Lithological and hydrothermal alteration mapping of epithermal, porphyry and tourmaline breccia districts in the Argentine Andes using ASTER imagery

The area of interest is located on the eastern flank of the Andean Cordillera, San Juan province, Argentina. The 3600 km2 area is characterized by Siluro-Devonian to Neogene sedimentary and igneous rocks and unconsolidated Quaternary sediments. Epithermal, porphyry-related, and magmatic-hydrothermal breccia-hosted ore deposits, common in this part of the Frontal Cordillera, are associated with various types of hydrothermal alteration assemblages. Kaolinite – alunite-rich argillic, quartz – illite-rich phyllic, epidote – chlorite – calcite-rich propylitic and silicic are the most common hydrothermal alteration assemblages in the study area. VNIR, SWIR and TIR ASTER data were used to characterize geological features on a portion of the Frontal Cordillera. Red-green-blue band combinations, band ratios, logical operations, mineral indices and principal component analysis were applied to successfully identify rock types and hydrothermal alteration zones in the study area. These techniques were used to enhance geological features to contrast different lithologies and zones with high concentrations of argillic, phyllic, propylitic alteration mineral assemblages and silicic altered rocks. Alteration minerals detected with portable short-wave infrared spectrometry in hand specimens confirmed the capability of ASTER to identify hydrothermal alteration assemblages. The results from field control areas confirmed the presence of those minerals in the areas classified by ASTER processing techniques and allowed mapping the same mineralogy where pixels had similar information. The current study proved ASTER processing techniques to be valuable mapping tools for geological reconnaissance of a large area of the Argentinean Frontal Cordillera, providing preliminary lithologic and hydrothermal alteration maps that are accurate as well as cost and time effective

Physicochemical conditions of formation for bismuth mineralization hosted in a magmatic-hydrothermal breccia complex: an example from the Argentine Andes

The San Francisco de los Andes breccia-hosted deposit (Frontal Cordillera, Argentina) is characterized by complex Bi-Cu-Pb-Zn-Mo-As-Fe-Ag-Au mineralization. After magmatichydrothermal brecciation, tourmaline and quartz partially cemented open spaces, followed by quiescent periods where Bi-Cu-Pb-Zn ore formed. Bismuth ore precipitation is characterized by Bi-sulfides, sulfosalts, and tellurosulfide inclusions, which temporally co-exist with Ag-telluride inclusions and chalcopyrite. Three distinct Bi mineralizing stages have been defined based on the following mineral assemblages: (1) Bismuthinite (tetradymite–hessite inclusions); (2) Bismuthinite (tetradymite–hessite inclusions) + cosalite (tetradymite inclusions) + chalcopyrite; and (3) Cosalite (tetradymite inclusions) + chalcopyrite. Overall, Ag-poor bismuthinite hosts both Bi-tellurosulfide and Ag-telluride inclusions, whereas Ag-rich cosalite only hosts tetradymite inclusions.In this study, we discuss the effects of temperature, pressure, vapor saturation, salinity, acidity/alkalinity, and redox conditions on Bi-rich mineralizing fluids. Evolving hydrothermal fluid compositions are derived from detailed paragenetic, analytical, and previous fluid inclusion studies. Based on trace minerals that co-precipitated during Bi ore formation, mineral chemistry, and quartz geothermobarometry, a thermodynamic model for bismuth species was constructed. Sulfur and tellurium fugacities during Bi-ore precipitation were constrained for the three mineralizing stages at a constant pressure of 1 kbar under minimum and maximum temperatures of 230 and 400 °C, respectively. We infer that Te was transported preferentially in a volatile-rich phase. Given that Te solubility is expected to be low in chloride-rich hydrothermal fluids, telluride and tellurosulfide inclusions are interpreted to have condensed from magmatically-derived volatile tellurium (e.g., Te2(g) or H2Te(g)) into deep-seated, dense, metal-rich brines. Tellurium minerals in the hydrothermal breccia cement provide a direct genetic link with the underlying magmatic system. Though the vertical extent of the breccia complex is unknown, the abundance of Te-bearing minerals could potentially increase with depth and not only occur as small telluride inclusions in Bi-minerals. A vertical zoning of Te-minerals could prove to be important for exploration of similar magmatic-hydrothermal brecciapipes and/or dikes

