factors controlling the radioactivity of gabal abu edam ... filefactors controlling the...

64 ----------------------------------------------JJoouurrnnaall ooff SSeebbhhaa UUnniivveerrssiittyy--((PPuurree aanndd AApppplliieedd SScciieenncceess))--VVooll..66 NNoo..22 ((22000077)) ----------------------------------------

Factors Controlling The Radioactivity Of Gabal Abu Edam Area,

Eastern Desert, Egypt El Kholy, D.M.M*

Abstract

Gabal Abu Edam area occupies the eastern part of G. Qattar. It is covered by dioritic rocks that overlain by Hammamat sediments. They were intruded by younger granites in sharp intrusive contact. These granitic rocks are biotite hornblende granites and perthite granites. The biotite hornblende granites are intruded by the perthite one in its core to aappear as ring. The biotite – hornblende granite was intruded by acidic dykes while the perthite granites were intruded by acidic and basic ones. It worth to mention that some acidic dykes not pass through the perthite granites. These dykes are trending NE – SW.

Petrographically, the granitoid rocks are ranging from diorite to younger granites. The diorites are formed mainly of plagioclase, hornblende with minor orthoclase and biotite as essential minerals, while the accessories are iron oxides, apatite and sphene. The younger granites are classified into subsolvus biotite - hornblende granites and hypersolvus perthite granites. The zircon, iron oxides, apatite, allanite, xenotime are the main accessories. In the perthite granites the alkali feldspars exceed the quartz content to seem as syenogranite. Thus this arrangement of the granitic rocks from diorite to pertite granite could be considered as ring complex or zoned granite.Structurally, primary and secondary structures are recorded. The primary structures are represented by stratifications and laminations which are well distinct in the Hammamat sediments. The bedding of these sediments are striking NW – SE and dipping in NE direction. The secondary structures are represented by faults and joints. The faults are directed in NNW – SSE, NW – SE, NE – SW and ENE – WSW directions while the joints are trending in NW – SE, ENE – WSW and WNW – ESE directions. These faults and joints acted as passways for the hydrothermal solutions carrying radioactive minerals. Radiometrically, all the exposed rocks are measured in the field. It is found that the lowest radioactive rock is the diorite while the highest radioactive ones are the younger granites. The most radioactive rock among the younger granites is the perthite granite which shows uranium content varying between 13ppm and 21ppm. * Faculty of Science & Arts-Ubari, University of Sebha.

----------------------------------------------------------------------------------- Factors Controlling The Radioactivity Of Gabal Abu Edam

---------------------------------------------- JJoouurrnnaall ooff SSeebbhhaa UUnniivveerrssiittyy--((PPuurree aanndd AApppplliieedd SScciieenncceess))--VVooll..66 NNoo..22 ((22000077)) ---------------------------------------- 65

The radioactive anomalies are recorded along faults and near contact zones of dykes and granite and show average uranium and thorium contents of 600ppm and 500ppm respectively.

The factors controlling the radioactivity are the lithology, grain size, mineralogy, hydrothermal alterations and structural features.

INTRODUCTION The igneous rocks in northeast

Africa produced at the end of Precambrian tectonothermal event are termed as Pan African ( kennedy, 1964). The final stages of cratonization of the Pan African event were characterized by calc – alkaline to peralkaline magmatism (Gass,1981). Alkali or A –type granites (Loiselle and Wones (1979)) have received much attention because of their economic potential and tectonic significance. A – type granites are formed in anorogenic within plate situation. Hassan and Hashad (1990) assigned an interval of time from 570 to 530 Ma, tentatively called the Katherina event, during which peralkaline granite and alkali feldspar granites

and their extrusive equivalents are the dominant granitic types in the northern part of the Nubian Shield.

The present area is located east Gabal (G.) Qattar and bounded by latitudes 27º 00 ۤ 00ً and 27º 8 ۤ 00ً N and longitudes 33º 24 ۤ 00ً and 33º 36ۤ 00ً east (Fig. 1).

The study area is covered by diorites, Hammamat sediments and younger granites. These rocks are dissected by post granitic dykes comprising acidic, intermediate and basic ones.

The rocks covering the study area are studied by many authers. Among them El shazly (1964), El Ramly (1972), Sabet (1972), Dardir and Abu Zeid (1972), El Bouseily and Sokkary (1975). El Gaby (1975), Akaad and Noweir (1980), Greenberg (1981), Hussein et al (1982), Attawiya (1989), El Gaby et al (1990), Noweir et al (1990), Rogers and Greenberg (1990), Salman et al (1990), Khalaf (1995), Abdel AAl, (1996), Nossair and Ahmed (1999), Mussa (2001) and Haridy (2002).

