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Pergamon Jourml of African firrh Srrences. Vol 17, No 3, pp XT-397. lOY3
Copyright 0 1994 Elsev~cr Saence Ltd
Pnnted tn (ireat Hntam. All nghts recervsd OH9’)-5362/9? $6 IKI + 0 00
Sedimentological, mineralogical and geochemical studies on some Recent Khors sediments, Lake Nasser, Egypt
EZAT A. AHMED, M. EL-DARDIR* and N. N. GINDY*
Geology Department, Faculty of Science, Assiut University, Assiut, Egypt
*National Instrtute of Oceanography and Fisheries, Academy of Scientrfic Research and Technology, Egypt
(First received 22nd July. 1992; revised version received 4th September, 1993)
Abstract - Smty-SIX bottom samples were collected from Khor El-Ran&, Khor Kalabsha, Khor Wadi-Abyad and Khor Allaqi of Lake Nasser. Vanations in their grain-size parameters are attributed to the characteristics of the surroundmg Precambrian basement rocks and Upper Cretaceous Nubia Sandstone
The quartz surface texture reflects fiigerprmts of the original aeolian envuonment of some grams m spite of the diagenesis effect.
The heavy mineral suite illustrates the prime control of provenance
The clay fracuon is composed mamly of kaolmite and smectite Illite occurs UI traceable amounts Then distribuuons suggest a detrnal origin.
Geochemlcal analysis of the clay fraction for SrO,. AlrOr, Fe,O,. CaO. MgO, K,O, Ni, Cu. Pb and Mn content was carried out
INTRODUCTION
In the present study, we present the sedimen- tological. mineralogical and geochemical charac- teristics of Khors sediments of Lake Nasser. Al- though many studies have been carried out on the Lake sediments itself (Entz. 1974, 1976 and 1980; Abu El-Haggag. 1977; Philip et al.. 1977: Hassan et al. 1977; Scot et aL, 1978; Sherif et aL, 1978. 1980 and 1981; Elewa et aL, 1984; Sadiek. 1987; El-Dardi et al.. 1988; Khalifa et al., 1988: Soliman et aL. 1988; Nour El-Din, 1990; Gindy. 1991 and others), very few studies of the Khors sediments are available.
GEOLOGICAL BACKGROUND
Lake Nasser is bordered from East and West by a rugged plain consisting of Upper Cretaceous Nubia Sandstone (Figs 1 and 2). Depositional history of the Nubia Sandstone (Russeger. 1837; Youssef. 1957) has puzzled the geologists for a long time. Many authors suggested an aeolian origin (Fourtau, 1902; Barthoux, 1922, Picard. 1943 in Said, 1962: Issawi. 1971; Kholief. 1982) while others (Klitzsch et al.. 1979; Van Houten and Bhattacharyya. 1979; Ward and McDonald, 1979; Ahmed, 1983 and Soliman et al., 19861 advocated a fluvial origin.
Precambrian basement rock are locally exposed. These consist mainly of Aswan granites, epidio- rites, gneisses. schists, syenites. diorites and aegi- rine trachyte (El-Ramly. 1973).
Ahmed and Soliman (1981) studied the heavy minerals of the Nubia Sandstone m the Eastern Desert and reported that the Nubia sandstone was originally derived from plutomc rocks and might not be due to recycled sedimentation.
MATERIAL AND METHODS
Sixty-six bottom sediment samples were col- lected using grab sampler and research boat from depths ranging between 3 and 45 m below the lake water level from Khor El-Ramla, Khor Kalabsha, Khor Wadi Abyad and Khor El-Allaqi (Fig. 3). The samples were mechanically analyzed accord-
ing the Wentworth ( 1922) grade scale as modified by Krumbein (1934) and the grain-size parameters were calculated according to Folk and Ward ( 1957).
The surface texture of quartz grains of 17 representative samples was examined usmg the Scanning Electron Microscope. The heavy fraction of the sand samples (63- 125~)
was separated and quantitatively determined. Epidote index (IEpd)’ pyroxene mdex (IpJ and amphibole index (IAmp,) of Hassan (1976) were cal- culated.
