Magma-induced strain localization in centrifuge models of transfer zones   总被引：1，自引：0，他引：1  

Giacomo Corti  Marco Bonini  Francesco Mazzarini  Mario Boccaletti  Fabrizio Innocenti  Piero Manetti  Genene Mulugeta  Dimitrios Sokoutis 《Tectonophysics》2002,348(4)

Scaled centrifuge experiments have been used to investigate the dynamic relations between deformation and magma distribution in rift-related transfer zones. The physical models were built using suitable analogue materials, such as sand to represent the brittle upper crust, various kinds of silicone mixtures to simulate the lower crust and upper mantle and glycerol to reproduce magma. Models simulated the development of transfer zones across pre-existing glycerol reservoirs placed at the base of the analogue continental crust. In plan view, different geometries, dimensions and positions of subcrustal reservoirs were reproduced in three different sets of experiments; to compare results, models were also performed without magma-simulating glycerol.Set 1 experiments, incorporating a narrow rectangular glycerol reservoir, show that the low-viscosity material is able to localise deformation into the overlying crust, giving rise to discrete transfer zones. This concentrated surface deformation corresponds at depth to major magma accumulation. Set 2 experiments, with an initial wide squared glycerol reservoir, show instead that deformation is distributed across the whole model surface, corresponding at depth to relatively minor magma accumulation. Set 3 experiments explored various positions of a small squared reservoir that invariably localised faulting in the overlying analogue brittle crust at the onset of model deformation.The overall model behaviour suggests that magma distribution at depth can effectively control the strain distribution in the overlying crust and the deformative pattern of transfer zones. Strain distribution, in turn, may control magma emplacement as localized deformation would favour major accumulation of magma at transfer zones. Coupled to a strong thermal weakening of the country rocks, this process may ultimately lead to a positive feedback interaction between magma and deformation.  相似文献   

NADPH: Phenanthrenequinone oxidoreductase in channel catfish (Ictalurus punctatus)     

Bruce M. Hasspieler  Richard T. Di Giulio 《Marine environmental research》1995,39(1-4)

The toxicity of certain polycyclic aromatic hydrocarbons has been related to the phenomenon of oxidative stress. Recent studies in our laboratory have demonstrated that 9,10-phenanthrenequinone (PQ) is an efficient redox cycling agent in cytosols of several organs of the channel catfish (Ictalurus punctatus). Stomach cytosol demonstrated a high level of dicoumarol-sensitive PQ reduction which was at least tenfold greater than that seen in kidney, liver or gill. In the presence of stomach cytosol, PQ stimulated production of Superoxide union in-vitro at rates several fold higher than did menadione, a model redox active quinone. The active component from stomach cytosol has been purified, and is termed NADPH: phenanthrenequinone oxidoreductase, which the authors believe represents a novel quinone-reducing enzyme in this species.  相似文献   

The evolution of the Western Ligurian Flysch Units and the role of mud diapirism in ancient accretionary prisms (Maritime Alps,Northwestern Italy)     

Dr. A. Di Giulio 《International Journal of Earth Sciences》1992,81(3):655-668

The Western Ligurian Flysch Units represent an Upper Cretaceous to Paleogene accretionary prism overthrust onto the paleo-European continental margin during the collisional stages of the Alpine orogeny (Eocene). Their precollisional evolution has been reconsidered according to the data collected through extensive field mapping, the study of lowgrade metamorphism and by considering more strictly the processes documented in modern convergent zones.The proposed model involves chaotic facies produced by the flow of muddy sediments along decollement surfaces (diapiric melange) with the growth of mud volcanoes into an accreting wedge progressively shifting toward the European continental margin.

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Zusammenfassung Der westliche Ligurische Flysch repräsentiert die Entwicklung eines Akkretionskeiles während des Kreide-Paleogens, das auf den europäischen Kontinentalrand während der Kollisionsphase der alpidischen Orogenese (Eozän) überschoben wurde. Die Entwicklung vor der Kollision wird neu gedeutet auf der Basis ausgedehnter geologischer Felduntersuchungen, dem Studium der niedrig gradigen Metamorphose und anhand von Vergleichen mit heutigen konvergenten Zonen.Das vorgeschlagene Modell interpretiert das Erscheinen der chaotischen Fazies als Diapirismus von nur teilweise verfestigten Sedimenten und deren Umlagerung nahe Diskontinuitätsflächen im Inneren eines Akkretionprismas, das in Richtung des europäischen Kontinents wandert.

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Résumé Les flyschs de la Ligurie occidentale représentent un prisme d'accrétion du Crétacé-Paléogène charrié sur la marge continentale européenne pendant les phases de collision de l'orogenèse alpine (Eocène). Leur évolution anté-collision est reconsidérée sur la base de nouvelles données provenant du levé de terrain d'une vaste région, de l'étude du métamorphisme de degré faible et de l'application plus rigoureuse des enseignements fournis par les zones de convergence actuelles.Le modèle proposé envisage la production de facies à texture chaotique par flux diapirique de sédiments non consolidés le long de surfaces de décollement, à l'intérieur d'un prisme d'accrétion qui migre progressivement vers la marge continentale européenne.

