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31.
Domenico Cicchella Lucia Giaccio Annamaria Lima Stefano Albanese Antonio Cosenza Diego Civitillo Benedetto De Vivo 《Environmental Earth Sciences》2014,71(12):5129-5143
The Sarno River basin area is one of the most polluted in Europe and it is due to the waste products of the tomato industry, the leather tanneries and the pharmaceutical industry. This area also has been densely populated and urbanized since the Middle Bronze Age, as testified by the presence of numerous archeological sites, including the ancient Pompeii town, and environmental degradation that characterizes the area is absolutely unacceptable. This paper represents a detailed study to assess the potentially harmful element content of topsoils. In total, 283 soil samples were collected and analyzed, after an aqua regia extraction, by a combination of inductively coupled plasma atomic emission and inductively coupled plasma mass spectrometry for 53 elements. Univariate and multivariate analyses were carried out to show the single-element geochemical distribution and the distribution of factor scores of the elemental associations resulting from R-mode factor analysis. Maps showing elements and the association factor score distributions have been obtained using GeoDAS and ArcGIS software. The assessment of the soil contamination was also carried out using the contamination factor and degree of contamination. The results obtained indicate that soil pollution has different anthropogenic sources. Specifically, Cr pollution derives from tanneries discharging wastewaters in the main water bodies of the basin while Cu contamination seems to depend on widespread agricultural practices. Tin, Pb, Hg, Zn, Cd, Sb anomalies are found mainly in urban and industrial areas, sometimes close to roads with high traffic levels while there is a substantial coincidence with background values for other elements (Co, Ni, Se, Tl and V). 相似文献
32.
A finite element analysis is presented of some direct shear tests carried out on samples of a stiff, heavily overconsolidated clay. The effects of softening are accounted for through a simple material model which views this phenomenon as a consequence of an intrinsic loss of strength of the material taking place when plastic strains increase. After illustrating the main characteristics of the finite element approach, with particular reference to the correct determination of the non-reversible strains, its use in the interpretation of the mentioned shear tests is discussed. Some comments are also presented on the mesh dependence of the numerical results, and on the use of a relation between material parameters and element size which reduces this negative effect. Finally, the solution procedure is applied to the simulation of a compression test in order to investigate the possibility of numerically detecting the ‘spontaneous’ (i.e. not directly induced by the boundary conditions) formation of shear zones within the specimen. 相似文献
33.
A. Fornelli 《Mineralogy and Petrology》1994,51(1):49-65
Summary Late-hercynian granodiorites in the eastern Serre are calc-alkaline and peraluminous in composition; actinolitic-hornblende typically occurs in the mafic types, whereas muscovite occurs in the felsic ones. Magmatic microgranular enclaves and small metamorphic xenoliths are present in these granitoids. A petrographical study and microprobe analyses on plagioclase, biotite, amphibole, cordierite and cummingtonite in xenoliths and enclaves and in the host rocks were performed. The presence of sillimanitecordierite-biotite-hercynite and of cummingtonite-biotite-bearing xenoliths suggests that partial melting of a heterogeneous deep crust played an important role in the genesis of the granitoids. In contrast, the occurrence of microgranular enclaves suggests that a sub-crustal component might have been involved. Two alternative mechanisms are proposed to explain the magma genesis: i) mixing between subcrustal and crustal melts; ii) direct crustal genesis.
With 6 Figures 相似文献
Metamorphe Xenolithe und mikrogranulare Einschlsse im Serre Granodiorit (Sükalabrien, Italien) und ihre Bezienhungen zur Granitoidgenese
Zusammenfassung Spätherzynische Granodiorite des östlichen Serre-Gebietes zeigen kalk-alkalische und peraluminöse Zusammensetzung. Aktinolithische Hornblende tritt typischerweise in den mafischen, Muskowit in den sauren Gesteinen auf. In den Granitoiden vorkommende, magmatische, mikrogranulare Einschlüsse und kleine metamorphe Xenolithe wurden petrographisch und mittels Mikrosondenanalytik an Plagioklas, Biotit, Amphibol, Cordierit und Cummingtonit untersucht. Sillimanit-Cordierit-Biotit-Hercynit-und Cummingtonit-Biotit- führende Xenolithe weisen darauf hin, daß der partiellen Aufschmelzung einer heterogenen Unterkruste eine bedeutende Rolle für die Genese der Granitoide zukommt. Mikrogranulare Einschlüsse weisen dagegen auf die Beteiligung einer subkrustalen Komponente hin. Zwei alternative Mechanismen werden für die Magmengenese diskutiert. i) Mischung von subkrustalen und Krustalen Schmelzen; ii) direkte krustale Genese.