The aim of the present study is to determine the factors which control the high radioactivity distribution in the different rock units of G. Abu Edam area, especially the younger granites.

El Kholy, D.M.M ---------------------------------------------------------------------------------------------------------------------------------

66 ---------------------------------------------- JJoouurrnnaall ooff SSeebbhhaa UUnniivveerrssiittyy--((PPuurree aanndd AApppplliieedd SScciieenncceess))--VVooll..66 NNoo..22 ((22000077)) ----------------------------------------

METHOD OF STUDY The study of the different rocks

covering G. Abu Edam area was achieved by the following steps 1- Aerial photographs were prepared for drawing the base map. 2- Describing the different rocks in the area and determining their field relationships. 3- The structural features are recorded and measured during the field work. 4- The recorded structural measurements are treated statistically and diagrammatically to determine the main stress affecting the area.

5- Collection of samples is carried out for petrographic study and radiometric analysis. 6- The collected samples are radio metrically analyzed in Nuclear Materials Authority, Egypt. 7- Determining the factors controlling the recorded high radioactive anomalies during the field work. Also, through X-Ray analysis of some radioactive samples to determine the pathfinder elements that usually associate with high radioactivity.

GEOLOGICAL SETTING

The study area is covered by the following rocks that arranged chronologically: Post granitic dykes………Youngest Younger granites Hammamat sediments Diorites…………………..Oldest Each of the above mentioned rocks will be treated in the following lines. Diorites

The dioritic rocks are exposed in the north western sector of the study area. They are strongly weathered and altered. These rocks are unconformably overlain by clastic Hammamat sediments and intruded by younger granites in sharp intrusive contact (Fig.1&2).

Dioritic rocks in the present area are dissected by major strike slip faults that trending NW – SE. In hand specimen, these rocks are grey to greenish grey in color, coarse grained and altered in some parts especially along their contact with the younger granites or along faults. They are enriched in plagioclase, hornblende and some mafic minerals in addition to minor quartz and minor k- feldspars. Rogers and Greenberg, (1990) stated that they are related to the late orogenic granite, while El Shazly (1964) considered these rocks synorogenic and Hussein et al (1982) stated that they are subduction and collision related granites. El Gaby


----------------------------------------------JJoouurrnnaall ooff SSeebbhhaa UUnniivveerrssiittyy--((PPuurree aanndd AApppplliieedd SScciieenncceess))--VVooll..66 NNoo..22 ((22000077)) ---------------------------------------- 67

(1975) stated that the dioritic rocks are synorogenic granitoids.

Microscopically, they are light to dark grey, medium to coarse grained exhibiting equigranular or hypidiomorphic textures.

They are composed of plagioclase (An40 – An44), hornblende, biotite and minor quartz.

The accessory minerals are represented by sphene, iron oxides and apatite while the secondary ones are epidote and chlorite. Hammamat Sediments

The Hammamat sediments in the area are found as low hills in NE and NW sectors of the study area (Fig.1). They are intruded by younger granites in sharp intrusive contact. They show thermal metamorphism along this contact expressed by carbonation, epidotization and hematitization. Conglomerates, greywackes and siltstones are the main rock units forming the Hammamat group. They are characterized by their well distinct stratifications that striking NW – SE and dipping NE. Petrographically, they will be described where the conglomerates are dark green in colour, coarse grained, rounded to subrounded and heterogenous polymictic in their composition. They consist of stretched lithic fragments of older rocks, altered feldspars, quartz

and opaque minerals, all are embedded in fine grained matrix of the same composition.

The greywackes comprise angular to subangular quartz of size range from 1 -2mm in length and 0.5 – 1mm in width, altered euhederal to subhederal plagioclase and anhederal to subhederal orthoclase which is slightly altered to kaoline and sericite. Younger Granites

These rocks are covering most of the study area. They had intruded the older rocks in sharp intrusive contact. Moustafa (2001) stated that the younger granites in the study area are three phases that are.distinguished into biotite-hornblende granites (oldest), perthetic granites and graphic granites. while during the field work it is noticed that these granitic rocks are related to two magmatic phases which are characterized by petrological characteristic differences between each other.

