologica d’Italia 1:100.000, sheet n. 4b with distinct petrographic and geochemical signatures. “Dobbiaco”. The ascent of these magmas was controlled by the Geologic Map of Italy 1:50.000, sheet n. 009 Defereggen-Anterselva-Valles (DAV) line, which “Anterselva” (in print). strikes along large parts of the southern margin of the Hammerschmidt K. 1981 Isotopengeologische pluton. The contact aureole of the intrusion developed Untersuchungen am Augengneis vom Typ in the metapelitic country rocks, and is characterised Campo Tures bei Rain in Taufers, Südtirol. by a complete zoneography from andalusite- Mem.Sci.Geol., 34, 273-300, with geologic map. staurolite to sillimanite-K-feldspar. The presence of Mager D. 1985 Geologische Karte des synmetamorphic andalusite-bearing veins, related to Rieserfernergruppe zwischen Magerstein und the dehydration of metapelites, is a unique feature of Windschar (Südtirol). ‘Der Schlern’, 6, Bozen. Volume n° 2 - from B16 to B33 n° 2 - from Volume

Figure 1 - Geologic map of the Eastern Alto Adige (South Tyrol) from Dal Piaz (1934)

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Volume n° 2 - from B16 to B33 B17 - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg the Vedrette diRiespluton. The Dolomites,south Most oftheseunitsareoutcroppinginthearea Romandes» inSwitzerland. Penninic Unitsandthecover nappesofthe«Préalpes the two oceanicdomains,foundintheuppermost (4) theBriançonnais,amicrocontinentseparating the contactbetweenEuropeanand Adriatic units; by ophiolitesand«Buendnerschiefer»,locatedalong ocean andthePiedmont-Ligurianocean),represented (3) theremnantsoftwo oceanicdomains(the Valais Southalpine nappessouthofthePeriadriaticLine; the PeriadriaticLineandbyunmetamorphosed Austroalpine basementandcover nappesnorth of Adriatic (ApulianandInsubric)margin, foundinthe massifs, andthelowermost penninicnappes;(2)the represented bytheHelvetic cover nappes,theexternal Froitzheim etal.,1996):(1) The Europeanmargin, into thefollowing paleogeographicdomains (e.g. The Alpine chain(Figure2)maybesubdivided Regional geologicsetting Senarclens-Grancy W. (1972)GeologischeKarteder Schulz B.(1994)GeologischeKartedes Altkristallin Geol. B. A., Wien. westlichen Deferegger Alpen, Ostirol,1:25.000. 124; 1-28. östlich des Tauferer Tals. ErlangerGeol. Abh., Figure 2-MainStructuralandpaleogeographicaldomainsofthe Alps (fromDalPiazetal.,1975). European continentalmargin werealsosubducted,as (early Eocene),below the Adriatic plate.Parts ofthe Paleocene), followed bythatofthe Valais ocean of theJurassicPiedmont-Ligurianocean(early contrast, Tertiary eclogitesrefl Carpathians totheeastern Alps (Kozur, 1991).In Triassic oceanwhoseremnantsarefoundfrom the of theMeliata-Halstattocean(Neubauer, 1994),a eclogite metamorphismresultsfromtheclosure Alpine region (Froitzheimetal.,1996).Cretaceous events whichoccurredindifferent partsofthe ages ofeclogitizationcorrespondtodifferent tectonic Valais andPiedmont-Ligurianoceans. These two are partofthePenninicandophioliticunits the Austroalpine domains,whereasthelatterones occur inthe Alps. The formeronesarefoundin Eclogites ofCretaceousaswell Tertiary age margin. basement rocks(ZentralGneiss)fromtheEuropean window (Schieferhuelle),whilstitscoreexposes Ries. The oceanic unitsformtheborderof Tauern window (the Tauern window) northof Vedrette di European units,ascanbeseeninalarge tectonic Brianconnais?) arethrustedover theoceanic and of theintrusion. The latter unit(=thebasement?the the Austroalpine basementmakes thecountryrock of thepluton,belongtoSouthalpinedomain; ect thesubduction 20-05-2004, 14:42:36 THE PERIADRIATIC INTRUSION OF VEDRETTE DI RIES - RIESERFERNER (EASTERN ALPS): PETROLOGY, EMPLACEMENT MECHANISMS

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shown by the occurrence of high-pressure and ultra- Alps and in the Po Plain affected the southern part of high pressure rocks in the Dora Maira massif of the the chain. western Alps (Chopin et al., 1991). During the Oligo-Miocene the eastern Alps and the The Periadriatic Magmatism and area of Vedrette di Ries were affected by intense N- Vedrette di Ries. S shortening, contemporaneous with orogen-parallel The Periadriatic magmatism took place along the extension, resulting in eastward extrusion. This entire Alpine chain during the Oligocene, (Exner, tectonic regime formed large pop-up structures (the 1976; Laubscher, 1985) i.e., long after the continental Tauern Window), delimited by syn-convergence, low collision between the African (Insubric) and European angle normal faults at its eastern (the Brenner Fault) plates, which occurred starting from the Eocene. and western margins (the Katschberg Fault). Lateral Based on their andesitic, calc-alkaline characters and extrusion, was accommodated by sets of conjugate geological setting these magmas were interpreted as dextral (e.g., the Periadriatic Line) and sinistral (e.g., products of a subduction process (Sassi et al., 1980, the SEMP Line) strike-slip faults. The widespread Bellieni et al., 1981, Kagami, 1991). Dal Piaz & occurrence of subhorizontal E-W striking stretching Venturelli (1983) and Laubscher (1985) questioned lineations and fold axes in the country rocks of this interpretation, and proposed that the magmatism, Vedrette di Ries records this phase of orogen-parallel postdating the main tectono-metamorphic event extension. related to the collision, developed during a short Ongoing shortening and thickening of the orogen extensional phase following the continental collision. caused a propagation of the deformation front According to these authors this extensional phase towards the more external zones of the chain in the triggered the ascent and emplacement of the middle- to late Miocene. Hence, the Jura Mountains Periadriatic plutons along a belt extending for ca. and thrusting in the Molasse basin were initiated to 700 km from the western Traversella body, in the the north of the Alps, whilst thrusting in the Southern Piemonte region, to the eastern Pohorje pluton in Volume n° 2 - from B16 to B33 n° 2 - from Volume

Figure 3 - Simplifi ed tectonic map of the Alps, with enlargements of some segments of the PFS showing the spatial distribution of the Oligo-Miocene dikes and of the Periadriatic plutons. Only the major faults of Tertiary age are shown. Redrawn after Bigi et al. (1990). Faults: CL: Canavese Line; DAV: DAV Line; GL: Giudicarie Line; GTL: Gailtal Line; IL: Insubric Line; LT: Lavantal Line; PL: Pustertal Line. Plutons: A: Adamello; An: Andesites of the Canavese Line; B: Bergell; Bi: Biella; K: Karawanken; L: Lesachtal body; M: Miagliano pluton; P: Pohorje; R: Rieserferner; Re: Rensen; T: Traversella; TL: Tonalitic Lamellae. Full circles: dikes. Note that only part of the dikes are dated. Most of them are inferred to be Oligocene on the basis both of petrographic analogy with the dated ones and of crosscutting relationships with their country rocks. The size of the dikes is exaggerated by several orders of magnitude.

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Volume n° 2 - from B16 to B33 B17 - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg tens ofsquarekilometersinthecentralandnorthern 4). The roofoftheplutoncropsoutover several allowing ustoreconstructits3D geometry(Figure an exceptional exposure oftheintrusive body, Steenken etal.,2002)and2000mofreliefprovide Post-intrusive tiltingofthepluton(Borsietal.,1978; Geometry andemplacementofthepluton 1980; Bellienietal.,1982). as ageochemicallydistinctmagmaticbody(Bellieni, Vedrette diRiesplutoniccomplex, isnow recognized Cima di Vila pluton,onceconsideredpartofthe of theeasternPeriadriaticmagmatism. The smaller Vedrette diRiesconstitutesthemainplutonicbody emplacement alongtheactive Periadriaticlineaments. have anoverall E-Welongatedshape,refl –Altberg, Cima di Vila –Zinsnock, Vedrette diRies) sector ofthechainmostplutons(Rensen,Monte Alto Southern Alps (DalPiazand Venturelli, 1983).Inthis occurrences arereportedinthenorthernpartof concentrated inthe Austroalpine domain.Onlyminor In theeastern Alps thePeriadriaticmagmatismis (Trommsdorff andNievergelt, 1983). Penninic crystalline,ophiolitesand Austroalpine crust intruding fi sedimentary cover, andbytheBregaglia-Iorio pluton the South Alpine basementanditsPermo-Mesozoic represented bythe Adamello batholith,whichintruded magmatism reachesitswidestextension andis Venturelli, 1983).InthecentralsectorPeriadriatic covers andhigh-Kandesiticdikes (DalPiazand Magmatism isrepresentedbysmallplutons,volcanic the overthrusted Austroalpine continentalcrust. Southern Alps andextend uptothelimitwith a NE-SWorientation,plutonsintrudemainlythe into threemainsectors.Inthewesternsector, with whole Periadriaticmagmatismcanbesubdivided and ultrapotassiclamprophiriccompositions. The well asdikes rangingfromandesitictoshoshonitic volcanic rocksof calc-alkalineorogenicseries,as The Periadriaticmagmatismincludesplutonicand 1995). geochemical signature(Von Blankenburg andDavis, by thedistribution ofthemagmaticbodiesandtheir Periadriatic magmasbyslabbreak-off, assuggested interpretation isconsistentwiththegenerationof 1995; Steenken, 2000;Rosenberg, inpress). The latter in atranspressive tectonicsetting(Rosenberg etal., plutons showed thatascentandemplacementoccurred However, structuralinvestigations ofsomethese Slovenia (Figure3). ve nappesofthe Alpine pile,including ectingtheir at highercrustallevels. feeder (Figure7),whichmayhave fedotherplutons representing theuppercontinuationof Vedrette level thanthemainbodyandisthereforeinferredas the plutoninmapview) representsa highercrustal continuation ofthesteepzone(theeasterntail DAV mylonites. As aresultoftilting,theeasternmost in thesouthernpartofpluton,adjacentto Therefore, ascentofthetonaliticmagmasoccurred zone actedasthefeederforintrusion(Figure7). steeply orientedpartoftheplutonsuggeststhatthis The spatialcoincidenceofthesestructureswiththe rocks. occur inotherpartsofthepluton,norenclosing hundreds ofmeters(Figure6).Suchstructuresdonot are foundfromtheoutcropscaletothatofseveral (Steenken etal.2000; Wagner etal.,inreview) patterns withsteeplyplungingmagmaticlineations Within partsofthissteepzone,concentricfoliation tectonic intrusion. solid-state mylonitesoftheDAV, suggestasyn- preserved magmaticfabrics, orientedparalleltothe country rocksandtotheDAV (Figure5).Locally dipping tothesouth,parallelfoliationof The southernmargin of the intrusionissteeply inclined plane(Figure7; Wagner etal.,inreview). as resultingfromextensional fracturingalongagently instead ofstoping,thediscordantcontactsareinferred occur intheimmediatevicinityofcontact.Hence, 2000) andrarexenoliths, generally<50cmlong,only stoping. Stopedblocksarelacking(Steenken etal., in thecountryrocks,but there isnofi Large partsoftheroofarediscordanttofoliation (Wagner etal.,inreview). of thetonaliteratherthanfromregional deformation associated domesresultfromforcefulemplacement from thepluton,suggestingthatthisfoldand to allregional structuresofthecountryrocksaway striking axialplaneofthesynformisperpendicular structures separatedbyasynform. The north-south show thattheroofofplutonconsiststwo domal (Figure 6)andacontourmapofthecontact4) The foliationpatterninthemainbodyofintrusion dipping mainbodyofthepluton(Figure5) coarse-grained tonalitesissubhorizontalinthegently- 5). The contactbetweenthefi south-dipping, asitgetsclosertotheDAV (Figure km thick,relatively fl westernmost end. The mainbodyoftheplutonis~2 parts oftheintrusion,andbaseisexposed atits at-lying andbecomessteeply ne-grained andthe eld evidence for 20-05-2004, 14:42:41 THE PERIADRIATIC INTRUSION OF VEDRETTE DI RIES - RIESERFERNER (EASTERN ALPS): PETROLOGY, EMPLACEMENT MECHANISMS

