Lithos 124 (2011) 308–318

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Mantle xenoliths from Tallante (Betic Cordillera): Insights into the multi-stageevolution of the south Iberian lithosphere

Gianluca Bianchini a,b,⁎, Luigi Beccaluva b, Geoff M. Nowell c, D. Graham Pearson c,d, Franca Siena b

a Istituto di Geoscienze e Georisorse, C.N.R., Via Moruzzi 1, I-56124 Pisa, Italyb Dipartimento di Scienze della Terra, Università di Ferrara, Via Saragat 1, I-44100 Ferrara, Italyc Department of Earth Sciences, Durham University, South Road, Durham DH1 3L, UKd Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E3

⁎ Corresponding author. Istituto di Geoscienze e GeoI-56124 Pisa, Italy.

E-mail addresses: bncglc@unife.it (G. Bianchini).

0024-4937/$ – see front matter © 2010 Elsevier B.V. Adoi:10.1016/j.lithos.2010.12.004

a b s t r a c t

a r t i c l e i n f o

Article history:Received 14 April 2010Accepted 8 December 2010Available online 16 December 2010

Keywords:Betic CordilleraMantle xenolithsMetasomatismLithosphere refertilization

Extreme compositional heterogeneities have been recorded in mantle xenoliths from Tallante, attracting anintense petrological interest that is reflected in the impressive number of scientific studies. In this contributionwe present new isotopic analyses carried out by MC-ICP-MS and TIMS on minerals separated from samplespreviously characterized by Beccaluva et al., 2004 (Lithos 75, 67–87). The new Sr–Nd–Hf isotopic analyses,combinedwith the previously published data, highlight that anhydrous cpx-poor peridotites display enrichmenttrends towards Enriched Mantle (EM) components, related to metasomatic interaction between alkaline meltand a depleted peridotite matrix that sufferedmelt extraction in the garnet stability field. In contrast, anhydrouscpx-rich lherzolites (containing up to 5% plagioclase) cluster around the Depleted Mantle (DM) componentand are possibly related to a pervasive refertilization induced by tholeiitic melts that permeated the Beticlithosphere. These metasomatic reactions possibly occurred during the Mesozoic tectono-magmatic cycle thatultimately led to the opening of the central Atlantic and the westward propagation of the Neotethys rifting andoceanization. Furthermetasomatic reactionswithin the lithosphere occurred in the Neogene, during the Alboranback-arc development in connection with the Betic orogenic event. This cycle is documented by compositeperidotite xenoliths crosscut by plagioclase and orthopyroxene±quartz±phlogopite±amphibole veins thatare characterized by crustal Sr–Nd–Hf isotopic signatures. This indicates hydrous silica-oversaturated melts ascausativemetasomatic agents, in turn implying the recycling – via subduction – of continental crust componentswithin the mantle.

risorse, C.N.R., Via Moruzzi 1,

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© 2010 Elsevier B.V. All rights reserved.

1. Introduction

The geology of the Betic area (Fig. 1) has been characterized byseveral tectono-magmatic phases including both anorogenic andsubduction related volcanic cycles (Benito et al., 1999; Cebriá et al.,2009; Conticelli et al., 2009; Puga et al., 2010, 2011). This evolutioninduced remarkable compositional variation within the underlyinglithospheric mantle. The resulting compositional heterogeneities havebeen recorded by mantle xenoliths from Tallante, which attracted anintense petrological interest reflected in a wide range of scientificstudies (Ancochea and Nixon, 1987; Arai et al., 2003; Beccaluva et al.,2004; Bianchini et al., 2009; Capedri et al., 1989; Coltorti et al., 2007;Dupuy et al., 1986; Kogarko et al., 2001; Martelli et al., 2009; Ramponeet al., 2010; Schaefer et al., 2000; Shimizu et al., 2004, 2008; Turneret al., 1999).

In this contribution we review the existing related literaturediscussing the available Sr–Nd isotope data together with new Nd–Hf

isotopic analyses carried out by MC-ICP-MS on clinopyroxene andplagioclase separated from samples previously studied by Beccaluvaet al. (2004). The new results and the reinterpretation of the previousdata on mantle xenoliths from Tallante are discussed taking intoaccount: a) petrological investigations on magmatic rocks from theBetic area, including those of the Betic Ophiolite Association; and b)insights provided by the neighbouring ultramafic massifs of Rondaand Beni Bousera.

2. Geology

The Betic Cordillera in southern Spain (Fig. 1) is the westernmostbelt of the peri-Mediterranean Alpine orogen formed during theconvergence of the African and Iberian plates, with deformation of theinterposed Alboran microplate (Dewey et al., 1973, 1989; Mauffret etal., 2007; Platt et al., 2006 and references therein). The outcroppingrocks are included in the pre-Alpine units of the basement and in aMesozoic sedimentary sequence deposited on a subsiding riftedmargin evolved since the end of the Hercynian cycle (Barbero andLópez-Garrido, 2006). This post-Hercynian extensional phasefavoured intense magmatic activity (Puga et al., 2010 and references

Fig. 1. Simplified geological sketchmap of the circum-Alboran area. Note that the Gibraltar Arc has two arms represented by the Betic Cordillera of southern Spain and the Rif chain ofnorthern Morocco, which land-locked the Alboran Basin situated in the internal part of the Arc. In particular, the Betic Cordillera of SE Spain is divided in external (Subbetic, andPrebetic) and internal units; the latter are in turn subdivided into three nappe complexes called, from bottom to top Nevado–Filábride, Alpujárride and Maláguide. Widespreadextension-related Triassic and Jurassic magmatism (within plate basalts and dolerites) especially developed in the Subbetic zone, and ophiolitic units are recognized within theNevado–Filábride complex.

309G. Bianchini et al. / Lithos 124 (2011) 308–318

therein) and ultimately led to continental break up and formationof the Betic sector of the Neotethys ocean, currently reflected as theBetic Ophiolite Association (BOA; Puga et al., 2005, 2009, 2011).Subsequent orogenic processes started with the Cretaceous eo-alpinecycle attested by U–Pb dating on zircon from eclogites and blueschists(Puga, 2005; Puga et al., 2005). Convergence continued with neo-alpine episodes of Early Miocene age that are documented by Lu–Hfdating on eclogites and schists (Platt et al., 2006), although thepolarity of the subduction processes is still debated and controversial(Doblas et al., 2007). A more detailed introduction on the geology ofthe area, including description of the geological units and timing ofthe geodynamic events, is reported in Puga et al. (2011).

Cenozoic volcanism mainly occurred during the post-collisionalextensional phase in which low-angle faulting induced the formationof Neogene to Quaternary sedimentary basins where the SE VolcanicProvince of Spain developed (SEVP; Benito et al., 1999; Cebriá et al.,2009; Turner et al., 1999). The volcanic events included tholeiiticproducts (e.g. the Malaga dykes) showing radiometric ages between34 and 17 m.y. (Turner et al., 1999; Duggen et al., 2004), followedby calc-alkaline (e.g. Cabo de Gata) and high-K calc-alkaline (e.g. ElHoyazo, Mazarron, and Mar Menor) products erupted between 15and 6 m.y., as well as shoshonitic (e.g. Cartagena, Vera, Mazarron)and ultrapotassic volcanics (e.g. Cartagena, Fortuna, Vera and Jumillalamproites) erupted between 12 and 6 m.y. (Benito et al., 1999;Conticelli et al., 2009; Duggen et al., 2004, 2005). Petrological studiesof the erupted magmas indicate progressive evolution of the relatedmantle sources induced by a long and complex history involvingsubduction of oceanic lithosphere followed by continental collisionand recycling of crustal components back in the mantle. Following aquiescence of approximately 4 m.y., volcanic activity resumed in theLate Pliocene. This magmatic phase was characterized by Na-alkaline

basalts, producing the volcanic centre of Cabezo Negro at Tallante(Fig. 1) with its abundant mantle xenoliths content.

3. Mantle rocks from Tallante

A remarkable collection of mantle xenoliths (approximately 300samples) from the volcano of Tallante has been progressively acquiredduring 5 distinct field missions. Thin section investigation and bulkrock XRF analysis of 40 selected samples (Beccaluva et al., 2004)provided the base for the following classification:

1) protogranular anhydrous spinel (spl)-peridotites, including clino-pyroxene (cpx)-rich lherzolites that often contain plagioclase (pl,up to 5%) and more refractory cpx-poor (b7%) lherzolites andharzburgites. As observed by Capedri et al. (1989), these xenolithsare sometime characterized by deformed lens-shaped portions(elongated pods) mainly composed of plagioclase.

2) amphibole (amph)-/phlogopite (phl)-bearing harzburgites andorthopyroxenites crosscut by gabbronorite/diorite veins – up to4 cm thick – and millimetric gabbronorite/anorthosite veinlets.Similar xenoliths were already recognized in the papers ofAncochea and Nixon (1987) and Dupuy et al. (1986); the felsicveinlets, characterized by sharp contacts with the peridotite hostrock and typically mantled by orthopyroxene (opx) weredescribed by Arai et al. (2003), Beccaluva et al. (2004), Capedriet al. (1989), Rampone et al. (2010) and Shimizu et al. (2004,2008)

3) amph/phl-bearing clinopyroxenite xenoliths showing magmatictextures, usually referred as group II according to Frey and Prinz(1978). Other xenoliths are “composite” in the sense of Irving(1980) with protogranular peridotite crosscut by amph/phl-

310 G. Bianchini et al. / Lithos 124 (2011) 308–318

bearing clinopyroxenite veins up to 10 cm thick. Analogousxenoliths were described, reporting pictures of hand-specimensand thin sections, by Ancochea and Nixon (1987).

