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L'ATTIVITÀ ESTRATTIVA DEI MINERALI INDUSTRIALI IN ITALIA: IL QUADRO ATTUALE E LA DISPONIBILITÀ GEOLOGICA DELLE RISORSE
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Long term therapy with methylphenidate induces modest effects on growth in ADHD children
No full textThe Jibal Qutman deposit: first notes on a new gold discovery in the Arabian Shield (Kingdom of Saudi Arabia)
No full textThe Jibal Qutman gold deposit (Saudi Arabia) is located in the Asir Terrane (Arabian Shield), a composite
Neoproterozoic terrane that includes volcanic, sedimentary and intrusive rocks. This terrane amalgamated between 780-
640 Ma during the convergence of an oceanic domain interposed between the incoming east and west Gondwana
(Johnson et al., 2011; Flowerdew et al., 2013). The Nabitah-Tathlith fault zone (NTFZ) separates island arc sequences
metamorphosed under greenschist facies, in the west, from paragneiss and amphibolites of the Hajizah Gneiss Belt in
the east. Along the NTFZ, a belt containing over 40 gold deposit occurs (Worl, 1979). Among them, Jibal Qutman
(24°16’N and 45° 04’E), is hosted by lower greenschist metavolcanics and metasediments (Halaban group: 785 Ma).
The first study of the area was performed by the USGS on behalf of the then Directorate General of Mineral Resources
(Hackett, 1983). Recent exploration performed by Kefi Minerals PLC discovered seven Au mineralised zones in a 5 km
long (N-S) and 1 km wide (E-W) area, with estimated 0.733 Moz of gold in indicated and inferred resources.
Mineralisation zones are controlled by low-order structures subparallel to the NTFZ. Orebodies include veins,
stockworks and disseminations, related to step dipping to low angle brittle to ductile shear zones marked by different
stages of hydrothermal alteration and metasomatism. All mineralised zones show definite Au-Ag, Au-Te and (more
locally) Au-Pb geochemical correlations; Au-Ag ratios range from 4:1 to 1:4 on average. The Main Zone orebody is a
900 m-long, N-S quartz vein system, with a single high-angle vein up to 4 m thick that, along strike, splits into multiple
veins. The ore consists of pyrite and minor tetrahedrite, galena and sphalerite with coarse gold. Ore microscopy and
SEM-EDS studies identified a close association between native gold (Au > 85%, Ag 10-15%, traces of Hg), tetrahedrite
(Zn- and Ag-bearing), and Pb and Au tellurides (possible altaite and Hg-bearing calaverite). Pb tellurides are mostly
present as thin rims around tetrahedrite and major gold grains, while Au tellurides occur with gold as small droplets
within tetrahedrite. Milky to sugary quartz is the only gangue mineral. Jibal Qutman shows the features of a shear zonehosted,
mesothermal gold deposit. Different ore styles in the area derived from polyphasic mineralisation related to the
ductile-brittle structural evolution of the NTFZ. From the marked Au-Te geochemical correlations, the Ag abundance,
and the occurrence of tellurides with Sb- and Hg-bearing minerals, a mesozonal- to epizonal orogenic style of
mineralisation (Groves et al., 1998) may be inferred.
Flowerdew M.J., Whitehouse M.J. & Stoeser D.B. 2013 The Nabitah fault zone, Saudi Arabia: A Pan-African suture
separating juvenile oceanic arcs. Precam. Res., 239, 95-105, doi:10.1016/j.precamres.2013.08.004.
Groves D.I., Goldfarb R.J., Gebre-Mariam M., Hagemann S.G. & Robert F. 1998. Ororgenic gold deposits - a proposed
classification in the cvontext of their crustal distribution and relation-ship to other gold deposit types. Ore Geol.
Rev., 13, 7-27.
Hackett D. 1983. The Aflaj oolitic hematite-goethite deposit: Saudi Arabian Directorate General of Mineral Resources,
Jiddah. DGMR Open File Report 04-16.
Johnson P.R., Andresen A., Collins A.S., Fowler A.R., Fritz H., Ghebreab W., Kusky T. & Stern R.J. 2011. Late
Cryogenian-Ediacaran history of the Arabian-Nubian Shield: A review of depositional, plutonic, structural, and
tectonic events in the closing stages of the northern East African Orogen. J. African Earth Sci., 61, 167-232.
Worl R.J. 1979. The Jabal Ishmas-Wadi Tathlith gold belt, Kingdom of Saudi Arabia. U.S. Geol. Surv. Open-File Rep.
79-1519, 108 p
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
From Alpine-type sulfides to nonsulfides in the Gorno Zn project (Bergamo, Italy)
Full text linkRecent exploration of the Gorno Zn-Pb-Ag deposit in northern Italy identified 3.3 Mt of sulfides at 4.9% Zn, 1.3% Pb, and 27.2 g/t Ag (indicated+inferred resources), and a further mineralized nucleus of mixed sulfides-nonsulfides in the Val Vedra area, currently under evaluation. The ores are hosted in Triassic limestone and shale. Sulfides (sphalerite, Ag-bearing galena, minor pyrite, and chalcopyrite) paragenetically follow Mn-Fe-bearing saddle dolomite and sparry calcite. The mineral association, and the carbon and oxygen isotope ratios of the sparry calcite (avg. δ13C = 1.0 ± 0.6‰ V-PDB; avg. δ18O = 19.63 ± 1.25‰ V-SMOW), are in agreement with precipitation from hydrothermal fluids in a deep burial setting. Sulfide emplacement occurred before the Alpine orogeny, likely during the Early-Middle Jurassic, in analogy to other Alpine-type deposits. The nonsulfide ore formed at the expense of sulfides, and mainly consists of smithsonite, hydrozincite, hemimorphite, and cerussite. The C-O-isotope values of the early generations of Zn-carbonates are characterized by δ18O between 24.1 and 26.8‰ V-SMOW and δ13C ratios between − 3.1 and 1.7‰ V-PDB. The later generations have lower δ18O (21.9 to 23.9‰) and lower δ13C (− 6.2 to − 3.9‰). These compositions, as those measured on cerussite (δ13C = −6.3 and − 7.7‰; δ18O = 14.0 and 15.3‰), agree with the formation of the nonsulfides in a supergene environment, under climatic conditions warmer than today. The δ18O decrease from early to late generations suggests progressive involvement of meteoric water sourced from higher altitudes. These characteristics indicate that the nonsulfides formed during the exhumation of the Gorno area from Miocene to Pliocene
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