Geología de la parte sur de la Sierra de San Luis y granitoides asociados, Argentina

The lower Palaeozoic basement of the southern part of Sierra de San Luis, Argentina, is made up of metamorphic rocks, granitoids and ultramafic rocks. The metamorphic grade ranges from the lower limit of greenschist facies through the upper limit of amphibolite facies, in apparent transition. The lower grade metamorphic rocks include slates, metavolcanics, metaconglomerates, quartzites and phyllites. Rocks with intermediate metamorphism are biotite-quartz-oligoclase schists with abundant pegmatoid veins. The higher grade metamorphism is represented by gneisses, amphibolites and migmatites, to which mafic and ultramafic bodies are associated. Three deformation phases have been recognized, being the last one (D3), of ordovician age, responsible of the most marked structures.The granitoids were grouped into pre-, syn- and post-kynematic bodies respect to D3. The pre-kynematic granitoids are located within the belt of lower grade metamorphic rocks and are composed of tonalites, granodiorites and monzogranites, strongly deformed. Their age is unknown. The syn-kynematic bodies are mainly garnet-moscovite-bearing leucogranodiorites. They show low thermal and rheological contrasts respect to the country rocks, and the age is 454 ± 21 m.a. The post-kynematic granitoids are mainly monzogranites with K-feldspar megacrysts and abundant sphene. They are subcircular and discordant, and are associated with an extensional regime. Their age is comprised between 423 and 320 m.a., and corresponds to the end of the Famatinian cycle.El basamento cristalino de la parte sur de la Sierra de San Luis, de edad Paleozoico Inferior, está constituido por rocas metamórficas, granitoides y rocas ultramáficas. El grado de metamorfismo varía desde la parte baja de esquistos verdes hasta la parte alta de la facies anfibolita, siendo sus relaciones de aparente transicionalidad. Las rocas con menor grado metamórfico consisten en pizarras, metavolcanitas, metaconglomerados, cuarcitas y filitas. El grado metamórfico intermedio está representado por esquistos biotíticos cuarzo oligoclásicos con abundantes venas pegmatoideas. El más alto grado metamórfico está representado por gneises, anfibolitas y migmatitas y al mismo están asociados los cuerpos máficos a ultramáficos. Se han reconocido tres fases de deformación, siendo la última (D3), ordovícica, la que imprime la estructura más marcada.Los granitoides se han agrupado respecto de D3 en pre-, sin- y post-cinemáticos. Los primeros se encuentran en las fajas de bajo grado metamórfico y están compuestos por tonalitas, granodioritas y monzogranitos, fuertemente deformados. Su edad se desconoce. Los cuerpos sin-cinemáticos son predominantemente leucogranodioritas con granate y muscovita. Muestran bajo contraste reológico y térmico con respecto a la caja. Su edad es de 454 ± 21 m.a. Los granitoides post-cinemáticos son comúnmente monzogranitos con megacristales de feldespato potásico, ricos en titanita. Son discordantes, subcirculares y están asociados a una fase distensiva. Su edad está comprendida entre 423 y 320 m.a. y marca la finalización del ciclo Famatiniano

Erosion Surface and Granitic Morphology in the Sierra de Lihuel Calel, Province of La Pampa, Argentina

Fil: Aguilera, Emilia Yolanda. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Sato, Ana María. Centro de Investigaciones Geológicas (CIG). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Llambías, Eduardo Jorge. Centro de Investigaciones Geológicas (CIG). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Tickyj, Hugo. Departamento de Ciencias Naturales. Facultad de Ciencias Exactas y Naturales. Universidad Nacional de La Pampa; Argentin

Effect of fluorine in the synergism Co-Mo via hydrogen spillover on the hydrodesul-phurization of refractory molecules

The influence of fluorine concentration on the synergism between Co/γ-Al2O3 and MoAy-Al2O3 stacked beds separated by 3-mm of γ-Al2O3Fx (x = 0 - 2.5%), in the hydrodesulphurization of refractory molecules contained in gasoil, under operating conditions similar to those of industry, was studied. The results shown, that the synergism increases with F content, reaching a maximum at 0.8% of fluorine, which it is related to changes in zero point of charge (ZPC) and acid strength, due to the incorporation of fluorine. The conversion of most refractory molecule reported is favoured by fluorine.The authors wish to thank: FONDECYT Project No 1095120 and 1130749, PUCV DI 127.760, ENAPPeer Reviewe

Influence of the support and pore- generating method on the metal dispersion of Pt- catalysts for VOC oxidation

Trabajo presentado en el XIII Congreso Mexicano de Catálisis, celebrado en Puerto Vallarta (México) del 16 al 19 de abril de 2013.Peer Reviewe

Influence of the support and pore-generating method on the metal dispersion of Pt-catalysts for VOC oxidation

Trabajo presentado en el IV Congreso Internacional y el XIII Congreso Mexicano de Catálisis (2013), celebrado en Puerto Vallarta (México) del 16 al 19 de abril de 2013.N

Preparation of Pt-TiO2 catalysts for VOC abatement. Influence of the method of preparation

Trabajo presentado en el Symposium in honour of Ramôa Ribeiro (Catalysis: From the Active Site to the Process), celebrado en Lisboa el 8 y 9 de octubre de 2012.Industrially applied catalysts for decontamination processes are usually formed by supported noble metals, and their activities are related to the metal dispersion on the surface of the porous support and to the accessibility of the gases to the active phase which is related with its porosity. The optimization of these parameters is a goal of industrial catalysis in order to improve the activity of the system while taking into account that the cost of the catalyst is minimized. In this work the performance in the catalytic combustion of formaldehyde of a series of supported Pt catalysts with the same composition and prepared by different methods are studied and their behavior are related with their textural properties and the dispersion of the active phase.N

Progressive growth of the Cerro Bayo cryptodome, Chachahuén volcano, Argentina—implications for viscous magma emplacement

Cryptodome and dome collapse is associated with volcanic hazards, such as explosive eruptions, pyroclastic density currents, and volcanic edifice collapse. The study of the growth and evolution of volcanic domes provides vital information on the link between dome growth and the development of weakness zones that may cause collapse. The Cerro Bayo cryptodome is superbly exposed in the eroded Miocene Chachahuén volcano in the Neuquén basin, Argentina. Cerro Bayo is a &gt;0.3-km3 trachyandesitic cryptodome that intruded within the uppermost kilometer of the Chachahuén volcano. Here we investigate the emplacement of the Cerro Bayo cryptodome using structural mapping, photogrammetry and measurement of magma flow indicators, brittle deformation features, and magnetic fabrics with anisotropy of magnetic susceptibility. Magma flow fabrics near the margin are concentric and indicate contact-parallel flow and internal inflation of the body. Magmatic and magnetic fabrics and fracture patterns in the interior of the cryptodome are more complex and outline several structural domains. These domains are separated by magmatic shear zones that accommodated intrusion growth. The shear zones locally overprint the earlier formed concentric fabric. The nature of the structural domains shows that the emplacement of Cerro Bayo occurred in three stages that resemble the endogenous to exogenous growth of volcanic domes. The formation of magmatic shear zones during cryptodome formation may have a profound effect on cryptodome stability by creating weakness zones that increase the risk of collapse.</p