Geological Field Trips

Società Geologica Italiana

2014 Vol. 6 (2.1) ISPRA Istituto Superiore per la Protezione e la Ricerca Ambientale

SERVIZIO GEOLOGICO D’ITALIA Organo Cartografico dello Stato (legge N°68 del 2-2-1960) Dipartimento Difesa del Suolo

ISSN: 2038-4947

Crust-Mantle relationships close at hands Walking through the -Nonsberg orogenic lower crust Goldschmidt Conference - Firenze, 2013

DOI: 10.3301/GFT.2014.04 Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust R. Braga - G. M. Bargossi GFT - Geological Field Trips geological fieldtrips2014-6(2.1) Periodico semestrale del Servizio Geologico d'Italia - ISPRA e della Società Geologica Italiana Geol.F.Trips, Vol.6 No.2.1 (2014), 46 pp., 33 figs. (DOI 10.3301/GFT.2014.04) Crust-Mantle relationships close at hands Walking through the Ulten-Nonsberg orogenic lower crust Pre-conference Field Trip - Goldschmidt Conference Firenze, 2013

Roberto Braga, Giuseppe Maria Bargossi

Dip. Scienze Biologiche, Geologiche e Ambientali, Sezione di Geologia, Università di Bologna - Piazza di Porta S. Donato, 1 - 40126 Bologna ()

Corresponding Author e-mail address: [email protected]; [email protected]

Responsible Director Claudio Campobasso (ISPRA-Roma)

Editor in Chief Editorial Board Gloria Ciarapica (SGI-Perugia) M. Balini, G. Barrocu, C. Bartolini, Editorial Responsible 2 Maria Letizia Pampaloni (ISPRA-Roma) D. Bernoulli, F. Calamita, B. Capaccioni, W. Cavazza, F.L. Chiocci, Technical Editor R. Compagnoni, D. Cosentino, Mauro Roma (ISPRA-Roma) S. Critelli, G.V. Dal Piaz, C. D'Ambrogi, P. Di Stefano, C. Doglioni, E. Erba, publishing group Editorial Manager R. Fantoni, P. Gianolla, L. Guerrieri, Maria Luisa Vatovec (ISPRA-Roma) M. Mellini, S. Milli, M. Pantaloni, Fernanda Pilato (ISPRA-Roma) V. Pascucci, L. Passeri, A. Peccerillo, Convention Responsible L. Pomar, P. Ronchi, B.C. Schreiber, Anna Rosa Scalise (ISPRA-Roma) L. Simone, I. Spalla, L.H. Tanner, Alessandro Zuccari (SGI-Roma) C. Venturini, G. Zuffa. ISSN: 2038-4947 [online]

http://www.isprambiente.gov.it/it/pubblicazioni/periodici-tecnici/geological-field-trips

The Geological Survey of Italy, the Società Geologica Italiana and the Editorial group are not responsible for the ideas, opinions and contents of the guides published; the Authors of each paper are responsible for the ideas, opinions and contents published. Il Servizio Geologico d’Italia, la Società Geologica Italiana e il Gruppo editoriale non sono responsabili delle opinioni espresse e delle affermazioni pubblicate nella guida; l’Autore/i è/sono il/i solo/i responsabile/i. DOI: 10.3301/GFT.2014.04 Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust R. Braga - G. M. Bargossi geological fieldtrips2014-6(2.1)

INDEX

Information Itinerary

Information ...... 4 Day 1 - The garnet-spinel peridotites of Emergency contact numbers ...... 4 the Samerberg area ...... 29 Forest Guard Offices ...... 4 STOP 1.1: The garnet-spinel peridotites of the Maps ...... 4 Samerberg area ...... 29 Riassunto ...... 5 Abstract ...... 6 Day 2 - Peridotites, pyroxenites and migmatites ...... 32 STOP 2.1: The stromatic migmatites ...... 32 Excursion notes STOP 2.2: Pyroxenites and peridotites ...... 34 3 STOP 2.3: Nebulitic migmatites ...... 38 Excursion notes ...... 7 STOP 2.4: Peridotite-migmatite contact ...... 39 Geological Setting ...... 8 STOP 2.5 (optional): The Peridotite body of the Poinella lake .40 The Upper Austroalpine ...... 10 In Rumo – The Museo Giardino Geologico “Le Pietre delle Rock types ...... 11 Maddalene” ...... 41 Field occurrence of the Ulten-Nonsberg ultramafics ...... 12 Peridotites ...... 13 References ...... 44 Pyroxenites ...... 16 Paragneisses and migmatites ...... 17 Orthogneisses ...... 19

Mafic rocks ...... 19 index Petrology and metasomatic evolution ...... 20 Mantle and pyroxenites ...... 20 Crust ...... 24 Age dating ...... 26

DOI: 10.3301/GFT.2014.04 geological field trips 2014 - 6(2.1)

4 information day) cars day) nd R. Braga - G. M. Bargossi R. Braga and therefore good conditions are needed. physically demanding Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust DOI: 10.3301/GFT.2014.04 Proper training and equipment (mountains boots are compulsory, warm and waterproof clothes, gloves, and waterproof warm and equipment (mountains boots are compulsory, Proper training that summer thunderstorms and sunglasses and solar protection) for alpine conditions are required. Be aware snow are not uncommon. need to be arranged at the departure of the traverse (Sankt Nikolaus, ) and at the end (Mocenigo Ulten valley) (Sankt Nikolaus, at the departure of traverse need to be arranged Guard office must grant on the forest roads is toll-free but local Forest Travelling ). – Rumo, . and surroundings are listed in www.maddalene.it permissions. Accommodation in Rumo 2000 m asl (max height: Passo km at altitudes exceeding for several This field trip requires participants to hike the tree line, sometimes along steep slopes with ill-defined footpaths and loose 2340 m) well above Lavazzè, blocks. This field trip might be moraine Information Northern Italy). From Milano and Province, (Trento is Rumo The starting point of the field trip itineraries Brennero (see the index map below). Exit at Trento and A22 towards A4 to Verona highway by car, Venezia turn Mostizzolo, At and on the SS42. and continue to Mezzolombardo Michele – north or S. and to Trento trains involves (8.3 km). Public transport right and after 2.3 km turn left for the SP68 to Rumo station (bus at the Cles train leave Bus from Cles to Rumo local railway. then to Cles along the Trento-Malè (2 the traverse cars is highly recommended. For The use of 4-wheel website www.ttesercizio.it). Emergency Contact Numbers112 – Mountain rescue113 – Carabinieri118 – First Aid115 – Fire-fighters Maps Forest Guard Offices d’Ultimo / Ultental 1:25 000, sheet 042, Tabacco Val Topographic: and 026 (Appiano/Eppan). Geological: Carta Geologica d’Italia 1:50 000, sheets 025 (Rabbi) 1 itinerary) (Day +39 0473 920949 – Tesimo 2 itinerary) (Day Valburga/Ultimo +39 0473 795330 – S. 2 itinerary) (Day +39 0463 530126 – Rumo Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust R. Braga - G. M. Bargossi

Riassunto Index Map with geological fieldtrips2014-6(2.1) the simplified motorway Questa escursione di due giorni è dedicata network (toll all’osservazione di rocce uniche nel panorama roads) of geologico italiano, affioranti nell’unità d’Ultimo della Northern Italy. The red square nuova cartografia geologica alla scala 1:50.000. refers to the L’unità d’Ultimo è conosciuta nella letteratura simplified road specialistica anche con il nome di zona d’Ultimo o map on the right. Nonsberg-Ulten Zone. Si tratta di un basamento cristallino Varisico essenzialmente costituito da paragneiss e migmatiti di alta pressione che includono lenti di peridotiti del mantello. Questa associazione litologica ha avuto origine in una zona di collisione continentale che raggiunse il picco metamorfico 340-330 milioni di anni fa. L’eccezionalità dell’unità d’Ultimo risiede nella possibilità di osservare sul terreno la trasformazione di peridotiti a spinello in peridotiti caratterizzate dall’associazione granato-spinello. Questa transizione è accompagnata dalla reazione con fluidi crostali che 5 producono la cristallizzazione di abbondante anfibolo ± flogopite ± dolomite ± apatite. L’escursione ha lo scopo di rendere accessibile una lunga tradizione di studi petrologici iniziati già dalla seconda metà del XIX secolo e che ha permesso di aumentare la nostra conoscenza sui processi metasomatici indotti dal trasferimento di elementi da sorgenti crostali subdotte verso reservoir mantellici. La prima parte della guida riassume, in modo schematico, la geologia dell’unità d’Ultimo e le varie ipotesi petrogenetiche information proposte. La seconda parte illustrerà le peridotiti a granato-spinello della zona della Conca di Brez/Samerberg (primo giorno) e l’entusiasmante traversata di alta montagna attraverso la catena delle Maddalene, dalla Malga di Monte d’Ora (Val d’Ultimo, prov. di ) verso Lavazzè (Val di Non, prov. di Trento), per osservare le relazioni fra peridotiti, pirosseniti e migmatiti (secondo giorno).

