Chsr&Itristics and Significance of Uranium Bearing Fan African Younger Granite in the Eastern Desert

EG0000327 Tlu?'l--'ri'!i C'unfciTncc on the Peaceful Uses ofAtonm. t^nmsy, uurnascus y - u uec. IVVb AAEA

Chsr&itristics and Significance of Uranium Bearing Fan African Younger Granite in the Eastern Desert, Egypt

M. A, Hassan, G.A. Dabbour and T.F. Mohammden Nuclear .vlntonals Authority, P.O. Box 530, Maadi, ;\;)i!;innya. Cairo. Egypt.

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• L -• ! _^ja_J ui yJt-IiJ 1 J i O_ul Jfcij I a JJ& CjjLJft J_JS a _ -::• t ''I v -^ J ( i T V -^ _i djj " Abstract Surficial uranium mineralization was discoverd in lour Pan African younger granite plutons in the Eastern Desert of Egypt. Tlu: prc^c.it.'t'; revealed great similarity between these plutons both in pcirography a>;.: geochimestry. They are two-feldspar, two-mica pcraluir.i.n.ous ;:r p.i_>.:. which have been formed by melting of crustal materials and cr^nkr•:••.'. .ivir ing the late stage of a late Proterozoic ocogcnic cycle. Radit>rr«•'.:••<..• •••A- chemical investigations indicate that these granites are fertile wv.)\ iv.cr to U and form a potential target for primary uranium deposites. Four x•>•;'. els are suggested to explaine the source and mechanism of the surficia' ;•;•:> nium mineralization in these granites. The most applicable mod'-M •> U:e oxidation of U+4 found in minute dissiminated uraninite grains and its subsequent mobilization. This is supported by petrographic and autoradiographic studies. The bearings of the present study on further exploration for uranium deposits in granites of the Arabian-Nubian shield in general are discussed.

Introduction Surficial uranium mineralization were discovered in four younger Pan- African granite plutons in the Eastern Desert of Egypt (Fig. 1) namely Qat- tar, El Erediya, El Missikat and Um Ara. Secondary uranium minerals mainly uranophane (Fig. 2), occur as dissiminations and fracture filling mostly in association with sheer zones. These four granite plutons show many common features (Mohammaden, 1995)11 j which suggest a common mode of formation of the secondary uranium mineralization. This raised the possibility that these granites could be fertile granites and host primary uranium deposits. Accordingly, comparative petrographic, geochemical and radiometric studies were carried out on 45 representative fresh samples from these granites to identify their common features. The impact of these studies on the understanding of the mode of formation of the associated surficial uranium deposits and the possibilities of the occurrence of primary uranium deposits are discussed.

YAT Fig.'(l): Sketch map showing the studied areas O . . 300Km

• G. Um-Ara *• G. EI-Erediya * G. El-Missikat 0 G. Qattar Precambrian Basement

Common Features of the Uraniferous Granite Geologic Features

Besides their belonging to the younger post orogenic phase of the Pan African cycle, these granites are characterized by wide spread post- intrusion tectonic activities in the form of faults, fractures and shear zones. Multiple post magnetic activity in the form of variable veins and dykes as vvo!l as alkaline plug*-, is also common. Although all studied plutons have no !ar-iprophyn> dykes, yet they have other basic magmatism such as basaltic unc! . dykes as weil as basaltic sheets(Bakhit,1978[2], Abu Dief, 1985 [31, Ibrahim. 1986 j.4] & Roz, 1994 [5])

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\ „•' "••*

Qattar

Figure (2) : Grains of uranophane collected from El-Hrediya ami Q.1 tur granites.

TAt Petrographic Features The petrographic study of 32 representative thin sections from the concerned granites shows that these granites have similar petrograpmc charac- teristics. Felsic minerals (quartz, perthite and sodic plagioclase) have more than one mode of formation with intricate and complicated textural rela- tions between them, which indicate a complex history of crystallization (Mohammaden, 1995) [1] the presence of primary muscovite in the four granites reflects their peraluminous nature which was confirmed by the presence of garnet mineral (Fig. 3) in some of the studied samples. The presence of both muscovite and biotite classifies these granites as two-mica granites. Although the hypidiomorphic granular texture is prevailing, yet mylo- nitic texture (Fig.4) due to post crystallization shearing is not uncommon. The autoradiographic study of some thin sections indicated the presence of some accessory minerals such as zircon (Fig. 5) which seem to have cap- tured their uranium during crystallization. Alpha tracks associated with concentrations of iron oxides and micas (Fig. 6a&b) are mainly due to ad- sorption of uranium on their surfaces. A fine primary opaque mineral occurs ether in the form of dissiminated grains or clusters of grains (Fig. 6a-b & 7a-i) which contribute distinct and high concentrated alpha tracks. It is thus clear that the radioactivity of these granites is contributed both by primary and secondry sources. The principles and procedures of the applied autoradiographic technique are described by Thiel et al. (1979)[6], Figure (3) : Grains of garnet coliected from Urn-Ara. I'.!... X ! 2.

