Mineralogy and trace-element geochemistry of the high-grade iron ores of the Águas Claras Mine and comparison with the Capão Xavier and Tamanduá iron ore deposits, Quadrilátero Ferrífero, Brazil     

Carlos Alberto Spier  Sonia Maria Barros de Oliveira  Carlos Alberto Rosière  José Domingos Ardisson 《Mineralium Deposita》2008,43(2):229-254

Several major iron deposits occur in the Quadrilátero Ferrífero (QF), southeastern region of Brazil, where metamorphosed and heterogeneously deformed banded iron formation (BIF) of the Cauê Formation, regionally called itabirite, was transformed into high- (Fe >64%) and low-grade (30%?2O₃, with a higher amount of detrimental impurities, especially MnO, in the soft ore. Both hard and soft ores are depleted in trace elements. The high-grade ores at the Águas Claras Mine have at least a dual origin, involving hypogene and supergene processes. The occurrence of the hard, massive high-grade ore within “fresh” dolomitic itabirite is evidence of its hypogene origin. Despite the contention about the origin of the dolomitic itabirite (if this rock is a carbonate-rich facies of the Cauê Formation or a hematite–carbonate precursor of the soft high-grade ore), mineralogical and geochemical features of the soft high-grade ore indicate that it was formed by leaching of dolomite from the dolomitic itabirite by meteoric water. The comparison of the Águas Claras, Capão Xavier and Tamanduá orebodies shows that the original composition of the itabiritic protore plays a major role in the genesis of high- and low-grade soft ores in the QF. Under the same weathering and structural conditions, the dolomitic itabirite is the more favorable to form high-grade deposits than siliceous itabirite. Field relations at the Águas Claras and Capão Xavier deposits suggest that it is not possible to form huge soft high-grade supergene deposits from siliceous itabirite, unless another control, such as impermeable barriers, had played an important role. The occurrence in the Tamanduá Mine of a large, soft, high-grade orebody formed from siliceous itabirite and closely associated with hypogene hard ore suggests that large, soft, high-grade orebodies of the Quadrilátero Ferrífero, which occur within siliceous itabirite, have a hypogene contribution in their formation.  相似文献   

Reply to the discussion of: “Carbonatites in a subduction system: The Pleistocene alvikites from Mt. Vulture (Southern Italy)” by M. D'Orazio, F. Innocenti, S. Tonarini and C. Doglioni (Lithos 98, 313–334) by F. Stoppa, C. Principe and P. Giannandrea     

Massimo D'Orazio  Fabrizio Innocenti  Sonia Tonarini  Carlo Doglioni 《Lithos》2008,103(3-4):557-561

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Influence of tropical Pacific SST on seasonal precipitation in Colombia: prediction using El Niño and El Niño Modoki     

Samir Córdoba-Machado  Reiner Palomino-Lemus  Sonia Raquel Gámiz-Fortis  Yolanda Castro-Díez  María Jesús Esteban-Parra 《Climate Dynamics》2015,44(5-6):1293-1310

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The Bazar Ophiolite of NW Iberia: a relic of the Iapetus–Tornquist Ocean in the Variscan suture     

Sonia S. Martínez  Axel Gerdes  Ricardo Arenas  Jacobo Abati 《地学学报》2012,24(4):283-294

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Quasi-periodic fluctuations in the Greenland–Iceland–Norwegian Seas region in a coupled climate model   总被引：1，自引：1，他引：0  

Sonia R. Gamiz-Fortis  Rowan T. Sutton 《Ocean Dynamics》2007,57(6):541-557

We report an analysis of the mechanisms responsible for interannual variability in the Greenland–Iceland–Norwegian (GIN) Seas in a control integration of the HadCM3 coupled climate model. Interannual variability in sea surface temperature (SST) and sea surface salinity (SSS) is dominated by a quasi-periodic ∼7-year signal. Analyses show that the mechanism involves a competition between convection and advection. Advection carries cold, fresh, Arctic water over warm, salty, Atlantic water, while convection periodically mixes these two water masses vertically, raising SST. Convection is able to raise SST because of the presence of a subsurface temperature maximum. The GIN Seas convection in HadCM3 is forced by wind stress anomalies related to the North Atlantic Oscillation (NAO). The consequent SST anomalies feedback positively to force the atmosphere, resulting in a weak spectral peak (at ∼7 years) in GIN Seas sea level pressure. Although there is no evidence of a similar oscillation in reality, key aspects of the simulated mechanism may be relevant to understanding variability in the real GIN Seas. In particular, the potential for increases in convection to raise SST offers a possible new explanation for increases in SST that occurred between the 1960s and the late 1980s/early 1990s. These SST increases may have contributed to the observed sea-ice retreat. In addition, a positive feedback between GIN Seas SST and the atmosphere could contribute to the persistence of the NAO, potentially helping to explain its red spectrum or recent northeastward shift.