Parole chiave: Peridotiti a granato, pirosseniti, interazione crosta-mantello, crosta profonda, Ulten-Nonsberg, Alpi Orientali. DOI: 10.3301/GFT.2014.04 geological field trips 2014 - 6(2.1)

6 information R. Braga - G. M. Bargossi R. Braga day). nd day) and the exciting traverse and the exciting day) st Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Garnet-peridotites, pyroxenites, crust-mantle interactions, lower crust, Ulten-Nonsberg, Eastern Alps. DOI: 10.3301/GFT.2014.04 through the Maddalene range, from the Auerbergtal (Ulten valley) to the Lavazzè valley (Non valley), to (Non valley), valley to the Lavazzè from the Auerbergtal (Ulten valley) through the Maddalene range, and migmatites (2 address the field relation among mantle peridotites, pyroxenites Abstract Eastern crystalline basement of the Ulten-Nonsberg Zone, focuses on the Variscan excursion This two-day or unità d’Ultimo in the new geological also known as the Ulten Zone Italian Alps. The Ulten-Nonsberg Zone, and migmatites containing map of Italy (1:50 000 scale), mainly consists high-pressure paragneisses disseminated lenses of mantle peridotites. This lithological association originated in a continent-continent the Ulten-Nonsberg special is that reached its metamorphic peak at 340-330 Ma. What makes collision zone This transformation from spinel- to garnet-spinel-peridotites. the opportunity to see in field transition The fluids were responsible from a submerging crustal slab. fluids derived occurred during the influx of C-O-H amounts of dolomite and apatite. for the blastesis of abundant amphibole ± phlogopite and trace of field and petrological studies accessible to a wider audience a long tradition This field trip aims to make collision works and what are the to showcase our increased knowledge on how a continent-continent a The first part of this guide provides mass transfer. by the crust-to-mantle metasomatic processes driven geology and of some the petrogenetic models proposed. The second summary of the Ulten-Nonsberg Zone lenses occurring in the Samerberg area (1 part describes the garnet-spinel Key words: Key geological field trips 2014 - 6(2.1)

7 excursion notes R. Braga - G. M. Bargossi R. Braga Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Fig. 1 - The geological map of the NE red ink and published in 1936. portion of the Ulten-Nonsberg Zone, by Ciro Andreatta with a beautiful sketched DOI: 10.3301/GFT.2014.04 Excursion notes The inland access to the deep crust/upper mantle can be reached by shreds of crust and studying xenoliths, mantle brought to the surface by uprising rocks, or by examining exhumed volcanic into basements now incorporated collisional belts. The latter approach is up to km- provide since it may valuable scale crustal sections where the between upper petrogenetic interactions mantle and felsic materials can be conditions. under favourable investigated The Ulten-Nonsberg lower crust, long renowned for containing some of the best peridotites of exposure of garnet-spinel the entire Alps, represents a remarkable site to gain insights into mantle petrogenesis and metasomatism occurring during collisional tectonics continental margins. involving geological field trips 2014 - 6(2.1)

8 excursion notes R. Braga - G. M. Bargossi R. Braga , i.e. olivine-rich Oliviniti Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust DOI: 10.3301/GFT.2014.04 rocks. Since 1970, several studies marked a new interest for the Ulten-Nonsberg lower crust (Amthauer et al., studies marked rocks. Since 1970, several & Brenneis, 1978). The new petrological research 1977; Rost 1976-1977; Herzberg et al., 1971; Morten et al., the first modern for the seminal paper by Obata & Morten (1987) that gave environment set the cultural of the peridotites and metasomatic reactions transition petrologic account on the spinel- to garnet-facies between Bologna and Genova peridotite. A fertile cooperation the formation of garnet-amphibole governing produced important results on crustal metasomatism of mantle rocks, as summarised by Universities Scambelluri et al. (2010). In the same time, new field data and isotopic ages obtained during production of Trento and the Autonomous Provinces of Padova of the new Geological Map Italy and led by University of the Ulten- evolution and Bolzano added new views and, sometimes, dissenting ideas for the Variscan & Martin, 2003). Nonsberg basement (see the historical review by Tumiati The Ulten-Nonsberg lower crust is known as a site of interest for mineral collectors since the mid-nineteenth The Ulten-Nonsberg lower crust is known as a site of interest for mineral work before the XX century (Doblicka, 1852). Austrian scientists produced an intense field and petrographic 1899). A major breakthrough in the 1891; Hammer, 1866; Stache, 1880, 1881; Ploner, century (Sandberger, map of Ciro the geological and structural geological knowledge of the Ulten-Nonsberg lower crust was Andreatta (Andreatta, 1936). This map (Fig. 1) already reports the main features of this basement: metre- to by Andreatta in full red and classified as hundred meters-long peridotite bodies drawn Geological Setting of the European and Adriatic plate The Alpine Belt is the result of Late Cretaceous-Present convergence ocean. Tethys of the Western branch Piedmont-Ligurian margins, leading to the consumption of Jurassic continental collision The closure of the ocean occurred during Eocene-Miocene and led to Europe-Adria subdivided in four and the subduction of European continental margin. The Alps are traditionally domains (Fig. 2): tectonostratigraphic continental margin of the European continent; representing the proximal - Helvetic, rocks tectonically intermingled, (including the Briançonnais units), continental- and oceanic-derived - Penninic Alps and in tectonic windows (Engadine; Tauern); best exposed in the Western - Austroalpine, originated from the Adriatic plate cropping out in two sectors of Alpine belt (Eastern and Austroalpine); Western from the Adriatic margin. - Southern Alps, derived geological field trips 2014 - 6(2.1)

