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JJEES Volume 4 (Special Publication, Number 2), Jan. 2011
ISSN 1995-6681
Pages 35- 45
Jordan Journal of Earth and Environmental Sciences
Review of Uranium in the Jordanian Phosphorites: Distribution,
Genesis and Industry
Abdulkader M. Abed*
Present address: Researcher, Deanship of Scientific Research
Jordan University of Science and Technology, Irbid
Abstract
Phosphorites are well-known, world wide, to accommodate a substantial amount of U relative to other sedimentary rocks.
This is due to a great extent to the crystal structure of apatite (carbonate flour apatite, francolite) where U substitutes Ca.
Phosphorites form in shallow marine environments through the accumulation of planktonic fossils debris on the sea floor in
areas characterized by upwelling currents. Once the organic-rich sediments are buried below the sea floor and the organic
matter is decomposed, PO4 is released to the interstitial solutions. These PO4-rich solutions either precipitate phosphorites
directly (authigenic) or the solutions react with pre existing sediments and transform them to phosphorites (early
diagenentic). The Jordanian deposits are dominantly of the former type. Consequently, phosphorites are also well known to
be associated with high percentage of organic matter which makes them a good source rock for petroleum.
In Jordan, phosphorites are wide spread from its extreme NW to the SE. Uranium contents are not the same in each locality.
It is not also the same in each bed in the same locality. In Al-Kora Basin, NW Jordan, U ranges between 60-379 ppm (parts
per million or g/ton) with an average of 153 ppm. In Ruseifa, just east of Amman, the range is 132-195 ppm and average of
123 ppm. Central Jordan phosphorites (Al-Abiad and Al-Hasa) have a lower U %. The range is 34-190 ppm with an average
of 105 ppm. Eshidiyya Basin has a much less U concentration. The range is 7-125 ppm with an average of 70 ppm.
However, a recent work on the uppermost phosphorite horizon, the A0, in Eshidiyya Basin proved the presence of a 3 m
thick bed with 242 ppm U. Furthermore, certain phosphorite horizons are known to have much more than the average U in
that locality; e.g. in Al-Kora Basin, the average U is 153 ppm while certain horizons have up to 379 ppm U, the uppermost
bed in Ruseifa has up to 195 ppm while the average is 123 ppm, and in Eshidiyya the A0 has 242 ppm while the average of
the lower horizon (A1-3) average is 70 ppm. Obviously, if the U is to be extracted from the phosphorite, the horizons with
higher concentrations of U should be explored and used.
Uranium sticks to francolite in its behavior from precipitation in the marine environment, through mining and beneficiation,
and the fertilizer industry. 1) There is a significant high correlation coefficient between CaO and P2O5 in the hundreds of
samples analyzed. 2) Fines (clays) produced when washing the ore have very little U and consequently, washing water for
the last 45 years has not contaminated groundwater with U in central Jordan. 3) Uranium is concentrated in the phosphoric
acid then into diammonium phosphate (DAP) in the fertilizer industry and not in the phosphogypsum.
© 2012 Jordan Journal of Earth and Environmental Sciences. All rights reserved
Keywords: Phosphorite; Upper Cretaceous; Uranium; Francolite; Jordan; Diammonium Phosphate; Phosphogypsum .
* Corresponding author. e-mail: aabed@ju.edu.jo.
1. Introduction
Phosphorites are the carrier of uranium, thus the study
of them is a prerequisite to the study of U. Phosphorites
are widespread in Jordan and cover a relatively large area
of the country from the extreme northwest to its south.
Low and high grade phosphorites are supposed to have
been deposited throughout the country, but subsequent
uplift and erosion, from the Oligocene onwards, had
removed it from various parts of the country; e.g. Ajlun
dome the western parts of the western mountain range, and
the extreme south (Bender, 1974; Powell, 1989, Abed,
2000). Furthermore, high grade phosphorites are also
present in the subsurface of the eastern desert of Jordan;
e.g. Zgaimat Al-Hasat (Abed and Amireh, 1999).
