J Radioanal Nucl Chem (2012) 293:955–963 DOI 10.1007/s10967-012-1776-0

Geological and radiological studies of the Mount Arafat, Mekkah, Saudi Arabia

A. A. Qureshi • A. Sultan • A. Rashid • M. Ali • A. Waheed • S. Manzoor • M. A. Baloch • Matiullah • S. Batool • H. A. Khan

Received: 22 March 2012 / Published online: 10 April 2012 Ó Akade´miai Kiado´, Budapest, Hungary 2012

Abstract Mount Arafat is a sacred place for Muslims. It has Keywords Mount Arafat Saudi Arabia Petrography been classified as a granodiorite rock which mainly consists of Fission track dating Primordial radionuclides feldspar and quartz, muscovite, etc. During the Hajj and Umra, Radiological studies Muslims visit this holly place and stay there for some time. In order to study the geology and thermal history as well as to assess the radiological hazards due to the presence of pri- mordial radionuclides, systematic studies using petrographic, Introduction fission track dating and c-spectrometric (HPGe) techniques were carried out. Our study yielded fission track age of The Mount Arafat is a small hill on the east of Mekkah at a 9.13 ± 1.05 Ma of the Mount Arafat granodiorite. Rifting, distance of 19.67 km from Kaaba. It is located at a latitude of magmatism, volcanism and sea floor spreading that resulted in 21°.21‘38N and longitude 39°.50’56E; see Fig. 1. It reaches the formation of Red Sea seems may have altered the original about 70 m in height and has a reduced level of 454 m. Its age of the Arafat granodiorite under study to 9.13 ± 1.05 Ma. composition mainly is of rocks which consist of Feldspar and Measured radioactivity concentrations due to 226Ra, 232Th and quartz with minor amounts of clinozoisite/epidote, clinoch- 40K were found to be 10.75 ± 3.92, 29.21 ± 4.34 and lore etc. and muscovite, hornblende, titanite, biotite, apatite 664.49 ± 7.45 Bq kg-1, respectively. From the measured and sphene as accessories. The rock is classified as a radioactivity, gamma index (Ic) and radium equivalent (Raeq) granodiorite as per IUGS classification of the Plutonic rocks were calculated as 0.402 and 103.23 Bq kg-1 whereas out- [1]. During the current study, fission track age of Arafat door external dose (Dout) and annual effective dose (Eout)were granodiorite is estimated to be 9.13 ± 1.05 Ma. The gran- estimated to be 40.30 nGyh-1 and 0.045 mSvy-1 respec- odiorites exposed elsewhere in the Saudi Arabia are of more tively. All the above mentioned values are well below the than 600 Ma age. recommended limits. The Mount Arafat thus does not pose The hill is where Muhammad (peace be upon him) any radiological health hazard to the general public. delivered his farewell sermon to the Muslims towards the end of his life. The level area surrounding the hill is called the Plain of Arafat. During Hajj, the pilgrims should spend the A. A. Qureshi (&) M. Ali A. Waheed S. Manzoor M. A. Baloch S. Batool H. A. Khan afternoon of 9th day of Dhu al-Hijjah in Arafat. Muslims Radiation Physics Laboratory, Department of Physics, believe that Adam and his wife Eve reunited on the hill and COMSATS Institute of Information Technology, Chak Shahzad, Allah forgave after 200 years of separation caused by their Park Road, Islamabad, Pakistan disobedience in deference to the suggestion of Satan, hence e-mail: [email protected] it’s other names Jabal ar-Rahmah or Mountain of Mercy. For A. Sultan A. Rashid these reasons, the Mount Arafat is a sacred place for the Atomic Energy Minerals Centre, Ferozepure Road, Muslims. Geological, fission track dating and environmental Lahore, Pakistan studies on a sample consisting of numerous small chips Matiullah collected from Mount Arafat, Mekkah, Saudi Arabia was Physics Division, PINSTECH, Nilore, Islamabad, Pakistan carried out. The details of these studies are below. 123 956 A. A. Qureshi et al.

