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Abstract The Sanandaj-Sirjan Zone (SSZ) is considered as an important region for gold exploration in the western sector of Iran. Its mountainous topography and unpaved routes make its study challenging for researchers and raise the costs for mining companies strating new exploration plans. Gold mineralization mainly occurs as irregular to lenticular sulfide-bearing quartz veins along shear zones in deformed mafic to intermediate metavolcanic and metasedimentary rocks. In this investigation, ASTER data are used for mapping hydrothermal alteration minerals and to better discriminate geological structural features associated with orogenic gold occurrences in the area. Image transformation techniques such as specialized band ratioing and Principal Component Analysis are used to delineate lithological units and alteration minerals. Supervised classification techniques, namely Spectral Angle Mapper (SAM) and Spectral Information Divergence (SID) are applied to detect subtle differences between indicator alteration minerals associated with ground-truth gold locations in the area. The directional filtering technique is applied to help in tracing along the strike the different linear structures. Results demonstrate that the integration of image transformation techniques and supervised classification of ASTER data with fieldwork and geochemical exploration studies has a great efficiency in targeting new prospects of gold mineralization in the SSZ. The approach used in this research provides a fast, cost-efficient means to start a comprehensive geological and geochemical exploration programs in the study area and elsewhere in similar regions. [ABSTRACT FROM AUTHOR]

Field and mineralogical studies are integrated with multispectral and radar satellite data to unravel the occurrence of sulfide dissemination in the Gabal Monqul area (Eastern Desert, Egypt). This study was motivated by the strong belief that the widespread hydrothermal alteration haloes and sulfide disseminations in this area were ambiguously deciphered as a porphyry-style mineralisation. NE-Elongate bodies of silicified and sulfidized rocks frequently occur at the contacts between andesite-dacite, granodiorite, and porphyritic biotite granite intrusions. Hydrothermal alteration zones are best identified and outlined by employing band ratios (BR) and independent component analysis (ICA) techniques for the distinction between ferric and ferrous iron minerals. If fused with the clay and OH-bearing minerals maps, ferric iron oxides may characterise epithermal and porphyry mineralisation in which ore formation occurs under oxidising conditions. Iron-hydroxide, copper hydro-carbonate (malachite), and hydrous copper phosphate (pseudomalachite) are supergene mineral phases. The resultant processed images show that alteration extends beyond unit boundaries and overlaps different crosscutting lithologies. This observation implies that hydrothermal alteration of the host rock represents a secondary overprint, yet gypsum (±anhydrite) and barite in association with iron oxides and pyrite disseminations pinpoint a porphyry-related alteration assemblage. The poor metal endowment in the potassic alteration zones goes against the supergene enrichment typical of the porphyry mineralisation system and is coupled with the lack of hydrothermal breccia bodies, implying a rather epithermal sulfidation genesis. However, a thorough assay program is required to outline the potential metal-rich lithological unit(s) using XRD and remote sensing investigations that point to zonal alteration anomalies. • Sulfide mineralisation at G Monqul detected using petrological & remote sensing data. • Mineralised zones form a widespread NE-SW quartz and iron oxide veins. • Maximum Likelihood Classifier of ASTER is the most accurate for lithological mapping. • Independent component analysis distinct between ferric and ferrous iron minerals. • Potential metal enrichment, XRD and remote sensing define alteration zonal anomalies. [ABSTRACT FROM AUTHOR]