Figure (4) : Mylonitization and annealing ofquarty in qatiar ;uir.niK' L'.P... X 10.

TA1 Figure (5) : Zircon, violet fluorite and iron oxide crystals, Um-Aragranite.

ive (5) : The same previous photomicrograph showing mica flake en- gulfing zircon crystal gire faint pleochroic halo, Um-Ara gran- ge, r p..;x

Figure (5) : Distribution of cc-trckc •esulteJ nun. t!,^, radioactive zircon crystals of the above photomicrograph, Um-Ara granite. P.L., X 35.. Figure (6) : Altered biotite, iron oxide and black iadioacti\e •-< s t low corner, El-Erediya granite. P.L. X 35

Figure (6) : Distribution ot a-trakes or trie ano\e pnotomuio^iuph ml- their scattering in case of altered biotite and iron oxide and their high concentration in case of black radioactive spot . t\L. X35 •V

niV

Figure (7) : Black radioactive mineral of El-Missikat granite, note the red- dish brown alteration around the mineral. P.L. X 35

Figure (7) : Distribution of the a-trakes of the above photomicrograph, P.L. X 35 •» #

Figure (7): Black radioactive spots of Qattar granite.. P.L. X 35

• r

Figure (7) : Distribution of the a-trakes ot the above photomicrograph, P.L. X 35 Geochemical Features The geochemical investigation was carried out on 45 samples from the most fresh parts of the granites. Both major oxides and some trace elements were measured (Table 1). The relatively low loss on ignition values (generally < 1.5) indicates that the sampled units were not subjected to deep meteoric alteration. The obtained data were statistically treated and plotted on standard petrological diagrams (Fig. 8-11). These indicate that these granites are calc-alkaline, peraluminous, S-type granites and that they pos- sibly originated from the partial melting of crustal materials during an orogenic collision stage. These characteristicistics agree with conclusions obtained from the petrographic study.

Radioactivity Uranium and thorium contents of 33 non-mineralized samples, out of the 45 samples which were analyzed chemically, were measured radiomet- rically by g-spectrometric technique. Also, uranium was determined by LA- SER technique. The obtained data are presented in Table 2. All studied granites have high U and Th contents relative to the world averages, but they are low in K content which seems to be a regional characteristic for the Egyptian granites compared to the world granites. This feature is perhaps the only difference from the ideal parameters of fertile granites as suggested by Cambon (1994) [7]. All the measured samples have eU/eTh > 0.4 ex- cept one sample in Urn Ara (Table 2). It is clear that there is a difference between both chemical and radimetric measured uranium, this is attributed to the disequilibrium state in the U-decay series. The same conculsion is obtained from the ratio of eU/Ra which differ than unity. Also, we note that Th/U ratio lower than the world average ratio of granitic rocks ,which equals to 4.5, this reflects a case of uranium addation.

Table (1): Data of complete chemical analysis of Urn-Ara granite

S.NU 1 J .1 1 5 ft 7 K 9 10 11 12 . 13 11 SICJ2 7U.& 12.* 1.1.9 71.01 . 71.1 71.5 72.1 7.1.71 72.8 7.1.SI 74.01 73.31 73.05 74.1 "1102 ans 0.1.1 0.09 0.1 ru 0.07 0.07 0.07 am o.ns 0.04 0.1 II 1)13 0.09 A1.7O.1 1.1.7 14.7 11.7 II) 14. 1 M.I 13.9 3.SJ N.f, n.» IX1I 13.4 14 46 13.5 TclOJ O.lW l.t 1! 1.01 I.I IUC 3.11 o.™ .1 0.9 Wl-I 0.JI 1.1)1 FBI aJS o.s nit 0.71 as 0.5 0.79 0.C] o.» 0.5 0.41 0.1 O.H ns Mirf) (1.02 i 003 0.02 0.(12 n.oi 0.01 0 01 0.02 0.01 0.01 O.tll 0.02 0.02 no] ass i o.j o.x or,} 0.1} 0.33 0.73 0.M 0.33 0.72 0.11 0.57 0JS7 ToT C-»O nm i.r 1.01 u 1.0 0L»! 1.1 O.»» 1.1 an, O.HJ 0.91 0.93 0.9

