Pseudo-two-girdles c-axis fabric patterns in a quartz-feldspar mylonite (Costabona granodiorite, Canigo massif)

An example of the relationship that exist between the preferred crystaliografic orientation of quartz grains and the attitude of the mylonite foliation of quartz-feldspar mylonites is described. These rocks are the result of the inhomogeneous deformation under low-grade metamorphic conditions of a late Hercynian granodiorite, intruded into the gneisses of the slopes of the Canig massif (Eastern Pyrenees). The Costabona mylonites have a quartz c-axis fabric in pseudo-twogirdles symmetrical with respect to the mylonite foliation and perpendicular to the shearband systems which produce an extensional crenulation of the mylonite foliation

Estudi microtermomètric dels filons de quars de les Esquerdes de Rojà, Massís de Canigó, Pirineu Oriental

Els materials pre-hercinians i el granit de Costabona estan travessats per un conjunt de filons de quars de fms a 15 km de longitud, coneguts com a "Esquerdes de Roja". Aquests filons estan localment afectats per un sistema de bandes milonítiques i per un altre posterior de fractures. A partir de l'anilisi microtermometrica de les inclusions fluides prirniries en quars, ha estat obtinguda una temperatura de formació de l'ordre de + 280° C per la major part del quars, i una temperatura de + 250° C per als monocristaüs que omplen esquerdes i cavitats. Els filons s'haurien format a partir de solucions mineralitzants que contenien Na+Ca++, K+ i, en menor proporció, Mg++.fins una salinitat total de l'ordre del 20°/en pes de la Na C

On the Upper Ordovician unconformity in the Pyrenees : new evidence from the La Cerdanya area

In recent years, contradictory reports about whether or not an unconformity exists at the base of the Upper Ordovician succession of the Pyrenees have been made. In the Cerdanya area (Central Pyrenees), good outcrop evidence for this unconformity is displayed at the base of the Rabassa conglomerates. In this area, the Upper Ordovician rocks overlie a tilted Cambro-Ordovician sequence, displaying an angular unconformity and indicating a break in the stratigraphic series. Moreover, the existence of such an unconformity is supported by the distribution of Variscan minor structures, suggesting that the Cambro-Ordovician and the Upper Ordovician strata initially had different orientations before the main Variscan folding

Mineralización estratiforme de Pb-Zn-Cu en el Paleozoico de Bassegoda (Pirineo Oriental)

Al Sur del pico de Bassegoda existe una mineralización estratiforme de galena, esfalerita y pirita con calcopirita y arsenopirita, en forma de diseminaciones y lentejones masivos, situadas dentro de un tramo de 10 metros de micaesquistos y dolomias negras. Estos niveles mineralizados se hallan en el contacto entre micaesquistos y dolomias masivas que contienen piroclastos ácidos. Tanto el tipo de depósito como la litologia encajante, permiten correlacionar esta mineralización con un conjunto de concentraciones metalicas estratiformes y estratoligadas del Cambro-Ordovicico del NE de Cataluñ

New palaeobotanical data from Carboniferous Culm deposits constrain the age of the Variscan deformation in the eastern Pyrenees

The pre-Variscan rocks of the Pyrenees exhibit a polyphase deformation linked to the Variscan crustal shortening and a low-pressure-high-temperature metamorphism. However, there is scarce chronostratigraphic evidence of this Variscan deformation. In the Pyrenean low-grade metamorphic domains, maximum ages have been provided by the synorogenic Carboniferous Culm deposits. In medium- to high-grade metamorphic areas, the Variscan regional metamorphism or intrusive magmatic bodies constrain the age of the main Variscan deformation structures. However, these data usually provide a minimum age. Here, we present new palaeobotanical records that assign a Namurian age to the base of the Culm deposits of la Cerdanya in the eastern Pyrenees. This dating is based on the co-occurrence of the sphenopsids Archaeocalamites radiatus, Mesocalamites cistiiformis and the seed of Cardiocarpus sp. The plant remains were found in sandstone facies produced by high-density turbidity flows of a deep-sea fan system. The new biostratigraphic information constrains the age of the Carboniferous Culm succession in the eastern Pyrenees

New paleobotanical data from Carboniferous Culm deposits constrain the age of the Variscan deformation in the Eastern Pyrenees

The pre-Variscan rocks of the Pyrenees exhibit a polyphase deformation linked to the Variscan crustal shortening and a low-pressure-high-temperature metamorphism. However, there is scarce chronostratigraphic evidence of this Variscan deformation in the Pyrenees. In low-grade metamorphic domains, maximum ages have been provided by the synorogenic Carboniferous Culm deposits. In medium- to high-grade metamorphic areas, the geochronological ages of the Variscan regional metamorphism or intrusive magmatic bodies constrain the age of the main Variscan deformation structures. However, these data usually provide a minimum age. Here, we present new palaeobotanical records that assign a Namurian age to the base of the Culm deposits of La Cerdanya in the eastern Pyrenees. This dating is based on the co-occurrence of the sphenopsids Archaeocalamites radiatus, Mesocalamites cistiiformis and the seed Cardiocarpus sp. The plant remains were found in sandstone facies produced by high-density turbidity flows of a deep-sea fan system. The new biostratigraphic information constrains the age of the Carboniferous Culm succession in the eastern Pyrenees

