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158268

PETROGENESIS OF SELECTED PEGMATITIC BODIES FROM EASTERN DESERT AND SINAI MASSIF, EGYPT

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Last updated: 23 Jan 2023

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Abstract

Selected pegmatitic bodies of simple and complex types (unzoned and zoned) located in the Eastern Desert (ED) and Sinai Massif (SM) have been carefully studied. The simple pegmatites under consideration occur at Wadi Hawashia (northern ED), Gabal El Hudi area (southern ED) and Wadi Dahab (SM) forming irregular lenses and pods. Alkali feldspar, quartz and muscovite pockets represent the essential mineral constituents. On the other hand, the complex types of zoned nature occur at Gabal Abu Dob (central ED) and Wadi Um Shoki (SM) forming sheets and dyke-like appearance. They constitute a sequence of mineral assemblage from the contacts inward as follows: alkali feldspar ± mica pockets followed by graphic quartz and quartz megacrysts at the core. Almost all pegmatitic bodies invade granitoids with a mild contact effect (if present). Petrographically, the pegmatites are granitic (comprise alkali feldspar granite constituents as perthite, microcline perthite, quartz ± mica) and perthitic (string, patch and net types of perthite are the main mineral constituents). Allanite, zircon, apatite, cassiterite and uranophane are mostly accessories. Geochemically, almost all pegmatites have metaluminous to peraluminous nature and are characterized by their high alkali contents (up to 12 wt%) as well as low CaO contents (<1.0 wt%). Regarding to mineral chemistry, the perthite analyzed lies in the field of alkali-feldspar-rich rocks. Composition of Mg-mica (manganophyllite) is distinguished by elevated abundances of alumina, magnesia and manganese contents. Textural and mineralogical features of manganophyllite suggest late-crystalized phase with variable degrees of metasomatism of an initial source rock. It is quite clear from the field, petrographic and geochemical studies of the present pegmatites that these rocks seem to be strictly of magmatic nature in one hand and in combination with metasomatism associated with volatile input in another hand.

DOI

10.21608/djs.2005.158268

Authors

First Name

Mohamed T.S.

Last Name

Heikal

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Affiliation

Geol. Dept. Fac Sci. Tanta Univ., Tanta, Egypt

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First Name

S.A.

Last Name

Awad

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Affiliation

Geol. Dept. Fac. Sci. Ain Shams Univ., Cairo, Egypt

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Orcid

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First Name

I.E.

Last Name

Aassy

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Affiliation

Nuclear Materials Authority, Cairo, Egypt

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Orcid

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First Name

S. E.

Last Name

Ammar

MiddleName

-

Affiliation

Nuclear Materials Authority, Cairo, Egypt

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First Name

E.K.

Last Name

Abu Zeid

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-

Affiliation

Nuclear Materials Authority, Cairo, Egypt

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Volume

29

Article Issue

2

Related Issue

22908

Issue Date

2005-12-01

Receive Date

2021-03-21

Publish Date

2005-12-01

Page Start

156

Page End

184

Print ISSN

1012-5965

Online ISSN

2735-5306

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https://djs.journals.ekb.eg/article_158268.html

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https://djs.journals.ekb.eg/service?article_code=158268

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21

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Research and Reference

Type Code

1,686

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Journal

Publication Title

Delta Journal of Science

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https://djs.journals.ekb.eg/

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Article

Created At

23 Jan 2023