Late Variscan metamorphic and magmatic evolution in the eastern revealed by U-Pb age zircon dating

CARMEN AGUILAR1', MONTSERRAT LIESAl, PEDRO CASTINEIRAS' & MARINA NAVIDAD' lDepartament de Geoquimica, Petrologia i Prospeccio Ge% gica, Facultat de Ge% gia, Universitat de Barcelona (UB), Zona Universitaria de Pedralbes, Marti i Franques sin, 08028 Barcelona, 2Departamento de Petrologia y Geoquimica, Facultad de Ciencias Geol6gicas, Universidad Comp/utense de Madrid, Jose Antonio Novais 12, 28040 Madrid, Spain *Corresponding author (e-mail: [email protected])

Abstract: Variscall migmatites cropping out in the eastern Pyrenees were dated together with Late Variscall plutonic rocks. Upper Proterozoic-Lower Cambriall series were migmatized during a thermal episode that occurred in the interval 320 -315 Ma coeval with the main Variscan deformation event (D!). The calc-alkaline Sant Lloreny- pluton and the gabbro-diorite Ceret stock were emplaced during a later thermal episode synchronous with the D2 deformation event. A tonalite located at the base of La Jonquera suite intruded into the upper crnstal levels between 314 and311 Ma. The gabbro-diorite stock was emplaced in the middle levels of the series in two magmatic pulses at312 and307 Ma. The thermal evolution recorded in the eastern Pyrenees can be correlated with that of neighbouring areas of NE Iberia (Pyrenees-Catalan Coastal Ranges) and SE (Montagne Noire). The correlation suggests a NW-SE-trending zonation where the northeasternmost areas (1v1ontagne Noire and eastern Pyrenees) would occupy relatively more internal zones of the orogen than the southwesternmost ones.

The eastern Pyrenees (Fig. 1 a) are a typical example of Va riscan Geological setting metamorphic basement in southwestern Europe (Fig. 1 b), where the pre-Va riscan series was defonned by polyphase defonnation The approximately east-west-trending antifonnal dome-shaped and metamorphosed llllder low-pressure-high-temperature condi­ (Fig. 1c) Roc de Frausa Massif forms a distinctive geological tions during the Late Mississippian to PeIlllsylvanian (e.g. Zwart assemblage separated from neighbouring areas (e. g. Albera, Aspres 1962; Guitard et al. 1995). Crustal melting took place in the middle and Canig6 massifs) by Alpine faults. Its pre-Variscan metasedi­ and lower crust and was synchronous with the intrusion of late mentary and metaigneous rocks (see details and age data given by Va riscan granitoids into upper crustal levels (e.g. Debon et al. Autran & Guitard 1969; Castifierias et al. 2008) are embedded in 1995; Roberts et al. 2000; ViIa et al. 2005). Since the pioneering the Variscan Sant Lloreny--La Jonquera plutonic complex. This work of Zwart and Guitard the timing and the geodynamic context coherent block was uplifted in response to Palaeogene compression of this thennal evolution has still not been resolved. and subsequent Neogene extensional tectonics, favouring the out­ The aim of this paper is to constrain the timing of the Variscan cropping of the lowennost materials (Cires et al. 1994). thermal evolution in the Roc de Frausa Massif (Fig. 1c) between The pre-Variscan gneisses and metasediments were affected the fonnation of the early regional orogenic migmatites and the by a third phase of deformation events (Liesa & Carreras 1989). emplacement of the upper and middle crustal intrusive rocks. Few The main deformation event (D1) is characterized by the develop­ geochronological data on migmatites are available in the Pyrenees ment of a pervasive foliation (S1)' representing the axial plane of at present. In addition, ages from the intrusive rocks need to be a tightly folded foliation (So). Two later defonnational events (D2 revised as earlier attempts using the Rb--Sr method have yielded and D3) produced a fold interference pattern that resulted in the yOllllger emplacement ages of 282±5Ma (Cocherie 1984) and present structure of the massif (Fig. 1c). D2 is characterized by more recent U-Pb zircon data have given 295±7Ma (Maurel NE-SW-trending tight folds that, in high-strain domains, trans­ 2003). However, the U-Pb method has yielded intrusion ages pose S1 foliation. D3 is recognized by NW-SE-trending open between 314 and 301 Ma in other adjacent plutons of the Pyrenees. folds and by shear zones related to it. A pervasive retrograde New U-Pb dating of zircon using sensitive high-resolution ion foliation developed in these shear zones transposed older ones. D1 microprobe-reverse geometry (SHRIMP-RG) was carried out on and D2 are attributed to the Variscan orogeny and are correlated Variscan migmatites together with dating of Late Variscan plutonic with prograde metamorphism, whereas D3 was produced in rocks emplaced at different crustal levels. These data are combined greenschist conditions and can be related either to the late with trace element chemistry on zircon and textures revealed by Variscan or to the Alpine cycle. cathodoluminescence (CL). The resulting age data and the relative The intensity of metamorphic overprint increased from amphib­ ages of the tectonic-metamorphic and magmatic processes allow olite-facies (andalusite micaschists in the higher levels to silliman­ us to make a better interpretation of the late Variscan thennal evo­ ite micaschists in the medium levels) to lower granulite-facies lution and to attempt a fIrst correlation with the neighbouring areas. conditions towards the deeper structural levels (Liesa & Carreras c::::::J Post-Variscan Materials , Fault Thrust O::..-��_.;;:.30km O,,-�_��...;;500km NPF North-Pyrenean Fault

CANIGO MASSIF + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

PRE-VARISCAN SERIES PRE-VARISCAN GRANITOIDS VARISCAN IGNEOUS ROCKS POST-VARISCAN MATERIALS UPPER ORDOVICIAN - SILURIAN Q Roe de Frausa orthogneiss Q Granitoids � MESOZOIC-PALEOGENE r=l Metapelites and metavolcanic rocks G Mas Blanc orthogneiss [lliI Gabbro-diorite o NEOGENE UPPER PROTEROZOIC - LOWER CAMBRIAN " Fault

Upper series * Samples Metapehtes and • Intermediate series metagreywackes Lower series j . •

Fig. 1. Geological sketch maps of the Variscan basement in (a) the central and eastern Pyrenees and (b) central and southwestern Europe. (c) Geological sketch map of the Roc de Frausa Massif and Sant Lloreny-La Jonquera plutonic complex with the location of the samples collected.

