Conference Proceedings

Conference Proceedings

Merrill, J. Martínez, P. Urrutia, N. Voisin, L. (2016), "Sulphides detection by hyperspectral analysis in the thermal infrared range". 3er Seminario Internacional de Geometalurgia (GEOMET), Lima, Perú, 2016.

Hyperspectral analysis has had an increasing acceptance and application in the mining industry for mineral identification and characterization due to its rapid data acquisition, relatively low cost and non-destructive nature. Recognition of mineral species with this technique is achieved by identifying their distinctive spectral features in specific wavelengths of the electromagnetic spectrum. Until now, hyperspectral analysis in mining industry has been focused on gangue minerals as oxides, silicates, sulphates, carbonates, among others.

Even though scientific literature has reported that sulphide minerals have characteristic spectral features in the far infrared range of the electromagnetic spectrum (FIR: 15-100 μm), the hyperspectral techniques have not been successfully applied in detecting those minerals, in fact, there is currently no industrial hyperspectral analysis equipment that allows identifying sulphides. The most known equipment of this type, as Corescan or HyLogging Systems, work within visible-near infrared to thermal infrared ranges (from 0.4 to 14.5 μm approximately).

In the present research, by doing mathematical analysis of the measured spectra, it was possible to detect indirectly the presence of non-disseminated sulphides in the thermal infrared range (TIR: 6.5-14.5 μm), since reflectance around 7.6 μm was found to be significantly higher in samples that contain these minerals (e.g. pyrite, chalcopyrite or bornite). Based on this particular behaviour, spectral filters were created, in order to separate sulphides from other mineral species that also raise reflectance values around 7.6 μm wavelength, such as iron oxides (e.g. specular hematite). Sulphides detection through hyperspectral analysis in TIR range will help to improve the interpretation of ore and gangue minerals associations, providing new tools to optimize and improve decision-making within mining processes.

Painepán, M. Voisin, L. McFarlane, A. Montenegro, V. García, G. (2016). "Development of a proxy to identify molybdenum mineralization based on hyperspectral characterization". 3er Seminario Internacional de Geometalurgia (GEOMET), Lima, Perú, 2016.

Molybdenum is commonly associated with copper in porphyry deposits, however, its presence is less spatially continuous, and therefore it is more difficult for the estimation in resource models. Recently, hyperspectral analysis has become relevant and the utilisation is not only for exploration but also for geometallurgical uses, especially for clarifying the behavior of gangue minerals in downstream processes and allowing identification of valuable minerals from the characterization by using proxies. In comparison to other characterization methods, hyperspectral technology has advantages such as faster scanning rate, greater objectivity relative to traditional logging, non-destructive and almost no samples preparation requirements.

The present work involves a case study of a granodioritic copper porphyry deposit with a remarkable molybdenite mineralization, located in north Chile (Esperanza Sur project, Antofagasta Minerals S.A.). Hyperspectral data from different zones of the deposit obtained with Hylogger3 technology, together with chemical and QEMSCAN mineralogical analyses, were used to generate a proxy which allows the spatial estimation of molybdenum probabilities associated with gangue minerals.

For the methodology, first, mineralogical information was evaluated in terms of continuity and correlation, with those chemical ones related to molybdenum, second, the data was categorized and discretized, defining thresholds for mineral grade to establish valuable mineral or waste; third, probabilities using The Bayes theorem were assigned considering rocks characteristics, processing the data with the accumulative sum of errors on each drill core to define areas of mineralization and finally, a cross validation of the model, as a new information to process, was used to compare the prediction. The generated proxy allows to identify and predict existence and tendency of molybdenum into the deposit, reducing uncertainty and increasing the added value of the mining business.

Saavedra, I. Voisin, L. Merrill, J. Montenegro, V. McFarlane, A. (2016). "Predictive rheological models for Chilean mineral slurries based on hyperspectral characterization, using HyLogger3 technology". 9th International Copper Conference, Kobe, Japón, 2016.

