The document summarizes previous exploration studies of the late Ordovician Dubaydib sandstone formation in Jordan which indicated high concentrations of radioactive and rare earth elements. The current study aims to delineate promising areas in the formation for future study based on recent sampling and data from 2009. Exploration has found a radioactive zone in the middle of the formation up to 5m thick consisting of siltstones with abnormal values of zircon, rare earth elements like cerium and lanthanum, and thorium concentrations up to 2,337 ppm, which is the main source of radiation. Concentrations of radioactive and rare earth elements were highest in the middle area.

1. EXPLORATION OF RADIOACTIVE ELEMENTS IN THE LATE ORDOVICIAN
DUBAYDIB SANDSTONE FORMATION / SOUTH JORDAN
Abu qudaira, M.
Head of Exploration Division
Jordan Energy Resources Inc. (JERI), Amman, Jordan
ABSTRACT
Jordan was covered by airborne magnetic and spectrometric survey in 1980. The
airborne radiometric anomaly map indicated high anomaly related to the late
Ordovician Dubaydib sandstone Formation. Two exploration programs were carried out
by the Jordan Natural Resources Authority including uranium prospecting during 1987-
1996 and prospecting for zircon and rare earth elements during 1996-2009. The present
study is a follow up program taking in to account the results obtained from the previous
studies and the results of samples collected, recently by the Jordan Energy Resources
Inc. team. The results recorded a radioactive zone of 1.4 to 5m thick (average 3m). The
radioactive zone which is recognized by a yellowish green marker bed of about 0.75m
thick at the base consists of reddish brown siltstone overlain by greenish grey to violet
siltstone, pinkish dark grey siltstone and greenish grey siltstone. The study recorded
abnormal values of zircon mineral, some of rare earth elements (Ce, La, Lb and Hf) and
some of titanium minerals. A positive relationship between Zr, Ce, La, Y, & TiO2 was
recorded. The source of radiation was mainly due to thorium with concentration up to
2337ppm. The concentrations of radioactive and rare earth elements increase toward the
middle area (wadi Mezrab) which mean that the middle area was more affected by the
source of radioactive and rare earth elements. Five promising areas are delineated
within the Dubaydib Sandstone Formation for the futures studies.
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2. Introduction
The Dubaydib sandstone Formation covers an area of more than 900 sq km, located 350 kms South of
Amman and 100kms Northeast of Aqaba. This formation is extended, mainly, within four standard
subset topographic sheets of 1:50,000 scale (Jabal Ladghayn - Dubaydib (3148I & 3148II); Ad Disa,
3149III; Batn Al Ghul, 3149II and Jabal Al Batra, 3149IV). It extended as elongated belt trending NW-
SE from Jordan – Saudi border in the south toward the Northwest (Fig. 1). The name of Dubaydib
Formation is taken from Jabal Dubaydib in Dubaydib sheet area.
Previous Exploration Studies
After the results of airborne radiometric survey of Jordan published in 1980 (Phoenix corp.,
1980), several studies were carried out on the Dubaydib Formation in wadi Mezrab area by the Jordan
Natural Resources Authority (NRA) including prospecting for uranium in 1987-1996. Two geological
maps of Wadi Al Mezrab and Al Mudawwara areas at scale of 1:10,000 were produced (Masri, 1988a).
A positive relationship between Th, U and Zr was recorded from the radiometric and geological
evaluation of radioactive anomalies in the Ordovician Dubaydib Sandstone Formation (Perrin, 1989).
High concentration of zircon in the middle Dubaydib unit was recorded by Nimry et al. (1996), who
indicated that the REE are concentrated in the fine sand to silty sizes (<0.125mm). The study confirmed
thorium as the main source of radiation within the Dubaydib area.
The results of the these studies which indicated high concentrations of zircon mineral, rare earth
elements as Ce, La, and Y and some of titanium minerals encouraged the NRA to cry out an
exploration program for zircon and rare earth elements in wadi El Mezrab area. The exploration
program included reconnaissance phase and three phases 1, 2 and 3.
The reconnaissance phase included drilling and well logging of 10 boreholes (5-60m depth).
The study recorded a high gamma radiation in the zircon - bearing bed and moderate values of zircon
ranged from 0.28 to 1.71%. The zircon - bearing bed consisted of quartz and feldspar with cementing
material of calcite and iron oxides. (Madanat and Mehyar, 1997).
In phase I, the occurrences of zircon in Wadi Al Mezrab area were studied by Medanat and Mehyar,
(1999). Thirty nine (39) boreholes were drilled and seven (7) trenches were dug. The thickness of
zircon-bearing beds, which was determined by using gamma well logging, ranged between 1.5-5m with
an overburden thickness ranged between 0.0 and 18.7m. Chemical analysis (ICP) showed that the
average of zircon concentration ranged between 0.67 and 3.73% and the TiO2% was between 0.73 –
4.91%. The concentration of Ce and La was 499 – 2168ppm, and 242 – 1065ppm, respectively. It was
found that there is a positive relationship between the Zr, Ce, La, Y, and TiO2. Mineralogical studies of
2

