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High-Ti and Low-Ti Ophiolitic Belts in Albania: A petrogenetic model for crustal accretion in Mid-Ocean Ridge and Suprasubduction oceanic settings
No full textMid-Ocean Ridge and Suprasubduction affinities in the Ophilitic Belts from Albania
No full textPetrological data based on 147 new major and trace element analyses are presented as a preliminary result of the research program on Jurassic ophiolites from Albania. Albanide ophiolites of the Mirdita tectonic zone represent one of the most complete, coherent sequences among all the Mediterranean ophiolites, and are constituted by two NNW-SSE trending subparallel belts.
The Eastern Belt is mainly represented by mantle tectonites, predominantly harzburgitic in composition (clinopyroxene: 3-0 %; Kukes, Bulqize, and Shebenik Massifs, from north to south). Westward, tectonites gradually give way to a cumulitic intrusive sequence - particularly well-developed in the northern part - consisting of dunites, (plagioclase-) lherzolites, (olivine-) websterites, (mela-) gabbronorites (with minor troctolites), quartz-diorites and plagiogranites. Accordingly, their crystallization order is olivine + chromite, followed by pyroxenes and then plagioclase. Chromititic layers, pods and lenses - always associated with dunites - occur both within mantle harzburgites and in the ultramafic lower portion of the cumulitic sequence. The associated volcanic suite consists of low-Ti and, more rarely, very low-Ti basalts and basaltic andesites, andesites, dacites, and rhyolites. Sheeted dike complexes occur mainly in the lower part of the volcanic formation.
The Western Belt mainly consists of mantle tectonites, lherzolitic in composition (clinopyroxene: 13-5 %), passing upward to cumulitic (plagioclase-) dunites, (plagioclase-) wehrlites, troctolites, (mela-) gabbros, Fe-gabbros, and very scarce plagiogranites. The crystallization order is therefore olivine + chromite, followed by plagioclase and then clinopyroxene. The associated volcanics consist of high-Ti basalts with MORB affinity.
Strongly-tectonized metabasites, showing MORB affinity and metamorphosed into greenschist and amphibolite facies, are locally wedged within the ophiolitic units, as well as at their eastern and western borders.
In conclusion, the Western Ophiolitic Belt reveals pure MORB affinity, as indicated by the crystallization order and nature of cumulate intrusives, the less depleted composition of mantle tectonites, as well as the geochemical features of associated high-Ti basalts. Its original setting is therefore to be considered an oceanic spreading system, without any influence of subduction-related processes.
By contrast, for the Eastern Ophiolitic Belt, the petrological characteristics of the cumulitic sequence and the underlying strongly depleted mantle tectonites, together with geochemical features of the lavas, coherently indicate a suprasubduction generation of parental magmas. The generation of such a magmatic system implies intra-oceanic subduction of a pristine lithosphere, whose remnants could be represented by the Western belt ophiolites as well as by the associated metabasites with MORB affinity.
A paleogeographic reconstruction of the Mirdita oceanic basin during the Jurassic should therefore imply a previous creation of MORB-type oceanic lithosphere between the newly formed continental margins after the Triassic rifting phase; later on, an intraoceanic converging plate system would have developed on the eastern side of this basin, with the generation of a suprasubduction oceanic crust and underlying harzburgitic refractory mantle residua. The relatively undepleted lherzolite tectonites of the Gomsiqe, Krrab and Tropoja massifs, parallel to the Shkoder-Pec line, could represent, at least in part, subcontinental upper mantle material protruded and exposed along the bordering transcurrent system of the oceanic basin to the north
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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