Satellite imagery combined with airborne geophysical data and field observations were employed for new geologic mapping of the Edembo area in the Eastern Hoggar (Tuareg Shield, Sahara). Multi-spectral band fusion, filtering, and transformation techniques, i.e., band combination, band-rationing and principal component analysis of ETM+ and ASTER data are used for better spectral discrimination of the different rocks units. A thematic map assessed by field data and available geologic information is compiled by supervised classification of satellite data with high overall accuracy (>90%). The automated extraction technique efficiently aided the detection of the structural lineaments, i.e., faults, shear zones, and joints. Airborne magnetic and Gamma-ray spectrometry data showed the pervasiveness of the large structures beneath the Paleozoic sedimentary cover and aeolian sands. The aeroradiometric K-range is used for discrimination of the high-K granitoids of Djanet from the peralumineous granites of Edembo, and to verify the Silurian sediments with their high K-bearing minerals. The new geological map is considered to be a high resolution improvement on all pre-existing maps of this hardly accessible area in the Tuareg Shield. Integration of the airborne geophysical and space-borne imagery data can hence provide a rapid means of geologically mapping areas hitherto poorly known or difficult to access. [ABSTRACT FROM AUTHOR]

The Sikhuran ophiolite complex in Esfandagheh, Kerman province, is considered one of the important chromite mining areas in southern Iran. The complex is comprised of mainly tectonized harzburgite of residual upper mantle, depleted harzburgite, chromitite, dunite, and orthopyroxenite of the transition zone, as well as upper cumulates of ultramafic-mafic rocks. Sulfide disseminations, i.e., pentlandite, chalcopyrite, chalcocite, millerite, and heazlewoodite are hosted by dunite and chromitite in the upper part of the transition zone. The abundance of Base Metal Sulfides (BMS) as interstitials of olivine shows early stage sulfur saturation in Mg-rich magmas. Low Ni contents of ubiquitous olivine indicate that Ni in the primary silicate melt is preferentially concentrated in the sulfide liquid. The high activity of Ni in the melt is evidenced by the dominance of Ni-rich pentlandite and other Ni-bearing minerals from the Sikhuran ophiolite complex. Major and trace element compositions indicate that pentlandite is the main PGE-carrier with ƩPGE up to 44 ppm. Palladium, the most abundant PGE, is partitioned into pentlandite by diffusion of Monosulfide Solid Solution (MSS). The factors affecting this mechanism include the initial concentration of Pd, low compatibility of Pd compared to IPGEs, and decreasing solubility of Pd in MSS with decreasing temperature. Generally, although no detailed studies have been conducted on the occurrence of sulfide minerals in Iran; sulfide mineralization with coarse sulfide minerals in the Sikhuran can be a new perspective for mining companies and economic geologists. [Display omitted] • Sulfide disseminations occur in the upper part of the transition zone. • Pentlandite from the transitional zone dunite is the main PGE-carrier. • High Ni contents in both pentlandite and olivine indicate Ni-enriched parental melts. • Pd partitioning to pentlandite occurred from Monosulfide Solid Solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Textual and trace element compositions of pyrite reflect successive pyrite generations. • Variations of trace element composition show an effect of time and temperature. • The normal distribution analysis provides useful information for fluid evolution. • Mechanisms of incorporation of trace element are related to fluid evolution. Variations in trace element composition of pyrites in inactive chimneys from the SMAR 26°S hydrothermal field provide important insights into the genesis and evolution of volcanic-hosted hydrothermal mineralization. Petrographic observations of zoned chimney samples integrated with in-situ LA-ICP-MS analysis of morphologically different pyrites allowed the assessment of fluid evolution during the chimney growth. Pyrite varieties precipitated with increasing temperatures from the outermost chimney wall (zone A) through the intermediate zone (zone B) to the inner zone (zone C). At the late mature stage, pyrite precipitates as interstice pore fillings. The distribution of trace elements in pyrites across the chimney indicates a strong dependence on time, temperature, and associated sulfide minerals. Variations in the trace elements composition of the different pyrite varieties indicate that the hydrothermal system evolved from low-temperature low-chloride liquid-dominated fluids (enriched in