To examine the local variability of the heavy minerals induced by sedimentary processes, the heavy mineral ratios (E/PHT. N/NO and ZTR/PH) of Flores and Schideler (19781 were calculated on the average heavy mmeral content of the studied samples.
383
384 E72~T A. AHMED, M. EL-DARDIR and N. N. GINDY
The clay fraction (< 2lJ) of 15 samples represent- ing the Khor sed iments were also investigated us ing X-ray diffraction technique, to identify the encounte red clay minerals .
3~ o¢ , 3 ~ l 3°~ I ' r i , r
:~o o 0 0 0
0 O,
SIO=. A1303, Fe203, CaO, MgO. K~O, Ni, Cu, Pb and Mn content of the clay fraction were es t imated gravimetrically by Perkln-Elmer Atomic Absorp- tion spec t rophotometer and Flame photometer techniques.
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Dakhla Formation I Khor Ei-Ramla
II Khor Kalabsha
Nubia Sandstone III Khor Wadi-Abyad
IV Khor EI-Allaqi
Precambrian basement rocks
Fig. I. Geologlcal map of Lake Nasser and |ts surrounding, southern Egypt. {After Issawl, 1968, 1971; EI-Shazly et al., 1977; Klitzsch et aL, 1979 and Ahmed, 1988).
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Sedimentologncal, mineralogical and geochemical studies on some Recent Khors sediments, Lake Nasser ... 387
RESULTS AND DISCUSSION be tween -0.21 (negatively skewed) and 0.63 (very
Grain-s ize
Grain-slze ana lys i s (Fig. 4) reveals tha t the s tud ied s amp le s are main ly s a n d s (90%) bes ide silty s a n d s (10%).
Table 1 s h o w s the va lues of the grain-size para- m e t e r s ca lcu la ted after Folk and Ward (1957). The Khor s amp le s show tha t their m e a n grain-size d iamete rs are f rom 0.65 to 2.670; inclusive graphic s t a n d a r d deviat ion (o i) va lues range be twee n 0 .65 (medium sorted) and 2.67 o (very poorly sorted) inc lus ive g raph ic s k e w n e s s (Sk~) v a l u e s range
positively skewed) with an average va lue of a b o u t 0 .14 (positively skewed); and the graphic Kurtos is (KG) va lues in the s tud ied s amp l e s f rom 0.41 (platykurtic) to 0 73 (very leptokurt ic) with an average reaching 0 .54 (leptokurtic) The average KG values increase towards the nor th High average va lues of Mz, Sk~ and KG are recorded in Khor EI- Ramla sed iments . The average of ~I va lues is relatively high in Khor Wadi-Abyad sed imen t s relative to the o ther s tud ied khors . The va lues of Mz, ~, SK i and KG do not va ry with wa te r dep th in the s tud ied khors (Table 2 and Fig. 5).
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Fig. 4. Classification of the analyzed Khor samples following Shepard (1954)
388 EZZAT A. ~ D , M. EL-DARDIR and N. N. GINDY
Table 1. P e r c e n t a g e s of s a n d , silt a n d c lay of t he a n a l y z e d K h o r s s a m p l e s .
