Fourier spectrum of the seiches of an ideal rectangular basin with sinusoidally varying level     

Giorgio Manzoni 《Pure and Applied Geophysics》1969,72(1):148-154

Summary If the level of an ideal rectangular water basin varies sinusoidally with amplitude 2h ₁ and angular frequency ₀ the modes of the free oscillations of the basin split into multiplets with spacing ₀: the shape and the height of the peaks are given as functions of the mean levelh ₀ and of the lengthl of the basin and of the amplitude 2h ₁.Istituto di Geodesia e Geofisica, Universita' di Trieste, Italy.- This research has been supported by E.R.O.-U.S. Army, under contract DA-91-591-3538.  相似文献   

Radiometric age evidences of a Triassic Thermal Event in the Southern Alps     

Prof. Giorgio Ferrara  F. Innocenti 《International Journal of Earth Sciences》1974,63(2):572-581

In the Southern Alps several K/Ar age determinations point out the existence of a thermal event of Upper-Triassic age. Radiometric evidences concern overprinting on K/Ar ages of biotites belonging to hercynian periadriatic massives, and of muscovites of pegmatites in which also a Sr isotopic re-equilibration has taken place. Some evidences are also recognizable in ancient metamorphic basement. In the same time an extensive extrusive and intensive magmatic activity of alkaline affinity occurred. These facts are interpreted as predrift events shortly preceeding the set up of lower Jurassic oceanic conditions of alpine area.  相似文献   

Über einen Zusammenhang zwischen atmosphärischen und kosmischen Phänomenen und physikalisch-chemischen Prozessen     

Giorgio Piccardi 《Theoretical and Applied Climatology》1955,6(4):486-505

Zusammenfassung Sei langer Zeit wird ein Zusammenhang zwischen atmosphärischen und kosmischen Vorgängen und physikalisch-chemischen biochemischen und biologischen Prozessen angenommen. Für Forschungen auf diesem Gebiete hat der Verfasser eine ganz einfache, differentialle Methode ausgearbeitet. Es werden Serien-Fällungen von BiOCl gleichzeitig mit normalem und mit physikalisch aktiviertem Wasser bei identischen Bedingungen gemacht; dabei wird die Anzahl der schnelleren und die Anzahl der langsameren Fällungen im aktivierten Wasser gezählt. Die zeitlichen Änderungen des Prozentsatzes der schnelleren Fällungen werden verfolgt. Die Experimente wurden unter zwei verschiedenen Bedingungen ausgeführt: 1. in einem ganz metallfreien Raum und 2. in einem mit Metall abgeschirmten Raum. Die Unterschiede der Ergebnisse beweisen, daß die registrierten Variationen tatsächlich auf Einwirkungen äußerer Faktoren zurückzuführen sind.Es wurde festgestellt: eine säkuläre Variation, die möglicherweise in Zusammenhang mit der Sonnenaktivität steht; eine jährliche Variation, die man vielleicht mit der Erdbewegung in Verbindung bringen kann; und mehrere kleinere Variationen, die mit verschiedenen Elementen in Zusammenhang stehen können. Es werden Korrelationen mit dem Luftdruck, mit dem luftelektrischen Potentialgefälle und mit der kosmischen Strahlungsintensität festgestellt. Ferner zeigt sich, daß die Beschaffenheit des Metallschirmes von Bedeutung ist. Aus in Florenz, Brüssel und Wien durchgeführten Beobachtungen ließ sich ein Breiteneffekt feststellen. Die Untersuchung der Wirkung der Metallabschirmungan sich mit einem vereinfachten Test ohne Aktivierung ergab, daß im Allgemeinen die BiOCl-Fällung unter Abschirmung schneller erfolgt und daß ein Zusammenhang zwischen der spezifischen elektrischen Leitfähigkeit der verwendeten Metalle und dem Abschirmungseffekt besteht.

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Summary It is commonly believed for a long time that there exists a relation between atmospheric and cosmic phenomena and physico-chemical, biochemical and biological processes. The author has developed a simple and differential method for researches in this field. Series of precipitations with BiOCl are simultaneously made with normal and with activated water at identical conditions, whereby is counted the number of the faster and of the slower precipitations in the activated water; the temporal variations of the percentage of the faster precipitations are studied. The experiments have been carried out with the following two conditions: (1) in a room free of any metal, (2) in a room isolated with metal. The differences in the results prove that the variations obtained are due in fact to the influence of exterior factors.Has been ascertained: a secular variation which might be in connexion with the sunspot activity, an annual variation which might be in connexion with the earth's rotation, and several smaller variations which may be in relation with different elements. There are found correlations with the atmospheric pressure, with the potential gradient of atmospheric electricity and with the intensity of cosmic radiation. Is found, in addition, that the nature of the metal screen is of importance. It was determined also an effect of latitude from observations carried out at Florence, Brussels and Vienna. The investigation of the effect of the metal screen, by a simplified test without activation, has shown that in general the BiOCl precipitation is going on more rapidly when using the screen, and that there is a relation between the specific electrical conductivity of the metals used and the effect of screening.