Zn, Cd, Tl, Ag, Pb, Mn, Mo, and V) to higher temperature, vapor-dominated fluids (Cu, Au, Te, and Bi), and then to high-temperature fluids (Co and Se). In the waning stage of the hydrothermal system, circulating hot fluids in auxiliary conduits were depleted in most trace elements. The systematic variations in trace element compositions of hydrothermal fluids induced by changes in physicochemical conditions are properly governed by the law of normal distribution of trace elements. The LA-ICP-MS time-depth analysis indicate that Cu, Zn, Cd, Tl, Ag, Te, and Bi are related to micro-/nano-inclusions, whereas Co, Se, and Mo may occur as substitutions in pyrite lattice. The As, Pb, Au, and Sb show both modes of occurrences as substitutions and as inclusions. Adsorbed films on pyrites control the distribution of V and Mo. The incorporation processes of trace elements in pyrites change with fluid evolution during the chimney growth: trapping of micro-/nano-inclusions and surface adsorption is seen more frequently at the low-temperature stage, and lattice substitution mainly at the elevated temperature stages. [ABSTRACT FROM AUTHOR]

In-situ sulfur isotopic compositions of morphologically different pyrites from the SMAR (southern Mid-Atlantic Ridge) 26°S hydrothermal field, integrated with δ34S and δ65Cu values in associated chalcopyrite, reflect a recurring flux of magmatic-hydrothermal fluids and subsequent leaching by seawater. The δ34S values of sulfides (−1.27 to +5.25‰) indicate mixing of magmatic sulfur with seawater sulfate-derived sulfur. Compared to other Mid-Ocean Ridge (MOR) hydrothermal vent sites, a significant contribution of magmatic fluids is herein distinctive. Three concentric mineralogical zones around the conduit in an inactive black smoker sample include an inner chalcopyrite-dominated zone, an intermediate zone of idiomorphic and massive pyrite, and an outermost zone of porous and colloform pyrite with/without traces of chalcopyrite. The systematic increase in δ34S from the interior conduit (avg. −0.60‰, n = 8) through the intermediate zone (avg. +2.36‰, n = 14) to the exterior wall (avg. +3.02‰, n = 27), and contributions of seawater sulfate (0 to 10.7%, and to 18.6%, respectively) are most likely related to interaction between hydrothermal fluid and previously precipitated sulfides. A significant contribution of seawater sulfate-derived sulfur occurred likely via permeability or porosity upsurge across the chimney. Chalcopyrite with consistently positive δ65Cu values (+0.17 to +0.48‰), which are typical of mid-ocean ridge (MOR) hydrothermal vent fluids, is suggestive of reaction/mixing with hydrothermal fluids. Sulfur and Cu isotopic compositions of chalcopyrite further imitate the significant contributions of magmatic gases in the formation of metalliferous seafloor massive sulfides. • Petrography of the SMAR 26°S sulfides reveals various morphologies of pyrites. • S and Cu isotopes of sulfides indicate mixing between magmatic fluids and seawater. • Chalcopyrite δ34S and δ65Cu data reflect the important role of magmatic volatiles. • Isotopic compositions of sulfides disclose fluid evolution during chimney growth. [ABSTRACT FROM AUTHOR]

• Application of Landsat-8 data for hydrothermal alteration mapping in tropical region; • Gold mineralization typified by intrusion-related gold deposit and quartz-dominant vein systems; • Spatial consistency of hydrothermal alteration with known mining area and gold occurrences in a granitic background; • Newly discovered prospective areas are Yangamo-Ndatanga and Taparé-Tapondo prospects. Climatic conditions and vegetation constrain the use of optical satellite imagery as an exploration tool for hydrothermal ore mineralization in tropical and subtropical regions. In this investigation, Landsat-8 and ASTER satellite imagery were used to detect hydrothermal alteration zones associated with gold mineralization in the Ngoura-Colomines region, Eastern Cameroon. The study area contains several gold-bearing quartz veins associated with zones of pyritization, muscovite/sericite, iron oxides, and silicification. Principal Component Analysis (PCA), Independent Component Analysis (ICA), and specialized spectral band ratios were used to extract spectral information related to vegetation, iron oxide/hydroxide minerals, Al–OH, Fe-Mg–OH, carbonate group minerals, and silicification using Landsat-8 data at regional scale. Linear