Response to “Comment on Metallic Mineral Resources in the Twenty-First Century: I. Historical Extraction Trends and Expected Demand” by D. A. Singer and W. D. Menzie     

Alberto E. Patiño Douce 《Natural Resources Research》2016,25(1):93-96

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The island of Elba (Tuscany,Italy) at the crossroads of ancient trade routes: an archaeometric investigation of dolia defossa from the archaeological site of San Giovanni     

Rosarosa Manca  Laura Pagliantini  Elena Pecchioni  Alba P. Santo  Franco Cambi  Laura Chiarantini  Alessandro Corretti  Pilario Costagliola  Andrea Orlando  Marco Benvenuti 《Mineralogy and Petrology》2016,110(6):693-711

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A framework to assess quality and uncertainty in disaster loss data     

Xavier Romão  Esmeralda Paupério 《Natural Hazards》2016,83(2):1077-1102

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W–Au skarns in the Neo-Proterozoic Seridó Mobile Belt,Borborema Province in northeastern Brazil: an overview with emphasis on the Bonfim deposit     

João Adauto Souza Neto  Jean Michel Legrand  Marcel Volfinger  Marie-Lola Pascal  Philippe Sonnet 《Mineralium Deposita》2008,43(2):185-205

The Seridó Mobile Belt (SMB) is located in the Borborema Province in northeastern Brazil and consists of a gneiss basement (Archean to Paleo-Proterozoic), a metasedimentary sequence (marble, quartzites, and schists), and the Brasiliano igneous suite (both of Neo-Proterozoic age). In this region, skarns occur within marble and at the marble–schist contact in the metasedimentary sequence. Most of the skarn deposits have been discovered in the early 1940s, and since then, they have been exploited for tungsten and locally gold. Recently, the discovery of gold in the Bonfim tungsten skarn has resulted in a better understanding of the skarn mineralization in this region. The main characteristics of the SMB skarns are that they are dominantly oxidized tungsten skarns, with the exception of the Itajubatiba and Bonfim gold-bearing skarns, which are reduced based on pyrrhotite as the dominant sulfide, garnet with high almandine and spessartine component, and elevated gold contents. In the Bonfim deposit, pressure estimates indicate that the skarns formed at 10- to 15-km depth. The mineralized skarns present the prograde stage with almandine, diopside, anorthite, and actinolite-magnesio-hornblende, and titanite, apatite, allanite, zircon, and monazite as accessory minerals. The retrograde stage is characterized by alkali feldspar, clinozoisite–zoisite–sericite, calcite, and quartz. Scheelite occurs in four ore-shoots distributed within the marble and at the marble–schist contact. The main ore body is 5–120 cm wide and contains an average of 4.8-wt.% WO₃, which occurs in the basal marble–schist contact. Fold hinges appear to control the location of high-grade scheelite. The late-stage gold mineralization contains bismite (Bi₂O₃), fluorine-bearing bismite, native bismuth, bismuthinite (Bi₂S₃), and joseite [Bi₄(Te,S)₃], and also chlorite, epidote, prehnite, chalcopyrite, and sphalerite. This gold–bismuth–tellurium mineralization exhibits a typical late character and occurs as a black fine-grained mineral assemblage controlled by conjugate brittle-ductile faults (and extensional fractures) that crosscut not only the banding in prograde skarn but also the retrograde alkali feldspar and clinozoisite–zoisite–sericite assemblage. The Au–Bi–Te-bearing minerals are intergrown with retrograde epidote, prehnite, chlorite, chalcopyrite, and sphalerite, indicating that gold mineralization at Bonfim is linked to a late-stage skarn event. The polymetallic nature of the Bonfim deposit can be used as an important guide for the exploration of this type of skarn deposit in the Borborema Province, which potentially contains significant new, undiscovered gold and polymetallic deposits.  相似文献   

Cut Slopes in Clayey Soils: Consolidation and Overall Stability by Finite Element Method   总被引：1，自引：1，他引：0  

José Leitão Borges 《Geotechnical and Geological Engineering》2008,26(5):479-491

When a cut slope in a saturated clay is undertaken, a transient water flow occurs and stress transferences from the water to the soil skeleton take place in time (consolidation). Mainly in strongly overconsolidated clays, these stress transferences may determine swelling of soil and therefore reduction of its shear strength in time. However, the lowering of the water level associated to the cut increases effective mean stress, which may therefore counterbalance the above-mentioned effect. In the paper, the behaviour of a cut slope in an overconsolidated clay is analysed by a finite element program that incorporates the Biot consolidation theory (coupled analysis), with constitutive relations simulated by the p–q–θ critical state model. In addition, the variation in time of the overall stability is assessed with a computer program that uses the finite element results and formulations of the critical state soil mechanics. In order to achieve a more complex geotechnical interpretation of the problem, the analysis in time of the excess pore pressures, effective stresses, displacements and stress levels is also presented. Finally, comparisons of stability results are analysed by changing some parameters, namely the problem geometry (weight of excavated soil) and the over-consolidation ratio of the clay.  相似文献   