They are represented by biotite – hornblende granite and perthite granite. These granites cross – cut a calc-alkaline diorite of pan African age of 552 ± 7Ma (Abdel – Rahman and Doig, 1987). These two types of younger granites will be described in the following lines. Biotite – hornblende granites are located in the northwestern part of the

El Kholy, D.M.M ---------------------------------------------------------------------------------------------------------------------------------


study area forming Gabal (G.) Umm Araka which occupies an area of about 66 Km² and extend southward to surround the perthite granites. It had intruded the diorite rocks in sharp intrusive contact in the north corner. They are enriched in basic metavolcanic and diorite xenoliths. In hand specimen, it is pinkish white in color and medium to coarse grained. They are composed of quartz with orthoclase and plagioclase in equal amounts in addition to biotite and hornblende as essential minerals. It is intruded by youngest perthite granites in its core in sharp contact (Figs.1) while in other places along this contact they were intercepted in each other. This indicate that the biotite – hornblende granites are older than the perthite granites. The biotite – hornblende granites are dissected by acidic dykes in NE - SW directions (Fig.1). Some of these dykes not pass through the pertite granites. Also, they are cut by major strike slip faults trending in NW – SE and NNW – SSE directions.

Microscopically, these granites are medium to coarse grained The quartz is coarse, anhederal with small sized opaque minerals as iron oxides. They are subsolvus with orthoclase of 0.5 -1.5mm in length and 0.5 -1mm in width which is subhederal to

anhederal and include quartz and some opaque minerals. The plagioclase crystals show 1 – 2mm in length and 0.5 – 1mm in width, slightly altered in the crystal core. The biotite crystals are dark brown to pale brown, euhederal to subhederal of variable sizes with small zircon crystals as inclusions which are surrounded by haloes due to presence of radioactive minerals in its crystal lattices. The biotete is chloritized along its boundaries and shows iron oxides along cleavage. Hornblende occur in small amounts as small subhederal crystals which are partly chloritized. Zircon, apatite, epidotes and iron oxides are the accessory minerals. Perthite granites are occupying an area of 181 km² in the central part of the area. It is intruded by high density of parallel acidic and basic dykes trending NE – SW. Thus, these granites are strongly sheared and altered around these dykes. In hand specimen, they are reddish pink, coarse to medium grained and composed mainly of quartz and orthoclase perthite with subordinate plagioclase. These granites are strongly hematitized and silicified near their contact with dykes, especially the basic ones. (Fig.1). They were dissected by strike slip



faults and fractures that directed NW – SE; rarely filled with dykes. Most of the NE –SW faults were intersected with the NW –SE ones and their intersections control most of the recorded radioactive anomalies (Fig. 1&2). The perthite granites are silicified, hematitized, episyenitized and kaolinized at the intersection zones of some major faults. They include numerous pegmatite pockets along their peripheries. Some parts are fine grained, especially near the contact with dykes. Microscopically, they are composed of medium to fine grains of perthite, quartz and plagioclase as essential minerals. Quartz shows anhederal to subhederal with 0.5 to1.5mm in length and 0.5 to 1mm in width reach to 2.5 mm in the phenocrysts and intergrows with the perthite and plagioclase and include dispersed grains of opaque minerals. The quartz shows cataclse appearance with wavy extinction due to deformation by structure. Patchy and string perthites are predominant and bounded along peripheries by secondary quartz and secondary albite. The perthite proportion exceeds the quartz and plagioclase.

The plagioclase (An8 –An14) is subhederal to euhederal and much fewer than perthite. It includes secondary quartz. Iron oxides, zircon, fluorite, allanite and chlorite represent the accessory minerals. Post Granitic Dykes

They are represented by acidic, basic and intermediate dykes. In addition to some veins which are comprising feldspars and quartz.

The acidic dykes involve, granite porphyry, aplites and pegmatite dykes. The basic dykes investigated in the study area are dolerites and basalts (Fig.1).

These dykes show variation in distribution within the different granite rocks in the study area since the biotite – hornblende granites are enriched in acidic dykes which some of them not passed in the perthite granites involve which acidic and basic ones and scarce basic dykes in graphic granites. Also, according to the dyke distribution the granite rocks can differentiate into oldest biotite – hornblende granites followed by perthite granites then youngest graphic granites

El Kholy, D.M.M ---------------------------------------------------------------------------------------------------------------------------------


Fig. 1: Geological and structural map of Gabal Abu Edam area, Eastern Desert, Egypt. Legend 1 : 100,000 - - - Post granitic dykes + + Biotite – Hornblende granites ± ± Perthetic granites o o Hammamat sediments x x Diorites * Radioactive anomalies

The map is modified after Moustafa (2001)

Fig. 2 : Landsate photo showing sharp intrusive contact (C ) between biotite – hornblende granite (BHGr)

and perthite granites (PGr) in G. Abu Edam area.