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Figure 4 - Contour map of the pluton contact. Modifi ed after Wagner et al., in review.

Figure 5 - N-S cross-section of the pluton. From Rosenberg, in press. Volume n° 2 - from B16 to B33 n° 2 - from Volume

Figure 6 - Foliation trajectories in the Vedrette di Ries.

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Volume n° 2 - from B16 to B33 B17 - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg Figure 7- Ascent andemplacement modelfor the Vedrette diRiespluton,from Wagner etal.,(2003). 20-05-2004, 14:42:45 THE PERIADRIATIC INTRUSION OF VEDRETTE DI RIES - RIESERFERNER (EASTERN ALPS): PETROLOGY, EMPLACEMENT MECHANISMS

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Figure 8 - Distribution of Vedrette di Ries rocks on the QAP Figure 9 - TAS (Total Alkali Silica, Bellieni et al., 1995) classifi cation diagram (taken from Bellieni et al., 1976). classifi cation diagram for rocks from the Vedrette di Ries pluton. Igneous lithologies and fi eld relationships. Vedrette di Ries is a composite pluton, consisting mainly of granodiorite and tonalite, with minor amounts of granite and diorite (Figure 8 and Figure 9).

Three main suites of rocks can be distinguished both in the fi eld and from their geochemical characteristics (Bellieni et al. 1976, Bellieni et al., 1981, Steenken et al., 2000). Following their emplacement order we distinguish a fi rst, coarse-grained suite (Figure 10), characterized by the presence of “book biotite” in piles up to 0.5 cm thick, stubby amphibole, and up to centimetric magmatic garnet (Bellieni et al., 1979, Bassani et al., 1997). Figure 10 - Coarse-grained tonalite with up to centimetric garnet (Grt), stubby amphibole (Hbl), and frequent Mafi c Rocks of this suite are mainly located in the western Microgranular Enclaves (MME) part of the body and discontinuously decorate its northern and, to a lesser extent, southern borders Volume n° 2 - from B16 to B33 n° 2 - from Volume

Figure 11 - Distribution of the various magmatic suites in the Vedrette di Ries Pluton (from Steenken et al. 2000).

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Volume n° 2 - from B16 to B33 B17 - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg (Western Geltal,areaNofRauchkofel, 2500masl). and tonaliteofthesecond,medium-tofi Figure 13-Initialstageofminglingbetween granodiorite the rightsideofReintal). granodiorite (2kmEofPonte Tobel, asmallquarryon enclaves aremoreaboundantintonalitethan generally presentinsmall“fl amphibole, sometimesincoarsecrystals.Biotiteis abundance ofbiotiteandthepresencerare fi contact withthecoarse-grainedsuite,ismedium-to The secondsuite sharp contactsarealsoobserved (Figure12). transitional withlocalevidence ofmixing, although The contactsamongdifferent lithologiesaregenerally the suiteisevidenced bythepresenceofraregarnet. side ofthepluton.Graniteisrareanditsaffi dioritic bodiesarelocatedalongthesouth-eastern diorite togranodiorite,withdominanttonalite.Small (Figure 11). This suite rangesincompositionfrom observed inotherplaces. As arule,mafi granodiorite fromsuite2(left).Transitional contactswere garnet tonalitefromsuite1(right)andmedium-grained Figure 12-Sharpcontactbetween coarse-grained ne-grained andischaracterizedbythe relative , displayingasharptotransitional akes”, althoughsome c microgranular ne-grained suite liation to and interlayering(Figs.14,15). transitional, withevidence ofmingling (Figs.13,14) between tonaliticandgranodioriticrocksismainly to graniteanddonotany containgarnet. The contact Rocks ofthissuiterangeincompositionfromtonalite “book” crystalscanbeobserved inthecontactzones. layering (upperleft)between tonaliteandgranodiorite Figure 14-Mingling(lower partofthepicture)and Figure 15-Interlayeringofmedium-tofi from thesecondsuite(Western Geltal,areaNof granodiorite andtonalite. Rauchkofel, 2500masl). negrained 20-05-2004, 14:42:53 THE PERIADRIATIC INTRUSION OF VEDRETTE DI RIES - RIESERFERNER (EASTERN ALPS): PETROLOGY, EMPLACEMENT MECHANISMS

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Chemical characters of the Vedrette di Ries rocks and genetic hypothesis The intrusive rocks of Vedrette di Ries show a

calcalkaline character. They have invariably low TiO2

content (<0.8 wt%), high Al2O3 and low FeO/MgO ratio. From the geochemical point of view the three suites (Figure 17) can be distinguished based on their Ca, Sr, Rb (Figure 18) contents and trends (Bellieni et al., 1978).

Further investigations pointed out that, based on their REE contents, rocks of Vedrette di Ries can be Figure 16 - Sharp contacts between granodiorite subdivided into two main groups characterized by low and tonalite from the second suite. Dikes of evolved (<1.1) TbN/YbN and high TbN/YbN values (Figure 19). granodiorite magma cut and disrupt the (partially) crystallized tonalite (South of Riesernock, along the According to Bellieni et al. (1981) the rock series Hartdegenweg, 2320m asl). represents the product of a two-stage crystal/liquid Sharp contacts and dikes of granodiorite intruding fractionation starting from one and the same parent and dismembering the tonalite are also observed magma. During a fi rst stage, at high pressure, (Figure16). separation of hornblende + garnet lead to magmas with

high TbN/YbN, representing the ancestor of each suite. The third suite, located in the central-eastern part These magmas, during their rise at lower pressure, of the pluton and mostly surrounded by rocks of underwent a second stage of fractional crystallization the second suite, is medium- to fi ne-grained and with separation of hornblende + plagioclase, and then displays a rather homogeneous leuco-granodioritic evolved towards Sr-poor compositions. Processes of composition. Biotite, in accessory quantities, is contamination with crustal material and separation of the only mafi c mineral, and K-feldspar appears in accessory phases had an important role in determining centimetric individuals. Contacts with rocks of the the high 87Sr/86Sr values and the uneven distribution of previous suite are sharp (Steenken et al., 2000). some trace elements (Bellieni et al., 1981). Volume n° 2 - from B16 to B33 n° 2 - from Volume

Figure 17 - Areal distribution of the three different suites of rocks in Vedrette di Ries as identifi ed by the Ca-Sr and Rb-Sr variation diagrams (taken from Bellieni, 1978).

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Volume n° 2 - from B16 to B33 B17 - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg (Taken fromBellieni,1978). third, central,homogeneousleuco-granodiorite. second, fi garnet bearingsuite.SuiteT*-GD2-G2correspondstothe Suite T3-GD3-G3correspondstothefi curves for each suitetakes placeatdifferent Rb/Srvalues. defi taken asadifferentiation index.Thethreesuitesofrocks the mostmafi host andtheircompositionrefl Mafi Figure 18-Cumulative diagramofRbandSrvs abundance decreaseswiththeincreasingSiO and occasionalinthethirdgranodioriticsuite. Their They areabundant inthefi initial evolution ofthesemagmas,asindicatedbytheirhigh country rocksactuallyplayedanimportantroleinthe in rocksfromthesecondsuite. Assimilation of “surmicaceous” xenoliths areparticularlyabundant areas ofthemagmaticbody. Smallmetamorphic close tothecountryrocks,but alsoinsomecentral Metamorphic xenoliths are thereforegoodstrainmarkers (Figure21). interaction withthehostmagma(Figure20).MME magma whoseoriginalcompositionwas modifi (1989) argued that MMErepresentblobsofmafi geochemical andisotopiccharacters,Bellienietal. the garnet-bearingsuite.Basedontheirpetrographic, hosts. GarnetisrestrictedtoMMEsampledwithin ne different trends.TheintersectionofRbandSr c microgranular enclaves (MME) 87 ne-to medium-grainedsuite.GD1representsthe Sr/ 86 Sr isotopiccompositionandbyitswide c enclaves beingobserved inmostmafi arelocallyabundant notonly rst, coarse-grainedsuite ects thatofthehost, rst, coarse-grained, arecommon. Rb/Sr 2 ofthe ed by ed c c to metric,have anoverall E-Worientation,andoften veins (Figure22). Acidic dikes rangefrom centimetric All suitesarecutbylateacidicandmafi variational range(Borsietal.,1979). (reported asB1,B2,B3).Stars:diorite;circles:tonalite; with highTb the threedistinctgeochemical trendsof Vedrette diRies Figure 19-Two maingroupsofrocks canbeidentifi low (<1.1)Tb in Vedrette diRiesbasedontheirTb rocks withhighTb (Differentiation Index)andCavsSrdiagrams, N triangles: granodiorites;squares:granite. /Yb N /Yb N (fi N lled symbols).IntheSrversus D.I. values(emptysymbols),androcks N /Yb N plotattheoriginofeach of N /Yb: rocks with c dikes and dikes c 20-05-2004, 14:43:00 ed THE PERIADRIATIC INTRUSION OF VEDRETTE DI RIES - RIESERFERNER (EASTERN ALPS): PETROLOGY, EMPLACEMENT MECHANISMS

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Figure 20 - Mafi c microgranular enclave surrounded by a centimetric reaction halo. Volume n° 2 - from B16 to B33 n° 2 - from Volume

Figure 21 - Example of late fl attening on a mafi c microgranular enclave and an aplitic dike.