Slurries are widely used in mineral processing and their rheological properties such as viscosity and yield stress strongly determine the energy consumption for pumping, the water requirements for transport, the throughput rate of thickeners and the capacity constraints of tailings impoundments. To investigate the impact of the mineralogy on their rheological behavior, synthetic slurries were prepared by varying the content of bentonites and white mica in order to represent critical gangue minerals that affect the slurry rheology and which are associated with copper sulphides in Chilean ore deposits. Laboratory scale rheometries were performed using those slurries, and viscosity and yield stress were determined by applying a Bingham-plastic flow model, the most suitable according to the observed behavior. The rheological properties for slurries were plotted on ternary diagrams where gangue component amounts represent the axes. Both viscosity and yield stress showed synergistic behavior as a result of blending. After this, HyLogger3 hyperspectral characterization of dry slurry samples was conducted to study the feasibility of using this novel technology as a tool to quickly identify the above gangue minerals, which can cause deleterious effect during their transport as mixed slurry. Hyperspectral data was related to the information from rheometries such that predictive geometallurgical models are formulated by different modelling techniques. The modelling results confirmed a good accuracy in the quantification of minerals and prediction of rheological properties by using hyperspectral technology, thus leading the development of a reliable prediction tool for the viscosity and yield stress of mineral slurries.

Jeldres, G. Voisin, L. (2016). "Effect of montmorillonite on the viscosity of smelting copper slag and its relation with copper in trap and refractory brick consumption". 9th International Copper Conference, Kobe, Japón, 2016.

Clay minerals, which are usually presented into the gangue associated with copper sulphide ores, follow the concentrate that is generated during the froth flotation process, and their presences have a significant effect on some transport phenomena properties of the slag that is formed during the pyrometallurgical process for metallic copper production. Behavior of slag turns to be complex and unpredictable because, even under controlled operational conditions, it tends to collect additional oxides formed during the oxidation of minor elements contained into concentrates, and also those dissolved from refractory bricks during the operation.

In this study, synthetic fayalite slags were prepared and doped with different amounts of montmorillonite in a magnesia crucible and then, they were melted by using an electric furnace under controlled partial pressure of oxygen of 10-8 atmospheres for 4 hours. After reaching the equilibrium, rheometric tests were taken to determine the effect of that clay mineral on slag viscosity and liquidus area at temperatures of 1275°C and 1350°C. Finally, the crucible was quenched into cold water and samples were taken and characterized by using XRD and XRF prior calibration with ICP.

From the study, it was determined a clear dependency of the content in charge of montmorillonite on the molten slag viscosity, it was observed a sharply increase in that property mainly due to the distribution of alumina and silica between both, molten matrix and crystals present into the slag, under the experimental conditions. The results were compared with those obtained from industrial slags in order to clarify the problematic of copper in trap and the refractory brick consumption.

Voisin, L. Ihle, C. Montenegro, V. Jeldres, G. (2015). "Modelo geometalúrgico predictivo del comportamiento de escorias de fusión, en función de la presencia de arcillas contenidas en concentrados de Cobre". 6ta Convención Cubana de Ciencias de la Tierra, La Habana, Cuba, 2015.

La presencia de óxidos como la alúmina, cromita y cal entre otros, contenidos en concentrados de cobre, tiene un efecto importante en características como densidad y viscosidad de las escorias que se forman en el proceso pirometalurgico para la producción de cobre metálico. En particular, en la primera operación unitaria del proceso productivo, denominada fusión, se inyecta al reactor pirometalúrgico un agente oxidante gaseoso, generalmente aire enriquecido con oxígeno, y se adiciona sílice como fundente para lograr la fusión del concentrado sulfurado y consecuente separación física de, una fase sulfurada concentrada rica en cobre denominada mata y, otra fase oxidada rica en hierro denominada escoria. Esta última, resulta ser compleja de representar y predecir su comportamiento puesto que tiende a colectar todos aquellos óxidos inicialmente contenidos en los concentrados más aquellos que se forman durante la etapa a partir de la oxidación de impurezas. La composición de las escorias tiene un efecto directo sobre su densidad y viscosidad y éstas a su vez sobre el atrapamiento mecánico de cobre y consumo de ladrillos refractarios. Los óxidos primarios contenidos en los concentrados sulfurados de cobre suelen estar contenidos en arcillas que acompañan al mineral en su procesamiento y flotan junto a los sulfuros en la etapa de concentración.

En la presente investigación se caracterizaron, mediante híper-espectrometría, XRD y XRF e ICP, diversos tipos de arcillas puras así también como concentrados sulfurados de cobre y escorias producidas por plantas concentradoras y fundiciones ubicadas en Chile, respectivamente, y se correlacionaron entre sí considerando condiciones operacionales y variables termodinámicas específicas de la etapa de fusión como composición, temperatura y presión parcial de oxígeno empleando data termodinámica existente en la literatura, para finalmente construir modelos geometalúrgicos que permiten predecir propiedades de densidad y viscosidad de las escorias de fusión y sus efectos sobre las pérdidas de cobre por atrapamiento mecánico y sobre el consumo de ladrillos refractarios.