1989). where widespread migmatization took place. The lower­ Carnbrian series and the Upper Ordovician-Silurian rocks (Fig. most migrnatites reached temperature peak conditions during the 1c), it displays a cross-cutting relationship with the country-rock at main deformational event (Dj). its eastern end and at the roof (Fig. 1c). The late Variscan magmatic bodies were emplaced in different The Ceret stock is the most prominent of a series of smaller 2 levels of the pre-Variscan rock series (Liesa & Carreras 1989). The (10 km ) gabbro-diorite bodies including ultrarnafic cumulates Sant Lioreny-La Jonquera batholith is a sheet-like intrusion, vary­ intruded into the intermediate series. Both the Sant Lioreny-La ing in composition from tonalite to granite. Although the base of Jonquera batholith and the Ceret stock are synkinematic with the D2 the batholith was emplaced roughly parallel to lithological bounda­ deformation event, as indicated by the preferred orientation of the ries and Sj foliation between the Upper Proterozoic-Lower magmatic fabric. They have different geochemical characteristics Fig. 2. Microscopic aspect of the migmatites. Sample 349 (lowermost migmatites): (a) tightly fo lded lithological banding; (b) muscovite and biotite define the S1 fo liation and crystallize parallel to the axial planes of tight D, folds. Sample 526 (migmatites fr om the Ceret stock contact aureole): (c) fi brolite defines S1 fo lded by subsequent D, deformation event that developed tight fo lds, which are also folded by the last deformation event (D]); (d) S, is defined by the crystallization of the neosome parallel to the axial plane of the folds. Mineral abbreviations after Holland & Powell (1998). and belong to two genetically distinct igneous suites produced in tounnaline and opaque minerals. Muscovite and biotite are subhedral different levels of the lithosphere (Vila et al. 2005). Cordierite­ and defme SI foliation. Locally, biotite and muscovite crystallize par­ andalusite hornfelses fonned around the Sant Lioreny-La Ionquera allel to the axial planes of tightD2 folds (Fig. 2b). Retrograde chlorite, intrusion, whereas widespread migmatization in the granulite facies epidote and sericite are related to DJ structures. In sample 524, the developed in the contact metamorphic aureole around the Ceret characteristic mineral association contains quartz, plagioclase and stock, including a mineral association of gamet, cordierite, biotite, biotite. Ilmenite, magnetite, zircon, monazite, apatite and tourmaline sillirnanite, K-feldspar, plagioclase and quartz roughly aligned par­ are found as accessory minerals. Isolated grains of gamet are included allel to the axial planes of D2 folds (Fig. 2c and d). in plagioclase. Most of the subidioblastic biotite crystals are located in the palaeosome and defme a preferred orientation parallel to SI. This foliation developed open folds during a DJ defonnation. Occasionally, Sample description kink bands are fonned in biotite and their axial planes are also related To detennine the time evolution from early migmatization to the to the DJ defonnation event. emplacement of the magmatic bodies and the formation of migma­ Sample 530 is a holocrystalline, granular tonalite from the Sant tites around the gabbro-diorite Ceret stock (Fig. 1 c), we selected Lioreny-La Ionquera batholith with the major constituents quartz, (1) two migmatites from the lower series, (2) two late Variscan K-feldspar, plagioclase, biotite and hornblende and with variable igneous rocks, and (3) two migmatites from the contact aureole. grain size. Plagioclase fonns idiomorphic phenocrysts and displays The two migmatites from the lower series (samples 349 and 524) oscillatory zoning as well as Carlsbad and polysynthetic twinning. show a tightly folded lithological banding (Fig. 2a) with a coarse­ Biotite and hornblende are subhedral and show a strong pleochro­ grained(> 1 mm) leucosome and a fme-grained «1 mm) palaeosome. ism from brown to reddish brown and green to light brown, respec­ The latter displays a granolepidoblastic texture and preserves SI folia­ tively. Biotite crystals contain a large number of inclusions of tion. The mineral association in sample 349 consists of quartz, plagio­ zircon and apatite. Opaque ore and allanite are also present. Sample clase, muscovite and biotite, and the accessories, zircon, rnonazite, 420, represents a medium- to coarse-grained gabbro from the Ceret 349 . 530 11 13, 20 1 14, 32, 0.2 mm 0.2 mm 19 20 21 23

