In Central Spain, it is possible to distinguish two main types of peraluminous late-Hercynian granites: the PI types and the PS types. The distinction between both types is made on the basis of differences in peraluminosity (PS types are more peraluminous than PI types) and also on the appearance of some characteristic mafic minerals; PS types have biotite, cordierite and monazite as the most typical accessory phase, whereas PI types have biotite, amphibole (in the less evolved facies) and allanite as the accessory mineral. Both granite types have similar trace element ratios and initial Sr, Nd and Pb isotopic signatures, Initial 87Sr/ 86Sr ratios of both types exhibit a large range from 0,7073 to 0,7193, whereas initial BN d varies in a restricted range from -5,4 to -6,6, The scarce associated basic rocks do not play a significant role in the chemical variability of these peraluminous granites which follow low pressure crystal fractionation trends from granodior ite/monzogranite parental magmas, Mixing and AFC modelling of Sr and Nd isotopic data reveal an unrealistically high mantle contribution, Based on major and trace element and isotopic data, an orthogneissic protolith for both granitic series is proposed, Nevertheless, none of the metamorphic country rocks of Central Spain has the appropriate Sr isotopic composition to satisfy the origin of these granitic rocks, and so, it is argued that progressive isotopic re-equilibration of crustal material during the granulization of the lower Hercynian crust, together with the possibility of isotopic disequilibrium during melting (as has been demonstrated in migmatitic terranes in nearby areas) may explain the isotopic differences between the granites and the high level metamorphic country rocks,

A BSTRAcr: Convenlional rock class ification diagrams do not distinguish the variery of peraJumi nollS rock �ries. Mortover. peraluminClIl.� granite Iypes have nOl bee n clearly discriminated in rooenl revisions-The srudy of several peraluminous series in diff erenl iDtraooDUnental orogen..i c bellS reveals th:it four distinct groups can be defined. Using an A-B dil!lgraro, these four groups are:(I) rughly peraluminou! graniloids (hP) cbaracterised by high A values and typified by an increase in pcraJuminosity toward t he mOst malic vurieullS; (1) moderately peraluminous graniLOids (mP) whicb o.cc upy the intermediate field :and generaUy show increasing peraJuro.inosity t owa rds the most f!:lsic varieties; (3) low peraluminous gran.itoids (JP) which plot in the lowest p.an of tbe pcralwninous field dtfi.n.ing negalive slope trends.; (4) bigbly felsic pcraluminou:\ graniles UP) with po.orly defined va ria tion trends.In inlracontinentaJ or ogenic belts, tbe genesis of pcraluminous granitic series is favoured by the abundance of (enile cruslal prol oliths. mainly mctapditcs. mctaigneous rocks and mctagrcywlIckcs. The diffi culty of auaining temperatures in C"X� o( 950°C al lowcr cJUSTal Icvcl� during (he (octonothermal evolution or Ihjckened CIlJ.SI. inhibits 1 he panial melting of 010r-c basic sources.A Ithough the physica.l Pllramctc� of the mehing prote:S! in fluence I heir chemical and mineralogical characteristics.. SQurtt rock composition ultimately detemlinc.s t he degree of pcraJuminosily of the granitic series.J<. EY WOR DS: collisional orogenic magmatism. crustal protolil hs. granite elllSS ificalion. Conventional rock class ilie:ation diagrams (e.g. TAS andKlO-SiOl plots) do not distinguish the vari

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...

No abstract

SPAIN if the xenoliths is lower than that outcropping mid-crustal A contribution the granites reduces the mantle contribution in models if granite nature if the lower continental crust in contrasts with the more mqfic ffJ7f!r:r-,Cf1LUflf con7iJo:ntum and estimaud in other European Herrynian areas) a non-Thermobarometric calculations based on min-crust in this Herrynian eral paragenesis 850-950°(;, 7-11 indicate conditions around th us the xenoliths lower conassemi'JLCl!.'!e IS a Ket;vpftlUC coronas) alkaline magma. Felsic mela1!!J'leOlIS this high-T high-P by trf111. 'in(J'rt in the exhibit restitic mineral with up to 50% 37% sillimanite. Major and trace element mO,rJelLWP idea that the taU�-l1erc�vnuzn {J19JaLumlnollS 8 Nd calculaud at an (J1)erage H errynian age if 300 Ma) are in the range O' 706-0' 712) and-1,4 to-8'2, These values match the isowpic if the outcrobtnnp late TIe Sr

