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Shoshonite and sub-alkaline magmas from an ultrapotassic volcano: Sr-Nd-Pb isotope data on the Roccamonfina volcanic rocks, Roman Magmatic Province, Southern Italy
No full textThe Roccamonfina Volcano is characterised by a two stage volcanic activity, divided by volcano-
tectonic collapses. Ultrapotassic leucite-bearing rocks are confined in the pre-caldera stage and display
geochemical characteristics very similar to those of other volcanoes of the Roman Province. Shoshonitic
rocks have been poured out from cinder cones and domes both within the caldera and on the external flanks
of the pre-caldera Roccamonfina volcano. On the basis of new trace element and Sr-Nd-Pb isotope data,
Roccamonfina shoshonitic rocks show differences with respect to shoshonites from Northern Roman
Province, and recall closely those of the Neapolitan volcanoes. Eventually, in the very last phases of
volcanic activity, sub-alkaline magmas are found both as enclaves in trachytic domes, and as final lavas
vented by a fracture within the Monte Santa Croce dome. Ultrapotassic rocks that built up the pre-caldera
composite volcano are plagioclase-bearing leucitites and, similarly to other Roman Provinces volcanoes, have by high levels of incompatible trace elements with an orogenic signature having troughs at Ba, Ta, Nb,
Ta, and Ti, and peaks at Cs, K, Th, U, and Pb. Initial values of 87Sr/86Sr range from 0.709261 to 0.709987,
of 143Nd/144Nd range from 0.512134 to 512195, of 206Pb/204Pb range from 18.788 to 18.851, of
207Pb/204Pb range from 15.685 to 15.701, and of 208Pb/204Pb range from 39.048 to 39.076. Shoshonites
show a larger differentiation degree but, as a whole, lower levels of incompatible trace elements with similar
pattern of incompatible trace element contents with respect to earlier ultrapotassic leucite-bearing rocks. On
the other hand, shoshonitic rocks have Sr, Nd, and Pb isotopes consistently different than pre-caldera
ultrapotassic leucite-bearing rocks. 87Sr/86Sr ranges from 0.706604 to 0.708332, 143Nd/144Nd ranges
from 0.512179 to 0.512382, 206Pb/204Pb ranges from 18.838 to 19.153, 207Pb/204Pb ranges from 15.661
to 15.694, and 208Pb/204Pb ranges from 38.999 to 39.212. High-K calc-alkaline samples have intermediate
isotopic values between ultrapotassic plagioclase leucitites and shoshonites, but the lowest levels of
incompatible trace element contents. The genesis of this uncommon association is investigated in details. It
is argued that ultrapotassic magmas have been generated in a modified lithospheric mantle after crustal-
derived metasomatism. Interaction between metasomatic agent and lithospheric upper mantle produced a
low-melting metasomatised veined network. Pure partial melting of vein mineralogy produced pre-caldera
leucite-bearing ultrapotassic magmas. Leucite-free magmas have been generated further melting, at higher
temperature, of the same meltasomatic mantle previously depleted by the ectraction of ultrapotassic rocks.
We suggest that a key role in this second episode of melting is played by little but significant addition of
astenospheric upper mantle material from foreland mantle, flowing through the corner of the Ionian present
day subducted slab during its roll-bac
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
Dunites in the Balmuccia Peridotite Massif (Western Italian Alps): their origin by focused percolation of pyroxenite-derived melt.