Comparison of different algorithms to map hydrothermal alteration zones using ASTER remote sensing data for polymetallic Vein-Type ore exploration: Toroud-Chahshirin Magmatic Belt (TCMB), north Iran

© 2019 by the authors. Polymetallic vein-type ores are important sources of precious metal and a principal type of orebody for various base-metals. In this research, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) remote sensing data were used for mapping hydrothermal alteration zones associated with epithermal polymetallic vein-type mineralization in the Toroud-Chahshirin Magmatic Belt (TCMB), North of Iran. The TCMB is the largest known goldfield and base metals province in the central-north of Iran. Propylitic, phyllic, argillic, and advanced argillic alteration and silicification zones are typically associated with Au-Cu, Ag, and/or Pb-Zn mineralization in the TCMB. Specialized image processing techniques, namely Selective Principal Component Analysis (SPCA), Band Ratio Matrix Transformation (BRMT), Spectral Angle Mapper (SAM) and Mixture Tuned Matched Filtering (MTMF) were implemented and compared to map hydrothermal alteration minerals at the pixel and sub-pixel levels. Subtle differences between altered and non-altered rocks and hydrothermal alteration mineral assemblages were detected and mapped in the study area. The SPCA and BRMT spectral transformation algorithms discriminated the propylitic, phyllic, argillic and advanced argillic alteration and silicification zones as well as lithological units. The SAM and MTMF spectral mapping algorithms detected spectrally dominated mineral groups such as muscovite/montmorillonite/illite, hematite/jarosite, and chlorite/epidote/calcite mineral assemblages, systematically. Comprehensive fieldwork and laboratory analysis, including X-ray diffraction (XRD), petrographic study, and spectroscopy were conducted in the study area for verifying the remote sensing outputs. Results indicate several high potential zones of epithermal polymetallic vein-type mineralization in the northeastern and southwestern parts of the study area, which can be considered for future systematic exploration programs. The approach used in this research has great implications for the exploration of epithermal polymetallic vein-type mineralization in other base metals provinces in Iran and semi-arid regions around the world

Multispectral and Hyperspectral Remote Sensing Data for Mineral Exploration and Environmental Monitoring of Mined Areas

In recent decades, remote sensing technology has been incorporated in numerous mineral exploration projects in metallogenic provinces around the world. Multispectral and hyperspectral sensors play a significant role in affording unique data for mineral exploration and environmental hazard monitoring. This book covers the advances of remote sensing data processing algorithms in mineral exploration, and the technology can be used in monitoring and decision-making in relation to environmental mining hazard. This book presents state-of-the-art approaches on recent remote sensing and GIS-based mineral prospectivity modeling, offering excellent information to professional earth scientists, researchers, mineral exploration communities and mining companies

Lithological Mapping and Identification of Argillic and Propylitic Alteration Zones at Anjerd Volcanic Terrain

Anjerd area is part of Arasbaran volcanic-magmatic terrain in northwestern Iran. The area is covered by multiple intrusive bodies of diverse compositions, volcanic, volcaniclastic, sedimentary and young alluvial deposits. The usefulness of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data for the lithologic mapping of the area and identification of alteration zones is investigated in this study. To carry out the study, one ASTER frame was atmospherically calibrated by Internal Average Relative Reflectance (IARR). The False Color Composite (FCC) and Principal Component Analysis (PCA) images were used for discriminating lithologic units along with Spectral Angle Mapper (SAM) and Matched Filtering (MF). The pure endmember image spectra were extracted from Pixel Purity (PPI) algorithm. The results showed that PCA and FCC can be used to discriminate sedimentary rocks from magmatic and volcanic rocks. Because feldspars and quartz are relatively featureless in shortwave infrared (SWIR) spectral region the methods were not capable to distinguish between various magmatic rocks except for basalts with darker color and higher pyroxene content. The MF gave better results than SAM algorithm and therefore MF is recommended over SAM for studying similar terrains. The argillic and propylitic alteration zones were detected by band ratios. The results showed that MF algorithm in combination with band ratios can be used to distinguish magmatic rocks from sedimentary rocks and delineate the alteration zone

Lithological Mapping and Identification of Argillic and Propylitic Alteration Zones at Anjerd Volcanic Terrain

