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Um Balad area has a good potential for further gold exploration because of the existence of extensive and intense alteration zones. The use of Remote Sensing data supported by Airborne Gamma-Ray Spectrometry (AGRS) data analyses enabled the exploration of new gold occurrences in the alteration zones at the Um Balad area. False Color Composites (FCC...
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... The origin of gold mineralization in Egypt's Eastern Desert is a matter of controversy. The Eastern Desert has been considered as one of the best places for gold occurrences [1][2][3]. On the Red Sea coast, the Um Balad area lies approximately 110 km northwest of Hurghada. It is located between 27° 48 ' 00 '' and 27° 52 ' 42 '' N and 32° 42 ' 22 '' and 32° 52 ' 20 '' E (Fig. 1a). ...
The Um Balad area is a part of the Arabian Nubian Shield (ANS), which hosts various gold and base metal deposits. Gold can be prospected in the alterations and sheared zones in the widely exposed metagabbro-diorite rocks in the Um Balad area. In this regard, the integration of ASTER multispectral data processing, gamma-ray spectrometry data analysis, GIS modeling, and fieldwork gave us a good indication of which areas are most likely to contain gold-related alteration zones in the study region. Three remote sensing techniques were applied, including Spectral Angle Mapper (SAM), Spectral Information Divergence (SID), and Mixture Tuned Matched Filtering (MTMF). Key alteration mineral types are mostly related to the spatial distribution of mineral-bearing alteration zones. Careful interpretation of the gamma-ray spectrometry data is reliable for mapping alterations related to hydrothermal activity. The potassium distribution (%) of the study area was analyzed, where the radioelement ratio maps [eTh/K and eU/K] were obtained. The F-parameter and the Th-normalization techniques (Ud % and Kd %) were respectively applied for identifying potential mineralization zones. The GIS (weight overlay analysis) tool was used to combine the results of the three methodologies (remote sensing approaches, gamma-ray spectrometry data interpretation, and automatic lineament extraction) by combining ten layers (ASTER-SAM, ASTER-SID, ASTER-MTMF, lineament density, [K%], [eTh/K], [eU/K], [K*(eU/eTh)], [Kd], [Ud]). A final gold-related alteration zone map was generated. For validation, spectral signatures of the acquired rock samples as well as scanning electron microscopy (SEM) were used for the result verification of such a study. Finally, going forward, the adopted methodologies are considered the basis for gold-related alteration mapping in comparable environments.
... Although, FCC is a traditional remote sensing method, it is still widely used for various applications by specifying three bands in RGB. Selecting these bands depends mainly on the feature to be scrutinized 42,48,80,81 . For instance, in geological remote sensing, visible near-infrared (VNIR) bands are often included for discriminating iron-rich minerals due to the unique absorption features of these minerals at this spectral range. ...
Since their recent first record within the Egyptian Nubian Shield, auriferous and uraniferous marbles (Au = 0.98–2.76 g/t; U = 133–640 g/t) have rarely been addressed, despite not only their probable economic importance but also the fact that it is a new genetic style of gold and uranium mineralization in the Nubian Shield rocks. This is mainly attributed to the inadequate localization of these marbles within harsh terrains, as well as the cost and time spent with conventional fieldwork for their identification compared to the main lithological components of the Nubian Shield. On the contrary, remote sensing and machine learning techniques save time and effort while introducing reliable feature identification with reasonable accuracy. Consequently, the current research is an attempt to apply the well-known machine learning algorithm (Support vector Machine—SVM) over Sentinel 2 remote sensing data (with a spatial resolution of up to 10 m) to delineate the distribution of auriferous-uraniferous marbles in the Barramiya-Daghbagh district (Eastern Desert of Egypt), as a case study from the Nubian Shield. Towards better results, marbles were accurately distinguished utilizing ALOS PRISM (2.5 m) pan-sharpened Sentinel 2 data and well-known exposures during fieldwork. With an overall accuracy of more than 90%, a thematic map for auriferous-uraniferous marbles and the major rock units in the Barramiya-Daghbagh district was produced. Marbles are spatially related to ophiolitic serpentinite rocks, as consistent with their genesis within the Neoproterozoic oceanic lithosphere. Field and petrographic investigations have confirmed the newly detected Au and U-bearing zones (impure calcitic to impure dolomitic marbles in Wadi Al Barramiya and Wadi Daghbagh areas and impure calcitic marble in Gebel El-Rukham area). Additionally, X-ray diffraction (XRD), back-scattered electron images (BSEIs), and Energy Dispersive X-ray spectroscopy (EDX) results were integrated to verify our remote sensing results and petrographic investigations. Different times of mineralization are indicated, ranging from syn-metamorphism (gold in Wadi Al Barramiya and Gebel El-Rukham) to post-metamorphism (gold in Wadi Daghbagh and uranium in all locations). Based on the application of geological, mineralogical, machine learning and remote sensing results for the construction of a preliminary exploration model of the auriferous-uraniferous marble in the Egyptian Nubian Shield, we recommend a detailed exploration of Au and U-bearing zones in Barramiya-Dghbagh district and applying the adopted approach to other districts of similar geological environments.