High grade phosphorites were discovered in Jordan in
1908 during the construction of the Hijaz Railway. In
1938, small scale mining from Ruseifa started and was
exported by mules through Haifa. The Jordan Phosphate
Mines Company (JPMC) commenced its work by 1953 in
Ruseifa, 1965 in Al-Hasa, 1979 in Al-Abiad, and 1988 in
Eshidiyya (Abed, 2000). Ruseifa mines were closed in
1988 despite the fact that there are several tens of millions
of high grade phosphorites south of Amman-Zarqa
Highway (Zarqa B area) (Abed, 1989). Central Jordan
© 2012 Jordan Journal of Earth and Environmental Sciences . All rights reserved - Volume 4, (Special Publication, Number 2)(ISSN 1995-6681)
36
phosphorites (Al-Hasa and Al-Abiad) are near depletion);
consequently, Eshidiyya is going to be the centre for
phosphorite mining and industry. However, several
hundred millions of high grade phosphorites are present in
Al-Kora Basin NW Jordan (Mikbel and Abed, 1985; Abed
and Al-Agha, 1989), likewise, huge, but not estimated,
subsurface deposits in the SE desert continuing into Saudi
Arabia are present (Abed and Amireh, 1999). In short,
there seems to be no shortage of high grade phosphorites
in Jordan even for the distant future.
On the other hand, uranium is well known to be
several folds enriched in phosphorites compared with other
sedimentary rocks such as sandstones, carbonates and
shales. Average U in phosphorite is 120 ppm compared
with 3.5, 0.5 and 2.2 ppm in shale, sandstone and
carbonate respectively; an enrichment factor of around 30
relative to shale (Altschuler, 1980; Slansky, 1986;
McArthur et al., 1987; Krauskopf and Bird, 1995).This is
basically due to the nature of the crystal structure of
francolite (carbonate flour apatite) where U is substituting
for calcium, both having a close radius (Ca+2= 0.99Å and
U= 0.97Å (e.g. Nathan, 1984; Mcclellan and Van
Kauwenberg, 1990). The enrichment of U in phosphorites
may also be due to the association of the latter with
abundant organic matter in the depositional environment
of the phosphorites (Barnett, 1990). Uranium, in the
Jordanian phosphorite, was studied by Coopens et al.,
(1977), Khalid and Abed (1982), Abed and Khalid (1985)
and Sadaqah et al., 2005 amongst others).
The aim of this paper is to discuss a) the distribution of
U in the various localities and the phosphorite horizons
within each locality; b) the genesis of phosphorite
formations in Jordan; and c) the behavior of U throughout
the processes of mining, upgrading and fertilizers industry.
2. GEOLOGICAL SETTING
The phosphorites of Jordan form part of the
Cretaceous-Eocene phosphorite episode which deposited
one of the most extensive deposits in the world in the
Eastern Mediterranean (Saudi Arabia, Iraq, Syria, Jordan
and Palestine) and North Africa (Egypt, Tunisia, Algeria,
Morocco, Mauritania, Senegal, …), and parts of the
Caribbean and NE S. America. It is second to the Miocene
North American episode (Sheldon 1981; Riggs, et al.,
1985; Notholt et al. 1989; Abed, 1994; Follmi 1996).
The phosphorites of Jordan are present within Al-Hisa
Phosphorite Formation (AHP). Fig. 1 shows the location of
high grade phosphorites in Jordan. The age of the AHP is
most probably early Maastrichtian, Uppermost Cretaceous
(Quennell, 1951; Hamam, 1977; Cappetta et al., 1996). In
general, the AHP consists of phosphorites, bedded chert,
limestones, oyster buildups, organic-rich marl (oil shale)
and other rock types (Powell, 1989; Abed, 2000).
However, the lithology and thickness of the AHP are
variable from one locality to the other. The total thickness
of the AHP is around 10 m in NW Jordan, 30 m in
Ruseifa, 40-60 m in central Jordan, 10-17 m in Eshidiyya
and 5-6 m in Zgaimat Al-Hasat in the SE desert ((Powell,
1989; Abed, 2000).
Fig. 1 Location map of the grade phosphorite deposits in Jordan.
