Post-seismic relaxation and earthquake triggering in the southern Adriatic region   总被引：1，自引：0，他引：1  

Marcello Viti  Francesca D'Onza  Enzo Mantovani  Dario Albarello  Nicola Cenni 《Geophysical Journal International》2003,153(3):645-657

  相似文献   

Layered amphibolite sequence in NE Sardinia,Italy: remnant of a pre-Variscan mafic silicic layered intrusion?     

Marcello?FranceschelliEmail author  Mariano?Puxeddu  Gabriele?Cruciani  Andrea?Dini  Marilisa?Loi 《Contributions to Mineralogy and Petrology》2005,149(2):164-180

A banded amphibolite sequence of alternating ultramafic, mafic (amphibolite) and silicic layers, tectonically enclosed within Variscan migmatites, outcrops at Monte Plebi (NE Sardinia) and shows similarities with leptyno-amphibolite complexes. The ultramafic layers consist of amphibole (75–98%), garnet (0–20%), opaque minerals (1–5%) and biotite (0–3%). The mafic rocks are made up of amphibole (65–80%), plagioclase (15–30%), quartz (0–15%), opaque minerals (2–3%) and biotite (0–2%). The silicic layers consist of plagioclase (60–75%), amphibole (15–30%) and quartz (10–15%). Alteration, metasomatic, metamorphic and hydrothermal processes did not significantly modify the original protolith chemistry, as proved by a lack of K₂O-enrichment, Rb-enrichment, CaO-depletion, MgO-depletion and by no shift in the rare earth element (REE) patterns. Field, geochemical and isotopic data suggest that ultramafic, mafic and silicic layers represent repeated sequences of cumulates, basic and acidic rocks similar to macrorhythmic units of mafic silicic layered intrusions. The ultramafic layers recall the evolved cumulates of Skaergaard and Pleasant Bay mafic silicic layered intrusions. Mafic layers resemble Thingmuli tholeiites and chilled Pleasant Bay mafic rocks. Silicic layers with Na₂O: 4–6 wt%, SiO₂: 67–71 wt% were likely oligoclase-rich adcumulates common in many mafic silicic layered intrusions. Some amphibolite showing a strong Ti-, P-depletion and REE-depletion are interpreted as early cumulates nearly devoid of ilmenite and phosphates. All Monte Plebi rocks have extremely low Nb, Ta, Zr, Hf content and high LILE/HFSE ratios, a feature inherited from the original mantle sources. The mafic and ultramafic layers show slight and strong LREE enrichment respectively. Most mafic layer samples plot in the field of continental tholeiites in the TiO₂–K₂O–P₂O₅ diagram and are completely different from N-MORB, E-MORB and T-MORB as regards REE patterns and Nd, Sr isotope ratios but show analogies with Siberian, Deccan and proto-Atlantic rift tholeiites. Comparisons with Thingmuli, Skaergaard and Kiglapait rocks and with experimental data suggest that the Monte Plebi intrusion was an open-to-oxygen system with fO₂ FMQ. Mafic and ultramafic samples yielded _Nd(460)=+0.79 /+3.06 and ⁸⁷Sr/⁸⁶Sr=0.702934–0.703426, and four silicic samples _Nd(460)=–0.53/–1.13; ⁸⁷Sr/⁸⁶Sr=0.703239–0.703653. Significant differences in Nd isotope ratios between mafic and silicic rocks prove that both groups evolved separately in deeper magma chambers, from different mantle sources, with negligible interaction with crustal material, and were later repeatedly injected within a shallower magma chamber. The spectrum of Sr and Nd isotope data is consistent with a slightly enriched mantle metasomatized during an event earlier than 460 Ma. The metasomatising component was represented by alkali-Th-rich fluids of crustal origin rather than by sedimentary materials, able to modify alkali and Sr–Nd isotope systematics. Monte Plebi layered amphibolites might represent the first example of a strongly metamorphosed fragment of an early Paleozoic mafic silicic layered intrusion emplaced in a thinning continental crust and then tectonically dismembered by Variscan orogeny.  相似文献   

Carbonate pseudotachylytes: evidence for seismic faulting along carbonate faults     

Alfio Viganò  Simone Tumiati  Sandro Recchia  Silvana Martin  Marcello Marelli  Riccardo Rigon 《地学学报》2011,23(3):187-194