524 8 7 9

420 9 1

0.2 mm

O.2mm Fig. 3. CL images of the analysed zircon rims from the lowennost migmatites (samples 349 and 524) with the location of the SHRIMP spots. 1 1 stock with variable grain size. It has a granular to ophitic texture and it is composed of clinopyroxene, amphibole, plagioclase, bio­ tite and the accessories zircon, apatite and opaque ore. Quartz is scarce and has an interstitial texture. Plagioclase is idiomorphic Fig, with Carlsbad and polysynthetic twinning and is surrounded by 4, CL images of the analysed zircons from the Sant Lloren,-La Jonquera tonalite (samples 530) and the Ceret stock gabbro (sample 420) clinopyroxene, amphibole and anhedral biotite. Altered olivine is with the location of the SHRIMP spots. locally included in clinopyroxene. Arnphiboleand biotite occasion­ ally display a coronitic texture around clinopyroxene. Secondary minerals are iddingsite, white mica and uralite. A second foliation (SJ is defined by the crystallization of the leu­ Samples 526 and 529 represent migmatites from the Ceret stock cosome parallel to the axial plane of the folds and associated with contact aureole corresponding to metapelitic rocks from the inter­ the D2 deformation event (Fig. 2d). Cordierite porphyroblasts mediate series located near the Pic de F ontfreda. Both samples con­ include biotite oriented by SI and S2' which is interpreted as late to sist of a coarse-grained leucosome and a fine-grained palaeosome. post-D2 deformation. Sericite, pinnite and muscovite are retrograde In sample 526, the leucosome has a granular texture composed of minerals. quartz, K-feldspar, biotite and idiomorphic to subidiomorphic por­ phyroblasts of plagioclase, garnet and cordierite. The palaeosome shows a grano-lepidoblastic banded texture with xenoblastic quartz Zircon morphology and plagioclase layers alternating with fibrolite and biotite layers. Migmatites fromthe lower series Sillimanite is either fibrolitic or prismatic and is included in garnet and cordierite porphyroblasts together with biotite and ilmenite. Zircons obtained from the lowermost migrnatites (samples 349 and Sillimanite is found in three textural situations, thus allowing us to 524) are small and scarce. In fact, fewer than a hundred grains were establish the blastesis-deformation relationships: type I appears as extracted from c. l2 kg of each sample. Zircon grains can be colour­ fibrolite in the fold flanks of the first schistosity(So); type II is also less or various shades of brown and purple, and are practically free of fibrolitic and defines SI (Fig. 2c); type III is coarse prismatic silli­ visible inclusions. Two groups of zirconcan be distinguished: (1) sub­ manite parallel to the S2 foliation. Cordierite porphyroblasts dis­ rounded stubby grainswith pitted and dull surfaces owing to sedimen­ play simple twinning. Accessory minerals are iirnenite, pyrite, tary abrasion that are interpreted as detrital zircon; (2) idiomorphic apatite, zircon and monazite. In sample 529, the leucosome is also grainswith highly variable habits and secondary and shiny faces that composed of quartz, antiperthitic plagioclase, biotite, garnet, are interpreted as metamorphic zircon. No evidence was found of cordierite and the accessories spinel (included in cordierite), ilmen­ chemically corroded grains without further overgrowths. CL images ite, pyrite, apatite, zircon and monazite. The palaeosome is formed of the latter reveal a varied population of cores with scarce irregular of alternating xenoblastic quartzofeldspathic and biotite layers. dark rims (Fig. 3). The cores have different textures, including oscil­ Cordierite is also found as porphyroblasts. Quartz, plagioclase and latory, sector and soccer-ball zoning, and contrasting luminescence biotite from the palaeosome crystallize parallel to the SI foliation. responses, from low to high. These characteristics suggest that the 0 .085 ------,- --, Sample 530 (a) Sample '70 0 0.060 To common Pb 349 o Antecrysts (314.2 ±1.5 Ma) • Magmatic age (311.0±0.9 Ma)

'30 0 0.05 8 l!,. Lead loss 0.075 ga a 290 weighted mean age 0.05 6 320±13 Ma .c (95% .c 11. confidence) O.065 0054 l t Pb .c modern 11. o :a 11. ill � 0.05 2

0.050 350 330

0.048 0 0 45 ------. L-....,.,6!:-��-!'. 17:-� �, 8:-� ..,,� 9 � � 20:-� -,2:!:, --' "'u/"'Pb

Sample 524 0.058 (b) weighted mean age 325 313± 13 Ma 0 0.070 (95% confidence) (b) Sample 420 305 0 To common Pb 0.05e o Old cores (312 .0±1.6 Ma) 285 0 0.06 6 • Young ccres (307.6 ±1.5 Ma) + o Rims (307.0±3. 5 Ma) .c 11. l:l Lead loss lO.O54 l� 0.062 .c 11. � ill 0.052 0 f 0.058 l I- et .c 11. 0.050 modern Pb � 0.054 losstre�

320 00 ...- � 290 280 0.0 8 0.050 � 4 17 18 19 20 21 22 23 � "'UI "'Pb

0.046 Fig. 5. Tera-Wasserburg diagrams of SHRIMP U-Pb zircon ages from the lowermost migmatites: (a) sample 349; (b) sample 524. The grey­ shaded ellipses represent the data used to obtain the weighted mean age 0.042 (inset), whereas the white ellipses were discarded. Inherited ages are not 20 21 22 23 shown for clarity. Error ellipses are ±2cr. 238U/ "'Pb

Fig. 6. Tera-Wasserburg diagrams of zircon U-Pb ages from Variscan cores represent fonner detrital grains, magmatic in origin, which are igneous rocks: (a) the Sant Lloreny-La Jonquera tonalite (sample 530); overgrown duringmetamorphism. (b) the Ceret stock gabbro (sample 420). Error crosses are ±2cr.

Sant Llore/1l;-La Jonquera tonalite and Ceret surrOlmded by variably thick rims (c. 25 �un thick) that are highly stock gabbro luminescent and display a subtle broad oscillatory zoning (Fig. 4).

