1,720,970 research outputs found
The origin of spheroidal halloysites: A review of the literature
Get PDFTubular halloysite has many applications as a nanomaterial. Spheroidal halloysite (SPH) is the other most common form of halloysite. Its mode of formation has had different explanations, including association with allophane, or more generally, following weathering of volcanic glass. Some SPHs have formed from minerals in crystalline rocks, sometimes as an early stage of evolution into plates and/or tubes of halloysite and ultimately to kaolinite. Spheroidal halloysites can show a range of Fe contents and can occur with other forms of halloysite; they have often formed in confined environments whereas tubular halloysites apparently form in more open spaces. They have also formed on microbes or where there is a significant amount of organic matter. Generally, SPHs have often formed by rapid dissolution of volcanic glass and primary minerals. The SPHs can persist over time. They have few active edges, so interparticle interaction is poor, causing low viscosities in clay-water suspensions, poor soil stability and low adsorption capacities.Fil: Cravero, Maria Fernanda. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Jock Churchman, G.. University of Adelaide; Australi
Hydrogeochemistry and Stable Isotopes of a Solid Waste Disposal Area from Gualeguaychú, Entre Ríos, Argentina
Get PDFMajor and trace elements, pH, electrical conductivity and organic matter were determined in groundwater and subsoil samples collected from an urban solid waste final disposal site (Gualeguaychú city, Argentina) in order to quantify leachate impact on the quality of these resources. Geochemical modeling results showed mixing process of pristine water and leachate in different proportions which promote, in turn, other processes in the free aquifer such as cation exchange, outgassing of carbon dioxide, precipitation and dissolution of minerals. Anomalous electrical conductivity values of subsoil samples confirmed the leachate impact too. Soilwater interaction allowed the development of natural attenuation processes in water: low dissolved organic carbon (DOC), iron and aluminum concentrations were associated with high amounts in subsoil. High clay content (smectites) and high cation exchange capacity, organic matter and metals analysis suggesting that the exchange and or sorption process were effective. δ13C-DOC constant values ratified the DOC sorption in sediments rather than oxidation. Other natural processes such evaporation and marine ingressions were detected through geochemical models. δ18O y δ2H values suggested not only a meteoric origin for the groundwater but also evaporation and mix process of waters. δ13C-DIC demonstrated that CO2 outgassing could have happened during the mixing.Fil: Sanci, Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Panarello, Hector Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Cravero, Maria Fernanda. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentin
‘Piedra Mar del Plata’: An Argentine orthoquartzite worthy of being considered as a ‘Global Heritage Stone Resource’
Get PDFAlthough 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.Fil: Cravero, Maria Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotopica; ArgentinaFil: Ponce, M. B.. Secretaría de Industria y Minería. Servicio Geologico Minero Argentino; ArgentinaFil: Gozalvez, M. R.. Secretaría de Industria y Minería. Servicio Geologico Minero Argentino; ArgentinaFil: Marfil, S. A.. Universidad Nacional del Sur. Departamento de Geología; Argentin
Zr-Ti-Fe placers along the coast of NE Argentina: Provenance analysis and ore guide for the metallogenesis in the South Atlantic Ocean
Get PDFThe Zr-Ti-Fe placers along the coast of Rio Negro and Buenos Aires Provinces, Argentina, evolved within the reaches of the Malvinas Current (1st order hydrodynamic regime). Together with some regional 2nd order local currents it is of major influence on the mineral assemblage of these terrigenous linear shoreline deposits. The nearshore-marine placers came into being in a macro- to mesotidal (San Matias Gulf) and meso- to microtidal regime (Bahia Blanca Estuary).The modern-day placers under study result from a transgressive regime with only moderate detrital input by the contemporaneous river drainage systems. The proto-placers are hallmarked among the heavy minerals (HM) by changes in the redox system which affected predominantly the Fe-Ti oxides and lead to pseudobrookites and kleberite. Light minerals (LM) in the present-day placers played a different role which is mirrored by changes in the alkalinity of the intragranular fluid system. As far as the environment of deposition is concerned in these shoreline deposits, the dune belt and backshore are most prospective as to the concentration of magnetic and non-magnetic HM. The HM assemblage of the coastal placers is a mirror image of the Afro-American part of Gondwana and its break-up history during the Mesozoic and Cenozoic. The HM reflect the alternating orogenic and anorogenic geodynamic processes operative along the passive margin of both continents. While the orogenic regimes contributed to the accumulation of metallogenetically irrelevant HM (e.g. alumosilicates, spinel, garnet, amphibole) of the placers, the anorogenic geodynamic regime may be held accountable for the target elements in the placer