Study area

G. Abu W. Faliq El

W. Faliq El

CBHGr

PGr



STRUCTURAL FEATURES The structural features in the study

area are represented by primary and secondary structures. The first one are represented by well distinct bedding and laminations which are clear in the Hammamat sediments. These rocks are striking NW– SE and their dipping is varying between 10° and 27° to NE reaching to 50° due to deformation effect. The secondary type comprise, joints and faults. The main trends of the joints are NW – SE, NE –SW, NNW – SSE and ENE – WSW (Fig.3) and dipping to NE, SSE and ENE respectively. Some of the joints are filled with quartz, iron oxides, potash

feldspars and manganese oxides. Some of the joints surfaces trending NNW–SSE and NE–SW and their intersections show high radioactivity. The faults are of strike slip types and affected all the studied rocks in the study area (Fig.1). They are sriking in NNW–SSE, NW–SE, NE–SW and NNE–SSW directions ( Fig.4 ). The faults trending NE–SW cut those trending NNW–SSE and NW–SE. Some of these intersections are radioactive. Chronologically, The NE fault trend is the youngest one among the studied faults in the area.

0

50

100

150

200

250

E ENE NE NNE NS NNW NW WNW W

Fig. 3: Frequency histograms showing the prevalent trends of the measured joints in G. Abu Edam area

Fault directions

Frequency

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According to the field study of the

different rocks covering the study area , it is noticed that the perthite granites of G. Abu Edam appear as circular shape. The rocks are arranged from outside to inside the circular shape as follow; diorite (outside border) then biotite - hornblende granites followed by the perthite granites in the center. They could be arranged as synorogenic plutonites then late orogenic plutonites followed by post orogenic plutonites according to El shazly (1964) synonames or they can arranged according to Hussein (1982) as subduction and collision granite then post collision granites then anorogenic granites in the center of the circular form. According to these arrangements, the alkali feldspar

granites is intruded in calc alkaline granite (old phase of the younger granite) which intruded in the diorites. Therefore, this form is seem to be ring complex because it shows that the diorite emplaced first and intruded by biotite hornblende granites and the latter intruded by the alkali feldspar or syenogranites. RADIOACTIVITY

The radioactivity of the rocks covering the study area are measured. The measured radioactivity values and uranium contents are listed in table (1). The diorites record radioactivity values between 5Ur and 9Ur.The radioactivity values of the Hammamat sediments are ranging

between 11Ur and 19Ur reaching to 22Ur at the altered parts, especially

0

2

4

6

8

10

12

E ENE NE NNE NS NNW NW WNW W

Fault directions

Fig. 4: Frequecy histograms showing the main trends of the recorded faults in G. Abu Edam area

Fault directions

Frequency



along the contact with the younger granites. The younger granites show wide variation in radioactivity values due to age difference, the mineralogy and the magma type from which they are produced(Heinrich,1956). With reference to the younger granites, the biotite - hornblende granites, the radioactivity values are ranging between 28Ur and 34Ur with uranium content varying between 12ppm and 17ppm. The perthite granites, recorded radioactivity values between 44Ur and 50Ur with uranium content between 13ppm and 21ppm.

According to the measured radioactivity values, the younger granites are the most enriched in uranium content (Figs.5, 6). Also, the perthite granite type is the most radioactive one among the granite rock types (Table 1). This could be due to age relation, mineralogical composition and the effect of heat flow of the basic dykes during their extrusion within the perthite granites. This caused redistribution of the radioactive minerals within the granites and accumulated them near the contact with the basic dykes. Also the radioactivity increased due to hydrothermal solutions intruded along the major faults passing through the perthite granites. In addition to these factors, the resistant minerals such as

zircon which release the uranium after dissolving (Simpson et al, 1979) contribute in increasing radioactivity. Radioactive Occurrences

During the field radiometric survey, six radioactive occurrences are located in the younger granites in the study area. Four occurrences are situated in the perthite granites, one in the southern part of the biotite hornblende granites and the last one is discovered along fault affect the eastern border of G. Qattar (Fig 1 & 7).. Radioactive occurrences in the perthite granites

They are recorded in the altered granite around basic dykes, along faults and at the intersection zones of the major faults (Fig.7). Those around or near dykes are due to the thermal effect of the dyke magma and associated hydrothermal solution which contribute with its loads of mineralization, in addition, to the granite mineralization in increasing radioactivity of these spots. Some of these occurrences are episyenitized due to the dissolving of the quartz by the high temperature hydrothermal solutions intruded at the intersection zones of major faults (Fig.1 &7). Most of these occurrences are hematitized, silicified and metasomtized. The measured uranium content in these occurrences is ranging from 200ppm

El Kholy, D.M.M ---------------------------------------------------------------------------------------------------------------------------------


to 850ppm while thorium content varies from 150 to 600ppm, showing disequilibrium indicating that more uranium is added to the granites by the solutions (Table 2). Radioactive occurrence in biotite – hornblende granites

One radioactive anomaly is recorded in this granite in the extreme south western part of the area along major fault striking NW – SE (Fig.7). The granite in this location is strongly altered showing high dense hematitization with manganese oxides.