9 excursion notes R. Braga - G. M. Bargossi R. Braga Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Fig. 2 - Tectonic map of the Alps from Handy & Oberhänsli (2004). The black lines represent major tectonic boundaries. Fig. 2 - Tectonic red box shows the location of map in Fig. 3. red box The reader is refereed to the above authors for a comprehensive description of the several fault systems here reported.The description of the several authors for a comprehensive The reader is refereed to the above DOI: 10.3301/GFT.2014.04 The Helvetic and Penninic zones, and the Austroalpine nappe system are characterised by Europe-vergent and the Austroalpine nappe system are characterised zones, and Penninic The Helvetic These domains are juxtaposed along the Periadriatic structures whereas the Southern Alps are Adria-vergent. strike-slip (Insubric) lineament, a dextral during Oligocene- fault system active Neogene times. geological field trips 2014 - 6(2.1) excursion notes 10 R. Braga - G. M. Bargossi R. Braga Fig. 3 - Geological sketch of Fig. 3 - Geological sketch (1999). the Ulten-Nonsberg zone (gray). the Ulten-Nonsberg zone Modified after Del Moro et al. faults (Fig. 3). Within the nappe, the NE-trending Tonale line is a Paleocene Rumo extension-related fault that marks the contact between high-pressure the high-grade, Ulten-Nonsberg peridotite- bearing basement and the amphibolite-facies peridotite- free basement known as the unit (Fig. 4). Tonale Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust DOI: 10.3301/GFT.2014.04 The Upper Austroalpine In particular, The Ulten-Nonsberg lower crust belongs to the Upper Austroalpine of Italian geological literature. crust bounded by Alpine nappe, a slice of Variscan the Ulten-Nonsberg crust is part of basement Tonale geological field trips 2014 - 6(2.1) excursion notes 11 R. Braga - G. M. Bargossi R. Braga Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Fig. 4 - Cross-section of the Tonale nappe located just north of the geological map of Fig. 3. Ulten Zone: GK, nappe located just north of the geological map Fig. 3. Ulten Zone: Fig. 4 - Cross-section of the Tonale simplified from the Sheet 026 “Appiano/Eppan” of the Carta Geologica d’Italia 1:50.000, Avanzini et al., (2007). et al., of the Carta Geologica d’Italia 1:50.000, Avanzini simplified from the Sheet 026 “Appiano/Eppan” garnet-kyanite gneisses; Mi, migmatites; P, peridotites. Tonale unit: Pa, sillimanite paragneisses; A, mafic sillimanite paragneisses; unit: Pa, peridotites. Tonale gneisses; Mi, migmatites; P, garnet-kyanite and Redrawn Dolomia Principale (Upper Triassic). orthogneisses. Southern Alps: Do, amphibolites; Ma, marbles; O, DOI: 10.3301/GFT.2014.04 Rock types and subordinate paragneiss The Ulten-Nonsberg orogenic lower crust consists of migmatites, kyanite-bearing Although the layers. peridotites including pyroxenite mafic amphibolites, orthogneiss and mantle-derived petrological studies deal with the peridotites form a minor component of the basement, most available background information on the field occurrence and 2010). Here we provide (Scambelluri et al., ultramafics how the Ulten-Nonsberg rocks appear under polarizing optical microscope. geological field trips 2014 - 6(2.1) excursion notes 12 R. Braga - G. M. Bargossi R. Braga Fig. 5 - Typical exposure of ultramafic rocks in the Ulten- exposure of ultramafic Fig. 5 - Typical olivine; dull gray, orthopyroxene. Pen length is about 17 cm. Pen orthopyroxene. olivine; dull gray, Nonsberg, Seefeldalm area. Coarse-grained peridotite: ochre, Nonsberg, Seefeldalm area. Coarse-grained Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust DOI: 10.3301/GFT.2014.04 Field occurrence of the Ulten-Nonsberg ultramafics Most of the mantle peridotites Ulten-Nonsberg lower crust outcrop in an area delimited by which includes the villages and the upper Non valley, to the South, southern flank of Ulten valley valley is known as Maddalene. (Fig. 3). The mountain range and of Rumo In the field, mantle peridotites offer two styles of occurrence. The first style consists barrel-shaped lenses that the peridotite bodies slid or pods embedded into quaternary glacial deposits (Fig. 5). Although it is likely their location in a rather by mass wasting, narrow band between the garnet-kyanite migmatites is a gneisses and the overlying remarkable coincidence. A few hundreds meter long peridotite bodies embedded into country gneisses/migmatites represent the second outcrop style. An important example is the peridotite body occurring in a steep gully on the (Marocchi et of the Mt. Hochwart western wall 2009). Here, metasomatic reactions bands al., locally mark the peridotite-migmatite contact. according to this The reaction bands are zoned sequence: migmatite | phlogopitite rocks | garnet- anthophyllite-talc-rich 2009). In amphibole peridotite (Marocchi et al., other sites, e.g. the outcrop west of Masa the peridotite- in the upper Non valley, Murada of with no development crust contact is sharp, & Sapienza metasomatic reaction bands (Braga a modal increase of 2007). In this outcrop, in the peridotite phlogopite can be observed the contact with country gneisses. towards geological field trips 2014 - 6(2.1) excursion notes 13 sensu R. Braga - G. M. Bargossi R. Braga chlorite and black Mercier & Nicolas, 1975) with a grain up to 5-6 mm (Fig. 7a). The size assemblage consists of large mineral and olivine and orthopyroxene, kinked and dark brown smaller clinopyroxene spinel. The latter occurs disseminated in the rock matrix, as exsolutions and intergrowth with pyroxenes Porphyroclastic orthopyroxene. samples contain garnet that typically surrounds brown spinel (Fig. 7b). In appear also as addition, garnet may with rounded large porphyroblast spinel inclusions and as elongated from large pyroxenes. exsolved grains peridotites have The fine-grained ≤ 1 mm and are size grain average mainly spinel harzburgites with high modal amounts of amphibole (up to & Morten, 2001) Rampone 23 vol%, and accessory spinel. Their (micro)structure ranges transition from protogranular to from protogranular transition microstructure ( porphyroclastic Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Fig. 6 - Fine-grained peridotite. The preferred orientation of olivine Fig. 6 - Fine-grained parallel to the foliation. The diameter of coin is 2.7 cm. parallel defines the fabric. An elongated orthopyroxene porphyroclasts is aligned porphyroclasts defines the fabric. An elongated orthopyroxene DOI: 10.3301/GFT.2014.04 Peridotites been subdivided 1992) and they have (Bondi et al., from harzburgite (abundant) to lherzolite varies Peridotites 2003): coarse and (Obata & Morten, 1987; Morten Trommsdorff, size into two groups based on the grain fine types, with the former considered as protolith of latter (Fig. 6). The coarse peridotites show geological field trips 2014 - 6(2.1) excursion notes 14 R. Braga - G. M. Bargossi R. Braga Olivine and orthopyroxene porphyroclasts Olivine and orthopyroxene Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust DOI: 10.3301/GFT.2014.04 from porphyroclastic to tabular equigranular and granoblastic (Fig. 7c). and granoblastic to tabular equigranular from porphyroclastic typically show internal deformation features (kink bands) while the tabular equigranular microstructure is typically show internal deformation features (kink bands) while the tabular equigranular garnet aggregates. Relic defined by the shape preferred orientation of undeformed olivine and orthopyroxene of amphibole are recognised under the polarizing generations rim is also found. Two rimmed by a kelyphitic microscope: pale to brownish green magnesiohornblende and colourless tremolite, the latter also rimming equilibrium with tremolite and as large chlorite occurs in textural magnesiohornblende cores. Retrograde enclosing black spinel. Phlogopite appears in the peridotites close to contact with country grains forms a foliation concordant to the lithological gneisses. The preferred orientation of the phlogopite flakes boundaries (Fig. 7d). type and in the tabular equigranular garnet-spinel-peridotites dolomite occurs both in the coarse-grained Rare 2009). Dolomite 2007; Sapienza et al., et al., 2003; Braga (Obata & Morten, 1987; Morten Trommsdorff, with regular and grain, mm in length or as matrix-forming (Fig. 7e) up to several occur as porphyroclasts may (Fig. 7f). contacts with surrounding minerals Apatite has been also found in association smooth grain-grain 2009). with dolomite (Sapienza et al., geological field trips 2014 - 6(2.1) excursion notes 15 Fine- and D E Fine-grained C R. Braga - G. M. Bargossi R. Braga and 1 mm for D to A Smooth grain-grain contacts involving Smooth grain-grain F Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Porphyroclastic peridotite with large anhedral garnet (Gt) and spinel inclusion; partly crossed nicols. peridotite with large anhedral Porphyroclastic B Coarse-grained peridotite type with large olivine (Ol), orthopyroxene (Opx) and anhedral spinel (Spl); plane polarized (Opx) and anhedral peridotite type with large olivine (Ol), orthopyroxene Coarse-grained A Dolomite (Dol) porphyroclast in a garnet-bearing matrix; plane polarized light. matrix; plane polarized in a garnet-bearing Dolomite (Dol) porphyroclast Fig. 7 - Main textural features of the Ulten-Nonsberg peridotites. Scale length is 0.4 mm from Fig. 7 - Main textural dolomite, amphibole and olivine; crossed nicols. . grained peridotite type showing abundant amphibole (Amp) and a foliation outlined by phlogopite (Phl); plane polarized light. peridotite type showing