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214459

Mineral Chemistry and Genesis of Emerald and Beryl Mineralization in the south Eastern Desert of Egypt

Article

Last updated: 01 Jan 2025

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Tags

Environmental chemistry

Abstract

Beryl mineralization in Egypt occurs in the south Eastern Desert and Sinai, occurring in two geologic environments. In the first environment, beryl occurs in phlogopite schist next to contacts with discontinuous muscovite leucogranite and linked to cogenetic pegmatites. Their spatial distribution is a well-defined NW-SE trend district extending ~45 km long and ~9 km wide. This extensive district coincides with the major Nugrus thrust and linked strike-slip shear-zone system. Zabara-Um Addebaa district (Z-UD) resembles this type and the schist hosting emerald in the south Eastern Desert of Egypt is confined to this district. In the second geologic environment, beryl occurs within pegmatite (lenses, bodies, and veins), quartz veins, and disseminated form in alkali feldspar granite; the Homret Akarem-Homret Mukpid district (HA-HMD) resembles this type. In Z-UD, the averages of Al2O3, K2O, CaO, TiO2, V2O3, and Cr2O3, in emerald of phlogopite are higher than those of green beryl either in phlogopite or in quartz veins. It is sodium-rich beryl, as Na2O ranges between 1.74 and 1.96 wt.%. In the studied emerald and beryls, the concentrations of Cr, V, and Fe+2 control the beryl coloration (chromophore). In HA-HMD, the beryl mineralization of Homret Akarem is a whitish and pale green color, while beryl of Homret Mukpid is of pale blue color. The averages of Na2O, MgO, Al2O3, K2O, CaO, MnO, NiO, and Cs2O in Homret Akarem are higher than those of Homret Mukpid. Conversely, the averages of TiO2, V2O3, Cr2O3, and FeO of Homret Akarem are less than those of Homret Mukpid. The pale blue color of Homret Mukpid is attributed to the high content of Fe+2, Cr, and V, whereas the whitish color of Homret Akarem beryl is due to the deficiency of these elements. The genesis of beryl mineralization in Z-UD district is interpreted as a result of the interaction between highly evolved felsic magma (muscovite leucogranite and associated pegmatite) and the pre-existing mafic-ultramafic rocks embedded in mélange matrix (schists). These processes involve the addition of the elements characteristic of a highly evolved granitic assemblage (Be, F, B, P, alkalis) to the ultramafic assemblage that is quite high in Mg, Ti, Cr, Ni, and Cu. Consequently, phlogopite (K-metasomatism) formed at the expense of earlier actinolite (Mg, Ca metasomatism), which released Cr and (or) V giving the green to deep green color. The genesis of beryl mineralization in HA-HM district is attributed to metasomatism by emanation of volatiles exsolved from a deep-seated highly evolved felsic magma source.

DOI

10.21608/ejchem.2022.113700.5166

Keywords

beryl, Emerald, mineral chemistry, Zabara, Um Addebaa, Akarem, Mukpid

Authors

First Name

F.M.

Last Name

Khaleal

MiddleName

-

Affiliation

Nuclear Materials Authority, P.O. 530. El Maadi, Cairo, Egypt

Email

farraggeo68@gmail.com

City

-

Orcid

-

First Name

Lentz

Last Name

D.R.

MiddleName

-

Affiliation

Department of Earth Sciences, University of New Brunswick, Fredericton, NB, Canada

Email

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City

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Orcid

-

First Name

Hall

Last Name

D.C.

MiddleName

-

Affiliation

Microscopy and Microanalysis, University of New Brunswick, Fredericton, NB, Canada

Email

-

City

-

Orcid

-

Volume

65

Article Issue

8

Related Issue

31862

Issue Date

2022-08-01

Receive Date

2021-12-29

Publish Date

2022-08-01

Page Start

601

Page End

623

Print ISSN

0449-2285

Online ISSN

2357-0245

Link

https://ejchem.journals.ekb.eg/article_214459.html

Detail API

https://ejchem.journals.ekb.eg/service?article_code=214459

Order

56

Type

Original Article

Type Code

297

Publication Type

Journal

Publication Title

Egyptian Journal of Chemistry

Publication Link

https://ejchem.journals.ekb.eg/

MainTitle

Mineral Chemistry and Genesis of Emerald and Beryl Mineralization in the south Eastern Desert of Egypt

Details

Type

Article

Created At

22 Jan 2023