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81.
Giorgio?RivalentiEmail author Alberto?Zanetti Maurizio?Mazzucchelli Riccardo?Vannucci Carlos?A.?Cingolani 《Contributions to Mineralogy and Petrology》2004,147(6):647-670
Amphibole ± phlogopite ± apatite-bearing mantle xenoliths at Gobernador Gregores display modal, bulk-rock and phase geochemical characteristics held as indicators of carbonatitic metasomatism. However, part of these xenoliths has high TiO2/Al2O3 and those displaying the most pronounced carbonatitic geochemical markers modally trend towards harzburgite. Bulk-rock, clinopyroxene and amphibole show Zr, Hf and Ti negative anomalies, which increase at decreasing Na2O and high field strength elements (HFSE) concentrations. Steady variation trends between xenoliths which have and do not have carbonatitic characteristics suggest a control by reactive porous flow of only one agent, inferred to be initially a ne-normative hydrous basalt (because of the presence of wehrlites) evolving towards silica saturation. Variation trends exhibit cusps when amphibole appears in the mode. Appearance of amphibole may explain the Ti anomaly variations, but not those of Zr and Hf. Numerical modelling [Plate Model (Vernières et al. in J Geophys Res 102:24771–24784, 1997)] gives results consistent with the observed geochemical features by assuming the presence of loveringite. Modest HFSE anomalies in the infiltrating melt may be acquired during percolation in the garnet-facies.In memory of Carlo Rivalenti 相似文献
82.
Stefano Schiaparelli Michela Castellano Paolo Povero Gianfranco Sartoni & Riccardo Cattaneo-Vietti 《Marine Ecology》2007,28(3):341-353
In this contribution we document an anomalous mucilage growth which occurred in June 2003 along the rocky cliffs of the Portofino Promontory (Ligurian Sea, NW Mediterranean Sea), and we describe its dynamics and its negative effects on many benthic taxa. The zooxanthellate scleractinian Cladocora caespitosa underwent ‘bleaching’ and about 40% of biomass of the erect algae was detached by mucilage ‘lianas’ created and strengthened by bottom currents. The 2003 event differed from any other previously occurred in the northern Tyrrhenian Sea, in that the mucilage aggregates were formed by the free‐living form of the Phaeophyceae Acinetospora crinita (Harvey) Kornmann, a not usually dominant species in mucilage aggregates from the north Tyrrhenian Sea. The damage suffered by the benthic organisms living in this area was curtailed by a severe storm, occurred in July, which removed the mucilage to deeper depths, preventing irreversible damages. Only slow growing, perennant organisms, such as corallinales or scleractinians, were seriously affected, but a survey carried out 1 year later, in June 2004, allowed to appreciate a complete recovery of those organisms. This anomalous mucilage event occurred in coincidence of the 2003 European heatwave, and the anomalous temperature increase of seawater has to be regarded as the major contributing event that led to the mucilage outbreak. 相似文献
83.
Stefano Schiaparelli Giancarlo Albertelli & Riccardo Cattaneo-Vietti 《Marine Ecology》2006,27(1):44-53
Some organisms represent useful Biological Sea‐Level Indicators (Bio SLI) thanks to their constant position relative to sea level and allow the reconstruction of past sea level changes. The sessile gastropods Vermetidae are among the most used indicators, since their shells often resist time averaging and can be easily dated with 14C. However, all these vermetids have a level of precision (± 0.5–1 m), obtained from data on the Mediterranean Dendropoma petraeum (Monterosato, 1884). We found a certain degree of plasticity in this species; it can also live subtidally, not in correspondence with the main sea level, where it feeds adopting a mixed feeding strategy. Considering this variability and the almost complete lack of knowledge for other Bio SLI vermetids, it appears clear that a common value of precision cannot be maintained and the precision of other vermetid species remains to be tested. 相似文献
84.
A new methodology for computing the gravitational effect of a spherical tesseroid has been devised and implemented. The methodology is based on the rotation from the global Earth-Centred Rotational reference frame to the local Earth-Centred P-Rotational reference frame, referred to the computation point P, and it requires knowledge of the height and the angular extension of each topographic column. After rotation, the gravitational effect of the tesseroid is computed via the effect of a sector of the spherical zonal band. In this respect, two possible procedures for handling the rotated tesseroids have been proposed and tested. The results obtained with the devised methodology are in good agreement with those derived by applying other existing methodologies. 相似文献
85.
