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Spatial and compositional effects of intersection zones in the five-element (Ni-Co-As-Bi-Ag) vein system of the Southern Arburèse district (SW Sardinia)
No full textThe Arburèse district (SW Sardinia) is regarded as potential source of critical raw materials related to the large Montevecchio vein system, mined in the past for Pb and Zn ores. In the > 5 km-long, poorly exploited Southern branch of the system, the ores have been defined as five-element (Ni-Co-As-Bi-Ag) polymetallic veins (Moroni et al., 2019). They are hosted in late-Ordovician metasandstones and Silurian carbonaceous shales between two granitoid intrusions: the Arbus (304 Ma) and Mt. Linas (289 Ma) plutons. Investigations in the Perda S’Oliu, Sa Menga, Acqua Is Prunas and Pira Inferida old mines highlighted a pinch-and-swell attitude, with alternating ore shoots and low-mineralized zones. Prevalence of breccia/cockade textures and complex ore mineralogy indicate multiple hydrothermal mineralizing pulses, resulting in the overall mineral
assemblages: i) native Bi; ii) Ni-Co arsenides/antimonides and sulfarsenides/sulfantimonides + quartz; iii) Zn, Pb, Cu, Bi sulfides and Cu-Ag-Sb sulfosalts + siderite; iv) quartz; v) pyrite and calcite. As noted in the recent literature on similar European ore deposits (Markl et al., 2016), mineralization processes were mainly controlled a) by redox environments, and b) by intersections with other mineral systems. Native Bi and arsenide precipitation occurred under rapidly evolving reducing conditions, favored by interaction of hydrothermal fluids with carbon-rich lithologies, well represented in Ordovician and Silurian host rocks. Moreover, field
surveys in the studied localities pointed out that relevant ore shoots also correspond to intersection zones (IZs) with earlier hydrothermal systems related to the Monte Linas pluton (Deidda et al., 2021). Brecciated domains of IZs were critical both for fluid circulation and entrapment, but also for ore compositions. Indeed, the high-Bi contents of the five-element ore in the Pira Inferida mine are explained by intersection with a granite-related wolframite-quartz (Bi-Au-Te) vein system, from which abundant Bi (±Au) was remobilized.
Similarly, in the Sa Menga mine, skarns and veins rich in Ni-Co-bearing arsenopyrite and Fe sulfides were As and metal sources for the cross-cutting five-element ore. In conclusion, where the low-temperature fiveelement system is close to the inferred contact with the Mt. Linas granite, or it crosscuts the related hightemperature hydrothermal systems selective leaching and reconcentration of Bi, As and other elements might have occurred. Sb abundance seems more related to host rocks chemistry, with increase of Ni-Co antimonides and sulfantimonides far from main IZs. Numerous, unexplored IZs may be assumed as a key targets for further mineral exploration in the Arburèse district, where undiscovered ore shoots may be present at depth
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Recovering critical and economic metals (In, Sn, Zn, Cu) from mine waste debris and weathered outcrops in the Zn-Fe skarn belt of the Iglesiente-Sulcis region (SW Sardinia): the case of the historical Perda Niedda mining area
No full textPerda Niedda is a historical, poorly known mining area, close to the Arenas-Tiny mine site near Iglesias
in SW Sardinia. Mineralization at Perda Niedda consists of several Fe-Zn-rich skarn occurrences developed
in the Cambrian Gonnesa limestones over the Oridda monzogranite stock, satellite to the 289 Ma Mt. Linas
pluton. Perda Niedda is actually part of a late-Variscan skarn system stretching across the Iglesiente-Sulcis
region. Recent studies defined the features of the skarn mineralization: magnetite-sphalerite-fluorite-cassiterite
enrichments are associated with retrograde silicate assemblages which deeply replaced prograde skarn facies
dominated by andraditic garnet. Critical metals In and Sn are concentrated in cassiterite and Fe-sphalerite
(with chalcopyrite disease), and also hosted in widespread garnets and magnetite, as revealed by EPMA and
in-situ LA-ICPMS analyses. Twenty samples from several mine dumps and variably mineralized weathered
outcrops were collected to verify the fate of In, Sn and associated metals Zn and Cu during weathering.