The uranium and thorium contents are varied between (500ppm–900ppm) and (600ppm–1200ppm), respectively (Table 2). The depletion of uranium could be due to leaching by water since the granite in this site is soft due to its alterations. Radioactive occurrence east G. Qattar

It is recorded along major fault trending NE – SW along W. Faliq Al Sahl (Fig.7).

This occurrence is strongly hematitized and silicified with quartz grains of smoky appearrance due its effect by radiations emitted from the radioactive minerals that caused damage in its crystal structure.

The uranium and thorium contents are 600ppm and 220ppm, respectively (Table 2). Factors Controlling High Radioactivity in the Granitic Rocks

The radioactivity in the studied granites is controlled by grain size, alterations, mineralogy and structural features.

Each of these factors contribute in increasing radioactivity in the younger granites of the study area. Grain size: this factor is well distinct in the perthite granite where the finer grained parts record high radioactivity, especially at the intersection zones of the faults (Fig.1) and near the contact with the basic dykes, since the fine grained one is less altered and hard, thus the radioactive minerals are well preserved.

The coarse grained granites are lower in radioactivity because most of them are strongly altered , thus the radioactive minerals could leached and escaped by weathering processes.

Alteration processes: They are represented by silicification, hematitization, kaolinization and episyenitization. It is noticed that the recorded high radioactive anomalies



Table 1 : Radiometrical values of the studied rocks in G. Abu Edam area

Rock types S.No Radioactivity cps*

Radielement unit Ur*

Uranium content ppm*

Diorites

1 2 3 4 5

50 55 75 80 70

5 6 8 9 7

4 4 6 8 5

Hammamat sediments

6 7 8 9

10 11 12

130 125 132 170 100 150 170

13 12 13 19 11 18 19

12 9 8

11 11 14 15

Biotite – hornblende

granites

13 14 15 16 17 18

300 305 250 310 280 275

33 34 27 34 31 30

13 15 17 14 12 17

Pertite granites

19 20 21 22 23 24 25 26 27 28 29 30 31 32

410 412 400 430 423 435 450 445 300 322 300 330 340 350

45 44 44 48 47 48 50 49 33 36 33 37 40 42

19 20 15 13 17 15 21 21 15 17 15 18 16 17

* cps : count per second * Ur : Radioelement unit * ppm : Part per million

Table 2: Radiometric analyses of the radioactive samples

S.No. Uranium content ppm

Thorium content ppm Lithological features

1 2 3 4

340 200 500 850

220 150 430 650

Perthite granite, showing hematitization, silicification, episyenitization and kaolinization recorded along faults

and near contact between the perthite granites and intruded basic dykes.

5 6

500 900

600 1200

Recorded in biotite hornblende granites along faults with hematitiztion and manganese oxides.

7 600 220 Recorded along faults with hematitization and metasomatism.

El Kholy, D.M.M ---------------------------------------------------------------------------------------------------------------------------------


are associated with the silicified and hematitized zones, especially at the intersection zones of the faults (Fig.1). Also, at the episyenitized parts some high radioactive anomalies are recorded. The episyenitization are formed due to hydrothermal metasomatism effect on the alkali feldspar granite by dissolving the quartz to make the rock as reservoir for ores (Cathelineau, 1986). Sarcia & Sarcia (1962) and Leroy(1971), noted that the magmatic texture remaine unchanged apart from the disappearance of quartz. The hydrothermally altered granites provides an excellent substrate for the

investigation of naturally occurring radioactivity due to its elevated level of uranium and thorium (Morton et al, 2002; Rogers and Adam,1963; Brimhall and Adam,1969; Richardson,1964;Fehn et al 1978), especially along faults and near the basic dykes. Mineralogy: This factor play important role in increasing radioactivity in some occurrences. The presence of zircon, hematite, xenotime, monazite and fluorite in the present granitic rocks is important because each of them associate with uranium and thorium with variable amounts (Abdel – Karim,1999).

050

100150200250300350400450500

1 4 7 10 13 16 19 22 25 28 31

Rad

ioac

tivity

in c

ps

uranium content in ppm

Fig.5 :Variation diagram showing relation between radioactivity values measured in count per second (cps) and uranium content of the different rocks in G. Abu

Edam area.

