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showing 10 items of 61 documents
Distorted f.c.c. arrangement of gold nanoclusters: a model of spherical particles with microstrains and stacking faults
2008
The structures of two samples of gold nanoclusters supported on silica were studied by X-ray powder diffraction (XRD) and X-ray absorption spectroscopy. The data relative to both techniques were analysed by an approach involving simulation based on structural models and fitting. The XRD model concerned a distorted f.c.c. (face-centred cubic) arrangement, with microstrains and parallel stacking faults in approximately spherical particles; as an alternative possibility, a linear combination of ordered f.c.c. and noncrystalline (decahedral and icosahedral) particles was also taken into account. Both approaches gave calculated patterns closely resembling the experimental data. X-ray absorption …
Transtensional/extensional fault activity from the Mesozoic rifting to Tertiary chain building in Northern Sicily (Central Mediterranean)
2005
Extensional structures of different ages characterize the Sicilian fold-and-thrust belt. Normal faults ranging in geometry from stepped to listric and formed in different geodynamic settings significantly controlled the pattern of syn-tectonic deposits. Since Mesozoic times Sicily has experienced deformation related to the opening of the Tethys Ocean. Between the Upper Triassic and the Cretaceous normal, strike- and oblique-slip faults, developed in northern Sicily, in the framework of a transtensional deformation regime induced by the oblique rifting of the African and European continental passive margins. Since Tertiary times a reversal in the general relative plate motion induced converg…
Optical characterization of Mg-doped GaN films grown by metalorganic chemical vapor phase deposition
2000
Scanning electron microscopy, micro-Raman, and photoluminescence (PL) measurements are reported for Mg-doped GaN films grown on (0001) sapphire substrates by low-pressure metalorganic chemical vapor phase deposition. The surface morphology, structural, and optical properties of GaN samples with Mg concentrations ranging from 1019 to 1021 cm−3 have been studied. In the scanning micrographs large triangular pyramids are observed, probably due to stacking fault formation and three-dimensional growth. The density and size of these structures increase with the amount of magnesium incorporated in the samples. In the photoluminescence spectra, intense lines were found at 3.36 and 3.31 eV on the tr…
Understanding paleomagnetic rotations in Sicily: thrust vs. strike-slipe tectonics
2018
The paleomagnetic investigation of the western Sicily Maghrebian belt has revealed since the 1970s that large clockwise (CW) rotations up to 140° with respect to the Hyblean-African foreland occurred synchronous with Tertiary shortening of the chain. The observation that rotations decrease stepwise from internal to external tectono-stratigraphic units led in the 1990s to a widely accepted model postulating that rotational thrust-sheet emplaced during forward orogenic propagation. More recently, other authors suggested that CW rotations from Sicily are conversely the result of late orogenic dextral strike-slip tectonics. Here we report on a paleomagnetic investigation of 30 Jurassic-Eocene s…
PRIN Project 2010-11 “Active and recent geodynamics of Calabrian Arc and accretionary complex in the Ionian Sea”: new constraints from geological, ge…
2014
This contribution illustrates the preliminary results of our Research Unit in the PRIN Project 2010-11, which focuses on active and recent geodynamics of Calabrian Arc. The integration of the new geological, geodetic and seismological data supports the inferred recent plate boundary reorganization in the central-southern Mediterranean, where the regional GNNS velocity fields point to a deceleration or cessation of Calabrian Arc migration, and to extension along the axis of the Calabrian Arc, accommodated by normal faulting (e.g. Capo Vaticano and Messina Straits (Aloisi et al., 2012; Pepe et al., 2014; Spampinato et al., 2014). The study of the lateral borders of the Arc revealed that obliq…
On the relationships between tectonics and volcanism in the offshore capo vaticano, se tyrrhenian sea, during the plio-pleistocene.
2014
High-resolution bathymetry and a grid of single-channel reflection seismic profiles (Sparker and Chirp) were recently recorded in a sector of the upper slope of Capo Vaticano (CV) promontory (Tyrrhenian coast, W Calabria) where forward and inverse modeling of previously acquired aeromagnetic data highlight the presence of a WNW©\ESE elongated, 20 km long and 3¨C5 km wide, magnetized body extending from sea floor to about 3 km below sea level. Magnetic properties of this body are consistent with those of the medium to highly evolved volcanic rocks of the Aeolian Arc (De Ritis et al., 2010). Forthwith offshore promontory, the bathymetry highlights a complex-shape seamount that develops along …
Understanding paleomagnetic rotations in Sicily: Thrust vs. transpressive structures
2016
Since the 1970s, paleomagnetic data collected in Sicily have documented large magnitude clockwise (CW) rotations around vertical axis with respect to Africa and the Hyblean foreland. Many Authors argued that rotations arise from rotational thrusting of large coherent nappes coinciding with paleogeographic units. In the forward thrust propagation process, each nappe rotates the overlying nappe stack. This would explain the stepwise decrease of rotation magnitudes from the internal Panormide unit (90°-140°) to the external Saccense unit, yielding no rotation. However, other Authors later proposed that rotations of Sicily are the consequence of dextral shear occurring since late Miocene times …
Architecture and kinematics of forearc basins and intra-caldera resurgences: new insight from the Paola Basin (western offshore Calabria region) and …
This thesis deals with the patterns of tectonic deformation at different time and spatial scales ranging from tens to millions of years and from one to tens of kilometers, respectively. The study areas are the Campi Flegrei (Campania region, Italy) and Paola Basin (western offshore Calabria region, Italy). The Campi Flegrei and its offshore prolongation, the Pozzuoli Bay, are a laboratory for investigating volcano-tectonic deformations at 1yr-1kyr timescale and 1km spatial scale related to the dynamics of the Neapolitan Yellow Tuff (NYT) caldera and its intra-caldera resurgence. Resurgence is the late stage, long-term uplift of a collapse caldera floor to form a dome-like structure. The com…
Neotectonic uplift and tilting of crustal blocks in Northern Sicily
2009
La Sicilia settentrionale è caratterizzata da un’intensa attività sismica che è espressione di deformazioni attive. In questo settore dell’Isola affiora il nucleo della catena neogenica delle Magrebidi occidentali, che è sottoposto ad intenso sollevamento durante il Plio-Pleistocene. Le deformazioni più recenti sono, in gran parte, rappresentate da sistemi di faglie estensionali e trascorrenti. Il tasso di sollevamento non è uniforme, così come suggerisce la differente elevazione dei depositi di questo periodo. Essi affiorano lungo il settore costiero settentrionale e la loro quota decresce complessivamente dall’estremità nord-est a quella nord-ovest della Sicilia. Le deformazioni più recen…