Sonia R. Gamiz-FortisEmail:

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Stratigraphy,age and petrography of the Beni Issef successions (External Rif; Morocco): Insights for the evolution of the Maghrebian Chain   总被引：1，自引：0，他引：1  

Angelida Di Staso  Vincenzo Perrone  Sonia Perrotta  Mohamed Najib Zaghloul  Michel Durand-Delga 《Comptes Rendus Geoscience》2010,342(9):718-730

In the Beni Issef Massif, nearly 30 km west of Chefchaouen (Morocco), the thickest post-nappe succession within the Rifian sector of the Maghrebian Chain seals the tectonic contact between the Intrarifian External Tanger and Loukkos Units, related to the Rifian External Domain. This succession is very important for the reconstruction of the deformation timing of the Rifian Maghrebids. The age of its base, in fact, is an important constraint for defining an upper boundary to the stacking of both the Intrarifian and Maghrebian Flysch Basin Units, because clasts fed by the Melloussa and Numidian Flysch Nappes are abundant in the conglomerate layers. Field and biostratigraphic analyses pointed out the presence of a Lower Beni Issef Fm, unconformable on the Intrarifian External Tanger and Loukkos Units, and an Upper Beni Issef Fm, unconformable on both the Intrarifian Units and the Lower Beni Issef Fm. The Lower Beni Issef Fm, 150 m thick, consists of lenticular conglomerates with huge blocks in a marly-clayey matrix, followed by marls and minor sandstones. It deposited in a siliciclastic platform, shows a fining upward trend and is affected by metre- to hectometre-sized, locally reversed, folds. Samples collected 45–50 m above the base of the formation resulted not older than Late Tortonian in age, but an older age for the base of the formation cannot be excluded. The Upper Beni Issef Fm, up to 550 m thick, starts with coarse conglomerates followed by medium- to coarse-grained well-bedded sandstones and by grey-blue marls and mudrocks. It indicates deposition in a channelized marine delta, with evolution towards pro-delta pelites, and shows sub-horizontal or gently dipping beds towards the east. Biostratigraphic data indicate a probable Messinian age for this formation. The composition of the arenites of both Lower Beni Issef and Upper Beni Issef Fms is quartzolithic and all samples show a notable content of monocrystalline well-rounded quartz and sedimentary lithic fragments. Detrital modes, all falling in the Quartzose Recycled and Transitional Recycled fields, suggest a provenance from recycling of sedimentary successions, easily recognizable in the Flysch Basin and External Units, mainly the Numidian Nappe sandstones. A Tortonian age of the Lower Beni Issef Fm would agree with the Late Serravallian age of the uppermost beds of the External Tanger Unit and indicate that the most probable age for the stacking of the Intrarifian Units falls in the Late Serravallian-Middle Tortonian time span. The Lower Beni Issef Fm was involved in a compressive tectonic phase testified by north-south striking folds. Later, probably during Messinian, the Upper Beni Issef Fm deposited in a younger intramontane basin, resting on both the Intrarifian Units and the Lower Beni Issef Fm. Successively, the Upper Beni Issef Fm was passively transported piggyback on top of the fold and thrust belt during later tectonic evolution of the Rifian Maghrebids. This tectonic evolution results quite similar to that recognized in the Tellian and Sicilian Maghrebids and also in the southern Apennines.  相似文献   

Impact of soil map specifications for European climate simulations     

Benoit P. Guillod  Edouard L. Davin  Christine Kündig  Gerhard Smiatek  Sonia I. Seneviratne 《Climate Dynamics》2013,40(1-2):123-141

Soil physical characteristics can influence terrestrial hydrology and the energy balance and may thus affect land–atmosphere exchanges. However, only few studies have investigated the importance of soil textures for climate. In this study, we examine the impact of soil texture specification in a regional climate model. We perform climate simulations over Europe using soil maps derived from two different sources: the soil map of the world from the Food and Agricultural Organization and the European Soil Database from the European Commission Joint Research Center. These simulations highlight the importance of the specified soil texture in summer, with differences of up to 2 °C in mean 2-m temperature and 20 % in precipitation resulting from changes in the partitioning of energy at the land surface into sensible and latent heat flux. Furthermore, we perform additional simulations where individual soil parameters are perturbed in order to understand their role for summer climate. These simulations highlight the importance of the vertical profile of soil moisture for evapotranspiration. Parameters affecting the latter are hydraulic diffusivity parameters, field capacity and plant wilting point. Our study highlights the importance of soil properties for climate simulations. Given the uncertainty associated with the geographical distribution of soil texture and the resulting differences between maps from different sources, efforts to improve existing databases are needed. In addition, climate models would benefit from tackling unresolved issues in land-surface modeling related to the high spatial variability in soil parameters, both horizontally and vertically, and to limitations of the concept of soil textural class.  相似文献   