Estructura geològica

L'illa de Cabrera, situada al sud de Mallorca, és la continuació de les Serres de Llevant i hi té grans similituds geològiques. La sèrie estratigràfica s'inicia amb les fàcies keuper del Triàsic. El Juràssic inferior és representat per fàcies de plataforma marina i la resta del Juràssic i Cretaci inferior són enregistrats per una sedimentació marina corresponent a ambients de talús, amb olistòlits i olistostromes, i conca. Després d'una llacuna estratigràfica important, la sedimentació es reprèn amb fàcies litorals de l'Eocè mitjà i superior. Novament hi ha interrupcions importants del registre sedimentari i només es troben uns pocs sediments del Miocè superior i del Quaternari. L'estructura de Cabrera ve determinada per l'existència de falles normals, encavalcaments i uns pocs plecs. Algunes falles normals són juràssiques i s'han desenvolupat sincrònicament amb la sedimentació de les fàcies de talús; només es descriuen les existents entre el Cap des Morobutí i la Cova Blava, però de ben segur que algunes falles normals d'altres llocs de Cabrera tenen el mateix origen. D'altres falles normals tallen les roques eocenes i per tant hi són posteriors; se suggereix que aquestes podrien ser tardimiocenes o pliocenes. Si bé les falles normals són les estructures més evidents de Cabrera, considerem que els encavalcaments juguen un paper determinant. L'existència dels encavalcaments d'Es Penyal Blanc, d'Es Burrí i del Clot del Guix suggereixen dividir Cabrera en dues unitats estructurals diferents. La unitat inferior és la més gran i està constituïda per la sèrie estratigràfica sencera. La unitat superior ocupa les parts altes de l'illa i només està constituïda per roques de la fàcies de plataforma del Juràssic inferior.The Cabrera Island is located South of Mallorca and has many geologic similarities with the Serres de Llevant. The older rocks in Cabrera belongs to Triassic (Keuper facies). They are folowed by Early Jurassic marine shelf rocks, Middle and Late Jurassic marly limestones of submarine talus facies, and Lower Cretaceous basin marls. Big stratigraphic gaps exist and Cenozoic sedimentary record is discontinous; it includes Eocene litoral calcarenites, and Upper Miocene and Quaternary sediments. Normal faults are the more conspicous structures of Cabrera Island. A conjugated normal fault system Middle and Late Jurassic in age has been described between the Cap des Morobutí and the Cova Blava. Syngenetic faults other then those probably exist in other localities in Cabrera. Another set of normal faults cut Eocene rocks, thus they are post-Eocene in age. It is suggested they could be Latemost Miocene and Pliocene in age. Thrust faults play a major role in the structure of Cabrera Island. Es Penyal Blanc, Es B urrí and the Clot des Guix thrusts are clearly exposed, they suggest the existence of two different structural units. The lower one is the biggest and consists of the complete stratigraphic sequence. The upper one outcrops in the higher parts of the island and only consists of Early Jurassic shelf rocks

Review of the Ediacaran-Lower Ordovician (pre-Sardic) stratigraphic framework of the Eastern Pyrenees, southwestern Europe

The Ediacaran-Lower Ordovician successions exposed in the Eastern Pyrenees are updated and revised based on recent U-Pb zircon radiometric ages, intertonguing relationships of carbonate-dominated strata, and onlapping patterns marking the top of volcano-sedimentary complexes. A stratigraphic comparison with neighbouring pre-Variscan outcrops from the Montagne Noire (southern French Massif Central) and Sardinia is related to i) the absence of Cadomian deformation close to the Ediacaran-Cambrian boundary interval; ii) the presence of an episodic, Cadomian-related, acidic-dominant volcanism related to carbonate production punctuating the Ediacaran-Cambrian transition, similar to that recorded in the northern Montagne Noire; and iii) the lack of Guzhangian (Cambrian Epoch 3) regressive shoal complexes present in the Montagne Noire and probably in Sardinia

The Roses giant quartz vein (Cap de Creus, Eastern Pyrenees): Geology and fluid inclusion data.

The Pyrenean Axial Zone is characterized by thick series of metasedimentary and orthogneissic materials derived from pre-Variscan rocks. These sequences were intruded by large bodies of Variscan granitoids, some exposed after the Alpine orogeny. In the Eastern Pyrenees, a number of quartz veins of kilometric length and metric to decametric width, are present. Although these veins are mostly hosted by Variscan and pre-Variscan rocks, in the utheastern limit of the Roc de Frausa Massif, large fault related quartz bodies rossc utting Mesozoic sedimentary rocks, have also been recognized Liesa, 1988). The Roses giant quartz vein constitutes a remarkable example of the seregional scale quartz veins. It is located at the south ernportion of the Cap de Creus Massif, extending for 2700 mand reaching widths up to 25m. Apparently, the vein continues towards the NW depicting a much longer structure