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Volume n° 2 - from B16 to B33 B17 - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg et al.,2000). Vedrette diRiesyieldsanage of26.3 determinations onalamprophyricdike within and Pennidicunits(Gattoetal.,1976).K-Arage the Austroalpine, but alsotheSouthern Alpine “andesitic” l.s.dike activity thatinterested notonly surrounding basement. They belong toawidespread Mafi calcalkaline magma(Figs.24and25) magma isintrudedanddisruptedbyyounger unpublished degree thesis),wherepristineshoshonitic sometimes even withinthesamedike (Schiavon, calcalkaline andshoshoniticproductsarepresent, trachy-basalt tobasalticandesite(Figure21).Both to decametricandrangeincompositionfrom metamorphic countryrocks. They arecentimetric including apliteandpegmatite dikes, andthe magmatic cycle. They cutboththeplutonicrocks, Mafi host (Figure23). orientation, show sharpcontactswiththeintruded Lamprophyric dikes and evolution of Vedrette diRies. latest magmaticactivity linked totheemplacement may containspessartinegarnet. They representthe dikes aremorecommonthanpegmatitic onesand seldom intrudethemetamorphiccountryrock. Aplitic constitute swarms ofsubparallelindividuals thatonly Figure 22-TAS classifi (Fioretti etal.,unpublished). mafi c dikes within Vedrette diRiesPluton c dikes arecommonlyfoundalsointhe c dikes arenotpartof the Vedrette diRies cation diagramfor acidicand withadominantN-S ± 3 Ma(Steenken an initialratioof0.709.Highervalues oftheinitial for Vedrette diRiesof30 Borsi etal.,(1979)reportedawholerockRb/Srage Geochronology evidence indicatesthat Vedrette diRiesisyounger al., 1979,Cavazzini etal.,unpublisheddata).Field batches ofmagmasandfromsomegranite(Borsiet 87 Figure 23-Mafi Sr/ 86 Sr (uptoca.0.720)wereobtainedfromother Figure 24- Veining ofamafi magma. Thehorizontallinesareglacialstripes. c dike withmagmaticlineationalongthe wall (S-SEofRifugioRoma). ± 3 Maand c dike bymoreevolved 87 Sr/ 86 20-05-2004, 14:43:09 Sr with THE PERIADRIATIC INTRUSION OF VEDRETTE DI RIES - RIESERFERNER (EASTERN ALPS): PETROLOGY, EMPLACEMENT MECHANISMS

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Figure 25 - Pristine magma disrupted by younger calcalkaline magma within the same dike.

than the acidic porphyritic dikes outcropping in the Schulz, 1997); surrounding basement (Cescutti et al., 2003). These 3 - Eo-Alpine metamorphism under relatively high- dikes have been correlated (Cescutti et al., 2003) P/low-T conditions (7.5 ± 1.5 kbar and 450 ± 50 °C, with those outcropping at the Austroalpine-Penninic Stöckhert, 1984, 1987; Prochaska, 1981); limit north of Rensen (Figure 3), dated at 30.9±0.2 4 - “Main-Alpine” (“Tauern”) metamorphism under Ma by Müller et al. (2000). The late lamprophyric lower greenschist facies conditions (Sassi et al., dikes cross-cutting Vedrette di Ries are 26.3±3 Ma 1980); (Steenken et al., 2000). 5 - Oligocene contact metamorphism in the aureole of the Vedrette di Ries pluton (Bianchi, 1934; Prochaska, Metamorphism 1981; Schulz, 1989; Cesare, 1994a, 1999a): the last In the region between the Tauern Window and the metamorphic event recorded in the area. Periadriatic Lineament, the Austroalpine basement of Metamorphism was accompanied by intense the Eastern Aps forms an E-W trending belt, divided deformation during both the eo-Alpine (Stöckhert, into three blocks by two major tectonic lines: the 1987) and the late-Alpine events (Kleinschrodt, Defereggen-Anterselva-Valles (DAV) line and the 1987). Oligo-Miocene dextral and sinistral mylonites Kalkstein-Vallarga (KV) line (Borsi et al. 1978). are widespread throughout the area, pointing to an Unlike the other two blocks, which display an intense coaxial component of deformation in front essentially pre-Alpine tectono-metamorphic history, of the Dolomite indenter (e.g. Müller et al., 2001).

the block north of the DAV line was involved in Discrete mylonite zones of considerable thickness B16 to B33 n° 2 - from Volume the Alpine metamorphic cycle (Borsi et al., 1978): and lateral continuity occur far from (and north of) its polymetamorphic history can be summarized as the DAV line, in addition to numerous smaller and follows: discontinuous ones (Mancktelow et al., 2001). 1 - “Caledonian” metamorphism of undetermined However, parts of the block escaped the Alpine P-T conditions (Borsi et al., 1973; Hammerschmidt, structural reworking (not the metamorphic overprint) 1981) preserving pre-Alpine structures and metamorphic 2 - Variscan high grade metamorphism and anatexis at relict assemblages (Borsi et al., 1978). One of these P = 6±1 kbar and T = 650 °C (Stöckhert, 1985, 1987; areas is located south of the Vedrette di Ries tonalitic

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Volume n° 2 - from B16 to B33 B17 - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg population but alsoprotectedandactively maintained. development. The Park isnotonlyacceptedbythe considerate policy of integration andsustainable native populationfromusingit,but bypursuinga by imposingrestrictionsthateventually prevent the successfull example of protectingawideareanot and was founded13yearsago.Itconstitutesa The Park isthelargest oneinSouthern Tyrol in the“NaturparkRieserferner-Ahrn”. The areawearegoingtovisitiscompletelyenclosed Field tripitinerary represents thesouthernfl W anddipssouth30°to60°;theoverall structure metamorphic layering,isoclinallyfolded,strikes E- and amphibolite. The well-developed Variscan layers ofpegmatite gneiss,marble,quartzite paragneisses aredominant,withminorinterbedded pluton; heremetapeliticschistsandmigmatitic showing theantiformal structureinthecountryrocks. Figure 26-North-southcross-sectionacrossthe Vedrette diRiespluton(fromDalPiaz,1934) 1994a, usingtheHoldaway’s (1971) Al metamorphism isestimatedat2.5-3.75kbar(Cesare, (1991) facies seriesscheme. The pressureofcontact which correspondtotype2biiofPattison & Tracy’s divided byCesare(1992)intofi is approximately1.5kilometreswideandhasbeen The contactaureoleofthe Vedrette diRiestonalite (Figure 26). antiform quasi-concordantwiththeplutonmargin metamorphic grade,closetotheplutoncontact. metamorphism andislocalizedinthezonesofhighest the earliermainfoliation,accompaniedcontact A weakdeformation,occurringasareactivation of point of,withmaximumtemperaturesof600-620°C. ank ofakilometer-sized ve mineralogiczones, 2 SiO 5 triple tonalite quarriesandintroductiontothepetrology a) Riva di Tures valley (Reintal):avisittothe Hütte). (Ursprung) valley –RifugioRoma(Kasseler Taufers) -Riva di Tures (Reinin Taufers) -Sorgiva Brunico (Bruneck)-Campo Tures (Sandin not toleave any majortraceofyourpassage. take somesampleswithyou,wekindlyrequestyou considerate. Whereas youarecertainlyallowed to also gratefullyacknowledged (Figure27).Please,be population fortheirhomeland,andwhichGodis these placestestifi are proudlycultivated andtransmitted. The beautyof home forthepeopleliving here.Culturaltraditions The mountains,woods, water, andgrazingareasare Figure tonalite, Franziskusweg, NaturparkRieserferner-Ahrn. 27 -“MaytheLordbepraised”:carved block of es tothecareandlove ofthelocal DAY 1 20-05-2004, 14:43:15 THE PERIADRIATIC INTRUSION OF VEDRETTE DI RIES - RIESERFERNER (EASTERN ALPS): PETROLOGY, EMPLACEMENT MECHANISMS