With 6 Figures 相似文献
34.
Francesca Micheletti Pierre Barbey Annamaria Fornelli Giuseppe Piccarreta Etienne Deloule 《International Journal of Earth Sciences》2007,96(5):843-860
In situ U–Pb dating of zircons from five samples of Calabrian augen gneisses shows that their protoliths are Latest Precambrian
to Early Cambrian in age (562 ± 15, 547 ± 7, 540 ± 4, 539 ± 16 and 526 ± 10 Ma), and contain Archaean (3.1 Ga), Palaeoproterozoic
(1.7–2.4 Ga) and Neoproterozoic (0.6–0.9 Ga) inheritance. Geochemical signature of augen gneisses is typical of high-K calc-alkaline
post-collisional magmatism. Their Sr–Nd isotopic compositions [0.7093 < (87Sr/86Sr)i < 0.7139; −3.2 < ɛNd(t) < −5.4; 1.5 < T
DM < 1.7 Ga] indicate the involvement of a crustal component in significant proportions. The Calabrian augen gneisses have,
therefore, to be distinguished from the orthogneisses of Sardinia and northern Algeria, and from the porphyroids of Sicily,
which are Middle Ordovician. By contrast, the Calabrian augen gneisses show a close similarity to the Pan-African post-collisional
granitoids of the northern edge of the West African craton (e.g. the Moroccan Anti-Atlas). This suggests a peri-Gondwana origin
and corroborates previous palaeogeodynamic reconstructions attributing the Alboran microplate to the northern margin of the
West African craton. 相似文献
35.
In the coupled finite element analysis of the two-phase, saturated soils the pore pressure could decrease below the atmospheric pressure in particular when the plastic dilation of the skeleton is accounted for. The consequent reduction of the bulk modulus of the liquid phase is here modelled in a simplified manner through a tension cut off on the pore pressure. Two alternative approaches are outlined in the framework of the finite element method. The first one introduces a unilateral constraint on the nodal pore pressures and involves manipulations on matrices of the assembled mesh, whilst the second approach requires calculations solely at the element level. The effects of the pore pressure tension cut off are illustrated through some undrained test examples in elastic–plastic regime. 相似文献
36.
Marco Pilz Stefano Parolai Dino Bindi Annamaria Saponaro Ulan Abdybachaev 《Pure and Applied Geophysics》2014,171(8):1729-1745
A strong topographic relief and the presence of weakly consolidated sediments create favorable conditions for the development of landslides around the eastern rim of the Fergana Basin (Central Asia). In summer 2012, a field experiment employing small aperture seismic arrays was carried out on an unstable slope, using ambient vibration recordings. The aim of the study was to constrain the seismic response of a potential future landslide and to map lateral and vertical changes in the shear-wave velocity of the surficial soil layers. Strong variations of horizontal-to-vertical spectral ratios in terms of amplitude and directionality indicated clear differences in local site effects, probably reflecting the stability of different sections of the slope. Results further showed resonant frequencies of both the entire unstable block, as well as for smaller, individual parts. The use of an ad hoc, passive seismic tomography approach based on noise correlograms allowed for the mapping of the shear-wave velocities of the sliding material, even in cases of significant topography relief. Based on the recording of seismic noise only, we clearly identified a low-velocity body of weakly consolidated claystone and limestone material, which can be interpreted as the landslide body, with laterally varying thickness. 相似文献
37.
