1,720,958 research outputs found
Raman spectroscopy for fluid inclusion analysis
No full textRaman spectroscopy is a versatile non-destructive technique for fluid inclusion analysis, with a wide field of applications ranging from qualitative detection of solid, liquid and gaseous components to identification of polyatomic ions in solution. Raman technique is commonly used to calculate the density of CO2 fluids, the chemistry of aqueous fluids, and the molar proportions of gaseous mixtures present as inclusions. Raman spectroscopy has been applied to measure the pH range and oxidation state of fluids. The main advantages of this technique are the minimal sample preparation and the high versatility. Present review summarizes the recent developments of Raman spectroscopy in fluid inclusions research to provide support for laboratory analyses. (C) 2011 Elsevier B.V. All rights reserved
Paleoclimate reconstruction during the Messinian evaporative drawdown of the Mediterranean Basin: Insights from microthermometry on halite fluid inclusions
No full text""Data constraining the paleoenvironmental conditions during the Messinian evaporative drawdown of the. Mediterranean basin are still conflicting. Here we present a comprehensive paleoclimatic reconstruction. during Messinian halite deposition from several Italian sites. We performed fluid inclusion analyses to define. better both the composition of the Mediterranean water body and the paleotemperatures of the Messinian. brine during halite crystallization. We measured homogenization temperatures on 218 primary all-liquid fluid. inclusions in Messinian halite from the Volterra, Crotone, and Caltanissetta evaporite basins. These. measurements provided mean homogenization temperatures of 17–18C, with a range between 10–11C and. 28–29C, which should be close to the SST of the Mediterranean Sea during halite deposition. The occurrence. of major elements such as Cl, Na, Mg, S, Ca, and K within the halite fluid inclusions, together with the. presence of minerals such as pentahydrite, polyhalite, and Ca-, K-, and Mg-sulfates, indicates that these salt. bodies originated from mainly marine water. Taking into account both the present-day annual SST of the. Mediterranean Sea around the sampling sites, which ranges between 18 and 20C, and the lower latitude of. the Mediterranean Basin during the Messinian Salinity Crisis, our homogenization temperatures point to a. colder climate during the Messinian halite deposition compared to the present interglacial climate stage. This. conclusion is consistent with halite deposition during a Late Miocene glacial interval (TG12)."
A Late Variscan tin province associated to the ilmenite-series granites of the Sardinian Batholith (Italy): The Sn and Mo mineralisation around the Monte Linas ferroan granite
No full textThe characterisation of the late Variscan intrusion of Monte Linas (southern Sardinia) allowed to firstly study some Sn-bearing ores of this area and their relationships with the surrounding intrusives. The Monte Linas pluton was emplaced at ca. 290 Ma at a shallow crustal level between allochthonous units and the foreland of the Sardinian Variscan belt. The pluton emplaced in a post-collisional regime into a previously exhumed low-grade basement, forming a coarse-grained monzogranite that is capped by an almost continuous sub-horizontal sheet of fine-grained rocks. The rocks within the pluton are ferroan F-bearing granites, belonging to the ilmenite-series. They have alumina saturation index values indicative of sub-aluminous to slightly peraluminous granitoids, as also indicated by the chemical composition of biotite within the pluton. The new data of this study indicate that the Monte Linas pluton formed from water-undersaturated magmas under low-fO2 conditions at temperatures > 850 °C. The later stages of magmatism were characterised by boiling and fluid expulsion at confining pressures of < 1 kbar, producing fayalite-bearing pegmatites, miarolitic facies and greisening. A wide variety of mineral deposits are associated with the Monte Linas pluton, including different types of Sn-bearing and Mo-bearing ores. Sn-bearing ores are represented by 1) Sn–As and Sn–Pb–Zn–Cu veins, and 2) “wrigglite” skarn Fe-Zn-Sn ores. Field and analytical studies, including fluid inclusion analyses, EMPA and SEM-EDS, allow to refer these deposits to the evolution of initial highly saline, hypothermal magmatic fluids, as confirmed by parageneses and fluid inclusion analyses of cassiterite in veins, which provide evidence of polyphase processes that started at temperatures close to 400 °C. The hydrothermal systems were initially characterised by low-fO2 and high-chlorine solutions that mobilised Sn and underwent rapid changes in physicochemical conditions that led to the deposition of cassiterite. In the “wrigglite” F-rich genetic environment, a role of fluoride as complexing agent for Sn can be inferred. The Monte Linas pluton is also characterised by Mo deposits, not typical in ilmenite series granites; they occur both as greisens and veins. Mo was mobilized as a result of rapid increases in fO2 within the magmatic system, and precipitated in a fS2-rich environment nearby the contact between the intrusion and the surrounding country rocks. The variety of Sn mineralising events around the Monte Linas pluton confirms the role of physicochemical characters of magmas and of magmatic processes in the genesis of tin deposits. The occurrence in southern Sardinia of a wide suite of ilmenite-series ferroan granites emplaced in similar geological contexts allows to consider the idea of a low-grade tin province and opens the way to further explorations
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
Cassiterite Vein Deposits Related to Late Variscan Ilmenite-series in SW Sardinia (Italy): Insights for a New Tin Province
No full textIn the Arburese region (SW Sardinia, Italy) several vein-type ore deposits, including small Sn minerali-zations, are arranged, with different trends, around two contrasting late-to post-collisional shallow plutons: the Arbus and the Monte Linas plutons, dated at 304 +/- 1Ma, and 289 +/- 1Ma respectively. These intrusions belong to two different ilmenite suites: an earlier high-K rock-series (Arbus Pluton), and a later F-bearing rock-series (Monte Linas Pluton). In the apical portion, close to the host rocks, they suffered greisen type alteration testified by secondary muscovite, B-rich and F-bearing phases. Preliminary fluid inclusion analyses in cassiterite veins, documented polyphase mineralizations and temperature close to 400 degrees C. The petrochemical features and the emplacement history of the Linas pluton meet high favourability for tin accumulation. Despite of their limited extent, the Sn ores of SW Sardinia have a metallogenic relevance as they document a long lasting metallogenic epoch all over the South Variscan Realm
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