deposits Zr, Ti and Fe. Fe-Ti oxides (rutile, ilmenite-titanohematites, titanomagnetites) and zircon form placer deposits in their own rights with zircon playing an additional minor role also as ore guide to rift-related deposits. Titanium dioxides (Nb-Ta rutile s.s.s., struverite) and Nb titanite take the most prominent role as ore guides to rare element-bearing pegmatites, alkali magmatic rocks and carbonatites. In conclusion, the HM suite encountered in the placer deposits denotes a hot-spot mineralization at a triple junction of the South Atlantic, the Antarctic and the Proto-Iapetus Oceans. The Zr-Ti-Fe placer deposits are part of the clastic halo or expressed metaphorical as remnants of this hot-spot metallogenesis encompassing anorogenic Nb-Ta deposits related to alkaline-magmatic rocks, Skaergaard-type Fe-concentration and anorthosite-hosted Fe-Ti deposits.Fil: Dill, Harald G.. Gottfried Wilhelm Leibniz University; AlemaniaFil: Goldmann, Simon. Bundesanstalt für Geowissenschaften und Rohstoffe; AlemaniaFil: Cravero, Maria Fernanda. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentin
Mineralogical and geochemical analysis of sodium bentonites in continental settings: The Uspallata Group (Triassic) of the Cuyana Basin, Mendoza province, Argentina
No full textThe Triassic Uspallata Group of the Cuyana rift Basin is characterized by continental deposits including alluvial, fluvial and lacustrine systems, mainly composed of volcaniclastic (reworked) and pyroclastic sediments. The present work focuses on the ash fall tuffs levels (bentonites) in order to understand the origin of their sodium composition since classic worldwide natural sodium bentonites link with marine environments as a source of sodium. The mineralogical attributes and relationship with diagenetic alterations have been explored by petrography, X-ray diffraction, and geochemical analysis. The tuff levels, recorded in the Cerro de las Cabras, Potrerillos and Cacheuta formations, provide the most reliable representation of the composition of the original material and diagenetic alterations due to these levels are devoid of detrital input. Accordingly, they represent key elements to explore the origin of huge bentonite deposits in the basin. In the study units, Na-montmorillonite and analcime, found at concentrations of up to or more than 50 vol%, grew at the expense of vitric components and represent authigenic minerals developed under early diagenesis. Following sedimentological and paleogeographic evidence the alteration of volcanic glass occurred in hydrologically open lacustrine systems that reached saline-alkaline conditions. The changes in the (Na + K)/H+ ratio influenced the formation of Namontmorillonite and analcime through the succession. In addition, kaolinite is an important alteration mineral that fills cavities, replaces the feldspar grains, and probably the early diagenetic minerals. The origin of kaolinite is due to the combined effects of decomposition of organic matter and incursion of meteoric freshwater during late-stage telogenesis which generated the acidification of pore waters. Based on geochemical proxies, geochronological data and the geodynamic context the input of high volumes of pyroclastic material may thus be the result of explosive volcanism from an arc-subduction complex located to the west at these latitudes. The present work suggests that the composition of Na-rich pyroclastic ashes accumulated in hydrologically-open lake systems which conditioned the formation of sodium bentonites in continental settings.Fil: Salduondo, Joaquín. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Comerio, Marcos. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Cravero, Maria Fernanda. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Etcheverry, Ricardo Oscar. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin
Zeolites in acid vitreous rocks, southern Mendoza, Argentina
Get PDFA mordenite-rich deposit located in the south of the province of Mendoza (Argentina) was studied. The host rock in this area has not been previously described and corresponds to rhyolitic lavas of high-K calc-alkaline series. Petrographic, mineralogical and geochemical analyses of fresh and altered rocks are shown, and a proposal for the alteration process and the stratigraphic position of the protolith is presented. The main mordenite-rich sectors developed in zones of autobreccias of high permeability, with minor clinoptilolite, smectites, secondary K-feldspars, opal-CT, and colloform silica. The proportion of relict glass vs. alteration minerals is variable and mainly depends on the texture (permeability) of the host rock. The studied rhyolites overlie the Upper Cretaceous sediments of the Neuquén Group and are covered by Tertiary basalts of the Molle Eruptive Cycle and Quaternary sediments. Geochemically, they present similarities with rhyolitic rocks of Cordón del Burrero Volcanic Complex of Lower to Middle Miocene age.Fil: Locati, Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Cravero, Maria Fernanda. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Marfil, Silvina Andrea. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Centro de Geología Aplicada, Agua y Medio Ambiente; Argentina. Universidad Nacional del Sur. Departamento de Geología; ArgentinaFil: Lescano, Leticia. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Centro de Geología Aplicada, Agua y Medio Ambiente; Argentina. Universidad Nacional del Sur. Departamento de Geología; ArgentinaFil: Madsen, Lenís. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Centro de Geología Aplicada, Agua y Medio Ambiente; Argentina. Universidad Nacional del Sur. Departamento de Geología; ArgentinaFil: Maiza, Pedro Jose. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Centro de Geología Aplicada, Agua y Medio Ambiente; Argentina. Universidad Nacional del Sur. Departamento de Geología; Argentin