K2O 1.61 4.1 1.3 1.3 T5— TiT- -1.C7 4.2 1.7 4.72 -4lT~ -1.S6 4.7 0.12 0.15 0.11 O.t* 0.12 0.11 0.1 S O.H 0.A9 0.01 0.04 0.11 on 1-0.1. 1.03 0.9« 0.9K 0.1 5 0.35 0.12 uc 0.IS O.W 0 93 IJ» 1.0! a.n 0.97

ltd las 30 64 !) 31 Cii * 17 20 13 IS 22 n tfi 71 27 71 26 • 27 49

MjO_

NalO raoa O.Oi O.IH 0.01

Table (1): Continue El-missikat granite

ZS 1 29 30 31 32 33 34 35 36 SIO2 73.9 73.1 73.5 7131 73.SI 74 1 73.6 73 9 11.61 TICS 0.08 0.03 0.07 0.13 0.05 O.OS 0.13 0.1 1.12 AL2O3 135 13.1 13.9 13.9 13.91 13.4 13.17 13.S 14.46 FsJO3 1.2 1.45 U !.« 1.7 0.0* 0.84 1 1.00 | 1.04 fEO 0.35 0.62 0J6 0.93 0.68 0.31 0.49 0.* 0.97 MnO 0.05 0.04 0.02 0.03 0.02 0.02 0.03 0.02 0.02 «sP 0.34 0.3' O.« o.n 0.22 0.37 0.31 0.31 O.Ji c»o 1.1 0.9 1.12 o.s 0.95 1.00 0.91 0.92 1.07 h'CO 3.5 3.9 •1.0 3.4 3.6 3.4 0,7) I 3J9 3.11 X2O 4.1 4.0 4.0 3.3 4.16 4.32 1 4.S *.7 nos 0.15 o.os O.OS 0.03 0.03 0.13 0.11 O.I 0.14 LOX o.n 0.9! 3 S3 0.K L.tl 0.97 1.14 0.92 0.83

104 102 92 163 78 78 97 11 113 Sr 143 112 59 108 90 10 <9 71 63 Zr 210 204 130 195 101 161 207 IS8 220 3t 330 3OS ill 303 $tt 333 339 ]70 371 Nb 16 30 22 40 10 27 n 33 39 Y 30 31 23 J4 13 38 3S 2S 47 Cu 9 16 11 21 14 29 21 13 16 li 70 43 *l 66 » 39 33 V 21 fb «4 3! 17 18 11 JO 28 23

Table (1): continue Qattar granite

ISO.' 37 38 39 40 41 42 43 44 *J S1O2 73.9 72J 74.S 713 74.3 73.01 73.7 74.4 71.66 TOM 0.08 0.07 0.09 0.03 0.09 0.09 0.05 0.1 0.14 AL2O3 13.4 (4.3 13.2 14.6 13.01 [4.44 14.4 13.00 14.7 F.2O3 1.2 3.01 0.S3 3.49 .0.96 1.03 0.99 0.S7 0.9 rco 0.43 0.71 0.37 a.6t 0.62 0.7* 0.7 0.42 0.7J MIIO O.04 0.03 0.02 0.03 0.03 0.01 0.02 0.01 0.03 M«O 0.44 0.7S 0.34 0.71 0.33 0.44 0.3 0J1 0.3 CiO 1.0 0.9 1.01 0.93 .1.01 1.13 0.9S 0.73 1.01 XiIO 3.6 3.02 3.33 3.11 3.31 3.14 3J 3.59 1 3.3 K2O 4.5 3.19 4.3 4.01 4.9 4.22 4.4 4.91 4.77 KO5 0.19 O.tl O.U 0.13 0.13 0.17 O.JI 0.05 O.I LO.L 1.0 1.1 0.63 0.85 0.70 0.86 0.68 0.5 [.12