Spectral Unmixing (LSU) algorithm was implemented to ASTER VNIR + SWIR bands for detailed discrimination of hematite, jarosite, kaolinite, muscovite, chlorite and epidote at district scale. The Automated Spectral Hourglass (ASH) technique was employed to extract reference spectra directly from the ASTER bands for producing fraction images of end-members using the LSU. A comprehensive field survey was used to verify the remote sensing results. Petrographic study, X-ray diffraction analysis and reflectance spectroscopy indicated the presence of quartz, goethite and sericite, as well as the absorption features of Fe3+/Fe2+, Al–OH, OH/H 2 O and SiO 2 in the alteration zones. Several hydrothermal alteration zones of iron oxide/hydroxide, clay, carbonate minerals and silicification zones were identified, which are spatially associated with known mining areas and gold occurrences in the study area. High potential prospects were also delineated, including the Ngoura-Colomines prospects and the newly discovered Yangamo-Ndatanga and Taparé-Tapondo prospects in the southwestern and southeastern parts of the study area. Consequently, satellite-based mineral prospectivity maps at regional and district scales were generated for the study area by implementing the fuzzy logic model to the most informative thematic layers derived from image processing results. The satellite-based prospectivity maps are reliable for exploration of new gold prospective zones in the Ngoura-Colomines goldfield. [ABSTRACT FROM AUTHOR]

The exploration of carbonate-hosted Pb-Zn mineralization is challenging due to the complex structural-geological settings and costly using geophysical and geochemical techniques. Hydrothermal alteration minerals and structural features are typically associated with this type of mineralization. Application of multi-sensor remote sensing satellite imagery as a fast and inexpensive tool for mapping alteration zones and lithological units associated with carbonate-hosted Pb-Zn deposits is worthwhile. Multiple sources of spectral data derived from different remote sensing sensors can be utilized for detailed mapping a variety of hydrothermal alteration minerals in the visible near infrared (VNIR) and the shortwave infrared (SWIR) regions. In this research, Landsat-8, Sentinel-2, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and WorldView-3 (WV-3) satellite remote sensing sensors were used for prospecting Zn-Pb mineralization in the central part of the Kashmar–Kerman Tectonic Zone (KKTZ), the Central Iranian Terrane (CIT). The KKTZ has high potential for hosting Pb-Zn mineralization due to its specific geodynamic conditions (folded and thrust belt) and the occurrence of large carbonate platforms. For the processing of the satellite remote sensing datasets, band ratios and principal component analysis (PCA) techniques were adopted and implemented. Fuzzy logic modeling was applied to integrate the thematic layers produced by image processing techniques for generating mineral prospectivity maps of the study area. The spatial distribution of iron oxide/hydroxides, hydroxyl-bearing and carbonate minerals and dolomite were mapped using specialized band ratios and analyzing eigenvector loadings of the PC images. Subsequently, mineral prospectivity maps of the study area were generated by fusing the selected PC thematic layers using fuzzy logic modeling. The most favorable/prospective zones for hydrothermal ore mineralizations and carbonate-hosted Pb-Zn mineralization in the study region were particularly mapped and indicated. Confusion matrix, field reconnaissance and laboratory analysis were carried out to verify the occurrence of alteration zones and highly prospective locations of carbonate-hosted Pb-Zn mineralization in the study area. Results indicate that the spectral data derived from multi-sensor remote sensing satellite datasets can be broadly used for generating remote sensing-based prospectivity maps for exploration of carbonate-hosted Pb-Zn mineralization in many metallogenic provinces around the world. [ABSTRACT FROM AUTHOR]