Zircon crystals from thetonalite of the Sant Lloren9-La Jonquera Migmatites from the Ceret stock contact aureole batholith (sanlple 530) are colourless, pale yellow or light purple and contain few visible inclusions. They foml short prisms with Only one of the migmatitesfrom the Ceret stock contact aureole pro­ differently shaped pyramid tenninations and length-to-breadth duced a zircon yield (sample 529), whereas sample 526 was devoid ratios between 1:2 and 1:4. Under CL, zircons display broad mod­ of this mineral. As in the lowennost migmatites, zircon grains are erately Iwninescent oscillatory zones typical of magmatic environ­ variably coloured and display two distinct morphologies: one corre­ ments, and in a few grains less luminescent homogeneous cores can sponding to detrital zircon and the other to metamorphic zircon. also be discerned (Fig. 4). Zircons from the Ceret stock gabbro (sample 420) are moder­ ately elongated prisms with roWlded terminations, variable aspect Results ratios (1:1 to 1:3) and abundant inclusions. They are generally bro­ Zircon U-Pb dating ken. CL images reveal definite core-rim structures that can be observed even under the transmitted light m icroscope. The cores Analytical results for zircon U-Pb dating are plotted in Figures 5 exhibit a non-luminescent weakly oscillatory and sector zoning and 6. The uncertainties for the error ellipses and crosses are 1000 10000 (a) (a) Sample 349 E 1000 0.. � 100 :::J -QI ';:: "tl 10 c 100 0 ..c:: 1 10 100 � Th (ppm) c 0 0.70 � 0.1 (b) 'N 0.01 0.60 o o (b) Sample 524

349-4 1000 349-11 o 0.50 o 100 • ,SI :::I ';:: W o "3040 -g 10 W o ..c:: � c 0.30 o � 'N 0.1

524-5 • • • • 0.20 • La Ce Pr Nd Srn Eu Gd Oy Y Er Yb

0.10 Fig, 8, Chondrite-normalized REE patterns for sample 349 (a) and sample 524 (b). Chondrite normalization according to Anders & Grevesse (1989), modified by Korotev (1996). 0.00 10000 11000 12000 13000 14000 15000 Migmatites from the lower series. sample 349, a total of 37 anal­ Hf (ppm) In yses were performed on 36 zircon grains. Areas with clear mag­ 12.0 matic textures were avoided, as they could represent inherited (c) Lowermost migmatites zones, so all the analyses were focused on rims or areas with homo­ geneous zoning that were presumably metamorphic. However, 10.0 o Sample 349 only seven analyses yielded ages younger than 400 Ma, whereas • Sample 524 8.0 the remaiuing 30 spots yielded ages between 600 and 2740Ma, E which were iuterpreted as inheritance. Owing to the scatter iu the G:l(J) 6.0 young ages (Fig. 5a, inset), obtaiuing a valid age from these seven 0 0 analyses is difficult.We can consider the two oldest analyses in this 4.0 0 group as outliers, and calculate the weighted average with the 524-5 349-4 remaiuing five analyses. However, the high MSWD obtained in • cD 0 2.0 349-11 this calculation (26) iudicates that these data do not represent a con­ • • • • sistent population. The best statistical estimate is obtained anchor­ 0.0 ing only three data to a common Pb composition of o. 857, giving a 0 20 40 60 80 100 120 140 younger iutercept age of 320± 13 Ma (Fig. 5a). Once again, the Yb/Gd high MSWD value (9.9) indicates that the considered analyses do not constitute a consistent population, so this number must be Fig. 7. Compositional diagrams for zircon from the lowennost migmatites regarded only as the upper limit for the age of metamorphism. (samples 349 and 524) (a) U v. Th; (b) Hfv. EulEu*; (c) Yb/Gd v. Ce/Sm. In sample 524, a total of 22 spot analyses also located at the rims The labelled analyses are those not used to obtain the mean age. were carried out on 20 zircon grains. Only seven analyses yielded Va riscan ages, sensu lata (i.e. less than 340 Ma). In this case, the two extreme values can be regarded as clear outliers (Fig. 5b, represented at the 2a level. Depending on the amount of data, the inset), and we calculate the weighted average using the rest of the mean square weighted deviation (MSWD) has to be lower than a analyses. Once more, the result produces a high MSWD (13) that theoretical value to confirm the statistical validity of the calcu- can be considerably lowered if we consider only four spots to cal­ 1ated age (Wendt & CarI1991). Ages younger than 1000Ma are culate the weighted mean, resultiug in an age of 315 ± 4 Ma, with an J reported using the 207-corrected 206Pbj2 8U ratio, whereas older acceptable MSWD value (2.0; Fig. 5b). The rest of the analyses ages are reported using the 204-corrected 207Pbj206Pb ratio. yielded inherited ages between 650 and 2660 Ma. 40 best estimate for the age of the cores was obtained fromfive anal­ (a) Sample 530 yses (Fig. 6a) yielding a mean age of 314.2± 1.5 Ma. with an MSWD of 0.11. Two of these analyses had moderate common Pb 35 • Antecrysts o Rims contents and were connected with the concordant analyses by 30 means of a line anchored to a common Pb composition of 0.S57. As regards the rims. a reliable estimation for their age was 25 obtained from 13 analyses, yielding a mean age of 311.0±0.9Ma "C with an MSWD of 0.3S. The remaining 13 analyses represented (!) :a 20 ages younger than 30S Ma and were probably attributed to varia­ >- ble radiogenic Pb loss as they were obtained from both cores and 15 • rims. The difference in age between cores and rims suggests that the former might represent antecrysts (Charlier et al. 2005); that 10 is, crystals formed slightly earlier on the crystallization path. In sample 420 (a gabbro from the Ceret stock), 24 spots were 5 analysed on 19 zircons with clear core-rim structures. The data were evenly distributed between 315 and 294 Ma (Fig. 6b), with the 0 cores usually older than the rims. The weighted mean obtained 0.00 0.20 0.40 0.60 O.BO 1.00 fromthe 12 core analyses (c. 309 Ma) had a high MSWD, suggest­ Th/U ing that the data contained more than one age population. In a fur­ 14.0 (b) ther appraisal, we used the Sambridge & Compston (1994) approach to extract these age populations, considering the core 12.0 analyses that were unaffected by Pb loss. By doing so, two age groups were established, namely an older one of 312.0 ± 1. 6 Ma

10.0 (MSWD � 0.15 for four analyses) and a younger one of

307.6± 1.5 Ma (MSWD � 0.24 for five analyses). As regards the jiB 0 rim analyses, the six younger values were clearly affected by Pb loss (Fig. 6b). However, the best estimate for their ages was Qj obtained from four other analyses, yielding a mean age of °6.0 307.0±3.5Ma with an MSWD of 0.10.