Fig. 1 Jabal Arafat or mountain of mercy, this is the place where first human being ADAM, exiled from Paradise and sent to earth, here He prayed Allah for mercy and His prayer was accepted and he was united with his wife. This is also the place where Muhammad (PBUH) delivered his last sermon to the Muslims. (Photograph from Google Earth)

Petrographic studies using thin section of rock under a radiation emitted by the decay products of 232Th, 235U, 238U polarizing microscope were carried out to study the texture and 40K present in the building materials and radon. Outdoor and structure of the rock to understand the origin, geology and indoor exposure to radiation depend upon the concen- of the Mount Arafat and its evolutionary history. tration of radionuclides in the rocks/soil and duration of Fission track dating, a radiometric dating technique, is occupancy. Keeping in view the frequent visits of Muslims to based on the analyses of the damage trails, or tracks, left by the Mount Arafat during Hajj and otherwise, study regarding fission fragments in uranium-bearing minerals present in the measurement of natural radionuclides present in the rock rock. Current research using fission tracks is one to sample was carried out. (a) understanding the evolution of mountain belts; (b) study- ing the thermal evolution of basins; (c) dating and provenance determination of archeological artifacts etc. Fission track Geology of Saudi Arabia dating studies on the sample were carried out for under- standing the evolution and thermal history of Mount Arafat. The Saudi Arabian Plate was a part of a larger geological All kinds of rocks, ‘‘soils and minerals’’ contain natu- entity, the Arabian-Nubian plate that once constituted the rally occurring radionuclides. The presence of natural core of Gondwanaland [3]. The Arabian-Nubian plate radioactivity results in radiation exposure. There are three covers several Asian-African countries, mainly Saudi sources that contribute towards the environmental radio- Arabia, Egypt, Eritrea, Ethiopia, Somalia, Sudan and activity and exposure to public. The main source is the Yemen. The basement of Saudi Arabia plate is made up of primordial radionuclides of terrestrial origin which our Arabian shield rocks. The shield rocks are overlain by a earth inherited at the time of its creation. The cosmogenic cover of sedimentary rocks of younger ages and extensive and anthropogenic radionuclides are insignificant because lava fields extending from Yemen to Syria. The shield of their low abundance. The most commonly encountered rocks are exposed in the western part of Saudi Arabia. The primordial radionuclides include 232Th, 235U, 238U and younger sedimentary rocks are exposed elsewhere. Detail their decay products and 40K[2]. of distribution of these rocks is given below. Annual average radiation dose received by a person from various sources is 300 mSv. The major contribution Arabian shield rocks (200 mSv) of this dose is from primordial sources and their decay products especially radon. Human body is exposed to The Arabian shield consists of metamorphosed volcano- the radiation via outdoor exposure to gamma radiation sedimentary rocks of Proterozoic age (&2,500–4,500 Ma emitted by the decay products of 232Th, 235U, 238U and 40K old). The volcano-sedimentary rocks underwent deforma- present in rocks and soil and indoor exposure due to gamma tion and metamorphism during the evolution of shield and

123 Geological and radiological studies of the Mount Arafat 957 were intruded by granitic and gabbroic rocks covering seconds to remove scratches due to the carbide powder. about 55 % of the shield area. The intrusive rocks are Then cover glass was cemented firmly on the section. The mainly granitic (63 %), intermediate (31 %) and mafic to thin section was studied under polarizing microscope fitted ultramafic (6 %). The Arabian shield is composed of a with a digital camera. number of smaller segments welded together by NW and NE trending sutures [4]. The sutures divide the shield into Heavy minerals separation five tectonic zones [5, 6]. The Midyan, Hijaz and Asir tectonic zones are on the Red Sea side, whereas, the Afif For fission track dating and heavy minerals studies, the sample and Ar Rayan zones are on the other side. The Mount was crushed and ground through standard procedures. The Arafat is located in the Mekkah quadrangle which is a part ground material was passed through various sieves. The Asir tectonic zone [7]. fraction between 105 and 250 lm was found suitable for fis- sion track dating and stereo-microscopic observations. Sedimentary rocks Aliquot of 20 g of the sieved material was put in a separating funnel containing bromoform (Sp. grav- The sedimentary rocks of Phanerozoic (younger than ity = 2.89), for separation of light and heavy fractions. 540 my) age in the north and east of Arabian shield con- Both, the lighter and heavy fractions were dried and stitutes the Arabian platform. These rocks overlay the weighed. After density separation, 1.80 g of heavies and Arabian shield and are hence called as cover rocks. Since 18.20 g of lights were obtained. The heavy fraction was ‘‘Precambrian times’’ the shield has been relatively a stable subjected to magnetic separation, on Frantz’s iso-magnetic block except sea transgression on the eastern side where dynamic separator to get various fractions. Finally, apatite thick continental and shallow marine sediments were and sphene were isolated using the stereomicroscope. deposited. The Red Sea coastal plain is a relatively narrow zone that comprises of Oligocene-recent sedimentary Sample preparation for fission track dating rocks. A series of clastic sediments were deposited on the older marine deposits of Eocene age of Tethyan affinity. Apatite and sphene was found in the heavy minerals con- The clastic sediments are overlain by marine beds of centrate. Clear apatite grains were mounted in epoxy,