Diorite

Hammamat sediments

biotite Hornblendegranite

perthite granite



0102030405060

1 4 7 10 13 16 19 22 25 28 31

Rad

ioel

emen

t U

r

uranium ppm

Fig.6 :Variation diagram showing the relation between radioelement distribution and uranium content of the different rock units in G .Abu Edam area

Diorite

Hmmamat sediments

biotite Hornblende

Perthite granite

Fig.7: Landsate showing geological features and high radioactivity occurrences of G.Abu Edam area, Eastern Desert, Egypt

35> 35 70 Ur 70 100 Ur 100 135 Ur > 135 Ur

El Kholy, D.M.M ---------------------------------------------------------------------------------------------------------------------------------


Structural features: Most of the recorded high radioactivity are cited along major faults (Fig.1) due to the mineralized hydrothermal solutions extruded along their zones. These solutions are usually mineralized with hematite, silica, manganeze oxides in addition to the radioactive minerals. Also, many of the radioactive anomalies are recorded at the intersection of the follwing fault trends; NNW – SSE with NE – SW in biotite granites, ENE – WSW with NNE – SSW in perthite granites and N – S with NE – SW in Gattar granites (Fig.1). Each intersected two faults are structurally analyzed to determine principal stresses affecting these zones (Fig8,9&10).

In the perthite granites two major faults striking N50E – S50W and N15W – S15E are intersected with each other in the eastern part of the area (Figs.1 &7.

They are structurally analyzed by plotting cyclographic projection to determine principal stresses that affected the granite and resulting by the hydrothermal solutions along the intersections of the two faults. In figure (8), the principal stress ó1 is directed N24E with plunge of 53NE, causing those two intersected faults at the intermediate principal stress ó2 which trending S24W and plunging

37SW and least principal stress ó3which represent the maximum strain along which the rock responsed to the principal stress ó1, therefore the mineralized solutions found its way upward.

Figure (9), shows the cyclographic projection of two intersected major faults striking N70E – S70W and N20E – S20W affecting the biotite – hornblende granites in the southern part of the area (Figs. 1,7&9). The in this occurrence is affected by main principal stress ó1 directed N48E and plunging 65NE, intermediate principal stress ó2 which plunge 25SW and minimum stress ó3 plunging 1º SE. Along the minimum stress the intersection zon is opened causing the thermal solutions to be extruded with their radioactive minerals.

Figure (10), shows principal stresses affecting the eastern part of Gabal Qattar, producing two major faults striking N – S and N40E, where ó1 is directed N22E and plunge 67NNE, ó2 which orientedS22W with plunge of 23SW and ó3 that trend 1WNW. Along the least principal stress representing the maximum principal strain since the granite suffice strong deformation in the intersection zone making the mineralized solution to lift on the surface.

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the area affected by the major Red Sea graben.

During the field investigation, it is found that the diorites are intruded by the biotite – hornblende granites which subsequently intruded in their core by the perthite granites. The appear as ring of diorite surround ring of biotite hornblende granite which

include the perthite granite in the center of the ring. On the other hand, older granitoid as first layer surround calc alkalie granite as second layer which involve alkali feldspar granite in its core . Thus, it could be ring complex. This ring need more studies to be proved as geochemical analyses and petrogeneses.

العوامل التي تتحكم يف النشاط اإلشعاعي يف منطقة جبل أبو عضام

الصحراء الشرقية ، مصر درويش محمد محمد الخولي

ملخصمنطقة جبل أبو عضام يشغل المنطقة الشرقية من جبل قطار حيث يغطيها صخور الدايوريت ورواسب

وتنفذ الصخور الجرانيتية من خالل صخور الدايوريت والحمامات . الجرانيتية الحديثةالحمامات والصخور وينفذ . هورنبلند جرانيت والبيرثيت جرانيت –تتمثل الصخور الجرنيتية بالبيوتيت .في تالمس نافذ حاد

. اطق أخرىهورنبلند جرانيت نفاذا حاد في بعض المناطق ومتداخل في من –البيرثيت جرانيت خالل البيوتيت هذه الجدد تتجه شمال شق جنوب غرب. آما ينفذ خالل صخور المنطقة جدد حامضية وبازلتية

يتكون الدايوريت من . بتروجرافيا تتدرج الصخور الجرانيتية من الدايوريت الى الجرانيت الحديثالقليلة تتمثل بأآاسيد الحديد البالجيوآليز والهورنبلند وقليل من األورثوآليزآمعادن أساسية بينماالمعادن