4.0 Migmatites from the Ceret stock contact aureole. In sample 529, a total of I 7 spot analyses were carried out in the same number of 2.0 zircon grains, focusing on the rims or areas with zoning that could be attributed to metamorphic zircon. The ages vary between 570 and 2700 Ma and were interpreted as inheritance. 0.0 0 5 10 15 20 25 30 35 40 Yb/Gd 10000 Zircon U, Th, Hf and REE composition U, Th, Hf and traceelement composition of zircon was used to gain 1000 insight into their petrogenesis and the analytical results are plotted Cl) in Figures 7-10. The interpretation of the results presented here .. will be discussed in the next section. "C''::: 100 I: 0 Migmatites from the lower series. Uranium concentrations in both ..I: 10 ..!:! migmatites (samples 349 and 524) are similar and range from 250 I: 0 to 11 OOppm (Fig. 7a). Thorium contents range between 2.5 and � Sppm in sample 349, whereas sample 524 has slightly higher val­ 'N ues. In Figure 7a, both samples define a compact cluster around the 0.1 0.01 ThIU ratio and the concentration of hafnium (Fig. 7b) in both migmatites is comparable. By contrast, the EulEu * anomaly is lower in sample 524 than in sample 349. Yh/Gd values (Fig. 7c) range between 35 and 120, with the lowest values corresponding to sample 524. The difference in the Ce/Sm ratio in both samples is Fig. 9. Compositional diagrams for zircon from the Sant Lloreny-La small, with sample 349 having slightly higher values. In the REE Jonquera tonalite (sample 530): (a) Th/Uv. Yb/Gdplot; (b) Yb/Gdv. Cel chondrite-nonnalized diagram (Fig. Sa and b), the patterns defmed Srn plot; (c) chondrite-normalized REE patterns. Chondrite normalization by the migmatite samples are typical of high-grade and magmatic as in Figure 8. zircon, with a progressive fractionation fromthe heavy to the light REE and two prominent anomalies in cerium (positive) and euro­ Sant Lloren,-La Jonquera tonalite and Ceret stock gabbro. In pium (negative). sample 530 (a tonalite from the Sant Lioreny-La Ionquera batho­ lith). 31 spot analyses were performed on 30 zircon grains. Single Sant Lloren,-La Jonquera tonalite and Ceret stock gabbro. In sam­ results range between 315 and 293 Ma. Taking into account the ple 530, the compositional difference between antecryst and rim CL texture of the zircon grains. most of the cores yielded the old­ analyses, including those affected by Pb loss, is discernible in only est ages. whereas data from the rims were usually younger. The some elements and elemental ratios. In Figure 9a, analyses define 0.25 two distinct trends; three out of five antecryst and two rim analyses (a) Sample 420 have a gentle negative slope, whereas the rest of the analyses define a steeper negative slope. In Figure 9b, there is a positive correlation • Old cores between the two ratios. The analyses cluster in two groups: one of 0 • Young cores the groups with three antecryst and two rim analyses at the low Yb/ o Rims Gd-Ce/Sm end, and the other groupwith the remaining analyses at 0 0.20 the high Yb/Gd-Ce/Sm end. In a chondrite-nonnalized plot (Fig.

• 9c), the rims (grey lines) show relatively homogeneous patterns, :s cOD whereas core analyses (black lines) have heterogeneous patterns W - with variable Eu and Ce anomalies. :s 0 CD W • • In sample 420, the compositional differences between the cores • 0 and the rims are more pronounced. In Figure lOa, the data defme a 0.1 5 . negative correlation, with cores having a higher Hf content and • ... 0 0 • lower values for the Eu anomaly than rims. In Figure lOb, the cor­ • relation of the data is positive, with the rims depleted in REE and Hf with respect to the cores. Furthennore, there is also a slight dif­ ference between the old and the young cores. By contrast, other compositional ratios such as the Ce/Sm and Yb/Gd ratios do not 0.10 show marked variations. This is evident in Figure 10c, where the 6000 8000 10000 12000 14000 core and rim patterns are identical and the only difference is the Hf (ppm) lower content in REE of the rims with respect to the cores. (b) 12000 Summary and discussion

