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61.
Cordierite-bearing lavas (CBL;~105 ka) erupted from the Mt. S. Angelo volcano at Lipari (Aeolian arc, Italy) are high-K andesites, displaying a range in the geochemical and isotopic compositions that reflect heterogeneity in the source and/or processes. CBL consist of megacrysts of Ca-plagioclase and clinopyroxene, euhedral crystals of cordierite and garnet, microphenocrysts of orthopyroxene and plagioclase, set in a heterogeneous rhyodacitic-rhyolitic groundmass containing abundant metamorphic and gabbroic xenoliths. New petrographic, chemical and isotopic data indicate formation of CBL by mixing of basaltic-andesitic magmas and high-K peraluminous rhyolitic magmas of anatectic origin and characterize partial melting processes in the lower continental crust of Lipari. Crustal anatectic melts generated through two main dehydration-melting peritectic reactions of metasedimentary rocks: (1) Biotite + Aluminosilicate + Quartz + Albite = Garnet + Cordierite + K-feldspar + Melt; (2) Biotite + Garnet + Quartz = Orthopyroxene + Cordierite + K-feldspar + Melt. Their position into the petrogenetic grid suggests that heating and consequent melting of metasedimentary rocks occurred at temperatures of 725 < T < 900°C and pressures of 0.4–0.45 GPa. Anatexis in the lower crust of Lipari was induced by protracted emplacement of basic magmas in the lower crust (~130 Ky). Crustal melting of the lower crust at 105 ka affected the volcano evolution, impeding frequent mafic-magma eruptions, and promoting magma stagnation and fractional crystallization processes.  相似文献   
62.
On far field occurrence of seismically induced landslides   总被引:1,自引:0,他引:1  
Earthquakes may induce landslides at large distances from the epicentral area. In the last two decades, there have been many studies of this phenomenon to determine the causes that contribute to the occurrence of landslides at very long distances from earthquake epicenter. In this study, which is based on previously published works, a worldwide database comprising 270 earthquakes, including 150 during the instrumental period, was compiled to analyse the features of those landslides that occur at much further distances than maximum expected distances. From the analysis of the compiled data, it was observed that susceptible slopes can be grouped into five broad geological categories: jointed rock, marly–clayey (cohesive) soils, granular alluvial and/or colluvial sediments, volcanic soils, and residual soil slopes. These categories were equally likely to be associated with far field disrupted landslides, whereas far field coherent landslides were more frequent on cohesive soil slopes. Other factors, along with slope susceptibility may also contribute to far field landslides and increase the size of the area affected. Among these factors, site effects, antecedent rain and occurrence of seismic series have been cited. The analysis of available data also showed that for events of the same magnitude, far field disrupted landslides may occur at greater distances than coherent ones. The same database has also been employed to determine, for the first time, the upper bound curves for the maximum observed epicentral distances of several types of landslides and the maximum area observed to be affected by landslides, both based on the epicentral intensity of the events.  相似文献   
63.
Member States of the European Union and the Mediterranean Regional Sea need to elaborate national strategies for coastal management according to ICZM principles and to undertake national stock-taking, which must consider major actors, laws and institutions influencing the management of their national coastal zone. However, different approaches to coastal management and defence and various degrees of development and implementation of national ICZM strategies can be found. The research presented in this article aims to analyze the different situations and to contribute to the further development of a common approach in terms of methodology to establish stakeholder and users participation in ICZM. An extensive survey was conducted in five pilot sites along the European Mediterranean coastal zone (Greece, Italy and France) show beach visitors’ perception of ICZM, coastal erosion and coastal defence systems, and beach visitors’ Willingness To Pay (WTP) for beach defence. The survey yielded important information for coastal and beach managers. Surprisingly, the level of awareness about generic Coastal Zone Management was found to be rather low in all regions except Riccione Southern beach, Emilia-Romagna Region. In the Languedoc-Roussillon Region, this is justified by the fact that most of the respondents were not local people or beach visitors (other than recreational day-visitors). As regards coastal erosion it appears significant that, despite the lack of awareness demonstrated overall by stakeholders in the Region of East Macedonia and Thrace, visitors respond very positively to definitions and show awareness of the erosion process in their coastal system. In conclusion, in order to raise public awareness about ICZM, erosion and coastal defence systems, it is suggested that education, training and public awareness should be promoted as well as identification of local needs for the implementation of specific demand-driven studies.  相似文献   
64.