The AHP consists of three formal members, from older
to younger Sulatani, Bahiyya and Qatrana. The three
members are well displayed throughout central Jordan
where the terminology was first used by El-Hiyari (1985)
(Table 1). In central Jordan, the Sultani Member consists
of alternating limestones, bedded chert and minor
phosphorites. The Bahiyya Member consists of oyster
banks or buildups up 30 m in thickness that are made of
oyster fragment in clinoforms dipping general to the SE
(Abed and Sadaqah, 1998). The Qatrana Member is the
host of the high grade phosphorites. The grade
phosphorites are friable with little calcareous cement. They
are present as lenses (small basins) with a diameter
ranging up to few kilometers and a thickness up 13 m.
Table 1. Nomenclature of the Upper Cretaceous rock units in
Jordan (Al-Hiyari, 1985)
In Eshidiyya Basin, the three formal members are
present only in the northern parts of the basin. The
Bahiyya coquina thins gradually towards the SE until it
disappears completely. The Sultani Member or the lower
© 2012 Jordan Journal of Earth and Environmental Sciences . All rights reserved - Volume 4, (Special Publication, Number 2)(ISSN 1995-6681) 37
member is hosting the main (high) grade phosphorite
deposits. It is divided by the miners into three producing
phosphate horizons from top to bottom; A1, A2 and A3,
separated by non phosphorite strata like; chert, porcelanite,
and minor beds of marl, limestone and dolomite.
(Sofremines, 1987; Abed et al., 2007). The A3, at the base,
is rich in quartz sand, while A2 is a friable, high grade
phosphorite. The A1 is a low grade indurated by calcite
cement (Fig. 2). The Qatrana Member or the upper
member is designated A0 and consists of up to 3 m of
friable high grade phosphorite in the north thinning to the
SE to few centimeters only.
Fig. 2 A columnar section describing the lithology of Eshidiyya phosphorites. A detailed section , right, shows the lithology of the A0
deposits in northern Eshidiyya.
Fig. 3 is a columnar section in central Jordan. The SE
desert deposits were discovered by Abed and Amireh
(1999). They are deep seated in the subsurface, but crop
out as windows at the cores of anticlines such as that of
Zgaimat Al-Hasat. Total thickness is 5-6 m consisting of
friable phosphorites with same quartz sand increasing to
the SE (Fig. 4). The age, most probably Turonian, seems
older than other phosphorites of Jordan (Khalifa and Abed,
2011).
Fig. 3 (left) Generalized lithological section in central Jordan.
Fig. 4 (right) Detailed columnar section of the Ajlun Group and the phosphorites of the SE desert at Zgaimat Al-Hasat (Khalifa and Abed,
2011). For legend, see Fig. 2.
© 2012 Jordan Journal of Earth and Environmental Sciences . All rights reserved - Volume 4, (Special Publication, Number 2)(ISSN 1995-6681)
38
The Ruseifa mines were closed in 1988, however, the
deposits consists of four phosphorite horizons designated
from bottom A1, A2, A3, and A4, separated by limestone,
trace fossils and some chert (Fig. 5). Al-Kora deposits,
NW Jordan, were discovered by Mikbel and Abed (1985)
with several million tons of grade phosphorites. The
deposits are up to 10 m thick, the lower part consists of
alternating chert and phosphorite caped by about 3 m thick
high grade, friable phosphorite horizon rich in organic
matter (Abed and Al-Agha, 1989). Fig. 6 shows the
lithology near the village of Tobna. These deposits have
not been mined yet.
Fig. 5 (left) columnar section describing the phosphorites at Ruseifa Basin.
Fig. 6 (right) Columnar section describing the phosphorites at Tobna, Al-Kora Basin, NW Jordan. For legend, see Fig. 2 .
3. Results and Discussion
3.1. Petrography and Mineralogy
The phosphorites of Jordan are granular in nature with
subordinate pristine (primary or not reworked) especially
in NW Jordan deposits. Grain types are phosphate
intraclasts, peloids, coprolites and skeletal fragments (bone
and teeth). The former two types are due mainly to
reworking of originally precipitated phosphate material, or
may partially be due to the nature of deposition between
the pore spaces of pre existing sediments (Riggs, 1979,
1980; Burnett, 1990; Abed and Fakhouri, 1996; Abed et
al., 2007 amongst many others).
