Spinel lherzolite xenoliths from the Cenozoic Calatrava volcanic fi eld provide a sampling of the lithospheric mantle of central Spaill. The xenoliths are estimated to originate from depths of 35-50 km. Trace element content of clinopyroxene and Cr-lllunber in spinel indi cate low degrees of partial melting (::: 5%) of the xenoliths. Although a major element whole-rock model suggests wider degrees of melting, the Calatrava peridotite chemistry indicates a moderately fertile mantle beneath central Spain. Calatrava peridotite xenoliths bear evidence for interaction with two different metasomatic agents. The emichment in LREE Oight rare earth element), Th, U and Pb, and the negative anomalies in Nb-Ta in clinopyroxene and amphibole from xenoliths of El Aprisco, indicate that the metasomatic agent was probably a subduction-related melt, whereas the emichment in l\1REE in clinopyroxene from xenoliths of the Cerro Pelado centre suggests an alkaline melt similar to the host lUldersaturated magmas. These metasomatic agents are also con sistent v..i th the chemistry of interstitial glasses fOlUld in xenoliths of the two volcanic centres.Differences in metasomatism but also in mantle composition is supported by Sr-Nd whole-rock data, which show a more radiogenic nature for Sr isotopes of samples from the El Aprisco centre (87Sr/86Sr ratios of 0.7035-0.7044 instead of 0.7032-0.7037 for samples from Cerro Pelado).The timing of the subduction-related metasomatic stage is unconstrained, although the Calatrava intraplate volcanism intrudes an old Variscan lithospheric section reworked during the converging plate system affecting SE Iberia in the Tertiary. The presence ofwehrlite types within the Calatrava peridotite xenoliths is here interpreted as a reaction of host lherzolites with silica-lUldersaturated silicate melts that could be related to the Calatrava alkalinemagmatism. The Sr-Nd isotopic com position of Calatrava peridotites plot within the European asthenospheric reselVorr (EAR) mantle, these values represent more emiched signatures than those fOlUld in the other Spanish Cenozoic alkaline province of Olot.Studies of ultramafic xenoliths exhumed by Ceno zoic volcanic activity have provided substantial information regarding the nature of the subcontinen tal lithospheric mantle (e.g. Nixon 1987;Downes 2001). In the Iberian peninsula three main Cenozoic volcanic fields have provided significant mantle derived xenolith suites since studies from the last century: SE Spain (Ossan 1889), Olot (San Miguel de la Camara 1936) and Calatrava (Ancochea & Nixon 1987) (Fig. 1). Scarce ultramafic xenoliths have also been described in the Cofrentes volcanic area (Ancochea & Nixon 1987;Seghedi et al. 2002), and mantle-derived xenoliths have been found in Upper Permian subvolcanic dykes of the Spanish Central System, although they represent mafic-ultramafic cumulates instead of real mantle peridotitic fragments (Orejana et al. 2006; Villaseca et al. 2007; Orejana & Villaseca 2008).In this work we study the chemical compositio...

Keywords: Gabbroic rocks Crustal recycling Variscan orogeny Uthospheric mantle Spanish Central SystemThe gabbroic intrusions that crop out along the Spanish Central System (SCS) are geochemically heterogeneous, including primitive and evolved rocks. Differentiation is mainly related to fractionation of Cr-spinel and olivine, but mixing with coeval granitic magmas or crustal assimilation may have also played a role in the evolution of the most differentiated rocks. The most primitive uncontaminated gabbros show arc like trace element chondrite and primitive-mantle normalised patterns, characterised by large ion Iithophile elements (ULE)-Iigh t rare earth elements (tREE) enrichment, Sr and Pb positive and Nb-Ta-Ti negative anomalies. However, paleogeographic constraints suggest that the SCS was located far from subduction zones, so these geochemical signatures could be better explained by a recycling of continental crustal components within the mantle. The most primitive SCS gabbros expand the Sr-Nd isotopic compositional range of the Variscan basic magmatism in the Central Iberian Zone to more depleted values. This reflects a heterogeneous sub-continental Iithospheric mantle under central Spain ranging from a depleted mantle (ENd = +3.1. 87Sr/86Sr= 0.704) towards an isotopically enriched component (ENd = -1.6, 87Sr/ 86Sr = 0.706). Geochemical modelling suggests that mantle enrichment could be explained by minor lower crustal metapelitic granulite contamination (-2%). Additionally. the Sr-Nd-Pb isotopic ratios of the most primitive gabbros match the composition of the European subcontinental lithospheric mantle recorded in ultramafic xenoliths from western and central Europe.

