International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004 
  
3. RESULTS AND DISCUSSION 
3.1 Lithologic interpretation 
Lithological formations of Wadi Um Laseifa area were identified 
from the analysis and interpretation of Landsat TM data, as well 
as the field study. This area is covered by Pan African 
Precambrian basement rocks and overlain by Phanerozoic 
sedimentary rocks (Fig. 2). 
The Pan African rocks are arranged from oldest to youngest 
as follows: ophiolitic ultramafic rocks, ophiolitic melange, 
metavolcano-sedimentary rocks, metavolcanic rocks, gabbro- 
diorite rocks, granodiorites, Hammamat sediments, calc-alkaline 
and alkali granites. These rocks are injected by pegmatite and 
quartz veins as well as felsitic and trachytic dykes . 
Phanerozoic rocks are outcropping in the eastern flank of the 
area and represented by Miocene sediments (Gabal El Rosas, Abu 
Dabbab. Essel and Sharm El Bahari formations), Pliocene 
sediments (Gabir, Shagara and Wizr formations), Pliestocene (Um 
Gheig Formation) and Quaternary deposits (Fig. 2). 
3.2 Radioactive occurrences 
The identified radioactive anomaly sites are classified into three 
groups according to their main trend and their host rocks. 
- The first group trending NNE-SSW and associated with the 
alkali-granite, trachytic dykes, felsitic plugs and pegmatitic 
veins at Gabal Hamrat Ghannam, Gabal Dileihimi, Gabal 
Abu El Tiyur respectively. 
- The second group trending NNE-SSW and associated 
with the manganese veins which injected the granitic rocks at 
Gabal Abu El Tiyur. 
Table (1) gives the concentration of the different radionucleides 
in ppm for U and Th in ppm of both groups. 
- Thethird group trending NNW-SSE associated with the 
Miocene sediments at the area between Wadi Sharm El 
Bahari and Wadi Um Greifat (Ramadan, et al., 1999). 
The following is brief description for these sites 
according to host rocks. 
3.2.1 Radioactive associations with the granitic rocks: This 
type of radioactive anomalies is associated with the alkali-granite, 
trachytic dykes, felsitic plugs and pegmatitic veins. 
a. Gabal Hamrat Ghannam area 
This area is covered by granodiorites and intruded by biotite and 
alkali granites. Several trachytic dykes trending 20° N and cut 
these rocks. The delineated radioactive anomalies having U > 50 
ppm occur within the alkali granite and trachytic dykes in the 
southern part of Gabal Hamrat Ghannam (Lat. 25° 52 20” N and 
Long. 34? 16” 30” E). These trachytic dykes reach up to 50 m in 
thickness and up to 2 km in length and trending NNE-SSW (Fig. 
3). Gamma ray readings of the scintillometer in the granodiorites 
are ranging from 40 to 50 c/s, from 130 to 150 c/s in the alkali 
granites and from 160 to 190 c/s in the trachytic dykes at 
sensitivity 500. The HPG measurements of U and Th in the 
trachytic dykes show that the contents of U range from 3.2 to 10 
ppm, and Th from 10 to 18 ppm (Table - 1). 
b. Gabal Dileihimi area 
This area is covered by granodiorites and intruded by biotite and 
alkali granites. Several felsitic and trachytic dykes cut these rocks 
and trending 20? N. The delineated radioactive anomalies having 
U > 50 ppm occur in the alkali granite and trachytic dykes in the 
northern part of Gabal Dileihimi. Gamma ray readings of the 
scintillometer in the granodiorites are ranging from 40 to 50 c/s 
and from 150 to 170 c/s in the alkali granites. 
c. Gabal Abu El Tiyur area 
This area is covered by biotite and alkali granite. Numerous 
felsitic dykes trending — N-S cut these rocks. The delineated 
radioactive anomalies having U > 50 ppm occur within alkali 
granite and felsitic dykes in the northern part of Gabal Abu El 
Tiyur (Lat. 25° 45' 05" N and Long. 34° 15' 15" E). The readings 
of the scintillometer in the felsitic dykes are ranging from 175 to 
200 cfs. 
d. Gabal Nusla area 
This area is covered by granodiorites and intruded by biotite and 
alkali granites. Several felsitic dykes and pegmatitic veins 
trending 20° N are injected in these rocks. The delineated 
radioactive anomalies having U > 50 ppm occur wihin felsitic 
dykes and pegmatitic veins at the northern part of Gabal Nusla 
(Fig. 3) The readings of the scintillometer in the granodiorites are 
ranging from 140 to 150 c/s. The HPG measurements of U and 
Th in the pegmatitic veins show that: the contents of U range from 
9.7 to 17.2 ppm, and Th from 23 to 36 ppm (Table - 1). 
e. Wadi Maktal Mohamad: 
A radioactive anomaly, where U exceeds 50 ppm, is recorded at 
the upper reaches of Wadi Abid, representing the northern 
tributary of Wadi Maktal Mohamad. At this site, a felsite plug cuts 
the gabbroic rocks and is partially covered with Miocene clastic- 
carbonate formations. In this felsitic plug, the readings of the 
scintillometer range from 150 to 160 c/s. 
3.2.2 Radioactive anomalies within the manganese veins: 
Several manganese veinlets injected the granitic rocks of Gabal 
Abu El Tiyur at its eastern side trending N-S. These veins reach 
up to 2 m length and 3 cm width. The readings of the 
scintillometer are ranging from 175 to 200 c/s. The measurements 
of U and Th in the manganese veins show that: the contents of U 
range from 0.9 to 9 ppm and Th is less than the detection limit of 
the gamma spectrometer (Table - 1). 
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