Phosphate particles or grains, in marine phosphorites,
consist of the mineral carbonate flour apatite (francolite), a
variety of the mineral apatite. The phosphorites of Jordan
have the following chemical formula of francolite [Ca 9.86
Mg .005 Na .14] [PO4 4.93 CO3 1.07 F 2.06] (Abed and
Fakhouri, 1996). The crystal structure of francolite is
rather open, thus enhancing substitution (e.g. McClellan
and Van Kauwenberg, 1990). Uranium is one of many
elements that substitutes for Ca. Consequently, U is
present within the crystal structure of francolite and
behaves more similar to Ca than to P, simply because the
ionic radii are very close to each other. To shed more light
on this relationship, U ppm is correlated with each of
CaO%, P2O5%, U/ P2O5 and U/CaO in 184 samples from
the Jordanian phosphorites (Fig. 7). It is clear that a better
correlation is present between U and Ca than between U
and P, meaning that U is not only present within the
structure of francolite but it occupies same positions of Ca
in that structure.
Fig. 7 Correlation between U and A) P2O5%, B) CaO%, C)
U/P2O5 ratio, and D) U/CaO ratio. Solid line is the best fit while
dotted lines are for the 95% confidence. Number of samples is
184.
The yellowish-greenish U minerals found on the
surface of joints and fractures are due to leaching by
groundwater of the original U; i.e. secondary in origin.
Consequently, this type occurrence is very limited in
abundance, and thus, of minor importance and of no
economic value for U exploration.
© 2012 Jordan Journal of Earth and Environmental Sciences . All rights reserved - Volume 4, (Special Publication, Number 2)(ISSN 1995-6681) 39
3.2. Distribution of Uranium
In this title, the distribution of U in the various
localities in Jordan is discussed based on data acquired by
the author, his coworkers and students since 1980.
3.2.1. Eshidiyya Deposits
Phosphorites are present in two members, the lower
member (A1, A2 and A3 horizons) who accommodates the
main phosphorite reserves, and the upper member (A0
horizon) with limited reserves (Fig. 2). Tables 2 and 3
display the contents of U in both upper and lower members
respectively.
The U average of 60 samples analyzed from the lower
member is 51 ppm with a range 1 -175 ppm. If the samples
with less than 11 % P2O5 % are removed, because they are
not typical phosphorites, then the average U will be 70
ppm. The higher U concentrations up to 175 ppm can be
found in the calcareous, high grade A2 horizon. The A3
has the lowest U content, partially, because of the high
dilution with silica sand which can be present up to 50 %
in certain samples. The A1 is slightly higher than the A3
(Khaled and Abed, 1982). Upgrading the lower member
will certainly enhance the contents of U in these
phosphorites.
Table 2.Uranium, P2O5 and CaO contents and other ratios in the lower phosphorite member in Eshidiyya Basin (Khaled and Abed, 1982;
Abed and Khaled, 1985).
U ppm
P2O5% CaO%
U/
P2O5 CaO/
P2O5 U/
CaO
Uppm
P2O5
% CaO%
U/
P2O5 CaO/
P2O5 U/
CaO
1 45 23.96 41.23 1.88 1.72 1.09 31 63 5.83 39.53 10.81 6.78 1.59
2 96 21.93 37 3.14 1.69 2.59 32 5 9.88 32.05 0.51 3.24 0.16
3 143 33.13 53.12 4.23 1.60 2.69 33 5 10.27 39.35 0.49 3.83 0.13
4 146 23.98 53.3 4.43 2.22 2.74 34 5 6.55 9.17 0.76 1.40 0.55
5 44 27.22 40.4 1.62 1.48 1.09 35 50 30.88 48.04 1.62 1.56 1.04
6 44 23.16 40.78 1.75 1.76 1.08 36 35 31.74 45.96 1.10 1.45 0.76