Powdered samples were analyzed by XRD, prior to and after acid attack with aqua regia (HCl+HNO3) aimed
at dissolving metals from soluble mineral phases. The resulting solutions were analyzed by Microwave Plasma
Atomic Emission Spectrometer (MP-AES). The XRD analyses provided qualitative evaluation of secondary
minerals, like Fe- (goethite, lepidochrocite-pharmacosiderite) and Mn-Zn-Fe hydroxides (pyrochroite,
chalcophanite), compared to primary minerals (magnetite, cassiterite and andradite) in the starting materials
and residues. The solutions from mineralized gossans and weathered mine dump debris recorded high
Zn (up to 1 wt.%), Cu (up to 0.7 wt.%) and notable In (0.1 wt.%) contents likely released from Fe-Mn-
Zn hydroxide crusts, while the coupled low Sn (280 ppm) might be due to release from magnetite only,
because of cassiterite insolubility. Interesting results derived from analyses of poorly mineralized samples
still preserving abundant prograde andradite, soluble into HCl (https://www.mindat.org/article.php/553/
Solubility+Data+on+646+Common+and+Not+So+Common+Minerals). Their solutions from acid attack
provided remarkable Sn contents, up to 0.26 wt.%, with Zn+Cu (up to 2 wt.%) and In (up to 140 ppm). Such
pilot study suggests various features involving weathering of mineralized skarns and their economic potential.
The first one is the control of the primary minerals in the mobility of valuable metals, in particular In and Sn,
when distributed between soluble (sphalerite-magnetite) and insoluble (cassiterite) phases. The second feature
regards the role of secondary minerals in efficiently capturing metals liberated during weathering, thereby
generating metal-enriched gossans. Last but not least, the role of soluble prograde Ca-garnets acting as initial
reservoirs for metals like Sn and In, directly emanated by the granite magma after emplacement, as well as a
further potential ore mineral
Recycling feldspar wastes as buffer for AMD remediation: preliminary tests on sulfide-rich materials from Sardinia abandoned mines
No full textAcid mine drainage and release of potentially toxic elements are the main source of pollution in sulfiderich
mining sites. In Italy, several regions are affected by environmental pollution caused by the extraction
and processing of sulfide minerals. Several studies have assessed the acidification potential of sulfide mine
wastes, and suggested some procedures to neutralize the acidity and reduce the high metal content of the waters
produced by these materials.
Adding carbonate-based materials, such as lime (Grieco et al., 2021), can neutralize acid mine drainage by
raising pH of water and triggering precipitation of metals as hydroxides at the same time, but the treatment
processes are often expensive in terms of capital and operating costs.
The aim of this research is to test the neutralizing capacity of a carbonate-bearing buffering material derived
from feldspar quarrying in Sardinia.
The Sardinia region has one of the longest mining histories in Italy, and mining dumps are currently causing
environmental pollution (Da Pelo et al., 2009).
Selected samples were collected from Campo Pisano and Furtei abandoned mines. Campo Pisano is part
of a giant and high-grade MVT and SEDEX Zn-Pb-Fe district with variable proportions of Cd-rich sphalerite,
Ag-rich galena and pyrite. The abandoned mine at Furtei exploited an epithermal deposit comprising Cu, Au
and Ag sulfides and sulfosalts + base metal minerals (e.g., pyrite, sphalerite).
Grain size, XRD and XRF were used to characterize the samples. The acidification potential was determined
through ABA tests. Leaching tests simulated the contaminant release from tailings following the Synthetic
Precipitation Leaching Procedure. Leachates were analyzed for major and trace elements through ICP-MS
and were then buffered with waste materials from feldspar quarrying, provided by Minerali Industriali. The
Potential Toxic Element contents of buffered materials was also determined through ICP-MS.
All samples show positive Net Acid Potential Production, with higher values at Campo Pisano. Leaching
tests show very different behavior between the two mines in terms of both acidification and metal contents,
with Furtei showing much lower pH and higher metal contents.
Buffering with feldspar waste was very efficient on highly acidic Furtei samples, even though the amount
of buffered material required is high. At Campo Pisano were leached solutions are near neutral the addition of
buffer has limited impact
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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
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