L o c a t i o n K h o r E I - R a m l a Sample no. Depth (m) Sand % Silt % Clay %
1 3 67.5 29.4 3. I 2 3 84.0 13.5 2.5 3 5 86.9 12.4 0.7
4 6 94.6 4.9 0.5 5 12 92.3 6.0 1.7 6 8 96.3 3.5 0.2 7 15 85.6 13.3 1.1 8 11 82.2 12.8 5.0 9 22 91 .o 8.5 0.5
lO 21 95.8 3,5 0.7 11 14 90.3 9.7 12 23 97.2 2.7 0.I 13 33 84.4 12.9 2.7 14 25 97.4 2.3 0.3 15 27 96,8 3.0 0.2 16 28 99.0 I.O
Main C h a n n e l
17 63 99.1 0.9
Khor K a l a b s h a 18 43 91.4 7 2 1.4 19 32 99.4 0.6 20 23 99.1 0.9 21 17 95.0 4.5 0.5 22 31 94.8 4.2 1.0 23 29 98.9 I. I 24 29 91.5 7.0 1.5 25 26 93 o 5.3 1.7 26 19 97.5 I 8 0.7 27 20 89.7 8. i 2.2 28 19 92.5 6.8 0.7 29 17 77.0 20.5 2.5
Main C h a n n e l
30 51 94.2 4.7 1.1
Khor W a d i - A b y a d 31 4 99.2 0.8 - i 32 5 74.5 22.2 3.3 33 16 81.2 15.2 3.6 34 20 83.4 15.7 0 .9 35 25 79.8 18.o 2.2 36 28 90 3 9.0 0.7 37 28 76.0 21.1 2 9 38 38 76.1 20.2 3.7 39 41 81.4 15.7 2.9 40 45 73.2 22.9 3.9
Main C h a n n e l
41 62 89.2 10.0 0 8
K h o r EI-Allaql Sample no. Depth (m) Sand % Silt % Clay %
42 15 91.1 7.3 1.6 43 23 95 3 3.2 1.5 44 27 92.2 5.9 1.9 45 32 96.0 2.9 1.1 46 27 96.5 3 5 47 20 87.2 10.8 2.0 48 13 87 6 10.5 1.9 49 9 87 6 11.9 0.5 50 8 98.8 1 1 51 10 90.1 8.7 1,2 52 14 94.7 4.1 1.2 53 16 92 3 6.2 1,5 54 18 95.0 4.0 1.0 55 20 97.2 2.8 56 20 97 1 2.9 57 17 95 5 3 5 1.0 58 20 82.2 16.7 1.1 59 17 93.6 5.4 1.0 60 17 99. i 0.9 61 16 91.8 6.6 1.6 62 20 91.0 7.2 1.8 63 16 98.9 1 1 64 17 85.0 13.6 1.4 65 16 96.6 2.9 0.5
Main C h a n n e l
66 35 91.3 8.35 0,35
In fact, t h e h y d r o d y n a m i c s of the s t u d i e d k h o r s differ f rom one k h o r to t he o ther . Whi le w a v e s a n d c u r r e n t s are s t r o n g in K h o r E1-Allaqi a n d K h o r K a l a b s h a , s ta t i c h y d r o d y n a m i c c o n d i t i o n s prevai l in K h o r s E1-Ramla a n d W a d i - A b y a d .
Fol lowing P a s s e g a (1957, 1964) a n d P a s s e g a a n d Byramj ee (1969), t he p lo t s of the a n a l y z e d s a m p l e s lie in t he field of rol l ing (67.86%), rol l ing s u s p e n - s ion (10.71%), m o d e r a t e t u r b u l e n c e g r a d e d s u s - p e n s i o n (7 14%) a n d u n i f o r m s u s p e n s i o n r eg imes (1.79%) (Fig. 6).
Q u a rtz s u r f a c e T e x t u r e
T h e s u r f a c e f e a t u r e s of t h e q u a r t z g r a i n s e x a m i n e d s h o w (Fig. 7 )
(1) M e c h a n i c a l f e a t u r e s i n c l u d i n g u p t u r n e d p la tes , m e a n d e r i n g r idges , V - s h a p e d pi ts , c u r v e d g rooves a n d c o n c h o i d a l f r a c t u r e s w h i c h po in t to a n aeo l i an or igin (Coch a n d Krins ley, 1971; Margol is a n d Krinsley, 1974 a n d K r m s l e y a n d Wel lendorf , 1980).
(2) C h e m i c a l f ea tu re s . Sfllca d i s s o l u t i o n a n d p rec ip i t a t i on in t he q u a r t z g r a i n s h a v e b e e n con- s ide red as w e a t h e r i n g p h e n o m e n a u n d e r acidic c o n d i t i o n s ( D o o r n k a m p a n d Krinsley, 1971, Higgs,
Sedimentological, mineralogical and geochemical studies on some Recent Khors sediments, Lake Nasser ... 389
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Fig. 5. Variations of grain size parameters wRh depth of Khor EI-Ramla (a); Khor Kalabsha (b); Khor Wadl Abyad (c) and Khor Ellaql (d).
