150 research outputs found
Magmatic Processes at Euganean Hills (Veneto Volcanic Province, Italy): Clinopyroxene Investigation to Unravel Magmatic Interactions
No full textThe Euganean Hills (NE Italy) magmatic district represents the final volcanic activity of the Veneto Volcanic Province. Alkaline to subalkaline magmatic suite dominated by intermediate to felsic volcanic rocks characterises the latest volcanic activity of the Euganean Hills. Magmatic (intrusive and volcanic) enclaves are common in Euganean Hills trachytes. We used the ability of clinopyroxene to record variations of P, T, and fO2 to reconstruct the geological history of the volcanic enclaves and trachytic host. Despite similar major and trace elements composition, clinopyroxene from host is higher in Ca and Na (and Fe3+) and lower in Mg than enclaves and is slightly enriched in trace elements but with the same pattern distribution. Minor differences in geochemistry and crystal structure of clinopyroxene from enclaves and trachytic host suggest similar parental magmas that differs by small degrees of fractional crystallisation. Clinopyroxene geobarometry performed combining X-ray diffraction with mineral geochemistry for volcanic enclaves–trachytic host combined with amphibole geobarometry for intrusive enclaves and crystal mushes points to a crystallisation pressure range between 4.8–2.0 kbars. Our data support the model of a complex system of magma chambers at intermediate to shallow crustal level where mafic magma accumulated, evolved by fractionation processes and mixed
Degassing behaviour at basaltic volcanoes: New insights from experimental investigations of different conduit geometry and magma viscosity
No full textUnderstanding gas-magma dynamics in volcanic conduits and linking them with the associated geophysical signals at the surface is of fundamental importance in monitoring active volcanoes. In the past, a significant number of studies have been devoted to this topic, addressing the onset, the key factors governing each degassing regime and the related markers at the surface, particularly at basaltic volcanoes. Here, we first review such a broad and increasing literature, focusing on the main approaches used in the attempt of deciphering conduit dynamics by indirect observations: 1) analogue laboratory experiments; and 2) seismo-acoustic measurements. Then, we combine the two techniques into a novel set of experiments, addressing a crucial, yet unexplored, issue: the irregularity (i.e. the departure from an ideal smooth cylindrical shape) of the conduit surface. We built a set of epoxy conduits with various fractal dimensions (D c ; i.e. irregularity) of the internal surface, using silicone oil as a proxy for magma. Different degassing patterns (bubbly, slug and churn-annular flow) were reproduced by changing systematically: 1) injected gas flux (5 to 180 × 10 −3 l/s); 2) analogue magma viscosity (10 to 1000 Pas); 3) fractal dimension (D c ) of the conduit surface (i.e. D c = 2, D c = 2.18 and D c = 2.99). The experiments were monitored by means of a video-camera and a set of sensor aimed to detect the seismic and acoustic signals. Results show that viscosity strongly influences the transition among degassing patterns and the recurrence rate of slug bursts at the surface. Moreover, we observed an increase of the exponent of the power law equation linking squared seismic amplitude to gas flow rate with conduit roughness; the opposite trend was noticed with increasing liquid viscosity. These results have important implications for linking seismic tremor to eruption source parameters such as the volume discharge rate at different volcanoes or for investigating its temporal evolution at a single vent
ILCatalogo: a digital archive for theatre cultural heritage
No full textIn this article the final results of the research project "Digital archive of the artistic heritage of Emanuele Luzzati: the
theatre" will be presented. The project, lasting two years, was funded under the Convention between the Region of
Liguria and ILC-CNR for “Higher education projects Operational Programme (OP) Regional Competitiveness and
Employment (CRO) European Social Fund (ESF) 2007-2013 Liguria Region axis IV Human Capital Specific Objective I /
6” and it ended on April 30th, 2015. The main theme of the research was on the structuring, integration, accessibility and
maintenance of archives and the scope of intervention is related to cultural heritage
Experimental magma mixing between rhyolitic and basaltic melts: implications for the Bruneau-Jarbidge magmatism, Snake River Plain (USA)
No full textInterdiffusion of major elements at 1 atmosphere between natural shoshonitic and rhyolitic melts