Comparison of spatial interpolation methods for the estimation of precipitation distribution in Distrito Federal,Brazil     

Pablo de Amorim Borges  Johannes Franke  Yumiko Marina Tanaka da Anunciação  Holger Weiss  Christian Bernhofer 《Theoretical and Applied Climatology》2016,123(1-2):335-348

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Digital thermal monitoring of the Amazon forest: an intercomparison of satellite and reanalysis products     

Juan C. Jiménez-Muñoz  Cristian Mattar  José A. Sobrino  Yadvinder Malhi 《International Journal of Digital Earth》2016,9(5):477-498

Remote sensing and climate digital products have become increasingly available in recent years. Access to these products has favored a variety of Digital Earth studies, such as the analysis of the impact of global warming over different biomes. The study of the Amazon forest response to drought has recently received particular attention from the scientific community due to the occurrence of extreme droughts and anomalous warming over the last decade. This paper focuses on the differences observed between surface thermal anomalies obtained from remote sensing moderate resolution imaging spectroradiometer (MODIS) and climatic (ERA-Interim) monthly products over the Amazon forest. With a few exceptions, results show that the spatial pattern of standardized anomalies is similar for both products. In terms of absolute anomalies, the differences between the two products show a bias near to zero with a standard deviation of around 0.2?K, although the differences can be up to 1?K over particular regions and months. Despite this general agreement, the proper filtering of MODIS daily values in order to construct a new monthly product showed a dramatic reduction in the number of reliable pixels during the rainy season, while for the dry season this reduction is only seen in Northern Amazonia.  相似文献   

Accuracy of ionospheric models used in GNSS and SBAS: methodology and analysis   总被引：8，自引：4，他引：4  

A. Rovira-Garcia  J. M. Juan  J. Sanz  G. González-Casado  D. Ibáñez 《Journal of Geodesy》2016,90(3):229-240

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Platinum-group element concentrations in pyrite from the Main Sulfide Zone of the Great Dyke of Zimbabwe     

R. Piña  F. Gervilla  S.-J. Barnes  T. Oberthür  R. Lunar 《Mineralium Deposita》2016,51(7):853-872

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Investigation of terrain illumination effects on vegetation indices and VI-derived phenological metrics in subtropical deciduous forests     

Lênio Soares Galvão  Fábio Marcelo Breunig  Thiago Sousa Teles  William Gaida  Rafaelo Balbinot 《地理信息系统科学与遥感》2016,53(3):360-381

We used RapidEye and Moderate Resolution Imaging Spectroradiometer (MODIS)/Terra data to study terrain illumination effects on 3 vegetation indices (VIs) and 11 phenological metrics over seasonal deciduous forests in southern Brazil. We applied TIMESAT for the analysis of the Enhanced Vegetation Index (EVI) and the Normalized Difference Vegetation Index (NDVI) derived from the MOD13Q1 product to calculate phenological metrics. We related the VIs with the cosine of the incidence angle i (Cos i) and inspected percentage changes in VIs before and after topographic C-correction. The results showed that the EVI was more sensitive to seasonal changes in canopy biophysical attributes than the NDVI and Red-Edge NDVI, as indicated by analysis of non-topographically corrected RapidEye images from the summer and winter. On the other hand, the EVI was more sensitive to terrain illumination, presenting higher correlation coefficients with Cos i that decreased with reduction in the canopy background L factor. After C-correction, the RapidEye Red-Edge NDVI, NDVI, and EVI decreased 2%, 1%, and 13% over sunlit surfaces and increased up to 5%, 14%, and 89% over shaded surfaces, respectively. The EVI-related phenological metrics were also much more affected by topographic effects than the NDVI-derived metrics. From the set of 11 metrics, the 2 that described the period of lower photosynthetic activity and seasonal VI amplitude presented the largest correlation coefficients with Cos i. The results showed that terrain illumination is a factor of spectral variability in the seasonal analysis of phenological metrics, especially for VIs that are not spectrally normalized.  相似文献