3. the zircon – bearing beds indicated that quartz is the main constituent with small amounts of feldspar,
mica, rutile, brookite and monazite. Cementing materials consist of calcite and iron oxides.
Geochemical prospecting for minerals in Jabal Ladghayn – Dubaydib sheet map area was carried out
by Al Dalou et al., (2001). The geochemical analysis of the sampled area indicated that the
concentration of zirconium (Zr) was up to 2354ppm in rock samples On the other hand a bulk sample
of 500kg was sent to Egypt for mineral processing and concentration studies. The study which carried
out by the Geological survey of Egypt, (2003), showed that it is possible to separate zircon with 1.53%
and 80% purity.
In phase II, (Madanat and Shakkour, 2008), thirty seven (37) boreholes were drilled, 6 trenches and 8
pits were dug in four blocks within wadi Mezrab area. Chemical analysis (ICP) showed that the
average zircon concentration ranged between 0.38 – 4.42%.
In phase III, the studying of zircon and rare earth elements, taking in consideration, the
radioactive elements U & Th, in all the outcrops of the Dubaydib Sandstone Formation was carried out
by Abu Qudaira et al., (2009). The objective of this phase was to study all of the dubaydib sandstone
outcrops because the previous studies were concentrated mainly on Wadi Mezrab area. However the
project was terminated because the radioactive minerals became the responsibility of Jordan Atomic
Energy Commission (JAEC). This study was limited to geological studies, radiometric measurements
and collecting samples for chemical analysis.
Objective of the present study
The objective of the present study was to delineate potential areas within all the outcrops of
Dubaydib Sandstone Formation, for detailed study in the future. The data used in the present study
includes the data of the previous study carried out by Abu Qudaira et al., (2009) and the data collected
recently, by the exploration team of the Jordan Energy Resources Inc. (JERI).
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4. Figure 1: Location map of Dubaydib sandstone Formation (Coordinates in UTM, zone 36).
4

5. Stratigraphy
The Dubaydib Sandstone Formation is overlain by Mudawwara Sandstone and underlain by
Hiswa Sandstone formations (Table1). The formation (150-170m thick) has been divided into three
members by Masri (1988b); lower (DB1), middle (DB2) and upper (DB3).
Table1: The stratigraphic position of Dubaydib Sandstone Formation.
Formations Subdiv. Lithology Group Age
Mudawwara Sandstone Conularia Sandstone Silurian
DB3
Dubaydib Sandstone DB2 Sabellarifex Sandstone
Khuraym Ordovician
DB1
Hiswa Sandstone Graptolite Sandstone
The lower member (25m thick) starts with vertical sabellarifex and consists of alternating beds
of sandstone and siltstones. The sandstone consists of sheet like bed of fine grained micaceous
sandstone, grey weathered, buff to light brown, medium hard. According to Makhlouf, 1992, this
member could be separated into two facies; quartzarenite and silty shale facies. Each facies is
characterized by a particular association of sedimentary structures and textures.
The middle member comprises about 55m of fine grained cross-bedded sandstone, with
subordinate very fine silty sandstone, overlying channelled bases. This member was divided into two
facies; channelled sand and silty sand facies (Makhlouf, 1992). The channelled sand facies is either
surrounded by or interfingered with the silty sand facies. Large scale trough cross-bedding, ripples sole
marks, parallel lamination, low angle cross stratification, hummocky cross stratification, load cast and
locally trace fossils (Cruziana sp., sabellarifex sp., Rusophycus sp.) are all common.
The upper member (76m thick) consists of greenish silty shales and subordinate grayish fine
grained sandstone. The member could be separated into two facies greenish silty shale and hummocky
cross-stratified sandstone facies. Both facies are arranged in six coarsening-upward sequences the
thickness of individual sequences ranging from 7.6-22.5m.
Makhlouf (1992) considered a subtidal to lower intertidal marine environments for the lower
member with periods of current activity alternating with periods of slack water. The middle member
marks a high energy mid shelf zone (Powell. 1989) or a wave-dominated subtidal environment
(Makhlouf, 1992). Inner shelf conditions prevailed during the deposition of the upper member (Powell,
1989).
The radioactive zone occupies the lower part of the Middle Dubaydib Formation (DB2). The
sequence is well recognized by the yellowish green marker bed (Fig. 2). It consists of reddish brown
5

