Metodología para la caracterización de arcillas y unidades geometalúrgicas, Mina San Antonio Óxidos, Región de Atacama
Metodología para la caracterización de arcillas y unidades geometalúrgicas, Mina San Antonio Óxidos, Región de Atacama
Authors
Aguilera Ocares, Vania
Authors
Date
2022
Datos de publicación:
Keywords
Geología estructural - Litología - Rocas igneas - Mineralogía - Industria minera - Minerales - Arcilla
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Abstract
La mina San Antonio Óxidos (SAO), corresponde a un yacimiento de tipo pórfido cuprífero, que presenta localmente características de un skarn de Cu. Pertenece al Distrito Minero Potrerillos y se sitúa a 62 km al sur de la ciudad de El Salvador. La explotación a rajo abierto de la mina SAO se inicia el año 2015, extrayéndose la mena oxidada de cobre de la parte superior del yacimiento. Los trabajos geológicos previos que se han realizado en mina San Antonio hacen referencia al alto contenido y la amplia distribución de arcillas presente en el yacimiento, asociándolas a problemas metalúrgicos, relacionados especialmente al consumo de ácido analítico, sin embargo, estos trabajos sólo se han realizado en términos genéricos. Por esta razón, este trabajo tiene como objetivo principal la caracterización de los diversos tipos de arcillas en el yacimiento, y establecer así su relación con el comportamiento metalúrgico, asociado al consumo de ácido analítico y propiedades mecánicas. Primero se desarrolló una metodología de caracterización mineralógica y además se consideraron las variables geológicas, tales como: litología, alteración y mineralización, que sentaron las bases para la creación de unidades Geometalúrgicas de consumo de ácido analítico (CAA) para la geología de producción de corto plazo.
Como resultado de este trabajo, se identificaron dos grupos de arcillas predominantes que corresponden a caolín y a las esmectitas, en estas últimas se identificaron porcentajes de cobre y se las conoce en minería como “arcillas con cobre” (ACU), presentan un alto consumo de ácido analítico (55 - ≥ 75 kg/ton) debido a sus propiedades físicoquímicas. Además, se establecieron parámetros para la identificación de las ACU en terreno, con la finalidad de mapearlas y obtener una aproximación de su comportamiento geometalúrgico, el que fue contrastado con los análisis de rigor: consumo de ácido analítico (CAA), cobre total (CuT), cobre soluble en frío (CuSF), difracción de rayos X (XRD) y LIBS-Raman, siendo las dos últimas, técnicas con las que se logró identificar el tipo de arcilla y la presencia de cobre en las ACU.
Se definieron 7 Unidades Geológicas – Metalúrgicas (UGMc), con sus respectivas fases de producción, litologías, alteraciones, asociaciones minerales (UGMx) y tipo de arcillas (UGA) asociadas, donde la UGMc 1 posee el rango de CAA mayor (> 75 kg/ton), e incluye dentro de su mineralogía dominante: ACU, carbonatos, óxidos negros y un predominio de arcillas tipo esmectitas, además de las alteraciones argílica y metamórfica retrógrada, siendo considerada la más problemática; al igual que la UGMc 2 con un CAA alto, entre 60 y > 75 kg/ton, posee mineralogía similar a la UGMc 1, pero con presencia de sulfuros secundarios; en un segundo clúster se pueden agrupar las UGMc 3, 4 y 5 de
consumo de ácido analítico medio (35-60 kg/ton) cuyas mineralogías dominantes son:, sulfatos, fosfatos, nitratos, ACU, carbonatos, escasos OXN y sulfuros secundarios, y arcillas del tipo caolín-esmectitas; las UGMc 6 y 7, tienen un rango de CAA menor (< 35 kg/ton), con predominio de sulfatos, fosfatos, y arcillas tipo caolín, siendo las menos problemáticas.
