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41.
Cristina?PerinelliEmail author Pietro?Armienti Luigi?Dallai 《Contributions to Mineralogy and Petrology》2006,151(3):245-266
Peridotite xenoliths found in Cenozoic alkali basalts of northern Victoria Land, Antarctica, vary from fertile spinel-lherzolite
to harzburgite. They often contain glass-bearing pockets formed after primary pyroxenes and spinel. Few samples are composite
and consist of depleted spinel lherzolite crosscut by amphibole veins and/or lherzolite in contact with poikilitic wehrlite.
Peridotite xenoliths are characterized by negative Al2O3–Mg# and TiO2–Mg# covariations of clino- and orthopyroxenes, low to intermediate HREE concentrations in clinopyroxene, negative Cr–Al trend
in spinel, suggesting variable degrees of partial melting. Metasomatic overprint is evidenced by trace element enrichment
in clinopyroxene and sporadic increase of Ti–Fetot. Preferential Nb, Zr, Sr enrichments in clinopyroxene associated with high Ti–Fetot contents constrain the metasomatic agent to be an alkaline basic melt. In composite xenoliths, clinopyroxene REE contents
increase next to the veins suggesting metasomatic diffusion of incompatible element. Oxygen isotope data indicate disequilibrium
conditions among clinopyroxene, olivine and orthopyroxene. The highest δ18O values are observed in minerals of the amphibole-bearing xenolith. The δ18Ocpx correlations with clinopyroxene modal abundance and geochemical parameters (e.g. Mg# and Cr#) suggest a possible influence
of partial melting on oxygen isotope composition. Thermobarometric estimates define a geotherm of 80°C/GPa for the refractory
lithosphere of NVL, in a pressure range between 1 and 2.5 GPa. Clinopyroxene microlites of melt pockets provide P–T data close
to the anhydrous peridotite solidus and confirm that they originated from heating and decompression during transport in the
host magma. All these geothermometric data constrain the mantle potential temperature to values of 1250–1350°C, consistent
with the occurrence of mantle decompressional melting in a transtensive tectonic regime for the Ross Sea region. 相似文献
42.
Relative sea level rise (RSLR) due to climate change and geodynamics represents the main threat for the survival of Venice,
emerging today only 90 cm above the Northern Adriatic mean sea level (msl). The 25 cm RSLR occurred over the 20th century,
consisting of about 12 cm of land subsidence and 13 cm of sea level rise, has increased the flood frequency by more than seven
times with severe damages to the urban heritage. Reasonable forecasts of the RSLR expected to the century end must be investigated
to assess the suitability of the Mo.S.E. project planned for the city safeguarding, i.e., the closure of the lagoon inlets
by mobile barriers. Here we consider three RSLR scenarios as resulting from the past sea level rise recorded in the Northern
Adriatic Sea, the IPCC mid-range A1B scenario, and the expected land subsidence. Available sea level measurements show that
more than 5 decades are required to compute a meaningful eustatic trend, due to pseudo-cyclic 7–8 year long fluctuations.
The period from 1890 to 2007 is characterized by an average rate of 0.12 ± 0.01 cm/year. We demonstrate that linear regression
is the most suitable model to represent the eustatic process over these 117 year. Concerning subsidence, at present Venice
is sinking due to natural causes at 0.05 cm/year. The RSLR is expected to range between 17 and 53 cm by 2100, and its repercussions
in terms of flooding frequency are associated here to each scenario. In particular, the frequency of tides higher than 110 cm,
i.e., the value above which the gates would close the lagoon to the sea, will increase from the nowadays 4 times per year
to a range between 20 and 250. These projections provide a large spread of possible conditions concerning the survival of
Venice, from a moderate nuisance to an intolerable aggression. Hence, complementary solutions to Mo.S.E. may well be investigated. 相似文献
43.
Luigi Sambuelli 《Rock Mechanics and Rock Engineering》2009,42(3):547-556
I would like to suggest a theoretical justification for the mathematical structure of some laws for predicting the maximum
particle velocity vibration from blasting operations in the light of some basic notions of elastic and anelastic wave theory.
Within this point of view, in dimensionally correct expressions, the terms pertaining to the rock, to the blast and to the
seismic wave become evident and recognisable. A law is presented that can be used to forecast the maximum particle velocity
on the basis of some blast design and rock parameters. Four tests of the proposed law performed with real data sets seem to
confirm fairly well its reliability. 相似文献
44.
In this paper we describe a new computing system array, designed, built and now used at the Space Astrophysics and Planetary Institute (IAPS) in Rome, Italy, for the INTEGRAL Space Observatory scientific data analysis. This new system has become necessary in order to reduce the processing time of the INTEGRAL data accumulated during the more than 9 years of in-orbit operation. In order to fulfill the scientific data analysis requirements with a moderately limited investment the starting approach has been to use a ??cluster?? array of commercial quad-CPU computers, featuring the extremely large scientific and calibration data archive on line. 相似文献
45.