3.1. Mineral chemistry

1) Microprobe analyses provided by Beccaluva et al. (2004), Kogarkoet al. (2001), Rampone et al. (2010) and Shimizu et al. (2004,2008)indicate that minerals of anhydrous peridotites are generallyhomogeneous within individual crystals. Olivine (ol) is character-ized by Fo content between 88.9 and 91.6. Orthopyroxene exhibitsMg# 89.5–92.6, Al2O3 2.6–5.8 and Cr2O3 0.2–0.6 wt.%; clinopyrox-ene is diopsidic displaying Mg# 91.2–93.2, Al2O3 3.2–6.6, Cr2O3

0.6–1.4, TiO2 0.1–1.0, and Na2O 0.5–1.4 wt.%; marginal zones ofpyroxenes (70–120 μm), although unzoned in terms of Mg# andCaO/MgO ratio, are characterized by decreasing Al and Cr contents(Kogarko et al., 2001). Calculations of equilibration temperature ofxenoliths from Tallante, using the conventional two-pyroxenegeothermometer of Brey and Köhler (1990), have been performedby Beccaluva et al. (2004), Kogarko et al. (2001), Rampone et al.(2010), and Shimizu et al. (2008), which obtained temperatures inthe range of 830–1000 °C. The coexistence of spinel (Mg# 75.5–80.5 and Cr# 14.2–27.4) and plagioclase (mainly An 45.9–75.1)suggests equilibration pressure close to 0.7–0.9 GPa (Borghini etal., 2010).

2) Composition of mineral phases in amph-/phl-bearing harzburgitesand orthopyroxenites crosscut by anorthosite, gabbronorite anddiorite veins and veinlets have been reported by Arai et al. (2003),Beccaluva et al. (2004) and Shimizu et al. (2004, 2008). In theperidotite domains olivine has Fo 89.2–90.5; orthopyroxene ischaracterized by Mg# 90.0–91.5, Al2O3 2.1–4.7 and Cr2O3 0.3–0.7 wt.%; clinopyroxene is diopsidic with Mg# 92.3–93.3, Al2O3

4.1–6.5, Cr2O3 0.8–1.1, TiO2 0.3–1.0, and Na2O 0.5–0.9 wt.%. Thetwo-pyroxene geothermometer of Brey and Köhler (1990) appliedto harzburgite TL23 of Beccaluva et al. (2004) and to the peridotiteportion of sample CNT131 of Shimizu et al. (2008) suggestsequilibration temperatures between 940 and 1030 °C. As de-scribed earlier the coexistence in equilibrated peridotite para-geneses of spinel (Mg# 71.9–80.9 and Cr# 11.8–31.6) andplagioclase (mainly An 49.2–57.6) supports equilibration pressureclose to 0.7–0.9 GPa (Borghini et al., 2010).In the felsic veins and veinlets minerals are often zoned.Orthopyroxene is characterized by Mg# 86.3–91.6, Al2O3 0.8–4.4and Cr2O3 0.0–0.7 wt.%, plagioclase by An 47.6–78.2, and pargasiticamphibole by Mg# 85.4–91.2, Al2O3 14.0–16.3, Cr2O3 0.1–1.8, TiO2

0.9–1.4, Na2O 2.5–3.1 and K2O 0.0–1.0 wt.%. This mineral assem-blage permits the application of the amph–pl thermometry(Holland and Blundy, 1994) that constrains the temperature ofthe veining event as more than 850 °C. The modal presence ofphlogopite (Mg# 88.1–93.1 and TiO2 1.0–2.2), quartz and glassypatches with dacite composition were also reported by Arai et al.(2003) and Shimizu et al. (2004). Further accessory phases arerepresented by apatite, huttonite, rutile, and zircon (Bianchini etal., 2009; Shimizu et al., 2004).

3) Composition of mineral phases in amph/ph-bearing clinopyrox-enite xenoliths (goup II of Frey and Prinz, 1978) and in amph/ph-bearing clinopyroxenite veins crosscutting protogranular perido-tite of composite xenoliths is reported by Capedri et al. (1989),Rampone et al. (2010) and Shimizu et al. (2004). Olivine ischaracterized by Fo content down to 74.9; clinopyroxene ranges incomposition from diopside to augite displaying Mg# down to 80.4,Al2O3 3.3–5.3, Cr2O3 0.3–1.0, TiO2 0.5–1.0, and Na2O 0.2–1.1 wt.%;amphibole displays pargasite to kaersutite composition with Mg#down to 0.73, Al2O3 12.7–15.1, Cr2O3 0.0–1.3, TiO2 1.5–4.8, Na2O1.8–3.1 and K2O 0.9–1.6 wt.%; phlogopite has Mg# down to 77.7

and TiO2 3.7–5.2 wt.%. Glassy patches with basanite to trachybasaltcomposition have also been recorded (Authors' unpublished data).

3.2. Bulk rock major element data

1) Bulk rock analyses of anhydrous peridotites (Beccaluva et al.,2004; Dupuy et al., 1986; Turner et al., 1999) indicate variousdegree of “fertility”. Cpx (pl)-rich lherzolites show compositionsimilar to the Primitive Upper Mantle estimates (Pearson et al.,2003 and references therein). Taking into consideration the entiresample population, the content of elements classically consideredindicators of mantle depletion by melt extraction, i.e. CaO (0.9–3.2 wt.%), Al2O3 (0.6–3.9 wt.%), TiO2 (0.02–0.13 wt.%) decreasewith increasingMgO (38.9–45.8 wt.%) andNi (1690–2390 ppm) inthe most refractory parageneses.

2) Bulk rock analyses of amph-/phl-bearing harzburgites and ortho-pyroxenites (Beccaluva et al., 2004; Dupuy et al., 1986) areenriched in SiO2 (up to 49.2 wt.%) thus reflecting the higher modalabundance of orthopyroxene and the presence of felsic veinletsmade of pl±quartz±opx±amph±phl. The bulk rock composi-tion of these veinlets reveals SiO2 content between 46.5 and62.9 wt.%, Na2O between 1.0 and 3.6 wt.%, K2O between 0.3 and0.67 wt.%, and a silica-oversaturated affinity (Arai et al., 2003;Beccaluva et al., 2004).

3) Bulk rock analyses of amph/phl-bearing clinopyroxenite xenolithsand analogous veins of composite xenoliths, reported by Dupuy etal. (1986) and Turner et al. (1999), display SiO2 between 46.0 and49.3 wt.%, Na2O between 1.0 and 3.3%, K2O between 0.3 and 2.5%,showing a remarkable similarity with the host (silica-undersatu-rated) alkaline basalts.

3.3. Rare earth elements (REE) distribution

1) As reported by Beccaluva et al. (2004), REE bulk rock distributionin anhydrous cpx-rich (pl-bearing) lherzolites (Fig. 2a) showsalmost-flat heavy (H)REE patterns (0.8–2.3* chondrite) withvariable Light (L)REE depletion (LaN/YbN=0.9–0.47). Similarresults were recorded by Dupuy et al. (1986) and Turner et al.(1999), showing compositional analogies with lherzolites of theExternal Liguride ophiolites (Rampone et al., 1995 and referencestherein). More refractory anhydrous lherzolites (cpxb7%) andharzburgites display comparatively lower HREE contents (down to0.3* chondrite) and variable LREE enrichment (LaN/YbN up to 4.3).REE distribution for clinopyroxenes of anhydrous cpx-rich lherzo-lites (Beccaluva et al., 2004), displays high HREE contents (up to19* chondrite) and variable LREE depletions (LaN/YbN down to0.3), conforming to the results reported for other Tallantelherzolite xenoliths by Rampone et al. (2010). Note that thesecpx REE patterns display close analogies with those recorded inlherzolites of the External Liguride and Eastern Central Alpsophiolites (Müntener et al., 2004; Rampone et al., 1995).Clinopyroxene of Tallante cpx-poor lherzolites and harzburgitesdisplay lower HREE contents (down to 6* chondrite) and slightLREE enrichments (LaN/YbN up to 2).

2) As reported by Beccaluva et al. (2004), the bulk rock REE contentsof amph/phl-bearing harzburgites and olivine–orthopyroxenitescrosscut by felsic veinlets show patterns characterized by upwardconvex Middle (M)REE with strong negative Eu anomalies (Fig.2b). The same patterns also characterize their constituentpyroxenes. The associated gabbronorite veinlets display LREEenrichments (LaN/YbN up to 19.5), as previously reported byDupuy et al. (1986). Amphiboles within this group of samples areLREE enriched; taking into consideration a complete spectrum oftrace elements, they show a suprasubduction affinity (i.e. they aredepleted in Nb, with suprachondritic Ti/Nb and Zr/Nb) as definedby Coltorti et al. (2007).