No full textIn the Balmuccia Massif, an Alpine peridotite thought to represent part of the subcontinental mantle, a 50 m thick and 150 m long dunite body, which occurs as a subconcordant, tabular structure, has been recently recognised. The contacts with the host spinel-facies depleted lherzolite are sharp. The dunite body is composed of spinel-rich dunite containing centimetre-size lenses of relict Cr-diopside websterite, spinel-poor granoblastic dunite and virtually monomineralic Cr-spinel layers exhibiting flow structures. Orthopyroxene is a minor, relict phase in all the lithologies; clinopyroxene is intergranular and amphibole is a minor accessory phase. Overall the dunite body is fairly refractory (Fo in olivine: 90.7-93.8). Strontium and neodymium isotope ratios of clinopyroxene separates from the dunitic body resemble those of a Cr-diopside websterite suite that forms a series of dykes cutting the main peridotite host. It is proposed that the dunites were generated in a part of the mantle veined byearly Cr-diopside websterites by a three-stage process involving partial melting of pyroxenite, infiltration of the pyroxenite-derived melt into the depleted lherzolite and its consequent open-system partial melting and focused flow of the resultant partial melts leading to the production of reactive dunite channels through both peridotite and pyroxenite. This process has been simulated using pMELTS assuming that the pyroxenite partially melts at 1.5 GPa and focused melt transport occurs at pressures greater than 0.7 GPa. The results show that, depending on the focusing factor assumed, dunite can form from peridotite at P < 1.2 GPa and from pyroxenite at P < 1.1 GPa, in both cases over a large pressure range. The model accounts for specific characteristics of the dunite, such as its refractory composition, the presence of orthopyroxene relics, the occurrence of relict websterite lenses in the spinel-rich dunites and the flow structures in the Cr-spinel layers. The proposed mechanism allows dunite formation to occur well within the spinel stability field, and therefore at greater depth than dunites in ophiolites,which generally formed within the plagioclase stability field. The aggregated model melts extracted from the segments where dunite forms are high-Mg alkali basalts resembling, after olivine fractionation, the compositions of enriched-type mid-ocean ridge basalt from slow- and ultraslow-spreading ocean ridges
Formation of highly-refractory dunite by focused percolation of pyroxenite-derived melt in the Balmuccia peridotite massif (Italy)
No full textA 50 m thick and 150 m long dunite body occurs as a subconcordant, tabular structure in the Balmuccia Massif, an Alpine peridotite thought to represent part of the subcontinental mantle. The contacts with the host spinel-facies depleted lherzolite are sharp. The dunite body is composed of spinel-rich dunite containing centimetre-size lenses of relict Cr-diopside websterite, spinel-poor granoblastic dunite and virtually monomineralic Cr-spinel layers exhibiting flow structures. Orthopyroxene is a minor, relict phase in all the lithologies; clinopyroxene is intergranular and amphibole is a minor accessory phase. Overall the dunite body is fairly refractory (Fo in olivine: 90·7–93·8). Strontium and neodymium isotope ratios of clinopyroxene separates from the dunitic body resemble those of a Cr-diopside websterite suite that forms a series of dykes cutting the main peridotite host. It is proposed that the dunites were generated in a part of the mantle veined by early Cr-diopside websterites by a three-stage process involving partial melting of pyroxenite, infiltration of the pyroxenite-derived melt into the depleted lherzolite and its consequent open-system partial melting and focused flow of the resultant partial melts leading to the production of reactive dunite channels through both peridotite and pyroxenite. This process has been simulated using pMELTS assuming that the pyroxenite partially melts at 1·5 GPa and focused melt transport occurs at pressures greater than 0·7 GPa. The results show that, depending on the focusing factor assumed, dunite can form from peridotite at P < 1·2 GPa and from pyroxenite at P < 1·1 GPa, in both cases over a large pressure range. The model accounts for specific characteristics of the dunite, such as its refractory composition, the presence of orthopyroxene relics, the occurrence of relict websterite lenses in the spinel-rich dunites and the flow structures in the Cr-spinel layers. The proposed mechanism allows dunite formation to occur well within the spinel stability field, and therefore at greater depth than dunites in ophiolites, which generally formed within the plagioclase stability field. The aggregated model melts extracted from the segments where dunite forms are high-Mg alkali basalts resembling, after olivine fractionation, the compositions of enriched-type mid-ocean ridge basalt from slow- and ultraslow-spreading ocean ridges
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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