BOLETIN GEOLOGICO Y MINERO最新文献

{"title":"Significance of the “cut off-average grade-tonnage” sensitivity analysis in mining projects","authors":"L. D. L. Torre, J. A. Espí","doi":"10.21701/BOLGEOMIN.130.1.008","DOIUrl":"https://doi.org/10.21701/BOLGEOMIN.130.1.008","url":null,"abstract":"espanolEl Analisis de Sensibilidad referido a la relacion ley-tonelaje en un proyecto de inversion minera resulta un paso reconocido en todos los estandares de calidad actuales. Sin embargo, despues de presentarlo, apenas se comenta ni critican los resultados. El trabajo analiza mas de 50 proyectos actuales agrupados por modelos metalogeneticos de cobre y oro, encontrando caracteristicas propias en las curvas de evolucion del tonelaje al variar la ley de corte. Ademas, al considerar las categorias de calidad de informacion en los recursos, los calificados como inferidos, suelen denotar la falta de esta calidad. Tambien, el trabajo trata de encontrar una explicacion de las diferencias que aparecen entre las tipologias que contienen un gran volumen de recursos y con variaciones no bruscas de sus leyes, con otras tipologias con anisotropias muy declaradas y fuertes controles estructurales. EnglishThe sensitivity analysis applied to the grade-tonnage relationship in mining projects is a recognized stage in all existing quality standards. However, once presented, the results are hardly commented on or criticized. This study analyzes more than 50 projects grouped by copper and gold metallogenetic models which find their own characteristics in the tonnage evolution curves by varying the cut-off grade. In addition, when considering the categories of quality in information regarding resources, those which are classified as inferred usually denote a lack of quality. This study also offers an explanation about the behaviour of ore typologies with important resources and non-abrupt grade variations, with other typologies with well-declared anisotropies and strong structural controls.","PeriodicalId":45458,"journal":{"name":"BOLETIN GEOLOGICO Y MINERO","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49266569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison of elemental concentration in near-surface late Holocene sediments and precipitation regimes of the Yucatán Peninsula (Mexico): a preliminary study.","authors":"P. Roy, N. Torrescano-Valle, D. D. S. Escarraga-Paredes, A. A. Vela-Peláez, R. Lozano-Santacruz","doi":"10.21701/BOLGEOMIN.129.4.006","DOIUrl":"https://doi.org/10.21701/BOLGEOMIN.129.4.006","url":null,"abstract":"espanolPaleoclimate research in the Yucatan Peninsula of Mexico has mainly involved fossil pollen preserved in sedimentary archives whilst geochemistry has received limited attention. In this study, we compared concentrations of K, Ti, Fe, Ca and Sr in 35 near-surface late Holocene sediments collected from different permanent and seasonal water bodies across the peninsula with mean annual precipitation of 600-1600 mm in order to explore the relationship between concentrations of inorganic elements and precipitation. The calcareous provenance has a diluting effect and sediments have less K, Ti and Fe (associated with clastics) and more Ca and Sr (associated with carbonate and evaporite) compared to the Upper Continental Crust. Individual elements and ratios of K/Ca, Ti/Ca and Fe/Ca in samples with minimal clastics did not show any relationship with precipitation. Average values of elemental ratios in sediments with more clastics increase as the mean annual precipitation increases. However, the sampling protocol and presence of most of the sampled water bodies being in a single precipitation cluster (i.e. 1200-1400 mm/year) did not allow a complete evaluation of the potential correlation between precipitation and elemental ratios. Considering that the concentration of Ti is low in sediments of the limestone-rich Yucatan Peninsula and Fe is mobile in anoxic depositional environments, the K/Ca ratio can be used as a preliminary proxy to evaluate precipitation in sedimentary records. EnglishLa investigacion paleoclimatica en la Peninsula de Yucatan (YP) de Mexico involucra principalmente el polen fosil preservado en archivos sedimentarios, mientras que la geoquimica ha recibido menos atencion. En este estudio, se compararon las concentraciones de K, Ti, Fe, Ca y Sr, en 35 muestras superficiales de sedimento del Holoceno tardio, colectadas en un gradiente de precipitacion entre 600-1600 mm/a, a lo largo de la YP, con el objetivo de establecer un testigo de la paleo-precipitacion para la region. El origen calcareo tiene un efecto de dilucion en las concentraciones elementales, provocando que los sedimentos presenten baja cantidad de K, Ti y Fe (elementos asociados con clasticos) y mayor cantidad de Ca y Sr (elementos asociados con carbonato y evaporitas), en comparacion con la corteza continental superior. Los elementos individuales y las relaciones de K/Ca, Ti/Ca y Fe/Ca en muestras con cantidades minimas de clastico, no muestran una relacion con la precipitacion. Los valores promedio de la relacion elemental en sedimentos con mas clasticos, muestra tendencias positivas con la precipitacion. No obstante, el protocolo de muestreo y la presencia de un mayor numero de cuerpos de agua investigados en un simple aglomerado (p. ej. 1200-1400 mm/a) no permitio completar la evaluacion de la correlacion potencial entre precipitacion y la relacion elemental. Considerando que la concentracion de Ti en los sedimentos ricos en calizas de la PY es bajo y el Fe es mov","PeriodicalId":45458,"journal":{"name":"BOLETIN GEOLOGICO Y MINERO","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2018-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49497236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Palynodiversity