Palaeoclimatic and diagenetic controls based on clay mineralogy and organic matter distribution: The continental rift Cuyo Basin (Triassic), west-central Argentina
No full textThe Triassic Cuyo rift Basin is one of the renowned petroleum systems in South America that records distinctive alluvial, lacustrine and fluvial settings with volcanic input. The present study focuses on the clay mineral assemblages that represent the syn-rift to post-rift fills. Four clay mineral assemblages are defined based on X-ray diffraction, optical and electron microscopy analyses. The illite/mica-dominated assemblage is documented in the syn-rift I (Cerro de las Cabras Formation). Such mineral phases are inherited and derived from the erosion of pre-rift units, suggesting that physical weathering associated with a warm and semi-arid climate played a leadingrole in their occurrence. Authigenic smectite clays are diagnostic in organic-lean mudstones of the syn-rift II (lower Potrerillos Formation) which point to alteration of pyroclastic material under a warm and semi-arid to humid climate. A warm and humid climate prevailed during the depositionof lacustrine hydrocarbon source rocks (upper Potrerillos and Cacheuta formations). Organic-rich mudstones show the illite/mica–kaolinite–smectite assemblage in conjunction with amorphous organic matter and restricted terrigenous elements. Diagenetic kaolinite booklets and bipyramidal quartz are attributed to the acidification of pore-water related to kerogen transformationduring burial diagenesis. Vitrinite reflectance values (ca 0.63%) confirm that organic-rich sediments reached the earliest oil window; however, smectite is devoid of illite layers throughout the Triassic succession, probably related to the absence of potassium in the system and the high crystallinity of the smectite, which delayed the transformation of smectite into mixed layers illite–smectite. Red mudstones of the post-rift II (the fluvial-lacustrine Rio Blanco Formation) show the kaolinite-dominated assemblage where theauthigenic kaolinite is interpreted to be derived from the alteration of volcaniclasticdetritus and indicative of warm climate with markedly wet periods.Fil: Salduondo, Joaquín. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Comerio, Marcos. YPF - Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pineda, Juan A.. YPF - Tecnología; ArgentinaFil: Cravero, Maria Fernanda. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Erra, Georgina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Spheroidal halloysites from Patagonia, Argentina: Some aspects of their formation and applications
Get PDFHalloysite deposits in Argentina have been identified in the province of Río Negro (Patagonia). The mineralized area occurs as altered zones in Eocene volcanic–pyroclastic rocks, dacitic to rhyolitic in composition. A comprehensive study of these deposits was carried out by means of mineralogical, geochemical and isotopic analyses. Intense weathering has transformed the whole rock to a white mass composed of 75% –90% halloysite + kaolinite, with cristobalite, tridymite, and quartz, as the main non-clay minerals. Ferruginous beidellite and titanium minerals are also present in minor amounts. The halloysite–kaolinite ratio ranges from 75 to 25 to 100–0. Due to the alteration of very dense rocks, halloysite morphology is predominantly spheroidal. Tubular halloysite is the main constituent in more porous rocks, but the latter are scarce in the area. Because of the predominance of the spheroidal type, the use of halloysite as HNT (halloysite nanotube) is not feasible. Nonetheless, this mineral can be modified by different organic molecules, and used to remove pollutants such as emulsified hydrocarbons and heavy metals. A special product made with this halloysite is used as sunscreen when sprayed on fruits in areas of intense solar radiation. The whiteness of this mineral is not very high due to the amount of titanium oxide present in its composition (about 1%). Nevertheless, titanium oxide is present as individual particles, so it could be removed by a mechanical process. New applications for spheroidal halloysite are currently being investigated. Moreover, depending on the price and demand, the tubular halloysite of low grade deposits could be exploited.Fil: Cravero, Maria Fernanda. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Fernández, L.. Universidad Nacional del Comahue; ArgentinaFil: Marfil, S.. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Sánchez, M.. Universidad Nacional del Comahue; Argentina. Universidad Nacional del Sur; ArgentinaFil: Maiza, Pedro Jose. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Sur; ArgentinaFil: Martínez, A.. Universidad Nacional del Sur; Argentina. Biotec Argentina S.R.L; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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