Petrogenesis and geodynamic significance of silicic volcanism in the western Trans-Mexican Volcanic Belt: role of gabbroic cumulates     

Chiara Maria Petrone  Teresa Orozco-Esquivel  Luca Ferrari 《Contributions to Mineralogy and Petrology》2014,167(5):1-21

In the western Trans-Mexican Volcanic Belt voluminous silicic volcanism has been associated with the rifting of the Jalisco block from mainland Mexico. Rhyolitic volcanism started at 7.5 Ma after a major pulse of basaltic volcanism aged 11–8.5 Ma associated with slab detachment. This was followed by a second period, between 4.9 and 2.9 Ma, associated with rhyolitic domes and ignimbrite coexisting with basaltic volcanism. The similarity in rare earth element contents between basalts and rhyolites excludes a simple liquid line of descent. The low Ba and Sr contents and the ferroan character of the rhyolites suggest extensive fractional crystallization. Late Miocene–early Pliocene rhyolite Sr isotope values are only slightly more radiogenic than the basalts, whereas Nd isotope ratios are indistinguishable. We successfully modelled the 7.5–3 Ma silicic magmatism as a result of partial melting of crustal gabbroic complexes that we infer to have formed in the mid-lower crust due to the high-density Fe-enriched composition of the late Miocene basaltic volcanism. Slab rollback since ~7.5 Ma favoured decompression melting and arrival of additional mafic magmas that intruded in the lower crust. These basalts heated and melted the gabbroic complexes forming the silicic magmas, which subsequently underwent assimilation and fractional crystallization processes. The first silicic pulse was emplaced during a period of low tectonic activity. Extensional faulting since the Pliocene favours the eruption of both silicic magma and lesser amount of mafic lavas.  相似文献   

Probabilistic seismic hazard analysis at a strategic site in the Bay of Bengal   总被引：1，自引：1，他引：0  

Sara Cristina Teresa Trianni  Carlo Giovanni Lai  Erio Pasqualini 《Natural Hazards》2014,74(3):1683-1705

Probabilistic seismic hazard analysis (PSHA) along the route of an offshore pipeline for the transport of oil in the Bay of Bengal has been performed, in order to set up design parameters and identify possible geohazards. The complexity of geological and seismotectonic setting of the region where the pipeline is planned to be installed is the result of the interaction of the Indian, Eurasian and Burmese tectonic plates. In order to properly account for the intricate way by which these plates interact, a large area extending 450 km from the pipeline route has been considered for the compilation of a comprehensive earthquake catalogue, spanning the period 1663–2012 AD. Differently from earlier PSHA analyses conducted in the region based on assuming two-dimensional polygons as seismogenic provinces, this study adopted a seismotectonic source model which also includes for the first time a linear tectonic lineament representing the northward extension of the Sunda mega thrust, responsible for the large Sumatra–Andaman earthquake of 26 December 2004. Hazard computations have been performed over a grid of sites spaced 0.045° covering a rectangular area which contains the pipeline. Epistemic uncertainty in the hazard computations has been taken into account by a logic tree framework, incorporating different seismotectonic source models, maximum cut-off magnitude and ground-motion prediction equations. Horizontal median uniform hazard spectra and median uniform hazard spectra plus and minus one sigma on stiff ground have been calculated at the selected sites for different return periods. Peak ground acceleration with 10 % probability of exceedance in 50 years has been compared with values from previous hazard studies available for Bangladesh.  相似文献   

Assessment of the physico-mechanical behaviour of gypsum-lime repair mortars as a function of curing time     

Jesús Igea Romera  Sagrario Martínez-Ramírez  Pilar Lapuente  María Teresa Blanco-Varela 《Environmental Earth Sciences》2013,70(4):1605-1618