abundant amphibole (Amp) and a foliation outlined by phlogopite (Phl); plane polarized grained E peridotite type consisting of an aggregate, locally polygonal, of unstrained olivine and orthopyroxene; crossed nicols olivine and orthopyroxene; peridotite type consisting of an aggregate, locally polygonal, unstrained F light. DOI: 10.3301/GFT.2014.04 geological field trips 2014 - 6(2.1) excursion notes 16 R. Braga - G. M. Bargossi R. Braga Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Fig. 8 - Garnet-amphibole-websterite from the Seefeldalm Fig. 8 - Garnet-amphibole-websterite and garnet. Sample length: 10 cm. area. The large porphyroclast (arrow) is a clinopyroxene with (arrow) is a clinopyroxene area. The large porphyroclast exsolutions. Purplish-red garnet is visible at the orthopyroxene granular and the fine-grained contact between the porphyroclast amphibole orthopyroxene, matrix, which is made of clinopyroxene, DOI: 10.3301/GFT.2014.04 Pyroxenites websterite and amphibole of garnet-amphibole Layers in cutting peridotite lenses can be observed clinopyroxenite different locations of the Ulten-Nonsberg unit. Although of the represent only a few percent by volume pyroxenites lenses, some of the best exposures are those ultramafic around the Seefeld/Lago della Siromba area, southern side form layers (Fig. 3). Pyroxenites of the Ulten valley along the peridotite foliation, with sharp transposed host peridotites. contacts towards Morten & Obata (1983) were among the first to provide websterite and petrological data on the garnet-amphibole from the Seefeld/Lago della Siromba area. clinopyroxenite megacrysts (up to The websterite consists of clinopyroxene and garnet exsolutions, 6 cm; Fig. 8) with orthopyroxene mosaic matrix composed of dispersed in an equigranular amphibole, garnet and clinopyroxene, orthopyroxene, is made of diopside, brown spinel. Clinopyroxenite magnesiohornblende, garnet and accessory amounts of ilmenite. geological field trips 2014 - 6(2.1) excursion notes 17 R. Braga - G. M. Bargossi R. Braga Fig. 9 - View from SE (Rio Valle valley) towards Ilmenspitz/Cima degli Olmi. The towards valley) Fig. 9 - View from SE (Rio Valle overlying nebulitic migmatites (diatexites). overlying dashed line, drawn in correspondence of a change colour the altered surface dashed line, drawn rocks, indicates the contact between stromatic migmatites (metatexites) and Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust DOI: 10.3301/GFT.2014.04 Paragneisses and migmatites the metamorphic grade metamorphic zoning: by an inverted The Ulten-Nonsberg crust (Fig. 9) is characterised along the crustal sequence. Staurolite-garnet bearing micaschists crop out in upwards increases moving These See/Lago di Alborelo. and Pankrazer Valburga between the localities St. Walburg/Santa Ulten Valley, by gneisses characterised contact to garnet-kyanite through a gradational way micaschists (Fig. 10a-b) give foliation defined by alternating mica-rich and mylonitic minor modal amounts of white mica and a marked from the garnet-kyanite The transition around garnet porphyroclasts. wrapping quartz+feldspars layers to the overlying paragneisses by the migmatites is marked presence of the ultramafic from lenses. Migmatites range mica-rich, foliated metatexites and to poorly foliated quartz- plagioclase-rich diatexites (Del 1999). The Moro et al., domains from the leucocratic migmatites are inequigranular aggregates of quartz + plagioclase ± alkali-feldspar (all boundaries) with irregular grain alternating with melanocratic domains containing biotite and garnet and kyanite. anhedral Within the migmatites, rare rocks (garnet ~ 90 garnet-rich with minor amounts of vol%) quartz and interstitial kyanite, biotite occur. geological field trips 2014 - 6(2.1) excursion notes 18 R. Braga - G. M. Bargossi R. Braga Anhedral garnet (Grt) Anhedral (A) Anhedral white mica (Wm) in a large Anhedral (D) Staurolite (St) porphyroclast in a mica-rich domain (Bt; Wm). Plane Staurolite (St) porphyroclast (B) Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Kyanite (Ky) with rutile (Rt) inclusions. Plane polarized light. with rutile (Rt) inclusions. Plane polarized (Ky) Kyanite (C) Fig. 10 - The Ulten-Nonsberg crust under the polarizing microscope. Scala bar is 0.4 mm. plagioclase (Pl) porphyroblast from leucosome. Crossed nicols. plagioclase (Pl) porphyroblast porphyroclast elongated in concordance with the main foliation made of white mica (Wm) and biotite (Bt). Garnet is riddled porphyroclast light. (fluid?) inclusions. Plane polarized with tiny light. polarized DOI: 10.3301/GFT.2014.04 geological field trips 2014 - 6(2.1) excursion notes 19 R. Braga - G. M. Bargossi R. Braga Fig. 11 - Close view of a foliated mafic amphibolite with leucocratic 2.2 cm across. quartz-feldspar lenses. Val Lavazzè, east of Malga Masa Murada. Coin is east of Malga Masa Murada. Lavazzè, lenses. Val quartz-feldspar weakly foliated amphibole-bearing orthogneiss rich in quartz and 1999). Aggregates made of Al-rich plagioclase (Del Moro et al., phases such as corundum, epidote, staurolite and white mica of enclaves been interpreted as former femic microgranular have 1996). igneous origin (Godard et al., Mafic rocks mafic amphibolites occur in association with to massive Foliated (Fig. 11). In the Seefeld Lavazzè migmatites, e.g. in the Val Alm/Malga Siromba area, mafic amphibolites with relics of a former eclogite assemblage are described in Godard et al. (1996). Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust DOI: 10.3301/GFT.2014.04 Orthogneisses and Orthogneisses are present as concordant intercalations within gneisses and migmatites. On textural texture grounds, we define two orthogneiss types: the first type shows a porphyroclastic mineralogical quartz and plagioclase set in an mm across) anhedral by the presence of large (several characterised matrix composed mainly of quartz and feldspars. Biotite occurs in minor modal amounts inequigranular small rounded garnet, rutile and white mica are accessory phases. The second type is a medium-grained, geological field trips 2014 - 6(2.1) excursion notes 20 data P-T R. Braga - G. M. Bargossi R. Braga path proposed for the P-T Fig. 12 - of Braga & Sapienza (2007). of Braga Ulten-Nonsberg peridotites. Modified from Scambelluri et al. (2010) with the 800-900°C; ~ 2.0 ~ 730°C; ~ 1.6 GPa) is the ~ 730°C; 1.6 GPa) conditions of 1.3-1.6 GPa and conditions of 1.3-1.6 GPa HP stage; P-T Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust LP stage; of Fig. 12; ~ 1,200°C; ≤ 1.5 GPa) into HP of Fig. 12; ~ 1,200°C; ≤ 1.5 GPa) spinel stage DOI: 10.3301/GFT.2014.04 GPa). Exhumation and retrogression to spinel–chlorite- GPa). ( amphibole–assemblages Petrology and metasomatic evolution Mantle and pyroxenites of The Ulten-Nonsberg peridotites record the transformation spinel-facies assemblages coarse-grained shallow anhydrous ( porphyroclastic garnet-spinel-amphibole assemblage as the result garnet-spinel-amphibole porphyroclastic of cooling at increasing pressure ( last stage recorded by the Ulten-Nonsberg ultramafics. This last stage recorded by the Ulten-Nonsberg ultramafics. corner flow of a lithospheric consistent with the downward evolution a subducting crustal slab (Fig. 13) that was mantle wedge overlying undergoing partial melting. The crustal anatectic melts reacted with and residual fluids layers peridotites producing orthopyroxene of the residual enriched in incompatible elements. The infiltration fluids into the mantle wedge produced amphibole + garnet (± dolomite) peridotites (Scambelluri et al. 2006). Based for the pyroxenites. Only few petrological data are available and rocks, Morten & compositions of minerals on major-element Obata (1983) suggested that the protolith of garnet-amphibole segregated from clinopyroxenite a garnet-free websterite was basaltic liquids intruding the upper mantle. A subsequent study by Nimis & Morten (2000) provided 1430-1470 °C for the igneous stage. After stage, shared a common petrological history along with the pyroxenites peridotite host. geological field trips 2014 - 6(2.1) excursion notes 21 R. Braga - G. M. Bargossi R. Braga analyses of minerals. The analyses of minerals. in situ Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Fig. 13 - Mantle wedge dynamics during the genesis of Ulten-Nonsberg lower crust. The model requires coupling occurred during the exhumation of crust. Modified from Scambelluri et al. (2010). existence of orthopyroxenite layers produced during the reaction between crustal anatectic melts and peridotite. layers existence of orthopyroxenite and enrich the mantle wedge. The crust-mantle upwards fluids, rich in incompatibile elements, move Residual DOI: 10.3301/GFT.2014.04 transition from spinel- to garnet-spinel peridotites is marked by the presence of amphibole (± dolomite) and peridotites is marked from spinel- to garnet-spinel transition A large number of studies focused on the metasomatic evolution of the Ulten-Nonsberg ultramafics, as recently of the Ulten-Nonsberg ultramafics, A large number of studies focused on the metasomatic evolution elements data were acquired both on bulk samples (Figs. reviewed by Scambelluri et al. (2010). Critical trace & Morten (2001), by 14-15) and, starting from the work of Rampone geological field trips 2014 - 6(2.1) excursion notes 22 R. Braga - G. M. Bargossi R. Braga evolution of the Ulten-Nonsberg evolution P-T Fig. 15 - Selected modal and incompatible peridotite (Scambelluri et al., 2010). peridotite (Scambelluri et al., elements data showing the increased amounts of fluid-mobile