GRACE重力卫星可用于观测南极洲冰川的质量变化。由GRACE重力卫星提供的月解重力场能有效探测质量的年变化及长期变化(周期和非周期性)。通过GRACE观测的质量变化时间序列,计算得到南极洲质量的长期变化及周期性年变化。计算结果受多种误差影响,其中GRACE模型误差的影响较小,而研究时段及其跨度的影响较为显著,以不同宽度的时间窗口进行平移,得到无穷时间序列下该误差的参考值为±14.89 mm/a。南极地区的气压修正误差可达±10 mm/a,GIA修正误差与其量级相同。由此我们认为,目前对于南极洲冰川质量变化的一些认识仍需商榷。南极洲西部地区冰川加速消融,Dronning Maud Land和Enderby Land等地区的质量持续累积;其他地区的质量变化情况仍需进一步研究。 相似文献
38.
Metabasic rocks related to pre-Cambrian protoliths from the lower portion of the deep crust of the Serre (Calabria, southern Italy) contain porphyroblastic garnet up to 5–6 cm in diameter. Garnet forms coronas around the inclusions of clinopyroxene and is in contact with various matrix minerals. Both inner and outer coronas formed under granulite facies conditions after the thermal peak during the Hercynian reworking. Six porphyroblastic garnets (≥1 cm in diameter) from four samples have been dated with the Sm-Nd method to constrain the distinct metamorphic stages and, possibly, to investigate the diffusion of Sm and Nd in garnet. They show in the core major element flat profiles whereas one of these, analyzed for REEs, preserves only a feeble zoning. This suggests that the diffusion rates of REEs are effective at the crystal scale. The apparent Nd ages range from 354 to 88 Ma, without any reproducibility in each and in all rock samples. The oldest age of 354 Ma is interpreted as the primary isotopic signatures linked to prograde metamorphism. The interpretation of younger ages (309, 272, 215, 143 and 88 Ma) requires a detailed discussion about: (i) possible modification of chemical and isotopic composition of the rocks during and after garnet growth, (ii) possible contamination by inclusions in garnet, (iii) inherited isotopic disequilibrium, (iv) new growth or recrystallization of garnet and (v) possible isotopic resetting of large crystals which, in principle, is hampered by the slow diffusion of REE’s in garnet. Some of the Nd ages are similar to U-Pb ages of zircon from the metabasic rocks of deep crustal rocks of the Serre (350, 300 and 280 Ma). This convergence of apparent ages can hardly be considered as simply fortuitous. Thus, since: (i) corona formation was fluid-assisted and (ii) all porphyroblasts were broken up into several fragmented subgrains by sets of fractures resulting in smaller volumes, the volume diffusion and the possible role of high-T fluids on the resetting of Sm-Nd ages are discussed. The calculated ages of 354, 309 and 272 Ma are considered as geologically meaningful and related to the thermal peak and subsequent decompression and cooling stage of the Variscan metamorphism. 相似文献
39.
In the Serre mountains of Calabria, Italy, an exposed section of the continental crust, as left by the Hercynian orogeny, consists of intermediate-lower to upper crustal units. Huge masses of granitoids separate the lower from the upper crustal units. Many mica ages have been obtained from metamorphic and plutonic rocks, which have been interpreted as reflecting continuous cooling or discrete Mesozoic events. A reappraisal of previously determined isotopic data integrated with new Rb–Sr biotite ages is presented and assessed at regional scale to better constrain the post-Hercynian geological evolution of the continental crust of the Serre. The ages cover a wide span of time and form clusters which fit a model involving magmatic, hydrothermal and tectonic events preceding and accompanying the opening and closure of the Tethyan ocean. 相似文献
40.
Summary Leucosomes, mesosomes and melanosomes, including 12 leucosome-host rock pairs have been studied for Sr and Nd isotopic systematics
in migmatitic metapelites of the Serre (southern Calabria) which experienced granulite facies conditions in Hercynian times.
Most samples came from the deep to middle part of a metapelitic unit, which is 5–6 km thick.