التحت سولفي . يقسم الجرانيت الحديث الى الجرانيت التحت سولفي واألعلى سولفي. واألباتيت واإلسفينيشمل الكوارتز واألورثوآليز والبالجيوآليز والبيوتيت وقليل من الهورنبلند أما الجرانيت األعلى سولفي

المعادن اإلضافية تشمل الزرآون . جيوآليزيشمل البيرثيت والكوارتزوقليل من البال .واألباتيتواأللالنيتوالزينوتيم

بالنسبة للتراآيب األولية فإن التطبقات والخطوط .من الجانب الترآيبي ، تم تسجيل تراآيب أولية وثانويةتكون أآثر وضوحا في رواسب الحمامات التي تمتد في إتجاه شمال شرق جنوب غرب ، وشرق شمال شرق

.ب جنوب غرب ، وغرب شمال غرب وشرق جنوب شرقغرولوحظ أن أقل الصخور أشعاعياهو . ومن الجانب اإلشعاعي تم قياس الصخور الظاهرة في الحقل

ومن بين الصخور الجرانيتية الحديثة فإن الجرانيت . الدايوريت واألعلى إشعاعيا هوالجرانيت الحديثجزء في 21جزء في المليون إلى 13محتواه من اليورانيوم من البيرثيتي هو األعلى إشعاعيا الذي يتراوح

تم تسجيل الشاذات اإلشعاعية في مناطق الصدوع وتقاطعاتها وقرب مناطق التالمس بين الجدد . المليون 500جزء في المليون و 600لبازلتية والجرانيت وآان متوسط محتواها من اليورانيوم والثوريوم حوالي

من خالل الدراسة إتضح أن العوامل التي تتحكم في النشاط اإلشعاعي هي . على الترتيبجزء في المليون .المادة الصخرية والحجم الحبيبي والترآيب المعدني والتغيرات الحرارية والصفات الترآيبية

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REFERENCES

Abdel All Youssef Abdel All, 1996: Proterozoic A – Type Granite:A Study From The Northeastern Nubian Schield, Egyptian Journ. Of Geol., Vol. 40 – 2, P. 631 -660. Abdel – Karim, A. M., (1999): REE-rich accessory minerals in granites from southern Sinai, Egypt:Mineralogy, geochemistry andpetrogenetic implications, 4Th Int. Conf., On Geochem., Alex.Univ.Egypt, 15 – 16 Sept., p.83-100. Attawiya (1990): Petrochemical and chemical studies on granitic rocks from G. Qattar area, E.D.Egypt. Arab. J. Nucl. Sci. and Appli.,Cairo, Egypt, Vol.22: 13 -30. Akaad. M.K., and Noweir, A.M. (1980): Geology and lithostratigraphy of the Arabian Desert orogenic belt of Egypt between lat.25º 30´ and 26º 30´ N.Ins.App.Geol. Bull., King Abdel AzizUniv., Jaddah. 3 (4), p. 127- 135. Brimhall, W. H. and Adams, J. A. S., (1969): Concentration changes of thorium, uranium and other metals in hydrothermally altered Conway granite, NH. Geochim. Cosmochim. Acta 33: 1308-1311. Cathelinau, M., (1986): The hydrothermal alkali metasomatism effects on granitic rocks: Quartz

dissolution andrelated subsolidus changes. Centre de Recherches sur la Geologie de l´Uranium, BP23, 54501 Vandoeuvre les nancy Cedex, France, 945 – 965 P. Dardir, A.A. and Abu Zeid, K.M. (1972): Geology of the basement rocks between lat.27º 00´ and 27º 30´, Eastern Desert, Egypt. Ann.Geol.Surv.Egypt, V.2, p.129 -160. El Bouseily, A.M. and El Sokkary, A.A. (1975): The relation between Rb, Ba and Sr in granitic rocks. Chem. Geol., V.16 p. 207 – 220. El Gaby, S. (1975): Petrochemistry and geochemistry of some granites from Egypt. N.Jb.Miner.Abh., V.124, p. 147 – 189. El Gaby, S., List, F.K. and Tehrani, R., (1990): ˝The basement complex of the Estern Desert and Sinai˝. In: SaidR. (Edittor): Geology of Egypt. Pulkema Published.Netherlands, p. 175 – 184. El Ramly, M.F. (1972):Anew geological map for the basement rocks in the E.D. and W.D., Egypt, scale 1:1,000,000, Annals, Geol. Surv., Egypt, Vol.11, 1 -18 El Schazly, E.M., (1964):On the classification of the Precambrian and other rocks of magmatic affiliation in Egypt. 22nd Int. Geol. Congr. India.



