Exploration and Petrogenesis of Corundum-Bearing Pegmatites: A Case Study in Migif-Hafafit Area, Egypt

Abstract

A net of pegmatite veins crosscut gneiss and dismembered ophiolitic ultramafic rocks are abundant in the Migif-Hafafit culmination area, South Eastern Desert, Egypt. Some of these pegmatites are corundum-bearing. Corundum-bearing pegmatites are studied in eight localities around the Migif-Hafafit complex. The present study aims to integrate field investigation, whole rock and corundum chemistry, remote sensing studies, and the conventional methods to detect the corundum-bearing pegmatites, which led to finding out the genesis of the corundum mineralization. In addition, the tectonic regime has been detected using bulk rock geochemistry. False-color composite (FCCs), band ratio (BR), principal component analysis (PCA), minimum noise fraction (MNF), decorrelation stretch (DS), and the constrained energy minimization (CEM) image processing algorithms were proposed and applied on Landsat-8 OLI, and Sentinel-2A data to discriminate the exposed lithological units and to detect the corundum-bearing pegmatites in the study area. These detected pegmatites are structurally controlled following the NW-SE direction. The ultramafic rocks are the host of six areas and the gneisses are the host rocks of the two others. Gneisses and pegmatites are characterized by a steep slope of LREEs relative to HREEs with week Eu negative anomaly. The studied pegmatites have both plumasite and marundite. On the other hand, the studied corundum has Al2O3 content up to 99.72 wt% in pegmatite-gneiss and up to 100 wt.% in pegmatite-ultramafics. Corundum is ascribed to metamorphic/metasomatic type according to its chromosphere. Desilication in pegmatites led to the excess of alumina content in the residual melt producing corundum mineralization.

Radiological Hazards and Natural Radionuclide Distribution in Granitic Rocks of Homrit Waggat Area, Central Eastern Desert, Egypt

“…Granitic rocks represent the most abundant plutonic rocks in the continental crust [1]. Their distribution in Arabian-Nubian Shield (ANS) is heterogeneous, since they are abundant in the northern ANS [2][3][4][5][6]. Granitic rocks cover about sixty percent of the Egyptian crystalline rocks in the Eastern Desert, which decreases to thirty percent in the south (Kenya and Ethiopia) of ANS [7,8].…”

Distribution of Radionuclides and Radiological Health Assessment in Seih-Sidri Area, Southwestern Sinai

“…Crystalline rocks of Egypt, which are dominantly distributed in the Eastern Desert and South Sinai as well as the Uwainate area, constitute the northern sector of the Arabian Nubian Shield (ANS) [ 18 , 19 , 20 ]. These rocks include infrastructure gneisses, ophiolite and arc assemblages, and variable compositions of granitic intrusion [ 21 , 22 , 23 , 24 ]. ANS represents the main crustal juvenile that developed during the late Proterozoic Era by closing the Mozambique Ocean [ 19 , 21 ], exposed from Egypt to Ethiopia on the Nubian side and from Saudi Arabia to Yemen on Arabian Side [ 25 ].…”

Assessing geochemical and natural radioactivity impacts of Hamadat phosphatic mine through radiological indices

“…In Egypt, there is a wide occurrence of igneous, metamorphic, and sedimentary rocks which are concentric essentially in Sinai, the Eastern, and Western Deserts [ 7 , 9 , 10 ]. Phosphate deposits in Egypt are part of the Duwi Formation, which stretches from the Arab countries in Africa (to the west) to the Arab countries in Asia (to the east).…”