Download Mineral chemistry of different late and post orogenic granitic rocks

Mineral chemistry of different late and post orogenic granitic
rocks surrounding Gabal Abu Kharif, North Eastern Desert,
Egypt.
I . Abu El-Leil(1) , A.Orabi(1), A. Tolba(1) and A. Abdel-Shafy(2)
(1) Al-Azhar University- (2) Nuclear Material Authority (NMA).
Abstract:
Field geologic investigation of Gabal Abu Kharif area reveals that
the examined basement rocks are chronologically related to early Pan
African, late Pan African and post Pan African stages. The early Pan
African comprises metavolcaniclastics and metavolcanics. The late Pan
African comprises different types of granite (tonalite, granodiorite and
monzogranite) as well as some related dykes and veins. The Post Pan
African anorogenic stage comprises the riebeckite granite that occurs as
limited few plutons.
The chemical analyses of plagioclase, biotite, hornblende and
riebeckite, sphene, apatite, allanite, zircon, epidote and iron oxides were
determined by using the Environmental Scanning Electron Microscope
(ESEM). The purpose of the study is the chemical formula of these
minerals to be in certain condition. Mineral chemistry of plagioclase
indicates that has albite-oligoclase composition for late orogenic granites
and albite for post orogenic granite, it had been crystallized at
temperature 748º - 900ºc and the chemical formula can be recognized by
(K, Na, Ca)4 (Si, Al)16 O32. Biotite crystals are related to plutonic types
for the late orogenic granite. The chemical formula of the study
hornblende is expressed as Ca2Mg4AlSi7O24. The post orogenic granite
include also riebeckite mineral, the analysed is nearly coincident with the
composition of common riebeckite Na2Fet4Si8O22 (OH, F)2.