Hercynite as the product of staurolite decomposition in the contact aureole of Vedrette di Ries,eastern Alps,Italy     

Bernardo Cesare 《Contributions to Mineralogy and Petrology》1994,116(3):239-246

Metapelitic hornfelses in the contact aureole of the Vedrette di Ries pluton exhibit the terminal decomposition of Zn-poor Fe-staurolite in a muscovite-quartz-free domain. The reaction takes place only within coarsegrained sillimanite that has replaced andalusite porphyroblasts during prograde metamorphism. The product is a gahnite-poor hercynitic spinel, which occurs as very small grains closely associated in space with resorbed staurolite. Microstructural observations indicate that bereynite growth postdates the pseudomorphs of sillimanite after andalusite. The textural evidence for a genetic relationship between hercynite and staurolite is confirmed by the identical Fe/Mg/Zn ratios of the two minerals, which causes the collinearity of hercynite, staurolite and Al₂SiO₅ in FeO–MgO–ZnO–Al₂O₃–SiO₂–H₂O composition space (FMZASH), and indicates hercynite formed by the reaction: Fe-staurolite = 3.85hercynite + 5.1sillimanite + 2.55quartz + 2H₂O Staurolite inclusions within andalusite did not break down to form hercynite, indicating a kinetic control, as well as little overstepping of the equilibrium conditions, of the reaction forming hercynite. Assuming overstepping did not occur, modelling of the reaction with existing thermodynamic data in the simplified FASH system suggests that the terminal breakdown of staurolite to form hercynite occurred at 2.5–3.75kbar and 585–655°C.  相似文献   

Volcanic emissions and atmospheric pollution:A study of nanoparticles     

Erika M.Trejos  Luis F.O.Silva  James C.Hower  Eriko M.M.Flores  Carlos Mario González  Jorge E.Pachón  Beatriz H.Aristizábal 《地学前缘(英文版)》2021,12(2):746-755

The influence of emissions of an active volcano on the composition of nanoparticles and ultrafine road dust was identified in an urban area of the Andes.Although many cities are close to active volcanoes,few studies have evaluated their influence in road dust composition.Air quality in urban areas is significantly affected by nonexhaust emissions(e.g.road dust,brake wear,tire wear),however,natural sources such as volcanoes also impact the chemical composition of the particles.In this study,elements from volcanic emissions such as Si>Al>Fe>Ca>K>Mg,and Si-Al with K were identified as complex hydrates.Similarly,As,Hg,Cd,Pb,As,H,Cd,Pb,V,and salammoniac were observed in nanoparticles and ultrafine material.Mineral composition was detected in the order of quartz>mullite>calcite>kaolinite>illite>goethite>magnetite>zircon>monazite,in addition to salammoniac,a tracer of volcanic sources.The foregoing analysis reflects the importance of carrying out more studies relating the influence of volcanic emissions in road dust in order to protect human health.The road dust load(RD₁₀)ranged between 0.8 and 26.8 mg m^?2in the city.  相似文献   

Spatial structure of directional wave spectra in hurricanes     

Bernardo Esquivel-Trava  Francisco J. Ocampo-Torres  Pedro Osuna 《Ocean Dynamics》2015,65(1):65-76

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Resilience and seismic risk perception at school: a geoethical experiment in Aiello Calabro,southern Italy     

Francesco De Pascale  Marcello Bernardo  Francesco Muto  Dante Di Matteo  Valeria Dattilo 《Natural Hazards》2017,86(2):569-586

The last few years have seen the debate on the geoethics of environmental and climatic protection growing to include resilience as a central idea within this new discipline, which holds many similarities with geography. Resilience analysis often looks at the capacity to re-establish conditions of equilibrium within a system which has been hit by a serious shock, e.g. a natural or man-made disaster. Geoethics works, in tandem with geological analyses and the geography of risk, to inform a population and develop integrated risk management in such a way as to strengthen a community’s resilience. The aim of this work is to study some people’s capacity to overcome what was potentially a disastrous event and, through a process of reconstruction, turn it into an occasion for growth. The experiment, carried out in the primary and middle schools in Aiello Calabro (Calabria, southern Italy), was conducted on the basis of the belief that there is a close relationship between a population’s having a realistic understanding of the risk of such an event, e.g. an earthquake, and high levels of resilience. We also tried to gain an insight into the relationship that may exist between resilience in primary and secondary school children and methods of coping which give an appropriate management of seismic risk. To be more precise, we try to discover whether there is a link between good/appropriate resilience and good/appropriate risk management.  相似文献   

Geochemical and petrological constraints on rear-arc magma genesis processes in Ecuador: The Puyo cones and Mera lavas volcanic formations   总被引：1，自引：0，他引：1  

Géraldine Hoffer  Jean-Philippe Eissen  Bernardo Beate  Erwan Bourdon  Michel Fornari  Jo Cotten 《Journal of Volcanology and Geothermal Research》2008

