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• Artículo
  Relationships Between SiO₂, Al₂O₃, Fe₂O₃, CaO, K₂O, and Expansion in the Determination of the Alkali Reactivity of Basaltic Rocks

  ( 1998) Marfil, Silvina Andrea ; Maiza, Pedro ; Bengochea, A. L. ; Sota, Jorge D. ; Batic, Oscar R.

  The purpose of this work is to attempt to establish the relationship between the chemical elements leached out of basaltic rocks and the expansion measured on mortar bars by the ASTM C9 P214 method. Seventeen basalt samples from different locations in Argentina were selected. Solubilized SiO₂ was determined by the chemical test method (ASTM C-289). An aliquot of the solution was analyzed by ICP, indicating the presence of AI₂O₃, Fe₂O₃, CaO, K₂O, MgO, TiO₂, and MnO. The results obtained were statistically treated by the Principal Components method in order to determine whether there is a relationship between each of the analyzed elements and the expansion and, if any, their degree of participation. It was concluded that expansion is closely related to the dissolved silica contributed by the deleterious mineralogical components of basaltic rocks, especially volcanic glass and its alteration products, and poorly crystallized silica. The iron and calcium content does not have any influence on the reactivity. High values of solubilized silica would indicate that the basaltic rock has undergone an intense devitrification and/or silicification.
• Artículo
  Piedra Mar del Plata : An Argentine orthoquartzite worthy of being considered as a Global Heritage Stone Resource

  ( 2014) Cravero, F. ; Ponce, María Beatriz ; Gozalvez, M. R. ; Marfil, Silvina Andrea

  Although Argentina is a large country, only a few local stones meet the requirements to be used for construction purposes. Piedra Mar del Plata is a quartzite that has been used for more than 50 years, mainly as a building stone. During the 1930s and 1950s, its use in the construction of houses in the city of Mar del Plata (a famous beach resort) created a distinctive architectural style. Because of its durability and availability, the use of this stone rapidly spread to other parts of the country. Sculptures and monuments have also been made out of this stone. Mar del Plata architectural style is now part of the heritage of Argentina and represents the rise of the middle class, when local citizens could afford to build their own houses in a style different from the mansions, which were constructed by rich families with imported stone.
• Documento de conferencia
  Geoquímica de la zona caolinizada de Mina Estrella Gaucha (Prov. de Chubut, Argentina)

  ( 2008) Maiza, Pedro ; Marfil, Silvina Andrea ; Cardellach, Esteve ; Zunino, Juan

  En las provincias de Chubut y Santa Cruz existen numerosos yacimientos de caolín, algunos de gran extensión areal como los del valle del río Chubut, lotes 8, 18, 19 y Cerro Rubio, estudiados por Cravero et al. (2001). Dichos depósitos son de origen residual y sedimentario, formados a partir de la alteración de materiales volcánicos (especialmente tobas) de composición riolítica de edad Jurásico medio-superior. En esta misma provincia existe otro grupo de depósitos de caolín cuya génesis se relaciona con fenómenos de alteración hidrotermal. Un ejemplo de ellos es Mina Estrella Gaucha . Este depósito fue estudiado por Hayase et al. (1971), Maiza (1972, 1981) y Maiza y Hayase (1975), quienes determinaron la existencia de cuatro zonas de alteración: zona silicificada, zona alunitizada, zona caolinizada y zona de sericita-clorita, concluyeron que el origen del yacimiento es epigenético-hidrotermal y propusieron un modelo de zonación. Se encuentra ubicado a 70 Km de la localidad de Alto Río Senguer (Prov. de Chubut), emplazado en areniscas tobáceas y conglomerádicas de la formación Apeleg de edad Cretácico inferior. Con el fin de determinar el origen del depósito, en el presente trabajo se ha llevado a cabo un estudio mineralógico, geoquímico, de elementos mayores, menores y traza y de los isótopos estables de O y D de la zona caolinizada.
• Documento de conferencia
  Geochemistry of the hydrothermal kaolins in the SE area of Los Menucos. Prov. de Río Negro

  ( 2001) Maiza, Pedro ; Pieroni, D. ; Marfil, Silvina Andrea

  Rhyolitic tuffs of the Sierra Colorada Fm (Triassic - Middle Jurassic) accommodate remarkable argillaceous mineralization with a zonalion characterized by strong silicifícation ai the upper levels, kaolinite, dickile and alunite at the intermedíate levels, and sericitization at the bottom, where relicts of the original texture oí the rock can be recognized. The alteration process has wholly obliterated the original texture. Relicts of embayed quartz, phanloms of mafic minerals, defined by the precipitation of i ron oxides, and feldspar pseudomorphically replaced by almost puré kaolinite and dickile with cryslals that can be up to 70 μm in size, can be recognized. Ore samples taken from a quarry about 15 metcrs in width were analyzed by XRD, TG- DTA, IR, SEM,EDAX and ICP. These methods allowed the identification of dickite, kaolinite and alunite occurrence. Rare eailh elements (REE) were analyzed showing a marked Eu negative anomaly, but no Ce anomaly, which would be typical of sedimentary deposits. There is a cióse spatial relationship between kaolinite and dickite crystallization, which is concentrated at the intermedíate levels. Alunite distribution is being concentrated at the most permeable sections. The presence of dickite and alunite, the textures and valúes of REE support a hydrothermal origin. Ore-bearing fluids reached a quite acid pH, detennined by the presence of alunite and temperaturas of about 250°C, which allowed dickite crystallization.
• Artículo
  Deteriorated pavements due to the alkali-silica reaction: a petrographic study of three cases in Argentina

  ( 2001) Marfil, Silvina Andrea ; Maiza, Pedro

  Deteriorated concrete pavements from three regions in Argentina were studied. The aim was to evaluate aggregate constituents, especially the presence of deleterious components, determine what reaction products had developed, and find the main causes of the deterioration based on the petrographic study of the concrete. Thin sections were analyzed with a petrographic microscope to evaluate microcracking, characteristics of the aggregate-cement interface, reaction rims, and the development of reaction products. The latter were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDAX). Pavements exhibit widespread microcracking with the development of crystalline materials at the aggregate rims, identified as zeolite-like structures by XRD. From the ED AX analysis, Si, Al, O, Ca, K, and Na were determined. Ettringite is abundant both inside cavities and on crack surfaces within concrete. Its occurrence was confirmed by XRD and ED AX. The aggregate deleterious constituents are mainly glassy vulcanites and volcanic glass, generally altered to argillaceous minerals, and strained quartz, with undulatory extinction. The deterioration of the three pavements studied was due to the development of the alkali-silica reaction (ASR), involving the strained quartz.