Se extrajeron 34 muestras de las actuales fases de producción del rajo (Fase 1B y 1C), para corroborar las tendencias estadísticas de la Base de Datos de pozos de tronadura de San Antonio Óxidos (BDSAO), estas corresponden en su mayoría a muestras de óxidos de alta ley en zona de producción, con los distintos tipos de litologías y alteraciones que se presentan en el yacimiento. La clasificación mineralógica y metalúrgica de las muestras extraídas coincide con las estadísticas obtenidas de la BDSAO y es aplicable para muestras de Óxidos de Alta Ley (OAL) (> 0.4% CuSF) e incluso Óxidos de Baja Ley (OBL) (> 0.2% CuSF), pero no es válida para muestras estériles. La metodología desarrollada permite clasificar de manera integrada las muestras, considerando el comportamiento metalúrgico,
respecto al consumo de ácido analítico en las variables de fase-litología-alteración, asociación mineral y tipo de arcillas. Clasificación que mostró una buena concordancia entre los resultados esperados y los obtenidos, por lo que las variables identificadas serán consideradas parámetros fundamentales en las próximas etapas de la creación de unidades Geológica-metalúrgicas de la División
The San Antonio Oxides (SAO) mine corresponds to a porphyry copper style ore deposit, which locally have characteristics of a skarn. It belongs to the Potrerillos Mining District, located 62 km south of the city of El Salvador. The open pit exploitation of the SAO mine began in 2015, by extracting the oxidized copper-rich upper part of the ore deposit. Previous geological studies performed in the San Antonio mine mentioned the high content and widespread distribution of clay minerals within the ore deposit, and its relationship to metallurgical issues, especially related to the high consumption of analytical acid. However, these works have only been performed on a generic way. For this reason, this work aims to characterize the various types of clays within the ore deposit, and to establish their relationship to the metallurgical behavior, related to the analytical acid consumption and the mechanical properties. First, a methodology to characterize the mineralogy was developed, while the geological variables, such as: lithology, alteration and mineralization were also considered to set the foundations for the creation of Geometallurgical units for analytical acid consumption (CAA) for the shortterm production geology. As a result of this work, two main groups of clays were identified, corresponding to kaolin and smectite, the latter was identified to contain copper at the percentage level and they are known in the mining industry as "clays with copper" (ACU), they show a high consumption of analytical acid (55 - ≥ 75 kg/ton) due to its physicochemical properties. In addition, parameters for the identification of the ACUs in the field were established, in order to be able to map them and get an approximation of their geometallurgical behavior, which it was later checked with the rigorous analyses: analytical acid consumption (CAA), total copper (CuT), soluble copper in cold (CuSF), X-ray diffraction (XRD) and LIBSRaman, the last two techniques allow us to identify the type of clay and the presence of copper in the ACU. Seven Geological - Metallurgical Units (UGMc) were defined, with their corresponding production phase, lithology, alteration, mineral association (UGMx) and group of clay (UGA), where UGMc 1 has the highest CAA range (> 75 kg /ton), and its main mineralogy includes: ACU, carbonates, black oxides and a predominance of smectitetype clays, with argillic and retrograde metamorphic alterations present, and it is considered the most problematic; Likewise the UGMc 2 has a high CAA, between 60 and > 75 kg/ton, it has a similar mineralogy to UGMc 1, but it also contains secondary sulfides; In a second cluster, UGMc 3, 4 and 5 have an average analytical acid consumption (35-60 kg/ton), its main mineralogy consists of: sulfates, phosphates, nitrates, ACU, carbonates, rare OXN and secondary sulfides, and a mix of kaolin-smectite type clays; UGMc 6 and 7 have a lower CAA range (< 35 kg/ton), with a predominance of sulfates, phosphates, and kaolin-type clays, and it is considered the least problematic. Thirty-four samples were extracted from the pit of current production phases (Phase 1B and 1C), in order to corroborate the statistical trends of the San Antonio Oxides Blast Pits Database (BDSAO), these correspond mostly to high grade oxide samples from the production area, on different types of lithology and alteration that occur within the ore deposit. The mineralogical and metallurgical classification of the collected samples coincides with the statistics obtained from the BDSAO and can be applied to the High Grade Oxides (OAL) (> 0.4% CuSF) samples and even to the of Low Grade Oxides (LBO) (> 0.2% CuSF) samples but not to the barren. The developed methodology allow us to classify the samples in an integrated manner, considering the metallurgical behavior, regarding the consumption of analytical acid obtained from the variables: phase, lithology, alteration, mineral association, and type of clay. The classification showed a good agreement between the expected results and those obtained, hence, the identified variables will be considered as the fundamental parameters for the next stages on the creation of Geological-metallurgical units for the Division