Timing of the Variscan thermal evolution in the 11000 • • • • eastern Pyrenees .0 0 Sunrrnarizing the results obtained, a late Variscan thermal evolution 10000 is recorded in the eastern Pyrenees involving two distinct processes, • • an early migmatization and a late intrusion of igueous rocks . - �O • E • The earliest migmatization was coeval with the main defonna­ (Dj). ! 9000 tion It is recorded in the deepest levels of the Upper Proterozoic to Lower Cambrian series of the Roc de Frausa Massif. ... 11 J: 0 The Variscan partial melting history of the migmatites is poorly 1Ll • constrained by zircon geochronology as zircon recrystallization is 8000 0 generally limited to thin discontinuous rims. Nevertheless, the onset of crustal melting can be estimated to have occurred between 320±13 and 315±4Ma (Serpukhovian-Bashkirian). Furthermore, 7000 REE contents and various elemental ratios of these rims show a 0 500 1000 1500 L:REE relatively homogeneous composition, which suggests that the pro­ cess of zircon crystallization was by dissolution-precipitation. The compositional difference between the two analysed samples (349 (c) and 524) observed in Eu/Eu· and Ce/Sm suggests that zircon rims 6.0 l- from sample 349 precipitated from less evolved meltsthan those of sample 524, which precipitated from possibly less oxidized melts that had undergone substantial feldspar crystallization. 0 • The late intrusion of the composite Sant Lioreny-La Ionquera 0 plutonic complex (314-311 Ma) and the Ceret stock (312-307 Ma) 4.0 III D l- · was coeval with D2. The Sant Lioreny-La Ionquera plutonic sheet 0 0 E r . was emplaced between the medium-grade Upper Proterozoic­ I/) 0 - •• Lower Cambrian series and the low-grade Upper Ordovician­ III B U 0 0 Silurian metasediments. At the base of the La Ionquera sheet, � 0 2.0 l- tonalite magmas intruded between 314.2 ± 1.5 (core ages) and • 311.0±0.9 Ma (rim ages). The ages are significantly older than the age previously estimated (282± 5 Ma on Rb-Sr whole-rock, Cocherie 1984; 295± 7 Ma on U-Pb zircon, Maurel 2003). The variable REE contents of zircons (Fig. 9c), the heterogeneous pat­ I I 0.0 terns of the core analyses and the relatively homogeneous patterns 5 10 15 20 of the rims together with the variable size of the Eu and Ce anoma­ Yb/Gd lies support the interpretation of zircon cores as antecrysts. The gabbro-diorite Ceret stock intruded into lower crustal levels of the Fig. 10. Compositional diagrams for zircon from the Ceret stock gabbro Upper Proterozoic-Lower Cambrian series. Two magmatic pulses (sample 420) (a) Hfv. EuJEu* plot; (b) IREE v. Hfplot; (c) Yb/Gd v. Ce/Sm plot. are revealed by CL (Fig. 4), and are also demonstrated by the trace MASSIF PRE-VARISCAN METASEDIMENTS VARISCAN THERMAL EVENT CHEMICAL CENTRAL _ Carboniferous Migmatites t U/Pb �\ laouzas (Anatectic granite) • Silurian-Devonian GJ Granitoids • U-Th/P b '333:t 6 Ma Vialais o Upper Proterozoic-Ordovician POST-VARISCAN MATERIALS C Rb/Sr la Salvetat Ma t '320 ± 3 PRE-VARISCAN GRANITOIDS o MESOZOIC-PALEOGENE !Thiswork I '3�����a D Orthogneiss " Fault Monlale t324 ± 3 Ma '327±7MJ Bay of Bisc.ay

Eaux-Chaudes +301 9 Ma

Ceret gab e [T'312 ±t. a liJllLlcI 2!r

Migmatites (lower series) 1::26\:t,\%�1

� atalan Coastal Ranges

50 100 km

SOOkm

Fig. 11. Sketch of the Variscan zonation in NE Iberia and southern France, modified from Druguet (2001), with the available ages of the migmatites and intrusive rocks. NPF, North Pyrenean Fault; Py, Pyrenees; CCR, Catalan Coastal Ranges; MN, Montagne Noire.

element compositional differences between non-luminescent cores zirconium was retained in the pre-existing zircon grains and was and luminescent rims of zircons (Fig. 10). The non-luminescent barely dissolved during the migmatization event, with the result cores correspond to an early magmatic pulse that occurred at that isotopic re-equilibration was incomplete. 312 ± 1.6 Ma. They grew from a more evolved magma where most of the plagioclase had already crystallized, in accordance with the lower values for Eu anomalies. The young ages obtained from the Comparison with the Variscan segment of the cores (307.6± 1.5 Ma) probably represent lead loss. The lumines­ Pyrenees cent rims correspond to a second pulse that took place at 307.0±3.5 Ma. They originated from a second and less evolved The late Variscan crustal heating recorded in the eastern Pyrenees magma where plagioclase had not completely crystallized, as sug­ has also been observed in the more western parts of the Pyrenees, gested by the lower Hf content and the shallower Eu anomaly (Fig. such as the deep-seated intrusive rocks of the Ax granite in the lOa). The absence of meso- and microscopic evidence of physical Aston Massif and the deforrued deep-seated granite and charnock­ mixing (mingling) suggests that the mixture was complete; there­ ite in the Agly Massif (Fig. 11). They yield ages between 321 and fore, the existence of these two magmaticpulses is recorded only in 314 Ma (Table I) similar to those obtained for the early partial zircon. In summary, zircon geochemistry suggests a complex mag­ melting episode recorded in the deepest migmatites of the Roc de matic history for the Sant Lioreny-La Ionquera suite and the gab­ Frausa Massif (320-315 Ma). However, younger U-Pb ages bro-diorite Ceret stock. This history includes several pulses of (310±25 and 295 ±5 Ma) have been obtained for the deepest gran­ magma and mixing of magmas with different geochemical charac­ ulitic paragneisses of the Saint Barthelemy Massif (Delaperriere teristics. Moreover, the chemistry of zircon supports the proposal et al. 1994). of Viii! et al. (2005) that these two igneous bodies are geochemi­ This episode was followed by the emplacement of mafic rocks in cally diverse and they belong to genetically distinct igneous suites the middle crust subordinate to large calc-alkaline plutons in the produced in different levels of the lithosphere. upper crust. Few geochronological data are available for the for­ In the migmatites from the Ceret gabbro contact aureole, mer. In the Agly Massif, the Tournefort diorite yields a U-Pb age Variscan rims around inherited zircon are absent. This suggests that of30S.3± 1.2 Ma (Olivier et al. 200S). This age is younger than that Table 1. Available ages for migmatites and intrusive rocks of the Varisean Beltin the Pyrenees, Montagne Noire and Catalan Coastal Ranges