Listvenites normally form during hydrothermal/metasomatic alteration of mafic and ultramafic rocks and represent a key indicator for the occurrence of ore mineralizations in orogenic systems. Hydrothermal/metasomatic alteration mineral assemblages are one of the significant indicators for ore mineralizations in the damage zones of major tectonic boundaries, which can be detected using multispectral satellite remote sensing data. In this research, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) multispectral remote sensing data were used to detect listvenite occurrences and alteration mineral assemblages in the poorly exposed damage zones of the boundaries between the Wilson, Bowers and Robertson Bay terranes in Northern Victoria Land (NVL), Antarctica. Spectral information for detecting alteration mineral assemblages and listvenites were extracted at pixel and sub-pixel levels using the Principal Component Analysis (PCA)/Independent Component Analysis (ICA) fusion technique, Linear Spectral Unmixing (LSU) and Constrained Energy Minimization (CEM) algorithms. Mineralogical assemblages containing Fe2+, Fe3+, Fe-OH, Al-OH, Mg-OH and CO3 spectral absorption features were detected in the damage zones of the study area by implementing PCA/ICA fusion to visible and near infrared (VNIR) and shortwave infrared (SWIR) bands of ASTER. Silicate lithological groups were mapped and discriminated using PCA/ICA fusion to thermal infrared (TIR) bands of ASTER. Fraction images of prospective alteration minerals, including goethite, hematite, jarosite, biotite, kaolinite, muscovite, antigorite, serpentine, talc, actinolite, chlorite, epidote, calcite, dolomite and siderite and possible zones encompassing listvenite occurrences were produced using LSU and CEM algorithms to ASTER VNIR+SWIR spectral bands. Several potential zones for listvenite occurrences were identified, typically in association with mafic metavolcanic rocks (Glasgow Volcanics) in the Bowers Mountains. Comparison of the remote sensing results with geological investigations in the study area demonstrate invaluable implications of the remote sensing approach for mapping poorly exposed lithological units, detecting possible zones of listvenite occurrences and discriminating subpixel abundance of alteration mineral assemblages in the damage zones of the Wilson-Bowers and Bowers-Robertson Bay terrane boundaries and in intra-Bowers and Wilson terranes fault zones with high fluid flow. The satellite remote sensing approach developed in this research is explicitly pertinent to detecting key alteration mineral indicators for prospecting hydrothermal/metasomatic ore minerals in remote and inaccessible zones situated in other orogenic systems around the world. [ABSTRACT FROM AUTHOR]

Geological mapping and mineral exploration programs in the High Arctic have been naturally hindered by its remoteness and hostile climate conditions. The Franklinian Basin in North Greenland has a unique potential for exploration of world-class zinc deposits. In this research, multi-sensor remote sensing satellite data (e.g., Landsat-8, Phased Array L-band Synthetic Aperture Radar (PALSAR) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)) were used for exploring zinc in the trough sequences and shelf-platform carbonate of the Franklinian Basin. A series of robust image processing algorithms was implemented for detecting spatial distribution of pixels/sub-pixels related to key alteration mineral assemblages and structural features that may represent potential undiscovered Zn–Pb deposits. Fusion of Directed Principal Component Analysis (DPCA) and Independent Component Analysis (ICA) was applied to some selected Landsat-8 mineral indices for mapping gossan, clay-rich zones and dolomitization. Major lineaments, intersections, curvilinear structures and sedimentary formations were traced by the application of Feature-oriented Principal Components Selection (FPCS) to cross-polarized backscatter PALSAR ratio images. Mixture Tuned Matched Filtering (MTMF) algorithm was applied to ASTER VNIR/SWIR bands for sub-pixel detection and classification of hematite, goethite, jarosite, alunite, gypsum, chalcedony, kaolinite, muscovite, chlorite, epidote, calcite and dolomite in the prospective targets. Using the remote sensing data and approaches, several high potential zones characterized by distinct alteration mineral assemblages and structural fabrics were identified that could represent undiscovered Zn–Pb sulfide deposits in the study area. This research establishes a straightforward/cost-effective multi-sensor satellite-based remote sensing approach for reconnaissance stages of mineral exploration in hardly accessible parts of the High Arctic environments. [ABSTRACT FROM AUTHOR]