1,720,994 research outputs found
The acid-sulfate zone and the mineral alteration styles of the Roman Puteolis (Neapolitan area, Italy): clues on fluid fracturing progression at the Campi Flegrei volcano
No full textActive fumarolic solfataric zones represent important structures of dormant volcanoes, but unlike emitted fluids,their mineralization are omitted in the usual monitoring activity. This is the case for the Campi Flegrei caldera in Italy, among the most hazardous and best-monitored explosive volcanoes in the World, where the landscape of Puteolis is characterized by acid sulfate alteration that is active at least since Roman time. This paper provides temperature, mineralogical, textural,compositional and stable isotope data for those solfataric terrains sampled at the crater and Pisciarelli slope of the Solfatara volcano between 2012 and 2019. Temperatures vary between 40 ° and 95 °C. Minerals include alunite with grain sizes generally larger than 20 μm, alunogen, native sulfur, well-ordered kaolinite, and, common at Pisciarelli, pyrite and NH4-sulfates. Sulfate terrains have higher contents of Ti, Ba, Au, As Hg and Tl relative to their parent substrate. The Pisciarelli slope is anomalous in terms of the presence of NH4. δ34S values for sulfides and native S range between -3.00 and 0.49 ‰ and from -4.42 to 0.80 ‰, respectively. Sulfates show δ 34S and δ 18O values in the range of -3.35 to 3.80 ‰ and between 0.3 and 31.33 ‰, respectively. The style of mineralization and the stable isotope geochemistry do produce complex and not completely consistent classifications and genetic information. We merge our data with volcanological information, data from exploration drillings and geophysical results. With the conceptual model we suggest a series of shallow and deep aquifers interconnected like “communicating vessels” through a main fault system that downthrows Solfatara with respect to Pisciarelli. Fluid outflow from the different discrete aquifers hosted in sediments – and possibly bearing biological imprints – is the main dataset that allows determination of the steam-heated environment with a supergene settings superimposed. Supergene conditions and high-sulfidation relicts, together with the narrow sulfate alteration zone buried under the youngest volcanic deposits, point to
the existence of a paleo-conduit. The data will contribute to monitor and evaluate the volcanic hazardsPublished1809–18313V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcaniciJCR Journa
High-silica zeolites in pyroclastic flows from Central Sardinia (Italy): clues on genetic processes and reserves from a mineralogical study
No full textThe island of Sardinia (Italy) presents some of the most interesting zeolite ores in Europe, most of which are associated with old pyroclastic deposits. In particular, the poorly welded ash and pumice pyroclastic flows of the Oligo-Miocene Allai unit were the suspected cause for the widespread zeolitization processes and their subsequent potential economic interest. Fourteen stratigraphic sequences of those Allai flows were sampled and studied, in order to fill the gap existing in the mineralogical database of Sardinian zeolites. A multi-analytical strategy has been used to determine for the first time the nature, the distribution and the textural relationships of the main zeolite types throughout the pyroclastic flows, as well as the geochemical features of the zeolite-bearing rocks. The overall data contribute to depict the main genetic process that involved a hydrothermal environment operative under a dominant closed system, at temperature near to 200 °C and progressively proceeded thanks to cooling and chemical variation of the fluids permeating the matrix. The investigated zeolites mainly consist of Ca-clinoptilolite and/or Na-mordenite, up to 38% in abundance. However, contrarily to the most common clinoptilolite + mordenite paragenesis, mordenite zeolitization is really abundant in the studied ignimbrites in relation to their pristine rhyolitic compositions. The weight percentages and distribution of the industrial minerals throughout the pyroclastic deposits presented by this work can be an important background information for an evaluation of the quality and the reserves of this zeolite mineralization aimed at a possible future exploitation and potential use.Published767-7882V. Struttura e sistema di alimentazione dei vulcaniJCR Journa
Late Quaternary uplift and sea level fluctuations along the Tyrrhenian margin of Basilicata - northern Calabria (southern Italy): New constraints from raised paleoshorelines
No full textNew analyses of marine terraces in the Tyrrhenian Sea margin of Basilicata - northern Calabria (southern Italy) have been carried out. In the study area, c. 25 km in length, an impressive flight of marine terraces occurs, with the highest terraces reaching ~160 m a.s.l. Detailed geomorphological-stratigraphical analyses on remnants of paleoshorelines located within 60 m a.s.l. have shown that the rocky coast of the investigated coastal stretch has been affected by multiple relative sea-level fluctuations, during which reworking of older shorelines has occurred. Dating of the coral Cladocora caespitosa and speleothems, either predating or postdating single paleoshorelines, has allowed the construction of a chronological framework for the identified relative sea-level markers, and their correlation with MIS 7, MIS 6e and distinct peaks of MIS 5. A mean uplift rate of c. 0.25 mm/y since the Last Interglacial has been quantified, one order of magnitude larger than previous estimates. The uplift rate value has been used to infer the elevations of MIS 5a, 5c and 6e sea level peaks, which are higher than those reported in most sea level curves worldwide, although consistent with several findings from the western Mediterranean. Our results demonstrate that a mere sequential correlation may be misleading in the interpretation of flights of marine terraces and indicates that multiple age controls are crucial to unravelling the complex interaction between uplift and sea-level fluctuations in uplifted coastal areas. The reconstructed MIS 5a, 5c and 6e sea level paleo-elevations, besides contributing to the assessment of late Quaternary sea-level fluctuations in the Mediterranean Sea, may contribute to constrain coeval ice sheets volume variations
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
Remote Sensing and Mineralogical Analyses: A First Application to the Highly Active Hydrothermal Discharge Area of Pisciarelli in the Campi Flegrei Volcanic Field (Italy)
No full textThis paper explored the relationship between acidic sulfate alteration, geostructural frameworks, and geomorphological changes that can be observed in active volcanic hydrothermal systems. The target area was Pisciarelli in the Campi Flegrei volcano, where diffuse acidic sulfate alteration and hydrothermal dynamics have been growing since 2012, causing a progressive deterioration of landscapes. Terrestrial Laser Scanner (TLS), photogrammetry of proximity survey, geological field work, mineralogical and geochemical analysis with Optical Microscopy (OM), electron microscopy, and energy dispersive micro-analysis (BSEM-EDS) and X-ray Powder Diffraction (XRPD) to characterize (and monitor) altered rock outcrops were repeatedly carried out in the area. We present the multi-temporal acquisition and analysis referring to Terrestrial Laser Scanning (TLS) datasets (2014 survey) with 3D-point clouds obtained from the Structure for Motion (SfM) photogrammetry (2021 survey) with a high-resolution digital camera aimed at evaluating volumetric changes on the mostly damaged and altered fault scarp. For each survey, we obtained a vertical Digital Elevation Model (DEM) and a true color RGB orthomosaic that provided the setting of the area at the different times and its evolution through their comparison. Changing sites were examined in the field and characterized for mineralogical and geochemical purposes. The investigated slope lost up to about 4 m3 of deposits between 2014 and 2021, mostly related to hydrothermal alteration induced by gas emissions and meteoric infiltration. Our methodological approach appears promising to evaluate evolution and rock-fall susceptibility of solfataric terrains subjected to hydrothermal dynamics
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