elements of the HP and LP stages peridotites with respect to the spinel-stage peridotites. an overall LREE and LILE enrichment (Fig. 14). an overall The further enrichment in amphibole and U in the Sr, other fluid-mobile elements as Pb, peridotites (LP amphibole + spinel retrograde stage, Fig. 15) indicates a prolonged supply of fluid and incompatible elements during the whole , spinel (B) and (A) Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust , garnet-bearing hydrous peridotites. From hydrous , garnet-bearing (D) and (C) Fig. 14 - Normalised whole-rock REE and incompatible elements Scambelluri et al. (2010). peridotites. patterns for the Ulten-Nonsberg peridotites. DOI: 10.3301/GFT.2014.04 The trace element composition of minerals reveals a reveals element composition of minerals The trace The enrichment in some multifaceted metasomatic history. LILE and light REE, along with lithium enrichment in indicates that the coarse and orthopyroxene, clinopyroxene spinel peridotites underwent an early cryptic metasomatic 2006). by mafic melts (Scambelluri et al., driven event geological field trips 2014 - 6(2.1) excursion notes 23 R. Braga - G. M. Bargossi R. Braga fluid. The REE distribution among garnet, 2 O-CO 2 crust-derived components (Rampone & Morten, 2001; components (Rampone crust-derived 2006). The LP peridotites, Scambelluri et al., by the chlorite + amphibole ± dolomite characterised fluids assemblage, indicate that metasomatic C-O-H percolated the peridotites also during retrogression, i.e. at shallower lithospheric levels. Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Fig. 16 - Normalised REE and incompatible element patterns in minerals from garnet-bearing peridotites (Sapienza et al., 2009). peridotites (Sapienza et al., from garnet-bearing Fig. 16 - Normalised REE and incompatible element patterns in minerals DOI: 10.3301/GFT.2014.04 clinopyroxene, amphibole and dolomite in the garnet peridotites reflects an equilibrium partitioning (Fig. 16) clinopyroxene, the LREE and LILE- and confirms that the fluid influx occurred at peak pressure conditions. Moreover, peridotites indicate that the incoming fluids carried Ba) of the garnet-spinel-amphibole Pb, enrichments (e.g. Sr, The age of the early metasomatism is poorly constrained, possibly pre-Variscan (Petrini & Morten, 1993). During (Petrini possibly pre-Variscan The age of the early metasomatism is poorly constrained, the HP stage, coronitic garnet assemblages replaced coarse spinel peridotites and were progressively amphibole-rich (± dolomite and apatite) assemblages. The presence of amphibole by fine-grained obliterated and carbonates required an open-system input of H geological field trips 2014 - 6(2.1) excursion notes 24 R. Braga - G. M. Bargossi R. Braga Fig. 17 - Summary of the available Ma, Langone et al., 2011. Ma, Langone et al., P–T paths for the Ulten-Nonsberg crust P–T & Massonne, (modified after Braga 1996; H96, 2008): G96, Godard et al., 1996; T03, Tumiati et al., Hauzenberger 2007. et al., 2003; B07, Braga et al., 2003; et al., Age data: 330 Ma, Tumiati et al., 2007; 302 Ma, Hauzenberger 2003; 350 et al., 1993; 205 Ma, Tumiati P- during progressive produced a clockwise values for the crust differ among values range of 1.0-2.0 GPa and 600-900° C, of 1.0-2.0 GPa range climax (~ 1.2 GPa) climax (~ 1.2 GPa) T values (< 1.0 GPa; < 650 °C) related to (< 1.0 GPa; values Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust P P-T T and 330 Ma) determined for the metamorphic peak P and c. P path during the Variscan orogeny, with a pressure peak orogeny, path during the Variscan P-T path characterized by a path characterized DOI: 10.3301/GFT.2014.04 Crust consensus that the Ulten-Nonsberg crust followed a There is a general clockwise that predates the thermal maximum (Godard et al., 1996; Hauzenberger that predates the thermal maximum (Godard et al., 2007; et al., 2004; Braga et al. 2003; Morten al., 1996; Tumiati et al., & Massonne, 2008). Braga The determined peak available studies (Fig. 17). Godard et al. (1996) proposed for the available a wide peak paragneisses Migmatites activity. depending on assumptions about the water yield low generally 1996). the retrogression stages (Godard et al., et al. (1996) Hauzenberger Based on relics of eclogite-facies minerals, or more and suggested that the metamorphic peak occurred at 1.5 GPa near the coesite stability et al. (2003) estimated values 750° C. Tumiati HP conditions field for the crustal rocks. The explanation of these very lies in the same age ( of garnet-peridotites and crustal rocks (Tumiati et al. 2003). and crustal rocks (Tumiati of garnet-peridotites gneisses by Braga thermobarometric work on garnet-kyanite Recent & Massonne (2008) et al. (2007) and Braga T heating and a thermal peak between 700-750 C° at about 1.0 GPa, i.e. during the first stages of exhumation process. This relatively gneisses is also for the Ulten-Nonsberg garnet-kyanite LP evolution as inclusions in both garnets and supported by the lack of HP minerals & Massonne, 2008). The source rocks of the zircons (Braga gneisses, produced about 20-30 migmatites, i.e. the garnet-kyanite geological field trips 2014 - 6(2.1) excursion notes 25 ) B ≤ -1 P R. Braga - G. M. Bargossi R. Braga (Fig. 18a). This -1 loop characterised by loop characterised Tectonic exhumation of the Tectonic P-T A) Lower crust delamination model B) Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust O that exceeded the water crystallographically bounded in micas. According to Braga & Massonne (2012) bounded in micas. According to Braga crystallographically the water O that exceeded 2 A Fig. 18 - Cartoons showing two working hypotheses on the Ulten-Nonsberg geodynamics. Fig. 18 - Cartoons showing two working hypotheses of the thickened lower crust. UN indicates the inferred position of Ulten-Nonsberg of the thickened 1.2 GPa and relates the HT conditions, which led to migmatization, upwelling of upper mantle following foundering 1.2 GPa envisaged by Braga et al., 2007; Braga & Massonne, 2008; 2012. This scenario agrees with a 2007; Braga et al., by Braga envisaged Ulten-Nonsberg lower crust during ongoing, high-angle continental subduction (redrawn from Ranalli et al., 2005). This et al., from Ranalli continental subduction (redrawn Ulten-Nonsberg lower crust during ongoing, high-angle 2003. et al., HP crustal signature proposed by Tumiati scenario agrees with the very DOI: 10.3301/GFT.2014.04 the excess water needed to sustain the anatexis was stored in pore spaces along grain boundaries. stored in pore spaces along grain needed to sustain the anatexis was water the excess for the orthogneisses. Most of samples studied so and petrological data are available Limited petrographic According to Del Moro et al. far are from the Cima Binasia area where amphibole-bearing orthogneisses occur. protoliths with magmatic ages of 400 Ma. Field evidence suggests granitoid (1999) these orthogneisses have and migmatites. history with the paragneisses that the orthogneisses shared a common high-grade et modelled by Ranalli peridotites, was The exhumation of the Ulten-Nonsberg crust, along with entrained al. (2005) as a two-stage process. In the first stage, Ulten-Nonsberg crust underwent buoyancy-driven of abouttectonic extrusion along the subduction channel, at an exhumation rate 0.1-1 cm a and lasted nearly 100 Ma, bringing rocks to shallow lithospheric levels (< 20 km). and lasted nearly 100 Ma, bringing rocks to shallow lithospheric levels vol% of melt by the breakdown of white mica (Braga & Massonne, 2012). Partial melting required an amount & Massonne, 2012). Partial of melt by the breakdown white mica (Braga vol% of H stage, which proceeded for 30 Ma, is believed to have brought the crust from depths ≥ 100 km, assuming to have stage, which proceeded for 30 Ma, is believed slow (about 0.01-0.1 cm a et al. (2003). The second exhumation stage was HP conditions of Tumiati very geological field trips 2014 - 6(2.1) excursion notes 26 paths P-T R. Braga - G. M. Bargossi R. Braga Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust paths are not fully consistent, the geodynamic evolution for the Ulten-Nonsberg orogenic paths are not fully consistent, the geodynamic evolution P-T DOI: 10.3301/GFT.2014.04 is considering the delamination of the lithospheric mantle (Braga et al., 2007; Braga & Massonne, 2008; 2012). 