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40Ar/39Ar dating of the trachytic crystal mush of the Green Tuff ignimbrite, Pantelleria island
No full textThe Green Tuff (GT) is the last of nine ignimbrite eruptions associated with the peralkaline volcanic complex of Pantelleria island (Sicily Channel, Italy).
Well known in the scientific literature for its petrological and eruptive peculiarities, the GT eruption withdrew a shallow chemically zoned magma reservoir, consisting of a deeper and a late-erupted trachytic crystal mush (P = 1-1.5 kbar, T = 925 C°, H2Omelt = 1.5-2.5 wt.%) to a shallower pantelleritic magma batch (P = 0.5-1-2 kbar, T = 730 °C; H2Omelt = 4.0-4.5 wt.%) (Romano et al., 2018, 2019).
In this work we focus on the trachytic top member, which is characterized by high porphyricity (> 35 vol.% Na, K-feldspars phenocryst), high Ba concentrations and positive Eu anomalies both in the groundmass glass and in cpx-hosted H2O-poor melt inclusions as well (Romano et al., 2018, 2019).
To better constrain the Green Tuff eruption and to stress the relationship between trachytic and pantelleritic members, we performed new 40Ar/39Ar age determinations on anorthoclases phenocrysts (mean composition: Ab70Or25An5; Romano et al., 2018).
Irradiation with fast neutrons along the flux monitor FCT (Fish Canyon Tuff) at the Oregon State TRIGA Reactor was followed by a long degassing at low temperature, a necessary step to discard any extraneous surface-bound 40Ar. Single crystal laser ablation was followed by the isotopic ratios measurements of argon using a Helix SFT (2013) mass spectrometer housed at Institut des Sciences de la Terre d’Orléans (CNRS-ISTO). Despite accurate hand-picking selection, xenocrysts cannot be avoided, but their effect can be mitigated using the single grain fusion approach to provide a robust eruption age.
Pantelleritic members (basal fallout deposit and ignimbritic member) were previously dated at 45.7 ± 1.0 ka (2σ; Scaillet et al., 2013). Here, we obtained a statistically indistinguishable weighted mean age of 43.9 ± 0.5 ka (1σ), with a Mean Square Weighted Deviation (MSWD) of 1.34. This age confirms previous dating and point to variable (lesser) xenocrysts contaminations relative to the other GT members. This is unexpected on the premise that more 40Ar should be stored in crystals accumulating at the bottom of the pantellerite magma chamber due to feldspar fractionation and accumulation in the magma mush.
Compared to the age of the pantelleritic members, our new data basically supports field evidence, confirming no stasis took place between the plinian/sub-plinian phase of the eruption (basal fallout deposit and ignimbrite) and the late extrusion of the trachytic ignimbrite top member representing the deeper portion of the Green Tuff reservoir
Natural Laboratories for Field Observation About Genesis and Landscape Effects of Palaeo-Earthquakes: a Proposal for the Rocca Busambra and Monte Barracù Geosites (West Sicily)
Full text linkEarthquakes are phenomena that are still being learned by the scientific community, and poorly known, especially as regards the prevention, by the population. Having a more complete knowledge is a basic step in understanding the vastness and intensity of the destructive phenomenon that involves a great amount of people. The recent earthquakes occurred in Central Italy (L’Aquila and Amatrice earthquakes) are examples that demonstrate the importance of having knowledge about these phenomena to contrast their destructive effects. We present a geological field trip to recognise causes and landscape effects of palaeo-earthquakes recorded in the Mesozoic rock successions outcropping in Sicily. The isolated carbonate reliefs of Rocca Busambra and Monte Barracù (Sicani Mountains) are spectacular sites of a passive continental margin where synsedimentary tectonic features—as palaeo-faults, neptunian dykes, morphostructural scarps, submarine landslide and soft sedimentary deformation structures—document earthquake causes and effects. Field evidence show in detail as the several palaeo-faults mapped in the Rocca Busambra stepped margin triggered the soft-sediment deformation structures recorded in the coeval deep-water rock succession of the Monte Barracù. In this view, the proposed field trip can represent a powerful tool to enhance the naturalistic and geological importance of the study areas by establishing geosites and protected areas for a proper fruition of geological-natural heritage and/or for geoconservation. Thus, through the proposed field trip it is possible to observe palaeo-earthquakes activity and landscape products, having an educational training purpose also for public administrators, whose rapid and skilled action is necessary for the prevention and reduction of the geohazard
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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