الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The area under investigation covers about 12000 Km2 in the
southeastern part of Eastern Desert of Egypt, It is located between
latitudes 22° 10’ and 23° 50’ Nand logititudes 34° 30’ and 35° 30’ E. It is
characterizedby arid to semi arid climatic conditions.
Geomorphologically:Five geomorphicunits are recognized.
1-Red Sea mountains
This unit is mainly composed of crystalline basement rocks,
running parallel to the Red Sea coast and forming the main water divide
between Red Sea and Nile valley drainage systems.
2- Sandstone Plateau
Such unit is located in the northwestern part of Wadi Hodein,
including Gebel Abraq, Gebel Hodein, Gabal Kalat and Gebel Sa’alik.
3- Tectonic depressions:
These depressions are oriented in NW -SE and formed along the
grabbensstructure.
4- Tertiary volcanic ridges
Tertiary volcanic ridges occur between Red Sea Mountains and
piedmontplains.
5- Piedmont and coastal plains
They extend from Red Sea coast to the inland mountainous area
representing moderate sloping and covered by poorly sorted alluvial
deposits.
Geologically, The area under investigation comprises a wide diversity
of igneous, metamorphic and sedimentary rocks, ranging in age from
Precambrian to Quaternary. The rocks units in the area are
chronologically grouped into the following main sequences from oldest to
younger : 1-Precambrian Basement rocks.
-Gneisses and metasediments.
-Ophilitic serpentinites and related rocks.
-Metagabbros.
-Metavolcanics.
-Old granitoides
-Younger granitoides.
-Ring related rocks.
2-Cretaceous Sediment.
-Abu-Aggag Formation.
-Timsah Formation.
-Urn Baramil Formation.
3-Quatemary sediments.
Hydrogeologically, the study area comprises three water- bearing
formations :-
• Quaternary alluvial aquifer
• Upper Cretaceous Nubian Sandstones aquifer
• Precambrian Basement rocks
Such aquifers were investigated through 39 water points. Also, 61
water samples were collected and chemically analyzed during two field
hips.
Quaternary Groundwater exists in the main delta of Wadi Hodein
and in the main channel of the delta of subsidiaries wadies draining to
Wadi Hodein mega basin. Seven water wells are tapping the Quaternary
aquifer. Four of them in the Delta of Wadi Hodein. Two at Wadi Eigad
(tributary of Wadi Beitan) and only one at Wadi Urga El-Rayani. The
groundwater exists as free water table. The depth to water ranges from
6.23 in. to 23.86 m. The general direction of wound water flow is in the
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same direction of surface runoff. The Quaternary aquifer in the area under
investigation is mainly composed of wadi fill deposits including silt, sand
and gravel. It is distributed along the main wadi channels and in the
deltas.
The Upper Cretaceous aquifer is represented at northwestern part
of the area (Wadi Abraq, Wadi EI-Dif and Abu-Saafa area). Three waterbearing
formations namely Um-Bannil, Abu-Agag and Timsah are
recognized and mainly composed of sandstone intercalated with shale and
iron ore deposits and underlain by basement aquifer. The aquifer is
composed of block-faulted sandstone, slightly folded and mainly affected
by the Red Sea rift; Such blocks are acting as independent isolated
aquifers. Twenty goundwater samples are tapping the aquifer, eight of
them as springs, five hand-dug wells and seven as drilled wells.
Groundwater exists as a free water table, however gravity springs are
recognized at Abu-Saafa, Abraq and El-Goderate springs. The
investigated aquifer is mainly recharged from surface runoff as well as
direct precipitation during tolerant floods. Concerning drilled and handdug
wells, the depth to water ranges between 2.5 m. to 23.5 m. at El-
Sunta and Wadi EI-Dif areas, respectively.
Groundwater trapped in the Pre-Cambrian aquifer includes
variable bearing rocks, scattered in different wadis as granite rocks at
Wadi Madi, syenitic rocks at Wadi Arnrite, metagabbroic and peissic at
Wadi Behan, metavolcanic at Wadi El-Beida and the upstream of Wadi
Rahaba, and metasedimentary at Wadi El- Beida. The depth to water
ranges from 2 m. to 10.7m.
