1,721,022 research outputs found
Ni-Co enrichment and High-Tech metals geochemistry in the Wingellina Ni-Co oxide-type laterite deposit (Western Australia)
No full textThe aim of this study is to evaluate the Ni-Co enrichment and the high-tech metals (REE and Sc) geochemistry in the Wingellina Ni-Co oxide-type laterite deposit (Western Australia). The study has been carried out on two mineralized cores (WPDD0012 and WPDD0019 drillcores) originating from two areas of the deposit. The geochemical assessments have been integrated with the analysis of laterite facies and sample mineralogy. In both the studied laterite profiles Ni enrichment was mostly controlled by the paragenetic evolution of the laterite itself, whereas Co enrichment was related to the formation of Mn-oxy-hydroxide-rich horizons in the limonitic ore-body. Significant REEs concentrations (up to 890 ppm) have been observed within the limonite zones. The correlation between REEs and the major oxides shows a decoupling between Ce and the other REEs, likely reflecting either a variable enrichment process among the different REEs, or a heterogeneous mineralogy of the REEs-bearing phases. Differently from other Ni-Co laterite deposits, Sc is only in limited part correlated with Fe2O3, having been most commonly detected in Ni- and SiO2-rich zones of the saprolitic parts of the profiles. All the geochemical features, the facies characteristics and the Ni-Co, REEs and Sc grades observed in the two studied profiles seems to be the results of the interactions between two main controlling factors: distinct parent rock lithology and diverse degree of serpentinization
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
The Shanggong gold deposit, Eastern Qinling Orogen, China: Isotope geochemistry and implications for ore genesis
No full textVariations 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
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
Mineralogical association and Ni-Co deportment in the Wingellina oxide-type laterite deposit (Western Australia)
No full textThe Wingellina deposit (currently owned by Metals X Limited) is an oxide-type Ni-Co laterite, with 168 Mt of ore grading 0.98% Ni and 0.08% Co. The laterite profile is derived from the weathering of the olivine-rich mafic-ultramafic layered intrusion of the Giles Complex (Mesoproterozoic) and consists of a well-developed limonitic ore and a thin saprolite horizon. XRPD, SEM-EDS and EMPA analyses revealed that the ore zone is dominated by Fe- and Mn-(hydr)oxides, which are the main carriers of both Ni and Co. The mineralogy of the Mn-hydroxides is complex, and high concentrations of Co and Ni occur mainly in a lithiophorite-asbolane intermediate phase, which has been subdivided into types I, II, III and IV, with significant differences in their Co/Ni ratios and Al content. The enrichment of metals in the lithiophorite-asbolane phases is mainly controlled by the Co and Ni replacement of Al in gibbsite-like layers, and rarely by Ni incorporation in the vacancies of Mn-(hydr)oxides. Other, less important, metal-bearing Mn-(hydr)oxides at Wingellina include romanèchite, ernienickelite-jianshuiite, manganite, and birnessite. The texture and chemistry of the Mn-(hydr)oxides suggest that the lithiophorite-asbolane phases were formed at a later stage with respect to the other manganiferous phases, after repeated leaching and re-precipitation of the Mn-(hydr)oxides. This process could be one of the main factors controlling the enrichment of Co and Ni in the limonite zones during lateritization
Ore geology, fluid geochemistry and genesis of the Shanggong gold deposit, Eastern Qinling Orogen, China
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