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Volatile evolution of magma in the Campi Flegrei (Italy) volcanic system based on melt inclusions.
No full textLa comunicazione riporta i risultati di indagini sperimentali su melt inclusions nei prodotti magmatici dei Campi Flegre
Origin of the nodules in the 18.6 ka Sarno plinian eruption of Mt Somma-Vesuvius (Italy) and their significance
No full textDescription and petrography of plinian Sarno products of Mt Somma-Vesuvius. Studies and preliminary results on melt inclusion
Composition and origin of nodules from the 20 ka Pomici di Base (PB)-Sarno eruption of Mt. Somma-Vesuvius, Italy
No full textNodules (coarse-grain "plutonic" rocks) were collected from the ca. 20 ka Pomici di Base (PB)-Sarno eruption of Mt. Somma-Vesuvius, Italy. The nodules are classified as monzonite-monzogabbro based on their modal composition. The nodules have porphyrogranular texture, and consist of An-rich plagioclase, K-feldspar, clinopyroxene (ferroan-diopside), mica (phlogopite-biotite) ± olivine and amphibole. Aggregates of irregular intergrowths of mostly alkali feldspar and plagioclase, along with mica, Fe-Ti-oxides and clinopyroxene, in the nodules are interpreted as crystallized melt pockets. Crystallized silicate melt inclusions (MI) are common in the nodules, especially in clinopyroxenes. Two types of MI have been identified. Type I consists of mica, Fe-Ti-oxides and/or dark green spinel, clinopyroxene, feldspar and a vapor bubble. Volatiles (CO2, H2O) could not be detected in the vapor bubbles by Raman spectroscopy. Type II inclusions are generally lighter in color and contain subhedral feldspar and/or glass and several opaque phases, most of which are confirmed to be oxide minerals by SEM analysis. Some of the opaque-appearing phases that are below the surface may be tiny vapor bubbles. The two types of MI have different chemical compositions. Type I MI are classified as phono-tephrite - tephri-phonolite - basaltic trachy-andesite, while Type II MI have basaltic composition. The petrography and MI geochemistry led us to conclude that the nodules represent samples of the crystal mush zone in the active plumbing system of Mt. Somma-Vesuvius that were entrained into the upwelling magma during the PB-Sarno eruption
Magma chamber homogeneity recorded by melt inclusions from Mt Somma-Vesuvius, Italy.
No full textLa comunicazione riporta i risultati di esperimenti condotti sui prodotti dell'eruzione di Sarno del complesso vulcanico Mt Somma-Vesuvi
Origin of nodules in the 20 ka Pomici di Base-Sarno eruption of Mt. Somma-Vesuvius, Italy, based on geochemistry of melt inclusiuons.
No full textLa comunicazione riporta i risultati di una indagine sperimentale sulle pomici dell'eruzione delle Pomici di Base-Sarno del Mt Somma-Vesuvi
Small and large scale inhomogeneities in the magma chamber of the 18.6 ka Sarno plinian eruption of Mt Somma-Vesuvius (Italy) based on melt inclusion studies in nodules
No full textDescription and petrography of plinian Sarno products of Mt Somma-Vesuvius. Studies and preliminary results on melt inclusion
Constraints on the origin of the nodules from the Sarno (Pomici di Base) plinian eruption of Mt. Somma-Vesuvius (Italy) based on geochemical studies
Full text linkFour, “sub-effusive” type of nodules, collected from the uppermost layer of the Sarno (Pomici di Base - PB) plinian eruption, were studied in this doctoral research. This thesis presents new geochemical data (major/trace elements and volatiles) of both melt inclusion (MI) and minerals of the studied nodules. The main goal of this research was to constrain the formation depth of the nodules, and hence the depth of the magma chamber associated with the Sarno (PB) eruption, but later the focus shifted on the origin of melts trapped in representative minerals of the nodules.
A detailed petrographic study was carried out on all four selected nodules. They have porphyrogranular texture, but they differ in terms of modal composition. Three of the four nodules contain clinopyroxene and olivine as phenocrysts (Type A nodules), whereas one contains amphibole (Type B). The groundmass in both cases is completely crystallized, and crystallized melt pockets were also recognized in the interstitial space.
MI are abundant in clinopyroxenes in the nodules. All MI observed in this study are partially to completely crystallized, suggesting they cooled relatively slowly after trapping. Two types of MI can be distinguished based on petrography. Type I consists of mica, Fe-Ti-oxide minerals and/or dark green spinel, clinopyroxene, feldspar and a vapor bubble. No volatile species (CO2, H2O) were detected in the bubbles during Raman analysis. Type II inclusions are generally lighter in color and they contain feldspar and/or glass and oxides. Both types of MI are randomly distributed in the crystals or occur along a growth zone and are interpreted to be primary. Some of the MI were analyzed by LA-ICP-MS without homogenizing them first, but most of the MI were heated to produce a homogeneous glass phase before analysis. MI homogenized between 1202-1256 °C, but mostly above 1220 °C. Type I MI can be classified as phono-tephrite – tephri-phonolite – basaltic trachy-andesite, whereas Type II MI have mainly basaltic composition. The two different types of MI also show different trace element patterns. Type I MI are more enriched in incompatible elements compared to Type II MI. The heating experiments revealed, however, that only Type I MI are representative of the crystallizing melt. The compositions of Type II MI are strongly modified by accidentally trapped An-rich feldspar.
The comparative study of Type I MI and bulk rock of Mt. Somma-Vesuvius concluded that compositions of Type I MI are similar to the bulk composition of the pre-Sarno, older Somma lava rocks rather than the Sarno (PB) volcanics. Therefore, the NLM1-1a nodule and perhaps the other two Type A nodules have formed from the same melt that was erupted during the early history of Mt. Somma. The presence of older, crystallized material in the younger eruptive products indicates that the Sarno (PB) magma erupted from the same (or a deeper) magma chamber(s) that fed the older eruptions. The thermobarometer models estimate at least 4 kbar (~12 km) for nodule formation.
MI were also studied in amphibole from Type B nodules. The petrographic and geochemical studies, however suggested that the compositions of these MI are strongly modified by trapping solid inclusions, including phlogopite and less commonly, apatite. Therefore, the origin of Type B nodules cannot be determined based on MI compositions. Most likely this nodule crystallized from a melt that was more enriched in light REE, but less enriched in Ti, compared to melts from which Type A nodules crystallized. Thermobarometer models estimate at least 8 kbar (~24 km) for Type B nodule formation
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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