The leucosomes presently occurring in the migmatites are mainly K-poor peraluminous leucotonalites; the host rocks (metapelites,
metagreywackes and opx-bearing rocks) are more or less depleted in “granitic” component and have molar Al2O3/(CaO + Na2O + K2O) (A/CNK) ratios up to 15; the highest values relate to garnet + sillimanite-rich metapelites. Sm/Nd ratios are generally
lower in the leucosomes and Rb/Sr ratios are very low (≪ 1) and lower than in related mesosomes and melanosomes. The isotopic
Sr and Nd values vary in a wide range within the various kinds of host-rocks and within the leucosomes. A correlation of Nd-
and Sr- isotopic compositions between coexisting leucosomes and host-rocks has not been found. The isotopic Sr and Nd values
of the leucosomes are less variable than the host-rocks; melanosomes having A/CNK ratios > 3 concentrate at the lowest εNd290 Ma values, owing to retention of garnet and accessories and depletion of feldspars. The leucosomes define a hyperbolic trend
where most samples concentrate in the middle part. These features are interpreted as reflecting melting of several rock types
generating melts having a weighted mean composition from the contributing sources. The prevailing leucotonalites and their
very low Rb/Sr ratios indicate that plagioclase played a more important role than mica in the melting processes which produced
the studied leucosomes. Since assemblages lacking or very poor in biotite and K-feldspar are common in metapelitic restites,
potassic melts, as one should expect from melting of micas, must have been extracted before the leucosomes under study formed.
Zusammenfassung
Aufschmelzung im Ungleichgewicht dokumentiert an granulitfaziellen Metasedimenten der n?rdlichen Serre (Kalabrien, Süditalien)
Die Sr und Nd Isotopensystematik von Leuko-, Meso- und Melanosomen, einschlie?lich von 12 Leukosom- und Nebengesteinspaaren,
wurde untersucht. Sie treten in migmatitischen Metapeliten der Serre (südliches Kalabrien) auf, deren granulitfazielle Metamorphose
als hercynisch eingestuft wird. Die meisten Proben stammen aus dem unteren Teil der mittleren Metapeliteinheit, die eine M?chtigkeit
von 5–6 km erreicht.
Die in den Migmatitien auftretenden Leukosome sind haupts?chlich K-arme, peralumin?se Leukotonalite. Die Nebengesteine (Metapelite,
Metagrauwacken, und Opx-führende Gesteine) sind mehr oder weniger an “granitischer” Komponente verarmt und haben molare A/CNK
Verh?ltnisse bis 15, mit den h?chsten Werten in Granat- Sillimanit- reichen Metapeliten. Die Sm/Nd- Verh?ltnisse sind generell
niedriger in den Leukosomen. Rb/Sr ist sehr niedrig (≪ 1) und niedriger als in den Meso- und Melanosomen. Die Sr- und Nd-Isotopenzusammensetzungen
variieren stark innerhalb der verschiedenen Nebengesteine und ihrer assoziierten Leukosome. Eine Korrelation der Nd- und Sr-
Isotopenzusammensetzungen zwischen koexistierenden Leukosomen und Nebengesteinen konnte nicht festgestellt werden. Die Sr-
und Nd-Isotopie der Leukosome ist weniger variabel als die der Nebengesteine. Die Melanosome, sie haben A/CNK > 3, zeigen
die niedrigsten εNd290 Ma Werte als Folge der Retention von Granat und Akzessorien und der Verarmung an Feldspat. Die Leukosome definieren einen hyperbolischen
Trend, wobei die meisten Proben in der Mitte zu liegen kommen. Dies wird so interpretiert, dass mehrere Gesteinstypen, die
eine gewichtete mittlere Zusammensetzung der an der Aufschmelzung beteiligten Ausgangsmaterialien darstellen, aufgeschmolzen
wurden. Die vorherrschenden Leukotonalite und ihre sehr niedrigen Rb/Sr Verh?ltnisse zeigen, dass Plagioklas eine wichtigere
Rolle bei den leukosombildenden Schmelzprozessen spielte als Glimmer. Da Mineralvergesellschaftungen, die arm an Biotit und
Alkalifeldspat sind, h?ufig in metapelitischen Restiten auftreten, müssen K-reiche Schmelzen – sie sind zu erwarten wenn Glimmer
aufgeschmolzen werden – vor der Bildung der Leukosome extrahiert worden sein.
Received November 11, 1998; revised version accepted October 21, 1999 相似文献