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geochemistry of the composite pluton of Vedrette di Ries. b) Sorgiva-Ursprung valley: walk to the northern contact of the pluton. Outcrops of mylonites at the contact and intensely deformed tonalite. Discussion of the structural and chronological relationships between emplacement and ductile deformation, and of the role of the northern mylonite zone. c) A walk along the Hartdegenweg to the Rifugio Roma (2275 m a.s.l.): outcrops of various facies of the tonalite. Strain gradient in the tonalite, mingling and injection relationships between fi ne-grained and coarse-grained facies, aplitic, granitic and lamprophyric dikes cutting the main body. Figure 28 - Subhedral garnet with atoll inclusions (amphibole ± plagioclase ± biotite ± opaque minerals), Stop 1: surrounded by a thin reaction rim. Road between Campo Tures - Riva di Tures (Fig 29). (c. 1150m a.s.l.). Quarries of tonalite along the Rio The compositional range of rims is more scattered, di Riva Valley. Coarse-grained, Grt-bearing tonalite possibly due to different degrees of interaction with and granodiorite. Contact with the medium- to distinct magmas. fi ne-grained granodiorite without garnet. Granite The composition of included minerals shows some and aplitic dikes. Petrogenetic implications of the systematic differences compared to that of the same presence of garnet will be discussed. phases occurring in the rock. While plagioclase in Garnet is one of the main features of the coarse- the rock shows a marked zoning with bytownite core grained suite (Figure 10). In calc-alkaline magmas and up to oligoclase rim, plagioclase within garnet garnet is rare, but not unusual; experimental work by lacks the An-poor external rim, and its intermediate Green (1972) and Green & Ringwood (1972) have zones are very thin. Amphibole in garnet is Fe- demonstrated that it forms at pressure conditions > hornblende and is Al-richer than the Mg-hornblende 10 Kbar. However, the observations that magmatic of the rock. On the other hand, the composition of garnet-bearing rocks in Vedrette di Ries represent a biotite inside garnet and within the rock is almost the sort of belt around the pluton close to the contact with same. Petrographic and minero-chemical characters the metamorphic country rocks, and that all along fi t the hypothesis that minerals in inclusions formed the contacts magmatic rocks contain metamorphic by crystallization of portions of the magmatic xenoliths with abundant garnet, suggested that liquid trapped in garnet during its crystallization garnet in the Vedrette di Ries plutonic rocks might (Figure 30). The composition of minerals in the exclusively be linked to the assimilation of country reaction rim is rather homogeneous. Plagioclase is rocks. This problem was addressed by Bellieni et oligoclase, and amphibole composition straddles the al. (1979) and recently reconsidered by Bassani (unpublished degree thesis, 1996). Garnet in Vedrette di Ries tonalite and granodiorite is up to 2 cm wide and is generally idiomorphic. It is typically surrounded, and sometimes totally replaced, by a reaction rim made up of fi ne-grained plagioclase ± biotite ± quartz (± amphibole) (Figure 28). Volume n° 2 - from B16 to B33 n° 2 - from Volume Preserved individuals show concentric shells of Pl ± Qtz ± Bt ± Hbl inclusions, likely representing samples of the coexistent crystallizing magma. Garnet is zoned with a wide, rather homogeneous, nucleus of almandine composition (Alm 50-70%, Sps 2-10%) and a narrow more spessartine-rich rim (Alm 35- Figure 30 - Inclusion in garnet. The shape of the 40%, Sps 12-15%). The core composition of garnet inclusion, a negative garnet crystal, and the composition is independent from the rock, i.e. core composition of of the mineral phases suggest that included minerals garnet in diorite, tonalite and granodiorite is the same crystallized from a portion of trapped magmatic liquid.

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Volume n° 2 - from B16 to B33 B17 - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg substitution oftheoriginalgarnet. the reactionborderrangesfromathinrimtocomplete Figure 31-Reactionborderaroundgarnet.Thewidth of constant spessartinecontents. metamorphic rock (diamonds)andfromaplite(star).Magmaticcoresdefi Figure 29-Compositionofgarnetcorefromtonaliteandgranodiorite(fullsquarescircles),thecountry of themagmatowards shallower crustallevels (ca. is presumablylinked toarelatively rapiduprising marked plagioclasezoning(Bellienietal.,1976), The instabilityofthegarnet,accompainedbya (Figure 31). as suggestedbythepresenceofareactionborder instability conditionsonlyduringalaterstage, on relicsduringmagmaticcrystallization,andreached of approximately5%.Garneteitherformedorgrew with liquidusatP>10Kb, T<950°C andwater content et al.(1979)estimatedthatgarnetwas inequilibrium Taking intoconsiderationthegarnetcores,Bellieni fi elds ofFe-hornblendeandMg-Hornblende. ne anellipticalcoherentfi eld withrather 20-05-2004, 14:48:40 THE PERIADRIATIC INTRUSION OF VEDRETTE DI RIES - RIESERFERNER (EASTERN ALPS): PETROLOGY, EMPLACEMENT MECHANISMS

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2 Kb), where the magma eventually emplaced. An crystallization was proposed for these dikes (Cescutti identical conclusion was independently reached by et al., 2003). studying the crystallization of the cotectic minimum of the granitic rocks (Bellieni, 1977). Contact mineral Stop 4: assemblage of the country rocks (Bellieni, 1977; Path 8a to Rifugio Roma, 2320m a.s.l. The well- Cesare, 1992) further confi rms the fi nal emplacement exposed northern contact of the pluton. level of the Vedrette di Ries magma. Mylonitic paragneisses with transposed tonalitic dikes. The country rocks in this area are largely made Stop 2: of mylonitic paragneisses, containing numerous veins Path 8c, 1735m a.s.l.. Foliated, coarse-grained and apophyses of coarse-grained tonalite, transposed tonalite just before the bridge over Rio di Riva. and boudinaged within the foliation (Figure 32, see Foliations dip to the N-NW of 50-60°. also Steenken, 2002). In the paragneisses, biotite and fi brolitic sillimanite occur in the synkinematic Stop 3: assemblage. As sillimanite occurs in this area only as Path 8c from Riva di Tures (Loc. Säge) to a product of contact metamorphism, we can conclude Ursprungalm, along the river, 1850m a.s.l.. Strongly foliated country rocks at the northern intrusive contact. The mylonitic paragneisses contain both layer-parallel and discordant dikes and apophyses of coarse-grained tonalite. These relationships suggest that mylonitic deformation was active in this area during the initial stages of pluton emplacement, and that it stopped before the fi nal stages of emplacement.

Along path 8c to Ursprungalm several aspects and phenomena deserve consideration: 4) at 1900m a.s.l: paragneisses with transposed Figure 32 - Small tonalitic dike transposed in the foliation tonalite injections along mylonitic foliation; of country rock paragneisses. In the paragneiss, the 5) from 1900m to 2100m a.s.l: the path climbs up to foliation is outlined by synkinematic sillimanite (fi brolite). the north of a hill mostly made of amphibolites; 6) at 2290m a.s.l: the amphibolites and paragneisses are crosscut by a porphyritic dike (Cescutti et al., 2003). The dike is c. 3 m thick, and is strongly sheared within the dominant mylonitic foliation. This kind of dikes, of granitic composition, never crosscuts the Vedrette di Ries plutonic rocks, and is therefore older. Similar rocks, named “porphyritic tonalites” have been dated at 30.9±0.2 Ma by Müller et al. (2000). The mineral assemblage of this kind of dikes is plagioclase, quartz, K-feldspar, muscovite, and biotite. Garnet, allanite, apatite, opaque minerals and zircon are present in accessory quantities. Figure 33 - Boudinage of a dm-thick amphibolite layer B16 to B33 n° 2 - from Volume Based on petrographic evidence (garnet composition at the northern intrusive contact of the Vedrette di Ries and zoning, its presence inside the core of zoned tonalite, in the upper Val Sorgiva. plagioclase, overgrowth of new garnet around individuals not included in plagioclase, partial that the mylonitic foliation developed during contact resorption and subsequent crystallization of new metamorphism, i.e., that it was synchronous with plagioclase), and their chemical signature, a genesis pluton emplacement. by partial melting of deep crustal material and an Amphibolites, metacarbonates and calc-silicate rocks emplacement at shallow levels following a polybaric at the immediate contact. As also observed in the

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Volume n° 2 - from B16 to B33 B17 - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg the pluton’s interior(Wagner etal.,inreview). enclaves of~10:1rapidlydecrease to~3:1towards from themagmatictosolidstate. Aspect ratiosof found locally, suggestingacontinuous deformation deformation. However, melt-bearingshearbandsare fabrics areentirelyoverprinted bygreenschistfacies subhorizontal stretchinglineations.Magmatic shearing alongasteep,E-Wstrikingzone,displaying the entireplutonanditischaracterisedbysinistral solid state. This arearecordsthelargest strainof of thetonalite,andhencetodeformationin paragneisses pointstoamorecompetentbehaviour Boudinage oftonalitewithintheenclosing layers (Figure33). beautiful examples ofboudinageintheamphibolite deformation canbeobserved alsointheserocks,with grain-size. As inthemetapeliticmylonites,astrong and clinopyroxene, andmaydevelop avery coarse calc-silicate rocks. The lattercontaingarnet,epidote grained, biotite-bearingamphibolites,marblesand contact ofthetonaliteareoftencomposedfi lower Val Sorgiva, countryrocksattheimmediate characterized bythepresenceofmarblesandcalc- Again, thecountryrocksatcontactare grained tonaliteatthenorthern contact. metre-sized zoneofminglingcoarse-andfi Path 8toRifugioRoma,c.2400ma.s.l. A ten- Stop 5: Figure 34-Remnantsofthepluton’s roof(darker colour)ontopoftheSpronedelle Vedrette Giganti. ne- ne- some garnethere. silicate rocks. The coarse-grained tonalitecontains the Austroalpine basement;synintrusive deformation contact betweenthetonaliteandmetapelitesof at thefrontofMonteNevoso Glacier:intrusive intrusion of Vedrette diRies.Ice-polishedoutcrops Aplitic andlamprophyricdikes post-datingthemain Rifugio Romaandsurroundings. metamorphism (Cesare,1992,1994a). helping constraintheP-Tconditionsofcontact sillimanite” zone)hasbeenobserved inparagneisses, metamorphic assemblageMs-Kfs-Qtz-Sil(or“second only locationwherethedivariant KNASH contact delle Vedrette Giganti(Riesernock). That isthe of thepluton’s roof(Figure34)ontopofSprone eastern sectorofthemassif,withlarge remnants From theRifugio,apanoramicview towards the foliation isdiscordanttothewall ofthedikes. the alreadycrystallizedtonalite(seeFigure16). The Dikes ofevolved granodioritemagmacutanddisrupt and granodiorite. contacts betweenmedium-tofi Path 8toRifugioRoma,c.2320masl.Sharp Stop 6: DAY 2 ne-grained tonalite 20-05-2004, 14:48:48 THE PERIADRIATIC INTRUSION OF VEDRETTE DI RIES - RIESERFERNER (EASTERN ALPS): PETROLOGY, EMPLACEMENT MECHANISMS

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Stop 2: Ice-polished rocks at the base of the Tristenferner glacier, c. 1800 m south of Rifugio Roma, 2550 m a.s.l.. Here is one of the best exposures of the intrusive contact between underlying fi ne-grained tonalite and overlying metapelitic country rocks, thoroughly affected by contact metamorphism and synintrusive deformation. Rather than a sharp surface, the contact is an intrusion/interaction zone of some tens of metres in thickness, where several layer-parallel tonalite injections are observed. Overall, the contact is generally concordant with the country rocks’ Figure 35 - Replacement of andalusite by coarse-grained, foliation, and dips c. 30° to the north. This area can be prograde muscovite. Sillimanite (fi brolite) is the stable considered a part of the pluton’s roof. Al SiO polymorph, and occurs in the matrix 2 5 The country rocks are mostly migmatitic paragneisses around the nodular pseudomorph. (Hofmann et al., 1983) characterized by a Qtz-Pl-Ms- Bt-And-Sil-St-Spl-graphite assemblage. Although easily recognized in the hand specimen, staurolite and andalusite are metastable relicts of lower-grade contact metamorphism, and are transformed into

Figure 36 - The reaction of staurolite to hercynite accompanies the topotactic replacement of andalusite by sillimanite in the metapelites at Stop 2. Taken from Cesare (1994a).

and contact metamorphism of the country rocks; oligocene Grt-Ms-Tur-Ber-bearing pegmatites. Figure 37 - Contact metamorphic prismatic sillimanite bent and wrapped by fi brolite-bearing foliation. Stop 1: Swarm of mafi c, lamprophyric dikes with a general N-S direction. Sharp, brittle contacts, intrusion of thin lamprophyre apophyses along fracture zones, and presence of angular granodioritic xenoliths within the dikes testify for their late emplacement. Chilled

margin and magmatic foliation are well developed in B16 to B33 n° 2 - from Volume wider dikes (Figure 23). Subsequent intrusions along the same feeder are testifi ed by network of less mafi c veins (Figure 24) that eventually lead to the disruption of the already solidifi ed mafi c magma (Figure 25). Spherical to ameboid geodes of acicular amphibole in a medium grained matrix within the mafi c dikes suggest a crystallization at high P . H2O Figure 38 - Tourmaline and garnet in the pegmatites of likely Oligocene age.