Miocene times. polished and etched in 2 % HNO3 for 50 s to reveal the spontaneous fission tracks. The spontaneous tracks were Cenozoic Harrats counted in the apatite at 9400 magnifications. The apatite was than irradiated in the reactor along with a Lexan A large part of the Arabian shield is covered with the detector for 100 s at 10 MW power to determine the extensive lava fields extending intermittently in NW induced track density. Standard reference glass SRM-614 direction from Yemen to Syria. Their distribution is related was used to calculate reactor fluence. to the extensional fissure caused by the pulling apart of the Fission track age of apatite was calculated using the Arabian and African blocks which later resulted in the simplified age determination formula of Durrani and Bull formation of Red Sea at the end of Oligocene (&25 Ma). [10] given below. The lava fields consist of dikes of gabbros and dolerites TðÞffi Age 6  10À8  q q  F years: ð1Þ placed in the fissure. The magma also reached the surface s i and formed extensive basaltic plateaus called as Harrats. The qs is the spontaneous track density, qi is induced The latest volcanic eruption was dated as young as the track density, and F is the reactor fluence. The constants, 1256 AD from Harrat Rahat. used for age calculation are; fission decay constant -1 kf = 8.4 9 10–17 year [8], the uranium isotopic ratio (235U/238U) I = 7.26 9 10-3, and the thermal neutron 235 -2 Experimental fission cross section (df) for U as 5.8 9 10–23 cm [9].

Slide preparation Samples preparation for HPGe

A rock piece was cut to obtain a thin slice approximately A part of the sample crushed for dating and heavy minerals 3 mm in thickness. The thin slice was cemented on a glass separation was dried in an oven at 110 °C for 24 h [10, 11]. slide with canada balsam. The slice was then ground on a The sample was then sealed in the standard Marinelli rotating lap using various silicon carbide powders until the plastic beaker [12, 13]. The reference materials, RG-set and standard thickness of 0.03 mm was obtained. Finally, the soil-6 sample, was also sealed in the Marinelli beaker. The section was polished with 6 l diamond paste for a few sample was then stored for ‘‘40 days’’ to bring radon 123 958 A. A. Qureshi et al.

