1,721,002 research outputs found
Tectonic setting and geochronology of the Cadomian (Ediacaran-Cambrian) magmatism in Central Iran, Kuh-e-Sarhangi region (NW Lut Block)
Full text linkThe structure, age and petrogenesis of plutonic basement rocks from the Kuh-e-Sarhangi region, located in the Kashmar-Kerman tectonic zone of Central Iran are described. These intrusive rocks consist of a sub-alkaline, dominantly high-K calc-alkaline acidic suite, characterised by high SiO2 (72.60-77.17wt%), and alkalis (up to 8wt%) and low Mg# (07-35). They are also enriched in Th, U and light rare earth elements, and depleted in Nb, Ta, and Ti, thus showing a geochemical fingerprint compatible with arc magmatism. The U-Pb zircon geochronology constrains magma crystallisation and emplacement during Ediacaran-Cambrian (ca. 575-535Ma) times, under a tectonic regime dominated by transpressional tectonics as constrained by analysis of field structures. Combined inverse and forward modelling thermobarometry indicates pluton emplacement occurred in a thickened crustal environment, suggesting the Kuh-e-Sarhangi magmatic belt exposes the exhumed roots of a volcanic arc. This magmatism is interpreted as part of the Cadomian, subduction-related magmatism and framed within an oblique convergence scenario during formation of an Andean-type active margin all along the northern (proto-Tethyan) margin of the Gondwana Supercontinent
Hydrothermal karst and associated breccias in Neoproterozoic limestone from the Barker-Villa Cacique area (Tandilia belt), Argentina
Full text linkIn the Barker-Villa Cacique area (Tandilia belt), remarkable megabreccias, limestone breccias and phosphate-bearing breccias hosted in black limestone and along the contact with the upper section of the sedimentary succession are exposed. These rocks are the result of extensive hydrothermal alteration of the original micritic limestone and other fine-grained clastic sediments. Typical alteration minerals are sericite, chlorite, interstratified chlorite/K-white mica, kaolinite, dickite, pyrite, chalcopyrite, goethite, quartz, calcite, Fe-calcite, dolomite, ankerite, fluor-apatite, barite and aluminium-phosphate-sulfate (APS) minerals. Quartz and calcite cements from hydraulic breccias in the limestone contain low-salinity aqueous fluid inclusions. Corresponding homogenization temperatures display 200-220 °C and 110–140 °C in hydrothermal quartz, and 130-150 °C in late calcite cement. Carbon and oxygen stable isotope analyses of carbonates from the Loma Negra quarry (LNQ) support the major role of hydrothermal activity. A significant difference was found between δ18Ocar values from unaltered micritic limestone (ca. 23.8‰ SMOW) and secondary calcite (ca. 18.5‰ SMOW). The lower δ18Ocar values are interpreted as a result of calcite precipitation from hot hydrothermal fluids. At a late stage, the hydrothermal fluid containing H2S mixed with descending and oxidizing meteoric waters. Circulation of the ensuing acid fluids resulted in the partly dissolution and collapse brecciation of the Loma Negra Formation. The hydrothermal stage can be tentatively dated ca. 590–620 Ma corresponding to the Brasiliano orogeny.Fil: Dristas, Jorge Anastasio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; ArgentinaFil: Martinez, Juan Cruz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; ArgentinaFil: van den Kerkhof, Alfons M.. Universität Göttingen; AlemaniaFil: Massonne, Hans Joachim. Universität Stuttgart; AlemaniaFil: Theye, Thomas. Institut für Mineralogie und Kristallchemie. Universität Stuttgart; AlemaniaFil: Frisicale, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; ArgentinaFil: Gregori, Daniel Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Alunites and REE rich APS minerals associated to hydrothermal clay deposits in the Barker area, Tandilia, Argentina
Full text linkChemical bulk analyses of intermediate alunite-natroalunite minerals indicate anomalous high contentsof REE, Sr, Ba, Ca and P. Alunite occurs as veinlets or nodules cross-cutting hydrothermal claydeposits, containing pyrophyllite, kaolinite and sericite in the west Barker area (Dristas & Frisicale1983(5), 1992(6)). Petrographic studies reveal a pseudocubic habit for the alunite. No significant zoninghas been detected in this mineral by EPMA backscattered images. Additionally, EPMA and EDXstudies indicate that the tabular-like inclusions in cores of alunite contain significant amounts of P, Ba,Sr, REE, Ca and Fe. Alunite shows epitaxial growth on the inclusion mineral. These tabular-likeinclusions correspond to APS (aluminium phosphate sulphate) minerals, such as florencite, formed atearly stages before alunite crystallization from a solution with a high phosphorous/sulphur ratio. Thecrystal structure of APS minerals are suitable for REE, Sr and Ba substitution since metal cations aresituated in large cavities formed by 6-membered rings of M(O, OH)6 octahedra. A later increase ofsolution sulfurization would favor the formation of alunite that constrained the REE, P, Sr, Fe, Ca andBa fixation.Fil: Martinez, Juan Cruz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Geología; ArgentinaFil: Dristas, Jorge Anastasio. Universidad Nacional del Sur. Departamento de Geología; ArgentinaFil: Massonne, Hans J.. Universitat Stuttgart; AlemaniaFil: Theye, Thomas. Universitat Stuttgart; Alemani
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Alpine tectono‐metamorphic evolution of the Corsica basement
Full text linkThe Alpine orogenic edifice of Corsica (northern Tyrrhenian Sea) offers thepossibility to investigate the mode through which continental crust respondsto the propagation of regional shortening at convergent plate margins. Thegeology of Corsica has been traditionally described as separating domainsaffected by the Alpine tectonism (Alpine Corsica) from those that did not expe-rience the Alpine tectono-metamorphic overprint (Hercynian Corsica), butrecent studies show that most of Hercynian Corsica was thermally reset inpost-Eocene times, questioning this paradigm. The continental units formed atthe expenses of the stretched continental margin of the European plate andconsist of Hercynian granitoid basement rocks and cover sequences (Permianvolcaniclastics and Mesozoic sedimentary successions). By integrating meso-and microstructural investigations with metamorphic thermobarometry and40Ar–39Ar geochronology along three E–W trending structural transectsrunning across the basement section exposed below the Alpine orogenicwedge, we document middle-late Eocene (c. 50–33 Ma) westward-vergingsyn-metamorphic (low-grade blueschist facies) thick-skinned, basement-involved thrusting. Significantly, crustal shortening in the continentalbasement predated of c. 15–10 Ma the subduction zone metamorphism in theoceanic-derived Schistes Lustrés Complex. When the P–T–t–deformationhistory as reconstructed from the Corsica basement is integrated with theregional scenario of the Alpine–Apennine orogeny, a tectonic reconstruction isproposed, which frames the Alpine orogeny in Corsica within the Apennine–Maghrebian subduction system in the retroside (retrowedge) of the Apennineorogenic wedge
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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