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Volume n° 2 - from B16 to B33 B17 - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg hercynitic spinelas: formulated thedecompositionofstauroliteto In theabove microstructures,Cesare (1994a)has and hercynite (Figure36). muscovite (Figure35),topotacticprismaticsillimanite nodular pseudomorphsconsistingofcoarse-grained the rock layersstudiedandrespective samplenumbers.MineralzonesasinTable 1(inset). Figure 39-Simplifi structural featuressuggestthattheserockspost-date observe thepegmatites whichintrudethetonalites, this outcrop. Although inthislocationonecannot are somemeter-thick discordantdikes whichoccurin are likely toberelatedthe Vedrette diRiesintrusion inpegmatitic rocks. Among the few pegmatites which The Vedrette diRiesplutonistypicallypoor contact metamorphism. rocks developed, orwas reactivated, duringthe (Figure 37). Therefore, thefoliationofcountry to have beenbentandwrappedbythefoliation sillimanite. Inaddition,prismaticsillimaniteappears foliation oftheparagneissesisoutlinedbyfi Like intheupper Val Sorgiva, thewell-developed metamorphism at2.5-3.75kbarand585-655°C. and hasconstrainedtheP-Tconditionsofcontact Fe-St = 3.85Her+5.1Sil2.55Qtz2H ed geologicalmap(afterMager, 1985)ofthesouthernaureole Vedrette diRies,withlocationof brolitic 2 O Anterselva. Afternoon: descenttoRiva di Tures andtripto undergoing adramaticretreat(Santillietal.,2002). lakes. The glaciersofthe Vedrette diRiesmassifare terminal morains,ice-polishedrocksandsmallglacial little iceage(1450-1850),suchashugelateraland observation ofthegeomorphological effects ofthe This areaisalsoparticularlyinterestingforthe abundant chloriteandepidote. low-temperature alteration,withdevelopment of also shows widespreadcataclasticdeformationand oriented, withelongatedmicrogranularenclaves. It The fi green berylhasalsobeendiscovered here. muscovite, garnetandtourmaline(Figure38).Light quartz andfeldspars,thesepegmatites containbiotite, to thefoliationofhostparagneisses. Along with a setofparallelinjectionsathighanglecompared contact metamorphism.Infact, thepegmatites form ne-grained underlyingtonaliteisstrongly 20-05-2004, 14:45:54 THE PERIADRIATIC INTRUSION OF VEDRETTE DI RIES - RIESERFERNER (EASTERN ALPS): PETROLOGY, EMPLACEMENT MECHANISMS

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Figure 40 - Hand specimen of a graphitic schist Figure 41 - Metapelitic schist from upper Zone 3. from lower Zone 3, with abundant coarse-grained The light brown to orange nodules are polycrystalline andalusite porphyroblasts. aggregates of staurolite. See Figure 42 for a microscopic view of an aggregate from this rock.

DAY 3 affected by the Oligocene contact metamorphism. We will focus our attention on the effects of contact Rifugio Forcella Valfredda (Rieserfernerhütte) metamorphism on metapelitic lithologies. and surroundings. The southern contact aureole of Vedrete di Ries has been divided into fi ve mineralogical zones (Table Contact metamorphism and related phenomena in 1, Figure 39, Cesare 1992) which developed at c. 3 the southern aureole of Vedrette di Ries. Profi le kbar. In the metapelites, the most evident minerals of the outer, regionally metamorphosed (Variscan of contact metamorphic origin are the abundant and Alpine) metapelites up to the intrusive contact; and very coarse andalusite (up to 10 cm in length, observation of the well-developed St-And-Sil Figure 40), and the unusually fi ne-grained staurolite, zoneography; discussion of thermobarometric which often occurs in polycrystalline nodules constraints to depth of emplacement. The Andalusite- (Figure 41). bearing veins and their fl uid inclusions: a marker of fl uid-rock interactions during contact metamorphism. Another peculiarity of this area is that layers of a distinctive rock type crop out in at least four localities, Participants will walk along a S-N oriented profi le at variable distance from the intrusive contact (Figure covering the whole contact aureole up to the intrusive 39). These rocks allow for reconstruction of the contact with the fi ne-grained tonalite. We are not multi-stage pseudomorphic replacement of a primary dividing the day into stops, as there would be too garnet: here follows a summary of the microstructural many. However, we will refer to the maps provided study and of the main conclusions outlined by Cesare herewith. Here follow the detailed descriptions of (1999a, b), where further details and an updated the two main objects of this part of the fi eld trip: the reference list can be found. The layers have a thickness contact metamorphism and its zoneography and the of < 20 m, and consist of fi ne-grained mica-schists andalusite-bearing veins. with a marked millimetric compositional layering, with abundant quartz-rich ribbons, probably the result Contact Metamorphism at Vedrette di Ries of mylonitic deformation. The foliation wraps around

The area of Rifugio Forcella Valfredda is the ideal B16 to B33 n° 2 - from Volume lensoid domains in which garnet, kyanite, staurolite, place to observe the effects of contact metamorphism andalusite and muscovite are dominant in turns. The induced by the tonalite of Vedrette di Ries. The systematic distribution of Al SiO polymorphs in southern aureole is mainly composed of metapelites, 2 5 the aureole, and the resulting isograd pattern (Figure but orthogneisses, quartzites, amphibolites and 39), indicate that during the contact metamorphic marbles also occur. As previously stated, these rocks event only the layer closest to the contact (i.e. sample belong to the Austroalpine basement to the north VR466) reached temperatures suffi cient for the of the DAV line, and have undergone a complex crystallization of sillimanite. It follows that in all the and polyphase metamorphic evolution before being other layers any occurrence of sillimanite is attributed

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Volume n° 2 - from B16 to B33 B17 - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg Sample description evolution ofthisarea. transformed duringthecomplex metamorphic primary rocktype(thesamefoldedlayer?),variably composition ateachlocality, mayrepresent thesame rocks, althoughshowing different mineralogical microstructural characteristicssuggestthatthese VR491 analysis. SeeFigure39fortheirlocations. microstructural, bulk chemical,andmineralchemical of therocktypeateachlocation,andusedfor Four sampleshave beenchosenasrepresentative to earliermetamorphism.Bothfi monomineralic aggregateofmuscovite wrappedbyfolia ofbiotiteandfi This suggestsreactivationofthemainfoliation duringcontactmetamorphism.PL, wv=6.5mm.h: VR466. Decussate the sericitematrix.Sericitearoundnodule(lower right)shows preferred orientationwithincipientshearbandcleavage. sericite aggregate(ser).Note(arrows) thecoarsergrain-sizeofstauroliteonperipheryaggregate,orisolatedin of moststaurolitecrystals(stars).Crossedpolars(CP),wv=6.5mm.g: VR480. Monomineralicnoduleofstauroliteina polarized light(PL),widthofview(wv)=6.5mm.f: VR496. Noduleofkyaniteandstaurolite.Kyanite occursatthecore biotite, ilmeniteandgarnet.Two kyanite-rich asymmetrictails(arrows) extendinthesubhorizontalmainfoliation. Plane- Figure 42-Close-upviewsofnodulesfromeach sample.e: VR491. Roundaggregateofmicrogranularkyanitewithminor as isolatedporphyroblasts,orassociatedwithkyanite typically <5mmindiametre.Garnetispresent,either schist, withabundant nodularaggregates ofkyanite, intrusive contact.Itisasilvery, muscovite-rich metamorphism. The samplefurthestfromthe : fromZone1(chlorite-biotite)ofcontact eld appearanceand VR496 in theaggregates. biotite-rich matrixthatformslayersalternatingwith This massive rockisalmostblack,owing tothe location isvery close (approx 50m)tothepluton. VR466 in thickness. staurolite. Quartzribbonsandrodsmayreachonecm mica-rich layersthatcontainbiotite,muscovite and Coarse porphyroblastsofandalusiteoccurinthe microgranular stauroliteupto1cmindiametre. rock, withorange-brown nodulescomposedof VR480 in themuscovite-rich layersofthematrix. garnet. Andalusite crystals,upto3cminlength,occur brown sturolite.Stauroliteoftenformscoronasaround in garnetporphyroblastsandnodulesoffi Light gray, stronglylayeredbut massive schist,rich brolite. PL,wv=6.5mm. : fromZone4(sillimanite-garnet). The sample : fromtheinnerZone2. A dark-brown : fromtheouterZone2(andalusite-staurolite). ne-grained, 20-05-2004, 14:46:27 THE PERIADRIATIC INTRUSION OF VEDRETTE DI RIES - RIESERFERNER (EASTERN ALPS): PETROLOGY, EMPLACEMENT MECHANISMS