Cpx-poor

a

LiguridePeridotites

Anhydrous Peridotites

Cpx-rich

10

1

Roc

k/C

hond

rite

Quartz-diorite veinEu

Amph/Phl-bearing anorthosite andgabbronorite veinlets

Amph-bearing orthopyroxenite

Amph-bearing harzburgite

100

10

1

Roc

k/C

hond

rite

b

cAmph/Phl bearing clinopyroxenite veins

Host basalt

Country-rock peridotite

Roc

k/C

hond

rite

100

10

LuYbTmErHoDy TbGdEuSmNdPrCeLa

LuYbTmErHoDy TbGdEuSmNdPrCeLa

LuYbTmErHoDy TbGdEuSmNdPrCeLa

Fig. 2. Chondrite-normalized (McDonough and Sun, 1995) bulk rock REE distribution inmantle xenoliths from Tallante. a) Anhydrous spl-peridotites including cpx-rich (pl-bearing) lherzolites as empty circles and cpx-poor lherzolites/harzburgites as filledcircles (data from Beccaluva et al., 2004). Ophiolite peridotites from the Apennines(External Ligurides; Rampone et al., 1995) are reported as grey field for comparison. b)Amph-bearing harzburgites and orthopyroxenites and crosscutting felsic veinletsmainly made of plagioclase±quartz±orthopyroxene±amphibole/phlogopite. Datafrom Beccaluva et al. (2004), Dupuy et al. (1986), Shimizu et al. (2004). c) Compositexenoliths in which the peridotite matrix is crosscut by amph/phl-bearing clinopyrox-enite (authors' unpublished data).

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3) Bulk rock rare earth distribution of amph/phl-bearing clinopyrox-enite xenoliths (and analogous clinopyroxenite veins of compositexenoliths) displays a remarkable LREE enrichment (LaN/YbN up to24) very similar to the composition of the host alkaline basalts(Fig. 2c). This enrichment in the most incompatible elementsgradually vanishes in the surrounding peridotite country rock(Dupuy et al., 1986). REE patterns of constituent clinopyroxeneand amphibole (Rampone et al., 2010) resemble those typical ofalkaline rocks. The amphibole trace element composition shows an

intraplate affinity (e.g. enrichement in Nb, with subchondritic Ti/Nb and Zr/Nb ratios) as defined by Coltorti et al. (2007). Theseveins, representing high-pressure cumulates from basic alkalinemelts which are closely related to the host basalts, will not bediscussed in the next sections.

3.4. Description of key samples: insights on melt/rock interaction

A sub-set of the described samples was selected for furtherinvestigation. Key samples include very “fertile” anhydrous spl-lherzolites containing up to 12% of clinopyroxene and more“refractory” anhydrous spl-lherzolites/harzburgites (cpx down to4%). The selected rocks have a protogranular texture, sometimesshowing elongated iso-oriented clusters of spinel+pyroxene (e.g.sample TL16). It is significant that the more fertile cpx-rich spl-lherzolites contain up to 5% of plagioclase. Evidence of in-situ spinel/plagioclase re-equilibration has been observed in some samples (e.g.in sample TL45; Fig. 3a and b). However, the interstitial plagioclasewidespread throughout the peridotite matrix (Fig. 3c), texturally farfrom spinel crystals, and exceeding the “normal” modal abundanceexpected for these accessory phases (1–2%; Pearson et al., 2003) hasto be interpreted as the result of melt impregnation and refertiliza-tion. An additional patent metasomatic feature in these rocks is theoccasional record of pyroxene replacement of olivine manifested asrounded, “resorbed” olivine grains enclosed by pyroxene (Fig. 3d).These petrographical evidences of peridotite/melt interaction aresimilar to those recognized in the peridotites bodies from theNorthern Apennine, Western Alps and Corsica (Borghini et al., 2007;Piccardo and Vissers, 2007; Piccardo et al., 2007; Rampone et al.,1997).

Further evidence of refertilization processes in the Tallanteperidotites is the occurrence of “gabbroic pods”. Sample TL196displays a deformed centimetre-size pod of plagioclase within aprevalent peridotite matrix. This gabbroic pod does not crosscut theentire xenolith and progressively pinch out, without reaction borderswith the surrounding peridotite (Fig. 4). Such occurrence representsmelt infiltration and percolation through the peridotite matrix and itssubsequent coalescence, focusing and channelling at shallowermantle levels.

As mentioned earlier, ultramafic xenoliths from Tallante alsoinclude rocks relatively enriched in orthopyroxene that containamphibole and/or phlogopite, often crosscut by felsic veinlets. Tohave a representative picture of the Tallante xenolith suite we alsoselected for further investigation the composite xenolith TL5 (Fig. 5)that contains a vein of plagioclase and orthopyroxene, amphibole andphlogopite crosscutting the peridotite matrix (Beccaluva et al., 2004).

4. Analytical methods

The isotope compositions of Sr were measured, by ThermalIonization Mass Spectrometry (TIMS) with a Finnigan MAT 262 Vmulticollector mass spectrometer at the CNR Istituto di Geoscienze eGeorisorse in Pisa, after preliminary chemical preparation of thesamples by conventional ion exchange methods. Measured 87Sr/86Srratios were normalized to 86Sr/88Sr=0.1194; replicatemeasurementsof NIST SRM 987 (SrCO3) standard gave values of 0.710252±13 (2σ,n=22).

The Hf and Nd isotope compositions of clinopyroxene (andplagioclase) separates (~100 mg) were measured at the Departmentof Earth Sciences, Durham University. After leaching (6N HCl, 30 min)and sample dissolution, pre-concentrationwas performed using a twocolumn procedure that employed a 5 ml cation separation as the firststep, using 1N HF-1N HCl to elute Hf and 6N HCl to elute Nd, followedby a mixed sulphuric acid-H2O2 anion column for final purification ofthe Hf (Dowall et al., 2003). Measurements of samples and standards(JMC-475 and J&M) were made by MC-ICP-MS on a ThermoFinnigan

Fig. 3. Microphotographs of cpx (pl)-rich lherzolites, showing subsolidus transformation of spinel in plagioclase (a and b); impregnation textures with development of interstitialplagioclase within the peridotite matrix; (c) record of pyroxene replacement of olivine manifest as rounded, “resorbed”, olivine grains enclosed by pyroxene (d).

312 G. Bianchini et al. / Lithos 124 (2011) 308–318

Neptune plasma ionization multicollector mass spectrometer, withprecision and accuracy better than 0.001% (Pearson and Nowell,2005). During the analytical sessions, the average value of the J&M Ndstandard was 0.511097+/−0.000012 (2σ, n=12), the average valueof the JMC-475 Hf standard was 0.282143+/−0.000008 (2σ, n=8).Errors on the sample analyses were generally better than +/−0.00003 (2σ). A higher error of +/−0.000107 characterized theHf isotopic analysis of plagioclase from sample TL5.

5. Sr–Nd–Hf isotopic composition of mantle rocks from Tallante

5.1. TIMS isotopic analyses of Strontium and Neodymium

TIMS Sr–Nd isotopic analyses, mainly carried out on clinopyroxeneand plagioclase separates, were reported by Beccaluva et al. (2004).Anhydrous mantle xenoliths display values in the range 87Sr/86Sr0.70213–0.70476 and 143Nd/144Nd 0.51250–0.51339. Significantdifferences can be observed within the sample population; anhydrouscpx-poor lherzolites and harzburgites display 87Sr/86Sr 0.70290–0.70476 and 143Nd/144Nd 0.51250–0.51305, whereas anhydrous cpx-rich lherzolites show 87Sr/86Sr 0.70213–0.70351 and 143Nd/144Nd0.51297–0.51339. A new Sr isotopic analysis has been carried out onplagioclase crystals separated from a “gabbroic pod” within theanhydrous lherzolite TL196 (Fig. 4). The resulting value, 87Sr/86Sr=0.70323, is included in the compositional spectrum describedearlier. A similar isotopic fingerprint, varying between DepletedMantle (DM) and Enriched Mantle (EM) components, is recorded inmantle xenoliths from several Cenozoic European volcanic districts(e.g. in Sardinia and Massif Central) and in some Alpine-type

peridotite massifs such as Lherz, Lanzo, and Ronda (Beccaluva et al.,2001 and references therein; Downes, 2001 and references therein).

Amph/phl-bearing harzburgites and olivine–orthopyroxenitesdisplay distinct isotopic features with 87Sr/86Sr 0.70672–0.70856and 143Nd/144Nd 0.51211–0.51213. This peculiar isotopic compositionof opx-rich hydrous xenoliths is exotic in mantle rocks entrained inanorogenic basic magmas, particularly from the circum-Mediterra-nean region.

5.2. MC-ICP-MS isotopic analyses of Neodymium and Hafnium

The new Hf and Nd isotope compositions of clinopyroxeneseparates (Table 1), measured by MC-ICP-MS, show that: a) cpx-rich plagioclase-bearing lherzolites (TL14, TL20, and TL45) arecharacterized by 143Nd/144Nd ranging between 0.51311 and 0.51335(εNd 9.2–13.8), 176Hf/177Hf between 0.28316 and 0.28343 (εHf 13.9–23.4); b) cpx-poor lherzolites and harzburgites (TL1, TL16, and TL24)are characterized by 143Nd/144Nd ranging between 0.51248 and0.51284 (εNd −3.1–3.8), 176Hf/177Hf between 0.28294 and 0.28452(εHf 6.1–61.8); c) plagioclase of the felsic vein crosscutting thecomposite xenolith TL5 is characterized by 143Nd/144Nd=0.51245(εNd=−3.6) and 176Hf/177Hf=0.28196 (εHf=−28.7). Theseresults, together with the composition of the notional mantle end-members (Salters and White, 1998), are plotted in the Hf–Nd isotopicdiagram of Fig. 6.