(222Rn) and its daughter products in equilibrium with Feldspar grains are dominantly plagioclases with anor- radium [14–16]. thite content 20–50 % (oligoclase to andesine). They are Radiometric measurements were performed for the usually sub-hedral in shape and show conversion to cli- identification and quantitative determination of radionuc- nozoisite/epidote and muscovite. ‘‘Albite’’ and ‘‘Carlsbad’’ lides present in the rock sample. The special emphasis was twinning is seen in the plagioclases as shown in photomi- on the concentration of 226Ra, 232Th and 40K. Gamma crograph Fig. 3. The plagioclase crystals give biaxial counting of the sample was carried for 30,000 s, and the positive and negative figures. Plagioclase grains have high spectrum was stored in PC based multichannel analyzer. to moderate degree of alteration to clinozoisite/epidote, The c-ray spectrum was analyzed with the help of a com- muscovite and sericite. Clinochlore appears to be an puter based multi-channel analyzer after counting. The alteration product of hornblende. Alkali feldspar was 226Ra and 232Th was analyzed on the basis of the peaks of identified as orthoclase and perthitic orthoclase. 214Bi, and 214Pb for 226Ra and 228Ac and 208Tl for 232Th in Quartz crystals are anhedral in shape. Occasionally, equilibrium with their parent nuclides [17, 18]. The anal- effects of cataclasis can be seen in quartz. The quartz ysis of 40K was based upon its single peak of 1,460 keV. crystals are fractured and show deformation that can be The peaks of interest are shown in Fig. 2. seen in the photomicrograph shown as Fig. 4. At few places, inclusions were also observed in some quartz grains. The extinction of quartz generally is wavy. Clino- Results and discussion zoisite/epidote is abundant in the rock as seen in the pho- tomicrograph Fig. 5. It appears to be an alteration product Petrography of feldspar. A layer of clinozoisite, about 1 mm thick, was seen in one side of the thin section. While, at other places, The rock is holocrystalline with anhedral to sub-hedral it is often associated with feldspar grains. The clinozoisite/ crystals and interdigitating crystal boundaries. Crystal size epidote has high refractive index and is anhedral in shape. varied from 0.175 mm up to 1.80 mm. Thin section studies Muscovite occurs as an alteration product of the pla- reveal that the rock consists, dominantly of feldspar and gioclase. Titanite crystals are irregular in shape and have quartz. Minor minerals include clinozoisite/epidote, cli- very high relief and extreme birefringence. At some places, nochlore etc. Approximate modal composition consists of typical diamond-shaped crystals of titanite are present. plagioclase (50 %), alkali feldspar (18 %), quartz (19 %), Biotite and hornblende are pale green in color. The titanite, clinozoisite/epidote (7 %), clinochlore (4 %) and accesso- clinochlore (Fig. 6.) and clinozoisite were confirmed ries (2 %). Accessory minerals include muscovite, titanite, through X-ray studies. Apatite was identified through hornblende, biotite etc. XRD, but no traces could be found in the thin section. The

Fig. 2 Typical HPGe gamma ray spectrum due to the naturally occurring gamma emitting radionuclides in the Arafat granodiorite. The 226Ra has been identified by 214Pb and 214Bi peaks. The 232Th was identified by spectrum peaks of 208Tl and 228Ac, while the 40K was identified by its own peak

123 Geological and radiological studies of the Mount Arafat 959

Fig. 5 Photomicrograph of Clinozoisite crystal, in cross polar light, showing first order interference colors (grayish blue). Epidote is also Fig. 3 Photomicrograph showing plagioclase crystal. The ‘‘Carls- seen but its crystals appear in extinction position bad’’ twining is visible. The alteration of feldspar into clinozoisite / epidote and muscovite is also seen. (Picture taken in cross polar light, XPL)

Fig. 6 Photomicrograph showing grassy green colored clinochlore, Fig. 4 Photomicrograph showing mainly quartz and plagioclase in plain polarized light (PPL). Note the crystal habit, which is thin to crystals. Quartz crystal is anhedral in shape and contains inclusions. thick pseudo-hexagonal in shape with tapering pyramidal faces The ‘‘Albite’’ twining and alterations are visible in the plagioclase grain (lower left corner). (Picture taken in cross polar light, XPL) microscope for fission track dating studies. Zircon was not seen in the sample. rock has been classified as granodiorite, as per IUGS classification of igneous plutonic rocks [1]. Fission track age of Arafat granodiorite

Heavy minerals About 1.5 kg of granodiorite sample was processed to obtain minerals for fission track dating studies. In total 49 The heavy minerals fraction was studied under stereomi- apatite grains were recovered. After mounting and polish- croscope for the identification of minerals. Few grains were ing, 32 grains survived for dating studies. Out of 32 grains analyzed through X-ray diffraction technique. Clinochlore, only 11 grains were good enough for etching, reactor clinozoisite/epidote, apatite and titanite (sphene) were exposure and track counting. So our dating studies are identified through X-ray diffraction studies. based on a very limited data. On the basis of track analysis, Light minerals identified were mainly quartz/feldspar the fission track age of the Arafat granodiorite was (90.19 %) and biotite (3.93 %) amphibole (0.01 %). the obtained as 9.13 ± 1.05 Ma years. This age is very young heavy minerals suit was identified as clinochlore (4.18 %), as compared to ages determined on granodiorites exposed clinozoisite/epidote (1.47 %), magnetite (0.10 %), hema- elsewhere in the Saudi Arabia. For details of the fission tite (0.07 %), apatite (0.03 %), titanite (sphene) (0.02 %) track age of Arafat granodiorite see Table 1. and pyrite traces. Apatite and titanite (sphene) was asso- In Saudi Arabia, the granodiorites are exposed at more ciated with nonmetallic fraction and were separated under a than 15 localities in combination of various other rocks 123 960 A. A. Qureshi et al.

