Las peridotitas y piroxenitas del Complejo catazonal del Cabo Ortegal

[Résumë] Les roches ultramafiques de l'unité supérieure du Complexe Catazonal du Cabo Ortegal montrent un bel exemple d'un manteau supérieur composite. Ce manteau est constitué d 'importantes masses de pyroxénites interlités dans des harzburgites résiduelles. Dans le massif d'Herbeira, ces pyroxénites constituent une lame d'au moins 300 m d'épaisseur continue sur plus de 3 km de longueur dans laquelle alternent de niveaux d'épaisseur tres variable (2 mm a 3 mm) de pyroxénite et de dunite, sans aucune rythmicité apparente. Ces rubans ne sont en général pas zonés mais peuvent localement montrer des enrichissements en clinopyroxene et spinelle ala base de certains bancs. Al'échelle du massif, cette lame de pyroxénite a une structure en amande pouvant résulter d 'un processus de boudinage compatible avec un cisaillement du Nord vers le Sud de l'ensemble du massif ultramafique. Les traces de cette deformation sont bien visibles dans toutes les roches situées ala périphérie de la lame de pyroxénite qui montrent a toute échelle, des plis soclinaux, des bandes de cisaillement mylonitiques, parfois de type C' et des failles normales associées au boudinage des niveaux pyroxénitiques. Cette déformation est cellée par la mise en place de filons de pyroxénite agrenat. Elle prédate le charriage de l'ensemble du massif sur les granulites. Ces roches ultramafiques ont subi une évolution complexe impliquant un reéquilibrage de l'ensemble des pnases primaires a une température voisine de 800 oC et aune pression élevée, supérieure a 15 kbar, évolution métamorphique de haut degré similaire a celle qu 'ont subi les granulites et éclogites encaissantes. Puis ces roches ont subi un reéquilibrage plus tardif dans des conditions du facies amphibolites[Resumen] Las rocas ultramáficas de la unidad superior del Complejo Catazonal del Cabo Ortegal muestran un buen ejemplo de manto superior compuesto. Se trata de un fragmento de manto terrestre constituido por una gran cantidad de piroxenitas intercaladas en harzburgitas residuales. En el macizo de Herbeira las piroxenitas constituyen una lámina de al menos 300 m de espesor, continua a lo largo de más de 3km de longitud, en la que alternan niveles de espesor variable (2 mm.a 3 m) de piroxenita y de dunita sin ninguna ritmicidad aparente. Los niveles generalmente no presentan zonaci6n aunque localmente pueden aparecer enriquecimientos en c1inopiroxeno y espinela en la base de algunos de ellos. A la escala del macizo la lámina de piroxenita presenta una estructura aproximadamente lenticular que podría ser el resultado de un proceso de boudinage compatible con una cizalla de Norte a Sur del conjunto del macizo ultramáfico. Las trazas de esta deformación son bien visibles en todas las rocas situadas en la periferia de la lámina piroxenítica., las cuales muestran a diferentes escalas pliegues isoclinales, bandas de cizalla miloníticas, en ocasiones de tipo C' así como fallas normales asociadas al boudinage de los niveles piroxeníticos. Esta deformación aparece sellada por el emplazamiento de filones de piroxenita con granate y precede al cabalgamiento del macizo sobre las granulitas. Las rocas ultramáficas han sufrido una evolución compleja con reequilibración del conjunto de fases primarias a una temperatura próxima a los 800 oC y a una presión elevada, superior a 15 kbar, evolución metamórfica de alto grado similar a la que se observa en las granulitas y eclogitas encajantes, seguida de una reequilibración tardía en condiciones de la facies de las anfibolitas.[Abstract] The ultramafic rocks from the upper unit of the Catazonal Complex of Cabo Ortegal show a good eXClmple of composite upper mande. This mande fragment is made of a great amount of pyroxenites intercalated within residual harzburgites. At the Herbeira massif these pyroxenites form a continuous sheet of more than 300 m in width by 3 km length. Pyroxenite and dunite levels, highly variable in width (2 mm to 3 m), alternate within the pyroxenitc sheet without any apparent rhytmicity. These levels generally are not zoned but there may be local enrichments in c1inopyroxene and spinel at the base of sorne of them. The pyroxenite sheet exhibits a near lenticular (almond) structure at the massif scale. This might be due to a boudinage process compatible with a Southwards shear movement of the ultramafic massif. The traces of this deformation are best observed in the rocks surrounding the pyroxenite sheet, where isoc1inal folds, mylonitic shear bands -C' bands in sorne cases-, and normal faults associated with the boudinage of pyroxenitic layers, are visible at different scales. This deformation is sealed by the emplacement of garnetbearing pyroxenite veins which occurred prior to the thrust emplacement of the ultramafic massif onto. the structurally underlying granulites. The ultramafic rocks underwent a complex evolution involving reequilibrium of the primary phases at a temperature of ca.800 oC and relatively high-pressure conditions (> 15 kbar). This recrystallization, comparable to that observed in the surrounding granulites and eclogites, was followed by a later event under amphibolite-Jacies conditions

Reliable Circuit Design with Nanowire Arrays

The emergence of different fabrication techniques of silicon nanowires (SiNWs) raises the question of finding a suitable architectural organization of circuits based on them. Despite the possibility of building conventional CMOS circuits with SiNWs, the ability to arrange them into regular arrays, called crossbars, offers the opportunity to achieve higher integration densities. In such arrays, molecular switches or phase-change materials are grafted at the crosspoints, i.e., the crossing nanowires, in order to perform computation or storage. Given the fact that the technology is not mature, a hybridization of CMOS circuits with nanowire arrays seems to be the most promising approach. This chapter addresses the impact of variability on the nanowires in circuit designs based on the hybrid CMOS-SiNW crossbar approach

RF characterization of the substrate coupling noise between TSV and active devices in 3D integrated circuits

International audienc

Natural History of the Pine Processionary Moth,Thaumetopoea pityocampa

International audienc

Natural History of the Pine Processionary Moth,Thaumetopoea pityocampa

International audienc

Natural history of the Processionary Moths (Thaumetopoea spp.): New insights in relation to climate change

La partie est intégrée dans le Chapter 2: Natural history of the Processionary Moths (Thaumetopoea spp.): New insights in relation to climate changeInternational audienceIt is difficult to find a genus of Lepidoptera showing the high variability of life history traits observed in Thaumetopoea. There are typical summer feeding close to winter feeding species, and in one special case a recent switch has been detected even within one species, the pine processionary moth, indicating that the natural history traits are constantly evolving at a fast rate. There are species adapted to cold conditions of high mountains and high latitude close to truly Mediterranean and sub-desert region species. All species have gregarious behaviour as larva and are protected against vertebrate predators by urticating setae