Cpx-rich pl-bearing lherzolites have Hf–Nd composition approach-ing the DM component. This could indicate that the related mantledomain was affected by ancient melt extraction, with preferentialdepletion of highly incompatible trace elements such as Nd and Hf(respect to Sm and Lu) and consequent increase of the Sm/Nd and Lu/Hf

Fig. 4. A plagioclase pod within the lherzolite xenolith TL196.

Fig. 5. Felsic veinlet in xenolith TL5 consisting in a fine intergrowth of plagioclase andorthopyroxene, with minor amounts of amphibole and phlogopite.

Table 1Nd–Hf isotope composition of clinopyroxene (cpx) and plagioclase (pl) separates fromTallante mantle xenoliths.

Sample 143Nd/144Nd 2σ εNd 176Hf/177Hf 2σ εHf

Anhydrous cpx-poor lherzolites and harzburgitesTL1 cpx 0.512801±23 3.18 0.283348±10 20.48TL16 cpx 0.512835±33 3.84 0.284516±26 61.78TL24 cpx 0.512481±28 −3.06 0.282942±8 6.12

Anhydrous cpx (pl)-rich lherzolitesTL14 cpx 0.513347±16 13.83 0.283430±12 23.38TL20 cpx 0.513115±16 9.30 0.283202±12 15.31TL45 cpx 0.513108±26 9.17 0.283163±7 13.93

Felsic vein (pl and opx, amph, phl) of a composite xenolithTL5 pl 0.512452±23 −3.63 0.281958±107 −28.68

313G. Bianchini et al. / Lithos 124 (2011) 308–318

ratios, ultimately resulting in comparatively higher suprachondrite143Nd/144Nd and 176Hf/177Hf ratios. However, considering the extreme“fertility” of these lherzolites containing up to 5% of interstitialplagioclase (and texture reflecting a significant fraction of trappedmelt) we interpret these isotopic values as result of a pervasiveinteraction with MORB (Mid Ocean Ridge Basalt)-type melts(εHf=11.3–20.0; εNd=8.4–12.2; Nowell et al., 1998; Salters andWhite, 1998).

Cpx-poor lherzolites and harzburgites display values ranging fromthose of sample TL16 that is characterized by an extremely high 176Hf/177Hf (εHf=61.8, εNd=3.8) to those of samples TL1 and TL24 thattend towards the notional EM compositions (εHf down to −9; εNddown to −7.5 Nowell et al., 1998; Salters and White, 1998)suggesting metasomatic processes induced by OIB (Oceanic IslandBasalts)-type metasomatic melts.

On the other hand, the plagioclase from the felsic veinlet ofcomposite sample TL5 displays a totally different signature (εHf=−28.7; εNd=−3.6) characterized by a “crustal” fingerprint, plausi-bly related to recycling of continental crust material in the mantle viasubduction. This Hf isotopic value, representing the least radiogeniccomposition ever reported in literature for mantle lithologies.

Further information can be provided by the ΔHf parameter definedby Johnson and Beard (1993), which indicates the displacement ofthese isotopic values from the mantle array defined by OIB magmas(εHfOIB=1.36 εNdOIB+1.63). TL5 is characterized by an extremely

negative ΔHf (−26.7) indicating that the subducted lithologiesbeneath the Betic region included terrigenous (zircon-bearing)sediments, or real chunks of felsic continental crust (van de Flierdtet al., 2007; Vervoort et al., 1999). Similar geochemical componentscharacterized by subchondritic Hf and Nd isotopic compositions havebeen also identified in the genesis of the Spanish Cenozoic lamproitemagmas (Nowell et al., 2008; Prelević et al., 2010).

6. Inferences on mantle processes

The Lu–Hf isotopic system is less influenced by metasomaticprocesses than the Rb–Sr and Sm–Nd ones and should preserve abetter record of mantle depletion events. Model ages of the mostradiogenic Hf composition (sample TL16) are 1.28 Ga with respect to

0.2815

0.2820

0.2825

0.2830

0.2835

0.2840

0.2845

0.5122 0.5124 0.5126 0.5128 0.5130 0.5132 0.5134

Olot Lherzolites Olot Harzburgites Calatrava Lherzolites Sardinia Peridotites

Tallante cpx (pl)-rich lherzolites Tallante cpx poor peridotites Tallante-felsic vein

effect of ancient partial meltingwith persistence of garnet in the

residual paragenesis?

UC

CHUR

CHUR

TL20 TL45

TL14

TL16

TL1

TL24

DM

HIMU

EM2

EM1

pl+opx+amph+phl veinIn composite xenolith TL5

143Nd144Nd

176Hf177Hf

Fig. 6. Hf vs Nd isotope composition of mantle xenoliths from Tallante. Data on mantlexenoliths from other Spanish occurrences and from Sardinia (Bianchini et al., 2007;2010) are reported for comparison. Mantle end-members (DM, HIMU, EMI, and EMII)and Upper Crust (UC) composition are from Salters and White (1998, and referencestherein).

314 G. Bianchini et al. / Lithos 124 (2011) 308–318

the Depleted Mantle and 1.60 Ga with respect to the ChondriteUniform Reservoir (CHUR). Similar Middle Proterozoic model ages arecommon in mantle peridotite xenoliths from other European volcanicdistricts as well as in the Ronda and Pyrenean ultramafic massifs(Beccaluva et al., 2001; Bianchini et al., 2007; Downes, 2001). Theseages are usually interpreted as the time in which the related mantlematerial left the convective asthenosphere and became incorporatedinto the lithosphere.

The highly radiogenic Hf isotope composition of TL16 contrastswith its relatively low Nd isotopic composition, as reflected byΔHf=56.3, which indicates that the two isotopic systems have beendecoupled. A very radiogenic Hf isotopic signature may result fromancient melt extraction in the presence of residual garnet, andconsequent fractionation of the Lu–Hf system (TL16 is characterizedby a very high Lu/Hf ratio in both whole rock and cpx), whichultimately leads to a very radiogenic 176Hf/177Hf composition(Johnson and Beard, 1993; Salters and White, 1998). A similarinterpretation has been proposed for mantle xenoliths from theFrench Massif Central and the Spanish volcanic district of Olot(Bianchini et al., 2007; Downes et al., 2003). Further explanation forthe decoupling of the Sm–Nd and Lu–Hf isotopic systems in mantlerocks is provided by Bedini et al. (2004) which suggests that diffusionloss of radiogenic Nd daughter products is faster than that of Hfdaughter products at mantle temperatures, leading to the develop-ment of anomalously high εHf at a given εNd value. Alternatively, suchdecoupled Hf–Nd isotope systematics could result from metasomaticinteractions with high Nd, low Hf melts, where the Nd isotopecomposition of the cpx is dominated by the composition of the melt,even at very lowmelt/rock ratios. A combination of all these processescan also generate the same effect.

Three main tectonomagmatic events seem to be recorded in themantle xenoliths from Tallante:

1) Evidence of subsolidus decompression is provided by samplescontaining unmixing lamellae in pyroxenes, and sometimes rutileneedles in orthopyroxene, as well as by microtextures indicatingthe former presence of garnet, i.e. symplectites of spinel andpyroxene (Rampone et al., 2010; Shimizu et al., 2008). Similarclusters of spinel and pyroxene resulting from garnet break-downand subsequent deformation during mantle creep processes arerecognized within our sample collection, e.g. in sample TL16. Note

that in the same sample the extremely high 176Hf/177Hf coupledwith high Lu/Hf of both clinopyroxene and whole rock suggests anearly petrological evolution within the garnet stability field.Mantle decompression processes are also recorded in samplescharacterized by spinel break-down and in-situ plagioclase growth(Fig. 3a and b) as well as by zoned pyroxene rims where Al, Cr, andTi decrease (Kogarko et al., 2001) indicating continued mantleuplift up to pressures of 0.7–0.9 GPa (Borghini et al., 2010), whichis in agreement with crustal thickness of ca 20 km (Banda et al.,1993; Torne et al., 2000).

2) Mantle diapirism was coupled with melt/peridotite matrixinteraction, resulting in a range of interaction styles, from crypticmetasomatic enrichments that characterize the cpx-poor perido-tites, to pervasive impregnation, annealing recrystallization andrefertilization indicated by cpx-rich (pl-bearing) lherzolites. Anextreme manifestation of these processes is evident in sampleTL196, which contains centimetre-sized plagioclase segregationzones (Fig. 4).Inferences on the nature of the percolatingmelts moved by porousflow in the Tallante peridotite domains can be obtained from thetrace element content of the clinopyroxene using melt/cpxperidotite coefficients from literature. Assuming equilibriumbetween cpx and the metasomatising melt and using partitioncoefficients from Lee et al. (2007) we calculated the theoreticalREE composition of the interacting melts reported in Fig. 7. Thisfigure also shows, for comparison, patterns of real magmatic rocksfrom the Betic Region. Cpx-rich (pl-bearing) lherzolites reflectinteraction with melts characterized by slightly fractionated REEpatterns (HREE 12–16* chondrite; LaN/YbN 3–5) that resemblethose of Enriched MORB tholeiites; metasomatic processesplausibly occurred at high melt/matrix ratio causing modalvariations and a bulk rock refertilization. In turn, clinopyroxeneof cpx-poor peridotites equilibrated with metasomatic agentscharacterized by highly fractionated LREE-enriched patterns(HREE 5–8* chondrite; LaN/YbN 13–21) that resemble thosetypical of OIB alkaline melts. In this case, we record only “cryptic”enrichments indicating that metasomatic processes occurred atlow melt/matrix ratio.Further constraints on the nature of the refertilizing melts areprovided by the Sr–Nd–Hf isotope compositions of the cpx, whichare dominantly influenced by the interacting metasomatic melts.These isotopic compositions support an anorogenic affinityvariable from MORB to OIB signatures.The refertilization hypothesis is also compatible with the osmiumisotope data provided by Schaefer et al. (2000), as lherzolitexenoliths from Tallante are displaced from the 187Re/188Os vs.187Os/188Os array of the Iberian sublithospheric mantle defined byperidotites from Ronda and the Pyrenean belt (Reisberg andLorand, 1995). The recorded suprachondrite 187Os/188Os values(0.129–0.13) which are unrelated with 187Re/188Os ratios showthat the Re–Os system has been perturbed, indicating thatdepletion by partial melting is not the only process producingthe observed variations, corroborating an interaction with amagmatic component. Significantly, an analogous Re–Os finger-print characterizes abyssal peridotites (Büchl and Snow, 2003)and ophiolitic (Tethyan) peridotites (van Acken et al., 2008),which are interpreted as mantle domains percolated and referti-lized by MORB magmas.