Table 1 Fission track age of apatite from Arafat granodiorite Crystal Crystal area Spontaneous track density (qs) Induced track density (qi) Fluence Age no. (910-5 cm2) (9105 cm-2) (9105 cm-2) (91014 ncm-2) (Ma)

4 5.26 0.76 1.14 4.53 9.06 5 3.90 0.57 0.85 4.53 9.11 6 0.13 915.38 1361.53 4.53 9.13 7 6.78 3.83 6.63 4.53 7.85 8 4.00 2.25 3.75 4.53 8.15 9 3.47 0.53 0.84 4.53 8.57 12 2.86 5.94 8.39 4.53 9.62 18 5.47 0.79 1.19 4.53 9.02 19 4.38 0.57 0.82 4.53 9.33 24 0.17 370.58 423.52 4.53 11.89 29 9.62 33.32 5.19 4.53 8.69 Average age 9.13 ± 1.05 Ma

-17 -1 The ages reported have been calculated using the fission decay constant kf = 8.4 9 10 year (Spadavecchia and Hahn [9]), uranium isotopic 235 238 -3 235 -22 -2 ratio ( U/ U = 7.26 9 10 ) and thermal neutron fission cross section (df) for U as 5.8 9 10 cm [10]. The reactor fluence was determined by means of SRG-614 fixed on Lexan by using Au-neutron dose calibration. The apatite and SRG-attached to Lexan were irradiated in the reactor for 100 s at 10 mW power in Pakistan Research Reactor at Pakistan Institute of Nuclear Science and Technology, Islamabad. Apatite was etched in 2 % HNO3 for 50 s and Lexan in 6.5 M NaOH at 50 °C for 50 min. The age was calculated by using the simple age equation t = 6 9 10-8 qs F years of Durrani and Bull [10] qi

[19]. Some of these are; Dhukhr Complex-815-810 Ma, 9.13 ± 1.05 Ma. So it is assumed that the present fission Filh granodiorite-age uncertain, Al Far granodiorite track age of the Arafat granodiorite is an age over printed *700 Ma, Haml suite monzogranite and granodiorit by later tectonics. *640–625 Ma etc., Ages of these granodiorites are radiometric ages and not fission track ages and are mostly Radionuclides in the Arafat granodiorite older than 600 Ma. No data on fission track ages on granodiorites of Saudi Arabia are available in the literature. Activity concentration of 226Ra, 232Th and 40K was found Tertiary dike complex and co-magmatic volcanic rocks to be 10.75 ± 3.92, 29.21 ± 4.34 and 664.49 ± of 30 Ma age, related to Red Sea rifting, in the central 7.45 Bq kg-1, respectively. Results of gamma activity Saudi Arabian coastal region record early stages of mag- (Bq kg-1) concentration of the Arafat granodiorite and its matism. This episodic magmatism in the region continued comparison with some other countries are given in Table 2. up to the present. Formation of Red Sea began as a crustal Our values are comparable with the granodiorites of extension, along with faulting and graben formation and Bergama, Turkey and Carpathian, Slovak [20, 21]. Relative dike-swarm intrusion. The style of crustal extension and contribution to total activity concentration in Arafat intrusion changed approximately 20 Ma ago, when local- granodiorite due to 226Ra, 232Th and 40K is shown in Fig. 7. ized volcanism and sheeted dike injection ceased and were The radioactivity level of 40K is much higher than the replaced by the intrusion of thick gabbro dikes [19]. This 226Ra and 232Th. This is because of the fact that the change might have marked the onset of sea-floor spreading, granodiorite contains 15 % Na ? K bearing feldspar. in the central Red Sea. At about 5 Ma, as a result of sea- floor spreading an intermittent marine environment Calculation of radiological effects between the Gulf of Suez and the Indian Ocean was established where water accumulated and evaporated While calculating the radiological hazards, we were only leaving behind evaporitic deposits. By the time Pliocene concerned with outdoor hazards as Arafat granodiorite is not began, the basin opened to the Indian Ocean and hence was used as a building material. Only a few people like camel filled with sea water. men, guides, vendors, etc. remain in the area for some time Like other granodiorites of the Saudi Arabia, the Arafat whereas the visitors come to Mount Arafat for a brief dura- granodiorite may have been emplaced much earlier. Mag- tion. The radiological hazards of Arafat Mount have been matism, volcanism, rifting and sea floor spreading, as dis- evaluated by calculating radium equivalent activity (Raeq), cussed above, continued up to 5 Ma in the area seems to gamma index (Ic), outdoor external dose (Dout) and annual have altered the age of Arafat granodiorite under study to effective dose (AED) as per detail below. The formulas used 123 Geological and radiological studies of the Mount Arafat 961