Locality Age (Ma) Reference Method Technique

PYRENEES Migmatites Roe de Frausa Massif Migmatites (Lower Series) 320± 13 This study U-Pb zircon SHRIMP-RG 315±4 This study U-Pb zircon SHRIMP-RG Saint Barlhelemy Paragneiss 31O±25 Delaperriere et a!.1994 U-Pb zircon or monazite 295±5 Delaperriere eta!. 1994 U-Pb zircon or monazite Deep crustal intrusive rocks Aston Massif Axgranite 321±7 Denele et a!. 2007 U-Pb zircon Agly Massif Defolllled deep-seated granite 317±3 Olivier et a!. 2004 U-Pb zircon ID-TIMS Ansignan charnockite 314±6 Respaut & Lancelot19S3 U-Pb zircon 315±5 Postaire19S4 U-Pb zircon Mid-crustal intrusive rocks Agly Massif TOUlllefort diorite 30S.3 ±1.2 Olivier eta!. 200S U-Pb zircon ID-TIMS Roe de FrausaMassif Ceret gabbro 312± 1.6 This study U-Pb zircon SHRIMP-RG 307.6± 1.5 This study U-Pb zircon SHRIMP-RG 307±3.5 This study U-Pb zircon SHRIMP-RG Calc-alkaline upper-crustal intrusive rocks La Jonquera-Sant Lloreny 2S2±5 Cocherie19S4 "Whole-rock Rb/Sr 295±7 Maurel2003 U-Pb zircon SIMS 314.2± 1.5 This study U-Pb zircon SHRIMP-RG 311.0±0.9 This study U-Pb zircon SHRIMP-RG SaintArnac 303.6±4.7 Olivier et a!.200S U-Pb zircon ID-TIMS Querignt 307±2 Roberts et a!.2000 U-Pb zircon Andorra, Mont-Louis 305±3 Romer & Soler 1995 U-Pb titanite 305±5 Maurel et a!.2004 U-Pb zircon SIMS Bassies 312±3 Paquette eta!. 1997 U-Pb zircon Eastern Cauterets 301±7 Temet eta!. 2004 U-Pb zircon Eaux-Chaudes 301±9 Temet eta!. 2004 U-Pb zircon Borderes 309±4 Gleizes et a!.2006 U-Pb zircon SIMS Aya (alkaline) 267.1± 1.1 Denele et a!.2011 U-Pb zircon LA-ICP-MS MONTAGNE NOIRE Migmatites La Salvetat 327±7 Faure eta!.2010 U-Th-Pb monazite EPMA Ourtigas 326±4 Faure eta!.2010 U-Th-Pb monazite EPMA Ana tectic granite Laouzas 333±6 Faure eta!. 2010 U-Th-Pb monazite EPMA Montalet granite 324±3 Faure eta!. 2010 U-Pb zircon SIMS 327±7 Faure eta!. 2010 U-Th-Pb monazite EPMA Late to post-migmatitic granite Angles 325±7 Faure eta!. 2010 U-Th-Pb monazite EPMA Vialais 320±3 Faure eta!. 2010 U-Th-Pb monazite EPMA Soulie 31S±4 Faure eta!. 2010 U-Th-Pb monazite EPMA

CATALAN COASTAL RANGES Montseny-Guilleries Massif Susqueda diorite 323.6±2.S Martinez et a!.200S U-Pb zircon SHRIMP-RG Granite 305.9±1.5 Martinez et a!.200S U-Pb zircon SHRIMP-RG Leucogranite 305.3±1.9 Martinez et a!.200S U-Pb zircon SHRIMP-RG 301.5±1.7 Martinez et a!.200S U-Pb zircon SHRIMP-RG 299.0±2.3 Martinez et a!.200S U-Pb zircon SHRIMP-RG