6. siltstone overlain by greenish grey to violet siltstone, pinkish dark grey siltstone to sandstone and
greenish grey siltstone. The pinkish dark grey siltstone to sandstone bed of about 40-75cm thick is the
main target bed for radioactive and rare earth elements. The total thickness of this sequence is ranging
between 1.5 and 5m with an average thickness of about 3m (Fig.3).
Figure 2: Radioactive zone located above the marker bed (yellowish green).
Figure3: Litho-log of the radioactive zone. (Gamma radiation was measured
by RS-125 spectrometer).
Chemical Analysis
The results of the chemical analysis, from the previous study (Abu Qudaira et al. 2009) and the
chemical analysis carried out by the team of JERI, are sown in table 2. These results indicate that the
thorium is the main source of radiation with concentration up to 2337ppm. Uranium concentration, on
the other hand, is up to 308ppm. The samples show high concentrations of Zr, La, Ce, Nb Hf and TiO2.
They show, also, a positive relationship between uranium and thorium and Th, Zr, La, Ce, Y and TiO2
(Fig. 4). A good correlation is shown between the concentrations of the following:
Th Vs U where R² = 0.8165, TiO2 Vs Th where R² = 0.9488, Zr Vs U, where R² = 0.8145 and Zr Vs
Th, where R² = 0.9622 (Fig. 5a-d). On the other hand bad correlation is shown between P2O5 and U.
(Fig.5e)
Table2: Previous and recent chemical analysis of samples collected from Dubaydib Sandstone areas.
(recent samples are the last 9 samples in the table).
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7. Du=Dubaydib sheet area, Di=Disi sheet area, and BG= Batn el Ghoul sheet area.
• Coordinates in UTM, zone 36N.
Mineralogical investigation
The main components of the radioactive zone, determined by the X-ray diffraction method (Abu
qudaira et al., 2009) were quartz as a major mineral with moderate amounts of feldspar and trace
minerals of kaolinite, zircon, muscovite, goethite and smectite. On the other hand, the minerals
identified in the thin section were Quartz as a major constituent and feldspar, mica and kaolinate as a
minor constituent, were the edges of quartz grains are mantled by iron oxides as a rim. Heavy minerals
occur as accessories and include: - zircon, Rutile, Brookite and Epidote. Cementing materials consists
of calcite and iron oxide (Madanat and Mihyar, 1999).
The Mineralogical and geochemical characteristics of rare earth elements bearing Ordovician
Sample Coordinates* U Th Zr La Ce Y Nb Hf V TiO2 P2O5 F2O3
No. ppm ppm ppm ppm ppm ppm ppm ppm ppm (%) (%) (%)
East North
ZrDu03 768293 3257945 99 575 16090 958 4183 200 97 N.A 170 5.89 0.40 05.22
ZrDu04 768187 3257887 102 621 19040 1137 4852 220 109 N.A 203 6.18 0.42 04.93
ZrDu06 768233 3266175 00.0 135 210 400 904 100 24 N.A 553 1.95 1.63 12.80
ZrDu07 771588 3252145 00.0 119 4375 271 1111 48 25 N.A 111 1.69 0.15 04.86
ZrDu08 771748 3251960 65.0 278 7806 533 2208 105 58 N.A 102 3.92 0.21 03.75
ZrDu09 772174 3250395 00.0 186 10300 618 2713 153 66 N.A 120 3.37 0.18 04.05
ZrDu10 768982 3265294 00.0 126 5493 286 1282 50 23 N.A 143 1.58 0.17 05.06
ZrDu11 768912 3265758 00.0 309 10530 701 3834 128 71 N.A 135 3.93 0.42 06.10
ZrDu12 772699 3249576 96.0 0 1293 121 487 47 13 N.A 251 0.96 0.47 15.30
ZrDi02 761201 3290602 00.0 236 137 249 560 290 0 N.A 675 3.71 0.19 3.63
ZrDi13 762113 3291322 00.0 93.0 3771 208 890 71 32 N.A 125 2.41 0.140 4.59
ZrBG2 768154 3267038 00.0 581 18110 1172 7100 280 104 N.A 178 6.22 0.32 4.87
ZrBG4 768151 3268391 00.0 122 3652 435 1977 115 31 N.A 175 2.09 1.29 8.97
ZrBG5 768271 3269071 64.0 144 4389 448 2248 131 45 N.A 519 2.58 0.75 12.5
MZ-A1 0768264 3257839 143.4 1409 34265 1847 3868 N.A 1604 1054 286 N.A 0.55 N.A
MZ-B2 0769104 3256891 237.0 2078 53629 2758 5417 N.A 2440 2113 618 N.A 0.69 N.A
MZ-B4 0770049 3256995 127.8 1439 30103 1960 3829 N.A 1597 973 456 N.A 1.08 N.A
DBO2-pit 0769491 3256208 53.7 638 16604 776 1711 N.A 732 385 225 N.A 0.32 N.A
DBO3-pit 0769602 3256157 42.0 433 12199 530 1434 N.A 501 267 253 N.A 0.37 N.A
DBO1 0769745 3256083 132 1540 30205 N.A N.A N.A N.A N.A 944 6.020 1.70 23.20*
DB-Th-1 0769124 3249415 <11 129 301 N.A N.A N.A N.A N.A 78 1.368 0.08 03.00*
DB-Th-2 0771071 3248417 <11 109 2950 N.A N.A N.A N.A N.A 73 0.880 0.11 02.60*
DB-1 0769100 3256888 308 2337 56640 N.A N.A N.A N.A N.A 560 0.108 0.89 6.763
sandstone from Dubaydib area were studied by Itamar et al., (1999). The study which was done on two
composite samples indicated that the primary rocks from which the sandstones were derived are acid
magmatic rocks, probably granites or microgranites. The presence of micas with some schistosity in
places, indicate that some metamorphic processes were took place. The study recorded zircon and
monazite as dominant heavy minerals. Rutile and anatase appear in small amount, and less amount of
7