Table 2 Specific gamma activity (Bq kg-1) concentration of Arafat granodiorite and its comparison with some other countries [21, 22, 27–29] Country/rock Specific activity (Bq kg-1) Total Reference 226Ra 232Th 40K

Arafat Saudi Arabia granodiorite 10.75 29.21 664.49 704.45 Present studies Bergama Turkey granodiorite 29–111 35–87 698–1,100 Karadeniz [21] Carpathian Slovak granodiorite 1–49 2–54 30–1376 Rusko and Andras [22] India granite 93 306 1,074 1,473 Sannappa et al. [27] Akeokuta Nigeria granite 22–29 289–301 49–56 – Gbadebo [28] Ikogosio Nigeria granite 81 249 58 308 Gbadebo [28] Egypt granite 57 53 1,041 1,151 Ahmed [29] Germany granite 76 70 1,465 1,611 Ahmed [29]

A A A I ¼ Ra þ Th þ K : ð3Þ c 300 200 3000 The gamma index for the Arafat granodiorite was found to be 0.402 Bq kg-1, which is less than the safe limit of unity.

Outdoor external dose (Dout)

The outdoor external dose for the Arafat granodiorite was calculated using the following Eq. 1;

Dout ¼ 0:462:ARa þ 0:623:ATh þ 0:0417:Ak: ð4Þ The value comes out to be 40.30 nGyh-1; which is lesser than the mean value of the worldwide average of 51 nGyh-1. The maximum permissible dose rate is 55 nGyh-1. Fig. 7 Relative contribution to total activity concentration due to 226Ra, 232Th and 40K in the Arafat granodiorite. The 40K is the major gamma (94.33 %) activity contributor Annual effective dose (AED) for the calculation of various indices have also been given in Degree of a radiological hazard is calculated on the basis of Table 3 for easy reference of the reader. annual radiation dose received by an adult working in the radiation area. The dose rate is converted to annual effec- Radium equivalent activity (Ra ) eq tive dose (AED mSvy-1) by using the following relation: À1 À1 À1 Radium equivalent activity (Raeq) was calculated in order AED ðmSvy Þ¼ DðoutÞ ðnGyh ÞÂ8760 ðhy Þ O to assess the overall radiological hazard of the Arafat  0:7ðSvyÀ1ÞÂ10À6 ð5Þ granodiorite, using the following equation [22–25]:  where, D is the dose rate (nGyh-1), O is the occupancy A A A (out) Ra ¼ Ra þ Th þ K  370 ð2Þ factor, and 0.7 Sv Gy-1 is the dose conversion factor. eq 370 259 4810 Annual effective dose for an adult working as a guide, where ARa,ATh and AK are the activity concentrations of camel man or some other serving in refreshment centers 226Ra, 232Th and 40KinBqkg-1 in Arafar granodiorite. around Arafat granodiorite area was calculated in mSvy-1. -1 The (Raeq) was found to be 103.23 Bq kg which is less Total time spent in a year by an adult in the working area is than the safe limit of 370 Bq kg-1. about 1,600 hy-1, therefore, occupancy factor is assumed to be 0.18. The outdoor external dose D(out) of Gamma index (Ic) 40.30 nGyh-1 was calculated. The value of AED comes out to be 0.045 mSvy-1, which is far below the limit of The gamma index for the Arafat granodiorite was calcu- 20 mSvy-1 for people working in radiation area; it is even lated using the following equation of European Commis- lower than the limit of 1 mSvy-1 for the general public sion [30]. [26]. Casual visitor like pilgrims for Hajj and Umra are 123 962 A. A. Qureshi et al.