Gypsum-based mortars were widely used during the Mudejar artistic period in Spain from the 12th to 16th century. During restoration works, compatibility between the new repair mortars and the original components is essential for an adequate intervention on the monument. The increasing interest of knowing the properties of the gypsum-lime-based mortars for restoration purposes justifies the research carried out. Different mortars compatible with traditional building materials were elaborated by varying the binder proportions, the type of aggregates, the binder/aggregate ratios and the curing time. The main goal of this paper is to characterize the mechanical behaviour and the pore structure of the mortars as a function of curing time. The influence between the different variables used to prepare the mortars and the development of the carbonation process over time is also considered. Mechanical strength and porosity measurements as well as X-ray diffraction and thermal analysis were performed after curing times of 1, 28 and 90 days. The results obtained confirmed a progressive increase in mechanical strength linked to the carbonation of the mortars prepared. Less lime binder and also aggregate contents showed the highest rise in strength over time, related to the highest initial porosity which favoured the carbon dioxide flow. The use of siliceous aggregates (GL-QS mortars) obtained the best results in the development of physico-mechanical properties over curing time. The knowledge obtained from the studied mortars provides practical information to establish a suitable mortar mixture for restoration works on historic buildings and modern architecture where gypsum-lime-based mortars are used.  相似文献   

Vestan lithologies mapped by the visual and infrared spectrometer on Dawn     

Eleonora Ammannito  M. Cristina De Sanctis  Fabrizio Capaccioni  M. Teresa Capria  F. Carraro  Jean‐Philippe Combe  Sergio Fonte  Alessandro Frigeri  Steven P. Joy  Andrea Longobardo  Gianfranco Magni  Simone Marchi  Thomas B. McCord  Lucy A. McFadden  Harry Y. McSween  Ernesto Palomba  Carle M. Pieters  Carol A. Polanskey  Carol A. Raymond  Jessica M. Sunshine  Federico Tosi  Francesca Zambon  Christopher T. Russell 《Meteoritics & planetary science》2013,48(11):2185-2198

We present global lithological maps of the Vestan surface based on Dawn mission's Visible InfraRed (VIR) Spectrometer acquisitions with a spatial sampling of 200 m. The maps confirm the results obtained with the data set acquired by VIR with a spatial sampling of 700 m, that the reflectance spectra of Vesta's surface are dominated by pyroxene absorptions that can be interpreted within the context of the distribution of howardites, eucrites, and diogenites (HEDs). The maps also partially agree with the ground and Hubble Space Telescope observations: they confirm the background surface being an assemblage of howardite or polymict eucrite, as well as the location of a diogenitic‐rich spot; however, there is no evidence of extended olivine‐rich regions in the equatorial latitudes. Diogenite is revealed on the Rheasilvia basin floor, indicating that material of the lower crust/mantle was exposed. VIR also detected diogenites along the scarp of Matronalia Rupes, and the rims of Severina and a nearby, unnamed crater, and as ejecta of Antonia crater. The diogenite distribution is fully consistent with petrological constraints; although the mapped distribution does not provide unambiguous constraints, it favors the hypothesis of a magma ocean.  相似文献   

Hydrogeochemistry approach to the identification of flow components under the descending limb conditions of a hydrograph (Corbeira stream,Spain)     

Juciene Andrade Figueiredo  Eldemar Albuquerque Menor  Maria Teresa Taboada-Castro  Maria Mercedes Taboada-Castro  Luís Drude Lacerda 《Applied Geochemistry》2012

