Thermal state and concentration of gas hydrate and free gas of Coyhaique,Chilean Margin (44°30′ S)     

I. Vargas-Cordero  U. Tinivella  F. Accaino  M.F. Loreto  F. Fanucci 《Marine and Petroleum Geology》2010

In the last decades gas hydrate occurrence along the Chilean continental margin has been well documented. In order to better define the seismic character of the hydrate-bearing sediments, we performed a detailed velocity analysis by using the pre-stack depth migration on part of multichannel reflection seismic line RC2901-734 located offshore Coyhaique.  相似文献   

Mantle degassing on a near shore volcano,SE Tyrrhenian Sea          下载免费PDF全文

Maria F. Loreto  Francesco Italiano  Davide Deponte  Lorenzo Facchin  Fabrizio Zgur 《地学学报》2015,27(3):195-205

The presence of a seamount‐like structure, located a few nautical miles offshore the Capo Vaticano Promontory (western Calabria, S Italy), was revealed by combined geophysical and geochemical investigation. The edifice covers ~55 km², with a top located at a depth of about 70 m below sea level, and consists mainly of a NW‐trending structure orthogonally interrupted by minor ridges, the largest of which is affected by extensional faults. The top of the edifice hosts active vents, injected fluids that have been investigated for dissolved volatiles. Gas analyses revealed high CO₂ and CH₄ contents, several orders of magnitude above the atmospheric‐type values expected for shallow, coastal marine waters, and a noteworthy enrichment in mantle‐derived ³He, which is an unambiguous indicator of the mantle origin of the fluids. Our results, combined with available data from the literature, suggest that the edifice is a tectonically controlled volcanic system, which presence near the Calabria region changes the role played by faults in the frame of the subduction process.  相似文献   

High-pressure displacive phase transition of a natural Mg-rich pigeonite     

Matteo Alvaro  Fabrizio Nestola  Fernando Cámara  M. Chiara Domeneghetti  Vittorio Tazzoli 《Physics and Chemistry of Minerals》2011,38(5):379-385

A high-pressure single-crystal X-ray diffraction study has been carried out on a P2₁/c natural Mg-rich pigeonite sample with composition ca. Wo₆En₇₆Fs₁₈ using a diamond anvil-cell. The unit-cell parameters were determined at 14 different pressures to 7.14 GPa. The sudden disappearance of the b-type reflections (h + k = odd) and a strong discontinuity (about 2.8%) in the unit-cell volume indicated a first-order P2₁/c–C2/c phase transition between 4.66 and 4.88 GPa. The P(V) data of the P2₁/c phase were fitted to 4.66 GPa by a third-order Birch–Murnaghan equation of state (BM3 EoS), whereas the limited number of experimental data collected within the C2/c phase between 4.88 and 7.14 GPa were fitted using the same equation of state but with K′ constrained to the value obtained for the P2₁/c fitting. The equation of state coefficients are V ₀ = 424.66(6) ų, K _T0 = 104(2) GPa and K′ = 8(1) for the P2₁/c phase, and V ₀ = 423.6(1) ų, K _T0 = 112.4(8) GPa, and K′ fixed to 8(1) for the C2/c phase. The axial moduli for a, b, and c for the P2₁/c phase were obtained using also a BM3-EoS, while for the C2/c phase only a linear calculation could be performed, and therefore the same approach was applied for comparison also to the P2₁/c phase. In general the C2/c phase exhibits axial compressibilities (β _c > β _a >> β _b) lower than those of the P2₁/c phase (β _b > β _c ≈ β _a; similar to those found in previous studies in clinopyroxenes and orthopyroxenes). The lower compressibility of the C2/c phase compared with that of the P2₁/c could be ascribed to the greater stiffness along the b direction. A previously published relationship between P _c and M2 average cation radius (i.r.) has been updated using all the literature data on P2₁/c clinopyroxene containing large cations at M2 site and our new data. The following weighted regression was obtained: P _c (GPa) = 26(4) ? 28(5) ×  i.r (Å), R ² = 0.97. This improved equation can be used to predict the critical pressure of natural P2₁/c clinopyroxene samples just knowing the composition at M2 site.  相似文献   

Comment on ‘Yamada H,Nakamura F,Watanabe Y,Murakami M and Nogami T. 2005. Measuring hydraulic permeability in a streambed using the packer test. Hydrological Processes 19: 2507–2524’     

Vittorio Di Federico  Rita Ugarelli 《水文研究》2008,22(17):3543-3544

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Thermal history of ALH 84001 meteorite by Fe2+‐Mg ordering in orthopyroxene     

M. Chiara Domeneghetti  Anna M. Fioretti  Fernando Cmara  Gianmario Molin  Vittorio Tazzoli 《Meteoritics & planetary science》2007,42(10):1703-1710