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New Constraints on Ages of Glasses Proposed as Reference Materials for Fission-Track Dating     

Marinella A. Laurenzi  Maria Laura Balestrieri  Giulio Bigazzi  Julio C. Hadler Neto  Pedro J. Iunes  Pio Norelli  Massimo Oddone  Ana Maria Osorio Araya  José G. Viramonte 《Geostandards and Geoanalytical Research》2007,31(2):105-124

New analyses have been performed in order to enhance the data-set on the independent ages of four glasses that have been proposed as reference materials for fission-track dating. The results are as follows. Moldavite - repeated ⁴⁰Ar/³⁹Ar age determinations on samples from deposits from Bohemia and Moravia yielded an average of 14.34 ± 0.08 Ma. This datum agrees with other recent determinations and is significantly younger than the ⁴⁰Ar/³⁹Ar age of 15.21 ± 0.15 Ma determined in the early 1980s. Macusanite (Peru) -four K-Ar ages ranging from 5.44 ± 0.06 to 5.72 ± 0.12 Ma have been published previously. New ⁴⁰Ar/³⁹Ar ages gave an average of 5.12 ± 0.04 Ma. Plateau fission-track ages determined using the IRMM-540 certified glass and U and Th thin films for neutron fluence measurements agree better with these new ⁴⁰Ar/³⁹Ar ages than the previously published ages. Roccastrada glass (Italy) - a new ⁴⁰Ar/³⁹Ar age, 2.45 ± 0.04 Ma, is consistent with previous determinations. The Quiron obsidian (Argentina) is a recently discovered glass that has been proposed as an additional reference material for its high spontaneous track density (around 100 000 cm^-2). Defects that might produce "spurious" tracks are virtually absent. An independent ⁴⁰Ar/³⁹Ar age of 8.77 ± 0.09 Ma was determined and is recommended for this glass. We believe that these materials, which will be distributed upon request to fission-track groups, will be very useful for testing system calibrations and experimental procedures.  相似文献   

Origin and emplacement of ultramafic–mafic intrusions in the Erro-Tobbio mantle peridotite (Ligurian Alps, Italy)     

Giulio Borghini  Elisabetta Rampone  Laura Crispini  Roberto De Ferrari  Marguerite Godard 《Lithos》2007,94(1-4):210-229

The Erro-Tobbio peridotites (Voltri Massif, Ligurian Alps) represent subcontinental lithospheric mantle tectonically exhumed during Permo–Mesozoic extension of the Europe–Adria lithosphere. Previous studies have shown that exhumation started during Permian times, and occurred along kilometer-scale lithospheric shear zones which enhanced progressive deformation and recrystallization from spinel- to plagioclase-facies conditions. Ongoing field and petrologic investigations have revealed that the peridotites experienced, during uplift, a composite history of diffuse melt migration and multiple episodes of ultramafic–mafic intrusions. In this paper we present the results of field, structural and petrologic–geochemical investigations into a sector of the Erro-Tobbio peridotite unit that preserves well this multiple intrusion history. Melt impregnation in the peridotites is evidenced by significant plagioclase enrichment and crystallization of unstrained orthopyroxene replacing kinked mantle olivine and clinopyroxene; impregnating melts were thus opx-saturated. Melt–rock interaction caused chemical changes in mantle minerals (e.g. Al decrease and REE increase in cpx; Ti and Cr# enrichment in spinel). Nevertheless, clinopyroxenes still exhibit LREE depletion (Ce_N/Sm_N = 0.006–0.011), indicating a depleted signature for the percolating melts. Melt impregnation was thus related to diffuse porous flow migration of depleted MORB-type melt fractions that modified their compositions towards opx saturation by mantle–melt interaction during ascent. The impregnated peridotites are intruded by a hectometer-scale stratified cumulate body, mostly consisting of troctolites and plagioclase wehrlites, showing gradational, interfingered contacts with the host mantle rocks. Subsequent intrusion events are revealed by the occurrence of olivine gabbros as decameter-wide lenses, variably thick (centimeter- to meter-scale) dykes and thin dykelets, which crosscut both the peridotite foliation and the magmatic layering in the cumulates. Overall, major and trace element compositions of minerals in the intrusives indicate that they represent variably differentiated cumulus products crystallized from rather primitive N-MORB-type aggregated melts. Slightly more evolved compositions are shown by olivine gabbros, relative to the troctolites and plagioclase wehrlites of the cumulate body. Mineral chemistry features (e.g. the Fo–An correlation and high Na, Ti, Mg# in cpx) indicate that the studied intrusive rocks crystallized at moderate pressure conditions (3–5 kbar, i.e. 9–15 km depth). Our study thus points to a progressive transition from porous flow melt migration to emplacement of magmas in fractures, presumably related to progressive change of lithospheric mantle rheology during extension-related uplift and cooling.  相似文献   

