Abstract This study shows the usefulness of borehole geophysical logging of density in the identification of coal seams, in relation to other lithologies present in a coal deposit located in the south of Brazil. Four drillholes were studied. The geological descriptions of the core samples recovered from these holes were the main information used as a control parameter in comparison with the geophysical logs. A threshold of density (2.0 g/cm3) was established in the gamma-gamma log analysis for identifying the coal seams with economic value. Also due to the economic and operational aspects related to the coal industry, the coal seams must be at least 0.4 meters thick. Once the coal seams were identified by density logs, a verification of the accuracy in the determination of the thicknesses and densities of the coal seams was performed. The coal seam thicknesses and densities determined by borehole logging were close to the observed values in the borehole core samples. As a result of the comparison between the geological and density log data, an average value difference of 0.03 m and -0.01 g/cm3 was reached for thickness and density, respectively. Due to the results and valuable information obtained, it was also possible to indicate and determine which areas of the deposit should be mined in relation to the drillholes studied and threshold parameters established. In conclusion, the importance of this evaluation is emphasized, mainly with respect to the thickness of the coal seams, which aids in the development of effective mine planning. Brazil logs 2.0 20 2 0 (2. gcm3 gcm g cm3 cm gammagamma gamma industry 04 4 0. thick performed data 003 03 0.0 0.01 001 01 -0.0 g/cm respectively obtained conclusion emphasized planning 2. (2 00 -0. ( -0 -

Abstract The opening of a mining enterprise requires knowledge of the geomechanical characteristics of the mineral deposit, which will be worked according to the use of parameters of stability and/or resistance of the material, as well as the discontinuities present in the rock. In this study, the Rock Mass Rating methodology was used to propose a geomechanical model in a lead and zinc deposit hosted in the sedimentary rocks of Camaquã Basin, Brazil. A geological model was created using the analysis of 50 drill holes with their geological descriptions, grouped into five lithological units, from base to top: rhythmite, lower sandstone, conglomerate, upper sandstone, and ore. The samples were regularized in composites of three meters in length, and then categorized into the five classes of the RMR system. Classes were estimated for each lithological unit using indicator kriging to obtain a model with the probability of each estimated block belonging to each RMR class, and thus the predominant class probabilities of each block. While it was possible to observe a predominance of class II (good rock) in the conglomerate, lower sandstone and ore, in the upper sandstone and rhythmite class III predominates (fair rock), and a few blocks were classified in class IV (poor rock) and V (very poor rock). Although the geomechanical model demonstrates the quality of the rock mass in general, being indispensable to more detailed studies, it is believed that the model allows greater safety in the classification of the rock mass and later use for slope stability and pit design.

As usinas de beneficiamento de minério, para garantir elevados índices de recuperação no produto final, dependem de inúmeros fatores, entre os quais destaca-se a estabilidade no teor de alimentação. As pilhas de homogeneização têm se mostrado uma ferramenta eficaz no atendimento dessa necessidade, atenuando, significativamente, a variabilidade do minério proveniente de diferentes frentes de lavra. Esse estudo testa a eficiência da simulação geoestatística quando aplicada à previsão da variabilidade in situ dos teores do minério formador das pilhas de homogeneização. Isto porque os métodos tradicionalmente utilizados, para o planejamento desses sistemas, não são capazes de incorporar, adequadamente, a incerteza associada ao valor estimado. Surge, então, a simulação geoestatística como alternativa, método que possibilita a geração de múltiplos cenários equiprováveis dos teores de determinado depósito. O conjunto de realizações dará origem a um grupo de possíveis valores para os blocos formadores de cada pilha, possibilitando, assim, a quantificação da variabilidade in situ. Os teores simulados foram comparados com os amostrados pela empresa. A reconciliação entre previsto e realizado mostrou precisão e acuracidade dos modelos gerados, reproduzindo, adequadamente, os teores de referência.

Mineral processing in order to ensure high ore recovery at the final product depends on many factors, among them, the low variability in the head grades feeding the plant. For this, homogenization piles have been an effective tool for significantly diminishing variability. This study tests the efficiency of geostatistical simulations to predict in situ grade variability and how this variability is transposed to the ore, forming blending piles. Traditionally, the methods used in designing these systems are not capable of properly incorporating the uncertainty associated with the estimated value. Ordinary kriging, for example, results in best local estimates, but with a smooth global variance. Conversely, geostatistical simulations provide equiprobable scenarios for the grades of a given deposit. These scenarios honor the sample values, their histogram and spatial distribution. They also provide a set of possible values for each block which forms each homogenization pile. Finally, it is possible to predict the in situ grade variability, given the real grades. The results were compared against the real (reference) mined grades through reconciliation. Results demonstrated that the methodology is accurate and precise enough to be applied in blending piles design.