2007; Braga et al., is considering the delamination of lithospheric mantle (Braga and Laurussia forming the The delamination followed the long-lasting, continuous collision of Gondwana continental crust, the delamination concerned mainly orogen (Fig. 18b). Within the thickened Variscan material in the lower crust. dense (garnet-rich) Age dating et al. (2003) represents the main source of age data for Ulten- study by Tumiati radiometric The excellent Sm-Nd isotope systematic indicate an and garnet-clinopyroxene Nonsberg lower crust. Garnet-whole-rock peridotites, the mafic rocks with eclogite-facies relics and at ca. 330 Ma for the coarse-grained isotopic event obtained by U-Pb dating of zircons from an amphibole-rich contact the migmatites. A similar age of 333 Ma was et al. 2007). The Alta mountain (Tumiati rock between peridotite and migmatites from the Hochwart/Vedetta during the subduction or the melting event represent either the thermal peak of Variscan Visean age may et al. 2003). early exhumation stages (Tumiati 1978). The yielded an U-Pb age of 336 Ma (Gebauer & Grünenfelder, from pyroxenites Zircons separated authors to consider the zircon age as representative of zircons led the above internal planar oscillatory zoning rise to the pyroxenites. that gave of the magmatic event an older age of gneisses (Fig. 19) reveal age dating of monazite from garnet-kyanite Chemical and U-Th-Pb subduction, possibly the pressure peak (Langone et stage of the Variscan 351-343 Ma related to the prograde rock Sm–Nd ages of 351 ± 1 Ma for a 2011). Monazite ages are in agreement with garnet-whole al., ages (292–247 white mica Rb–Sr to Lower Triassic 1994). Permian (Hauzenberger, paragneiss garnet–kyanite to represent cooling ages Ma) were obtained from the migmatites by Del Moro et al. (1993) and are believed ages (205–160 to Jurassic a re-heating stage. Upper Triassic alternatively, soon after the peak conditions or, 1993) and from et al., from migmatites (Hauzenberger on micas separated and Rb–Sr Ma) obtained by K-Ar been interpreted as cooling ages related to 2003). These ages have et al., (Thöni, 1981; Tumiati paragneisses 2005). et al., slow exhumation of the Ulten-Nonsberg crust (Ranalli the relatively lower crust remains an open question. An alternative explanation capable to reconcile the different lower crust remains an open question. An alternative Because the geological field trips 2014 - 6(2.1) excursion notes 27 R. Braga - G. M. Bargossi R. Braga On a whole, the available ages suggest that On a whole, the available the Ulten-Nonsberg crust underwent early- to middle-Carboniferous high-grade metamorphism and partial melting followed decompression at by Permian-Triassic and a final high temperature relatively cooling stage started at the end of and lasted until the Upper Jurassic. Triassic Starting from 330 Ma, the metamorphic et of the UZ peridotite (Tumiati evolution 2003) might be similar to the UZ crustal al., after these rocks were probably evolution tectonically emplaced in the UZ crust. ) a ) all data. From d ) NONS 8, mylonitic Grt-Ky- ) NONS 8, mylonitic b Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust ) NONS 11, white mica-rich Grt-Ky gneiss; ( ) NONS 11, white mica-rich Grt-Ky c Fig. 19 - U-Th-Pb isotopic ages of monazites from three Fig. 19 - U-Th-Pb Langone et al., 2011. Langone et al., representative garnet-kyanite gneiss of the Ulten-Nonsberg crust. ( garnet-kyanite representative NONS 2, biotite-rich Grt-Ky-gneiss; ( NONS 2, biotite-rich Grt-Ky-gneiss; gneiss; ( DOI: 10.3301/GFT.2014.04 geological field trips 2014 - 6(2.1) itinerary 28 R. Braga - G. M. Bargossi R. Braga Itinerary Day 2 itinerary with Stop 2 itinerary Day B) Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Day 1 itinerary and Stop location. The purple dashed 1 itinerary Day A) Fig. 20 - Turistico Le Maddalene – Val di Non. Le Maddalene – Val Turistico line is the road accesible by cars. locations. Cars park at Malga di Mt. d’Ora/Auerbergalm. 1:25.000 published by Consorzio Base map from Carta Turistica DOI: 10.3301/GFT.2014.04 geological field trips 2014 - 6(2.1) itinerary 29 R. Braga - G. M. Bargossi R. Braga Fig. 21 - Block of peridotite showing the coarse- and The hammer is 40 cm long. fine-grained peridotite types of Obata & Morten, 1987. fine-grained Day 1 Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust The garnet-spinel peridotites of the Samerberg area DOI: 10.3301/GFT.2014.04 Starting from Rumo (46°26’31.26” N; 11° 0’59.59” E) by 4-wheel car, take the road SP86 to Proveis/Proves (Fig. 20). Before getting to Proves turn right and enter the Kirchbach valley. After a few hairpin turns, pass the small village of Tal and start to drive on a forest road heading towards Stiebergalm/Malga Manzara (46° 29’ 17” N; 10° 59’ 45” E; alt 1855 m) where the cars ca be parked. Start walking on footpath n.19 until the ruins of Samerbergalm. From this point, move along an ill-defined footpath on moraine hills looking for metre-sized block of ultramafic rocks. Back to Stiebergalm/Malga Manzara and Rumo by the same itinerary. STOP 1.1: The garnet-spinel peridotites of the Samerberg area (WGS84): 46°29’35.10’’ N; 10°59’29.34’’ E Waypoint garnet-spinel-amphibole Porphyroclastic Target: garnetites peridotite and kyanite-bearing peridotite bodies are m-sized In this area, several scattered in glacial deposits. Coarse- and fine-grained peridotite with peridotite (Fig. 21) and porphyroclastic spinel (Fig. 22) can be reddish garnet rimming anhedral type shows, on a fresh The porphyroclastic observed. surface, the 6-phases assemblage typical of Ulten- peridotites: olivine (yellowish Nonsberg garnet-bearing (light with typical vitreous lustre) + orthopyroxene (green) + amphibole (fine- brown) + clinopyroxene dark green) + spinel (dark brown) and garnet grained; dolomite the rare (reddish). This outcrop provided described by Obata & Morten, 1987 and porphyroclasts 2009. Sapienza et al., geological field trips 2014 - 6(2.1) itinerary 30 R. Braga - G. M. Bargossi R. Braga we can look to the western face of Mandelspitz/Mt. Ometto (Fig. 24) showing the pattern of the Ulten- typical structural Nonsberg lower crust. Fig. 23 - Kyanite-bearing garnetite. Andreatta (1936) Fig. 23 - Kyanite-bearing The coin is 24 mm across. named this peculiar rock type “Ultenite” (from Ulten valley). Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Fig. 22 - Peridotite with porphyroclastic texture. Pinkish with porphyroclastic Fig. 22 - Peridotite garnet rims dark brown spinel. DOI: 10.3301/GFT.2014.04 Climbing few meters from the peridotite pods we can find an exposure of a reddish, coarse-grained garnetite Climbing few meters from the peridotite pods we can find an exposure of a reddish, coarse-grained Fig. 23). The exposure is readily recognizable because of the dark reddish to orange (garnet > 90 vol%; biotite and quartz. From this site weathered surface. The garnetite is isotropic, with minor amount of kyanite, geological field trips 2014 - 6(2.1) itinerary 31 S R. Braga - G. M. Bargossi R. Braga Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Fig. 24 - Panorama of the western face of the Mandelpitz/Mt. Ometto. The face’s height is about 250 m. A thick The face’s of the western face Mandelpitz/Mt. Ometto. Fig. 24 - Panorama N structural landmark of the Ulten-Nonsberg lower crust. structural peridotite layer is interleaved between the overlying stromatic migmatites and garnet-kyanite gneisses. This is the stromatic migmatites and garnet-kyanite between the overlying is interleaved peridotite layer DOI: 10.3301/GFT.2014.04 geological field trips 2014 - 6(2.1) itinerary 32 R. Braga - G. M. Bargossi R. Braga Day 2 Peridotites, pyroxenites and migmatites Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust DOI: 10.3301/GFT.2014.04 This is a journey through the Ulten-Nonsberg zone in a superb mountain wilderness. Small rock exposures of This is a journey through the Ulten-Nonsberg zone The walk are the main core of this field trip. peridotites crosscut by garnet-websterites garnet-amphibole on debris track footpaths and unmarked and follows both marked connects the Ulten and Non valleys of a similar is a remake hike area). This daylong Lavazzè deposits (especially around the Seefeldjoch/Passo International Eclogite Conference. September 17, 1993 during the Fourth field trip that took place on Friday, 1993). Martin, Lauro Morten and Giacomo Prosser (Martin et al., the field leader were Silvana In those days Since this itinerary cut the Maddalene Mts., best option is to arrange leave a car at Malga Lavazzè (from Rumo: go to Mocenigo and then turn left into the Lavazzè Valley park car at Malga Lavazzè) use another car to get the Ulten Valley. Start from Rumo by along SP6 towards east. After 4 km, turn left on the SP 86, direction Val d’Ultimo. The two tunnels after 11 km “pierce” Giudicarie fault system, which belong to the Periadriatic lineament dividing Austroalpine and Southern Alps domains. Once in the Ulten Valley (via Nazionale, 22 km from Rumo), turn left towards Sankt Walburg/Santa Valburga and Nikolaus/San Nicolò. At Sankt Nikolaus turn left and take the forest road that climbs Auerbergtal up to Auerberg Alm/Malga di Mt. d’Ora. Here, start walking along the footpath n. 18 (red-white marks) towards Seefeld Alm/Malga Siromba. Within 5-minute walk to the South, Seefeldsee/Siromba Lake can be reached. Time: 6:00 hours Lavazzè Alm to Seefeldjoch/Passo Uphill: 700 m, from Malga di Monte d’Ora/Auerberg to Malga Masa Murada. Lavazzè Downhill: 520 m, from Seefeldjoch/Passo STOP 2.1: The stromatic migmatites of the Ulten Zone (WGS84): 46°26’01.00’’ N; 10°56’47.82’’ E, 2050 m; along the footpath n.18 Waypoint stromatic migmatites Target: outcrops along the footpath n.18. These rocks garnet-biotite-gneiss fine- to medium-grained Massive, (Fig. 25). country rocks geometrically below the peridotite-bearing zone represent the Ulten Zone geological field trips 2014 - 6(2.1) itinerary 33 R. Braga - G. M. Bargossi R. Braga Fig. 25 - Eastern side of the Ulten Zone. the Monte Faggiola made of the Monte Faggiola the stromatic migmatites of Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust DOI: 10.3301/GFT.2014.04 geological field trips 2014 - 6(2.1) itinerary 34 R. Braga - G. M. Bargossi R. Braga Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust DOI: 10.3301/GFT.2014.04 STOP 2.2: Pyroxenitic and peridotites of Seefeld Lake (WGS84): 46°28’39.48” N; 10°56’51.12” E, 2200 m; West Waypoint cutting garnet-amphibole-peridotites Garnet-websterites Target: It consists of light-brown The outcrop (Fig. 26) forms a few meters-high cliff west of the Seefeld/Siromba Lake. (Fig. 27a-b), which shows a late websterite dyke peridotite cut by a 10 to 40 cm-thick green garnet-amphibole oriented at high angle with respect to