首页|Mafic and felsic magmatism in the Wadi Kalalat area,South Eastern Desert,Egypt:mineralogy,geochemistry and geodynamic evolution during the Neoproterozoic in the Nubian Shield
Mafic and felsic magmatism in the Wadi Kalalat area,South Eastern Desert,Egypt:mineralogy,geochemistry and geodynamic evolution during the Neoproterozoic in the Nubian Shield
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In the south Eastern Desert of Egypt,two con-trasting types of magmatism(mafic and felsic)are recorded in the Wadi Kalalat area,and form the Gabal El Mota-ghiarat and Gabal Batuga intrusions,respectively.The two intrusions post-dates ophiolitic and arc associations repre-sented by serpentinite and metagabbro-diorite,respec-tively.The mafic intrusion has a basal ultramafic member represented by fresh peridotite,which is followed upward by olivine gabbro and anorthositic or leucogabbro.This mafic intrusion pertains to the Alaskan-type mafic-ultra-mafic intrusions in the Arabian-Nubian Shield(ANS)being of tholeiitic nature and emplaced in a typical arc setting.On the other hand,the Gabal Batuga intrusion comprises three varieties of fresh A-type granites of high K-calc alkaline nature,which is peraluminous and garnet-bearing in parts.A narrow thermal aureole in the olivine gabbro of the mafic intrusion was developed due to the intrusion of the Batuga granites.This results in the devel-opment of a hornfelsic melagabbro variety in which the composition changed from tholeiitic to a calc-alkaline composition due to the addition of SiO2,A12O3,alkalis,lithosphile elements(LILEs)such as Rb(70 ppm)and Y(28 ppm)from the felsic intrusion.Outside the thermal aureole,Rb amounts 2-8 ppm and Y lies in the range＜2-6 ppm.It is believed that the Gabal Batuga felsic intrusion started to emplace during the waning stage of an arc sys-tem,with transition from the pre-collisional(i.e.,arc set-ting)to post-collisional and within plate settings.Magma from which the Gabal Batuga granites were fractionated is high-K calc-alkaline giving rise to a typical post-collisional A-type granite(A2-subtype)indicating an origin from an underplating crustal source.Accordingly,it is stressed here that the younger granites in the ANS are not exclusively post-collisional and within-plate but most likely they star-ted to develop before closure of the arc system.The pos-sible source(s)of mafic magmas that resulted in the formation of the two intrusions are discussed.Mineralog-ical and geochemical data of the post-intrusion dykes(mafic and felsic)suggest typical active continental rift/within-plate settings.
Wadi KalalatGabal El Motaghairat mafic intrusionGabal Batuga felsic intrusionArc settingPost-collisionWithin-plate
Adel A.Surour、Ahmed A.Madani、Mohamed A.El-Sobky
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Faculty of Science,Galala University,New Galala City,Suez 43511,Egypt
Department of Geology,Faculty of Science,Cairo University,Giza 12613,Egypt
Egyptian Mineral Resources Authority,P.O.Box 11517,Abbasiya,Cairo,Egypt
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