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Résumé Depuis longtemps on a envisagé une relation entre les phénomènes atmosphériques, solaires et cosmiques et les phénomènes physicochimiques, biochimique set biologiques L'auteur a développé un test inorganique pour l'étude de cette relation. Il fait simplement précipiter par séries dans des conditions identiques, du BiOCl avec de l'eau normale et avec de l'eau activée. Le pourcentage des cas dans lesquels la précipitation marche plus vite dans l'eau activée (T%) est la réponse du test inorganique. L'auteur a conduit ses essais contemporairement au-dehors et au-dedans d'une chambre de cuivre. Les différences dans les résultats obtenus prouvent que les variations observées sont vraiment dûes aux influences exercées par des facteurs extérieurs.On a constaté qu'il existe a) une variation séculaire qui est probablement en rapport avec l'activité solaire, b) une variation annuelle qui peut être due au mouvement de la terre, c) plusieurs autres variations plus petites qui peuvent dépendre de différents éléments. On remarque des corrélations avec la pression atmosphérique, le gradient du potentiel électrique de l'air et l'intensité du rayonnement cosmique. D'autre part, on constate qu'il est important de tenir compte de la nature de l'écran métallique. On a aussi constaté qu'il existait un effet de latitude en comparant les observations faites à Florence, Bruxelles et Vienne. En utilisant un test simplifié sans activation (Test P) l'auteur a montré qu'en général la précipitation se produit plus rapidement au-dessous de l'écran et qu'il existe une relation entre la conductibilité électrique spécifique des métaux employés et l'effet observé.

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Mit 10 Textabbildungen.  相似文献   

Temperature,fluid content and rheology of localized ductile shear zones in subsolidus cooling plutons     

Alberto Ceccato  Philippe Goncalves  Giorgio Pennacchioni 《Journal of Metamorphic Geology》2020,38(8):881-903

Temperature and fluid content are critical parameters that control rock rheology and strain localization in the continental crust. Here, we determine by thermodynamic modelling the of localized ductile shearing during cooling of three different granitoid plutons: the Rieserferner and the Adamello plutons in the Italian Alps, and the Lake Edison pluton in the Sierra Nevada—USA. Shear zones exploited precursor joints, associated veins and alteration zones. and P−T phase diagram sections were computed with Perple_X in the system MnO−Na₂O−CaO −K₂O−FeO−MgO−Al₂O₃−SiO₂−H₂O−Fe₂O₃. The phase diagram sections show that the nucleation of the brittle precursors (joints, veins) occurred at T» 450°C at fluid-saturated conditions. Localized ductile shearing likely occurred at temperature ranging between 420 and 460°C evolving from initially fluid-saturated to fluid-undersaturated conditions in a closed system. In this temperature range, granitoid rocks are potentially subject to a series of retrograde metamorphic reactions replacing the load-bearing feldspars with weaker phyllosilicates. Metamorphic reactions occurred in spatial association with the precursory structures, leading to localized shearing. Decreasing temperature and fluid-undersaturated conditions likely hampered progressive strain accommodation in shear zones by slowing down metamorphic reactions, thermally activated dislocation creep processes, fluid-mediated deformation mechanisms and weakening mechanisms. Polyphase granitoid ultramylonite and mylonitic quartz veins have been affected differently by the fluid-undersaturated conditions of the system, as consequence of different dominant deformation mechanisms and syn-kinematic paragenesis during localized shearing. Localized ductile shearing in cooling plutons effectively occurs in a limited temperature range (420–460°C) in which the strain accommodation capacity of the shear zone is controlled by the negative feedback between the cooling rate, the kinetics of metamorphic reactions and deformation mechanisms, and the consumption of the limited amount of available fluids.  相似文献   

Chromite composition and platinum-group mineral assemblage in the Uktus Uralian-Alaskan-type complex (Central Urals,Russia)     

Giorgio?GarutiEmail author  Evgeny?V.?Pushkarev  Federica?Zaccarini  Roberto?Cabella  Elena?Anikina 《Mineralium Deposita》2003,38(3):312-326

