The area around G. Um Khors (150 Km 2 ) is located in the middle of the basement 
complex of the Central  Eastern Desert, Egypt,  south of the  Qift-Quseir road. Um  Khors 
trachyte plug (bostonite sill) represents the youngest major rock unit in the district and was 
intruded  into  heterogenous  country  rocks  pertaining  to  the  ultramafics,  metagabbros, 
volcanogenic  metasedimentary  and  molasse-type  sediments  (Hammamat  group).  The 
contacts of  this  plug  against the  above  country  rocks are  invariably  sharp.  They  include 
mainly  porphyritic  sanidine  and  aegirine-ribeckite  trachytes.  Both  exhibit  pronounced 
porphyritic and trachytic textures. They consist essentially of phenocrysts of sanidine and 
orthoclase  set  in  a  groundmass  composed  of  fine  potash  feldspar  laths  together  with 
opaques  and  interstitial  quartz.  Um  khors  were  subjected  to  diagenetic  deuteric  activity 
activity  by  a thermal event, possibly during the intrusion of the bostonite sill, which caused 
set    of    complicated    alterations    including    hematitization,    carbonization,    pyritization, 
kaolinitization  and  among  others.  The  geochemical  features  of  the  mantle  source  of  the 
studied   trachytes   are   strongly   evident,   in   which   these   volcanics   represent   highly 
fractionated  melts   involving   fractionation   of  feldspar,   clinopyroxene   and   opaques. 
Detailed   spectrometric   study   reveals   the   eU/eTh   ratio   varies   directly   with   eU 
concentration  and  randomly  with  eTh,  indicating  that  the  radioelement  concentration  is 
governed by post magmatic redistribution. The high level of radioactivity in bostonite sill 
is attributed to the presence of the radioactive minerals uranophane, beta- uranophane (U-
silicate),  thorianite,  zircon,  fluorite  and  allanite  as  confirmed  by  XRD  analysis.  The 
mineralogical  study  of  the  samples  revealed  the  presence  of  niobian-tantalan  rutile, 
microlite, sphalerite, pyrite and bornite.