1,721,035 research outputs found
Mineral chemistry of the calcalkaline lavas from Marsili Seamount (southeast Tyrrhenian Sea): some magmatological and geodynamic considerations
No full textMineral chemistry data from lavas recovered over a large depth interval of the deep-water volcano of Marsili (Aeolian back-arc, SE Tyrrhenian Sea) are presented. The volcano is built up by products of calcalkaline affinity with the only exception of one outcrop of sub-alkaline, within plate basalts in the crestal area. On the whole, the calcalkaline lavas of Marsili have bimodal composition, and consist of basalts and andesites with, respectively, calcalkaline and high-K serial affinity. The andesites mark a change in the geodynamic conditions that is reflected by the clockwise rotation of the seamount rifting from the early NNE-SSE orientation, associated with the extrusion of the basalts, to a dominant tensional regime trending almost NE-SW. This evolution is discussed in the context of some magmatic-structural features in the southest Tyrrhenian volcanic area. -from Author
Calc-alkaline magmatism and rifting of the deep-water volcano of Marsili (Aeolian back-arc, Tyrrhenian Sea)
No full textGeochemistry and mineral chemistry data indicate that new lava samples recovered from a large depth interval of Marsili volcano (southern Tyrrhenian Sea) are calc-alkaline. The deep to intermediate portions of the volcano are made up by calc-alkaline basalts, whereas the summit consists of high-potassium calc-alkaline andesites. The contents of MgO, CaO, total iron, Cr, Ni and V decrease with increasing silica, while K2O, Rb, Ba, Th, Nb and LREE exhibit the opposite behavior. The andesite lavas of the top, at waterdepth shallower than about 800 m, are younger than 0.2 Ma. Composition of the basalts varies with the waterdepth; overall, the deepest products of Marsili are geochemically more mafic than those erupted in the higher physiographic positions. Geochemical features suggest the existence of a mantle source that was modified by metasomatic acquirement of subduction-derived incompatible elements. The seamount lies on oceanic crust which formed above subducting lithosphere not earlier than about 2 Ma ago. It is currently undergoing extension along linear faults. The major distensional fractures trend N-S to N15°E paralleling the physiographic elongation of the volcano. At the summit, later faults have an oblique NE-SW orientation which is associated with the eruption of high-potassium andesites. The transition from basalts to high-potassium andesites is discussed as a possible response to the extension and rapid subsidence that dominate the volcano and surrounding region. © 1994
La Roccaccia di Selvena (Castell’Azzara – GR): relazione della campagna 2000 e revisione dei dati delle precedenti
No full textcura dell'articolo con testi di E. Baldi, T. Cavallo, F. Cavanna, C. Citter, L. Giustarini, S. Giustarini, S. Menci, H. Salvadori, S. Savelli, C. Valdambrini, S. Zuccherin
Oligo-Miocene Magmatism and Geodynamics in the Central and Western Mediterranean Region.
No full textGuanidine-guanidinium cooperation in bifunctional artificial phosphodiesterases based on diphenylmethane spacers; Gem -dialkyl effect on catalytic efficiency
No full textDiphenylmethane derivatives 1-3, decorated with two guanidine units, are effective catalysts of HPNP transesterification. Substitution of the methylene group of the parent diphenylmethane spacer with cyclohexylidene and adamantylidene moieties enhances catalytic efficency, with gem-dialkyl effect accelerations of 4.5 and 9.1, respectively. Activation parameters and DFT calculations of the rotational barriers around the C-Ar bonds indicate that a major contribution to the driving force for enhanced catalysis is entropic in nature
Mixed function oxidase induction in Carcinus aestuarii. Field and experimental studies for the evaluation of toxicological risk due to Mediterranean contaminants
No full textThe aim of this study was to test and validate the use of mixed function oxidase (MFO) induction, in the crab Carcinus aestuarii, under experimental and field studies, for the evaluation of toxicological risk due to the main contaminants in the Mediterranean. Two different experiments were performed in the laboratory in order to identify the most suitable tissues for MFO studies in this species and the most suitable and sensitive MFO responses for evaluating chemical stress due to lipophilic contaminants. In order to validate this methodology in the field, two studies were carried out in two polluted Mediterranean lagoons: a transplant experiment in Orbetello Lagoon and an in situ experiment in Venice Lagoon. The following MFO responses were investigated in hepatopancres and gills of the crabs: ethoxyresorufin-O-deethylase (EROD) and benzo(alpha)pyrene hydroxylase (BPH) activities and reductase enzyme activities. The main results can be summarised as follows: midgut-gland and gills were confirmed to be useful for MFO tests; BPH activity in hepatopancreas was the most suitable and sensitive MFO response for evaluating chemical stress due to Mediterranean contaminants in laboratory and field studies; in the Orbetello Lagoon experiment, a statistically significant difference was found between sites subject to different human impact
Western Mediterranean Geodynamics: a look for the period of westward subduction initiation.
No full text
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
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