... It is also useful and accurate in the identification and detection of potassic hydrothermal alteration zones. Studies have shown that eTh/K ratio be used to identify potassic alteration zones as mineralization prospects (Hegab 2021;Ebele et al. 2021;Mahmoud Abd El-Rahman et al. 2022). Within the study location, the applicability of geophysical techniques such as aeromagnetic and aeroradiometric methods to assist in the full realization of the gold mineralization potential is rare in the literature. ...
The mapping of lithology, structures, and hydrothermal alteration zones in Kaiama, northcentral Nigeria, was carried out to locate possible gold mineralization zones. Both aeromagnetic and aeroradiometric datasets were used in the investigation. Enhancement techniques such as first vertical derivative, analytic signal, Euler deconvolution, 2D power spectrum, and center for exploration targeting (grid and porphyry) as well as ratio and ternary maps were employed to aid in the interpretation process. The study reveals NE-SW, NW–SE, E-W, and N-S structural orientations dominate the area. The most important was the NE-SW, which was thought to be the best direction for mineral resources within the region. Also, depth estimation of shallow and deep-seated structures calculated using Euler deconvolution technique ranged from 250 to 1546 m, while power spectrum gave a range of 468–1853 m. Aeroradiometric analysis based on the concentrations of equivalent thorium (eTh), equivalent uranium (eU), and percentage potassium (%K), as well as radiometric ternary map, revealed the presence of nine (8) lithological units and hydrothermal alterations. Finally, a composite map was created that included geology, structures, and hydrothermally altered zones. From the map, tight concordance between known gold mineralization locations and the interpreted structural and hydrothermal complexities sheds a light on similar mapped features that may be new promising sites for gold mineralization. However, the precise detection and evaluation of possible ore-bearing zones in the area require more geological and geophysical investigation.
... SID is a spectral classification approach that uses divergence measurements to compare pixel spectra to reference spectra (Hegab, 2021). When the divergence is decreased, the pixel spectra are closer to being identical to the reference spectra. ...
The Um Balad area is a part of the Arabian Nubian Shield (ANS), which hosts various gold and base metal deposits. Gold can be prospected in the alterations and sheared zones in the widely exposed metagabbro-diorite rocks in the Um Balad area. In this regard, the image processing and analysis of the ASTER data is a rapid and efficient technique for such studies, where the structural pattern and associated lineaments are probable indicators of hydrothermal flow and activities developing in mineral-bearing alteration zones as targets for gold exploration. The Spectral Angle Mapper (SAM), Spectral Information Divergence (SID), and Mixture Tuned Matched Filtering (MTMF) techniques have identified the alteration zones and the characterized altered minerals of each alteration. The automatic lineament extraction method was used by ASTER's visible and near-infrared bands to produce a lineament density map. Using gamma-ray spectrometry data, the potassium percent (K %) and hydrothermal alteration parameters (F-parameter and Th-normalization) were calculated. As well as ratio maps (eTh/K and eU/K) were used to determine the potassic and phyllic hydrothermal alteration. The model of exploration for gold-related alterations was developed in the Um Balad area, using multiple layers derived from remote sensing and gamma-ray spectrometry data through a GIS (Weighted Sum Overlay) approach. The probability of gold-related alterations was graded as low, medium, good, and very good. A final map has been generated showing the gold-potential alteration zones in four localities (Area-1, Area-2, Area-3, and Area-4). In these altered zones, valuable minerals such as sulphides and gold may be precipitated, making them ideal gold exploration sites. The field observations and spectral signature analyses of the collected samples from the various identified alterations supported the results of the remote sensing and aero-spectrometry data analysis. Therefore, these techniques have been suggested for similar investigations in other areas.
... SID is a spectral classification approach that uses divergence measurements to compare pixel spectra to reference spectra (Hegab, 2021). When the divergence is decreased, the pixel spectra are closer to being identical to the reference spectra. ...
The transition zone between the North and the Central Eastern Desert of Egypt has been investigated using airborne magnetic and radiometric data to better characterize the subsurface structures, the tectonic framework, and mineral occurrences in the area. The magnetic data were subjected to several filtering and depth estimation techniques including edge detectors, Euler deconvolution, 2D forward modeling and 3D inversion. Statistical trend analysis of the lineaments obtained from geological and filtered magnetic maps shows that the major tectonic trends are NNE–SSW, NE–SW, and NW–SE, in addition to less predominant ENE–WSW and N–S trends. Two parallel shear zones trending NE–SW were detected. The causative magnetic structures were imaged at depths varying from the surface down to 2200 m. A number of strong uranium anomalies associated with Younger Granites and Dakhla, Duwi, and Quseir Formations were identified which are worth being considered for further ground investigations.