3) Finally, veining events that affected the upliftedmantle domain aretestified by composite xenoliths in which felsic veins crosscut theperidotitematrix generating orthopyroxene-rich reaction zones. Inthis case, the channelled melts were characterized by hydrous andsilica over-saturated compositions, generating a plagioclase±quartz and orthopyroxene±amphibole±phlogopite paragenesessimilar to that recorded in the composite sample TL5. Thesemetasomatizingmelts display 87Sr/86Sr up to 0.70856, 143Nd/144Nd

Ce Pr NdSmEu Gd Tb Dy Ho Er TmYb

100

10

10

10

10

100

La Lu

Cpx/Chondrite

Cpx/Chondrite

Cpx/Chondrite

Clinopyroxenes of anhydrouscpx (pl)-rich lherzolites

Clinopyroxenes of anhydrousharzburgites

Clinopyroxenes ofamph-bearingharzburgites

TL23

TL1 and TL24

TL20 and TL45

composition of the inferredmetasomatic agents

BOA Tholeiitic basalts(Jurassic)

composition of the inferredmetasomatic agents

Betic Alkaline lamprophyres(Triassic)

composition of the inferredmetasomatic agents

Betic Lamproites(Miocene)

Cho

ndrit

e-no

rmal

ized

10

100

Cho

ndrit

e-no

rmal

ized

10

100

1000

Cho

ndrit

e-no

rmal

ized

anhydrous cpx (pl)-rich lherzolites

Anhydrous harzburgites

Amph-bearing harzburgite

LuYbTmErHoDy TbGdEuSmNdPrCeLa

LuYbTmErHoDy TbGdEuSmNdPrCeLa

LuYbTmErHoDy TbGdEuSmNdPrCeLa

a

b

c

Ce Pr NdSmEu Gd Tb Dy Ho Er TmYbLa Lu

Ce Pr NdSmEu Gd Tb Dy Ho Er TmYbLa Lu

Fig. 7. Chondrite-normalized (McDonough and Sun, 1995) REE patterns of mantleclinopyroxene and compositions of the theoretical metasomatic agents that affectedmantle peridotites from Tallante. The latter were inferred starting from clinopyroxenecompositions, using distribution coefficients cpx/melt reported by Lee et al. (2007).Note that a) theoretical metasomatic agents effective for anhydrous cpx-rich (pl-bearing) lherzolites show analogies with Jurassic tholeiite basalts (Gomez-Pugnaire etal., 2000); b) theoretical metasomatic agents effective for anhydrous harzburgites showanalogies with highly alkaline melts such as the Betic lamprophyres (Puga et al., 2010);c) theoretical metasomatic agents effective for amph-harzburgites show analogies withthe Tertiary Spanish lamproites (Conticelli et al., 2009).

315G. Bianchini et al. / Lithos 124 (2011) 308–318

down to 0.51211 and 176Hf/177Hf down to 0.28196, which indicatea subduction-related fingerprint. In this framework, the new dataand, in particular the remarkable unradiogenic Hf isotopic

composition (εHf=−28; ΔHf=−26.7) support the recycling ofcontinental crust components in the mantle via subduction.

In situ U–Pb datings on zircons from analogous felsic veins indicatethat the age of the veining event ranges between 4.4 and 2.2 Ma(Bianchini et al., 2009) thus implying a clear relation with the Tertiarysubduction and collisional processes that ultimately lead to the BeticCordillera formation.

7. Geodynamic framework

Recent studies by Rampone et al. (2010) and Shimizu et al. (2008)propose that the mineralogical and geochemical heterogeneitiesrecorded in the xenolith suite of Tallante were entirely generatedduring the “mantle wedge” evolution related to the Cenozoic Beticsubduction processes; in this model, pervasive melt impregnation,annealing recrystallization and refertilization are tentatively relatedto the uprising of subalkaline basalts closely comparable to thoserecorded in the Alboran domain, i.e. arc-type (subduction-related)tholeiites (Duggen et al., 2004, 2005, 2008; Torres-Roldan et al.,1986).

A comparison of the petrological data on mantle xenoliths fromTallantewith the available data onmagmatic rocks from the Betic areaas well as those of neighbouring ophiolite- and orogenic-peridotitessuggests an alternative interpretation implying multiple tectono-magmatic phases, some of which occurred in Pre-Cenozoic times. Inthis framework it has to be noted that:

– pl-bearing cpx-rich lherzolites from Tallante resemble analogousrock-types observed in ophiolite–peridotites from the Alps,Apennine and Corsica, with similar pl-bearing impregnationsthat are interpreted as the result of interaction with MORB-typemelts (Borghini et al., 2007; Müntener et al., 2004; 2010; Piccardoand Vissers, 2007; Piccardo et al., 2007; Rampone et al., 1997).Coherently, plagioclase separated from the gabbroic lenticular podobserved in sample TL196 displays 87Sr/86Sr=0.70323 that iscompatible with segregation from a MORB-type melt.

– In these lherzolites, the plagioclase, i.e. the product of therefertilization processes, usually shows lower 87Sr/Sr86 than thecoexisting clinopyroxene (Beccaluva et al., 2004); e.g. sample TL20shows 87Sr/Sr86 0.70250 for pl and 0.70298 for cpx; sample TL45shows 87Sr/Sr86 0.70265 for pl and 0.70272 for cpx. This supportsMORB-affinity and an asthenospheric origin for the infiltratingmetasomatic agents.

– Sm/Nd and 143Nd/144Nd ratios of cpx-rich lherzolites from Tallanteresemble those of analogous rock-types in ophiolite–peridotitesfrom the Alps and Apennine defining a trend that implies a pre-Cenozoic radiogenic ingrowth of the Sm–Nd isotopic system(Müntener et al., 2004 and references therein).

– As concerns the nature of the metasomatizing agents it is to benoted that the Cenozoic tholeiites from the Alboran domain areIsland Arc Basalts (IAB) and, in contrast to MORB tholeiites, shouldnot induce plagioclase impregnation. This difference in thecrystallization sequence, related to higher H2O content of IABmagmas (Beccaluva et al., 1984; Cameron et al., 1980; Perfit et al.,1980), is confirmed by petrographic observations on Cenozoictholeiites from the region (Malaga dykes), which show thatplagioclase crystallizes late in the sequence and only in thegroundmass, whereas the scarce phenocrysts are mainly repre-sented by olivine and clinopyroxene.

– Moreover, the Cenozoic Island-Arc tholeiites known in the region,offshore in the Alboran sea or as dykes close to Malaga (Duggen etal., 2004, 2005, 2008; Torres-Roldan et al., 1986) display a Sr–Ndisotopic fingerprint (87Sr/86Sr 0.7048–0.7119, 143Nd/144Nd0.51301–0.51255) totally different from the cpx-rich pl-bearinglherzolites from Tallante (87Sr/86Sr 0.70213–0.70351, 143Nd/144Nd0.51297–0.51339) thus precluding a genetic link with the

316 G. Bianchini et al. / Lithos 124 (2011) 308–318

mentioned refertilization processes (Fig. 8). The other subductionrelated Cenozoic magmas are calcalkaline, shoshonitic and ultra-potassic and display even greater isotopic differences.

Therefore we propose that the metasomatic and refertilizationprocesses, evident in the anhydrous peridotites, plausibly occurredduring pre-Cenozoic tectono-magmatic phases. Among the Mesozoicmagmatic rocks known in the Betic area, the Jurassic basalts of theBetic Ophiolite Association (BOA) display a Sr–Nd isotopic fingerprint(87Sr/86Sr 0.70266–0.70269, 143Nd/144Nd 0.51302–0.51305; Gomez-Pugnaire et al., 2000) similar to the compositions of anhydrous cpx-rich (pl-bearing) lherzolites from Tallante, thus suggesting a possiblepetrological link (Figs. 7 and 8).

Anhydrous cpx-poor peridotite xenoliths from Tallante displaycomparatively higher 87Sr/86Sr (up to 0.70476) and lower 143Nd/144Nd (down to 0.51250) possibly indicating interaction with a LREEenriched melt (plausibly an alkaline basalt) characterized by an OIBisotopic signature. Note that alkaline Permian and Triassic lampro-phyres (Figs. 7 and 8), characterized by a LREE enrichment and EMisotopic signature approaching the composition of the inferredmetasomatic agents, are widespread in the Iberian Peninsula(Villaseca et al., 2004) and have been recently discovered also in theBetic area (Puga et al., 2010).

