Origin of crystal-poor, differentiated magmas: insights from thermal gradient experiments     

Matteo Masotta  Carmela Freda  Mario Gaeta 《Contributions to Mineralogy and Petrology》2012,163(1):49-65

Crystal-poor, differentiated magmas are commonly erupted from shallow, thermally zoned magma chambers. In order to constrain the origin of these magmas, we have experimentally investigated crystallization, differentiation and crystal-melt separation in presence of a thermal gradient. Experiments have been designed taking advantage of the innate temperature gradient of the piston cylinder apparatus and carried out on a phonolitic system at 0.3 GPa and temperature ranging from 1,050 to 800°C. Crystallization degree and melt composition in experimental products vary as a function of the temperature gradient. In particular, melt composition differentiates from tephri-phonolite (starting material) to phonolite moving from the hotter, glassy zone (T ≤ 1,050°C) towards the cooler, heterogeneously crystallized zone (T ≤ 900°C) of the charge. The heterogeneously crystallized zone is made up of: (1) a crystal-rich, mushy region (crystallinity >30 vol%), (2) a rigid crystal framework (crystallinity ≤80 vol%) and (3) glassy belts of phonolitic glass at the top. Thermal gradient experiments picture crystallization, differentiation and crystal-melt separation processes occurring in a thermally zoned environment and reveal that relatively large volumes of crystal-poor melt (glassy belts) can originate as a consequence of the instability and collapse of the rigid crystal framework. Analogously, in thermally zoned magma chambers, the development and collapse of a solidification front may represent the controlling mechanism originating large volumes of crystal-poor, differentiated magmas.  相似文献   

Drainage network geometry versus tectonics in the Argentera Massif (French–Italian Alps)     

Adriano Ribolini  Matteo Spagnolo   《Geomorphology》2008,93(3-4):253-266

The Argentera Massif (French–Italian Alps), with its uniform lithology, was selected to evaluate how known Plio–Pleistocene tectonics have conditioned the drainage network geometry. The drainage network was automatically derived and ordered from a 10 m-resolution DEM. On hillshade images, alignments of morphological features were identified. The Massif was subdivided into 22 domains of 50 km² within which the directions of every river channel segment and the direction of the aligned morphological features were compared and contrasted with the strike of tectonic structures measured in the field. Results suggest that the Argentera drainage system is variously controlled by recent tectonics, depending on the Massif sector taken into account. In the NW sector, the vertical uplift is less because the strain has been accommodated in an oblique direction along a lateral thrust. In the SE sector, strain in a predominantly vertical direction along a frontal thrust has resulted in a major vertical displacement. Accordingly, the NW sector is characterized by (i) a strong geometric relationship between the main tectonic structures and the directions of river channels, (ii) longitudinal main rivers bordering the Massif, and (iii) a general trellis pattern within the domains.In the SE sector, the prolonged uplift has forced an original longitudinal drainage system to develop as a transverse system. This change has occurred by means of fluvial captures that have been identified by the presence of windgaps, fluvial elbows and knickpoints. At the domain scale, intense uplift of the SE sector has prompted the drainage pattern to evolve as a dendritic type with no clear influence of structure in the channel orientations.  相似文献   

Site characterization by seismic noise in Istanbul,Turkey     

Matteo Picozzi  Angelo Strollo  Stefano Parolai  Eser Durukal  Oguz Özel  Savas Karabulut  Jochen Zschau  Mustafa Erdik 《Soil Dynamics and Earthquake Engineering》2009

Single station seismic noise measurements were carried out at 192 sites in the western part of Istanbul, Turkey. This extensive survey allowed the fundamental resonance frequency of the sedimentary cover to be mapped, and identify areas prone to site amplification. The results are in good agreement with the geological distribution of sedimentary units, indicating a progressive decrease of the fundamental resonance frequencies from the northeastern part, where the bedrock outcrops, towards the southwestern side, where a thickness of some hundreds meters for the sedimentary cover is estimated. The particular distribution of fundamental resonance frequencies indicates that local amplification of the ground motion might play a significative role in explaining the anomalous damage distribution after the 17 August 1999 Kocaeli Earthquake.  相似文献   

HDR devices for the seismic protection of frame structures: Experimental results and numerical simulations     

Laura Ragni  Luigino Dezi  Andrea Dall'Asta  Graziano Leoni 《地震工程与结构动力学》2009,38(10):1199-1217

As part of a national research programme an experimental campaign was carried out on a real scale mock‐up consisting of a steel–concrete composite frame equipped with dissipative bracings, based on high damping rubber (HDR) devices. Free vibration tests, followed by force‐controlled and displacement‐controlled cyclic tests were performed. The experimental tests were aimed at studying the dynamic response of the coupled system in order to demonstrate the effectiveness of HDR devices in increasing the stiffness and dissipation capacity of the frame and investigating the ability of the constitutive HDR model proposed by the authors to predict the dynamic response of the coupled system. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Reconstruction and analysis of two long-term precipitation time series: Alpe Devero and Domodossola (Italian Western Alps)     

Guido Nigrelli  Matteo Collimedaglia 《Theoretical and Applied Climatology》2012,109(3-4):397-405