Basic to ultrabasic alkaline lamprophyres and diabases intruded within the Spanish

The Variscan Montes de Toledo Batholith (MTB) is an E-W linear array of peraluminous granite plutons which is chemically segmented. The study is focused on the western segment of the MTB (W-MTB), mainly composed of granites with slightly lower CaO and higher P₂O₅ contents than associated eastern plutonic units and nearby S-type granites, giving them a more pronounced peraluminous nature. The chemical contrast is also observed in isotopic composition, especially in radiogenic Nd and Pb ratios. The W-MTB granites have higher initial ε_Nd (-5.0 to -5.9) and lower ²⁰⁶Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios than peraluminous types from the E-MTB segment. A mixed pelitic-greywackeous derivation from regional Neoproterozoic formations is suggested whereas lower crustal and meta-igneous sources were involved in the origin of the easternmost MTB granites. The presence of igneous muscovite together with coexisting andalusite and sillimanite in some of the studied granites suggests that solidus was reached at 650-700 °C and depth corresponding to the pressure of 2-3 kbar

The alkaline lamprophyres and diabases of the Spanish Central System carry a heterogeneous suite of xenoliths which includes scarce pyroxenitic and hornblenditic types that can be divided in two groups: (a) pyroxenite xenoliths, including spinel clinopyroxenites and spinel websterites with granoblastic textures, and (b) hornblende-bearing clinopyroxenites and hornblen dites (here after called hornblenditic xenoliths) characterised by the presence of Ti-rich kaersutitic amphibole and magmatic textures, Both groups of xenoliths can be assigned to the Al-augite series of Wilshire and Shervais (1975) xenolith suite has a very homogeneous isotopic composition, close to the isotopically depleted values of high ENd and low 87 Sr/ 86 Sr ratios of one of the pyroxenite xenoliths, Some of these ultramafic xenoliths fall within the isotopic compositional range of their host alkaline dykes, which also define a bipolar compositional field, suggesting that most of them are cogenetic with the lamprophyres, P-T estimates yield temperatures in the range of 970-1 080 °c and pressures mainly from 0,9 to 1,2 GPa for pyroxenites, whilst hornblenditic xenoliths give lower (and probably underestimated) pressures (0,7-0,9 GPa), This pressure range is in agreement with pyroxenites being fonned by an underplating event at the upper mantle-lower crust boundary, whereas pressure estimates for hornblenditic xenoliths suggest equilibration within the lower crust

The Spanish Central System (SCS) batholith. located in the Central Iberian Zone, is one of the largest masses of granite in the European Variscan Belt. This batholith is a composite unit of late-and post-kinematic granitoids dominated by S-and I-type series granite. with subordinate leucogranite and granodiorite. Zircon trace element contents, from two representative S-type and three I-type granitoids from the eastern portion of the SCS batholith, indicate a heterogeneous composition due to magma differentiation and co-crystallisation of other trace element-rich accessory phases. In situ. U-Pb dating of these zircons by SHRIMP and LA-ICP-MS shows 479-462-Ma inherited zircon ages in the I-type intrusions. indicating the involvement of an Ordovician rnetaigneolls protolith, while the S-type intrusions exclusively contain Cadornian and older zircon ages. The zircon crystallisation ages show that these granites have been emplaced at ca. 300 Ma with a time span between 303 ± 3 Ma and 298 ± 3 Ma. Precise dating by CA-ID-TIMS reveals a pulse at 305.7 ± 0.4 Ma and confirms the major pulse at 300.7 ± 0.6 Ma. These ages match the Permo-Carbonif erous age for granulite-fades metamorphism of the lower crust under the SCS batholith and coincide with a wide spread granitic event throughout the Southern Variscides. Ti-in zircon thermometry indicates temperatures between 844 and 784°C for both the S-and I-type granites. rein forcing the hypothesis that these granites are derived from deep crustal sources.

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