Examinando por Autor "Grecco, L.E."
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Acceso Abierto Análisis estadístico de los resultados geoquímicos de los granitos de Cerros Colorados y Aguas Blancas, Sierras Australes de Buenos Aires(1992) Grecco, L.E.; Marfil, Silvina Andrea; Maiza, PedroSe realizó un estudio estadístico multivariado por los métodos de Componentes Principales y Análisis Discriminante con los resultados de los análisis químicos de los granitos peraluminosos de Cerros Colorados y Aguas Blancas. Con Componentes Principales, se determinó, que ambos intrusivos son similares, si bien se encontraron algunas diferencias en las variables involucradas. El análisis Discriminante permitió diferenciar los granitos estudiados sólo en base al contenido de $latex SiO_{2}, K_{2}O\hspace {0.1cm} y\hspace{0.1cm} Fe_{2}O_{3}.\hspace{0.1cm}$Los resultados obtenidos coinciden con la génesis deteminada a partir de los datos geoquímicos y petrológicos. - Artículo
Acceso Abierto Mineralogy and geochemistry of hydrothermal kaolins from the Adelita mine, Patagonia (Argentina); relation to other mineralization in the area(2012) Grecco, L.E.; Marfil, Silvina Andrea; Maiza, PedroThe kaolin deposit at the Adelita mine, located in the province of Rı´o Negro (Patagonia, Argentina), was studied. Petrographic studies on thin sections and chemical analyses of major, minor and trace elements on bulk samples were carried out. The kaolin content of the rock ranges from 31% to 65%. The mineralogy of the working front, which is about 45 m thick, varies from the upper zone, where the rock is strongly silicified, stained with iron oxides and carbonated, grading downwards to a kaolinized zone, with a quartz-kaolinite-dickite assemblage with relict lithic particles and a smaller amount of iron oxides, and ending in the deepest zone where dickite, alunite, diaspore, quartz and scarce associated kaolinite occur. The kaolin mineralogy was determined by SEM, XRD, DTA-TG, IR and d18O and dD isotope analyses. The S, Ba and Sr contents are enriched during hydrothermal alteration, whereas Cr, Nb, Ti and lanthanide elements are concentrated mainly during weathering. The (Ba+Sr) concentrations in the samples studied vary between 600 and 6000 ppm and (Ce+Y+La) between 2 and 150 ppm; (Cr+Nb) remains constant for all the samples, whereas (TiO2+Fe2O3) is below 0.3%. In the hypogene deposits P2O5 is also more abundant and increases with the degree of alteration. Chondritenormalized rare earth element diagram shows a marked enrichment in LREE relative to HREE, with negative europium anomalies and d18O values range between 3.8% and 7.7% and dD between 123% and 103%, suggesting that kaolin formed from the hydrothermal alteration of rhyolitic tuffs.