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Extensive, mainly acidic peraluminous magmatism affected the Tuscan Archipelago and the Tuscan mainland since late Miocene, building up the Tuscan Magmatic Province (TMP) as the Northern Apennine fold belt was progressively thinned, heated and intruded by mafic magmas. Between 3.8 and 1.3 Ma an intrusive complex was built on Larderello area (Tuscan mainland) by emplacement of multiple intrusions of isotopically and geochemically distinct granite magmas. Geochemical and isotopic investigations were carried out on granites cored during drilling exploration activity on the Larderello geothermal field. With respect to the other TMP granites the Larderello intrusives can be classified as two-mica granites due to the ubiquitous presence of small to moderate amounts of F-rich magmatic muscovite. They closely resemble the almost pure crustal TMP acidic rocks and do not show any of the typical petrographic features commonly observed in the TMP hybrid granites (enclaves, patchy zoning of plagioclase, amphibole clots). On the basis of major and trace elements, as well as REE patterns, two groups of granites were proposed: LAR-1 granites (3.8–2.3 Ma) originated by biotite-muscovite breakdown, and LAR-2 granites (2.3–1.3 Ma) generated by muscovite breakdown. At least three main crustal sources (at 14–23 km depth), characterized by distinct εNd(t) and 87Sr/86Sr values, were involved at different times, and the magmas produced were randomly emplaced at shallow levels (3–6 km depth) throughout the entire field. The partial melting of a biotite-muscovite-rich source with low εNd(t) value (about −10.5) produced the oldest intrusions (about 3.8–2.5 Ma). Afterwards (2.5–2.3 Ma), new magmas were generated by another biotite-rich source having a distinctly higher εNd(t) value (−7.9). Finally, a muscovite-rich source with high εNd(t) (about −8.9) gave origin to the younger group of granites (2.3–1.0 Ma). The significant Sr isotope disequilibrium recorded by granites belonging to the same intrusion is interpreted, as due to the short residence time of magmas in the source region followed by their rapid transfer to the emplacement level. Partial melting was probably triggered by multiple, small-sized mafic intrusions, distributed over the last 3.8 Ma that allowed temporary overstepping of biotite- and muscovite-dehydration melting reactions into an already pre-heated crust. Dilution in time of the magmatic activity probably prevented melt mingling and homogenization at depth, as well as the formation of a single, homogeneous, hybrid pluton at the emplacement level. Moreover the high concentrations of fluxing elements (B, F, Li) estimated for the LAR granites modified melt properties by reducing solidus temperatures, decreasing viscosity and increasing H2O solubility in granite melts. The consequences were a more efficient, fast, magma extraction and transfer from the source, and a prolonged time of crystallization at the emplacement level. These key factors explain the long-lived hydrothermal activity recorded in this area by both fossil (Plio-Quaternary ore deposits) and active (Larderello geothermal field) systems. 相似文献
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The model SCIARA, based on the Cellular Automata paradigm, is a versatile instrument whose scope is to analyse volcanic risk from lava flows.The possible fields of intervention are:[(a)] Long term forecasting of the flow direction at various eruption rates and points of emission by locating potential risk areas and permitting the creation of detailed maps of risk;[(b)] The possibility to follow the progress of an event and predict its evolution;[(c)] The verification of the possible effects of human intervention on real or simulated flows in stream deviation.A risk scenario has been developed for the Etnean territories of the towns of Nicolosi, Pedara and S. Alfio, simulating possible episodes with different vent locations along the fracture opened in the 1989 eruption and successively activated in the 1991–1993 eruption.The main characteristics of lava flows, that might be dangerous to the inhabited areas, have been analysed on the basis of the carried out Cellular Automata. 相似文献
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The fate of alpine species in response to climate warming is still unclear. We analyze effects of climate warming on the composition of alpine plants communities and unravel the range filling of communities within a belt from long-term true upward shift processes. In the European Alps we re-sampled in 2003 the vegetation at sites studied in 1953 and analyzed the changes at intra- and inter-community level. Since 1953 all communities experienced a high species turnover, leading to an overall increase in species richness as new species exceeded species losses. The dominant species mainly declined allowing the potential expansion of competitors and/or of new species. The main recruitment sources are neighbor communities within the same elevation belt performing biotic exchanges with other plant communities in the same altitudinal belts. The changes of species distribution curves with elevation emphasized that more than half of the most widespread persisting species exhibited downward shifts instead of upward shifts. Upward shifts from lower elevation belts and of nonnative species were very limited. One third of the persisting species declined and could be used as a proxy to measure the extinction debt. Therefore the fate of plant communities will depend on the ability of the original species to persist and fill the available ecological gaps. Species persistence may be crucial in developing adaptation and environmental protection strategies. 相似文献
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Galimberti Matteo Marinoni Nicoletta Della Porta Giovanna Marchi Maurizio Dapiaggi Monica 《Mineralogy and Petrology》2017,111(5):793-806
Mineralogy and Petrology - Limestone represents the main raw material for ordinary Portland cement clinker production. In this study eight natural limestones from different geological environments... 相似文献