Sechmentological, mineralogical and geochemical studies on some Recent Khors sediments, Lake Nasser . . .
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mooo 1979). Therefore, the surface f ea tu res of the quar tz grains were mos t p robab ly inher i ted from the source rocks. However, in the case of silica preci- pitation, the d isso lu t ion of d ia tom ske le tons as a source of silica canno t be excluded.
Fig. 6 Plots of the analyzed samples on the C-M dlagram of Passega (1957, 1964) and Passega and Byramjee (1969).
H e a v y m i n e r a l s
Heavy mineral ana lys is of the Khors sed imen t s revealed opaque (53.56%) and non-opaque (46.44%) minerals . The non -opaque minera l s include epido- tes (19.46%), amphibo les (9.90%), zircon (7.50%), p y r o x e n e s (3.26%), t o u r m a l i n e (3 13%), mica {1.67%), garnet (0.44%), rutfle {0.43%), s taurol i te
,oo (0.41%), sp ine l (0 22%) and apa t i t e (0,02%) (Table 3). The a m o u n t s of the individual heavy minera l s varies among the different s tud ied Khors. Khor EI-Ramla sed imen t s dmplay relatively high f requency of epldotes, amphibo les , pyroxenes , tourmal ine and rutile (Table 3). Khor Kab labsha s ed imen t s are relatively enr iched in zircon. Khor Wadi Abyad sed imen t s are enr iched m stauroli te ,
ioooo IChor EI-Allaqi s ed imen t s d isplay relatively high f requency of mica, garnet , spinel and apatite. Epidotes, amphiboles , zircon, pyroxenes , rutlle, s taurol i te and apat i te do not show any regular var ia t ion with wa te r dep th However, the fre- quency of tourmal ine , mica, garne t and spinel de- c reases as the water dep th increases . The heavy
m o o mineral con ten t of the Khors s ed imen t s reflects a relative deficiency m pyroxenes and enr i chment of epidotes and amphibo les compared with the nor- mal Nile sediments . The relative en r i chment of zircon in the s tud ied Khor s ed imen t s as well as the progressive increase of the a m o u n t s of opaques , epidotes, amphibo les and pyroxenes , away from
aoo the main channel , m a y be a t t r ibu ted to local con t r lbu tmn effect from the Nubia S a n d s t o n e tha t wldely dis tr ibuted a round the s tudied khors. Shukr i and Said (1945) po in ted ou t tha t the Nubla Sands tone conta ins a heavy minera l sui te lacking pyroxenes and with var iable b u t small a m o u n t s of amphibo les and epldotes
The indices of epidote (IEr J , amphibole (Ip~_, h) and pyroxene (I~y) were ca lcula ted after H a s s a n (i 976). The resu l t s show that the khor s ed imen t s have higher epldote index (lw. d) and lower amphlbole index (I~_~v h) t han that oi~Hassan (1976), a resul t indicating the un i mpor t an t role of the Nile contri- bu t ion to the khor s ed imen t s
The shape f ract ionat ion index E / P H T expressed by the ratio of ep ldo te / (pyroxene + hornb lende + tourmaline) , the hydraul ic f rac t ionat ion by dens i ty O / N O expressed by the ratio of o p a q u e s / n o n - opaques , and the stabil i ty index ZTR/PH (zircon + t r o u m a h n e + ru t i l e /py roxene + hornblende) were c a l c u l a t e d af ter F lo res and Sh ide l e r (1978). Table 4 i l lustrates tha t there is no significant
392 EZ7_AT A. AHMED, M. EL-DARDIR and N. N. GINDY
(NIL;.