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quartz ribbons and fi brolite-rich folia. Pink andalusite agreement with the presence, in sample VR491, of porphyroblasts are abundant, whereas the scarce untransformed garnet crystals adjacent to partially or muscovite is mainly concentrated within mm-sized completely pseudomorphed ones. nodules. The Kyanite Stage (VR491, VR496) - This is Figure 42 compares the general textural appearance represented by the nodules of microgranular kyanite of the four samples at the thin section scale. The which maintain their primary shape of garnet, but are most striking similarities are the presence of nodular not thought to have replaced it directly. The very fi ne aggregates of comparable size, wrapped around by grain-size of kyanite in the nodules is an anomalous the matrix, and the occurrence of quartz-rich ribbons. feature for metapelites; this peculiarity, and its In addition, all rock samples are graphitic, and contain possible cause, is discussed below. tourmaline crystals with similar, complex zoning. A As it is not clear whether sericite pre-dates kyanite progressive grain-size coarsening of matrix phases or is coeval with it, the possibility of a further (e.g. biotite and muscovite), aggregate phases (e.g. stage pre-dating the Kyanite stage, and represented staurolite), as well as nodular aggregates themselves, by sericite crystallization (the Sericite stage), has can be observed, even in hand specimens, in the to be considered. Sericite would form “shimmer transition from sample VR491 to sample VR 466. aggregates” upon replacing fi brolite, and leave relict This is consistent with the higher temperatures and needles within quartz and muscovite adjacent to the longer duration of contact metamorphism in the nodules. samples closer to the pluton. The Staurolite Stage (VR491, VR496, VR480) - This stage, initiated in sample VR491 and completed in A model for the evolution of a primary garnet site sample VR480, produces the nodules of microgranular The above microstructural information allow for staurolite. Microstructures indicate that staurolite reconstruction of the complex textural evolution of a crystallization is coeval with that of andalusite, or that primary garnet site, now represented by the nodules. it commenced slightly before, and continued during, Preservation of the subspherical shape of garnet was andalusite growth. As a consequence, the staurolite favoured by the very low strain experienced by these stage is related to the contact metamorphism. rocks after garnet crystallization, which resulted in The Muscovite Stage (VR466) - This is the fi nal the static growth of minerals in all the subsequent stage, in which decussate aggregates of muscovite metamorphic events. The textural sequence can be replace staurolite. Although this kind of pseudomorph divided into fi ve (or six) stages: is common during retrograde metamorphism, even in The Garnet Stage (VR491, VR496) - This is the earliest this area, in this sample it has been shown to represent microstructural stage, with garnet porphyroblasts of a prograde feature. Similar prograde pseudomorphs < 1 cm diameter wrapped by the micaceous layers. of muscovite after staurolite were fi rst described by Inclusions in garnet consist of quartz, biotite, ilmenite Guidotti (1968) in a regional metamorphic context. and muscovite, and provide no information regarding The inferred age of the stages can be summarized as the metamorphic history of the metapelite prior its follows: crystallization. The Fibrolite Stage (VR491, VR496) - Although there Stage Age Setting is no direct evidence for a stage where nodules were Grt Variscan Regional composed of fi brolite, several indications point to this Fib Variscan Regional occurrence. They include: i) the presence of fi brolite Ser Variscan? Eo-Alpine? Regional in close association with the nodules, formerly Ky Eo-Alpine Regional occupied by garnet; ii) the radiating arrangement St Oligocene Contact of needles, diverging from the nodule; iii) the Ms Oligocene Contact B16 to B33 n° 2 - from Volume presence of biotite with exsolution of ilmenite and iv) the proposed crystallization sequence, in which Andalusite-bearing veins at Vedrette di Ries fi brolite predates kyanite. These data are suggestive Schists outcropping in the southern aureole of of the high-T reaction of garnet to fi brolite + Ti-rich the Vedrette di Ries pluton contain several vein biotite. Thermodynamic modelling of this reaction generations distinguished by their mineralogical predicts a complex behaviour for garnet, which then composition. The following discussion considers may dissolve, grow or not react at all depending only those veins which are discordant compared to on the local confi guration of the matrix. This is in the pervasive regional foliation, indicating that they

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Volume n° 2 - from B16 to B33 B17 - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg 800 mfromtheintrusion;Site2,ingarnet-fi (Figure 45).Site1isinthestaurolite-andalusitezone, Valfredda werechosen forfurtherinvestigation Two siteswithabundant veins intheareaofForcella crystallization withinfl shape ofandalusitecrystals(Figure44)indicate The fi during orafterthevein formation. that majorductiledeformationdidnotaffect thearea south-dipping foliation,andarenotfolded,implying 5cm. From Cesare(1994b). zoning withFe-enriched darker areas.Baseofphoto: cluster atthestraightvein wall; theyexhibitconcentric from Site2,showing euhedralandalusitecrystalswhich Figure 44-Polished surfaceofanandalusite-quartzvein (Figure 43). They areorientedatahighangletothe fractures, generallystraightandinparallelsets tonalite. The veins arethin,parallel-sided,fi bearing veins, whichoccurupto1kmfromthe deformation. Among thesearesomeandalusite- are youngerthan(orcontemporaneouswith) Alpine The vein isvery thinanddiscontinuous. Figure 43- Andalusite-quartz vein atSite1. ne-grained pegmatitic structureandtheeuhedral uid-fi lled fi ssures. brolite lled At Site1 volumetric ratioisextremely low. single, thinveinlets. Therefore, thevein/host-rock vein occurrencesreportedinFigure45consistof and andalusitepresencewithinschists.Mostofthe the area,andrelationshipbetweenvein occurrence distribution ofthedifferent Al zone, isclosertothepluton.Figure45shows the host-rocks. the abundance ofgarnetintheimmediatelyadjacent which mayreachupto30%,isdirectlycorrelated and rareplagioclaseand/orwhitemica.Biotite, andalusite inequalamounts,withvariable biotite, no longerthan1metre. They containquartz and Andalusite veins arevery thin,usually<1cmand subhorizontal stretchinglineation. foliation dippingsouthandawell-developed E-W chlorite). They preserve theolderpenetrative planar staurolite, biotite,ilmeniteandgraphite(±garnet ± schists containingquartz,plagioclase,andalusite, Figure 45-Occurrencesofandalusite-bearingveins and distribution ofthe Al , host-rocksarepelitichornfelsesand Vedrette diRiesaureole. After Cesare(1994b). 2 SiO 5 polymorphsinthesouthern 2 SiO 5 polymorphs in 20-05-2004, 14:51:25 THE PERIADRIATIC INTRUSION OF VEDRETTE DI RIES - RIESERFERNER (EASTERN ALPS): PETROLOGY, EMPLACEMENT MECHANISMS

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At Site 2, the country-rocks are pelitic hornfelses, the central portion of the veins, alone or associated composed of quartz, plagioclase, biotite, muscovite, with andalusite. acicular and prismatic sillimanite, garnet, ilmenite The veins show a mineralogical zoning with and graphite, with abundant relicts of andalusite. andalusite and biotite abundant at the vein borders, Veins are larger and more abundant, and may in some whereas quartz is dominant at the centre. cases reach a few metres in length and up to fi ve cm All of the andalusite-bearing veins occur within those in thickness. parts of the aureole in which andalusite crystallized Veins are discordant, their direction being quite during contact metamorphism (cf. Figure 45), and are random, but always very steep. There are two end- always hosted by andalusite-bearing rocks. Where member types of andalusite-bearing pegmatitic veins veins occur in non-pelitic lithologies (e.g., pegmatitic at outcrop 2: biotite-absent, quartz-rich veins (the gneiss or quartzite), they do not contain andalusite or larger ones, Figure 44), and biotite-rich, quartz-poor biotite. In the few cases where veins crosscut different veins. In the fi rst type, euhedral andalusite crystals lithologes, there is a different mineral assemblage generally project from the vein walls into the quartz- in each part. The general relationships between rich inner zone as isolated prisms (up to 3 cm in the mineralogy of veins and that of host-rocks are length) or rosette aggregates. The second type occurs outlined in Figure 46. within garnet-bearing host-rocks; coarse-grained biotite is located at the vein walls, but also occurs in The orientation of veins can be consistently related Volume n° 2 - from B16 to B33 n° 2 - from Volume

Figure 46 - Schematic diagram summarizing meso- and microstructural observations on the andalusite-bearing veins of the Vedrette di Ries aureole. Veins that formed in a layered rock (upper left) comprising metapelites and quartzite display a variable mineralogy, depending on the composition of the adjacent host-rock. A, B and C represent observed mineral composition and texture of veins in three end-member host-rock lithologies, respectively garnet-poor pelite, garnet-rich pelite, and quartzite. From Cesare (1994b).

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Volume n° 2 - from B16 to B33 B17 - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg opening, migrationofmatter, andprecipitationof summarized. Itaccountsfortheprocessesoffracture (Cesare, 1994b;Cesareetal.,2001)ishere data, amechanismofsynmetamorphicveining Based onfi quartz andandalusite. the degree ofstrain andoftherelative abundance of are variously recordedineachsample asafunctionof aluminum transport.Intheinclusions,densitychanges fl indicates thatincreasedsolubilityin‘aggressive’ minerals. The low salinityoftheaqueousfraction lithostatic fl P-T conditionsofveining, andwitharegime of H fl these “primary”inclusionsareconsistentwithaC-O- high CO H inclusions defi vein formationarethoseoccurringintheisolatedfl Their resultssuggestthatthefl and Hollister(1995). bearing veins (Figure47)have beenstudiedbyCesare The fl principal stressintheschists. pluton, whichdefi 1 areconcordantwiththemarked elongationofthe σ the underlyingtonalite,whichgives asubvertical to thestressfi from within Andalusite-bearing veins. Figure 47-Primaryfl uids (e.g.Kerrick, 1990)isnotrequiredforeffective 1 2 O-CO . Inparticular, theN-Svein directionsatoutcrop uid inequilibrium withgraphiteattheestimated uid inclusionswithinquartzof Andalusite- 2 2 /CH -CH uid pressureduringcrystallizationofvein eld, microstructuralandfl 4 4 eld generatedbytheemplacementof ned as Type A. These arewater-rich ratio. The compositionanddensityof -NaCl mixtures,withlow salinityand nestheE-Wdirectionofminimum uid inclusionsinquartzcrystals uids presentduring ud inclusion uid uid and thelackofinterconnectedvein networks are thin, andalusite-bearingveins inthestudiedaureole, permanent fl will beattainedandinhibitpressuregradients mechanical stabilitybetweenfractureandhost-rock Vein Opening: Timing, Mechanisms,andFluid bearing veins. minerals duringtheformationof Andalusite- initial fl Grt +ChlMs= And +Bt+QtzH the reaction textural observation ofbiotitepseudomorpinggarnet, formation. Combiningtheabove data withthe were undergoing dehydrationduringandalusite aureole, isclearevidence thathost-rockmetapelites proceeding upgradewithintheandalusitezoneof in modalchloriteandwhitemica,whichisrecorded release duringdevolatilization reactions.Decrease of vein openingwas hydrofracturing,causedbyfl minimal, itcanbeconcludedthatthemainmechanism Since thetypicalfeaturesofshearfracturingare to thestressfi is consistentwiththeorientationofveins compared In theexample studied,thehydrofracturingmodel rock ( of minimumstress( fi immediately drive fl become asourceforlocalpressuregradientswhich and aconsequentdropinporepressure.Fractures increase inthevolume available forthefl Opening offi mineral assemblage. in thehornfelsescapableofproducingvein can beproposedasoneplausibledehydration reaction pressure inthevein must beequalto occurs whenthefl stress, andgeneratesfracturesperpendicularto requires elevated fl Hydraulic extension fracturing(hydrofracturing) at thetimeofvein formation. metamorphic reactionstakingplaceinthehost-rock was synmetamorphic:itwas synchronouswith coeval. Hence,mineralprecipitationinveins growth ofandalusiteinveins andhost-rockswas schists wereundergoing furtherheating.Furthermore, of andalusite(T=500±50°C,Cesare,1992),and the P-Tconditionswerewithinstabilityfi before thecrystallizationofsillimanite. At thattime Veins formedduringthecontactmetamorphicevent, Behaviour lling them.However, tokeep avein open,fl τ 0 ud fl uid ), accordingtothefailure condition: ow. Frequentoccurrencesof isolated, ssures intherockgeneratesasudden ow toward thecavity, aconditionof eld inducedbytheunderlyingtonalite. uid pressure(P uid pressuresandlow deviatoric P σ f uids intotheopencavities,