ID-TIMS, isotope dilution thermal ionization mass spectrometry; SIMS, secondaryionization mass spectrometry;LA-ICP-MS, laser ablation inductively coupled plasma mass spectrometry; EPMA, electron microprobe analysis. ofthe fi rst magmaticpulse ofthe Ceret gabbro-diorite (312 ±1.6 Ma, and imaging, zircon analyses and instrument tuning. We are indebted to J. recorded in the antecrystic cores) but comparable with the second A. Muiioz and J. M. Casas for invaluable comments on the paper. We are one, dated at 307.0±3.5Ma (recorded in the rims). The emplace­ also grateful to J. von Raumer for his detailed and constructive criticism and ment ofthe large upper crusta1 calc-alka1ine p1u tons of the Pyrenees for his help with the finalversion of the paper, and to an anonymous referee. could have lasted for about 15 myr. This episode could have been G. von Knorring reviewed the English style of the paper. diachronous (314-301 Ma) along the Pyrenees. The ages obtained References in this study for the Sant Llorenry-La Jonquera plutonic complex ANDERS, & GREVESSE, 1989. are in the older range if we consider those yielded by recent studies E. N. Abundances of the elements: Meteoritic and solar. Geochimica et Cosmochimica Acta, 53, 197-204. on other calc-alkaline intrusive bodies of the Pyrenees (between AUTRAN, A. & GUITARD, G. 1969. Mise en evidence de nappes hercyniennes de 312 to 301 Ma; see Fig. 11 and Table 1). Moreover, the ages style penninique dans la serie metamOlphique du massif du Roe de France obtained in this study record a multiple intrusion history that has (pyrenees orientales): Liaison avec la nappe du Canigou. Comptes Rendus de l'Acadhnie des Sciences, not been reported to date. 269, 24 79-24 99. CARRERAS, I. & DEBAT, P. (coords) 1996. La Tectonique Hercynienne. In : BARNOLAS, A. & CHIRON, I.C. (eds) Sy nthese geologique et geophpique Correlation with the Va riscan segment of des Pyrenees. Vol. 1: In troduction . Geophysique. Cycle Hercynien. Edition BRGM-ITGE, Orleans and Madrid, 585-677. Montagne Noire (SE France) and the Catalan CASTI14EIRAS, P., NAVIDAD, M., LIESA, M., CARRERAS, I. & CASAS, I.M. 2008. V-Pb Coastal Ranges (NE Iberia) zircon ages (SHRIMP) for Cadomian and Early Ordovician magmatism in the eas tern Pyrenees: New insights into the pre-Variscan evolution of the It is tempting to correlate the observations from the Pyrenean northern Gondwana margin. Tectonophysics, 461, 228-239. CHARLIER, B.L.A., WILSON, CJ.N., 10WENSTERN, I.B., BLAKE, S., VANCALSTEREN, Variscides with those of the neighbouring areas such as Montagne P.W.C. & DAVIDSON, I.P. 2005. Magma generation at a large, hyperactive Noire and theCatalan Coastal Ranges. The available data formigmatites silicic volcano (Taupo, New Zealand) revealed by V-Th and V-Pb system­ and intrusive rocks (Table 1) point to older ages and longer thennal atics in zircons. Jo urnalof Petrology, 46, 3-32. histories tothe NE (Fig. 11). The chronological relationships between CIRES, I., MORALES, v., LIESA, M., CARRERAS, I., CARRERAS, I., ESCUER, I. & PUJADAS, I. 1994 . Memoria explicativa del mapageol6gico de Espaiia, hoja the migmatitic and magmatic episodes could indicate a zonation con­ de LaJo nquera (2 20), scale 1:50000. Instituto Tecnol6gico Geominero de sistent -..vith the foreland propagation of the orogen from NE to SW. Espafia, Madrid. Similarly, the time-space distribution of migmatites and plutons COCHERIE, A. 1984 . In teraction manteau-croute: Son role dans la gen€se along the Pyrenees, the Coastal Ranges and Montagne Noire is in d'associations plutoniques calco-alcalines, contraintes geochimiques (elements en traces et isotopes du strontium et de l'oxygene) . line -..vith the relative position of the hinterland and foreland of the PhD thesis, Vniversite de Rennes . southern branch of the Variscan belt, corresponding to the south­ DEBoN, F., ENRIQUE, P. & AUTRAN, A. 1995. Magmatisme Hercynian. In : western polarity of Variscan structures in the three areas (Martinez BARNOLAS, A. & CHIRON, I.C. (eds) Sy nthese geologique et geophysique Catalln 1990; Carreras & Debat 1996; Matte 2001). des Pyrenees. Vol. 1: In troduction . Geophysique. Cycle Hercynien. Edition BRGM-ITGE, Orleans and Madrid, 303-359. DELAPERRIERE, E., DE SAINT-BLANQUAT, M., BRUNEL, M. & LANCELOT, I. 1994 . Geoehronologie V-Pb sur zircons et monazites dans le massif du Saint Conclusions Barthelemy (Pyrenees, France): Discussion des ages des evenements var­ iues et pre-varisques. Bulletin de la Societe Geologique de France, 165, New U-Pb SHRIMP zircon dating on late Va riscan migmatites and 101-112. igneous rocks from the eastern Pyrenees, combined with trace ele­ DENELE, Y., OLIVIER, P., GLEIZES, G. & BARBEY, P. 2007. The Hospitalet gneiss ment chemistry of zircon, allowed us to see two episodes in the dome (Pyrenees) revisited: lateral flow during Variscan transpression in the thermal evolution of the area. The fIrst, an early migmatization in middle crust. Terra Nova, 19, 445-453. DENELE, Y., PAQUETTE, I.L., OLIVIER, PH. & BARBEY, P. 2011. Pennian granites in the deepest crustal levels of Roc de Frausa Massif, occurred during the Pyrenees: the Aya pluton (Basque Count!)'). Terra Nova, 24, 105--113. c. the Serpukhovian-Bashkirian (320-315Ma) over a time span of DRUGUET, E. 2001. Development of high thennal gradients by coeval transpres­ 5myr, coeval with the main deformation event (DJ). This thennal sion and magmatism during the Variscan orogen: Insights from the Cap de episode is also responsible for the intrusion of deep-seated grani­ Creus (eastern Pyrenees). Te ctonophysics, 332, 275-293 . FAURE, M., COCHERIE, A., BEMEZEME, E., CHARLES, N. & ROSSI, P. 2010. Middle toids in other Pyrenean massifs (Agly and Aston). The second epi­ Carboniferous crustal melting in the Variscan Belt: New insights from sode, late intrusion during the Late Bashkirian-Moscovian V-Th-Pb\O\ monazite and V-Pb zircon ages of the Montagne Noire Axial (314-307Ma) synchronous with a late defonnation event (D2), cor­ Zone (southern French Massif Central). Gondwana Research , 18, 653-673. responds to the emplacement of the calc-alkaline La Jonquera-Sant GLEIZES, G., CREVON, G., ASRAT, A. & BARBEY, P. 2006. Structure, age and Llorenry plutonic complex and the Ceret gabbro-diorite stock in mode of emplacement of the Hercynian Borderes-Louron pluton (central Pyrenees, Frances). In ternational Jo urnal of Earth Sciences, 95, 1039- upper and middle crustal levels, respectively. CL, transmitted light 1052. microscope and trace element chemistry of zircon show that two GUITARD, G., VIELZEUF, D. & MARTfNEZ, F. 1995. Metamorphisme Hercynian. magmatic pulses can be recorded in the Ceret gabbro-diorite sepa­ In : BARNOLAS, A. & CHIRON, I.C. (eds) Sy nth€se geologique et geophysique rated by a time span of c. 5 myr. Migmatites were fonned arOlllld des Pyrenees. Vol. 1: In troduction . Geophysique. Cycle Hercynien. Edition BRGM-ITGE, Orleans and Madrid, 303-359. the Ceret gabbro contact aureole but the absence of Va riscan rims HOLLAND, T.1.B. & POWELL, R. 1998. An internally-consistent thennodynamic around inherited zircon prevented us from dating the episodes. data set for phases ofpetrologic interest. Journal of Metamorphic Geology, Space-time correlation of the Pyrenees with neighbouring areas 16, 309-34 3. (Catalan Coastal Ranges and Montagne Noire) allows us to con­ KOROTEV, R.L. 1996. A self-consistent compilation of elemental concentration data for 93 geoehemical refe rence samples. Geostandards Newsletter, 20, struct a NW -SE-trending zonation model. 217-24 5. LIESA, M. & CARRERAS, I. 1989. 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