76 106 90 103 73 107 140 100 17 Sr 30-> 147 9 133 203 59 51 TZ 31 Z, 113 103 186 2U_ r.2 239 230 ISO IM Si 705 317 393 317 695 406 269 Z~6 iSO M> 11 37 20 24 12 60 52 3-i V 14 31 24 23 14 40 33 66 ;•* Cu 6 IS 13 25 13 | 19 21 2; 2n 51 SO 33 53 26 61 n 15 Pb it 64 23 S3 31 19 li ;? ig I g ); Log £22 . SiOj diagram oi trie studied granilcs lielO I >s t 1dhiffilrf'*ld n '5 lh* calc alhQlin* tieid and fitd ni 3 th

Fig! ') )-A!,Oj/(f tiO-Na?!-K?O)-f iC; riiocjrcm (Shand, 1957). Cl (Mote--/. ) ^3 CMOlCV.) CQO (MQIT-/. > i" fO* MqO Table (2) : U chemical, eU, eTh, Ra and K% contents as well as ratios of eTh/eU, eU, eU/K, eU/eTh and eU/Ra

S. No Area V eU eTh Ra' K% eTh/eU eUTK eU/eTh eU/Ra chemical AI 64.0 40.3 40.5 30.1 3.1 1.0 130 1.0 1.3 A2 11.4 9.4 25.4 7.3 1.4 2.7 6.7 0.4 1.3 A3 1 130 307.1 66.2 164.9 19 0.2 105.9 4.6 1.9 A4 r- 16.0 12.0 37.0 13.8 2.6 3.1 4.6 0.3 0.9 A5 3 40.0 14.6 26.2 9.3 3.6 1.8 4.1 0.6 1.6 A6 • 80.0 55.9 48.3 63.3 0.8 0.9 69.9 1.1 0.9 A7 ' 120 80.8 42.8 75.9 0.8 0.5 101.0 1.9 I.I A8 192 266.0 52.0 180.0 2.8 0.2 95.0 5 1 1.5 A9 80.0 43.0 49.0 37.0 2.8 1.1 15.4 0.9 1.2 AIO 18.4 13.1 13.6 11.2 1.7 1.0 7.7 1.0 1.2

Average 75.2 84.2 40.2 59.3 2.3 1.3 42.3 1.7 1.3

S. No Area u eU eTh Ra K% eTh/eU eU/K eU/eTh U/Ra chemical El 27.6 18.8 20.3 13.5 3.3 1.1 5.7 0.9 1.4 E2 14.1 11.8 21.6 9.4 3.0 1.8 3.9 0.5 1.3 E3 18.4 U.O 18.0 13.0 2.9 1.6 3.8 0.6 0.8 E4 mi 46.3 24.7 21.6 14.6 2.7 0.9 9.1 1.1 1.7 E5 36.0 17.0 25.7 11.9 4.5 1.5 3.8 0.7 1.4 E6 nm 114.2 131.1 21.6 96.3 1.25 0.2 104.9 6.1 1.4 E7 D- 136 145.0 24.4 101.0 0.82 0.2 176.8 5.9 1.4 E8 *•< 10.0 17.7 14.1 10.0 3.16 0.8 5.6 1.3 1.8 fu Average 56.6 47.1 20.9 33.7 2.7 1.0 39.2 2.1 1.4

S. No Area U eU eTh Ra K% eTh/eU eU/K eU/eTh U/Tv. chemical Ml 80.0 30.4 6.4 .24.5 1.6 ' 0.2 19.0 4.8 1.2 M2 26.0 17.8 34.3 13.7 1.8 1.9 9.9 0.5 1.3 M3 tn 112 85.7 34.2 75.9 1.1 0.4 77.9 2.5 1.1 M4 i 11.4 9.8 16.1 11.6 2.6 1.6 3.8 0.6 0.8 M5 20.0 19.4 35.8 14.6 2.9 1.8 6.7 0.5 1.3 MG 17.1 27.0 38.4 29.8 0.2 1.4 135.0 0.7 0.9 M7 22.8 182 20.6 14.5 2.4 1.1 7.6 0.9 1.3 MS 106.6 44.1 44.0 29.0 0.4 1.0 110.3 1.0 1.5

