Petrology and Zircon morphology of granitoid rocks at um Bogma Environs, south west Sinai, Egypt

Document Type : Research and Reference

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assistant lecturer at the nuclear materials authority, geology department

Abstract

This paper studies the morphology of zircon crystals as well as geological and petrographical characteristics of granitoid rocks at Um Bogma environs, south Sinai, Egypt to provide the rock nomenclatures and to deduce their origin and magma types. The field relations and observations display the presence of different masses of granitic intrusions represented by older and younger granites. Based on modal mineral compositions, the granitoid rocks are classified into tonalite, quartz diorite, monzogranite, syenogranite and alkali feldspar granite. Commonly, zircon is the most abundant accessory mineral in the studied granitic rocks, which exhibits well crystalline and metamict forms.The morphologic examination of zircon crystals show some characteristic features including color, regular oscillatory zoning, metamictization, fracturing, volume expansion and alteration. The typologic investigation of zircon population discriminates between different petrographic types of granites, where in tonalites S13and S22 are the dominate types whereas in quartz diorite, S8 and S12 types of zircon are the most predominant types. Zircon of S8 type is the most predominant type in monzogranite, whereas P3 and P4 Zircon types are the most predominate in syenogranite. The most abundant zircon types in alkali feldspar granite are P5 and P4. Zircon investigations display that the quartz diorite has aluminous nature comparable with S-type granite, while tonalite, monzogranite and syenogranite have calc-alkaline affinity similar to I-type granite. On the other hand, the alkali feldspar granite has alkaline nature of A-type granite.

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