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F. Ruggieri V. Marín D. Gimeno J.L. Fernandez-Turiel M. García-Valles L. Gutierrez 《Engineering Geology》2008,101(3-4):245-250
Natural zeolitic rocks consisting mainly of chabazite-phillipsite, clinoptilolite, and volcanic glass have been evaluated by means of batch methods to remove arsenic from waters with different mineralization degree (from deionized water to natural water with a specific conductivity of 1,600 μS cm− 1). Arsenic was previously spiked in the studied waters at concentrations of about 100 µg l− 1 to simulate actual cases. The compositional range of natural waters is representative of large hydrogeochemical regions around the world. The experiments were focussed on the application of natural common zeolitic rocks to water treatment for human consumption. The removal efficiency observed rises, in the better cases, 60–80% for chabazite-phillipsite raw materials whereas is 40–60% for clinoptilolite-bearing ones. The arsenic removal tends to increase with water mineralization degree, independently of the zeolitic rock type. A large zeolitic content in the chabazite-phillipsite raw materials increase the removal. Instead, the inverse situation is observed in the clinoptilolite-bearing rocks. The relevance of the quantitative mineralogical analysis, determining also the content of volcanic glass, as well as the use of natural waters in the removal tests has been demonstrated. 相似文献
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M. Secomandi V. Paoletti G. Aiello M. Fedi E. Marsella S. Ruggieri B. D’Argenio A. Rapolla 《Marine Geophysical Researches》2003,24(3-4):207-221
We here present and discuss the results of the analysis and qualitative interpretation of two magnetic surveys performed in the Bay of Naples in 1998 and 2000. A map of the Bay of Naples based on the data acquired during these surveys has already been published by the Italian CNR-IAMC Research Institute. We re-processed the same data to produce maps of the pole reduced, analytic signal and horizontal derivative data and correlated them with the bathymetry and the gravimetric data of the area. The analysis shows strong anomalies in the NW and NE volcanic areas of the Bay of Naples, while the central area seems magnetically quiet. In the Phlegrean area the maps clearly show the southern rim of the Phlegrean caldera and demonstrate that while the Magnaghi Canyon is correlated to gravimetric highs and magnetic structures, and can therefore be interpreted as an active lineament, most of Dohrn Canyon is not characterized by volcanic activity and does not correlate to any gravimetric or magnetic structures. An important round-shaped magnetic anomaly is for the first time identified in the central slope of the gulf between the two canyons, probably correlated to a large buried volcanic edifice. In the Vesuvian area some intense circular anomalies, aligned in the NNW–SSE direction, are localized in the Torre del Greco and Torre Annunziata offshore, related to the submerged part of Vesuvius and possibly connected to buried vents. 相似文献
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Eva Pacioni Marco Petitta Ezio Burri Maria Fanelli Piero Mazzeo Fabrizio Ruggieri 《Environmental Earth Sciences》2010,61(1):201-216
This paper analyses flow and transport of pesticides from the unsaturated zone to groundwater so as to predict concentration
of those contaminants in the Fucino Plain’s groundwater, by site investigations and numerical simulations. Pesticides were
detected in surface water (peaks of 13 μg L−1) and groundwater (peaks of 0.37 μg L−1). Modelling tools made it possible to identify that pattern of precipitation, organic matter content, and root thickness
are the key factors involved in vertical seepage of pesticides. Numerical simulations indicated that a significant fraction
of contaminants is leached from the most surficial soil layers through runoff, while only a secondary fraction is mobilised
towards groundwater. Likelihood of contaminating deep groundwater is fairly low, whereas surface waters show higher susceptibility.
Results of the proposed conceptual hydrogeological model show that pesticides are more likely to be entrained by mixing of
stream water with shallow groundwater in periods of high water exploitation from shallow wells. 相似文献
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Shallow landslides in pyroclastic soils: a distributed modelling approach for hazard assessment 总被引：3，自引：0，他引：3
Paolo Frattini Giovanni B. Crosta Nicoletta Fusi Paolo Dal Negro 《Engineering Geology》2004,73(3-4):277-295
An effective assessment of shallow landslide hazard requires spatially distributed modelling of triggering processes. This is possible by using physically based models that allow us to simulate the transient hydrological and geotechnical processes responsible for slope instability. Some simplifications are needed to address the lack of data and the difficulty of calibration over complex terrain at the catchment's scale. We applied two simple hydrological models, coupled with the infinite slope stability analysis, to the May 1998 landslide event in Sarno, Southern Italy. A quasi-dynamic model (Barling et al., 1994) was used to model the contribution to instability of lateral flow by simulating the time-dependent formation of a groundwater table in response to rainfall. A diffusion model [Water Resour. Res. 36 (2000) 1897] was used to model the role of vertical flux by simulating groundwater pressures that develop in response to heavy rainstorms. The quasi-dynamic model overestimated the slope instability over the whole area (more than 16%) but was able to predict correctly slope instability within zero order basins where landslides occurred and developed into large debris flows. The diffusion model simulated correctly the triggering time of more than 70% of landslides within an unstable area amounting to 7.3% of the study area. These results support the hypothesis that both vertical and lateral fluxes were responsible for landslide triggering during the Sarno event, and confirm the utility of such models as tools for hazard planning and land management. 相似文献