This paper presents a method based on hydrogeochemical signatures for the identification of flow components, from the descending limb to the baseflow, without the direct support of hydrographs. The proposed model was built using chemical analysis of waters from a small agro-forestry catchment having a temperate climate. The sampling was performed every 15 days at the Corbeira stream outlet, from 2004 to 2008. A statistical approach was used with particulate P/dissolved P (PP/DP) values, resulting in a global histogram, within which mini-Gaussian distributions were highlighted. The mean of each group of highlighted PP/DP values, as well as all other selected analytical parameters, were calculated and plotted in Cartesian diagrams. The results showed the hydrogeochemical signatures of the Corbeira stream in the descending limb to baseflow conditions. Scatterplots of the migration of particulate matter showed linear regressions forming α ≠ 0 to the X-axis, while dissolved compounds showed parallel linearity (α = 0) in relation to the same axis. Deflections in the linear behavior point to significant changes in the chemical concentrations from different types of aqueous inputs. Flow components in the descending limb show distinct ranges along the X-axis: the mean PP/DP values. The ranges varying from 3.3 to 2.0 correspond to its upper phases from 2.0 to 0.9 suggests mixtures between inflows and from 0.9 to 0.3 denote subsurface flow dominance. Finally, PP/DP < 0.3 indicates exclusive baseflow conditions. These intervals are specific to the Corbeira catchment as a consequence of its geographical characteristics and should be numerically different from the proposed method if applied to other catchments. However, this method remains valid for application in other small catchments as the PP/DP ranges in the descending limb are defined by the relative behavior between the linear correlations from the hydrogeochemical concentrations plotted in a Cartesian diagram.  相似文献   

Non‐Metabolic Uptake of Al3+ by Dead Leaves of Rubus ulmifolius: Comparison With Metabolic Bioaccumulation Data          下载免费PDF全文

Pablo Lodeiro  Marta López‐García  Luz Herrero  José L. Barriada  Roberto Herrero  Leticia Carro  Teresa Vilariño  Pilar Rodríguez  Manuel E. Sastre de Vicente 《洁净——土壤、空气、水》2016,44(2):154-161

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Methods for point source analysis in high energy neutrino telescopes     

Jim Braun  Jon Dumm  Francesco De Palma  Chad Finley  Albrecht Karle  Teresa Montaruli   《Astroparticle Physics》2008,29(4):299-305

Neutrino telescopes are moving steadily toward the goal of detecting astrophysical neutrinos from the most powerful galactic and extragalactic sources. Here we describe analysis methods to search for high energy point-like neutrino sources using detectors deep in the ice or sea. We simulate an ideal cubic kilometer detector based on real world performance of existing detectors such as AMANDA, IceCube, and ANTARES. An unbinned likelihood ratio method is applied, making use of the point spread function and energy distribution of simulated neutrino signal events to separate them from the background of atmospheric neutrinos produced by cosmic ray showers. The unbinned point source analyses are shown to perform better than binned searches and, depending on the source spectral index, the use of energy information is shown to improve discovery potential by almost a factor of two.  相似文献   

Coastal Pollution Mitigation with Lime and Zero Valent Iron     

John L. Daniels  Gautham P. Das  Maria Teresa Serrano Hernandez  Sunyoung Bae 《Marine Georesources & Geotechnology》2013,31(3):183-191

The Taiwan Strait region has many miles of coastline, and the Taiwan Straits Tunnel (TST) project faces many potential pollution problems as construction proceeds through sensitive areas. Conventional approaches for pollution mitigation require further examination. The recent development of nanoscale particle technology has shown distinct advantages for contaminant attenuation and ground improvement. This paper is focused on trace metals and is part of the overall effort to develop the nanoscale particle technology. Trace metals in ground and surface waters represent a continued threat to human and ecological health. One of the difficulties in removing toxic concentrations of trace metals from solution is the variable oxidation state and amphoteric nature of multiple constituents. In particular, while cationic metals (e.g., Pb²⁺, Cd²⁺, Ni²⁺) may be rendered less mobile under high pH conditions, anionic metals (e.g., AsO₄ ^3?, CrO₄ ^2?, SeO₄ ^2?)may become more mobile. The objective of this research was to evaluate the sorption of both cationic and anionic trace elements, including arsenic (As), cadmium (Cd), chromium (Cr) and selenium (Se) under batch conditions. Mixtures of a local residual soil were tested alone and in combination with lime and zero valent iron. It was hypothesized that lime would raise the pH and precipitate positively charged metals while zero valent iron would create reducing conditions favorable to the immobilization of negatively charged metals. Results indicate that the use of lime and/or zero valent iron can increase the sorption capacity of soil. Compared to the baseline soil, sorption capacity increased with addition of lime for arsenic and cadmium while it decreased for chromium and selenium. In the case of zero valent iron addition, sorption capacity increased for cadmium, chromium and selenium, while showing no change for arsenic. When both lime and zero valent iron were used, the sorption capacity increased for all metals tested. These results suggest that the combined use of lime and zero valent iron may serve as an alternative treatment technology for removing trace metals from contaminated water systems.  相似文献   