7 45 25.68 39.04 1.75 1.52 1.15 37 50 22 38.47 2.27 1.75 1.30
8 45 22.18 36.49 2.02 1.65 1.23 38 75 32.84 49.08 2.28 1.49 1.53
9 44 27.63 44.1 1.39 1.60 1.00 39 85 33.96 49.94 2.50 1.47 1.70
10 141 32.63 48.8 4.32 1.50 2.89 40 100 33.76 49.93 2.96 1.48 2.00
11 111 25.33 44.3 4.38 1.75 2.51 41 88 26.6 43.65 3.31 1.64 2.02
12 72 19.99 42.91 3.6 2.15 1.68 42 85 18.27 27.87 4.65 1.53 3.05
13 45 26.14 42.06 1.72 1.61 1.07 43 100 20.7 33.79 4.83 1.63 2.96
14 44 33.82 30.25 1.30 0.89 1.45 44 46 28.25 50.63 1.63 1.79 0.91
15 18 7.45 24.94 2.42 3.35 0.72 45 45 20.05 44.57 2.24 2.22 1.01
16 7 4.1 7.26 1.71 1.77 0.96 46 63 22.92 40.46 2.75 1.77 1.56
17 16 7.7 25.96 2.08 3.37 0.62 47 8 33.13 44.52 0.24 1.34 0.18
18 29 24.15 37.82 1.20 1.57 0.77 48 75 29.91 48.33 2.51 1.62 1.55
19 43 35.91 55.09 1.20 1.53 0.78 49 125 29.7 39.63 4.21 1.33 3.15
20 30 24.21 38.22 1.24 1.58 0.78 50 1 0.83 2.82 1.20 3.40 0.35
21 35 27.78 43.86 1.26 1.58 0.80 51 2 10.89 18.19 0.18 1.67 0.11
22 51 33.66 54.18 1.52 1.61 0.94 52 1 1.5 3.14 0.67 2.09 0.32
23 69 30.34 47.19 2.27 1.56 1.46 53 5 11.38 17.59 0.44 1.55 0.28
24 34 10.68 16.8 3.18 1.57 2.02 54 2 8.8 18.11 0.23 2.06 0.11
25 125 26.71 55.35 4.68 2.07 2.26 55 25 10.1 16.93 2.48 1.68 1.48
26 89 17.07 54.58 5.21 3.20 1.63 65 3 13 20.36 0.23 1.57 0.15
27 175 27.32 52.24 6.41 1.91 3.35 57 1 11.07 16.56 0.09 1.50 0.06
28 34 23 40.84 1.48 1.78 0.83 58 1 7.78 30.47 0.13 3.92 0.03
29 46 33.01 50.55 1.39 1.53 0.91 59 1 2 22.79 0.50 11.40 0.04
30 34 23.94 36.28 1.42 1.52 0.94 60 1 1.66 25.56 0.60 15.40 0.04
Av 51 20.83 36.71 2.24 1.76 1.39 Av. of >11% P2O5 = 70 ppm
On the other hand, the upper phosphorite member (A0)
is much more enriched in U. Table 3 shows the analysis of
28 samples of the A0 with an average U of 133 ppm and a
range of 5-242 ppm. If the samples of less than 10% P2O5
% are removed, then the average U becomes 172 ppm and
the range 40-242 ppm, The data clearly indicates that U is
more than twice that of the lower member (Abed and
Sadaqah, 2011 in press). The A0 consists of two
phosphorite beds up to 3 m thick. The phosphorite beds are
calcareous with slight calcite cement, ammonites and trace
© 2012 Jordan Journal of Earth and Environmental Sciences . All rights reserved - Volume 4, (Special Publication, Number 2)(ISSN 1995-6681)
40
fossils. The A0 overlies the coquina member (middle
member) with subaerial unconformity. Abed and Sadaqah
(2011 in press ) concluded that the U enrichment is, at
least partially, due to slight leaching of the carbonates and
phosphorites at the unconformity. That is why the lower
bed of the A0 has more U compared with the upper bed
away from the unconformity.
Table 3.Uranium, P2O5 and CaO contents and other ratios in the upper phosphorite member (A0) in Eshidiyya Basin (Abed and Sadaqah,
2011 in press).
3.2.2. Central Jordan Deposits
Central Jordan phosphorites are represented by Al-Hasa
and Al-Abiad deposits and their surroundings. The
deposits are calcareous, granular, and slightly cemented by
calcite and are present in single isolated lenses. Several
hundred million tons or high grade phosphorites were
mined since 1965, and consequently these deposits are
near depletion. Table 4 shows the chemical results of 34
samples with an average of 105 ppm and a range 60-168
ppm (Abed and Khaled, 1985; Sadaqah et al., 2005; Abed
et al., 2008). However, there are no much deposits for
future U industry.
