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Variations in Melt Productivity and Melting Conditions along SWIR (70°E–49°E): Evidence from Olivine-hosted and Plagioclase-hosted Melt Inclusions
No full textMelt inclusion and host glass compositions from the eastern end of the Southwest Indian Ridge show a progressive depletion in light rare earth elements (LREE), Na8 and (La/Sm)n, but an increase in Fe8, from the NE (64°E) towards the SW (49°E). These changes indicate an increase in the degree of mantle melting towards the SW and correlate with a shallowing of the ridge axial depth and increase in crustal thickness. In addition, LREE enrichment in both melt inclusions and host glasses from the NE end of the ridge are compatible with re-fertilization of a depleted mantle source. The large compositional variations (e.g. P2O5 and K2O) of the melt inclusions from the NE end of the ridge (64°E), coupled with low Fe8 values, suggest that melts from the NE correspond to a variety of different batches of melts generated at shallow levels in the mantle melting column. In contrast, the progressively more depleted compositions and higher Fe8 values of the olivine- and plagioclase-hosted melt inclusions at the SW end of the studied region (49°E), suggest that these melt inclusions represent batches of melt generated by higher degrees of melting at greater mean depths in the mantle melting column. Systematic differences in Fe8 values between the plagioclase- and the olivine-hosted melt inclusions in the SW end (49°E) of the studied ridge area, suggest that the plagioclase-hosted melt inclusions represent final batches of melt generated at the top of the mantle melting column, whereas the olivine-hosted melt inclusions correspond to melts generated from less depleted, more fertile mantle at greater depths
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No full textAbstract not available
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
U-Pb columbite-tantalite chronology of rare-element pegmatites using TIMS and Laser Ablation-Multi Collector-ICP-MS
No full textU-Pb isotopic analyses using TIMS and Laser Ablation-Multi Collector-ICP-MS were carried out on columbite-tantalite minerals from three suites of rare-element (Li, Cs, Ta) pegmatites in the Superior Province of Canada. Conventional TIMS analyses of these columbite-tantalite crystals produce scattered data and reverse discordance even after HF leaching of the grains prior to dissolution, possibly reflecting the incomplete removal of the open-system metamict segments during sample preparation. LA-MC-ICP-MS analyses of unleached, primary columbite free from inclusions and alteration give consistent and precise (<0.5%) Pb-Pb ages, demonstrating the utility of this approach. However, normal and reverse discordance is also observed in U-Pb data from LA-MC-ICP-MS analyses. This discordance represents either U-Pb mobilisation during recent weathering, sample preparation and/or an analytical artefact originating from variable elemental fractionation between U and Pb during ablation and ionisation that itself may have its origin in the contrasting metamictization of the dated columbite and the monazite standard used. Best age estimates of columbite from pegmatites in the Superior Province are; 2670±5 Ma for the Pakeagama Lake pegmatite, 2644±7 Ma for the Separation Rapids group, and 2665±8 Ma for the Mavis Lake group. The ages broadly show that the rare-element pegmatites are temporally synchronous with adjacent peraluminous granites
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
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
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No full textDispelling 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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