patterns and paleoclimatic changes in the late Paleozoic in Brazil and Uruguay","authors":"Á. Beri, X. M. Blanco, Leticia Tejera, A. Piñeyro, Paulo A. Souza","doi":"10.21701/BOLGEOMIN.129.4.001","DOIUrl":"https://doi.org/10.21701/BOLGEOMIN.129.4.001","url":null,"abstract":"espanolSe analizo la diversidad de la palinoflora correspondiente a estratos del Paleozoico superior de las cuencas de Parana (Brasil y Uruguay), Parnaiba y Amazonas (Brasil), utilizando datos previamente publicados. Se elaboraron curvas de diversidad total y diversidad calculadas mediante el metodo range-through y se calcularon los indices de aparicion y desaparicion de los diferentes generos utilizando como herramienta el indice de Foote. Tambien se analizaron esos parametros en diferentes grupos de esporomorfos por separado. Se observo un aumento importante de la diversidad en el Asseliano y Sakmariano y una posterior disminucion gradual hasta el Lopingiano. Los valores de los indices de aparicion fueron mas importantes que los de desaparicion y se dieron en el Asseliano, mientras que las mayores desapariciones se observaron en el Capitaniano y en menor medida en el Sakmariano. Por otra parte, las esporas y los granos de polen presentan algunas diferencias en la tendencia general de diversidad. Sin embargo, se aprecian diferencias en los patrones de aparicion y desaparicion. A pesar de los posibles sesgos, fundamentalmente relacionados con el esfuerzo de colecta, existe cierta coherencia entre la diversidad, los indices de apariciones y desapariciones y las fases climaticas propuestas para esa edad en la region. El cambio hacia un clima mas templado ocurrido en el Permico inferior estaria asociado a un aumento en el numero de generos de palinomorfos mientras que el comienzo de una fase mas arida estaria relacionado a una disminucion en la diversidad. EnglishWe have analysed the diversity of the late Paleozoic palynoflora of the Parana (Brazil and Uruguay), Parnaiba and Amazon (Brazil) basins using already published data. In order to do this the total diversity and diversity with range-through approach curves were built up, as well as Foote’s appearance and disappearance rates at the generic level. These parameters were also obtained separately for each group of sporomorphs. An important increase in diversity in the Asselian and Sakmarian and a posterior decrease until the Lopingian were observed. The values of the appearance rates were higher than those of disappearance and they peaked in the Asselian, while the highest disappearances took place in the Capitanian and, to a lesser extent, in the Sakmarian. On the other hand, spores and pollen grains show some differences in the general diversity trend. However, there are differences in the patterns of appearance and disappearance. Despite possible biases, mainly related to the collecting effort, the diversity curves and appearance and disappearance rates obtained are congruent with the climatic phases proposed for this region in these periods. The increase in the number of palynomorph genera is associated to the early Permian climatic amelioration whilst a decrease in diversity is related to the beginning of an arid phase.","PeriodicalId":45458,"journal":{"name":"BOLETIN GEOLOGICO Y MINERO","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2018-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47544700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Advanced analysis methods applied to reconstructed and simulated paleoclimatic time series","authors":"C. Herrero, A. García-Olivares","doi":"10.21701/BOLGEOMIN.129.3.003","DOIUrl":"https://doi.org/10.21701/BOLGEOMIN.129.3.003","url":null,"abstract":"The results of a simulated CO2 (C) and a global ice volume (V) time series, derived from a simple relaxation model of the glacial-interglacial cycles (García-Olivares and Herrero, 2013), have been analyzed using linear and non-linear techniques to evaluate the ability of the model on simulating the dynamics embedded on the climate system. On a first approximation, we have compared simulated time series with the corresponding paleoclimatic reconstructions, obtaining correlations of 0.88 between proxy-record δO (Lisiecki and Raymo, 2005) and simulated V, and 0.79 between reconstructed atmospheric CO2 concentration (Petit et al., 1999; Indermuhle et al., 2000; Monnin et al., 2001; Siegenthaler et al., 2005; Luthi et al., 2008) and simulated C. Spectral analysis using Fourier transform and continuous wavelet transform are useful tools to quantify the performance of a model for reproducing the dynamics embedded in reconstructed time series. The analysis shows that the model reproduces closely the dynamics embedded in the ice volume time series, but the coherence between the simulated and reconstructed CO2 is only sporadic, indicating that both time series do not follow the same dynamical behaviour, although in the deglacial periods the two carbon series become dynamically close. The analysis reinforces the hypothesis that some specific mechanisms included in the model are able to closely reproduce the glacial-interglacial oscillations and thus suggests which specific mechanisms should be more seriously investigated in the climate system. These techniques may be applied to other climatic time series to quantify the performance of a model simulating the dynamics of the climate system.","PeriodicalId":45458,"journal":{"name":"BOLETIN GEOLOGICO Y MINERO","volume":"1 1","pages":""},"PeriodicalIF":0.2,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47541376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}