Abstract. In the Hercynian Anatectic Complex of Toledo (ACT) the anatectic granitoids include leucogranitic leucosomes, leucogranitic massifs, and restite-rich granites. They show a broad range of initial Sr and Nd isotope ratios from 0.71 I to 0.720 and 0.51164 to 0.51203, respectively, which clearly indicate the absence of isotopic homogenization in the melts. Broadly, the ranges reflect the isotopic variation of the metapelitic protoliths. If crusta! melting occurs under water-undersaturated conditions, as is the case of the ACT, the generated melts do not isotopically and chemically equilibrate with the granulitic residuum. The preservation of heterogeneities could arise through a number of pmcesses. (1) duration of the process:in which the presence of melts with disequilibrium features, and the high solid content of several of the granites in the ACT point to a very short-lived magmatic system, (2) limited

Andalusite occurs as an accessory mineral in many types of per aluminous felsic igneous rocks, including rhyolites, aplites, granites, pegmatites, and anatectic migmatites. Some published stability cunes for And = Sil and the water-saturated granite solidus permit a small stability field for andalusite in equilibrium with, felsic melts. We examine 108 samples of andalusite-bearing felsic rocks from more than 40 localities worldwide. Our purpose is to determine the origin of andalusite, including the T-P-X controls on andalusite formation, using eight textural and chemical criteria: sizecompa tibility with grain sizes of igneous m inera ls in the same rock; shape-ranging from euhedral to anhedral, with, no simple correla tion with, origin; state of aggregation-single grains or clusters of grains; association with, muscovite-with, or without, rims of mono crystalline or polycrystalline muscovite; inclusions-rare mineral inclusions and melt inclusions; chemical composition-andalusite with, little significant chemical variation, except in iron content (0-08-1-71 wt. °/o FeO); compositional zoning-concentric, sec tor, patchy, oscillatory zoning cryptically reflect growth, conditions; compositions of coexisting phases-biotites with. high, siderophy llite-eastonite contents (AT ~2-68 ± 0-07 atoms per formula unit), muscovites with 0-57-4-01 wt % P'eO and 0-02-2-85 wt % TiOg, and apatites with. 3-53 ± 0-18 wt % F. Coexisting muscovite-biotite pairs have a wide range of F contents, and FSt = 1-612FAIs + 0-015. Most coexisting minerals have compositions consistent with, equilibration at. magmatic conditions. The three principal genetic types of andalusite in felsic igneous rocks are: Type 1 Metamorphic-(a) prograde metamorphic (in ther mally metamorphosed peraluminous granites), (b) retrograde metamorphic (inversion from sillimanite of unspecified origin), (c) xenocrystic (derivation from local country rocks), and (d) restitic (derivation from source regions); Type 2 Magmatic-(a.) peritectic (water-undersaturated, TJ) associated with, leucosomes in migma tites, (b) peritectic (water-undersaturated, T^J, as reaction rims on garnet, or cordierite, (c) cotectic (water-undersaturated, T j direct, crystallization from a silicate melt, and (d) pegmatitic (watersaturated, T^J, associated with, aplite-pegmatite contacts or peg matitic portion alone; Type 3 Metasomatic-(water-saturated, magma-absent), spatially related to structural discontinuities in host, replacement, of feldspar and/or biotite, intergrowths with, quartz. Tie great, majority of our andalusite samples show one or more textural or chemical criteria suggesting a magmatic origin. Of the many possible controls on the formation of andalusite (excess AfOy,, water concentration and fluid evolution, high. Be-B-LiP , high. F, high. Fe-Mn-Ti, and kinetic considerations), the two most, important, factors appear to be excess Af03 and the effect, of releasing water (either to strip alkalis from the melt, or to reduce alumina solubility in the melt). Of particular importance is...

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.