Similar evolution has been proposed for mantle xenoliths fromOlot (NE Spain) where Bianchini et al. (2007) suggested that: a)harzburgites acquired their geochemical signature by metasomaticprocesses due to melts similar to the Iberian Permo–Triassic alkalinelamprophyres; and b) cpx-rich herzolites represent domains of thelithosphere totally rejuvenated by tholeiitic melts generated duringthe climax of the post-Variscan rifting of the Iberian margin. Acomparable petrogenetic history, in which lherzolites are interpretedas refertilized domains rather than portions of pristine mantle, isprovided by the Pyrenean peridotite body of Lherz (Le Roux et al.,2007).

The Cenozoic subduction-related processes, on the other hand,seem to have a role in the genesis of the amph/phl-bearing felsic

0.5120

0.5122

0.5124

0.5126

0.5128

0.5130

0.5132

0.5134

0.702 0.704 0.706 0.708 0.710

URDM

CHUR

Amph-harzburgite and orthopyroxenite

Cpx (Pl)-rich lherzolites

Cpx-poor lherzolites and harzburgites

Tallante xenoliths

Anhydrous sp-peridotites

Tholeiitic Mafic Rocks of the Alboran Domain

(Miocene)BOA Ophiolitic basalts

(Jurassic)

Alkaline lamprophyres(Permian-Trias)

143Nd144Nd

87Sr86Sr

Fig. 8. Nd vs Sr isotope composition of mantle xenoliths from Tallante. Composition ofCenozoic tholeiite magmas from the Alboran region is taken from Turner et al. (1999)and Duggen et al., 2004. Compositions of Jurassic tholeiite basalts and Permian-Triassiclamprophyres are from Gomez-Pugnaire et al. (2000) and Villaseca et al. (2004) andrespectively.

veinlets. In this case, the neoformation of opx+qtz in the metaso-matic parageneses indicates that the causative agents were alkali-richsilica-oversaturated melts, which were in turn related to recycling(and melting) within the mantle of crustal lithologies via subduction.However, the model provided by Arai et al. (2003) that envisaged an“Adakitic” nature of the metasomatic agents, resulting from slabmelting of “oceanic” lithologies (basalts and gabbros, or their high-pressure eclogite equivalent) has to be refined. Sr–Nd–Hf isotopicevidence supports the involvement of “continental” crust componentsdragged down into the mantle by subduction (Beccaluva et al., 2004).Coherently, Martelli et al. (2009) highlighted that mantle rocks fromTallante are characterized by low 3He/4He (never exceeding 5.6 Ra) asresult of time-integrated 4He development within a mantle wedgemetasomatized by U- and Th-rich crustal components.

These features are related to collisional processes that formedmelanges in which crustal and mantle rocks are intimately associated,as observed in the neighbouring Alpine-peridotite bodies of Rondaand Beni Bousera (Morishita et al., 2009; Thompson Lundeen, 1978and references therein). Partial melting of high-grade metamorphicrocks (Auzanneau et al., 2006; Hermann and Spandler, 2008; Monteland Vielzeuf, 1997), and subsequent felsic melt-peridotite interactiongenerated the opx−pl±qz±amph±phl veins recorded in thestudied mantle xenoliths.

We also hypothesize that the resulting metasomatic mantleparageneses share compositional analogies with the mantle sourceof the Murcia-Almeria ultrapotassic magmas, which are typicallycharacterized by a negative εHf isotopic fingerprint (down to −16;Nowell et al., 2008; Prelević et al., 2010).

8. Conclusions

In the previous sections we propose that in the Betic area pre-Cenozoic magmatic phases were effective in modifying and diversi-fying the sub-continental mantle, emphasizing analogies between theisotopic composition of the studied xenoliths and those of a range ofMesozoic magmas including the basalts of the Betic OphioliteAssociation (BOA) and the Betic Alkaline lamprophyres. This indicatesthat the lithospheric mantle beneath the Betic Cordillera records pre-Cenozoic tectono-magmatic cycles, including the post-Hercynianmagmatism, which is recognized in most sectors of the WesternEuropean Variscan Orogen. The initial phases of these processes in theIberian plate are recorded in lamprophyre dykes that are widespreadin the Central Spanish System (Villaseca et al., 2004), as well as in theBetic realm (Puga et al., 2010). Subsequently, a more abundantUpper Triassic-to-Upper Cretaceous magmatism developed along theSubbetic Zone (Fig. 1) in connection with the opening of the centralpart of the Atlantic Ocean (Puga et al., 2010, 2011), and the westwardpropagation of the Neotethys rifting and oceanization (Dewey et al.,1973; Ziegler, 1993). Within this extensional framework, the uplift ofthe asthenosphere induced magma genesis and widespread referti-lization of the lithospheric mantle, which is recorded in mantlexenoliths from Tallante.

Subsequently, the geochemical inheritance of these Mesozoicprocesses was partially masked by the Neogene evolution thatoccurred in a mantle–wedge setting, as testified by veins indicatingchannelled uprising of subduction-related magmas (Arai et al., 2003;Beccaluva et al., 2004; Rampone et al., 2010).

This scenario involving multiple phases of rifting is in agreementwith the crustal thinning that affected the whole region and iscoherent with thermal models based on apatite fission track analysesof Mesozoic sediments from the South-Iberian Continental Margin(Barbero and López-Garrido, 2006).

The history of mantle uplift and crustal thinning delineated for themantle section beneath Tallante fits the early models proposed by Vander Wal and Vissers (1993) and Vissers et al. (1995) for theneighbouring ultramafic massif of Ronda. These authors ascribed the

317G. Bianchini et al. / Lithos 124 (2011) 308–318

exhumation of the ultramafic rocks to an earlier mantle uplift duringthe Mesozoic rifting, breakup and oceanization of the Neotethys.These processes were accompanied by further mantle decompression,deformation and metasomatism during the genesis of the Alboranback-arc basin. This scenario agrees with the U–Pb datings obtainedby Sanchez-Rodriguez and Gebauer (2000) on zircons from Rondapyroxenites.

If correct, this history, suggests that the Tallante mantle section aswell as those of Ronda and Beni Bousera (Michard et al., 1997) wereuplifted to upper crustal levels long before the Neogene, and weresubsequently reactivated during the Oligo-Miocene development ofthe Alboran back-arc basin.

Acknowledgements

The authors gratefully acknowledge the fruitful discussions with S.Conticelli, G. Piccardo, S. Tonarini, M. Tiepolo and E. Rampone, as wellas the constructive criticism provided by two anonymous referees.

References

Ancochea, E., Nixon, P.H., 1987. Xenoliths in the Iberian Peninsula. In: Nixon, P.H. (Ed.),Mantle Xenoliths. John Wiley, pp. 119–124.

Arai, S., Shimizu, Y., Gervilla, F., 2003. Quartz diorite veins in a peridotite xenolith fromTallante, Spain: implications for reactions and survival of slab-derived SiO2-oversaturated melts in the upper mantle. Proceedings of the Japan Academy, SeriesB 79, 145–150.

Auzanneau, E., Vielzeuf, D., Schmidt, M.W., 2006. Experimental evidence of decom-pression melting during exhumation of subducted continental crust. Contributionsto Mineralogy and Petrology 152, 125–148.

Banda, E., Gallart, J., Garcia-Duenas, V., Danobeitia, J.J., Makris, J., 1993. Lateral variationof the Crust in the Iberian peninsula: new evidence from the Betic Cordillera.Tectonophysics 221, 53–66.

Barbero, L., López-Garrido, A.C., 2006. Mesozoic thermal history of the Prebeticcontinental margin (southern Spain): constraints from apatite fission-trackanalysis. Tectonophysics 422, 115–128.

Beccaluva, L., Ohnenstetter, D., Ohnenstetter, M., Paupy, A., 1984. Two magmatic serieswith island arc affinities within the Vourinos ophiolite. Contributions toMineralogy and Petrology 85, 253–271.

Beccaluva, L., Bianchini, G., Coltorti, M., Perkins, W.T., Siena, F., Vaccaro, C., Wilson, M.,2001. Multistage evolution of the European lithospheric mantle: new evidencefrom Sardinian peridotite xenoliths. Contributions to Mineralogy and Petrology142, 284–297.

Beccaluva, L., Bianchini, G., Bonadiman, C., Siena, F., Vaccaro, C., 2004. Coexistinganorogenic and subduction-related metasomatism in mantle xenoliths from theBetic Cordillera (southern Spain). Lithos 75, 67–87.

Bedini, R.M., Blichert-Toft, J., Boyet, M., Albarède, F., 2004. Isotopic constraints on thecooling of the continental lithosphere. Earth and Planetary Science Letters 223,99–111.

Benito, R., Lòpez Ruiz, J., Cebrià, J.M., Hertogen, J., Doblas, M., Oyarzun, R., Demaiffe, D.,1999. Sr and O isotope constraints on source and crustal contamination in the high-K calc-alkaline and shoshonitic Neogene volcanic rocks of SE Spain. Lithos 46,773–802.

Bianchini, G., Beccaluva, L., Bonadiman, C., Nowell, G., Pearson, G., Siena, F., Wilson, M.,2007. Evidence of diverse depletion and metasomatic events in harzburgite–lherzolite mantle xenoliths from the Iberian plate (Olot, NE Spain): implications forlithosphere accretionary processes. Lithos 94, 25–45.

