Browsing by Author "Esamaldeen Ali, Mohamed Y. Abdegalil"

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Assessment of Image Ratio Technique for Gold Exploration in Arid Region Using Landsat ETM+7: Limitations and Possible Source of Misinterpretations
(Arab Remote Sensing And Geographic Information System Organization, 2016) Esamaldeen Ali, Mohamed Y. Abdegalil; Abu Elhassan Musa
In modern exploration program, the use of multispectral satellite images is one of the standard procedures during the early stages of gold exploration, due to its high efficiency and low cost. The main goal of the present study is to assess the efficiency of image ratio technique for gold mineralization in arid region. The area around the third cataract, northern state, Sudan has been selected for the current purpose. Landsat ETM+7 images have been used in the current study. The patterns recognized in the digitally processed satellite images showed a clear discrimination of granitic rocks, Sandstone from mafic metavolcanics, as well as delineate the structural features in the region. The spectral properties of band ratios have successfully been used to delineate alteration zones. Common false color composite ratio images have been applied by combining band ratio images in RGB. From these entire analyses through visual interpretation and ground truthing the results show that more than 60% of the image mask with iron alteration due to the dominantly ferruginous Sandstone formation in the study area and addition to clay-rich wadies deposits. From field observation very narrow hydrothermally alteration zone has been detected along highly sheared metavolcanics and their margin with syn-orogenic granites in the central part of the study area. This study clearly concluded that nevertheless, the significance of image ratio technique for gold exploration in early stage of exploration program, care should be taken during image interpretation in such geological condition.
Litho-Tectonic Evolution around Third Cataract, Sudan: An integrated Remote Sensing, Lithological, Structural and Geochemical Approaches
(Faculty of Petroleum and Minerals - Alneelain University, 2017) Esamaldeen Ali, Mohamed Y. Abdegalil; Abu Elhassan Musa, Nuha E. Mohamed
This Study is focused on the geology of the area around the Third Cataract, Sudan. In terms of combined remote sensing, petrological, structural and geochemical criteria this article presents detailed lithological and tectonic evolution of this region. For preliminary visual interpretation of the different lithological units and structural elements a digital image processing has been applied using Landsat 8 OLI images that are verified by precise ground truthing. Petrography, geological and structural field relationships have led to preliminary classification of rock units into: Undifferentiated orthogneisses and migmatites; Low to medium-grade metavolcano-sediments; Syn-orogenic intrusions; Late to post-orogenic intrusions; Cretaceous sandstone formation; Cainozoic volcanics and Quaternary to Recent sediments. Geological map has been created at scale of 1:75,000. In this study, three deformation episodes are identified (D1, D2 and D3), where D1 is associated with the formation of tight to isoclinal recumbent fold (F1) with north-dipping fold plane and sub horizontal trending axes verging to the east. Deformation took place in green schist-facies rocks that is thought to be related to the arc-accretion event. D2 gave rise to open upright fold (F2) which folded the axial surfaces of (F1) with fold axes plunging gently to the NNW. NNW–SSE sinistral strike slip movement is a main characteristic of D3 deformation. The geochemical results show a clear calc-alkaline trend of the metavolcanics units that were derived from volcanic arc magmas. Whereas the granitic rocks classify as calc-alkaline metaluminous to slightly peraluminous, and is considered as I-type granites. Rb versus (Y+Nb) discrimination diagram indicates volcanic arc granites.