8. ilmenite were also observed. The enrichment in REE, Th and U within the monazite is typical to the
“placer type”.
Correlation between U&Th concentrations
2500
Concentrations (ppm)
2000
1500
1000
500
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
U
(a) Samples
Th
Correlation between Th, Zr, La, Ce, Y & TiO2 concentrations
70000
Concentrations (ppm)
60000
50000
40000
30000
Th
20000
Zr
10000
La
0
Ce
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Y
Samples
(b) TiO2
Figure 4: Correlation charts between the concentrations (ppm) of a) U&Th and b) Th,
Zr, La, Ce, Y & TiO2.
8

9. Th Concentration (ppm)
Th Vs U
3000
2500 R2 = 0.8165
2000
Th
1500
Linear (Th)
1000
500
0
0 50 100 150 200 250 300 350
U Concentration (ppm)
(a)
TiO2 Concentration (ppm)
TiO2 Vs Th
70000
60000 R2 = 0.9488
50000
40000 TiO2
30000 Linear (TiO2)
20000
10000
0
0 100 200 300 400 500 600 700
Th Concentration (ppm)
(b)
Zr Concentration (ppm)
Zr Vs Th
60000
50000
40000 R2 = 0.9622
Zr
30000
Linear (Zr)
20000
10000
0
0 500 1000 1500 2000 2500
Th Concentration (ppm)
(c)
Zr Concentration (ppm)
Zr Vs U
70000
60000 R2 = 0.8145
50000
40000 Zr
30000 Linear (Zr)
20000
10000
0
0 50 100 150 200 250 300 350
U Concentration )ppm)
(d)
9