the lithological contact. The green websterite shows cleavage fracture orthopyroxene centimetres across, Fig. 27b) made of an intergrowth clinopyroxene, megacrysts (several + amphibole garnet ± spinel + clinopyroxene orthopyroxene and garnet set in a medium- to coarse-grained light brown orthopyroxene, clinopyroxene, matrix. On a fresh surface it is easy to recognise green emerald that the matrix dark green amphibole and red garnet. With the aid of a hand lens it is possible to observe and form a mosaic texture. are equigranular minerals defines the ~ 1 mm) and the preferred orientation of minerals size (grain The peridotite is medium-grained is orthopyroxene) foliation. On a fresh cut the peridotite is dark coloured: dull-green olivine (± light-brown (Fig. 27c) form a 40 cm-thick band visible in a dark grey matrix composed of amphibole. Phlogopite flakes be and dark red garnet may occurring at 50 cm below the websterite-peridotite contact. Green clinopyroxene or rounded aggregates of 1-2 cm diameter (Fig. 27d). found as isolated coarse grains Another decametric peridotite lens crops out some 50 m north of the Stop 2.2 (Fig. 28). Here a leucocratic made of plagioclase, quartz and subordinate biotite (trondhjemite) is located between the dyke granular the modal abundance of biotite peridotite. In the trondhjemite dyke, migmatitic gneiss and the overlying the contact with peridotite. increases towards After the Stop 2.2, take an ill-marked track and go up to Seefeldjoch/Passo Lavazzè (2344 m, field trip’s highest point), at the boundary between Ulten ( district) and Non valleys ( district). geological field trips 2014 - 6(2.1) itinerary 35 R. Braga - G. M. Bargossi R. Braga Fig. 26 - Overview of the garnet- Fig. 26 - Overview of the garnet-websterite in Fig. 27. of the garnet-websterite amphibole peridotite west of the Close up views Seefeld/Siromba lake. Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust DOI: 10.3301/GFT.2014.04 geological field trips 2014 - 6(2.1) itinerary 36 R. Braga - G. M. Bargossi R. Braga Large porphyroclast (arrow) in Large porphyroclast Rounded porphyroclast consisting porphyroclast Rounded Phlogopite- bearing domain of the Garnet-websterite dyke (greenish) dyke Garnet-websterite Fig. 27 - Examples of lithological across. and mineral variations in the Stop variations and mineral 2.2, west of Seefeld/Siromba lake. A) intruded in the garnet-amphibole is concordant to peridotite. The dyke the peridotite foliation. B) garnet-websterite; C) peridotite. Phlogopite lamellae have (sub)metallic lustre. Olivine-rich texture and granular domains have Field of view: about 25 cm. ochre colour. D) of an aggregate green clinopyroxene and dark red garnet in foliated peridotite. The coin diameter is 21 mm B D Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust C A DOI: 10.3301/GFT.2014.04 geological field trips 2014 - 6(2.1) itinerary 37 R. Braga - G. M. Bargossi R. Braga Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Fig. 28 - Contact between Seefeld/Siromba Lake area. Seefeld/Siromba Lake peridotite and trondhjemite. DOI: 10.3301/GFT.2014.04 geological field trips 2014 - 6(2.1) itinerary 38 R. Braga - G. M. Bargossi R. Braga B Block of B Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Panorama from the Passo Lavazzè/Seefeldjoch towards the towards Lavazzè/Seefeldjoch from the Passo Panorama A Fig. 29 - stromatic migmatite. Aubergtal. The loose blocks of the debris covering the slope provide the the slope provide Aubergtal. The loose blocks of the debris covering the mesoscopic structures of migmatites. opportunity to observe DOI: 10.3301/GFT.2014.04 STOP 2.3: Nebulitic migmatites Pass. (WGS84): 46°28’5.13” N; 10°56’45.52” E, 2344 m; Seefeldjoch/Lavazzè Waypoint migmatites with trondhjemitic leucosome Nebulitic, coarse-grained Target: (to the of the Ulten Valley (2344 m; Fig. 29A), with the panorama Pass A quick Stop at the Lavazzè/Seefeld (to the south). The mountain peaks at both side of pass (Stubele and north) and the Non Valley down, Siromba/Seefeld Spitz) consist of migmatites with abundant trondhjemitic leucosome. During the way of the migmatite evidence of the variety provide loose blocks throughout the area and along track structures, e.g. the stromatic migmatite of Fig. 29B. From the Seefeldjoch/Lavazzè Pass descend southern slopes of Seefeldspitz/Cima della Siromba Mount. Loose blocks on the track require attention. The will intersect footpath n. 133 (red and with marks), turn right westward to Malga Masa Murada (2046m). geological field trips 2014 - 6(2.1) itinerary 39 R. Braga - G. M. Bargossi R. Braga Fig. 30 - Contact between peridotite (fine-grained type) and migmatite. Fig. 30 - Contact between peridotite (fine-grained Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust DOI: 10.3301/GFT.2014.04 STOP 2.4: Peridotite-migmatite contact Masa Murada (WGS84): 46°27’35.33” N; 10°57’13.50” E, 2036 m; along the footpath n. 133 toward Waypoint (46°27’25.00’’ N; 10°56’57.26’’ E, 2046 m) Contact between amphibole peridotite and country rocks Target: with a light- The decametre-long outcrop shows the contact between peridotite (rocks at footpath level gneissic migmatite with a reddish weathered surface (Fig. 30). brown weathered surface) and the overlying hand sample scale, the medium- to fine- At peridotite (~ 1mm on average) grained shows abundant olivine (dull green to (light brown) and orthopyroxene yellowish), aggregates rare amphibole (dark grey). Very made of dark red garnet and green A occur as porphyroclasts. clinopyroxene occurs in the peridotite phlogopite-rich layer the contact with overlying towards not visible with migmatite. Dolomite grains, are described in samples eye, the naked & Sapienza, 2007). from this outcrop (Braga The peridotite foliation is outlined by the shape-preferred orientation of olivine and This foliation is grains. orthopyroxene to that of the surroundings parallel migmatites, which show a foliation defined and biotite-rich by alternating leucocratic pegmatitic Locally, mm-thick layers. of trondhjemitic composition dykelets crosscut at high angle the migmatite gneissic foliation. geological field trips 2014 - 6(2.1) itinerary 40 R. Braga - G. M. Bargossi R. Braga Fig. 31 - Grain-size and texture variations in the peridotite lense and texture variations Fig. 31 - Grain-size foliated (coin), fine-grained. The coin is 23 mm across. foliated (coin), fine-grained. from the Lago della Poinella. From top to bottom: coarse granular, from the Lago della Poinella. Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust DOI: 10.3301/GFT.2014.04 STOP 2.5 (optional): The Peridotite body of the Poinella lake 46°27’24.00’’ N; 10°56’41.00’’ E, Waypoint: 2140 m asl, just east of the Lago della Poinella and country gneisses cut Peridotite Target: by andesite dykes The peridotite body from the Lago della area (Fig. 20) shows the transition Poinella to the fine-grained from the coarse granular by a foliated is marked types. The transition band of about 5 cm width (Fig. 31). The portion contains elongated coarse granular (Fig. 32A). Locally, pods of orthopyroxenite peridotite shows a clear the fine-grained fabric defined by the preferred orientation of The fabric is further outlined by minerals. (Fig. 32B). layers mm-thick pyroxenite From Malga Masa Murada move southward on the footpath n. 134 to Malga Lavazzè (1639 m) where the cars have been previously parked. Back to Rumo, end of the field trip. geological field trips 2014 - 6(2.1) itinerary 41 R. Braga - G. M. Bargossi R. Braga mm-thick pyroxenite layers concordant with the layers mm-thick pyroxenite B Museo Giardino Geologico “Le Pietre delle Maddalene” Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust Coarse-grained orthopyroxenite pods in granular peridotite. pods in granular orthopyroxenite Coarse-grained A Fig. 32 - main peridotite foliation. Thin (< 1 mm) amphibole-chlorite (?) veins cut at high angle the layering. main peridotite foliation. Thin (< 1 mm) amphibole-chlorite (?) veins AB DOI: 10.3301/GFT.2014.04 In Rumo – The Museo Giardino Geologico “Le Pietre delle Maddalene” In front of the Marcena church there is rock garden (Fig. 33A). The boulders on display are a catalogue of the rock types occurring in surroundings Rumo. (Fig. 33A). The boulders on display Group (Fig. 33B) and the Mesozoic Volcanic Athesian include specimens from the Lower Permian Rocks (Southern Alps) as well the older Austroalpine basement (Fig. 33C) with our beloved sedimentary cover of the boulders mimics neighbouring regional geology (see Fig. 3). peridotites. The arrangement geological field trips 2014 - 6(2.1) itinerary 42 R. Braga - G. M. Bargossi R. Braga Boulder of lapilli-tuff from the Athesian Volcanic Group. Volcanic Boulder of lapilli-tuff from the Athesian B) Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust ABC The church of Marcena and the rock garden. A) Migmatites (in front) and other rock types from the Austroalpine basement. Fig. 33 - C) CKNOWLEDGEMENTS DOI: 10.3301/GFT.2014.04 A Lo Pò in this work. Deborah Colleagues whose efforts are summarized The Authors are indebted to many up this guide. different sources of information that makes help to put in shape the many effective provided the improved and Mauro Roma Maria Letizia Pampaloni Gloria Ciarapica, Helpful comments by Benoît Petri, and Bolzano of Bologna; Trento quality of the submitted manuscript. National (PRIN) and local (University municipality) funds are acknowledged. Rumo Autonomous Provinces; Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust R. Braga - G. M. Bargossi g e o l o g i c a l