Bianchini, G., Beccaluva, L., Siena, F., Tiepolo, M., 2009. Subduction and crust recycling—petrological evidence and U–Pb dating in mantle xenoliths from the Betic area(Spain). Geochimica et Cosmochimica Acta, 19th Goldschmidt Conference SpecialSupplement, p. A119.

Bianchini, G., Beccaluva, L., Bonadiman, C., Nowell, G.M., Pearson, D.G., Siena, F., Wilson,M., 2010. Mantle metasomatism by melts of HIMU piclogite components: newinsights from Fe-lherzolite xenoliths (Calatrava Volcanic District, central Spain).Geological Society, London, Special Publications 337, 107–124.

Borghini, G., Rampone, E., Crispini, L., De Ferrari, R., Godard, M., 2007. Origin andemplacement of ultramafic–mafic intrusions in the Erro-Tobbio mantle peridotite(Ligurian Alps, Italy). Lithos 94, 210–229.

Borghini, G., Fumagalli, P., Rampone, E., 2010. The stability of plagioclase in the uppermantle: subsolidus experiments on fertile and depleted lherzolite. Journal ofPetrology 51, 229–254.

Brey, G.P., Köhler, T.P., 1990. Geothermobarometry in four phases lherzolites II. Newthermobarometers and practical assessment of existing thermobarometers. Journalof Petrology 31, 1353–1378.

Büchl, A., Snow, J.E., 2003. The Os isotopic variation of abyssal peridotites revised: astudy from the ultra-slow spreading Gakkel Ridge. EGS–AGU–EUG Joint Assembly,Abstracts from the meeting held in Nice, France, 6–11 April 2003, abstract #9454.

Cameron, W.E., Nisbet, E.G., Dietrich, V.J., 1980. Petrographic dissimilarities betweenophiolitic and ocean-floor basalts. In: Panayotou, A. (Ed.), Ophiolites, pp. 182–192.

Capedri, S., Venturelli, G., Salvioli-Mariani, E., Crawford, A.J., Barbieri, M., 1989. Uppermantle xenoliths and megacrysts in alkali basalts from Tallante, South-EasternSpain. European Journal of Mineralogy 1, 685–699.

Cebriá, J.M., López-Ruiz, J., Carmona, J., Doblas, M., 2009. Quantitative petrogeneticconstraints on the Pliocene alkali basaltic volcanism of the SE Spain VolcanicProvince. Journal of Volcanology and Geothermal Research 185, 172–180.

Coltorti, M., Bonadiman, C., Faccini, B., Grégoire, M., O'Reilly, S.Y., Powell, W., 2007.Amphiboles from suprasubduction and intraplate lithospheric mantle. Lithos 99,68–84.

Conticelli, S., Guarnieri, L., Farinelli, A., Mattei, M., Avanzinelli, R., Bianchini, G., Boari, E.,Tommasini, S., Tiepolo, M., Prelević, D., Venturelli, G., 2009. Trace elements and Sr–Nd–Pb isotopes of K-rich, shoshonitic, and calc-alkaline magmatism of theWesternMediterranean Region: genesis of ultrapotassic to calc-alkaline magmatic associa-tions in a post-collisional geodynamic setting. Lithos 107, 68–92.

Dewey, J.F., Pitman III, W.C., Ryan, W.B.F., Bonnin, J., 1973. Plate tectonics and theevolution of the Alpine System. Geological Society American Bulletin 84,3137–3180.

Dewey, J.F., Helman, M.L., Turco, E., Hutton, D.W.H., Knott, S.D., 1989. Kinematics of thewestern Mediterranean. In: Coward, M.P., Dietrich, D., Park, R.G. (Eds.), AlpineTectonics: Geological Society of London, Special Publications, 45, pp. 265–283.

Doblas, M., López-Ruiz, J., Cebriá, J.-M., 2007. Cenozoic evolution of the AlboranDomain: a review of the tectonomagmatic models. In: Beccaluva, L., Bianchini, G.,Wilson, M. (Eds.), Cenozoic Volcanism in the Mediterranean Area: GSA SpecialPapers, 418, pp. 303–320.

Dowall, D.P., Nowell, G.M., Pearson, D.G., 2003. A-2-column procedure for the pre-concentration of Sr, Nd and Hf for isotopic analysis by plasma ionisation multi-collector mass spectrometry. In: Holland, J.G., Tanner, S.D. (Eds.), Plasma SourceMass Spectrometry: Applications and Emerging Technologies. Royal Society ofChemistry, Cambridge, pp. 321–337.

Downes, H., 2001. Formation and modification of the shallow sub-continentallithospheric mantle: a review of geochemical evidence from ultramafic xenolithsuites and tectonically emplaced ultramafic massifs ofWestern and Central Europe.Journal of Petrology 42, 233–250.

Downes, H., Reichow, M.K., Mason, P.R.D., Beard, A.D., Thirlwall, M.F., 2003. Mantledomains in the lithosphere beneath the French Massif Central: trace element andisotopic evidence from mantle clinopyroxenes. Chemical Geology 200, 71–87.

Duggen, S., Hoernle, K., van den Bogaard, P., Harris, C., 2004. Magmatic evolution of theAlboran Region: the role of subduction in forming the western Mediterranean andcausing the Messinian Salinity Crisis. Earth and Planetary Science Letters 218,91–108.

Duggen, S., Hoernle, K., van den Bogaard, P., Garbe-Schönberg, D., 2005. Post-collisionaltransition from subduction- to intraplate type magmatism in the westernmostMediterranean: evidence for continental-edge delamination of subcontinentallithosphere. Journal of Petrology 46, 1155–1201.

Duggen, S., Hoernle, K., Klügel, A., Geldmacher, J., Thirlwall, M., Hauff, F., Lowry, D.,Oates, N., 2008. Geochemical zonation of the Miocene Alborán Basin volcanism(westernmost Mediterranean): geodynamic implications. Contributions to Miner-alogy and Petrology 156, 577–593.

Dupuy, C., Dostal, J., Boivin, P.A., 1986. Geochemistry of ultramafic xenoliths and theirhost alkali basalts from Tallante, southern Spain. Mineralogical Magazine 50,231–239.

Frey, F.A., Prinz, M., 1978. Ultramafic inclusions from San Carlos, Arizona: petrologicaland geochemical databearing on their petrogenesis. Earth and Planetary ScienceLetters 38, 129–176.

Gomez-Pugnaire, M.T., Ulmer, P., Lopez-Sanchez-Vizcaino, V., 2000. Petrogenesis of themafic rocks of the Betic Cordillera. Contributions to Mineralogy and Petrology 139,436–457.

Hermann, J., Spandler, C.J., 2008. Sediment melts at sub-arc depths: an experimentalstudy. Journal of Petrology 49, 717–740.

Holland, T., Blundy, J., 1994. Non-ideal interactions in calcic amphiboles and theirbearing on amphibole-plagioclase thermometry. Contributions to Mineralogy andPetrology 116, 433–447.

Irving, A.J., 1980. Petrology and geochemistry of composite ultramafic xenoliths inalkali basalts and implication for magmatic processes within the mantle. AmericanJournal of Science 280-A, 389–426.

Johnson, C.M., Beard, B.L., 1993. Evidence from hafnium isotopes for ancient suboceanicmantle beneath the Rio Grande rift. Nature 362, 441–444.

Kogarko, L.N., Ryabchikov, I.D., Brey, G.P., Fernández Santin, S., Pacheco, H., 2001.Mantlerocks uplifted to crustal levels: diffusion profiles in minerals of spinel-plagioclaselherzolites from Tallante, Spain. Geochemistry International 39, 355–371.

Le Roux, V., Bodinier, J.-L., Tommasi, A., Alard, O., Dautria, J.-M., Vauchez, A., Riches, A.J.V.,2007. The Lherz spinel lherzolite: refertilized rather than pristine mantle. Earth andPlanetary Science Letters 259, 599–612.

Lee, C.-T.A., Harbert, A., Leeman, W.P., 2007. Extension of lattice strain theory tomineral/mineral rare-earth element partitioning: an approach for assessingdisequilibrium and developing internally consistent partition coefficients betweenolivine, orthopyroxene, clinopyroxene and basaltic melt. Geochimica et Cosmochi-mica Acta 71, 481–496.

Martelli, M., Bianchini, G., Beccaluva, L., 2009. Geochemical fluxes associated to theBetic subduction (Spain): helium isotopic analyses of mantle xenoliths. Geochimicaet Cosmochimica Acta, 19th Goldschmidt Conference Special Supplement, p. A838.

Mauffret, A., Ammar, A., Gorini, C., Jabour, H., 2007. The Alboran Sea (WesternMediterranean) revisited with a view from the Moroccan Margin. Terra Nova 19,195–203.

McDonough, W.F., Sun, S.-s., 1995. The composition of the Earth. Chemical Geology 120,223–253.

318 G. Bianchini et al. / Lithos 124 (2011) 308–318

Michard, A., Goffe, B., Bouybaouene, M.L., Saddiqi, O., 1997. Late Hercynian±Mesozoicthinning in the Alboran domain:metamorphic data from the northern Rif, Morocco.Terra Nova 9, 171–174.

Montel, J.-M., Vielzeuf, D., 1997. Partial melting of metagreywackes, Part II. Composi-tions of minerals and melts. Contributions to Mineralogy and Petrology 128,176–196.

Morishita, T., Arai, S., Ishida, Y., Tamura, A., Gervilla, F., 2009. Constraints on theevolutionary history of aluminous mafic rocks in the Ronda peridotite massif(Spain) from trace-element compositions of clinopyroxene and garnet. Geochem-ical Journal 43, 191–206.

