1,721,020 research outputs found
A petrographic and fluid inclusions study of high-grade metamorphic hornfelses (Gennargentu Igneous Complex, sardinia, Italy): preliminary data.
No full textPreliminary crust-basalt interaction experiments at 0.8–1.0 GPa: new hybrid melts formation
No full textA new test for equilibrium based on clinopyroxene–melt pairs: Clues on the solidification temperatures of Etnean alkaline melts at post-eruptive conditions
No full textElectrical conductivity of a phonotephrite from Mt Vesuvius: The importance of chemical composition on the electrical conductivity of silicate melts
No full textThe bulk electrical conductivity of the phonotephritic lava from the 1944 eruption of Mt Vesuvius was measured using complex impedance spectroscopy in a multianvil apparatus at 1 GPa and temperatures up to
700 °C. Melting experiments prior to the electrical measurements were also performed on this sample in a
piston cylinder apparatus in order to gauge how bulk conductivity varies as a function of its melt fraction.
Unlike the behaviour found in basaltic rocks in which conductivity increases with increasing melt fraction,
we observe a conductivity decrease of the order of a factor of ten for samples at 700 °C ranging in melt
fraction from 32 vol.% to completely molten.We attribute this anomalous behaviour to the progressive loss of highly conductive leucite upon melting. The addition of potassium to the melt phase, however, does not
result in an increase of the total alkali concentration due to the melting of other mineral components. We
also present an empirical model to predict the electrical conductivity of fully molten silicate liquids as a function of temperature and chemical composition, based on conductivity data for natural silicate liquids
found in the literature. The inclusion of compositional terms reduces the error by more than a factor of four
with respect to a composition independent, temperature-only parameterization
The role of cooling rate in the origin of high temperature phases at the chilled margin of magmatic intrusions
No full textBoth large (i.e. from hundreds to thousands of metres thick) and small (i.e. from centimetres to a few metres
thick) magmatic intrusions are characterized by mineral compositional variations proceeding from the outermost
to the innermost part of the intrusive body. However, in the case of large intrusions, mineral compositions
become progressively more primitive (e.g. An-rich plagioclases and En-rich pyroxenes) from the
chilled margin towards the interior; whereas, the opposite occurs for small intrusive bodies.
Since it is unclear to what extent variable cooling rate conditions may alter the phase compositions, we have
performed isothermal and dynamic experiments within a temperature interval of 1250–1100 °C using four
different cooling rates of 150, 50, 10 and 2.5 °C/h. Numerical simulations of thermal regimes in and around
small and large magmatic intrusions have also been performed and compared with phase compositional variations
observed in our laboratory experiments.
Results indicate that, over rapid cooling rate conditions, the crystal compositions faithfully reproduce those of
high-temperature formations, i.e. An-rich plagioclases, En-rich pyroxenes and Usp-poor spinels. However,
such a process is limited to a maximum distance of 2–3 m from the margin of the intrusion. Moreover, in active
volcanic systems, heat fluxes are released from the main regions of magma storage into host rocks; therefore,
only magmas solidifying at the contact of cold wall rocks may develop chilled margins with features
related to rapid cooling rate conditions. In the presence of hot host rocks, thermal gradients are significantly
reduced and the role played by cooling dynamics on textural and compositional variations of minerals is
practically negligible
Strumentazioni in uso nel campo della petrologia sperimentale
No full textThis guide reports the description of the experimental
apparata in use in the experimental
petrology along with an accurate description of
some applications of these instrumentations.
After a brief introduction concerning what is the
experimental petrology and what is used for, we
provide a description of the starting materials
used in this field of the Earth Sciences.
Moreover, particular attention is focused on
these apparata used all around the world. We,
finally, introduce some examples of different
studies conducted with the different experimental
equipments.
The aim of this guide is, then, to give information
concerning the equipments and their potentiality.Published1-202.3. TTC - Laboratori di chimica e fisica delle rocceN/A or not JCRope
Strumentazioni in uso nel campo della petrologia sperimentale
No full textThis guide reports the description of the experimental
apparata in use in the experimental
petrology along with an accurate description of
some applications of these instrumentations.
After a brief introduction concerning what is the
experimental petrology and what is used for, we
provide a description of the starting materials
used in this field of the Earth Sciences.
Moreover, particular attention is focused on
these apparata used all around the world. We,
finally, introduce some examples of different
studies conducted with the different experimental
equipments.
The aim of this guide is, then, to give information
concerning the equipments and their potentiality.Published1-202.3. TTC - Laboratori di chimica e fisica delle rocceN/A or not JCRope
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
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