A detailed geochemical rock analyses were performed for 18 fresh
and their altered equivalents from different basement water bearings.
These samples were analyzed for major and some trace elements to show
the distribution of the mobile elements and their relation to the redistribution of these elements and their effect on the woundwater
quality. The significant features of these studies show a strong depletion
ofMgO, CaO, Na20, K20 and some tiines ofFe203.
Moreover a petrographical and X-ray diffractions studies were
carried out to investigate the mineralogical content of different waterbearingrocks.
Groundwater chemistry of the Quaternary aquifer depends
mainly on its location to sea, where the groundwater located at the
downstream portion of Wadi Hodein is characterized by high salinity
while groundwater at the upsh-eam portion of Wadi Hodein is
characterized by low. The gioundwater salinity in this aquifer varies from
brackish to highly saline, it ranges between 1363.76 mg/I at Wadi Eigad
to 19353.19mg/l in DeltaWadi Hodein.
The distribution of major and trace ions in the woundwater located
at the upstreain portion of Wadi Hodein depends mainly on the types of
different rocks, located closed to the shed area of each wadies, where the
groundwater in Wadi EI-Urga is directly affected by the ganitic rocks
characterized carbonate veinlets (sodium is the dominance cations
(95.31 %)) and bicarbonate is the dominance anion (40.75%), while
groundwater at Wadi Eigad is directly affected by the presence of
serpentinite rocks, located at the shed area, where records magnesium
(40.69%).
The groundwater chemical types varies from chloride-calcium in
the groundwater of Delta Wadi Hodein, reflecting the impact of marine
deposits on the gioundwater chemistry to chloride-sodium in groundwater
of Wadi Eigad, showing final stage of igoundwater evolution and
bicarbonate-sodium in groundwater of Wadi EI-Urga. Groundwater
within the coastal area is characterized by the presence ofMgC12 and CaC12 while the groundwater located at the upsteam is characterized by
Mg(RC03) 2 and Ca (RC03) 2 salts.
Groundwater of Delta Wadi Hodein is charactersed by very low
rNa’ rMgt2/rCa12, rS04-2/rCar2, rCl/rl3f, rBr7l, and rCl/rC03-
2+HC03- and high Cat2INa+, IV/CI and Srt2/Cl- are high values if they
are compared with the same parameters of seawater (Table, ). Besides,
the strong negative BEX (ranged between -16 and -21) ifit compared
with seawater (-5.89). In addition, the enhanced a and St+2 contents in
the same samples indicate that, they have identical source. The different
spatial distribution of cr in the wells suggests a considerable
heterogenity in the aquifer material, which is probably the result of
fluvio-marine environment. Thereby, the possibility of any sipificant
seawater infiltration is excluded. The main source of salinization is the
leaching of the residual old saline water and dissolution of sablcha
deposits.
Groundwater samples of the Quatemaiy aquifer at the upstream
portions have high rNa+ICl-, rMg+2/rCa+2, rS04-2/rCa+2, and Bt3/Cl- and low rClirBr+3, rff/rC03 + HC03 ratios, if they compared with the similar
parameters of seawater. Besides, they have positive BEX (ranges between
11.4 and 16.7) indicating aquifer freshening. The main sources of
salinization are dissolution of minerals due weathering and alteration with a consequentevaporationand concentrationof salt processes.
Chemistry of Nubian sandstone groundwater depends mainly on
the type of sediment origin which varies from continental, near shore
marine to deltaic deposits. The groundwater salinity of Nubian Sandstone
aquifer varies from fresh to moderately saline, which is ranges from
287.56 mg/l at Abu-Saafa area to 3137.15 mg/l at the down stream
portion of Wadi Amrite
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Distribution of major ions in the groundwater of Nubian Sandstone
aquifer is directly affected by the presence of near shore to deltaic
deposits, where sodium appears as the major cations, while chloride
appears as the major anion. Ca+2 ions increased in groundwater at Abudobisat
area, where carbonate between sandstone grains, as cement
material (field observation), S04-2 ions increased in groundwater at the
down stream of Wadi Amrite due to the presence of gypsum encountered
in clay sheets, while HC03 increases in shallow groundwater, where
appreciableamount of recent recharge is available.