Müntener, O., Pettke, T., Desmurs, L., Meier, M., Schaltegger, U., 2004. Refertilization ofmantle peridotite in embryonic ocean basins: trace element and Nd isotopicevidence and implications for crust–mantle relationships. Earth and PlanetaryScience Letters 221, 293–308.

Müntener, O., Manatschal, G., Desmurs, L., Pettke, T., 2010. Plagioclase peridotites inocean–continent transitions: refertilized mantle domains generated by meltstagnation in the shallow mantle lithosphere. Journal of Petrology 51, 255–294.

Nowell, G.M., Kempton, P.D., Noble, S.R., Fitton, J.G., Saunders, A.D., Mahoney, J.J., Taylor,R.N., 1998. High precision Hf isotope measurements of MORB and OIB by thermalionisation mass spectrometry: insights into the depleted mantle. Chemical Geology149, 211–233.

Nowell, G.M., Pearson, D.G., Irving, A.J., 2008. Lu–Hf and Re–Os isotopic studies oflamproite genesis. 9th International Kimberlite Conference, Extended abstract No.9IKC-A-00151.

Pearson, D.G., Nowell, G.M., 2005. Accuracy and precision in plasma ionisation multi-collector mass spectrometry: Constraints from neodymium and hafnium isotopemeasurements. In: Holland, J.G., Bandura, D.R. (Eds.), Plasma Source MassSpectrometry, Current Trends and Future Developments. Royal Society ofChemistry, pp. 284–314.

Pearson, D.G., Canil, D., Shirey, S.B., 2003. Mantle samples included in volcanic rocks:xenoliths and diamonds. In: Carlson, R.W. (Ed.), The Mantle and Core: Treatise onGeochemistry, vol. 2, pp. 171–275.

Perfit, M.R., Gust, D.A., Bence, A.E., Arculus, R.J., Taylor, S.R., 1980. Chemicalcharacteristics of island-arc basalts: implications for mantle sources. ChemicalGeology 30, 227–256.

Piccardo, G.B., Vissers, R.L.M., 2007. The pre-oceanic evolution of the Erro-Tobbioperidotite (Voltri Massif, Ligurian Alps, Italy). Journal of Geodynamics 43, 417–449.

Piccardo, G.B., Zanetti, A., Muntener, O., 2007. Melt/peridotite interaction in theSouthern Lanzo peridotite: field, textural and geochemical evidence. Lithos 94,181–209.

Platt, J.P., Anczkiewicz, R., Soto, J.-I., Kelley, S.P., Thirlwall, M., 2006. Early Miocenecontinental subduction and rapid exhumation in the western Mediterranean.Geology 34, 981–984.

Prelević, D., Stracke, A., Foley, S.F., Romer, R.L., Conticelli, S., 2010. Hf isotopecompositions of Mediterranean lamproites: mixing of melts from asthenosphereand crustally contaminated mantle lithosphere. Lithos 119, 297–312.

Puga, E., 2005. A reappraisal of Betic ophiolitic association: the westernmost relic of theAlpine Tethys Ocean. In: Finetti, I.R. (Ed.), Elsevier Special Volume “CROP-DeepSeismic Exploration of the Central Mediterranean and Italy”, pp. 665–704.

Puga, E., Fanning, C.M., Nieto, J.M., Díaz de Federico, A., 2005. New recrystallisationtextures in zircons generated by ocean-floor and eclogite facies metamorphism: acathodoluminescence and U–Pb SHRIMP study with constraints from REEelements. Canadian Mineralogist 43, 183–202.

Puga, E., Díaz de Federico, A., Nieto, J.M., Díaz Puga,M.A., RodríguezMartínez-Conde, J.A.,2009. The Betic ophiolitic association: a very significant geological heritage thatneeds to be preserved. Geoheritage 1, 11–31.

Puga, E., Beccaluva, L., Bianchini, G., Díaz De Federico, A., Díaz Puga, M.A., Alvarez-Valero, A., Galindo-Zaldívar, J., Wijbrans, J.R., 2010. First evidence of lamprophyricmagmatismwithin the Subbetic Zone (Southern Spain). Geologica Acta 8, 111–130.

Puga, E., Fanning, C.M., Díaz de Federico, A., Nieto, J.M., Beccaluva, L., Bianchini, G., DíazPuga, M.A., 2011. Petrology, geochemistry and U–Pb geochronology of the BeticOphiolites: inferences on Pangaea break-up and birth of the Westernmost TethysOcean. Lithos 124, 255–272 (this volume).

Rampone, E., Hofmann, A.W., Piccardo, G.B., Vannucci, R., Bottazzi, P., Ottoline, L., 1995.Petrology, Mineral and isotope geochemistry of the External Liguride Peridotites(Northern Apennines, Italy).

Rampone, E., Piccardo, G.B., Vannucci, R., Bottazzi, P., 1997. Chemistry and origin oftrapped melts in ophiolitic peridotites. Geochimica et Cosmochimica Acta 61,4557–4569.

Rampone, E., Vissers, R.L.M., Poggio, M., Scambelluri, M., Zanetti, A., 2010. Meltmigration and intrusion during exhumation of the alboran lithosphere: the Tallantemantle xenolith record (Betic Cordillera, SE Spain). Journal of Petrology 51,295–325.

Reisberg, L., Lorand, J.-P., 1995. Longevity of sub-continental mantle lithosphere fromosmium isotope systematic in orogenic peridotite massifs. Nature 376, 159–162.

Salters, V.J.M., White, W.M., 1998. Hf isotope constraints on mantle evolution. ChemicalGeology 145, 447–460.

Sanchez-Rodriguez, L., Gebauer, D., 2000. Mesozoic formation of pyroxenites andgabbros in the Ronda area (southern Spain), followed by Early Miocene subductionmetamorphism and emplacement into the middle crust: U–Pb sensitive high-resolution ion microprobe dating of zircon. Tectonophysics 316, 19–44.

Schaefer, B.F., Turner, S.P., Rogers, N.W., Hawkesworth, C.J., Williams, H.M., Pearson, D.G.,Nowell, G.M., 2000. Re–Os isotope characteristics of postorogenic lavas: implicationsfor the nature of young lithospheric mantle and its contribution to basaltic magmas.Geology 28, 563–566.

Shimizu, Y., Arai, S., Morishita, T., Yurimoto, H., Gervilla, F., 2004. Petrochemicalcharacteristics of felsic veins in mantle xenoliths from Tallante (SE Spain): aninsight into activity of silicic melt within the mantle wedge. Transactions of theRoyal Society of Edinburgh: Earth Sciences 95, 265–276.

Shimizu, Y., Arai, S., Morishita, T., Ishida, Y., 2008. Origin and significance of spinel–pyroxene symplectite in lherzolite xenoliths from Tallante, SE Spain. Mineralogyand Petrology 94, 27–43.

Thompson Lundeen, M., 1978. Emplacement of the Ronda peridotite, Sierra Bermeja,Spain. GSA Bulletin 89, 172–180.

Torne, M., Fernàndez, M., Comas, M.C., Soto, J.I., 2000. Lithospheric structure beneaththe Alboran Basin: results from 3D gravity modeling and tectonic relevance. Journalof Geophysical Research 105, 3209–3228.

Torres-Roldan, R.L., Poli, G., Peccerillo, A., 1986. An Early Miocene arc-tholeiiticmagmatic dyke event from the Alboran Sea: evidence for precollisional subductionand back-arc crustal extension in the westernmost Mediterranean. GeologischeRundschau 75, 219–234.

Turner, S.P., Platt, J.P., George, R.M.M., Kelley, S.P., Pearson, D.G., Nowell, G.M., 1999.Magmatism associated with orogenic collapse of the Betic–Alboran domain, SESpain. Journal of Petrology 40, 1011–1036.

van Acken, D., Becker, H., Walker, R.J., 2008. Refertilization of Jurassic oceanicperidotites from the Tethys Ocean — implications for the Re–Os systematics ofthe upper mantle. Earth and Planetary Science Letters 268, 171–181.

van de Flierdt, T., Goldstein, S.L., Hemming, S.R., Roy, M., Frank, M., Halliday, A.N., 2007.Global neodymium–hafnium isotope systematics — revisited. Earth and PlanetaryScience Letters 259, 432–441.

Van der Wal, D., Vissers, R.L.M., 1993. Uplift and emplacement of upper mantle rocks inthe W Mediterranean. Geology 21, 1119–1122.

Vervoort, J.D., Blichert-Toft, J., Patchett, P.J., Albarède, F., 1999. Relationships betweenLu–Hf and Sm–Nd isotopic systems in the global sedimentary system. Earth andPlanetary Science Letters 168, 79–99.

Villaseca, C., Orejana, D., Pin, C., López Garcia, J.-A., Andonaegui, P., 2004. Lemagmatisme basique hercynien et post-hercynien du Système central espagnol:essai de caractérisation des sources mantelliques. Comptes Rendus Geoscience 336,877–888.

Vissers, R.L.M., Platt, J.P., van der Wal, D., 1995. Late orogenic extension of the BeticCordillera and the Alboran domain: a lithospheric view. Tectonics 14 (4), 786–803.

Ziegler, P.A., 1993. Late Palaeozoic–Early Mesozoic plate reorganization: evolution anddemise of the Variscan fold belt. In: Raumer, J.F., Nebauer, F. (Eds.), Pre-MesozoicGeology in the Alps. Springer Verlag, Berlin, pp. 203–216.