| Petrology and Geochemistry of Ophiolitic Mafic Rocks in Wadi El-Mireiwa Area, South Eastern Desert, Egypt |
| Paper ID : 1099-ISCH |
| Authors |
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Hossam Ahmed Selim *, Mohamad Ashraf Ismail Helwan University |
| Abstract |
| The Neoproterozoic rocks of the Wadi El-Mireiwa area in the Eastern Desert of Egypt include metasediments, an ophiolite sequence, an island arc assemblage, and younger granites. The ophiolitic mafic rocks in Wadi El-Mireiwa include ophiolitic metabasalt and metagabbro. Petrographically, the ophiolitic metabasalt are fine-grained and amygdaloidal, composed of plagioclase and chlorite with subordinate opaque minerals. The ophiolitic metagabbro is massive, commonly medium- to coarse grained, with hypidiomorphic granular texture composed of plagioclase and brown amphibole. The opaque minerals are mainly Fe-Ti oxides with minor sulfides. Geochemically, the ophiolitic metabasalt of Wadi El-Mireiwa are low-K subalkaline rocks with tholeiitic affinity. On the other hand, the ophiolitic metagabbros are classified as medium-K rocks with tholeiitic to calc-alkaline nature. On the MORB-normalized spider diagrams, the ophiolitic metabasalt shows enrichment of LILE and most HFSE relative to MORB. Similarly, the MORB normalized spider diagram patterns of ophiolitic metagabbro are characterized by enrichment of LILE and most HFSE. As to tectonic setting and source, the ophiolitic metabasalt and metagabbro are developed along a spreading center showing negligible subduction component; rather they are akin to E-MORB ophiolites and are derived from an enriched mantle source. Yet the geochemical characteristics of the associated ultramafic rocks in Wadi El-Mireiwa area suggest a SSZ setting. This apparent discrepancy can be reconciled by assuming that both ultramafic and ophiolitic mafic rocks were formed in SSZ but the ophiolitic mafic rocks formed along a spreading center located far from the subducted slab or during the earliest stage of subduction. |
| Keywords |
| Neoproterozoic ophiolites, E-MORB ophiolites, Geochemistry, Eastern Desert |
| Status: Abstract Accepted (Poster Presentation) |