Fig. 7. Scanning electron mlcrographs showing: a - Upturned plates; b - meandenng ridges; c - Mechanical v-shaped pits and grooves; d - Sdlca overgrowth and dlssolution;
e - Silica globules; f - Diatoms plastered on sand grains.
va r ia t ions in t hese hydrau l i c indices among the s tud ied kho r s so the dif ferences in the i r a m o u n t are mos t ly re la ted to the p rovenance effect r a the r t h a n h y d r a u h c f rac t iona t ion
Clay minerals
X-ray diffract ion analys is of the clay f rac t ion of the col lected s a mp l e s revealed t ha t kaol ini te and smect i te are the m a i n clay minera l s e n c o u n t e r e d in all the s tud ied s am p l e s (Fig. 8). Illite occurs in
t raceab le amoun t s . The h ighes t f r equency of kao- linite is recorded mos t ly in a reas far away from the ma in channe l . It is sugges ted tha t the exis tence of kaolini te and smect i te m the s tud led kho r s sedi- m e n t s m a y be due to the local con t r i bu t ion f rom the Nubia S a n d s t o n e The dec rease of kaolini te with increas ing wa te r dep th m a y be a t t r i bu ted to size seggregation control of the clay part ic les (Gibbs, 1977). The occu r r ence ofillit e in t r aceab le a m o u n t s m a y resu l t f rom diagenes is of smect i te (Mt~ller, 1967).
Sedimentologlcal, mineralogical and geochemical studies on some Recent Khors sediments, Lake Nasser ...
Table 3. Relative a b u n d a n c e of heavy mine ra l s in the 63-1251,t size fract ion.
Locatlor Sample Depth i ~ ~ 8 ~ ~ ~ • 0 ~ ": " ~
. . . . o
I
2 3 |8.67 24.97 12.48 5.19 4.16 2.50 1.25 0.23 0.39 10.08 0.08 - 4.45
4 6 50.49 21.47 11.23 6.34 3.75 3.08 1.86 0.59 0.54 0.65 - - 3.34
E 6 8 56.51 28.98 9.67 6.93 3.16 1.79 1.34 0.77 0.48 0.I0 0.29 - 5.55
8 ii 48.19 22.56 LI.56 7.29 3.76 3.29 1.28 1.12 0.33 0.40 0.2.2 - 3.73 J
i0 21 48.25 21.13 10.74 6.64 3.52 4.49 2.89 10.54 0.45 0.72 0.63 4.26
12 23 45.66 ~8.50 9.26 10.37 3.08 10.57 1.78 0.56 0.22 - 4.27 X= 14 25 48.98 19.72 10.12 7.66 3.28 7.15 1.93 0.52 0.64 - ~ 3.IC
16 28 43.29 20.59 10.51 8.65 3,43 8.57 3.06 0.63 0.53 0.32 0.42 ~5.86
>~
o < _c ~ j
Average
18
20
22
24
26
28
Average
32
34
36
38
40
15.63 48.75 20.99 10.70 7.38 3.52 5.18 L.92 0.49 0.48 0.39 0.20 - 4.32
43 60.43 15.73 7.86 7.95 2.62 2.52 1.50 0.32 0.54 0.32 0.21 - 0.60
23 59.34 16.43 8.21 i0.08 2.74 1.36 0.72 D.46 0.39 0.20 0.07 - 3.38
31 50.58 20.74 II0.52 10.99 3.46 2.46 0.45 0.i0 0.25 0.20 0.25 - 4.88
29 59.55 16.87 8.43 7.46 2.81 2.35 1.03 0.40 0.81 0.06 0.23 4.24
19 56.90 19.39 9.70 7.86 3".23 1.60 0.71:0.20 0.24 0.17 - 1.97
