1,720,956 research outputs found
GEOCHEMISTRY OF PALEOFLUIDS IN MINERALIZATION ALONG SEISMOGENIC FAULTS IN THE IRPINIA AREA (SOUTHERN ITALY)
Full text linkThe present PhD Thesis Dissertation includes the results of a integrated and multidisciplinary study of fault-related calcite veins from the Contursi Hydrothermal basin (Irpinia area, southern Italy). The whole Contursi hydrothermal activity takes place within a seismically active portion of the southern Apennines of Italy, where destructive earthquakes unfortunately have occurred in recent times. The Contursi village lies close (ca. 1 – 5 km) to the epicentral area of the MW = 6.9, 1980 Irpinia earthquake, and the local fault system is well-exposed along the numerous fault scarps dissecting Mesozoic shallow-water carbonates pertaining to the Apennine Platform. The Contursi hydrothermal activity is characterized by the outgassing of deep sourced CO2 coupled with mantle-derived volatiles such as He (Buttitta et al., 2023). In order to gain news insight into the modalities of crustal-scale fluid circulation along active extensional fault systems, in this work I has been investigated the paleofluids that precipitated calcite minerals within fault-related veins of the aforementioned Contursi Hydrothermal Basin. Specifically, tackle the source of the mineralizing paleofluids and the modalities of fault-related fluid circulation by integrating the results of field structural studies with microstructural, stable isotopes (δ13C and δ18O) and trace elements characterizations of the calcite veins, and both noble gases and δD-H2O of Fluid Inclusion (FI).
The studied fault-related calcite veins crosscut the Mesozoic Apennine Carbonate platform exposed in the Contursi area, which is about 40 km2-wide and characterized by the exposure of high-angle fault forming two main sets roughly striking NNW-SSE and ENE-WSW, respectively. There, in close proximity to the main slip surfaces, both comb and slip-parallel calcite veins (labelled as C and SP, respectively) were sampled. In accordance with previous works, both C and SP-veins are interpreted as co-seismic or early post-seismic features, whose formation as brittle extensional fractures occurred during multiple seismic ruptures. Most of the sampled fault-related calcite veins include blocky calcite crystals, whose precipitation from the fault-controlled paleofluids, likely post-dated the occurrence of the aforementioned brittle fracturing. Only two samples show a fibrous texture of the calcite crystals, which are interpreted as syn-kinematics, and formed during small increments of shear-induce dilation and mineral precipitation. Due to their variable sized and inner texture, incremental crack and seal processes are documented for some studied calcite veins samples.
Most of calcite veins samples show δ13C and δ18O values similar to those that characterize the Mesozoic marine carbonate field (Apennine Carbonate platform). Such an isotopic signature is consistent with mineral precipitation form paleofluids in an isotopic equilibrium with the encompassing carbonate host rocks. This interpretation is supported by the calculated δ18Oparentalfluids values, δD values measured in Fluid Inclusion (FI) and trace and REE content, which all point out towards the long residence time of the mineralizing fluids within the faulted carbonate host rocks. In addition, since the homogenization temperatures (between 100 °C and 130°C) obtained by FIs analysis are similar to the maximum burial temperatures experienced by the Apennine Carbonate Platform host rock (100°C – 120°C), assuming a geothermal gradient of ~30 °C/km, and taking known values of groundwater temperature into account, the geochemical data are interpreted as due calcite precipitation within the fault-related veins from paleofluids that localized at depths of ca. 3 ~ 4 km, and interacted with the Mesozoic carbonates. Differently, some calcite veins are characterized by δ13C values similar to those reported above, but by a pronounced depletion in δ18O which, together with the high homogenization temperature assessed for the FIs, are consistent with the paleofluids derived from a deep reservoir from depths of ca. 8 ~ 10 km. Accordingly, similar to the conceptual model invoked for crustal-scale fault-related fluid flow in the High Agri Valley of southern Italy, results point out to an ascendance of deep fluids towards the Earth’s surface that likely occurred thanks to the temporary rupture of the tectonic mélange forming the sole thrust of the southern Apennine fold-and-thrust belt, and the main seal of overpressurized fluids entrapped within the Apulian carbonates.
Regarding to the results of noble gases analyses performed on the FIs trapped within the calcite veins, most of the investigated samples shows R/Ra values comprised between 0.53 and 1.38 Ra, which is consistent with a prevalent crustal component added to mantle one (up to 20%), and also with a negligible meteoric component. The variability of He isotopic signature in the FIs, that is not consistent with narrower range of He ratios for the current outgassing, can be due to early trapping processes (probably earthquakes occurred in the past). Based on co-seismic dilatancy model, an “early trapping” hypothesis for He isotopic signal, the following model of fault-related fluid circulation in the Contursi Hydrothermal basin is here proposed: the co-seismic dilatancy formed transient of high-permeability pathways through the upper crust, allowing the ascendence of likely overpressured fluids from rock volumes underneath the impermeable tectonic mélange made up of Apulian carbonates. During ascendence towards the Earth’s surface, these overpressured fluids characterized by crustal and mantle derived He (up to 20%), reached shallower crustal volumes (1-5 km), and were either in thermal and isotopic equilibrium or in disequilibrium with the Apennine carbonates generating the two distinct groups of calcite veins and associated FIs. For the fluids in thermal and isotopic equilibrium with the Apennine carbonate host rock, the mixing with the meteoric and/or shallow derived fluid cannot be excluded, as demonstrated through noble gas analysis (i. e. 40Ar/36Ar and relationship with R/Ra values) of some of the study samples. The high-permeability pathways permitting the rapid ascendance of deeper fluids towards shallow crustal conditions is still active in the Irpinia area, as suggested by soil gas measurements indicating a current outgassing of mantle-derived fluids. However, regarding the mantle component measured in the study sample, two possible scenarios are envisioned. First, the mantle-derived fluids derive from outgassing of magmatic intrusion at depth. Second, a through-going structural discontinuity that crosscut the whole crust down to the mantle channeled the deep fluids a depth.
In conclusion, the results of this study showed that the Contursi hydrothermal basin forms a great natural laboratory to gaining a new knowledge on modalities of crustal-scale fluid circulation associated with crustal deformation and earthquake faulting. Such investigations are fundamental to understanding the role of deep fluids in crustal deformation over time, and in the processes of earthquakes nucleation and rupture propagation. Moreover, this study provides hints upon long-time multidisciplinary integrated monitoring approach in tectonically active continental regions, so that the new insights can be helpful to improve earthquake forecast
Pace O., Buccione R., Punturo R., Zummo F. Rizzo G. 2023. Mineralogical and petrographic characterization of fibrous amphiboles in the blueschists of the Diamante-Terranova Unit (Calabrian-Peloritan Orogen, southern Italy). Congresso congiunto SIMP-SGI-SOGEI-AIV “The Geoscience paradigm: resources, risk and future perspectives”, 19-21 Settembre 2023, Potenza.
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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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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