10. P2O5 Concentration (ppm)
P2O5 Vs Th
18000
16000
14000
12000
10000 R2 = 0.0565 P2O5
8000 Linear (P2O5)
6000
4000
2000
0
0 500 1000 1500 2000 2500
(e) Th Concentration (ppm)
Figure 5: Correlation charts between a) Th Vs U, b) TiO 2 Vs Th, c) Zr Vs Th, d) Zr Vs U, and
e) P2O5 Vs U.
Conclusions
• The studies carried out on the Late Ordovician Dubaydib Sandstone Formation were started as a
result of radiometric survey carried out on all Jordan in 1980. Most of the studies were concentrated
on the Dubaydib area, (Wadi El Mezrab).
• A radioactive zone of 1.5 – 5m thick (average is 3m) was determined where the main source of
radiation is thorium. The thorium concentration was up to 2337ppm. Thorium and uranium were
found within the Monazite structure.
• Depending on the chemical analyses used in this study, the following concentrations were
calculated which are close to the previous results:
Th concentration ranges from 0 - 2337ppm (average = 593ppm).
U concentration ranges from 0 - 308ppm (average = 70ppm).
Zr concentration ranges from 0.014 – 5.66 % (average=1.49%).
La concentration ranges from 0.012 – 0.28% (average=0.08%).
Ce concentration ranges from 0.49 – 0.71% (average=0.27%).
Y concentration ranges from 0.005 – 0.029% (average=0.014%).
Nb concentration ranges from 0.0 – 0.24% (average=0.04%).
TiO2 concentration ranges from 0.108 – 6.22% (average=3.05%).
• A positive relationship between uranium and thorium and Th, Zr, La, Ce, Y and TiO2 was recorded.
A good correlation was recorded between the concentrations of the following:
Th Vs U where R² = 0.8165., TiO2 Vs Th where R² = 0.9488.
Zr Vs U, where R² = 0.8145, Zr Vs Th, where R² = 0.9622.
• Bad correlation is shown between P2O5 and U which confirmed the monazite mineral as the source
of uranium.
10

11. • An abnormal concentration of Zr, La, Ce, Hf, Lb and TiO2 were recorded which make these
elements viable for investment.
• Mineralogical studies indicated that quartz is the main constituent of the radioactive beds, with
small amounts of feldspar and heavy minerals (zircon, rutile, brookite, epidote and monazite).
The cementing material is calcite and iron oxides.
• The concentrations of radioactive and rare earth elements increase toward the middle area
(wadi Mezrab) which mean that the middle area was more affected by the source of radioactive
and rare earth elements.
• Five promising areas are delineated within the Dubaydib Sandstone Formation for the futures
studies. These areas are closed to the surface with low overburden thickness (Fig. 6).
11

12. Figure 5: The Delineated promising areas within Dubaydib Sandstone Formation.
12

13. REFERENCES
Abu Qudaira, M., Abu Saad, L.; Masarwa, R.: and Sadeq, A., 2009. Occurrences of zircon sand and
rare earth element in the Ordovician Dubaydib Sandstone Formation, South Jordan. NRA,
Amman, Jordan.
Al-Dalou, A., Al Sbaie, I., and Mahmod, S., 2001. Geochemical prospecting for minerals, Jabal
Ladghayn Dubaydib sheet area. Geochemistry Division, NRA, Amman, Jordan.
Geological survey of Egypt, 2003. Technological study for Economic minerals separated from
sample bearing zircon ore (Dubaydib sandstone, south Jordan), NRA, Amman, Jordan.
Itamar, A. Segal, M., Madanat, M., Mehyar, N., Bar-Matthews, M., and Shirav (Schwartz), M., 1999.
Mineralogical and geochemical charactestics of rare earth elements bearing Ordovician's
sandstone from Jordan. NRA, Amman, Jordan.
Madanat, M. and Mehyar, N., 1997. Occurrences of Zircon sand in Wadi Al – Mezrab area, NRA,
Amman, Jordan. (In Arabic).
Madanat, M. and Mehyar, N., 1999. Occurrences of Zircon in Wadi Al – Mezrab area, NRA,
Amman, Jordan.
Madanat, M. and shakkour, O., 2008. Occurrences of zircon in Wadi Al – Mezrab area / south
Jordan. Exploration Studies Division. NRA, Amman, Jordan.
Makhlouf, I., 1992. Depositional environments and facies in the Dubaydib and Tubeiliyat
sandstone, southern desert, Jordan. Subsurface geology bull. 3, NRA, 32p.
Masri, A., 1988a. Geological map of Wadi Al-Mezrab, scale1:10,000, NRA, Amman, Jordan
Masri, A., 1988b. The geology of Wadi Al- Mezrab, Int. report, NRA.
Nimry, F., Zu'bi, H.; Dana, J. and Abu Bakur, A., 1996. Zircon and Rare Earth Elements in
Dubaydib area, Geochemistry Division NRA, Amman, Jordan (in Arabic).
Perrin, C., 1989, Radiometric and geologic evaluation of Radioactive Anomalies in the Ordovician
(Sabllarifex), beds. Rep., 89-40.
Phoenix Corp., 1980. A comprehensive airborne magnetic relation survey of the H.K.J., NRA,
Amman, Jordan.
Powell, J., H., 1989, Stratigraphy and sedimentation of the phanerozoic rocks in central and south
Jordan; Part A, Ram and Khreim group. Geological mapping bulletin11, NRA, Amman, Jordan.
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