Origin and geochemical characteristics of beryllium mineralization in the Zabara-Wadi El Gemal region,South Eastern Desert,Egypt  

作　　者：Gehad M.Saleh Farrage M.Khaleal Mohammed Z.El-Bialy Mohamed S.Kamar Mokhles K.Azer Mohamed M.Omar Mohamed N.El Dawy Ahmed Abdelaal El Saeed R.Lasheen 

机构地区：[1]Nuclear Materials Authority,El-Maadi,P.O.Box 530,Cairo,Egypt 2 Geology Department,Faculty of Science,Port Said University,Port Said 42522,Egypt 3 Geological Sciences Department,National Research Centre,Cairo,Egypt 4 Environmental Sciences Department,Faculty of Science,Port Said University,Port Said 42522,Egypt 5 Geology Department,Faculty of Science,Al-Azhar University,P.O.Box 11884,Cairo,Egypt

出　　处：《Acta Geochimica》2024年第6期1105-1122,共18页地球化学学报（英文）

摘　　要：Beryl is the commercial source of beryllium and several varieties of it are valued as a gemstone.To contribute to understanding the mechanism of beryl formation,we carried out detailed geological,petrographical,and geochemical investigations on beryl mineralization occurrences in the Zabara-Wadi El Gemal(Z-WG)region.This region is an NW-SE trending tract that includes six berylhosting areas.The green gem variety of beryl(emerald)is restricted to phlogopite schist,pegmatite,and quartz veins.Prismatic hexagonal emerald crystals are well-developed in phlogopite schist and pegmatite.The gem variety emerald examined is sodic and Cr-dominant.It contains high concentrations of chromophore transition elements ordering Cr(up to 1511 ppm)>V(up to 242 ppm)>Sc(up to 245 ppm),giving rise to its vivid green color,refl ecting mafic-ultramafic source contribution.Among the investigated emeralds,the Sikait area contains the highest BeO(av.10.76wt.%)concentration.The compositional variability of emeralds is most likely attributed to the contribution from the host rocks.This is revealed by the examined emerald mineralization,for instance;the Abu Rusheid area(one of the best areas exposing rare metal-bearing granitoids)possesses the highest average of trace and REEs concentrations.In contrast,Um Kabu emerald has the highest contents of Co(av.20 ppm),Ni(av.299 ppm),MgO(av.8.2wt.%),Fe_(2)O_(3)(av.3.12wt.%),and CaO(avg.3.4wt.%)relative to other areas,which may be linked to contribution of ultramafic rocks exposed there.The proposed mechanism we suggest for emerald genesis is metasomatic interaction between felsic intrusions,that are enriched with K,Na,Be,Li,and B,with mafic-ultramafic rocks that are enriched in Cr,V,Mg,Fe,and Ca.This interaction is marked by the formation of phlogopite schist,the growth of emerald crystals,and desilicated pegmatite.

关 键 词：Beryl chemistry Emerald genesis Phlogopite schist PEGMATITE Eastern Desert 

分 类 号：P618.72[天文地球—矿床学]