The Puyo scoria cones and the Mera lava flows, two newly recognized volcanic formations dated between Late Pliocene to Middle Pleistocene, extend the limits of the Ecuadorian rear-arc volcanic province some 100 km to the south. The Puyo scoria cones have erupted K-rich absarokites containing olivine, diopside and phlogopite, whereas the Mera lava flows display a basic andesite composition, with olivine and minor augite phenocrysts. In addition to high contents in LILE, LREE and HFSE, the Puyo absarokites exhibit many characteristics of primitive melts, namely high Cr (590–310 ppm) and Ni (330–154 ppm) contents, high Mg# (64–70) and they contain forsteritic olivine (Fo_82–89). The composition of the most primary Puyo absarokite was used in petrogenetic models, in order to constrain the genesis of these high-K magmas. Major and trace elements models, as well as isotopic data, indicate that the source of Puyo magmas is a hydrated phlogopite- and garnet-bearing lherzolite. Phlogopite crystallization in the mantle wedge is triggered by the metasomatism by 3–5% of a SiO₂-, H₂O-rich liquid generated by slab melting. Partial melting of the subducted oceanic crust beneath Ecuador is allowed by the subduction of the young and warm Carnegie Ridge, which modifies the thermal regime of the Benioff zone. A low degree (1–4%) of partial melting of the metasomatized mantle wedge, leaving a variable garnet (4–7%) ± phlogopite (0–4%) lherzolitic residual assemblage, leads to the compositions of the entire Puyo absarokite series and is consistent with previous petrogenetic models developed for the Ecuadorian volcanic arc. Indeed, the homogeneity of isotopic data across the arc suggests a similar source for the whole Ecuadorian magmas.  相似文献   

Discrimination of agricultural crops in a tropical semi-arid region of Brazil based on L-band polarimetric airborne SAR data   总被引：4，自引：0，他引：4  

Wagner F. Silva  Bernardo F.T. Rudorff  Antonio R. Formaggio  Waldir R. Paradella  Jos C. Mura 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(5):458-463

Recent articles are indicating that polarimetric data provide significantly more information than conventional or multi-polarized images, particularly due to the additional phase information. The objective of this paper is to evaluate the multi-polarized and fully polarimetric L-band airborne SAR-R99B data, in terms of their capability to distinguish among different agricultural crops in the western part of Bahia State, Brazil. Emphasis was given to coffee, cotton and pasture crops which were at well developed growing stages. Discrimination among crops was carried out using graphical analysis of mean backscatter values. Crop classification was performed for single and multiple polarizations, and fully polarimetric images with a classifier that uses the contextual Iterated Conditional Modes–ICM algorithm. The investigation confirmed the potential of L-band multi-polarized and polarimetric airborne SAR-R99B data to distinguish and classify agricultural crops in the tropical condition of the test-site. In addition, it clearly indicated the gradual and considerable improvement that was achieved going from single to three polarizations and from multi-polarized to fully polarimetric images.  相似文献   

Stock and losses of trace metals from salt marsh plants     

Isabel Caçador  Miguel Caetano  Bernardo Duarte  Carlos Vale 《Marine environmental research》2009,67(2):75-82

Pools of Zn, Cu, Cd and Co in the leaf, stem and root tissues of Sarcocornia fruticosa, Sarcocornia perennis, Halimione portulacoides and Spartina maritima were analysed for a Tagus estuary (Portugal) salt marsh. Pools of Cu and Cd in the salt marsh were higher in spring/summer, indicating a net uptake of these metals during the growing season. Standing stocks of Zn, Cu, Cd and Co in the leaf and stem biomass of S. fruticosa, S. perennis and H. portulacoides showed a strong seasonal variation, with higher values recorded in autumn. The metal-containing leaves and stems that shed in the autumn become metal-containing detritus. The amount of this material washed out from the total marsh area (200 ha) was estimated as 68 kg of Zn, 8.2 kg of Cu, 13 kg of Co and 0.35 kg of Cd. The high tidal amplitude, a branched system of channels and semi-diurnal tidal cycle greatly favour the export of the organic detritus to adjoining marsh areas.  相似文献   

Comparison of the spatio-temporal distribution of the roughneck shrimp Rimapenaeus constrictus (Stimpson, 1874) (Crustacea,Penaeoidea) from monthly samples collected 20 years apart: Effects of a marine protected area in southeastern Brazil     

Veronica P. Bernardes  Aline N. Sousa  Camila H. Bernardo  Gustavo M. Teixeira  Rogério C. Costa  Fernando L. Mantelatto  Adilson Fransozo 《Marine Ecology》2020,41(5):e12605