We have discovered that the Asteroid (234) Barbara exhibits very anomalous polarimetric properties. The phase-polarization curve of this asteroid is unique and is not matched by any other known atmosphereless body of our Solar System. Although a few preliminary conjectures can be made, for the moment the reasons of the peculiar polarimetric properties of this asteroid remain essentially unknown.  相似文献   
65.
 Bromine/chlorine ratios in salammoniac samples, collected from 1983 to 1994 at the Fossa crater fumaroles of Vulcano (Aeolian Islands), were determined. The data obtained in this work have been compared to those obtained by Coradossi et al. (1985) in order to carry out a systematic study of the Br/Cl ratio variations since 1977. Br/Cl ratios range from 0.04 to 0.29. The Br/Cl ratio variations observed have been interpreted as the result of different contributions among deep and shallow components feeding the fumarolic fluids of Vulcano. The Br/Cl increases, which occurred from 1977 to 1979, in 1983–1984 and in 1992–1993, have been connected to an increased input of magmatic gases. Received: 10 November 1995 / Accepted: 12 July 1996  相似文献   
66.
We present the results of a campaign of spectroscopic observations of Jupiter Trojan asteroids. Thirty-four objects were observed during three runs in July and November 1998, and March 2002 using the Danish 1.54-m telescope at ESO. The covered spectral range was between 5000 and 9000 Å. Our observations include objects belonging both L4 to L5 clouds. According to analyses of previous investigations of Trojans, the spectra of different taxonomic classes can be separated on the basis of the slope of the reflectance spectrum. The large majority of the objects of our sample have been found to belong to the D taxonomic class, but we found also objects of P- and C-type. In two cases, we found also evidence of blueish spectral trends. Our data are important, since they allow us to substantially enlarge the whole data set of available Trojan spectra.  相似文献   
67.
Progress of modern astrophysics requires the access to the electromagnetic spectrum in the broadest energy range. The Ultraviolet is a fundamental energy domain since it is one of the most powerful tool to study plasmas at temperatures in the 3,000–300,000 K range as well as electronic transitions of the most abundant molecules in the Universe. Moreover, the UV radiation field is a powerful astrochemical and photoionizing agent.The objective of this review is to describe the crucial issues that require access to the UV range. A summary has been added to the end with a more classic view of UV needs by astronomical object type; this approach is followed at length in the rest of the contributions of this issue.  相似文献   
68.
Intermediate polars (IPs) are cataclysmic variables which contain magnetic white dwarfs with a rotational period shorter than the binary orbital period. Evolutionary theory predicts that IPs with long orbital periods evolve through the 2–3 h period gap, but it is very uncertain what the properties of the resulting objects are. Whilst a relatively large number of long-period IPs are known, very few of these have short orbital periods. We present phase-resolved spectroscopy and photometry of SDSS J233325.92+152222.1 (SDSS J2333) and classify it as the IP with the shortest-known orbital period (83.12 ± 0.09 min), which contains a white dwarf with a relatively long spin period (41.66 ± 0.13 min). We estimate the white dwarf's magnetic moment to be μWD≈ 2 × 1033 G cm3, which is not only similar to three of the other four confirmed short-period IPs but also to those of many of the long-period IPs. We suggest that long-period IPs conserve their magnetic moment as they evolve towards shorter orbital periods. Therefore, the dominant population of long-period IPs, which have white dwarf spin periods roughly 10 times shorter than their orbital periods, will likely end up as short-period IPs like SDSS J2333, with spin periods a large fraction of their orbital periods.  相似文献   
69.
Recent results support a possible ambiguity for several adopted values of the spin rates. An analysis of the present data set on the rotational properties is made in order to select a number of asteroids, for which new observations should be performed to check the reliability of their adopted parameters. The most significant example is presented and it concerns the very large asteroid 52 Europa. Its lightcurve presented two maxima and two minima during 1976 opposition leading to a period of 11h.26. In 1983 the same number of extrema appeared in 5h.63 only. The amplitude was small in both oppositions (~0m.08 and ~0m.10, respectively) and suggests the possibility of surface irregularities which dominate the light variation. Other hypotheses can be made but generally the period determination of asteroids is more difficult than previously believed.  相似文献   
70.
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