1,721,018 research outputs found
The heterogeneous tethyan oceanic lithosphere of the alpine ophiolites
No full textThe Alpine-Apennine ophiolites are lithospheric remnants of the Jurassic Alpine Tethys Ocean. They predominantly consist of exhumed mantle peridotites with lesser gabbroic and basaltic crust and are locally associated with continental crustal material, indicating formation in an environment transitional from an ultra-slow-spreading seafloor to a hyperextended passive margin. These ophiolites represent a unique window into mantle dynamics and crustal accretion in an ultra-slow-spreading extensional environment. Old, pre-Alpine, lithosphere is locally preserved within the mantle sequences: these have been largely modified by reaction with migrating asthenospheric melts. These reactions were active in both the mantle and the crust and have played a key role in creating the heterogeneous oceanic lithosphere in this branch of the Mesozoic Western Tethys
Records of mantle-crust exchange processes during continental subduction-exhumation in the Nonsberg-Ultental garnet peridotites (Eastern Alps)
No full textIn the Nonsberg-Ultental area (Tonale nappe), Grt-bearing peridotites occur in high-P migmatitic gneisses enclosing relics of
eclogites. The peridotites record the transformation of high-T Spl-lherzolites to coronitic Grt+Spllherzolites to fine-grained Amph±Grt-peridotites. The transformation is preceeded by LILE
enrichment and intrusion of hot melts, and accompanied by deformation, hydration, LILE enrichment and LILE/HFSE fractionation. High-P metamorphism of peridotites and eclogites and early migmatization of the country gneisses were virtually
coeval and possibly isofacial. The peridotites may represent former mantle-wedge material that was subducted and cooled due to incorporation in a crustal slab and then metasomatized by hydrous fluids left after crystallization of leucosomes. Possible directions for further work on this and other sectors of the Variscan belt where broadly similar rock associations have been found are proposed
Melt-versus fluid-induced metasomatism in spinel to garnet wedgw peridotites (Ulten Zone, eastern Italian Alps) : clues from trace element and Li abundances
No full textMelt- versus fluid-induced metasomatism in spinel to garnet wedge peridotites (Ulten Zone, Eastern Italian Alps): clues from trace element and Li abundances
No full textMelt- versus fluid-induced metasomatism in spinel to garnet wedge peridotites (Ulten zone, eastern Italian Alps): clues from trace element, Li and Be abundances.
No full textThe Ligurian Ophiolites: a journey through the building and evolution of slow spreading oceanic lithosphere
No full textThe Ligurian ophiolites constitute an accessible and unique window to track the opening and evolution of slow spreading oceanic lithosphere. The Internal Ligurian ophiolites consist of km-scale gabbroic bodies intruded into depleted mantle peridotites and bear remarkable structural and compositional similarities to oceanic lithosphere from slow and ultra-slow spreading ridges. The External Ligurian ophiolites are associated with continental crust material and include mantle sequences retaining a subcontinental lithospheric origin. This field trip explores two gabbro-peridotite associations from the Internal Ligurian ophiolites: i) the Bracco-Levanto ophiolite, which includes a km-scale gabbroic body recalling the oceanic core complexes from modern spreading centres (e.g. the Atlantis Massif, Atlantic ocean); ii) the Scogna-Rocchetta Vara ophiolite, which lacks the basalt layer similar to the nonvolcanic sections from Atlantic and Indian oceans. The peridotites and the gabbros from both these ophiolites record a composite history involving deformation and alteration from high temperature to seafloor conditions. The field excursion also explores peridotite bodies from the External Ligurian ophiolites, representing a nice example of MORB-type pyroxenite-bearing mantle
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
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