Alluvial terraces on the Ionian coast of northern Calabria, southern Italy: Implications for tectonic and sea level controls     

Gaetano Robustelli  Federica Luc  Fabio Corbi  Teresa Pelle  Francesco Dramis  Giandomenico Fubelli  Fabio Scarciglia  Francesco Muto  Domenico Cugliari 《Geomorphology》2009,106(3-4):165-179

In this paper we present the results of an integrated geomorphological, pedological and stratigraphical study carried out along the Ionian coast of northern Calabria (southern Italy). This area is characterised by the occurrence of five orders of alluvial terraces that are striking features of the landscape, where large and steep catchments debouch from the mountain front to the hilly coastal belt.Field investigations indicate that the deposits of all five terraces are suggestive of shallow gravel-bed braided streams.On the basis of the age of the Pleistocene substratum and morphostratigraphic correlation with marine terraces cropping out in the nearby areas, each order has been associated to specific marine oxygen isotope stages.Consequently, we focused on the interplay of allocyclic factors influencing stream aggradation/degradation. Soil features and other climatic proxies suggest that climate didn't play an important role with respect to tectonic and base-level changes in controlling fluvial dynamics.In particular, we recognised that during the middle Pleistocene the study area experienced a period of subaerial landscape modelling, as suggested by the thick and complex alluvial sequence of the highest terrace (T1). The onset of regional uplift marks a change in the geomorphic scenario, with tectonic and eustatically driven changes in base-level working together in causing switches in fluvial aggradational/erosional phases (T2–T5 terraces). Because of the uplift, river dissection occurred during phases of sea level fall, whereas aggradation phases occurred during periods of climate amelioration (sea level rise) just before highstands were attained.As a consequence, the stepped terraces in the study area reflect the interplay between tectonics (uplift) and sea level changes, in which terraces define episodes of relative sea level fall during the late Quaternary.  相似文献   

Sulfur as a binding agent of aggregates in explosive eruptions     

Teresa Scolamacchia  Donald B. Dingwell 《Bulletin of Volcanology》2014,76(10):1-12

The 2013 eruption of Pavlof Volcano, Alaska began on 13 May and ended 49 days later on 1 July. The eruption was characterized by persistent lava fountaining from a vent just north of the summit, intermittent strombolian explosions, and ash, gas, and aerosol plumes that reached as high as 8 km above sea level and on several occasions extended as much as 500 km downwind of the volcano. During the first several days of the eruption, accumulations of spatter near the vent periodically collapsed to form small pyroclastic avalanches that eroded and melted snow and ice to form lahars on the lower north flank of the volcano. Continued lava fountaining led to the production of clastogenic lava flows that extended to the base of the volcano, about 3–4 km beyond the vent. The generation of fountain-fed lava flows was a dominant process during the 2013 eruption; however, episodic collapse of spatter accumulations and formation of hot spatter-rich granular avalanches was a more efficient process for melting snow and ice and initiating lahars. The lahars and ash plumes generated during the eruption did not pose any serious hazards for the area. However, numerous local airline flights were cancelled or rerouted, and trace amounts of ash fall occurred at all of the local communities surrounding the volcano, including Cold Bay, Nelson Lagoon, Sand Point, and King Cove.  相似文献