Montenegro, V. Urrutia, N. Voisin, L. McFarlane, A. (2015). "Achievements from application of the Hylogger 3 to the mining industry in Chile". 37th Symposium on the Application of Computers and Operations Research in the Mineral Industry (APCOM), Fairbanks, Alaska, 2015.

A HyLogger-3 has been brought to Chile by the CSIRO Chile Centre of Excellence in Mining and Mineral Processing in collaboration with the Advanced Mining Technology Centre (AMTC) of the University of Chile, supported by the Chilean government and industry partners. The use of the HyLogger-3 in Chile opens new alternatives for the mining industry, providing a real opportunity for the local companies to increase their productivities in the future, one of the key objectives of the mining industry today.

Chilean mining companies are facing a crucial challenge, where energy costs are at a very high point due to environmental issues and mineral grades are constantly decreasing as a result of reserve depletion. In order to make mining activity more profitable, more accurate resource estimation, mine planning and geometallurgy becomes necessary. Hyperspectral Logging technology is a nondestructive and fast analytical technique which dramatically increases both the knowledge and the efficiency of geologist’s interpretation of geology and mineralogy from drill core. The main objective of this work is to use hyperspectral analysis of core to predict geotechnical and metallurgical properties of ore systems, supporting exploration, mining and mineral processing strategies.

This paper presents the current progress of hyperspectral research following the establishment of an advanced ore characterization laboratory in Chile and preliminary results from Chilean ore for enhancing geological and geometallurgical understanding using hyperspectral data.

Voisin, L. Merrill, J. Montenegro, V. McFarlane, A. (2015). "Application of the HyLogger3 to the characterization of mineral and metallurgical residues". 37th Symposium on the Application of Computers and Operations Research in the Mineral Industry (APCOM), Fairbanks, Alaska, 2015.

During the conventional production of copper matte from copper sulphide ores, some residues, such as tailings and slags are generated in the flotation and smelting stages, respectively. Residue characterization is a fundamental tool for the diagnosis of the operation, and is also necessary for post-treatment in order to reclaim unrecovered valuable elements and to ensure the stability of the tailings to minimize detrimental environmental outcomes.

Since corresponding tails and slags are primarily mixtures of oxides and silicates, hyperspectral analysis could be useful to determine, at an early stage, properties of these residues in order to generate a predictive model of their behaviors. The HyLogger-3 technology allows scanning of solid and granulated samples under the full VNIR/SWIR/TIR (visible and near infrared/shortwave infrared/thermal infrared) wavelength range, offering the opportunity to determine silicates, carbonates, sulphates, iron oxides among other mineral groups. In combination with The Spectral Geologist software (TSG), for the analysis of the obtained data, this approach represents a comprehensive, efficient and relatively low cost characterization method which constitutes a vital tool for resolving current and future problems in the mining and metals production industry.

This paper investigates the feasibility of using the HyLogger for the characterization of not just drill core or chip samples, but also mineral and metallurgical residues, the promising results using HyLogger 3 open a new possibility in the use of the hyperspectral analysis for metallurgical materials.

Martínez, P. Voisin, L. Montenegro, V. McFarlane, A. Laukamp, C. Huntington, J. (2015). "Hyperspectral logging for mineral deposits and its applications to mining". XIV Congreso Geológico Chileno, Coquimbo, Chile, 2015.

Automated hyperspectral drill core logging is capable of collecting detailed mineralogical information at close spatial resolution, complementing conventional (visual) logging with objective, data-rich information. An example of this technology is  HyLogger-3™, a reflectance spectroscopic instrument equipped with VNIR1, SWIR and TIR detectors. The deployment of HyLogger-3™ in major South American mineral deposits, such as the Chilean porphyry copper systems, has been in development through the Centre of Excellence for Mining and Mineral Processing at the AMTC since 2014. This document presents various examples of hyperspectral studies, and describe two case studies in detail that use this technology to solve mining-metallurgical and geological problems, in order to illustrate the potential of this analytic instrument. These cases are not directly related to the copper industry, but represent the way in which exploration and geometallurgical knowledge might be enhanced in porphyry systems via routinely acquired spectroscopic data.