exposed to a very nominal radiation dose. A comparison of

6 226 232 40

À activity concentration due to Ra, Th and K in Arafat 10 ]) granodiorite and similar rocks of the other countries is  31

F given in Table 2. Â Þ 1 - out ð (ICRP [ ]) D 1 - 33 Â Conclusion T ¼ (Ali [ 0.045 mSvy E The minerals suit in the Arafat Granodiorite consists of ]

33 quartz ? feldspar (90.19 %), clinochlore (4.18 %), biotite –

30 (3.93 %) and clinozoisite/epidote (1.47 %). Other minerals , k

23 are magnetite, hematite, apatite, titanite (sphene), amphi- bole etc. Fractures rotation and deformation of quartz

0.0417A crystals indicates that the Mount Arafat had undergone

= some dynamic processes of metamorphism and folding/ Th ) Annual effective dose (E)

]) 1 mSvy faulting. The rock has been classified as granodiorite, as out 1 per IUGS classification of igneous plutonic rocks [1]. 0.604A Like other granodiorites exposed elsewhere in the Saudi ? ]) 1 Ra Arabia, the Arafat granodiorite may also have been em- 1

- placed around 600 Ma. Because of the sensitivity of tracks, (UNSCEAR [ 1

- to heat and pressure the later magmatism, volcanism, rif- 0.462.A

= ting and sea floor spreading that resulted in the formation out (UNSCEAR [ of Red Sea seems to have altered the age of the Arafat 40.30 nGyh D granodiorite under study to 9.13 ± 1.05 Ma. So it is

], assumed that the present fission track age of the Arafat 23

]) 55 nGyh granodiorite is an age over printed by geological events 32 related to Red Sea formation. ) and annual effective dose (E) of Arafat granodiorite [ The activity concentration due to 226Ra, 232Th and 40K out in the Arafat granodiorite is 10.75 ± 3.92, 29.21 ± 4.34

], Ibrahim [ and 664.49 ± 7.45, respectively, which is lower than the 23 typical activity concentrations in granodiorite rocks. The

) Outdoor external dose (D 226 232 40

eq total activity concentration due to Ra, Th and Kis -1

370 (Beretka and Mathew [ 704.45 Bq kg , is lower than the values reported for

 granodiorites of Bergama, Turkey and Carpathian, Slovak. K

A The gamma index (Ic), radium equivalent activity (Ra ),

4810 eq ), outdoor external dose (D þ outdoor external dose (Dout) and annual effective dose are eq Th 1 259 A (Beretka and Mathew [ - ]) all within the safe limits. The annual effective dose (Eout)is þ 1 -1 32 -

Ra far below the limit of 20 mSvy for people working 370 A ÀÁ Arafat area; it is even lower than the limit of 1 mSvy-1 for ¼

eq the general public. Casual visitors to this site including Ibrahim [ 103.23 Bq kg Ra pilgrims receive a negligible dose of radioactivity during a day stay on or around the Mount Arafat. (EC K ), Radium equivalent activity (Ra A c 3000 þ 1 - Th ]) 370 Bq kg 200 ), radium equivalent activity (Ra A c 33 þ References Ra 300 ]) A 30 ¼ [ 1 (Ali [

c 1. UNSCEAR (2000) Effects from natural radiation sources. United 0.402 Bq kg I \ Nations Scientific Committee on Effects of Atomic Radiation, New York

Gamma index (I 2. Le Maitre RW (1989) Blackwell, Oxford, p 193 3. Abbady A (2005) Indian J Pure Appl Phys 43:589–593 4. Johnson PR (2006) Technical report SGS-TR-2006-4 calculated limit Value Formula used Permissible Index Gamma index (I Table 3 5. Abdelsalam MG, Stern RJ (1996) J Afr Earth Sci 23:289–310

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