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Geological and Radiological Studies of the Mount Arafat, Mekkah, Saudi Arabia

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Geological and Radiological Studies of the Mount Arafat, Mekkah, Saudi Arabia 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 Á Saudi Arabia Á Petrography Á been classified as a granodiorite rock which mainly consists of Fission track dating Á Primordial radionuclides Á 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 (&) Á M. Ali Á A. Waheed Á S. Manzoor Á M. A. Baloch Á S. Batool Á 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 Á 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.
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