Chromitite segregations in dunites of the Uktus Uralian-Alaskan-type complex (Central Urals, Russia) display large variation of the chromite composition: Cr/(Cr+Al)=0.46-0.77, Fe²⁺/(Fe²⁺+Mg)=0.28-0.66, and Fe³⁺/(Fe³⁺+Fe²⁺)=0.23-0.59. Three types of PGM assemblages have been recognized, varying in accordance with chromite composition: type I, dominated by Ru-Os-Ir (sulfides), is associated with magnesiochromite having Fe³⁺/(Fe³⁺+Fe²⁺)<0.30, in the southern dunite body. Type II, containing abundant Pt-Ir (alloys, minor sulfides), is found in magnesiochromite with Fe³⁺/(Fe³⁺+Fe²⁺)=0.40-0.44; type III, consisting of Ir-Rh-Pt-Pd (alloys, sulfarsenides, antimonides) in Fe-rich chromite having Fe²⁺/(Fe²⁺+Mg)=0.66 and Fe³⁺/(Fe³⁺+Fe²⁺)=0.59. Positive anomalies of Ir and Pt, and a negative peak of Ru characterize the PGE patterns of chromitites with type II and III PGM assemblages, whereas a positive Pt anomaly is observed in their dunite host. Intensive fractionation of Pt-Fe alloys in the Uktus chromitites reflects the anomalous behavior of Pt which is decoupled from Rh and Pd. Among other factors, the high iron activity and oxygen fugacity in the parent melt appear to exert a major control on precipitation of Pt-Fe alloys, below sulfur saturation. The strong Pt anomaly in chromitites from Uktus may indicate that Uralian-Alaskan-type magmas were derived from a Pt-rich mantle source.  相似文献   

Fault plane processes and mesoscopic structure of a strong-type seismogenic fault in tonalites (Adamello batholith, Southern Alps)   总被引：3，自引：3，他引：3  

Giulio Di Toro  Giorgio Pennacchioni   《Tectonophysics》2005,402(1-4):55

The Gole Larghe Fault is an exhumed paleoseismic fault crosscutting the Adamello tonalites (Italian Southern Alps). Ambient conditions of faulting were 9–11 km in depth and 250–300 °C. In the study area the fault accommodates 1100 m of dextral strike-slip over a fault thickness of 550 m. Displacement is partitioned into three hierarchically different sets of discrete subparallel cataclastic horizons (faults_1–2–3). Fault displacement is in the range of few centimeters (faults₃) to a maximum of a few tens of meters in major faults₁. Faults_1–2 nucleated on pre-existing joints, whereas faults₃ are newly generated fractures produced during slip along faults_1–2. Each fault within the Gole Larghe Fault records the same evolution with development of indurated cataclasites precursory to pseudotachylyte production. Pseudotachylytes are usually generated at the host rock/cataclasite boundary and within cataclasites the mean clast size decreases getting closer to pseudotachylyte fault veins. Pseudotachylytes and cataclasites have a similar chemical composition which is enriched in Loss On Ignition, K, Rb, Ba, U and Fe³⁺ compared to host rock.We envision two models for the evolution of the Gole Larghe Fault. In both models synkinematic fluid–rock interaction along a fault causes fault hardening by precipitation of abundant K-feldspar+epidote (and minor chlorite) in the cataclasite matrix conducive to final production of pseudotachylyte. In the first model, induration occurs progressively by differential precipitation related to fabric evolution in cataclasites. In the second model, induration occurs abruptly dependent on the development of full connectivity within the fault network and to fluid reservoir. Whatever the model, the Gole Larghe Fault represents a strong fault, where hardening processes resulted in a low displacement/fault thickness ratio and contrast with many mature weak faults where localized repeated seismic slip along the same weak horizons yields high displacement/fault thickness ratios.  相似文献   

Book Review: Geodynamics By D. L. Turcotte and G. Schubert, Cambridge University Press, New York, 2002, 456 p., U.S.110 (hb), 110 (hb), 45 (pb) ISBN 0-521-66186-2, 0-521-66624-4.     

Giorgio Ranalli 《Mathematical Geology》2005,37(1):125-126

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Constraints from geochemistry and Sr–Nd isotopes for the origin of albitite deposits from Central Sardinia (Italy)     

Francesca Castorina  Umberto Masi  Giorgio Padalino  Marcella Palomba 《Mineralium Deposita》2006,41(4):323-338