  相似文献   

The Growth of the Planetary Boundary Layer at a Coastal Site: a Case Study   总被引：2，自引：1，他引：1  

Ferdinando De Tomasi  M. Marcello Miglietta  M. Rita Perrone 《Boundary-Layer Meteorology》2011,139(3):521-541

A lidar system is used to determine the diurnal evolution of the planetary boundary layer (PBL) height on a summer day characterized by anticyclonic conditions. The site is located some 15 km distant from the sea, on a peninsula in south-east Italy. Contrary to expectations, the PBL height, after an initial growth consequent to sunrise, ceases to increase about 2 h before noon and then decreases and stabilizes in the afternoon. An interpretation of such anomalous behaviour is provided in terms of trajectories of air parcels towards the lidar site, which are influenced by the sea breeze, leading to a transition from a continental boundary layer to a coastal internal boundary layer. The results are analyzed using mesoscale numerical model simulations and a simple model that allows for a more direct interpretation of experimental results.  相似文献   

Global and regional ocean carbon uptake and climate change: sensitivity to a substantial mitigation scenario   总被引：1，自引：0，他引：1  

Marcello Vichi  Elisa Manzini  Pier Giuseppe Fogli  Andrea Alessandri  Lavinia Patara  Enrico Scoccimarro  Simona Masina  Antonio Navarra 《Climate Dynamics》2011,37(9-10):1929-1947

Under future scenarios of business-as-usual emissions, the ocean storage of anthropogenic carbon is anticipated to decrease because of ocean chemistry constraints and positive feedbacks in the carbon-climate dynamics, whereas it is still unknown how the oceanic carbon cycle will respond to more substantial mitigation scenarios. To evaluate the natural system response to prescribed atmospheric ??target?? concentrations and assess the response of the ocean carbon pool to these values, 2 centennial projection simulations have been performed with an Earth System Model that includes a fully coupled carbon cycle, forced in one case with a mitigation scenario and the other with the SRES A1B scenario. End of century ocean uptake with the mitigation scenario is projected to return to the same magnitude of carbon fluxes as simulated in 1960 in the Pacific Ocean and to lower values in the Atlantic. With A1B, the major ocean basins are instead projected to decrease the capacity for carbon uptake globally as found with simpler carbon cycle models, while at the regional level the response is contrasting. The model indicates that the equatorial Pacific may increase the carbon uptake rates in both scenarios, owing to enhancement of the biological carbon pump evidenced by an increase in Net Community Production (NCP) following changes in the subsurface equatorial circulation and enhanced iron availability from extratropical regions. NCP is a proxy of the bulk organic carbon made available to the higher trophic levels and potentially exportable from the surface layers. The model results indicate that, besides the localized increase in the equatorial Pacific, the NCP of lower trophic levels in the northern Pacific and Atlantic oceans is projected to be halved with respect to the current climate under a substantial mitigation scenario at the end of the twenty-first century. It is thus suggested that changes due to cumulative carbon emissions up to present and the projected concentration pathways of aerosol in the next decades control the evolution of surface ocean biogeochemistry in the second half of this century more than the specific pathways of atmospheric CO₂ concentrations.  相似文献   

Asteroids 2001, from Piazzi to the 3rd Millennium     

Marcello Fulchignoni 《Icarus》2002,159(2):269-270

  相似文献   

Dynamics of mineral crystallization from precipitated slab-derived fluid phase: first in situ synchrotron X-ray measurements     

Nadia Malaspina  Matteo Alvaro  Marcello Campione  Heribert Wilhelm  Fabrizio Nestola 《Contributions to Mineralogy and Petrology》2015,169(3):1-12

  相似文献   

Detection of detached forced-regressive nearshore wedges: a case study from the central-southern Siena Basin (Northern Apennines, Italy)     

Ivan Martini  Simone Arragoni  Mauro Aldinucci  Luca Maria Foresi  Anna Maria Bambini  Fabio Sandrelli 《International Journal of Earth Sciences》2013,102(5):1467-1489