Riccardo Cattaneo-Vietti Giancarlo Albertelli Giorgio Bavestrello Carlo Nike Bianchi Carlo Cerrano Mariachiara Chiantore Laura Gaggero Carla Morri Stefano Schiaparelli 《Marine Ecology》2002,23(S1):65-77
Abstract. Biomineralogy, as the complex of interactions at different levels (cell, organism, species, and community) between organisms and minerals, may play a significant role in the spatial distribution and structure of marine communities. For instance, a negative influence of quartz has been underlined on the Mediterranean benthic communities, which show a species-poorer structure in quartz-rich environments. Excluding the role of quartz, the aim of this work is to verify whether the composition of various mineralogical substrata can affect a hard-bottom benthic community. In the Ligurian Sea, the Levanto area shows an astonishing complex of substrata with different petrographic characters: in a few kilometres, sandstones, serpentinites, gabbros, and basalts occur in geometric association. Consequently, this area represents a suitable frame for this type of study. Herein, algal photophilic assemblages growing on the four mineralogical substrata show significant differences in number of species and percentage cover or abundance. This suggests a significant influence of rock mineral composition on the hard bottom community. Therefore, rock composition must be taken into account for a better understanding of the processes at the basis of hard-bottom community development and diversity. 相似文献
86.
Riccardo Briganti Giorgio Bellotti Leopoldo Franco Julien De Rouck Jimmy Geeraerts 《Coastal Engineering》2005,52(12):351-1174
This paper describes a new station for full-scale measurement of wave overtopping at the Rome yacht harbour rubble mound breakwater in Ostia (Italy) and the results of the successful first measurement campaign carried out during the winter season 2003–2004. The equipment and the research activities were supported by the EU project CLASH, focusing on scale effects for wave overtopping at coastal structures. The site is characterized by a very small tidal range, a long shallow foreshore and depth-limited breaking waves which interact with a shallow sloping porous rock structure. Overtopping water is collected by a steel tank installed on the crown slab behind the parapet wall. The measurement of water level variation inside the tank by means of two pressure transducers allows the calculation of individual overtopping volumes. Incident waves, sea levels and wind are also measured. During seven independent storms, more than 400 individual overtopping events were recorded and about 86 h of valid data are available. This extensive dataset is presented, discussed and then used for comparison with two commonly used overtopping prediction formulae based on small-scale model tests showing their tendency to underestimate the prototype results. A strong correlation between the hourly mean overtopping discharge and corresponding maximum volume is also presented. The paper generally confirms the validity of the approach used in Troch et al. (2004) [Troch, P., Geeraets, J., Van de Walle, B., De Rouck, J., Van Damme, L., Allsop, W., Franco, L., 2004. Full-scale wave overtopping measurements on the Zeebrugge rubble mound breakwater. Coastal Engineering 51, 609–628] for field measurement of wave overtopping. 相似文献
87.
Remnants of a fossil continent–ocean transition similar to that of the modern non-volcanic continental margins are preserved in the Jurassic External Liguride units. They consist of fertile lherzolites of subcontinental origin, MOR-type basalts and rare gabbroic intrusives, together with continental crust bodies exhumed during the rifting phases preceding the oceanization. The gabbroic rocks include troctolites, (olivine) gabbros, Fe–Ti oxide-bearing gabbros and diorites. Trace element and Nd isotope compositions indicate that these rocks were derived from N-MORB melts variably evolved through fractional crystallisation. In the gabbroic rocks, high-temperature ( 900 °C) shearing along ductile shear zones is locally overprinted by amphibolite-facies recrystallization (T 650 °C), which was most likely assisted by seawater-derived fluids. Basalts crop out as lava flows and as dykes crosscutting mantle lherzolites and gabbroic rocks. They display nearly flat REE patterns and high Y/Nb values (5–14), similar to modern N-MORB. Basalts are also characterised by weak Zr enrichment relative to neighbouring REE (Zr/Zr = 1.1–1.7) and high (Sm/Yb)DM ratios (1.5–1.8). Their Nd isotope compositions are close to typical depleted mantle (initial Nd = +7.6 to + 9.4). The geochemical features of parental melts of basaltic and gabbroic rocks may be attributed to melting of a MORB-type asthenospheric source. Trace element modelling shows that low-degree (≤ 6%) fractional melting of a depleted spinel peridotite cannot account for the elevated Sm/Yb ratios of basalts. Low-degree melting of a mixed source of spinel peridotite with small amounts of garnet pyroxenite has been proposed to explain the trace element signature of basalts. 相似文献
88.
Atlantic forcing of Pacific decadal variability 总被引:1,自引:0,他引:1
89.
90.
Riccardo Tortini Fabio L. Bonali Claudia Corazzato Simon A. Carn Alessandro Tibaldi 《地学学报》2014,26(4):273-281
Measuring surface deformation is critical in analogue modelling of Earth science phenomena. Here, we present a novel application of the Microsoft Kinect sensor to measure vertical deformation in a scaled analogue model of Nisyros volcano (Greece), simulating two magmatic sources and related surface deformation. The Kinect permits capture of real time, 640 × 480 pixel, true‐colour images (RGB) and a grid of distances to the modelled surface with a horizontal and vertical resolution of ±1 mm. Using recorded distances permits quantification of vertical deformation in terms of maximum and average down‐ and uplift during deflation and inflation phases respectively, which is of crucial importance for defining the kinematics of faults formed during the modelling, determined from interpretation of the RGB images. Although other techniques have demonstrated similar or higher accuracy, our study demonstrates the cost‐effectiveness of the Kinect in analogue modelling of volcanoes. 相似文献