Average 49 5 31.5 28.7 26.7 1.6 1.2 . 46.3 1.4 1.2

S. No Area U el! eTh Ra K% eTh/eU eU/K eU/eTh U/Ra chemical Gl 112.0 60.7 21.1 41.3 2.2 0.3 27.6 2.9 1.5 G2 800 52.2 48.2 47.1 1.8 0.9 29.0 I.I 1.1 G3 11.4 22.0 21.0 7.0 1.7 0.95 12.9 1.0 3.1 G4 o 128.0 197.0 37.0 151.0 2.3 0.2 85.7 5.3 1.3 G5 220.0 210.0 38.0 155.0 2.8 0.2 75.0 5.5 1.4 G6 17.1 15.0 20.0 5.0 3.2 1.3 4.7 0.8 3.0 G7 h 52.4 44.9 40 3 39.5 1.8 0.9 24.9 I.I 1.1

Average 88.7 86 0 32.2 63.7 2.3 0.7 37.1 2.5 IS

Characteristicistics of Fertile Granite Cambon (1994)[7] discussed the favorable environment for uranium deposits in granitic rocks and suggested the following items in the case of peraluminous granites: - Association with two-mica granite with significant muscovite and albite. - High eij. e'l'h and K values. - eU/ei ii > 0.4. - Post intrusion tectonic activity with formation of various dykes and veins. • A thermal flux more or less contemperancous with the tectonic activity vvhich may be indicated by: a. Long re.giotiai r-i'uamoiphic history with irmltiple successive intrusions. b. Basic i!i;;gmaiic activity manifested by lamprophyric dykes or other basic dykes. - Loss on ignition (L.O.L) in the chemical analyses < 1.5. These represent the most favorable conditions for formation of primary uranium deposits in granitic rocks. Most of these parameters were recog- nized in the studied granites and hence it is possible to consider them as potential target for primary uranium deposits. Similar granitic intrusions should receive particular attention during further exploration programs in w.c hgyptian Shield.

Origin of the Secondary Uranium Enrichment The surficial U mineralization associated with granites in the above mentioned areas can have one or more of the following possible sources: 1- Leaching of labile uranium bound to the intergranular spaces in the rock forming minerals. '•' Leaching of U fixed in some accessory minerals. v- Oxidation and mobilization of U in some primary uranium minerals. 4- !J brought by hydrothermal activity. in (lie following sections we will examine each of these possibilities in the light of ilie obtained and previously available data on. Leaching of Labile Uranium in Granitic Rocks Labile uranium in granitic rocks has been proposed by Stuckless and Ferreira (1976) [ 12s a source for many secondary uranium deposits such as the vein-type uranium deposits in France and the supergene deposits of Yeelirrie, Australia. The immobilization of U at labile sites could take place readily either under the action of an effective transporting medium such as meteoric water which becomes slightly acidified through dissolving of CO? to form weak LLCOT acid, or by the action of hydrothermal solutions moving along channels. The same authors suggested the following charac- teristics for ihe uranitic rocks which contain labile uranium: Alkalic affinity with high silica content (S1O2 > 70%). Anomalously high Th-content (50 ppm or more) relative to the world wide average of granites (18 ppm). This high Th-content is observed even in samples that have lost much or all of their labile U. Radioactive disequilibrium between pairs of long lived radiogenic daughters within the 2-^U decay series. However, .we can preclude the labile U as a source for secondary U enrichment in the studied granites due to the following: The studied granites have peraluminous calk-alkaline nature rather than alkaline affinity. Most of the samples have Th-content less than 50 ppm (Tab. 2). The low Th/U ratios and high U/K ratios, compared to world average which are 4.5 & 1.13 respectively, indicate that the studied granites have not been affected by any process that preferentially removes U from a large volume of rock and concentrates it in economic deposits (Stuckless et al., 1984) [13]. The studied peraluminous granites contain about twice the zirconium saturation limit assigned by Watson (1979) [14], which is < 100 ppm, for peraluminous granite. This excess in zirconium causes U fixation in zircon mineral and its absence in the form of labile U (Tab. 1). Comparison of U-Th-K ternary diagrams plotted for the granites of the Granite Mountain Wyoming, USA (Fig. 12a), which lost 80% of their labile U; and the peraluminous granites in the northwestern Saudi Arabia (Fig. 12b), which lack labile U and did not loose its U fixed in accessory minerals (Stuckless et al. 1984)[ 13]; and the studied Egyptian granites (Fig 12c, d, e, 0 indicates closer similarity between the studied granites of Egypt and the peraluminous granites of Saudi Arabia in the sense that both lack samples with Th/U ratios higher than 4.73, and that the samples are far to some extent from the Th-apex. -In contrast, the studied samples from Egypt have lower Th/K ratios (< 5xtO~4) and lie toward the U-apex with low Th/U ratios that average 1.25, 1.01, 1.2 and 0.68 for Urn Ara, El Erediya, El Missi- kat and Qattar respectively. 12VVJ-Th-K ternary diag'Om :ta>25O0 samples ot granite Mountain U5.A.,lb) 176 samples o' West Saudia Arabia,Ie.d.e and f ) samples ol £l-Eredtya. El-Missikac, Urn. Ara and Qcttar respedivel)<5luckte3s, el al,1584).