With this study, we analyzed two long-term precipitation time series recorded at Alpe Devero and Domodossola (Italian Western Alps) for two periods (1916–2010 and 1872–2010, respectively). The aims of the study were: to create the first precipitation time series covering more than 50?years for Alpe Devero, to extend and update the precipitation time series for Domodossola, to detect changes by means of trend analysis on the precipitation time series. After an accurate analysis of the metadata and the measurements recorded at each station, a trend analysis was performed on both datasets. The results showed a statistically significant decline in winter, summer, and annual precipitation at Alpe Devero and a nonsignificant decrease in seasonal and annual precipitation at Domodossola. Covering more than 90?years, the long-term precipitation time series at Alpe Devero and Domodossola represent unique data sets for this sector of Italian Western Alps. Continuing updating of the data could provide a useful resource for climate change studies in this area and, within a wider perspective, in Alpine regions.  相似文献   

Disperse Two-Phase Flows,with Applications to Geophysical Problems     

Luigi C. Berselli  Matteo Cerminara  Traian Iliescu 《Pure and Applied Geophysics》2015,172(1):181-196

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A User-Oriented Methodology for DInSAR Time Series Analysis and Interpretation: Landslides and Subsidence Case Studies     

Davide Notti  Fabiana Calò  Francesca Cigna  Michele Manunta  Gerardo Herrera  Matteo Berti  Claudia Meisina  Deodato Tapete  Francesco Zucca 《Pure and Applied Geophysics》2015,172(11):3081-3105

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Submarine landslides and the importance of the initial sediment composition for run-out length and final deposit   总被引：1，自引：0，他引：1  

Anders Elverhoi  Hedda Breien  Fabio V. De Blasio  Carl B. Harbitz  Matteo Pagliardi 《Ocean Dynamics》2010,60(4):1027-1046

Much remains to understand the dynamic processes during the flow of submarine landslides. A first relevant problem is to explain the extraordinary mobility of submarine landslides, which has no comparison in subaerial mass movement. Another challenging question is the apparent disparity between submarine landslides that remain compact for hundreds of kilometres and those that disintegrate during the flow, finally evolving into turbidity currents. This problem is linked to a central ongoing debate on the relative importance of turbidity currents versus submarine landslides in reshaping the continental margin. Based on three epitomic case studies and on laboratory experiments with artificial debris flows of various composition, we suggest a possible explanation for the disparity between compact and disintegrating landslides, identifying the clay-to-sand ratio as the key control parameter.  相似文献   

The Romagna Apennines,Italy: an eroded duplex     

A. Cerrina Feroni  L. Leoni  L. Martelli  P. Martinelli  G. Ottria  G. Sarti 《Geological Journal》2001,36(1):39-54

The study of clast composition carried out on the alluvial gravels of the Romagna Apennines of northern Italy has provided evidence for an extensive covering of allochthonous units (Ligurian nappe and Epiligurian succession) above the Miocene foredeep deposits (Marnoso‐Arenacea Formation), which has been subsequently eroded during the Late Miocene–Pleistocene uplift. This result is confirmed by the burial history outlined in the Marnoso‐Arenacea Formation through vitrinite reflectance and apatite fission‐track analyses. The Romagna Apennines represent, therefore, a regional tectonic window where the thrust system that displaced the Marnoso‐Arenacea Formation crops out. The geometric relations between this thrust system and the basal thrust of the Ligurian nappe, exposed at the boundaries of the Romagna Apennines (Sillaro Zone and Val Marecchia klippe), are consistent with a duplex structure. Thus, the Romagna Apennines thrust system is an eroded duplex. The duplex roof‐thrust corresponds to the surface of the synsedimentary overthrust of the Ligurian nappe on the Marnoso‐Arenacea Formation; the floor‐thrust is located in the pelagic pre‐foredeep deposits (Schlier Formation). Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

A lumped parameter model for time‐domain inertial soil‐structure interaction analysis of structures on pile foundations          下载免费PDF全文

Sandro Carbonari  Michele Morici  Francesca Dezi  Graziano Leoni 《地震工程与结构动力学》2018,47(11):2147-2171

The paper presents a lumped parameter model for the approximation of the frequency‐dependent dynamic stiffness of pile group foundations. The model can be implemented in commercial software to perform linear or nonlinear dynamic analyses of structures founded on piles taking into account the frequency‐dependent coupled roto‐translational, vertical, and torsional behaviour of the soil‐foundation system. Closed‐form formulas for estimating parameters of the model are proposed with reference to pile groups embedded in homogeneous soil deposits. These are calibrated with a nonlinear least square procedure, based on data provided by an extensive non‐dimensional parametric analysis performed with a model previously developed by the authors. Pile groups with square layout and different number of piles embedded in soft and stiff soils are considered. Formulas are overall well capable to reproduce parameters of the proposed lumped system that can be straightforwardly incorporated into inertial structural analyses to account for the dynamic behaviour of the soil‐foundation system. Some applications on typical bridge piers are finally presented to show examples of practical use of the proposed model. Results demonstrate the capability of the proposed lumped system as well as the formulas efficiency in approximating impedances of pile groups and the relevant effect on the response of the superstructure.  相似文献