Fehn, U., Cathlex, L.M. and Holland, H.D., (1978): Hydrothermal convection and uranium deposits in abnormally radioactive pluton. Ecom. Geol. 73:1556-1566. Gass, I. G.,1981: ˝Pan African (Upper Proterozoic) plate tectonics of the Arabian Nubian Shield˝. In Kroner, A., (Editor) : Precambrian plate tectonics. Amsterdam, Elsevier, p.385 – 405. Greenberg, J.K. (1981): Characteristic and origin of Egyptian younger granites. Summary Bull. Geol. Soc. Am., V. 92, p. 224 -232. Hassan, M. A. and Hashad, A. H. (1990): “Precambrian of Egypt”. In: Said,R. (Editer), Geology of Egypt. Bulkema Publishers, Netherlands, p.201 – 248. Heinrich,E.W. (1958) : Mineralogy and geology of radioactive raw materials. Mcgraw–Hill Book Company, Inc., New York, p.27 -140. Hussein, A.A., Ali, M.M. and Elramly, M.F. (1982): A proposed new classification of the granites of Egypt. J. Volc. Geoth. Res., V.14, p.187 -198. kennedy, W. Q., 1964: ˝The structural differentiation of Africa in the pan African (± 500m.y.) tectonic episode˝. Res. Int. Afr. Geol., Univ. of leeds8th Ann.Rept., p.48 – 49. Khalaf, M.A. (1995): Petrochemical and mineralogical characteristics of some U – bearing younger granites, N.

E. D., Egypt. MSc., Faculty of sciences, Cairo Univ., Cairo, Egypt, 78p. Leroy, J., (1971): Les episyenites non mineralisees dans le massif de granite a deux micas de Saint Sylvestre. Equilibre entre mineraux et solutions. Unpublished thesis, Nancy I University, France. Loiselle. M.C., and Wones, D.R. (1979): Characteristics and origin of anorigenic granites. Geol. Soc. Am.Abst. Programs, V. II, 468 p. Morton, L.S., Evans, C. V. and Estes, G.O. (2002): Heavy metals in the environment, Published in J.Environs. Qual. 31 : 155-162. Moustafa, M. (2001): Geology and radioactivity of Faliq Al Waar and Faliq Al Sahl area, North Eastern Desert, Egypt, Master degree, Faculty of Sciences, Cairo Univ., Giza, Egypt, 250p. Mussa, E.M.M. (1994): Geochemistry of some granitic masses and their relation to the tectonic evolution of the northern E.D., Egypt. MSc. Thesis, Faculty of Sciences, Ain Shams University, Cairo, Egypt., 214p. Nossair,L.M. and Ahmed, F.Y., (1999):On the geology, geochemistry and U–Th potentiality of Gabal Salaat El Bali and Gabal El Reddah granitoids, Eastern Desert, Egypt, 4th

El Kholy, D.M.M ---------------------------------------------------------------------------------------------------------------------------------


Intern. Conf. On Geochem. Alex. Univ., Egypt, 15 -16 Sept. p.271-290. Noweir, A.M., Seweifi, B.M., and Abu Ela, A.M. (1990):Geology, petrography, geochemistry and petrogenesis of the Egyptian younger granites. Qatar Univ.Sci.Bull., V. 10, p. 363 – 393. Richardson, K. A., (1964): Thorium, uranium and potassium in the Conway granite, New Hampshire, U.S.A. In the natural radiation environment. Univ. of Chicago Press, p. 39-51. Rogers, J. J. W. and Adam, J. A. S., (1963): Log normality of thorium concentration in the Conway granite. Geochim. Cosmochim. Acta 27: 775-783. Rogers, J.J.W., and Greenberg, J.K. (1990):Late orogenic, post orogenic and anorogenic granites: distinction by major element and trace element chemistry and possible orogins. J. Geol., V.98, p. 291 – 983.

Sabet, A.H. (1972): On stratigraphy of the basement rocks of Egypt. Ann.Geol. Surv., Egypt, V.2, p.79-109. Salman, A.B., Shalaby, M.H. and Nossair, L.M. (1990): U province, N Red Sea hills, Egypt. Proceeding of international Earth Sciences Cong. on Aegean region, Izmir, Turkey, 1 -6 October, Vol. 1 : p.89 -101. Sarcia, J. & Sarcia, J. A., (1962): Gites et Gisement du Nord Limousin. In : Les Minerals Uraniferes Francais, Paris, P.U. F., p. 190 -292. Simpson,P.R.; Brown,G. C.; Jan, P. and Ostel, D.,(1979):Uranium mineralization and granite magmatism in the British Isles, Institute of Geol. Sciences, Vol. 291, p. 385 – 412.

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