The detection of detached nearshore wedges formed in response to relative sea-level drops is considered one of the hottest topics in sequence stratigraphic analysis due to their importance as reservoir analogues. In fact, they usually constitute sandy and porous bodies generally encased in impermeable clay, thus presenting a good potential as traps for fluids. This paper focuses on the sequence stratigraphic analysis of the Pliocene deposits cropping out in the central-southern sector of the Siena Basin (Tuscany, Italy), a post-collisional basin of the Northern Apennines. The exposed sedimentary succession was investigated through a detailed sedimentological and stratigraphic approach, integrated by biostratigraphic analyses, aimed at a better characterization of the infilling history of this sector of the basin. Specifically, this study revealed the occurrence of repeated facies shifts that allowed the identification of two depositional sequences. In detail, a thick sand-rich body far from the basin margins, and previously considered as a turbiditic lobe, has been reinterpreted as formed in a nearshore setting during a fall in relative sea level. This body is totally encased in offshore clay, and due to the lack of physical connection with the related HST deposits, it has to be considered as a detached forced-regressive wedge. The present work led to the recognition of some sedimentological and stratigraphic features typical of falling stage systems tract deposits (e.g. presence of intrabasinal recycled materials, sedimentological evidence of a pre-existing fluvial network subsequently eroded) that can provide useful clues for the identification of detached forced-regressive nearshore wedges in core studies and poorly exposed settings.  相似文献   

Key barriers to community cohesion: views from residents of 20 London deprived neighbourhoods     

Marcello Bertotti  Faye Adams-Eaton  Kevin Sheridan  Adrian Renton 《GeoJournal》2012,77(2):223-234

The notion of community has been central to the political project of renewal of New Labour in the UK. The paper explores how the discourses of community are framed within New Labour and discusses these in the light of the results from research which focuses on how people within urban deprived areas construct their community. It draws upon the results of one part of a larger research project (the ‘Well London’ programme) which aimed to capture the views of residents from 20 disadvantaged neighbourhoods throughout London using an innovative qualitative method known as the ‘World Café’. Our results show the centrality of young people to the development of cohesive communities, the importance of building informal relationships between residents alongside encouraging greater participation to policy making, and the need to see these places as fragile and temporary locations but with considerable social strengths. Government policies are only partially addressing these issues. They pay greater attention to formally encouraging citizens to become more involved in policy making, largely ignore the contribution young people could make to the community cohesion agenda, and weakly define the shared norms and values that are crucial in building cohesive communities. Thus, the conclusion is that whilst an emphasis of the government on ‘community’ is to be welcome, more needs to be done in terms of considering the ‘voices’ of the community as well as enabling communities to determine and act upon their priorities.  相似文献   

Sediment distribution and depositional processes along the fluvial to marine transition zone of the Mekong River delta,Vietnam     

Marcello Gugliotta  Yoshiki Saito  Van Lap Nguyen  Thi Kim Oanh Ta  Toru Tamura 《Sedimentology》2019,66(1):146-164

The area of coastal rivers with a combination of fluvial, tidal and wave processes is defined as the fluvial to marine transition zone and can extend up to several hundreds of kilometres upstream of the river mouth. The aim of this study is to improve the understanding of sediment distribution and depositional processes along the fluvial to marine transition zone using a comprehensive dataset of channel bed sediment samples collected from the Mekong River delta. Six sediment types were identified and were interpreted to reflect the combined action of fluvial and marine processes. Based on sediment‐type associations, the Mekong fluvial to marine transition zone could be subdivided into an upstream tract and a downstream tract; the boundary between these two tracts is identified 80 to 100 km upstream of the river mouth. The upstream tract is characterized by gravelly sand and sand and occasional heterolithic rhythmites, suggesting bed‐load supply and deposition mainly controlled by fluvial processes with subordinate tidal influence. The downstream tract is characterized by heterolithic rhythmites with subordinate sand and mud, suggesting suspended‐load supply and deposition mainly controlled by tidal processes with subordinate fluvial influence. Sediment distributions during wet and dry seasons suggest significant seasonal changes in sediment dynamic and depositional processes along the fluvial to marine transition zone. The upstream tract shows strong fluvial depositional processes with subordinate tidal influence during the wet season and no deposition with weak fluvial and tidal processes during the dry season. The downstream tract shows strong coexisting fluvial and tidal depositional processes during the wet season and strong tidal depositional processes with negligible fluvial influence during the dry season. Turbidity maxima are present along the downstream tract of the fluvial to marine transition zone during both wet and dry seasons and are driven by a combination of fluvial, tidal and wave processes.  相似文献