19 54.80 20.69110.34 7.14 3.45 1.95 0.43 0.40 0.40 0.35 0.05 4.5[
-&
i
27.33 56.93 18.31 9,18 8.58 3.05 2.04 0.81 0.31 0.44 0.22 0.13 - 3.28
5 52.84 20.55 10.45 6.&0 3.84 2.35 1.81 0.39 0.43 0.60 0.14 - 2.01
20 52.87 21.79 10.90 5.81 3.63 1.23 1.52 0.31 0.46 1.33 0.15 - 2.95
28 60.62 16.68 8.44 7.57 2.78 ..14 1.51 0.33 0.50 0.30 0.]_3 - 1.63
38 60.76 17.64 8.82 5,16 2.94 0.72 1.28 0.39 0.45 .... 45 0.39 - 0.45
45 47.65 21.99 11.00 10.68 3.66 0.84 1.57 0.52 - 2.09 - 0.07
Average 27.20 54.95 19.73 9.92 7.16 3.37 1.26 1.54 0.39 0.37 1.15 0.16 1.42
42 15 62.65,14.67 7.41 7.95 2.44 1.28 1.67 0.54 0.35 0.69 0.23 0.12 5.82
44 27 60.15 17.75 8.98 6,94 2.96 0.81 I.ii 0.55 0.36 0.23 0.16 4.5~
46 27 56.75 20.80 10.44 5.52 3.47 i.ii 1.07 0.23 0.19 - 0.42 - 3.7"~
48 13 55.41 19.93 10.37 6.56 3.32 1.41 1.38 0.61 0.51 0.16 0.29 0.05 5.6(
50 8 66.06 13.02 6.70 5.78 2.17 2.41 2.47 0.37 0.51 0.09 0.42 - 5.4f i
52 14 58.22 16.70 8.14 7.13 2.62 4.34 1.54 0.29 0.62 ~0.II 0.29 - 4.4~
54 18 59.69 15.31 7.82 8.20 2.55 2.98 2.02 0.54 0.49 0.31 0.09 7.91
56 20 53.94 19.]8 9.91, 8.52 3.20 2.72 1.05 0.70 0.32 0.21 0.25 - 2.41
58 20 48.66 22.01 11.33 7.59 3.67 3.33 2.04 0.44 0.41 0.20 0.32 3.9~
60 17 48.65 20.45 10.61 7.81 3.41 4.49 3.19 0.75 0.38 0.07 0.19 4.5!
62 20 36.13 26.88 14.26 6.52 4.48 4.97 4.82 0.47 0.59 0.12 0.47 0.29 6.5
64 17 47.78 20.25 10.65 7.52 3.38 7.37 1.39 0.59 0.45 0.17 0.28 0.17 6.0:
Average 18.0 54.51 18.91 9.72 7.17 3.14 3.10 1.98 0.51 0.43 0.20 0.28 0.05 5.1
393
Table 4. Hydraul ic f rac t iona t ion rat ios of the s tud ied Khors sed iments . G e o c h e m i s t r y
Location Depth E/PHT O/NO ZTR/PE
Khor EI-Ramla 15.63 1.08 0.95 0.92 Khor Kalabsha 27.33 1.28 1.32 0.90 Khor Wadi-Abyad 27.20 1.36 1.21 0.66 Khor EI-Allaqi 18 00 1.16 1 19 0.83
E -- E p i d o t e s , P = P y r o x e n e s ,
T = T o u r m a l i n e O = O p a q u e s ,
Z = Z i r c o n , R = R u t i l e
H = Hornblende, NO = Non-opaques,
The clay f rac t ions of sixty-six s amples represen t - ing the s tud ied kho r s were ana lyzed for the i r SiO 2, AI203, Fe203. CaO, MgO, K20, Ni, Cu, Pb and Mn conten t (Table 5). The resu l t s show t h a t SiO 2, MgO, I~O and Ni are relat ively a b u n d a n t m the clay f rac t ion of Khor EI-Ramla. This was a t t r i bu ted to the relative a b u n d a n c e of smect i te a n d / o r fllite. Pb and Mn are relat ively a b u n d a n t in the clay f ract ion of Khor Kalabsha. The relat ively h igher Pb concen- t ra t ion in this khor is a t t r i bu ted to local pol lut ion
394 EZZAT A. AIIMED, M EL-DARDm and N. N. GINDY
T a b l e 5 R e s u l t s of c h e m i c a l a n a l y s e s .