Leaching of Uranium Found in the Accessory Minerals Both Th+4 and LJ+4 may be bound in primary accessory phases such as: zircon, sphene and apatite with high concentration as in the case of Lenister granite where zircon and sphene contain > 500 ppm U and apatite has 80- 120 ppm U (O'Connor et al., 1982) [15j. When these primary accessory minerals suffer crushing due to tectonic effects or metarnictization, the in- teraction occurs between these primary accessories and the deep circulating meteoric water or hydrothermal fluids during the deuteric phase. The U+4 of these accessories is then released and oxidized to U+6 ions which are leached out and then subsequently redeposited in surface low-temperature shear zones in the form of secondary uranium deposits (Simpson et al., 1979) [16]. This model may also be preclude due to: Crystals of accessory minerals in the studied granites (some zircon, sphene, apatite, ...etc.) are very fresh without any signs of metamictization even in the mylonitized samples of the studied granites. From autoradiograph studies, zircon still keeps its uranium content, which is also indicated by their strong pleochroic halos when present in mica. On the other hand, sphene and apatite do not give any recognizable pleochroic halos, which indicate that their non radioactive nature is original and not due to removal of their uranium. The experimental leaching of uranium from zircon separated from similar granitic rocks was found negligible even by strong acids.

Oxidation and leaching of U+4 found in the primary uranium minerals Primary uranium minerals such as uraninite and pitchblende may be a source for uranium enrichment and formation of secondary U deposits. These primary minerals contain uranium in the form of tetravalent state which is immobile and stable under the reducing environment. Under oxi- dizing conditions, it will be converted to U+6 which is stable in the oxidiz- ing medium and easily mobile with any circulating fluids. These fluids carry other cations and anions; then under optimum conditions of concentration, temperature, Eh and pH, secondary uranium minerals may precipitate onto shear zones and fractures. This model is reasonable for the U mineralization in the studied granites in the light of the presence of high concentrations of dissiminated black spots (pitchblend, uraninite ?) or fine grains that contribute significantly to the uranium. The very low average Th/U ratio in the studied uraniferous granites favors the formation of uraninite in the assemblage (Qz, uranothor- ite, zircon,, uraninite) since the amount of U exceeds the limit of ThSiCXj USiO4 solid solution (Mumpton an Roy, 1961)[17] in contrast to granitoids with high Th/U in which uranium can be entirely incorporated in a uranoan thorite and the assemblage Qz + uranoan thorite + zircon only is formed. The petrographic study and the autoradiograph investigation for the concerned granits show that there are high concentrations and densities of (-tracks emitted from black spots and fine grains which reflect the presence of true uranium minerals. So, it is very possible to consider them as pitchblend (altered uraninite) or primary uranium minerals which may prevail below the water table where reducing environment dominate. From the above discussion, it is very reasonable to suggest that uraninite and probably other primary uranium minerals are the source of the surficial uranium deposits.

From the hydrothermal solutions According to this model, the original uranium is of epigenetic origin while the 3-previous models mean a syngenetic origin of the uranium from which the secondary uranium enrichment in the studied granites was de- rived. The restriction of the secondary uranium deposits to the shear zones and its association with hydrothermal alteration features may suggest direct formation of the secondary uranium minerals from hydrothermal activities in site without much mobilization. This model was tempting for many authors to explain the origin of uranium mineralization in general as of hydrothermal origin which was later oxidized near surface. However, it was found later that the secondary uranium mineralization is much widespread and not restricted only in shear zones. Also, it occurs in slightly tectonized granite in Um Ara and in Qattar. So, the hydrothermal model could be accepted for the local uranium mineralization in the studied areas near the shear zones, but it is not accepted for the wide spread surficial enrichment of secondary uranium deposits.