The concentration of iron in the groundvvater is directly affected by
the presence of oolitic iron ore deposits encountered in Timsah
Formation.
Groundwater chemical types varies from Bicarbonate-Sodium in
most of shallow groundwater (Abraq, Gumbite, Abu-Saafa and Wadi El-
Dif areas), Bicarbonate-Calcium (Abraq and E-Sunta areas). Chloride-
Sodium characterizes most of drilled wells (Wadi EI-Dif, Abu-Saafa
areas) and chloride calcium characterizes shallow groundwater at Abu-
Dobisat area.
The majority of Groundwater in the concerned aquifer is
characterized by the prevalence ofNaCI, Na2S04, NaHC03 or
Mg(HC03)2 and Ca(HC03)2 salts, while groundwater at El-Sunta, Abu-
Dobisate and Abu-Shafa localities is characterized by NaCI, MgCI2,
MgS04, CaS04, andCa(HC03)2salts.
The groundwater salinity of the Pre-Cambrian aquifer in the area
under investigation varies from fresh to moderately saline. Values of
salinity in the concerned aquifers range from 382.72 mg/I at EI-Gahlia
area to 8860.53 mg/1 at Wadi El-Beida. Lower salinities are recorded
where a limited chance for leaching and dissolution, (water wells are
located at the upstream portion of Wadi Rahaba). In addition, the
presence of dissected dykes, acts as a groundwater entrapment, giving
more chance for recharge and replenislunent of groundwater. The higher
salinity (8860 mg/I) in metasedimentaiy rocks is mainly due to the
reusability of metasediments for leaching. The groundwater chemical
types varies from, Also the higher salinity of goundwater trapped in
gneissic rocks is mainly attributed to the foliation and lineation, which
characterizesthese rocks.
Groundwater trapped in metavolcanic rocks at EI -Gahlia area
ganitie rocks at Wadi Madi and syenitic rocks at Wadi Amrite is
characterized by the prevalence ofNaCl, Na2S04, NaHC03, Mg (HC03)2
and Ca(HC03)2, salts (58% of total samples) while the groundwater
trapped in metagabbroic and gneissic rocks is characterized by the
presence ofNaCl, MgC12, MgS04, Mg(HC03)2 and Ca(HC03)2 salts(25%
of total samples). Groundwater in metagabbroic rocks at Wadi Beitan,
differs slightly, as appearance of CaS04 while Mg(HC03)2 disappears.
The presence of magnesium salts in groundwater is mainly attributed to
the presence of serpntinite rocks at the shed area of Wadi Beitan. In Wadi
El-Beida NaCl, MgC12, CaC12,MgS04, CaSO.4and Ca(HC03) , appear
(16%). This assemblage characterizes saline groundwater in metavolcanic
bearing foimation at Wadi El- Beida and saline groundwater in
metasedimentary rocks. Presence ofMgC12 and CaC12salts reflects final
stage of groundwater evolution. In metavolcanic rocks, CaC12 salt
disappears.
The groundwater chemical types varies from Chloride-Sodium,
characterizing groundwater in Wadi EI -Beida and groundwater in
metagabbroic and Bicarbonate-Sodium characterizing groundwater in
inetavolcanic rocks at EI-Gahlia area, granitic rocks and Syenitic rocks.
Bicarbonate-Magiesium characterizes groundwater trapped in
metagabbroic and metavolcanic rocks. Chloride-Magnesium, this type is
detected in groundwater trapped in gieissic rocks at Wadi Beitan .
The petrographical and geochemical studies revealed that, the
basement rocks in the investigated area comprise different rock units,
each of them has its own mineralogical and geochemical characteristics.
Some effective secondary minerals were formed due to water-rock
interactions phenomena (e.g. Kaolin, sericite, chlorite, saussurite and
carbonate veins). Such minerals play the most important role in the
mobility of major component (e. g. Na, K, Ca, Mg, Fe, and Si02) and in
tum affects groundwatercomposition.
