Geology and geochemistry of Neoproterozoic basement rocks at Um Had area, Central Eastern Desert, Egypt | ||||
| Al-Azhar Bulletin of Science | ||||
| Volume 2024, Issue 1, January 2024 | ||||
| DOI: 10.58675/2636-3305.1666 | ||||
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| Authors | ||||
| Ibrahim Fangary1; Ahmed Orabi2; Abdellah Tolba2; Mostafa Abd Elghany1; Lotfy Mohamed1 | ||||
| 1Geology Department, Faculty of Science, Al-Azhar University, Assiut Branch, Egypt | ||||
| 2Geology Department, Faculty of Science, Al-Azhar University, Assiut Branch, Egypt. | ||||
| Abstract | ||||
| The study aims to identify and classify the Neoproterozoic rocks located in the Um Had area of Egypt's Central Eastern Desert using geological and geochemical assessments. These rocks originated during synorogenic and late to post-orogenic stages. The synorogenic rock assemblages include serpentinite (ophiolitic rocks) that is depleted from harzburgite protoliths, generated from ultramafic komatitic magmas, extruded by rhyolite and intruded by syenogranite, with the presence of metavolcaniclastics, metavolcanics, and metagabbro (island arc rocks); the metavolcaniclastics are calc-alkaline to subalkaline in affinity, overlaid by the Hammamat and intruded by the monzogranite, while meta-volcanics are developed in island arc and mid-ocean environments with subalkaline and calc-alkaline natures and undergo metamorphism at low temperatures of around 300 oC and pressures of less than 3 kb, They are intruded by quartz diorite and syenogranite; however, the tholeiitic and subalkaline metagabbroic rocks are formed in the ocean ridge and floor region and extruded by the rhyolite. The late to postorogenic rock assemblages include monzogranite, syenogranite, and granodiorite which are covered by Hammamat sediments and intruded in older granites and meta-volcanics. These granites are all of the I-type, which developed from calc-alkaline and metaluminous to mildly peraluminous magma in the post-orogenic granitoid setting at temperatures of between 730 and 760 oC and pressures between 1 and 5 Kb. Furthermore, these late to post-orogenic rock assemblages comprise the Hammamat sediments and Dokhan volcanics; the Dokhan volcanics are of rhyolitic composition, expose high potassic nature, and vary from subalkaline to calc-alkaline magma that is crystallized within active continental margins, whereas the Hammamat sediments are the region's youngest rock unit, undergoing little chemical weathering and are originated from felsic and mafic rock fragments that were deposited in intermontane basins in passive margin and island arc setting. | ||||
| Keywords | ||||
| Egypt; Field investigations; Geochemistry; Island Arc; Late to post-orogenic rock assemblages; ophiolite | ||||
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