Abstract— A single orthopyroxene crystal from the Martian meteorite Allan Hills (ALH) 84001 was studied by X‐ray diffraction (XRD) and electron microprobe analysis (EMPA) to retrieve information about its thermal history. Both sets of data were used to measure the Fe²⁺‐Mg order degree between the M1 and M2 sites expressed by the distribution coefficient k_D. The 529 ± 30°C closure temperature (T_c) of the Fe²⁺‐Mg ordering process of ALH 84001 orthopyroxene (Fs₂₈) was calculated using Stimpfl (2005a, 2005b) ln k_D versus 1/T equation obtained for intermediate iron sample. At this T_c, the orthopyroxene cooling rate, calculated by Ganguly's (1982) numerical method, was 0.1 °C/day. This study puts new constraints on the last high‐temperature thermal episode recorded by orthopyroxene. With reference to the geological history (Treiman 1998), we ascribe this episode to the I3 event, and we interpret the T_c of 529 °C as a lower limit for this impact heating. Our data confirm that experimentally defined physical conditions for the formation of magnetite from decomposition of carbonates took place on the Martian surface during event I3.  相似文献   

Future dynamical evolution of the Neptune-Triton system. A new synthetic method of analysis     

Vittorio Banfi 《Earth, Moon, and Planets》1984,30(1):43-52

A new approach to the study of future dynamical evolution of the Neptune-Triton system is here presented. After the analytical development of the model, the final results are compared with those drawn by previous works on the same subject.  相似文献   

Life Cycle, Demography and Secondary Production of the Polychaete Hediste ­diversicolor in a Non-Polluted Estuary in the Bay of Biscay     

Loreto García-Arberas  & Ana Rallo 《Marine Ecology》2002,23(3):237-251

Abstract. Population dynamics and secondary somatic production data of a population of the polychaete Hediste diversicolor (O. F. Müller) are reported. Monthly samples were taken in a small muddy-sand flat in the Gernika estuary (Basque Country, North Iberian Peninsula) from May 1991 to May 1992. In addition to H. diversicolor abundance, temporal variation of the infauna and sediment conditions were analysed. Size measurements were employed to estimate H. diversicolor biomass and several cohorts were differentiated based on the size distribution. Secondary production was estimated based on cohort summation of growth increments following individual cohorts through time. Results are compared with those of other H. diversicolor populations located along the whole latitudinal gradient of distribution of the species.  相似文献   

GRIDA3—a shared resources manager for environmental data analysis and applications     

Fabrizio Murgia  Riccardo Biddau  Alessandro Concas  Roberto Demontis  Luca Fanfani  Zeno Heilmann  Cristian Lai  Giuditta Lecca  Eva Lorrai  Marino Marrocu  Vittorio Alessandro Marrone  Laura Muscas  Elisaveta Peneva  Andrea Piras  Massimo Pisu  Gabriella Pusceddu  Guido Satta  Daniela Theis  Andrea Vacca  Paolo Valera  Ana Melina Vallenilla Ferrara  Ernesto Bonomi 《Earth Science Informatics》2009,2(1-2):5-21

GRIDA3 (Shared Resources Manager for Environmental Data Analysis and Applications) is a multidisciplinary project designed to deliver an integrated system to forge solutions to some environmental challenges such as the constant increase of polluted sites, the sustainability of natural resources usage and the forecast of extreme meteorological events. The GRIDA3 portal is mainly based on Web 2.0 technologies and EnginFrame framework. The portal, now at an advanced stage of development, provides end-users with intuitive Web-interfaces and tools that simplify job submission to the underneath computing resources. The framework manages the user authentication and authorization, then controls the action and job execution into the grid computing environment, collects the results and transforms them into an useful format on the client side. The GRIDA3 Portal framework will provide a problem-solving platform allowing, through appropriate access policies, the integration and the sharing of skills, resources and tools located at multiple sites across federated domains.  相似文献   

Space–time correlation of earthquakes     

Patrizia Tosi  Valerio De Rubeis  Vittorio Loreto  Luciano Pietronero 《Geophysical Journal International》2008,173(3):932-941

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Small‐scale experimental simulation of talus evolution     

Fabio Vittorio De Blasio  May‐Britt Sæter 《地球表面变化过程与地形》2009,34(12):1685-1692

We investigated a small‐scale laboratory model of a talus slope evolution. Five different size classes of basaltic rock were selected and marked with different colours. Homogenized mixtures of grains of different sizes were dropped from a fixed height onto a tilted experimental board covered with a loose granular layer. This was conducted in a series of regular sequences, and the resulting distribution on the board was studied after each sequence. At the beginning of the experiment, the grains developed a longitudinal gradation similar to natural talus slopes, where small grains settle at the top while the large ones roll down to the distal part. However, after a transient period dominated by single‐particle dynamics on the inert granular medium, the evolution proved to be more variable than expected. Due to the continuous shower of falling grains, the shear stress at the bottom of the upper granular layer increased. This resulted initially in a slow creep down slope that finally collapsed in large avalanches homogenizing the material. The slides occurred at the boundary between a weaker layer created by migration of small grains through the interstices, and marked by a vertical transition between small and large grains. We compare the experimental findings with observations from natural talus slopes, and suggest that similar experiments may be helpful in understanding the evolution of taluses. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献