3 ≥ ) andtensilestrengthofthe

σ 3

+ τ 0. f ), exceeds thesum σ 2 O (1) 3 : afterarapid uid phase, uid 20-05-2004, 14:47:00 σ 3 uid uid eld . It THE PERIADRIATIC INTRUSION OF VEDRETTE DI RIES - RIESERFERNER (EASTERN ALPS): PETROLOGY, EMPLACEMENT MECHANISMS

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additional observations against large-scale fl uid and low-temperature deformation of the tonalite, and circulation. its relationships to the DAV mylonites. In this area Mass transfer and mineral deposition the southern contact of the pluton dips steeply to After the initial, transient fl ow, fl uid can be considered the south, concordantly to the mylonites of the DAV. as virtually stagnant, acting as a passive medium, No kinematic indicators have been found within the in thermal and mechanical equilibrium with the tonalite, but preserved magmatic foliations parallel to surrounding rocks. Moreover, chemical equilibrium the mylonitic foliation of the DAV call for syntectonic can also be assumed, given present theoretical models intrusion. This part of the pluton is inferred to be the and the equal parageneses and mineral chemistry in feeder of the main body located further to the north. vein and host-rock. It follows that crystallization of This conclusion is based on the occurrence of a steep vein minerals was simply controlled by heterogeneous magmatic foliation associated with steep lineations mineral reactions in the host-rock (e.g. reaction 1). (Steenken et al., 2000; Wagner et al., in review). The Nucleation of product phases (andalusite, biotite location of the feeders of the intrusive bodies along and quartz) is favoured on the strained minerals segments of the Periadriatic Lineament is a common at vein walls; once nuclei form, concentration and feature of the Periadriatic plutons. chemical potential gradients between reactants and Discussion of the emplacement mechanisms within products are established, and the transfer of chemical the framework of the Oligocene tectonics of the components, continuously provided by dissolving Eastern Alps. reactants, is activated. This implies synchronous growth of andalusite in vein and host-rock. Mass DAY 5 transfer from adjacent host-rock to the vein occurs Return to Florence - End of Field Trip. via intercrystalline diffusion, which can be very effective, and dominant during metamorphism. Since the fracture is fi lled with fl uid that allows for faster Acknowledgments diffusion, the growth of vein minerals is also faster Financial support was received from CARG-PAB, and grain-size coarser; this explains the pegmatitic the Province of Bolzano, from CNR-IGG, from the vein texture. University of Padova and from DFG (Project Ha Because intergranular diffusion is the mass- 2403/3-2). We wish to thank Gottfried Leitgeb (Rif. transfer process during synmetamorphic veining, Forcella Valfredda), Arnold Seeber (Rif. Roma) and diffusion halos around veins can be expected. The Maria Mair (Geltalalm) for their assistance during plagioclase-rich border zones that sometimes occur fi eld work. The critical reading of Giuliano Bellieni is at vein margins can be interpreted as diffusion halos. gratefully acknowledged. Conversely, such an explanation is not applicable to the biotite-rich zones, which are located within the veins, and cannot be interpreted as residual portions References of metasomatically-depleted country rocks. Bassani S., Fioretti A.M., Bellieni G. (1997). Il granato nelle masse intrusive di Rensen, DAY 4 Vedrette di Ries e Polland (Alpi Orientali). Anterselva (Antholz) valley - Passo Stalle Plinius n.18; 43-44. (Staller Sattel) - Brunico (Bruneck). Bellieni G. (1977). Caratteri geobarometrici delle intrusioni granitiche del plutone delle Vedrette Morning: descent to Anterselva. Outcrops of di Ries (Rieserferner)(Alto Adige Orientale) tonalite at Cima di Vila (Zinsnock): discussion of its alla luce dei sistemi sperimentali Q-Or-Ab-An- geochemical and petrologic features (Bellieni, 1980; H2O. Rend. Soc. It. Miner. Petr., 33, 631-645. B16 to B33 n° 2 - from Volume Bellieni et al. 1982) and of the genetic relationships Bellieni G. (1978) Caratteri geochimici del massiccio with the Vedrette di Ries Pluton. granodioritico-tonalitico delle Vedrette di Ries Afternoon: Drive to Passo Stalle (Staller Sattel) (Rieserferner)-Alto Adige Orientale. Rend. Soc. (2000 m asl): cross sections along the cataclasites It. Miner. Petr., 34, 527-548. and mylonites of the Defereggen-Anterselva-Valles Bellieni G. (1980) The Cima di Vila (Zinsnock) (DAV) line from the pass to the Vedrette di Ries Massif: Geochemical features and comparisons tonalite. Shear bands in greenschist facies rocks, with the Vedrette di Ries (Rieserferner) pluton indicating the sinistral kinematics of the DAV. High- (Eastern Alps-Italy). Neu. Jb. Mineral. Abh.,

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Volume n° 2 - from B16 to B33 B17 - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg Borsi S.,DelMoro A., SassiF.P., ZirpoliG.(1979). Borsi S.,DelMoro A., SassiF.P., ZirpoliG.(1973). Borsi S.,DelMoro A., SassiF.P., Zanferrari A., Bigi, G., A. Castellarin,M.Coli,G. V. DalPiaz, Bianchi A. (1934).Studipetrografi Bellieni G.,Justin Visentin E.,ZanettinB.(1995). Bellieni G.,Cavazzini G.,Fioretti A.M., Peccerillo A., Bellieni G.,Peccerillo A., PoliG.(1982)REE Bellieni G.,Peccerillo A., PoliG.(1981). The Vedrette Bellieni G.,MolinG.M., Visonà D.(1979) The Bellieni G.,CominChiaramontiP., Visonà D.(1976). Rdsch massif anditsgeodynamicsignifi On theageof Vedrette diRies(Rieserferner) Geol. It. radiometric andgeopetrologicdata. the southof Tauern Window (Eastern Alps): Metamorphic evolution ofthe Austridic rocksto 17pp. Window (Eastern Alps). austridic continentalmargin Southofthe Tauern radiometric dataonthealpinehistoryof Zirpoli G.(1978).New geopetrologicand (Italy). Structural modelofItaly, S.E.L.C.A., Florence M. Sartori,P. Scandone,andG.B. Vai (1990) Univ. Padova, 10;243pp. orientale eregioni limitrofe.Mem.Ist.Geol.R. Petrol. problems andsuggestions.Soc.It.Mineral. Silica) forclassifi Use ofthechemical TAS diagram(Totali Alkali (Eastern Alps). from the Vedrette diRiesplutoniccomplex geochemistry ofmicrogranularmafi Poli G.,ZantedeschiP. (1989).Petrologyand Mineral. Abh. signifi granodioritic complex anditspetrogenetic distribution inthe Cimadi Vila (Zinsnock) 145-156. on ItsGenesis. Petrological andGeochemicalDataBearing di Ries(Rieserferner)PlutonicComplex: Abh. di Ries(Eastern Alps-Italy). intrusive massifsofBressanoneand Vedrette petrogenetic signifi Geol. It. Vedrette diRies(AlpiOrientali). Contributo allaconoscenza delplutonedelle 138, 244-258. , 136,238-253. cance (Eastern Alps, Italy). ., 68,41-60. Plinius, , 12,549-571. , 95,351-370. , 145,50-65. 14,49-52. Per. Mineral. Contrib. Mineral. Petrol. cance ofthegarnetsin cation ofplutonicrocks: Mem. Sci.Geol. , 58,1-3,45-65. ci sull’Alto ci Adige Neu. Jb. Mineral. cance. c enclaves c Mem. Soc. Boll. Soc. Neu. Jb. Geol. , 78, , 32, Cesare B.(1999).Multi-Stagepseudomorphic Cesare B.(1999).Multi-Stagepseudomorphic Cesare B.(1994b).Synmetamorphicveining: origin Cesare B.(1994a).Hercynite astheproductof Cesare B.(1992).Metamorfi Dal PiazG.V., Von RaumerJ.,SassiF.P., ZanettinB., Dal Piaz,Gb., (1934).Studigeologicisull’Alto Adige Chopin, C.,Henry, C.,andMichard, A. (1991) Cescutti C.,Fioretti A.M., BellieniG.&CesareB. Cesare B.,PolettiE.,BoironM-C.&Cathelineau Cesare B.andHollisterL.S.(1995). Andalusite- Congress, Abstract Orientale). (Alto Adige austroalpino neidintornidi Vedrette diRies fi (2003). Studiopetrografi mineral assemblages. polymetamorphism: 2.algebraicanalysisof replacement ofgarnetduring Geology their interpretation. polymetamorphism: Microstructuresand replacement ofgarnetduring Journal ofMetamorphicGeology di Riescontactaureole,Eastern Alps, Italy. of andalusite-bearingveins inthe Vedrette 116, 239-246. Contributions to Mineralogy andPetrology aureole of Vedrette diRies,eastern Alps, Italy. staurolite decompositioninthecontact Padova Orientali, Italia). pelitiche nell’aureoladi Vedrette diRies(Alpi Coy SquyresEd. The EarthSciencesSocietyof Italian Alps. Reprintedfrom“GeologyofItaly” Zanferrari A. (1975).Geologicaloutlineofthe 242 pp. di Geologia Regia Università diPadova orientale eregioni limitrofe. J. Mineral terrain, Dora-MairaMassif,western Alps. Geology andpetrologyofthecoesite-bearing 121-136 based onfl Window: amodel offl in theZentralgneisComplex oftheSW Tauern M. (2001). Alpine metamorphismandveining 13, 687-700. inclusions. - Italy):fl bearing veins at Vedrette diRies(Eastern Alps Geolog ln porfi loni y, 17,735–746 , 106pp. , 17,723–73 uid phasecompositionbasedonfl ., 3,263-291. uid inclusions. uid rici acidiaffi Journal ofMetamorphicGeology pg.201 Unp. PhD Thesis, Univ. 4 Journal ofMetamorphic smo dicontattorocce Journal ofMetamorphic oranti nelbasamento co egeochimicodei udrc interactions uid-rock Tectonophysics GeoItalia 2003 Memorie Istituto , 12,643-653. 20-05-2004, 14:47:03 , 336, , 10, Eur. uid , , THE PERIADRIATIC INTRUSION OF VEDRETTE DI RIES - RIESERFERNER (EASTERN ALPS): PETROLOGY, EMPLACEMENT MECHANISMS