Radiation Physics     

Pirronello  Valerio  Manicó  Giulio 《Earth, Moon, and Planets》1998,80(1-3):261-283

Earth, Moon, and Planets -  相似文献   

Gravity-Accommodated ‘Structural Wedges’ Along Thrust Ramps: A Kinematic Scheme of Gravitational Evolution     

Iovine  Giulio  Tansi  Carlo 《Natural Hazards》1998,17(3):195-224

In active geodynamic areas, such as the Italian Southern Apennines, the specific structural conditions have a profound effect on both the superficial and deep gravitational evolution of slopes. Chain sectors commonly exhibit structural complexities due to the superimposition, in space and time, of diverse tectonic stress fields. In this paper, attention is focused on particular structural configurations, connected to the tectonic quaternary phases that have affected the Southern Apennines, constituting a peculiar type of lateral spread gravitational deformations – which have not been previously described.The study area is characterized by regional roughly east-verging overthrusts (Holigo–Miocene). Superimposed on these, is a system of transpressive thrust ramps (Quaternary), connected to the activity of strike-slip faults. The latest tectonic phase, still active, has been characterized by an extensional stress field, which has produced differentiated uplifts along normal faults. All these factors have encouraged an intense and widespread processes of erosion, the creation of considerable relief energy and the development of both superficial and deep gravitational phenomena.It has been ascertained that the late extensional phases favoured gravitational reactivations (with normal movements) along those most recent thrust ramps whose attitude was kinematically consistent with the main extension direction of the stress field. Such reactivations were accommodated by antithetic neo-formational structures – these are also characterized by normal kinematics. Overall, such mechanisms lead to the individuation of wedge-shaped rock portions delimited by the normally reactivated thrust ramps, on one side, and by the antithetic structures, on the other.Structural wedges represent a particular type of lateral spread phenomena. On the basis of their orientation with respect to the orography, three typical situations have been defined: (1) wedge perpendicular to the ridge; (2) wedge parallel to the ridge; (3) wedge oblique to the ridge.In this paper three Calabrian case studies, exemplifying the above-mentioned situations, are described. The same framework can be applied to sectors of chain with an analogous structural setting, for a better understanding of the kinematic features of observed gravitational phenomena.  相似文献   

Pollution effects of the Tuy River on the central Venezuelan coast: Anthropogenic organic compounds and heavy metals in Tivela mactroidea     

Rudolf Jaffe  Ivan Leal  Jose Alvarado  Piero Gardinali  Jos Sericano 《Marine pollution bulletin》1995,30(12):820-825

Bivalve samples were collected at seven sampling stations located between the town of Machurucuto and the Bay of Higuerote, Venezuela, covering approximately 70 km of coastline. Samples were collected both east and west of the Tuy River mouth, which has a plume known to move in a north-westerly direction. Petroleum hydrocarbons, both aliphatic (n-alkanes and UCM) and polyaromatic (PAHs), were detected and quantified in the samples. These hydrocarbons were found to be primarily derived from fossil fuels. Halogenated organics consisted mostly of polychlorinated biphenyls (PCBs) and some chlorinated pesticides, primarily of the DDT group. Heavy metals such as Pb, Cu, Ni, Zn, Cr and Cd were analysed in the samples. The results clearly show the influence of the Tuy River plume on the water quality of the coastal zone, particularly that located west of the river mouth. One sampling station, located just east of the river mouth, also showed significant influence from the river plume.  相似文献   

Book reviews     

Martin Jaeggi  Giulio P. Genoni 《Aquatic Sciences - Research Across Boundaries》1989,51(1):84-85

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AN ION PROBE CONTRIBUTION TO RARE EARTH ELEMENT INVESTIGATION OF GABBRO GOG-1 USING SECONDARY ION MASS SPECTROMETRY   总被引：1，自引：0，他引：1  

Luisa OTTOLINI  Piero BOTTAZZI  Riccardo VANNUCCI  Massimo ODDONE 《Geostandards and Geoanalytical Research》1992,16(1):13-19

An updated REE measurement of Gabbro GOG-1 was carried out by means of secondary ion mass spectrometry (SIMS). The availability of high amount of rock powder allowed the sample to be well ground and homogenized before analysis. Fused glass pellets were employed for SIMS investigations. REE data were compared with new ICP-AES and NAA analyses. REE results from all employed analytical techniques show good agreement and are consistent with in-situ SIMS measurements of REE in major mineral phases forming GOG-1. Extensive homogeneity tests seem to confirm the possibility to using this rock as a reference material for earth sciences.  相似文献