The study of groundwater composition of the Basement aquifer
reveals the following:
1. Seven groundwater samples have NaHC03 water type of shallow
meteoric genesis, while four groundwater samples have MgC12 water type
of marine origin. The presence of MgC12 water type indicates intensive
evaporation process, which elevate CT concentrations relative to IC, Naand
MgT2
2. High bicarbonate concentrations in the majority of groundwater
samplesreflects leaching of talc carbonaterocks at the upstream portion.
3. Groundwater composition in metavolcanic rocks at El-Gahlia area
reflects high concentrations ofNa’ and Mgr2 compared to Ca-2 content.
High Nat content is attributed to the dissolution ofNa-plagioclase
(andesine) and sodalite minerals (X-ray investigation). High Mg+2
contents are refeffed to the dissolutionof biotite minerals.
4. Groundwater composition in metavolcanic rocks at El-Beida area
reflects high concentrations of Nat, CaT2 and Mg+2. Very high Nat
content is attributed to the dissolution ofNa-plagioclase minerals and high evaporation rate. Weathering and alteration of amphiboles and
pyroxenes may contribute to Ca-r2 and Mgl-2 concentrations. This is
confiimed by the sausritization of plagioclase and alteration of
ferroinagnesian minerals.
5. Groundwater composition in metagabbro at Wadi Beitan has high
concentrations of Cal-2, Na+ and Me. High Cal-2 contents are attributed
to the dissolution of Ca-plagioclase (anorthite) and alteration of this
mineral to sauserite. Alteration of hornblende to chlorite and actinolite
maycontributeto Ca+2,Mg+2and Naf concentrations.
6. Groundwater composition in peissic rocks at Wadi Beitan area has
high concentrations ofMe2, Caf2, Na+ and IC. High concentration of
Mg+2 is referred to the alteration of biotite, while high content of Ca-h2 is
attributed to the dissolution of Ca-plagioclase. High concentrations of
Na* is referred to the alteration ofNa-plagioclase, while high content of
IC- is attributedto the dissolutionofK-feldspar, muscoviteand biotite.
7. Groundwater composition in granitic and syenite rocks at Wadi Madi
and Wadi Amrite area, have very high concenh-ations ofIC +
compared to Mg+2 and Ca+2. A high concentration ofNa+ is referred to
the presence of sodalite and meionite (X-ray investigation) and alteration
ofNa-plagioclase, while high content ofIC is attributed to the dissolution
ofK-feldspar. This is confirmed by the intensive feldspar alteration and
kaolinization, which give a strong chance for IC and M.+ liberation. The
alteration of biotite mineral may contribute in Mg+2 concentrations in
groundwater in granitic rocks, while the alteration of arfvedsonite mineral
may contribute in Na’ and Mgi 2 concentmtionsin syeniterocks. Main conclusions and recommendations:
1- Studying the mobility of elements during alteration processes, which
leads to the concentration increase of some elements in groundwater.
2- Groundwater chemistry of the Quaternary aquifer is directly affected
by rock types forming shedarea and wadi channel.
3- Groundwater quality in Nubian Sandstone aquifer depends mainly on
the depositional environment, which varies from continental to near shore
deltaic.
4- Groundwater chemistry in Basement aquifer is directly affected by the
petrography of water - bearings.
5- from salinity point of view, groundwater in Delta Wadi Hodein can’t
be used under any conditions for human uses, while natural springs at
Abu-Saafa area, EI-Gahlia area, Abu-Beit area and Wadi Madi area can
be used safely.
6- Most groundwater in the area under investigation can be used for
agriculture purposes, by using a developed irrigation systems.
7- Detection of some hydrolysis phenomena (reactions), as a result of
silicate rocks -water interactions and their role in the formation of some
secondary minerals and leaching of some major elements in rocks (e.g.
Na, K, Ca, Mg and Fe).
8- Identification of some secondary minerals that formed due to the
different alteration processes (e g. Kaolinite, Sercite, Chlorite, Sausserite
and Carbonate) and in tum their effects on groundwater quality.
9- Identification of the different rock units nearby water wells through
petrographic investigations as well as field observations.