A multi-physics ensemble of regional climate change projections over the Iberian Peninsula     

Sonia Jerez  Juan Pedro Montavez  Juan Jose Gomez-Navarro  Raquel Lorente-Plazas  Juan Andres Garcia-Valero  Pedro Jimenez-Guerrero 《Climate Dynamics》2013,41(7-8):1749-1768

This study illustrates the sensitivity of regional climate change projections to the model physics. A single-model (MM5) multi-physics ensemble of regional climate simulations over the Iberian Peninsula for present (1970–1999) and future (2070–2099 under the A2 scenario) periods is assessed. The ensemble comprises eight members resulting from the combination of two options of parameterization schemes for the planetary boundary layer, cumulus and microphysics. All the considered combinations were previously evaluated by comparing hindcasted simulations to observations, none of them providing clearly outlying climates. Thus, the differences among the various ensemble members (spread) in the future projections could be considered as a matter of uncertainty in the change signals (as similarly assumed in multi-model studies). The results highlight the great dependence of the spread on the synoptic conditions driving the regional model. In particular, the spread generally amplifies under the future scenario leading to a large spread accompanying the mean change signals, as large as the magnitude of the mean projected changes and analogous to the spread obtained in multi-model ensembles. Moreover, the sign of the projected change varies depending on the choice of the model physics in many cases. This, together with the fact that the key mechanisms identified for the simulation of the climatology of a given period (either present or future) and those introducing the largest spread in the projected changes differ significantly, make further claims for efforts to better understand and model the parameterized subgrid processes.  相似文献   

A Policy-enabling framework for the ex-ante evaluation of marine protected areas     

R. Quentin Grafton  Sonia AkterTom Kompas 《Ocean & Coastal Management》2011,54(6):478-487

A marine protected area (MPA) potentially generates a wide range of consumptive use, non-consumptive use and non-use values that include: critical habitat protection, conservation of marine biodiversity, recovery of threatened and endangered marine species, increased recreational benefits and increased biomass of harvested marine species. To help assess whether such values exceed the potential costs of MPAs, this paper provides a policy-enabling framework that reviews the existing theoretical and practical instruments and approaches that can be used in the ex-ante evaluation of MPAs. This framework is in three parts. First, a range of alternative monetary and non-monetary techniques to estimate three key economic benefits of MPAs: consumptive, non-consumptive use and non-use values are presented. Second, three decision protocols that can be applied to determine the desirability of establishing MPAs are described. Third, caveats of these approaches and the necessity to accommodate social needs of the communities are provided. The framework shows that biological and ecological considerations together with economic viability and socio-economic factors can and should be taken into account when deciding about when and where to establish MPAs and of what size.  相似文献   

Seismic vulnerability and risk assessment: case study of the historic city centre of Coimbra, Portugal   总被引：5，自引：4，他引：1  

Romeu Vicente  Sonia Parodi  Sergio Lagomarsino  Humberto Varum  J. A. R. Mendes Silva 《Bulletin of Earthquake Engineering》2011,9(4):1067-1096

Seismic risk evaluation of built-up areas involves analysis of the level of earthquake hazard of the region, building vulnerability and exposure. Within this approach that defines seismic risk, building vulnerability assessment assumes great importance, not only because of the obvious physical consequences in the eventual occurrence of a seismic event, but also because it is the one of the few potential aspects in which engineering research can intervene. In fact, rigorous vulnerability assessment of existing buildings and the implementation of appropriate retrofitting solutions can help to reduce the levels of physical damage, loss of life and the economic impact of future seismic events. Vulnerability studies of urban centres should be developed with the aim of identifying building fragilities and reducing seismic risk. As part of the rehabilitation of the historic city centre of Coimbra, a complete identification and inspection survey of old masonry buildings has been carried out. The main purpose of this research is to discuss vulnerability assessment methodologies, particularly those of the first level, through the proposal and development of a method previously used to determine the level of vulnerability, in the assessment of physical damage and its relationship with seismic intensity. Also presented and discussed are the strategy and proposed methodology adopted for the vulnerability assessment, damage and loss scenarios for the city centre of Coimbra, Portugal, using a GIS mapping application.  相似文献