Location
n3 .-4 _=
I .-4 r,1
o c-
Sample No
i 2 3 4 5 6 7 8 9
I0 ii 12 13 14 15 16
Average
~a in channel 17
~3
o3 c]
hd
o r-
Ld
18 19 20 21 22 23 24 25 26 27 28 29
Ave r aae
Ha]_n c h a n n e l 30
31 ~u 32 n3
" >~ 33 34 35
"~ 36
Depth
(m)
3 3 5 6 12 8
15 ii 22 21 14 23 33 25 27 28
16
63
43 32 23 17 31 29 29 26 !9 20 19 17
2 5 . 4 2
51
4 5
16 20 25 28
Si02 AI203 Fe20 S Ca0 Mg0 K20 Ni Cu
% % % % % % ppm ppm
41.48i26.48 37.33 22.48 39.58 21.20 40.24 22.08 42.73 13.28 36.17 12.96 45.76 18.64 42.00 13.44 45.47~ 17.92 47.33:19.36 32.42 12.24
5.12 4.48 1.12 0.48 28.6 142.6 6.72 3.36 0.80 0.55 20.8 98.6 4,80 2.91 0.80 0.67 11.4 71.2 5.12 3.58q0.80 0.50 14.6 214.0 5.12 3.36i0.48 0.52 41.4 97.2 5.44 4,03!0.32 0.55 45.0 120.4 5.76 3.36 0.64 0.42 36.4 91.2 4.16 3.14 0,64 0.54 39.8 146.8 4.48 2.91 0.48 0.46 38.6 161.6 3.84 2.46 0.48 0.46 40.2 220.4 4.16 2.91 0.32 0.34 35.2 185.0
31.80 21.441 5.76 3.81 0.48 0.46133.8 259.0 29.34 28.881 6.72 3.58 0,32!0.56 50.2 133.0 43.54 21.84 4.16 3.14 0.16 0.38 25.2 193.6 33.40 26.56 5.44 2.91 0.16 0.40 33.8 205.0 48.48 14.24 4.16 2.24 0.16 0.28 29.6 241.6
Pb Mn
ppm ppm
86 487.8 78 448.2
102 455.0 86 448.6 22 4Ol.Od 44 666.01 18 440.41
124 404 .0 '
72 394.4' 142 445.4 106 420.4 102 623.6 60 658.6
200 391.8 212 461.6 130 365.6
39.82 19.57 5.06 3.26 0.51 0.47 32.81 161 3 99 469.5
48.36 14.08 5.12 0.90 0.16 0.34 16.81 201.4 138 401.8
27.75 27.84 35.18 24.40 32.52 24.72 27.24 19.76 24.76 25,92 31.22 29.12 22.30 22.56 31.42 22.64 23.341 24.80 28.341 27.04 25.96 24.161 27.50 25.12!
8.96 1.12 0.32 0.61 41.0 144.4 124 8.00 1.57 0.32 0.58 30.6 170.8 140 6.08 !.79 0.16 0.42 45.8 155.6 102 3.84 2.91 0.32 0.29 18.6 161.2 48 6.08 3.14[ 0.16 0.39 25.0 143.6 70 7.68 1.571 0.16 0.50 9.4 104.2 112 7.04 1.34! 0.16 0.50 16.6 97.6 90 5.76 2.46 0.32 0.37 31.6 114.2 260 4,80 2.9], 0.32 0.321 37.2 161.2 210 7.36 1.79 0.16 0.45 30.6 142.4 284 5.44 1.34 0.161 0.35 17.6 139.8 226 4.48 0.90 0.16 0.31 10.6 155.8 260
841.8 520.6 449.2 473.0 500.8 568.8 625.6 551.8 409 .(] 615.6 521.2 473.4
28.13 24 84 6.29 1.90 0.23 0.42 26.2 140.9 L60.5 545. c ,
30.62 29.12 10.8R 0.45 o.16 0.88 15.0 205.6 )_80.0 987.[
32.96 - 7.36 2.02 0.32 0.35 29.6 134.6 188 778.~ 32.50 22.88 5,12 9.14 0,48 0.291 6.4 122.6 172 679.z 25.66 23.92 4.48 2.69 0.16 0.271 ii 8 134.8 142 446.~ 27.98 24.96 5.44 2.46[ 0.16 0.32 i 7 6 92.6 146 404.~ 27.00 26.00 4.80 1.57 0.00 0.36 7 0 127.4 108 462." 29.80 - 8.00 0.67 0.00 0.39 5 8 140.4 132 739.