No full textRheological evolution of eruptible Basaltic-Andesite Magmas under dynamic conditions: The importance of plagioclase growth rates
No full textThe effects of crystal nucleation and growth on the viscosity of andesitic magmas are investigated at 1 atm. Pressure. The data are used to describe the rheological evolution of andesitic magmas and to derive empirical equations to model the crystallization dynamics. Viscosity experiments were performed at temperatures of 1473, 1483, and 1493 K with shear rates of 0.5 s−1 by using wide-gap concentric cylinder viscometry. We focused on eruptible magmas (i.e., crystal contents well-below ~50%) by following the time evolution of crystal nucleation and growth of a natural andesitic magma, while continuously monitoring the changes in viscosity. At near-equilibrium conditions, the basaltic-andesite contains 6, 13, and 25 area % crystals at 1493, 1483, and 1473 K, respectively, resulting in a viscosity increase of ca. 1 log unit. We show that the timescale of viscosity increase is mainly dictated by the delay time preceding crystallization and markedly decreases with increasing undercooling (from 22 to 42 K) and shear rates (from 0.1 to 1 s−1). The plagioclase growth rates estimated from our data are in the order of ~3–5 × 10−6 cm/s, which is much faster than the rates estimated for crystallization in static conditions. We conclude that the effect of the shear rate must be taken into account in modelling magmatic and volcanic processes, especially when transient changes in viscosity need to be estimated. Our results are important for understanding the dynamics of lava flows where deformation plays a significant role in promoting crystallization
Assimilation of rhyolitic magma by basaltic recharge in the Bruneau-Jarbidge eruptive center, Snake River Plain (USA)
No full textLanguage, communication and society: a gender based linguistics analysis
No full textThe purpose of this study is to find evidence for
supporting the hypothesis that language is the mirror of our thinking,
our prejudices and cultural stereotypes. In this analysis, a
questionnaire was administered to 537 people. The answers have
been analysed to see if gender stereotypes were present such as the
attribution of psychological and behavioural characteristics.
In particular, the aim was to identify, if any, what are the
stereotyped images, which emerge in defining the roles of men and
women in modern society. Moreover, the results given can be a good
starting point to understand if gender stereotypes, and the
expectations they produce, can result in penalization or inequality. If
so, the language and its use would create inherently a gender bias,
which influences evaluations both in work settings both in everyday
life
Morphochemistry of patterns produced by mixing of rhyolitic and basaltic melts
No full textIn this work we present the results of time series experiments performed by mixing basaltic and rhyolitic melts at high temperature using a device recently developed to trigger chaotic dynamics in a mixing system. The morphology of mixing patterns is quantified at different times by measuring their fractal dimension and a linear relationship is derived between mixing time and morphological complexity. The complexity of mixing patterns is also compared to the degree of homogenization of chemical elements during mixing and empirical relationships are established between the fractal dimension and the temporal variation of concentration variance of elements.
New concepts and tools to study the magma mixing process unfold from the experimental results presented in this work. The first one is that the mixing patterns are fractals and they can be quantified by measuring their fractal dimension. This represents a further step in the quantification of the magma mixing process. The second outcome is that the relationship between the fractal dimension of the mixing patterns and mixing time is linear. This has important volcanological implications as the analyses of the morphology of mixing patterns in volcanic rocks can be complemented by experiments to build a new chronometer to estimate the mixing-to-eruption time. A further result from this work is the relationship between the fractal dimension of mixing patterns and concentration variance of chemical elements. This represents the first morphochemical study in igneous petrology bringing with it the potential to infer the relative mobility of chemical elements during the time progression of mixing by analyzing the morphology of mixing patterns in the rocks
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