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DOI: 10.3301/GFT.2014.04 geological field trips 2014 - 6(2.1) references 44 se rocks e from Italy). e Ulten Eastern n Alps). lian Alps. tive della tive J. Petrol., J. al Regard lia. ROMA, ezia Tridentina, R. Braga - G. M. Bargossi R. Braga �dtirol. Ber. Deutsch. Geol. Wiss. Reihe B, Miner. Lagerstättenf., 16/2, 227-240. Lagerstättenf., Miner. B, Deutsch. Geol. Wiss. Reihe Ber. �dtirol. O content of deep-seated orogenic continental crust: the Ulten Zone, Italian Alps. Int. Geol. Rev., O content of deep-seated orogenic continental crust: the Ulten Zone, 2 Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust �hrender Ultramafitite des Ultentales, Sü Ultramafitite �hrender Carta Geologica d’Italia alla scala 1:50.000. Foglio 026 Appiano. APAT, Dipartimento Difesa del Suolo, Servizio Geologico d’Ita Dipartimento Difesa del Suolo, APAT, 026 Appiano. Carta Geologica d’Italia alla scala 1:50.000. Foglio 184. p. 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(1992) – Major elements, 3d transition De Francesco Bondi M., Ita of inclusions in zircon from high-pressure crustal rocks the Ulten Zone, (2008) - Mineralogy R. & Massonne H.-J. Braga (2012) - H R. & Massonne H.-J. Braga Avanzini M., Bargossi G.M., Borsato A., Castiglioni G.B., Cucato M., Morelli C., Prosser G. & Sapelza A. (2007) – Note illustra Morelli C., Cucato M., Castiglioni G.B., Borsato A., Bargossi G.M., M., Avanzini Andreatta C. (1936) - La formazione gneissico-kinzigitica e le oliviniti di Val d’Ultimo (Alto ). Mem. Mus. Stor. Nat. Ven d’Ultimo (Alto Adige). Mem. Mus. Stor. Andreatta C. (1936) - La formazione gneissico-kinzigitica e le oliviniti di Val References bei der metamorphen Gene in Pyroxenen (1971) – Über orienterte Granatenmischungen F. & Rost Grigel W. Brenneis P., Amthauer G., Hammer W. (1899) - Olivinegesteine aus den Nonsberg, Sulzberg und Ultental. Zeitschr. F. Naturwiss., 72, 1-48. Naturwiss., F. 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Del Moro A., ( complex of the Austroalpine Ulten zone (1993) - Cooling ages from the migmatite–granulite Prosser G. & Martin S. Del Moro A., Braga R., Massonne H.-J. & Morten L. (2007) - An early metamorphic stage for the Variscan Ulten Zone gneiss (NE Italy): evidenc Ulten Zone & Morten L. (2007) - An early metamorphic stage for the Variscan Massonne H.-J. R., Braga Braga R. & Sapienza G.T. (2007) – The retrograde evolution of a dolomite-bearing hydrous peridotite from the Ulten Zone (Italia peridotite from the Ulten Zone of a dolomite-bearing hydrous evolution (2007) – The retrograde R. & Sapienza G.T. Braga geological field trips 2014 - 6(2.1) references 45 . J. n, lution R. Braga - G. M. Bargossi R. Braga evolution of ‘crustal’ garnet peridotites and included pyroxenites from Nonsberg area (Upper of ‘crustal’ garnet peridotites and included pyroxenites evolution Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust P-T Austroalpine), NE Italy: from the wedge to the slab. J. Geodyn., 30, 93-115 Geodyn., J. Austroalpine), NE Italy: from the wedge to slab. 28, 599-623. Petrol., J. crystalline complex, Northern Italy. 4, 19-20. Nova, supplement to Terra Abstract eastern Alps. Terra 42, 207-219. Petrol., Austroalpine, Eastern Alps). J. (eds): Deformation Mechanisms, Rheology and Tectonics: & Cobbold P.R. Brun J.P. Nappe, Eastern Austroalpine. In: Gapais D., 243, 159–174. to the Lithosphere. Geol. Soc. Lond. Spec. Publ., from Minerals Mineral., 106, 775-780. Mineral., 5, 443-466. Pressure Metamorphism. EMU Notes in Mineralogy, Compagnoni R. (eds), Ultrahigh Austroalpine Ulten Zone. Mineral. Petrol., 58, 111–130. Petrol., Mineral. Austroalpine Ulten Zone. 5, 13. Abstracts, Terra, d’Ultimo), Southern Tyrol. the Nonsberg area, Ultental (Val Clapa (Alto Adige, northeastern Italy). Mem. Ist. in the Austridic crystalline basement from Val of a spinel-garnet-lherzolite 30, 3-28. Padova, Geol. Univ. (Italy). Lithos, 127, 68-85. Ulten Zone of the Variscan unshielded monazite from the high-pressure paragneisses 95, 251-272. Petrol., Mineral. in subduction zones. Italy): insights into fluid-rock interaction contact (Ulten Zone, basement rocks from the Nonsberg area. In: Morten L. (Ed) Italian eclogites and related rocks, Accademia Nazionale delle Scritti e Documenti XIII, 237-251. detta dei XL, Roma. Scienze 16, 454-487. Petrol., Acta, 21, 137-144. Petrogr. Miner. Trento. 73, 119-129. Mineral., Period. subduction–exhumation in the Nonsberg–Ultental garnet peridotites (Eastern Alps). A review. DOI: 10.3301/GFT.2014.04 Obata M. & Morten L. (1987) - Transformation of spinel Lherzolite to garnet lherzolite in ultramafic lenses of the Austridic in ultramafic to garnet lherzolite of spinel Lherzolite Obata M. & Morten L. (1987) - Transformation R. & Morten L. (1993) - Nd-isotopic evidence of enriched lithospheric domains: an example from the Nonsberg area, Petrini 313. 12, p. Mitt., Min. Petr. in Tirol. Tscherm. (1891) - Über Granat-Granulit Ploner P.J. (Upper of crustal metasomatism in the garnet peridotites Ulten zone E. & Morten L. (2001) - Records Rampone & Mahatsente R. (2005) - Continental subduction and exhumation: an example from the Ulten Unit, Tonale Martin S. G., Ranalli Morten L. & Trommsdorff V. (2003) - Metamorphism and textures of dry and hydrous garnet peridotites. In: Carswell D. A. & garnet peridotites. In: Carswell D. (2003) - Metamorphism and textures of dry hydrous V. Morten L. & Trommsdorff & Morten L. (2000) - Nimis P. Hauzenberger C.A., Höller W., Hoinkes G., Klözli U. & Thöni M. (1993) - Metamorphic evolution of the Austroalpine basement in & Thöni M. (1993) - Metamorphic evolution Klözli U. G., Hoinkes Höller W., C.A., Hauzenberger evo Piccirillo E.M. & Scolari A. (1977) - Petrogenetic Gregnanin A., Gatto G.O., A., Fornoni Chiesa S., Riccio L., Herzberg C., ages in metamorphic) U–Th–Pb of old (prograde & Tiepolo M. (2011) - Preservation Massonne H.-J. R., Braga Langone A., gneiss-peridotite & Bargossi G.M. (2009) - Metasomatic reaction bands at the Mt. Hochwart P. Tropper Mair V., Marocchi M., and surrounding of the Spl- to Grt-peridotite evolution Morten L. & Prosser G. (1993) – Metamorphic and structural Martin S., from basalts. by xenoliths and fabrics of upper mantle peridotites as illustrated & Nicolas A. (1975) - Textures Mercier J.-C. di No Val di Rumo, (1976-1977) - Notizie preliminari sulle metamorfiti della Val Bargossi G.M. & Landini F. Morten L., processes during continental of mantle–crust exchange E. (2004) - Records & Rampone Nimis P. Morten L., B lenses within garnet peridotite, Northern Italy. origin of pyroxenite high-temperature Morten L. & Obata M. (1983) - Possible Hauzenberger C.A., Höller W. & Hoinkes G. (1996) - Transition from eclogite to amphibolite-facies metamorphism in the G. (1996) - Transition & Hoinkes Höller W. C.A., Hauzenberger geological field trips 2014 - 6(2.1) references 46 n ure -394. 1-46. R. Braga - G. M. Bargossi R. Braga �dtirol. Verhandl. Geol. Reichsanst., p. 287. p. Geol. Reichsanst., Verhandl. �dtirol. �dlich des Ultentales, Provinz Alto Adige (Oberitalien). Tscher. Miner. Alto Adige (Oberitalien). Tscher. des Ultentales, Provinz �dlich Crust-Mantle relationships close at hands - Walking through the Ulten-Nonsberg orogenic lower crust �ber das Vorkommen von Olivingesteine im Sulzberg, Tltentaler Gebirgszug. Verhandl. Geol. R. Olivingesteine im Sulzberg, Tltentaler Gebirgszug. Verhandl. von das Vorkommen �ber Zone): records of subduction metasomatism in the mantle wedge. In: Beltrando M., Peccerillo A., Mattei M., Conticelli S. & Conticelli S. Mattei M., A., Peccerillo M., records of subduction metasomatism in the mantle wedge. In: Beltrando Zone): 36, paper 28, doi: 10.3809/jvirtex.2009.00259. Virtual Explorer, Doglioni C. (eds), J. A. Wien, p. 296. A. Wien, p. 124, 111-174. Geol. B.-A., of K/Ar and Rb/Sr age determinations on micas. Jahrb. Petrog., 25, 257-286. Petrog., 158, 401-420. Petrol., Mineral. Eastern Alps, Italy). Contrib. in a mantle wedge (Ulten Zone, recycling 151, 372 Petrol., Mineral. element and Li abundances. Contrib. Eastern Italian Alps): clues from trace peridotites (Ulten Zone, subducted mélange (Mt. Hochwart, Eastern Italian Alps). Lithos, 94, 148–167. subducted mélange (Mt. Hochwart, 210, 509-526. Earth Planet. Sc. Lett., geochronology and new petrological constraints. Alps (Nonsberg-Ulten zone): DOI: 10.3301/GFT.2014.04 Scambelluri M., Rampone E., Braga R. & Malaspina N. (2010) - The Variscan garnet peridotites from the Eastern Alps (Ulten R. & Malaspina N. (2010) - The Variscan Braga E., Rampone Scambelluri M., Olivingesteine in Sü von Stache G. (1880) - Über das Vorkommen Stache G. (1881) - Neuen Daten ü Thöni M. (1981) – Degree and evolution of the Alpine metamorphism in the Austroalpine unit W of the Hohe Tauern in the light of the Alpine metamorphism in Austroalpine unit W Hohe Tauern Thöni M. (1981) – Degree and evolution (2007) - Fluid-controlled crustal metasomatism within a high press & Monticelli O. Klötzli U. Martin S., Godard G., S., Tumiati Sandberger F. (1866) - Über Olivinfels and die in demselben vorkommende Mineralien. Neues Jahrb. F. Min., 385 pp. Min., F. Neues Jahrb. Mineralien. (1866) - Über Olivinfels and die in demselben vorkommende Sandberger F. R. (2009) - Dolomite-bearing orogenic garnet peridotites witness fluid-mediated carbon Scambelluri M. & Braga Sapienza G.T., fluid-induced metasomatism in spinel to garnet wedge versus E. (2006) - Melt- Morten L. & Rampone Hermann J., Scambelluri M., Rost F. & Brenneis P. (1978) - Die Ultramafitite im Bergzug sü (1978) - Die Ultramafitite & Brenneis P. F. Rost Tumiati S., Thoni M., Nimis P., Martin S. & Mair V. (2003) - Mantle-crust interactions during Variscan subduction in the Easter during Variscan (2003) - Mantle-crust interactions & Mair V. Martin S. Nimis P., Thoni M., S., Tumiati Tumiati S. & Martin S. (2003) – Garnet-peridotite in the Italian Eastern Alps: 150 years of discoveries. Mem. Sci. Geol., 55, 3 Mem. Sci. Geol., of discoveries. in the Italian Eastern Alps: 150 years (2003) – Garnet-peridotite & Martin S. S. Tumiati