Conclusion The granitic plutons of Qattar, El Missikat, El Erediya and Um Ara areas were exposed for petrographic, geochemical and radiometric studies to reach some conclusions about their U fertility and their possible origin of their secondary uranium deposits. Also, to try to direct an exploration pro- gram for uranium. The following conclusions were obtained: - These granites carry approximately all the characteristicistics which make them preferable environment for uranium deposition i.e. fertile granites. - The most reasonable origin of the present secondary uranium enrichment is oxidation and mobilization of U+4 from pre-existing primary radioactive minerals such as uraninite with possible and limited shar- ing from hydrothermal activity . - The scarcity or absence of primary radioactive minerals in the studied samples may be attributed to collection of these samples from the oxidation zone, where the primary minerals were oxidized to secondary ones. - The obtained results suggest the possibility of the presence of economic and primary uranium deposits in the reducing medium i.e. below water table. References [I] Mohammaden, T. F., 1995: Correlative studies on some uraniferous radioactive granitic rocks in Qattar, El Missikat, El Erediya and Um Ara areas, Eastern Desert, Egypt. M. Sc. Thesis, Ain Shams University, Egypt. [2| Bakhit, F. S., 1978: Geology and radioactive mineralization of Gebel El Missikat area, Eastern Desert. Ph. D. Thesis, Ain Shams University, Cairo. 289p. [3] Abu Dief, A., 1985: Geology of uranium mineralization in El-Missikat, Qena-Safaga road, Eastern Desert, Egypt. M. Sc. Thesis, Al-Azhar Univ., Cairo. 103 p. [4] Ibrahim, M. E., 1986: Geologic and radiometric studies on Um-Ara granite pluton, south east Aswan, Egypt. M. Sc. Thesis, Mansoura univ., Egypt. 177p. [5J Roz, M. E., 1994: Geology and uranium mineralization of Gebel Qattar area, northern Eastern Dedsert, Egypt. M. Sc. Thesis, Al Azhar Univer- sity, Egypt. [6] Thiel, K., Sagger, R. and Muff, R., 1980: Distribution of uranium in early Precambrian gold-bearing conglomerates of the Kaapvaal craton South Africa, review of a case study for the application of fission track micromapping of uranium minerals Science and Engineering, Vol. 4, p. 225-244. [7] Cambon, A. R., 1994: Uranium deposits in granitic rock. Notes on the national training course on uranium geology and exploration. Orga- nized by IAEA and NMA, 8-20 Jan. 1994. [8] Brown, G. C, 1982: Calc-Alkaline intrusive rocks: their diversity, evolution and relation to volcanic arcs. In: Andesites (Edited by Thorpe, R.S.), p. 437-461. John Wiley, New York. |9] Shand, S., 1957: The eruptive rocks. John Wiley, New York. [10] Takahashi, M., Aramaki, S. and Ishihara, S., 1981: Magnetite-series/ ilmenite-series vs. I-type granitoids. Mining Geol.Spec.Issue., No.8, p. 13-28. [II] Batchelor, R. A., and Bowden, P., 1985: Petrogenesis of granitoid rock series using multi-cationic parameters. Chem.. Geol., p.43-55. [12] Stuckless, J. S. and Ferreira, C. P., 1976: Labile uranium in granitic rocks. Int. Atomic Energy Agency, Vienna, p. 208-217.

r.i [13] Stuckless, J. S., Nkomo, I. T., Wenner, D. B. and Van Trump, G., 1984: Geochemistry and uranium favourability of the postorogenic granites of the north-eastern Arabian Shield, Kingdom of Saudi Arabia. Bull. Fac. Earth Sci., King Abdel Aziz Univ.-, No. 6, p. 195-209. [14] Watson, E. B., 1979: Zircon saturation in felsic liquids. Experimental results and applications to trace element geochemistry. Contrib. Miner- al Petrol. 70, p. 407-419. [15] OiConnor. P. J., Hennessy, J., Bruck, P. M. and Williams, C. T., 1982: Abundance distribution of uranium and thorium in the northern units of the Leinster granite, Ireland, Geol. Mag., 119 (6), p. 581-592. [16] Simpson, P. R., Brown, G. C, Plant, J. and Ostle, D., 1979: Uranium mineralization and granite magmatism in the British Isles. Phil. Trans. R. Soc. London, A. 291, p.385-412. [17] Mumpton, F. A. and Roy, R., 1961: Hydrothermal stability studies of the zircon-thorite group: Geochem. et Cosmochim. Acta, V. 21, p. 217- 238.

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