Anjerd area is part of Arasbaran volcanic-magmatic terrain in northwestern Iran. The area is covered by multiple intrusive bodies of diverse compositions, volcanic, volcaniclastic, sedimentary and young alluvial deposits. The usefulness of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data for the lithologic mapping of the area and identification of alteration zones is investigated in this study. To carry out the study, one ASTER frame was atmospherically calibrated by Internal Average Relative Reflectance (IARR). The False Color Composite (FCC) and Principal Component Analysis (PCA) images were used for discriminating lithologic units along with Spectral Angle Mapper (SAM) and Matched Filtering (MF). The pure endmember image spectra were extracted from Pixel Purity (PPI) algorithm. The results showed that PCA and FCC can be used to discriminate sedimentary rocks from magmatic and volcanic rocks. Because feldspars and quartz are relatively featureless in shortwave infrared (SWIR) spectral region the methods were not capable to distinguish between various magmatic rocks except for basalts with darker color and higher pyroxene content. The MF gave better results than SAM algorithm and therefore MF is recommended over SAM for studying similar terrains. The argillic and propylitic alteration zones were detected by band ratios. The results showed that MF algorithm in combination with band ratios can be used to distinguish magmatic rocks from sedimentary rocks and delineate the alteration zone

Experimental and Thermodynamical Modeling of Ore-Forming Processes in Magmatic and Hydrothermal Systems

This special issue book includes 10 original research papers that discuss and solve some problems of ore-forming processes in magmatic and hydrothermal systems. Some of these papers in the issue deal with experimental and thermodynamical modeling, while the others are devoted to analytical geochemistry, geochronology and genesis of some ore occurrences. I hope that these papers will be useful for scientists who work on the fundamental problems of ore-forming processes and the genesis of ore deposits, and will provide new ideas for future research

Teledetección multiespectral como apoyo a la cartografía del macizo ultramáfico de Ojén, Málaga

47 páginas.Trabajo Fin de Máster Oficial en Geología y Gestión Ambiental de los Recursos Minerales. Tutores: Dr. D. Fernando Gervilla Linares ; Dr. D. Felipe González Barrionuevo. El área del macizo ultramáfico de Ojén se encuentra en la provincia de Málaga. Al igual que el de Ronda, el de Carratraca y el del Rif (Beni Bousera), se encuentran contenidos en las Zonas Internas de la Cordillera Bético-Rifeña. Las rocas que abundan en este macizo en general son las lerzolitas estando en algunos casos alteradas a serpentinita. Esta zona presenta una actividad minera que en los últimos años se ha enfocado en la explotación de talco. Las alteraciones presentes en el mismo han sido poco estudiadas, además de que no hay una cartografía regional de estas que permita predecir otras zonas minerales. Para esto se utilizaron imágenes satelitales procedentes de los satélites Sentinel-2 y ASTER, las que permitirían poner a prueba la resolución del método y la capacidad de cada una. Los procesamientos utilizados se basaron sobre todo en las relaciones de bandas y el Análisis de Componentes Principales. Llegándose a cartografiar los límites del macizo, las zonas de alteración regional, las zonas más afectadas por la meteorización y los límites entre las unidades presentes. Además, se logró aislar la respuesta de depósitos de talco en las imágenes satelitales, lo que permite localizarar zonas que pudieran ser perspectivas para depósitos de esta materia.The ultramafic massif of Ojén is located in the province of Malaga. Like the massifs of Ronda, Carratraca and Rif (Beni Bousera), this is found in the Inner Zones of the Betic-Rifeña Mountain Range. The most common rocks in this massif are lherzolites, which, in some cases, are altered to serpentinite. This area presents a mining activity focused on the exploitation of talc in recent years. The alteration present in the massif has been scarcely studied, and no regional cartographic map useful for predicting additional mineral zones have been composed so far. For this study, the cartography was done using two sets of images from the satellites Sentinel-2 and ASTER. The processes used were mainly based on Rationing and Principal Component Analysis. The images processed with these technics are able to show the cartographic limits of the massif, the regional alteration, the areas most affected by weathering and the boundaries between internal units within the massif. Additionally, it was possible to isolate the response of talc mineralizations present in the area, permitting to map potential targets of this mineral