1,721,025 research outputs found
The "Venice Granodiorite": its features and consequent constraints on the "Caledonian" and Variscan events in the Alpine domain
No full textAn Ordovician granodiorite body was sampled along an exploratory well in the Northern
Adriatic Sea, close to the Lagoon of Venice. It stands 4711 m below the sea floor, and is buried under a sedimentary
cover spanning from Triassic to Quaternary. It contains several metasedimentary xenoliths, as well as
some microgranular enclaves. The drilled core is a unique example of the Southalpine crystalline basement under
the Po Plain. The granodiorite is undeformed, and does not display post-emplacement metamorphic overprints.
It therefore limits southwards the possible extent of the Variscan orogenic belt, which is well documented
in the Southalpine and Austridic metamorphic basements. The granodiorite is classified as an S-type granitic
rock, on the basis of major and trace element geochemistry and the occurrence of abundant metasedimentary
xenoliths. These features, together with the isotopic signatures, point to an anatectic origin of the granodiorite.
The metamorphic xenoliths are probably fragments from the wall-rocks of the pluton, and do not represent
restites of the main crustal source of the granodiorite. The microgranular enclaves probably represent parts of
chilled margins disrupted within the pluton, and do not indicate interaction with more mafic, mantle-derived
melts. The representative points of the granodiorite plot in post-collisional fields in some discriminant diagrams.
The age and many geochemical features of the Venice granodiorite are similar to those of the Austridic
metamorphosed granitoids occurring in the Eastern Alps, possibly indicating a unique geodynamic setting for
their genesis and emplacement. Together with the coeval calc-alkaline, mostly mantle-derived metagranitoids
occurring in the «Serie dei Laghi» (Western Southalpine), they define a magmatic suite which is consistent with
a convergent plate boundary tectonic setting
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
Petrography, age and geochemistry of the buried "Venice Granodiorite" (Northern Italy)
No full textA granodiorite body was sampled in an exploratory well in the Northern Adriatic Sea, close to the Venice Lagoon. It stands 4711 m below the sea floor, directly overlain by Triassic dolostones. The drilled core represents a unique evidence of the Southalpine crystalline basement underneath the Po plain. A Llandeilian emplacement age (461–463 Ma) is inferred by U/Pb single grain conventional dating, which supports the occurrence of an Ordovician plutonic event far southwards from the sites where it is well known in the Eastern Alps. The granodiorite is undeformed, and does not display metamorphic overprints: it therefore limits the extent of the Variscan metamorphic belt to the south. Major and trace element geochemistry, together with oxygen isotopic composition, mineralogy and occurrence of abundant metasedimentary xenoliths, point to an anatectic origin of the granodiorite
Pre-Variscan alkaline magmatism in the Eastern Apls: The Croda Nera metabasites and amphibolites
No full textThe Croda Nera (CN) amphibolites belong to the Austroalpine polymetamorphic Merano-Mules-Anterselva basement (MMA). The protoliths were affected by Variscan regional metamorphism, undergoing maximum P-T conditions typical of garnet amphibolite facies. During Oligocene, the MMA basement was intruded by several plutons. The CN body is located close to the Vedrette di Ries intrusion, which caused medium grade contact metamorphism, not exceeding 550° C, overprinting the older regional event.
In CN we identified ortho- and para-amphibolites, based on both petrographic and chemical grounds, employing different discriminant diagrams.
According to SCMR, the CN metabasites can be classified as amphibolites s.s., with minor garnet amphibolites, biotite+garnet amphibolites and monomineralic amphibolites. The most abundant phase is a subidiomorphic green amphibole. These crystals define the scistosity of the rock, when present. Sometimes they display a decussate microstructure. Garnet occurs as large porphyroblasts which include Amph + Bt + Ttn. Biotite, when present, is abundant (>10% vol.) and displays decussate microstructure. Plagioclase is usually very scarce, so that the rocks are melanocratic (M ≈ 90). Ti-bearing phases are Ttn and Ilm, the latter being often retrogressed into the former; Rt is absent. Calcite is widespread in variable amounts, from less than 1% vol. (ortho-amphibolites) to 15-20% vol. (calc-silicate para-amphibolites). Sporadic mylonitic fabric caused local retrogression to Act + Ep ± Chl greenschist assemblages. Clinopyroxene relics of likely igneous origin are sporadically observed, always bearing an hornblende corona. Amphibole is dominantly Mg-hornblende, with minor tschermakite and Fe-tschermakite. Garnet has a low Mg content (prp1-10) and a highly variable Ca (grs25-44), Fe (alm25-60 and Mn (sps1-15) contents. Plagioclase composition ranges from an12 to an33; in places, some pure albite crystals occur, especially within retrogressed deformed layers. Pyroxene relics have a composition close to the Di-Hd join (Ca > 0.94 a.p.f.u.); this fact, together with Na and Ti contents and the microstructural occurrence, points to an igneous origin of this phase, by crystallisation from alkaline magmas. Conventional ion exchange geothermobarometers, where applicable, yield pressures and temperatures lower than expected, indicating post-peak reequilibrations.
The bulk-rock chemistry of CN ortho-amphibolites highlights a mafic to ultramafic nature of the protoliths, which are classified as alkali basalts, basanites and picro-basalts. In a few samples, pyroxene cumulus phenomena have been detected. Major and trace element geochemistry indicates that many protoliths were primary liquids; possibly, only slight fractionation of olivine occurred sporadically. The REE are highly fractionated (LaN/YbN between 21 and 36), with no significant difference between LREE and HREE and no detectable Eu anomaly.
Discriminant diagrams employing immobile trace elements (e.g., Zr-Ti/100-3*Y, Th-Hf/3-Ta) confirm the alkaline nature of the protoliths and point to a within-plate tectonic setting for their emplacement.
Preliminary Nd isotope data on metaderivates from supposedly primary magmas yield ages of about 1100 Ma, calculated employing a linear evolutionary trend of the depleted mantle. They agree within error with other model ages in the MMA (Meli, unpublished); however such ages do not fit any previous model for this sector of pre-Variscan crust, being at the present state of knowledge somewhat controversial
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