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the Libyan Arab Republic. Tripoli. Tauernfensters (Südtirol/Italien). Erlanger Dal Piaz G.V., Venturelli G., 1983. Brevi rifl essioni Geol. Abh., 114, 1-82. sul magmatismo post-ofi olitico nel quadro Kozur, H. (1991) The evolution of the Meliata- dell’evoluzione spazio-temporale delle Alpi. Halstatt ocean and its signifi cance for the early Memorie Società Geologica Italiana, 26, 5-19. evolution of the Eastern Alps and Western Exner C.H., (1976). Die Geologische Position der Carpathians. Paleogeogr. Paleoclimatol. Magmatite des periadriatischen Lineaments. Paleoecol. 87, 109-135. Verh. Geol., B 4:3-64. Laubscher H.P. (1985). The late Alpine (Periadriatic) Froitzheim, N., Schmid, S.M., and Fey, M. (1996) intrusions and the Insubric Line. Mem. Soc. Mesozoic paleogeography and the timing of Geol. It., 26, 21-30. eclogite-facies metamorphism in the Alps : A Mager D. (1985). Geologische Karte des working hypothesis. Eclogae geol. Helv., 89, Rieserfernergruppe zwischen Magerstein und 81-110. Windschar (Südtirol). Der Schlern, 6, Bozen Gatto G.O., Gregnanin A., Molin G.M., Piccirillo Mancktelow N.S., Stöckli D.F., Grollimund B., E.M., and Scolari A. (1976). Le manifestazioni Müller W., Fügenschuh B., Viola G., Seward D. Andesitiche polifasiche dell’Alto Adige and Villa I.M. (2001). The DAV and Periadriatic occidentale nel quadro geodinamico alpino. St. fault systems in the eastern Alps south of the Trentin. Sc. Nat., 53, 21-47. tauern Window. Int. J. Earth Sci., 90, 593-622. Guidotti C.V., (1968). Prograde muscovite Mann A. and Scheuvens D. (1998). Structural pseudomorphs after staurolite in the Rangeley- investigation of the northern contact of the Oquossoc areas, Maine. American Mineralogist, Rieserferner Plutonic Complex (Eastern Alps) 53, 1368-1376. - fi rst results. Terra Nostra, 98, 62. Green T.H. (1972). Crystallization of calc-alkaline Müller W., Mancktelow N.S. and Meier M. (2000). andesite under controlled high-pressure Rb-Sr microchrons of synkinematic mica in hydrous conditions. Contrib. Mineral. Petrol. mylonites: an example from the DAV fault of 34, 150-166. the Eastern Alps. Earth and Planetary Science Green T.H., and Ringwood A.E. (1972). Letters, 180, 385-397 Crystallization of garnet-bearing rhyodacite Müller W., Prosser G., Mancktelow N.S., Villa I.M., under high-pressure hydrous conditions. J. Kelley S.P., Viola G., and Oberli F. (2001). Geol. Soc. Aust. 19, 203-212. Geochronological constraints on the evolution Hammerschmidt K. (1981). Isotopengeologische of the Periadriatic fault system (Alps). Int. J. Untersuchungen am Augengneis vom Typ Earth Sci., 90, 623-653. Campo Tures bei Rain in Taufers, Südtirol. Neubauer, F. (1994) Kontinentkollision in den Mem. Sci. Geol., 34, 273-300. Ostalpen. Geowissenschaften 12, 136-140. Hofmann K.H., Kleinschrodt R., Lippert R., Mager Pattison, D.R.M. & Tracy, R.J., 1991: Phase equilibria D. und Stöchkert B. (1983). Geologische Karte and thermobarometry of metapelites. In: des Altkristallin südlich des Tauernfensters Kerrick, D.M. (ed.): Contact metamorphism. zwischen Pfunderer Tal und Tauferer Tal Reviews in Mineralogy, 26; 43-104 (Südtirol). Der Schlern, 57; 572-590. Prochaska W. (1981). Einige Gangesteine der Holdaway M.J. (1971). Stability of andalusite and Rieserfernerintrusion mit neuen radiometrischen the aluminum silicate phase diagram: American Altersdaten. Mitteilungen der Gesellschaft der Journal of Science, 271, 97–131 geologie und Berbaustudent, Wien, 27, 161- Kagami H., Ulmer P., Hansmann W., Dietrich V.,

171. B16 to B33 n° 2 - from Volume and Steiger R.H. (1991). Nd-Sr isotopic and Rosenberg, C.L., A. Berger, and S. M. Schmid (1995) geochemical characteristics of the Southern Observations from the fl oor of a granitoid Adamello (northern Italy) intrusives: pluton; inferences on the driving force of fi nal implication for crustal versus mantle origin. J. emplacement, Geology, 23, 443-446. Geophys. Res. 96, 14331-14346. Rosenberg, C. L., in press, Shear zones and magma Kerrick D.M. (1990). The Al SiO polymorphs. 2 5 ascent: A model based on a review of the Reviews in Mineralogy, 22. Tertiary magmatism in the Alps. Tectonics. Kleinschrodt R. (1987). Quarzkorngefügeanalyse im Altkristallin südlich des westlichen Sassi, F.P. & Zanettin, B. (1980) Schema degli eventi

31 - B17

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Volume n° 2 - from B16 to B33 B17 - B17 Leaders: B.Cesare,A.M.Fioretti,C.Rosenberg Steenken A. (2002). The emplacementofthe Steenken A., Siegesmund, S.andHeinrichs, T. (2000). Schulz B.(1997).Pre-Alpinetectonometamorphic Schulz B.(1989).JungalpidischeGefügeentwicklung Steenken A, Siegesmund S,Heinrichs T, Fugenschuh Santilli M.,OrombelliG.andPelfi Alps, Tyrol) history ofthe Austroalpine basement(Eastern Line aswelltothekinematicandthermal Rieserferner PlutonanditsrelationtotheDAV- Austria). Rieserferner Pluton(Eastern Alps, Italy/ B (2002).Coolingandexhumation ofthe 120 pp. of Structural Geology magnetic fabrics andmicrostructures. Constraints fromfi The emplacementoftheRieserfernerPluton: Petrographische Mitteilungen Window. to thesouthofcentral Tauern evolution inthe Austroalpine basement Bundesanst. (Osttirol, Österreich). entlang derDefereggen-Antholz-Vals-Linie Quat. Glaciological Committee. 1999 inferredbythedatasuppliedItalian Variations ofItalianglaciersbetween1980and Petrologia Rendiconti SocietàItalianadiMineralogia e metamorfi 25,61-76. Int. J. EarthSci ci emagmaticinelle Alpi Orientali. , 36;3-7. , 132;775-789. Schweizerische Mineralogische Geotektonische Forschungen , 22,1855-1873 ., 91,799-817. Geogr. Fis. Dinam. ed observations, eld Jahrbuch. Geol. , 77,281-297. ni M.(2002). Journal , 94, Wagner R.,C.Rosenberg L.,HandyM.R.,Möbus Wagner R.,C.L.Rosenberg, M.R.Handy, C.(2003). Von Blankenburg F. andDavis J.H.(1995). Trommsdorff V. andNievergelt P., (1983) The Stöckhert B.(1984).K-Ardeterminationson Stöckhert B.(1987).DasUttenheimerPegmatit-Feld Stöckhert B.(1985).Pre-Alpinehistoryofthe Pluton, Eastern Alps. transpressive shearzone: The Rieserferner driven infl C., and Albertz M.inreview, Buoyancy- Memorie diScienzeGeologiche (Padova), 54, 14, 120-131. magmatism andtectonicsinthe Alps. Slab breakoff: A modelforsyncollisional relations. Bregaglia (Bergell) IorioIntrusive anditsfi 83-106. Mineral. Abh valley, Southern Tyrol, Eastern Alps). the southofwestern Tauern Window (Ahrn Alpine deformationinthe Austridic basementto pegmatites, andtheminimumageofOld muscovites andphengitesfromdeformed alpine Überprägung. (Ostalpines Altkristallin, Südtirol)Geneseund Geol. Paläont. Mh., Caledonian versus Hercynian event. Tauern Window (Southern Tyrol, Italy). Austridic basementtothesouthofwestern Mem. Soc.Geol.It., ation ofamid-crustalsillfedby ., 150,103-120. 618-642. Erlanger Geol.Abh Geol. Soc. Am. Bull. 26,55-68. Tectonics Neu. Jb. Neu. Jb. 20-05-2004, 14:47:06 ., 114, eld

Back Cover: Road map of the area NE of Brunico. Numbers in yellow dots indicate the localities of each field trip’s day as in the Guide.

B17_copertina_R_OK E 20-05-2004, 14:36:29 FIELD TRIP MAP INTERNATIONAL GEOLOGICAL CONGRESS nd 32

Edited by APAT

B17_copertina_R_OK B 28-05-2004, 17:19:13