Fe20 3 = Total iron
Sedimentolog~cal, mmeraloglcal and geochemical studies on some Recent Khors sediments, Lake Nasser ... 395
/
'c' I
IB I
V
A
ljl A i ] h J , i ,
30 28 26 24 22 20 IB" ,6" t4 12" I0 E3" 6'
2 9
Fig 8. X-ray dlffractogram patterns of sample No 62, Khor El- Allaqi A - Bulk sample., C -Air dry onented Sample. C - Sample
treated wlth ethylene glycol , D - Sample heated to 550°C_ I - Semectate; 2 - llhte, 3 - kaohmte
C O N C L U S I O N S
Sedlmentologlca l and minera logica l s tud ies of the Recent kho r s ed imen t s along lake Nasser re- vealed that .
- Grain-s ize ana lys is of the s tud ied kho r sedi- m e n t s show tha t they are composed main ly of s and (90%) and silty s a n d s (10%). The grain-size para- m e t e r s are widely var ied f rom one kho r to the other . These var ia t ions are a t t r i bu ted to the effect of local source rocks.
- Scann ing Elec t ron Microscope invest igat ion of qua r t z gra ins m the Khor s ed imen t s indica tes the p resence of mechan ica l ( u p t u r n e d plates , meande - ring ridges, V-shaped pits, curved grooves and concholda l f ractures) and chemica l (precipi tat ion and dissolution) f ea tu res These point to the i r aeol ian origin and the effect f rom the previous deposlt10nal env i ronmen t of the Nubia Sands tone .
- Heavy minera l invest igat ion of the s tud ied kho r s ed imen t s reflect a def ic iency in py roxenes and e n r i c h m e n t of ep idotes and amph ibo le s relatlve to the normal Nile sed iments . This conf i rm the im- po r t an t role of local con t r i bu t ion from s u r r o u n d i n g c o u n t r y rocks Moreover, the p re sen t s t udy shows tha t the hydrau l ic f rac t iona t ion by shape , dens i ty and chemica l decompos i t ion of the heavy minera l s is insignificant.
- X-ray diffract ion ana lys i s of the clay minera l s in the khor s ed imen t s shows the p re sence of kaoli- nite, smect l te and t r aces of flhte
Geochemica l ana lys is (major and t race ele- ments) of the clay f rac t ion (< 2~) shows tha t the behav iour ofS102. AI20 a, Fe203, CaO, MgO, K20, Ni, Cu, Pb and Mn are control led by the relative abun- dance of the clay mine ra l s In the s tud ied samples , pol lut ion of f ishing boa t s in the lake, f resh wate r ca l ca reous form and the source rocks.
due to the p r e sence of f lshlng boa t s a n d / o r its adso rp t ion to iron oxides, The relatively high Mn concent ra t10n m a y be asc r ibed to the effect of local con t r i bu t ion f rom the b a s e m e n t rocks• AI20 a is relat ively a b u n d a n t in Khor Wadi Abyad samples due to the relat ively high a m o u n t s of kaol imte CaO and Cu are relat ively a b u n d a n t in the clay f ract ion of Khor EI-Allaqi. The a b u n d a n c e of CaO is re la ted to d i s in tegra t ion of f resh wate r ca lca reous fo rams by s t rong waves and cu r r en t s . The high concen t r a - t ion of Cu in all kho r sed iments , in general , and in Khor EI-Allaqi, in par t icu la r , m a y be due to the con t r i bu t ion of the wea t he r ed b a s e m e n t rocks.
No regu la r var ia t ions have been observed in the a m o u n t s of Al20 a, Ni, Cu, Pb and Mn con ten t with wa te r dep th m the different khors . On the cont ra ry , the averages o fFe20 a and K20 increase with depth, whereas , the average con t en t s of SiO 2. CaO and MgO decrease with wa te r dep th
Acknowledgements - The authors thank Prof Dr. Emad R Phllobbos, Dept. of Geology, FacultyofSclence, Assmt Umvermty for hls suggestions and dlscusmons dunng the progress of the work
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