This study was motivated by the data about a Rimapenaeus constrictus population from Ubatuba Bay, obtained in the 1990s, and by the establishment of a marine protected area (MPA) in the same region in 2008. We obtained comparable data about the distribution and abundance of this species collected 20 years apart, to evaluate the effectiveness of the MPA, for its preservation and possible changes in the populational profile. Biotic and abiotic data were obtained monthly, in September 1995–August 1996 (period 1 = 1ºP), and in September 2016–August 2017 (period 2 = 2ºP), from five transects within Ubatuba Bay. In total, 710 and 2,362 individuals were caught in the 1^oP and 2^oP, respectively. Despite this increase in abundance, aspects of the spatial distribution did not change substantially. The high abundance recorded at 5 m of depth was probably due to the creation of the MPA and to the accumulation of detritus at this depth. The high abundance seen in the transect sheltered from waves may be related to sediment heterogeneity, which was higher in this transect, and to the fact that this area is naturally protected from fisheries. In the 1ºP, the highest abundances were recorded in spring and summer, whereas in the 2ºP, they occurred in autumn and winter. This change may be explained by the entrance of the South Atlantic Central Water (SACW), which drives shrimps towards shallower areas. During the 2ºP, a fishing ban occurred in autumn (March 1st until May 31st), which is also when the SACW retreats and water temperature and salinity increase. These two factors combined may have been responsible for the increased shrimp abundance. In conclusion, both conservation practices (MPA and fishing ban) along with the existence of an area naturally protected from fisheries seem to have positively affected the population of R. constrictus, leading to an increase in abundance over the 20-year interval.  相似文献   

On the ecohydrology of the Yucatan Peninsula: Evapotranspiration and carbon intake dynamics across an eco‐climatic gradient          下载免费PDF全文

Jorge M. Uuh‐Sonda  Hugo A. Gutiérrez‐Jurado  Bernardo Figueroa‐Espinoza  Luis A. Méndez‐Barroso 《水文研究》2018,32(18):2806-2828

The hydrology and productivity of the ecosystems of the Yucatan Peninsula (YP) are highly constrained by two factors: (a) the lack of surface drainage networks due to the existence of a highly permeable and connected karstic aquifer roughly the size of the peninsula and (b) a climatic gradient that leads to a transition from seasonally dry deciduous and sub‐deciduous tropical forests, in the north‐western and central parts of the Peninsula, to evergreen forests, in the southern and eastern parts. As a result, surface water fluxes of the YP are restricted to evapotranspiration (ET) that are tightly coupled to ecosystems health and gross primary productivity (GPP). The magnitude and seasonal variation of these fluxes are sensitive to climatic variability and perturbations caused by extreme events such as droughts and tropical storms that are frequent in the YP. In this study, we assess the spatio‐temporal dynamics of ET and GPP above average dry and wet conditions through time series analyses of 15 years of remotely sensed data from both Moderate Resolution Imaging Spectroradiometer and Tropical Rainfall Measuring Mission satellite products. Our results show that ET and GPP follow a regional moisture and temperature gradient that highly controls the distribution of ecosystems within the peninsula. We observe that ET and GPP are in phase with the rainy season in the deciduous forests, but for the evergreen forests, only the GPP is in phase. Additionally, and with the exception of droughts on deciduous ecosystems of the northern part of the YP, the productivity of these ecosystems shows a legacy effect, responding more to a defined trajectory (wetting or drying on the previous years), rather than to punctual extreme climatic events. This has implications on the resilience of these ecosystems to natural perturbations of climate. Comparisons between deciduous and evergreen forest indicate that both types of ecosystems have different plant water use strategies in response to hydrologic variability.  相似文献   

Entropy theory for analysing water resources in northeastern region of Brazil   总被引：1，自引：1，他引：0  

Vicente de P. Rodrigues da Silva  Adelgicio F. Belo Filho  Vijay P. Singh  Rafaela S. Rodrigues Almeida  Bernardo B. da Silva  Inajá F. de Sousa 《水文科学杂志》2017,62(7):1029-1038

Using the Shannon entropy, the space–time variability of rainfall and streamflow was assessed for daily rainfall and streamflow data for a 10-year period from 189 stations in the northeastern region of Brazil. Mean values of marginal entropy were computed for all observation stations and entropy maps were then constructed for delineating annual and seasonal characteristics of rainfall and streamflow. The Mann-Kendall test was used to evaluate the long-term trend in marginal entropy as well as relative entropy for two sample stations. The marginal entropy values of rainfall and streamflow were higher for locations and periods with the highest amounts of rainfall. The entropy values were higher where rainfall was higher. This was because the probability distributions of rainfall and the resulting streamflow were more uniform and less skewed. The Shannon entropy produced spatial patterns which led to a better understanding of rainfall and streamflow characteristics throughout the northeastern region of Brazil. The total relative entropy indicated that rainfall and streamflow carried the same information content at annual and rainy season time scales.  相似文献