The San Antonio Oxides (SAO) mine corresponds to a porphyry copper style ore deposit, which locally have characteristics of a skarn. It belongs to the Potrerillos Mining District, located 62 km south of the city of El Salvador. The open pit exploitation of the SAO mine began in 2015, by extracting the oxidized copper-rich upper part of the ore deposit. Previous geological studies performed in the San Antonio mine mentioned the high content and widespread distribution of clay minerals within the ore deposit, and its relationship to metallurgical issues, especially related to the high consumption of analytical acid. However, these works have only been performed on a generic way. For this reason, this work aims to characterize the various types of clays within the ore deposit, and to establish their relationship to the metallurgical behavior, related to the analytical acid consumption and the mechanical properties. First, a methodology to characterize the mineralogy was developed, while the geological variables, such as: lithology, alteration and mineralization were also considered to set the foundations for the creation of Geometallurgical units for analytical acid consumption (CAA) for the shortterm production geology. As a result of this work, two main groups of clays were identified, corresponding to kaolin and smectite, the latter was identified to contain copper at the percentage level and they are known in the mining industry as "clays with copper" (ACU), they show a high consumption of analytical acid (55 - ≥ 75 kg/ton) due to its physicochemical properties. In addition, parameters for the identification of the ACUs in the field were established, in order to be able to map them and get an approximation of their geometallurgical behavior, which it was later checked with the rigorous analyses: analytical acid consumption (CAA), total copper (CuT), soluble copper in cold (CuSF), X-ray diffraction (XRD) and LIBSRaman, the last two techniques allow us to identify the type of clay and the presence of copper in the ACU. Seven Geological - Metallurgical Units (UGMc) were defined, with their corresponding production phase, lithology, alteration, mineral association (UGMx) and group of clay (UGA), where UGMc 1 has the highest CAA range (> 75 kg /ton), and its main mineralogy includes: ACU, carbonates, black oxides and a predominance of smectitetype clays, with argillic and retrograde metamorphic alterations present, and it is considered the most problematic; Likewise the UGMc 2 has a high CAA, between 60 and > 75 kg/ton, it has a similar mineralogy to UGMc 1, but it also contains secondary sulfides; In a second cluster, UGMc 3, 4 and 5 have an average analytical acid consumption (35-60 kg/ton), its main mineralogy consists of: sulfates, phosphates, nitrates, ACU, carbonates, rare OXN and secondary sulfides, and a mix of kaolin-smectite type clays; UGMc 6 and 7 have a lower CAA range (< 35 kg/ton), with a predominance of sulfates, phosphates, and kaolin-type clays, and it is considered the least problematic. Thirty-four samples were extracted from the pit of current production phases (Phase 1B and 1C), in order to corroborate the statistical trends of the San Antonio Oxides Blast Pits Database (BDSAO), these correspond mostly to high grade oxide samples from the production area, on different types of lithology and alteration that occur within the ore deposit. The mineralogical and metallurgical classification of the collected samples coincides with the statistics obtained from the BDSAO and can be applied to the High Grade Oxides (OAL) (> 0.4% CuSF) samples and even to the of Low Grade Oxides (LBO) (> 0.2% CuSF) samples but not to the barren. The developed methodology allow us to classify the samples in an integrated manner, considering the metallurgical behavior, regarding the consumption of analytical acid obtained from the variables: phase, lithology, alteration, mineral association, and type of clay. The classification showed a good agreement between the expected results and those obtained, hence, the identified variables will be considered as the fundamental parameters for the next stages on the creation of Geological-metallurgical units for the Division
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