Stefano Urbini Iacopo Nicolosi Antonio Zeoli Sami El Khrepy Ahmed Lethy Mahfooz Hafez Mohamed El Gabry Ahmed El Barkooky Aly Barakat Mahomoud GOMAA Ali M. Radwan Mohamed El Sharkawi Massimo D’orazio Luigi Folco 《Meteoritics & planetary science》2012,47(11):1842-1868
Abstract– We detail the Kamil crater (Egypt) structure and refine the impact scenario, based on the geological and geophysical data collected during our first expedition in February 2010. Kamil Crater is a model for terrestrial small‐scale hypervelocity impact craters. It is an exceptionally well‐preserved, simple crater with a diameter of 45 m, depth of 10 m, and rayed pattern of bright ejecta. It occurs in a simple geological context: flat, rocky desert surface, and target rocks comprising subhorizontally layered sandstones. The high depth‐to‐diameter ratio of the transient crater, its concave, yet asymmetric, bottom, and the fact that Kamil Crater is not part of a crater field confirm that it formed by the impact of a single iron mass (or a tight cluster of fragments) that fragmented upon hypervelocity impact with the ground. The circular crater shape and asymmetries in ejecta and shrapnel distributions coherently indicate a direction of incidence from the NW and an impact angle of approximately 30 to 45°. Newly identified asymmetries, including the off‐center bottom of the transient crater floor downrange, maximum overturning of target rocks along the impact direction, and lower crater rim elevation downrange, may be diagnostic of oblique impacts in well‐preserved craters. Geomagnetic data reveal no buried individual impactor masses >100 kg and suggest that the total mass of the buried shrapnel >100 g is approximately 1050–1700 kg. Based on this mass value plus that of shrapnel >10 g identified earlier on the surface during systematic search, the new estimate of the minimum projectile mass is approximately 5 t. 相似文献
46.
Matthias
Van GINNEKEN Luigi FOLCO Carole CORDIER Pierre ROCHETTE 《Meteoritics & planetary science》2012,47(2):228-247
Abstract– On the basis of morphological and petrographic characteristics, eight “giant” unmelted micrometeorites in the 300–1100 μm size range were selected from the Transantarctic Mountain micrometeorite collection, Victoria Land, Antarctica. Mineralogical and geochemical data obtained by means of scanning electron microscopy, electron probe microanalyses, and synchrotron X‐ray diffraction allow their classification as chondritic micrometeorites. The large size of the micrometeorites increases considerably the amount of mineralogical and geochemical information compared to micrometeorites in smaller size fractions, therefore allowing a better definition of their parent material. A large variety of material is observed: five micrometeorites are related to unequilibrated and equilibrated ordinary chondrite, one to CV chondrite, one to CM chondrite, and one to CI chondrite parent materials. Besides reporting the first occurrence of a CV‐like micrometeorite, our study shows that the abundance of chondritic material supports observations from recent studies on cosmic spherules that a large part of the micrometeorite flux in this size range is of asteroidal origin. 相似文献
47.
Prof. Dr. Luigi Castoldi 《Pure and Applied Geophysics》1950,18(1):160-161
Riassunto Si fa uso di una formula di derivazione di un integrale di superficie per dimostrare un teorema meteorologico diV. Bjerknes.
Summary Use is made of a differentiation's formula for surface integrals in showing aV. Bjerknes' meteorological theorem.相似文献
48.
Prof. Luigi Castoldi 《Pure and Applied Geophysics》1952,23(1):27-35
Riassunto Si determina la distribuzione teorica della temperatura in an gradino della crosta terrestre, quale si averebbe ai margini dei continenti o delle fosse cceaniche in condizioni di isotropia ed omogeneità del materiale; deducendone alcune particolarità.
Summary The theoretical distribution of the temperature in a step-shaped part of the earth's crust has been determined, how it would be on the edge of the continents or the shelf of the oceans, under isotropic conditions and homogeneity of the material. Some inferences are deduced.相似文献
49.
Of the many topographic features, more specifically seamounts, that are ubiquitous in the ocean floor, we focus our attention on those with relatively shallow summits that can interact with wind-generated surface waves. Among these, especially relatively long waves crossing the oceans (swells) and stormy seas are able to affect the water column up to a considerable depth and therefore interact with these deep-sea features. We quantify this interaction through numerical experiments using a numerical wave model (SWAN), in which a simply shaped seamount is exposed to waves of different length. The results show a strong interaction that leads to significant changes in the wave field, creating wake zones and regions of large wave amplification. This is then exemplified in a practical case where we analyze the interaction of more realistic sea conditions with a very shallow rock in the Yellow Sea. Potentially important for navigation and erosion processes, mutatis mutandis, these results are also indicative of possible interactions with emerged islands and sand banks in shelf seas. 相似文献
50.
Mechanisms linking active rock glaciers and impounded surface water formation in high‐mountain areas 下载免费PDF全文
Nicola Colombo Luigi Sambuelli Cesare Comina Chiara Colombero Marco Giardino Stephan Gruber Gaetano Viviano Livia Vittori Antisari Franco Salerno 《地球表面变化过程与地形》2018,43(2):417-431
Rock glaciers are slowly flowing mixtures of debris and ice occurring in mountains. They can represent a reservoir of water, and melting ice inside them can affect surface water hydrochemistry. Investigating the interactions between rock glaciers and water bodies is therefore necessary to better understand these mechanisms. With this goal, we elucidate the hydrology and structural setting of a rock glacier–marginal pond system, providing new insights into the mechanisms linking active rock glaciers and impounded surface waters. This was achieved through the integration of waterborne geophysical techniques (ground penetrating radar, electrical resistivity tomography and self‐potentials) and heat tracing. Results of these surveys showed that rock glacier advance has progressively filled the valley depression where the pond is located, creating a dam that could have modified the level of impounded water. A sub‐surface hydrological window connecting the rock glacier to the pond was also detected, where an inflow of cold and mineralised underground waters from the rock glacier was observed. Here, greater water contribution from the rock glacier occurred following intense precipitation events during the ice‐free season, with concomitant increasing electrical conductivity values. The outflowing dynamic of the pond is dominated by a sub‐surface seepage where a minor fault zone in bedrock was found, characterised by altered and highly‐fractured rocks. The applied approach is evaluated here as a suitable technique for investigating logistically‐complex hydrological settings which could be possibly transferred to wider scales of investigation. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献