Major- and trace-element contents and Sr–Nd isotope ratios were determined in albitite, albitized and unaltered late-Variscan granitoid samples from the world-class Na-feldspar deposits of central Sardinia, Italy. The albite deposit of high economic grade has geological, textural, and chemical features typical of metasomatic alteration affecting the host granitoids. Albitization, locally accompanied by chloritization and epidotization, was characterized by strong leaching of Mg, Fe, K, and geochemically similar trace elements, and by a significant increase of Na. Ca, and P were moderately leached in the most metasomatized rocks. Other major (Si, Ti, Ca) and trace elements (U, Th, Y, and Zr), along with light (LREE) and middle (MREE) rare-earth elements, behaved essentially immobile at the deposit scale. The Nd-isotope ratios (0.512098 to 0.512248) do not provide information on the emplacement age of the unaltered late-Variscan granitoids. On the other hand, their Sr-isotope ratios fit an errorchron of 274±29 Ma (1σ error), in fair agreement with all published ages of Sardinian Variscan granitoids. The very low Rb content of albitized rocks precludes application of the Rb–Sr radiometric system to determine the age of albitization. The Sm–Nd system is not applicable either, because the ¹⁴³Nd/¹⁴⁴Nd ratios of albitized rocks and unaltered granitoids overlap. The overlap confirms that Sm and Nd were substantially immobile during albitization. On the other hand, the measured ⁸⁷Sr/⁸⁶Sr ratios of the albitized rocks are appreciably lower than those of the unaltered host granitoids, whereas, their initial Sr-isotope ratios are higher. This seems to suggest that a) albitization was induced by non-magmatic fluids rich in radiogenic Sr, and b) albitization occurred shortly after the granitoid emplacement. This conclusion is supported by Nd isotopes, because unaltered granitoids and albitites fit the same reference isochron at 274 Ma. The fluids acquired radiogenic Sr by circulation through the Lower Paleozoic metasedimentary basement. Specifically, it is estimated that Sr supplied by the non-carbonatic basement represents about 22 wt% of total Sr in albitite.  相似文献   

Geochemistry of the Submarine Gaseous Emissions of Panarea (Aeolian Islands, Southern Italy): Magmatic vs. Hydrothermal Origin and Implications for Volcanic Surveillance     

Giovanni Chiodini  Stefano Caliro  Giorgio Caramanna  Domenico Granieri  Carmine Minopoli  Roberto Moretti  Lavinia Perotta  Guido Ventura 《Pure and Applied Geophysics》2006,163(4):759-780

The marine sector surrounding Panarea Island (Aeolian Islands, South Italy) is affected by widespread submarine emissions of CO₂ -rich gases and thermal water discharges which have been known since the Roman Age. On November 3^rd, 2002 an anomalous degassing event affected the area, probably in response to a submarine explosion. The concentrations of minor reactive gases (CO, CH₄ and H₂) of samples collected in November and December, 2002 show drastic compositional changes when compared to previous samples collected from the same area in the 1980s. In particular the samples collected after the November 3^rd phenomenon display relative increases in H₂ and CO and a strong decrease in the CH₄ contents, while other gas species show no significant change. The interaction of the original gas with seawater explains the variable contents of CO₂, H₂S, N₂, Ar and He which characterize the different samples, but cannot explain the large variations of CO, CH₄ and H₂ which are instead compatible with changes in the redox, temperature and pressure conditions of the system. Two models, both implying an increasing input of magmatic fluids are compatible with the observed variations of minor reactive species. In the first one, the input of magmatic fluids drives the hydrothermal system towards atypical (more oxidizing) redox conditions, slowly pressurizing the system up to a critical state. In the second one, the hydrothermal system is flashed by the rising high-T volcanic fluid, suddenly released by a magmatic body at depth. The two models have different implications for volcanic surveillance and risk assessment: In the first case, the November 3^rd event may represent both the culmination of a relatively slow process which caused the overpressurization of the hydrothermal system and the beginning of a new phase of quiescence. The possible evolution of the second model is unforeseeable because it is mainly related to the thermal, baric and compositional state of the deep magmatic system that is poorly known.  相似文献   

Stresses and velocities in orogenic wedges with power-law rheology and linearly varying longitudinal strain rate     

Jiyang Liu  Giorgio Ranalli 《Journal of Structural Geology》1998,20(12):1611-1623

A two-dimensional analytical solution for stress, strain rate, and velocity is obtained for parallel-sided and wedge-shaped blocks with generalized viscous rheology (linearly viscous and power-law) deforming in plane strain. The main assumptions used in the derivation of the solution are that the material is incompressible, the longitudinal gradient in shear stress is much less than the vertical gradient of vertical normal stress, and the longitudinal strain rate varies linearly in the horizontal direction. Velocity boundary conditions are specified at the top of the block, and shear stress boundary conditions at the base of the block. In the one-dimensional case (where stress and strain rate do not vary in the longitudinal direction), the solution reduces to a well-known solution for the deformation of parallel-sided ice sheets [Nye, J. F. (1957) The distribution of stress and velocity in glaciers and ice sheets. Proceedings of the Royal Society of London A-239, 113–133]. The stress equilibrium for tapered wedges [Platt, J. P. (1986) Dynamics of orogenic wedges and the uplift of high-pressure metamorphic rocks. Geological Society of America Bulletin 97, 1037–1053] is a special case of the present stress solution. Implementation of the solution requires the subdivision of the wedge into vertical segments, and yields the tectonic normal and shear stresses that must be applied to the rear of a block with specified rheology in order to maintain a given longitudinal strain rate. The solution makes it possible to model deformation patterns analytically with longitudinally varying strain rate (including coeval compression and extension) and with vertical components of velocity reflecting the effects of underplating.  相似文献