الفهرس 
GEOLOGICAL SETTINGOnly 14 pages are availabe for public view
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Abstract
The study area (W. El Gemal -W. Sikait area) is located at the southern
part of the Eastern Desert of Egypt at about 50 km south of Marsa Alam
coastal city. It is easily accessible through the Red Sea Highway (Marsa
Alam-Halayb coastal asphaltic road) and then extends westward at the
eastern entrance of W. El Gemal desert track and is included in the protected
area. The main aim of this thesis is to study geology, geochemistry, and the
application of remote sensing imagery for studying the potentiality of
mineralization in the W. El Gemal-W. Sikait area.
The area was not previously subjected to discriminating its lithology and
mapping through remote sensing data. Consequently, Landsat-8 OLI data
was chosen in the present study because the Swath width is 185 km and
therefore it is useful in the regional mapping.
Fieldwork was carried out at W. El Gemal-W. Sikait area for sampling,
descriptions, photographs of the exposed lithological units, the different field
observation relationships between the rock units, and verified remote sensing
data for a good mapping. Moreover, the main rock units of the study area are
arranged from older to younger as follows: The gneiss rocks, ultramafic
rocks, ophiolitic metagabbros, ophiolitic mélange, metasedimentsmetavolcanics association, older granites, younger gabbros, and younger
granites. All the previously mentioned rock types are mostly traversed by
post-granite dykes and veins.
Petrographically, the metagabbro rocks are composed of plagioclase,
hornblende, actinolite, biotite, and quartz. Titanite and opaques are
accessories. Epidote and chlorite are secondary minerals. The metasediments
are represented by actinolite schist, hornblende schist, and biotite hornblende
schist. Actinolite schist is composed of actinolite, hornblende, quartz, and
plagioclase. Opaques and antigorite are the accessory and secondary
III
minerals respectively. Hornblende schist is composed of hornblende,
plagioclase, quartz, and augite. Opaques and apatite are accessory minerals.
Chlorite and saussurite are secondary minerals. Biotite hornblende schist is
composed of hornblende, plagioclase, biotite, and quartz. Titanite and
opaques are accessory minerals, whereas chlorite occurs as a secondary
mineral. Metavolcanics are represented only by metadacite and are
composed of plagioclase, quartz, K-feldspar, and biotite. Titanite and
opaques occur as accessory minerals. Epidote is a secondary mineral. The
granitic rocks are represented by older granites (quartz diorite and
granodiorite) and younger granites (biotite granite). Quartz diorite is
composed of plagioclase, quartz, biotite, and K-feldspar. Titanite, zircon,
apatite and opaques are accessories. Chlorite and saussurite are secondary
minerals. Granodiorite is composed of plagioclase, quartz, K-feldspar,
biotite, and hornblende. Zircon, titanite, apatite, and opaques are accessories.
Chlorite and sericite are secondary minerals. Biotite granite is composed of
K-feldspar, quartz, plagioclase, and biotite. Zircon, titanite, apatite, and
opaques are present as accessories. Chlorite existed as a secondary mineral.
Geochemical characteristics were carried out through the analysis of 19
samples of the metagabbros, hornblende schist, metadacite, and granodiorite
and biotite granite for major oxides, trace, and REEs. Geochemical studies
indicated that the metagabbro rocks are tholeiitic to calc-alkaline either
formed in the MORB setting modified by arc-related magmas or formed in
back-arc environment and display subduction zone trace element signatures
as a variable enrichment of LILE over HFSE, LREEs over HREEs and
negative Nb anomalies. The investigated hornblende schist samples are Feshale immature material derived from andesitic arc source rock formed in
oceanic island arc setting. The REE pattern of the hornblende schist samples
shows approximately strong enrichment of the LREEs relative to HREEs
with positive Eu anomaly. The metadacite are calc-alkaline metaluminous
IV
formed in the active continental margin setting. The REE pattern of
metadacite samples displays a flat pattern with slight enrichment of the
LREEs relative to HREEs and negative Eu anomalies. The investigated
samples from older granites (granodiorite) are calc-alkaline peraluminous
formed in volcanic arc setting, while the younger granites (biotite granite)
are shoshonitic peraluminous formed in post-collision setting. The
investigated granitic samples show enrichment of LREE relative to HREEs
with positive and negative Eu anomalies for granodiorite and biotite granite
respectively. The biotite granite REEs pattern shows less fractionated
LREEs and HREEs relative to granodiorite. High abundances of LREEs in
granodiorites are compatible with the presence of allanite accessory mineral
observed petrographically contrary to high a bundances of HREEs observed
in biotite granite which may be due to the presence of zircon-bearing HREEs.
A Field radiometric survey has been carried out by “RS-230 gamma-ray
spectrometer” for eU (ppm), eTh (ppm), and K%. The radiometric survey
was greatly compatible with the alteration maps, where areas that
significantly have higher iron oxides and hydroxides (hematite Fe2O3 and
goethite FeO-OH) content. The gneiss rocks at W. Abu Rusheid have a
higher radioactive content than granite rocks that appear at W. El Gemal and
W. Abu Rusheid area. The radioactive content of granite rocks was natural,
except the mineralized biotite granites at W. Abu Rusheid area show very
high anomalies compared with other granite rocks at W. El Gemal and W.
Abu Rusheid area.
The heavy minerals were separated using heavy liquid (bromoform)
separation technique from selected samples and picked under a binocular
microscope and identified by Scanning Electron Microscope, energy
dispersive spectrometry (SEM-EDX) technique. The identified minerals
from the different anomalies in the rock types are gold, pyrite, ilmenite,
galena, zircon, allanite, columbite, and apatite. The occurrence of gold
V
mineralization as fine-grained gold association with pyrite in metagabbro
rocks suggests their formation as a result of chemical interaction between the
hydrothermal solutions and the host rocks. where the interaction of the
sulfur-bearing fluid with the iron-bearing host rocks form pyrite (FeS2) in
cubic shape is an effective process, whereas the fined-grained gold was
precipitated associated with pyrite at the contact between metagabbro rocks
and metasediments-metavolcanics association