Table 4.Uranium, P2O5 and CaO contents and other ratios in central Jordan phosphorites, Al-Abiad and Al-Hasa (Abed and Khaled, 1985;
Abed et al., 2008).
© 2011 Jordan Journal of Earth and Environmental Sciences . All rights reserved - Volume 4, (Special Publication, Number 2)(ISSN 1995-6681)
41
However, grade phosphorites are present west of
Dhiban, near the village of Shgaig. The area is populated
and the deposits have not been mentioned by JPMC or
other workers (Abed and Khaled, 1985). Reserves are not
estimated and the U contents of 14 samples is 79 ppm with
a range of 4-118 ppm (Table 5)
Table 5. Uranium, P2O5 and CaO contents and other ratios in the
phosphorites of the Mujib Area (Abed and Khaled, 1985).
U
ppm P2O5% CaO%
U/
P2O5 CaO/
P2O5 U/
CaO
1 92 22.94 52.41 4.01 2.28 1.76
2 22 16.85 44.7 1.31 2.65 0.49
3 15 14.8 47.29 1.01 3.20 0.32
4 4 16.81 47.4 0.24 2.82 0.08
5 103 13.16 51.13 7.83 3.89 2.01
6 110 18.95 52.47 5.80 2.77 2.10
7 110 23.18 53.79 4.75 2.32 2.04
8 116 29.72 51.8 3.90 1.74 2.24
9 78 26.81 50.24 2.91 1.87 1.55
10 85 23.69 52.18 3.59 2.20 1.63
11 118 30.1 51.3 3.92 1.70 2.30
12 48 17.94 54.64 2.68 3.05 0.88
13 91 24.85 57.31 3.66 2.31 1.59
14 111 22.92 50.17 4.84 2.19 2.21
Av. 79 21.62 51.20 3.60 2.37 1.54
3.2.3. Ruseifa Deposits.
During 1988, Ruseifa mines were closed and the
remaining deposits south of the Amman-Zarqa highway
are becoming more and more urbanized. Thus, the
following lines are of historical value only. The Ruseifa
phosphorites consist of four horizons (A1, A2, A3, and A4
topmost) separated by carbonates and chert beds (Fig. 5).
Table 6 shows the analysis of 17 samples with an average
U of 123 ppm and a range of 57-184. Uranium content
increases upwards and the A4 horizon have the highest
content of more than 180 ppm (Abed and Khaled, 1985).
Table 6. Uranium, P2O5 and CaO contents and other ratios in the
phosphorites of Ruseifa (Abed and Khaled, 1985).
U
ppm P2O5% CaO% U/
P2O5 CaO/
P2O5 U/
CaO
1 123 17.25 52.61 7.02 3.05 2.34
2 121 26.66 55.26 4.55 2.07 2.19
3 113 13.26 52.7 8.52 3.97 2.14
4 56 24.67 42.58 2.27 1.73 1.32
5 86 24.59 42.97 3.5 1.75 2.00
6 57 25.31 43.62 2.25 1.72 1.31
7 183 29.79 52.65 6.11 1.77 3.48
8 184 28.94 50.33 6.53 1.74 3.66
9 127 26.31 46.71 4.82 1.78 2.72
10 73 21.69 43.68 3.37 2.01 1.67
11 119 20.96 53.17 5.68 2.54 2.24
12 117 17.31 49.45 6.76 2.86 2.37
13 161 30.5 53.8 5.28 1.76 2.99
14 162 31.11 53.75 5.21 1.73 3.01
15 181 21.75 53.82 8.32 2.47 3.36
16 117 16.54 54.2 7.07 3.28 2.16
17 117 17.93 52.1 6.53 2.91 2.25
Av. 123 23.21 50.20 5.52 2.16 2.46
3.2.4. Al-Kora Deposits, NW Jordan
The NW Jordan phosphorites are promising future
deposits for phosphorites and uranium. There are, at least,
several hundred million tons of high grade phosphorites
with high U content relative to other deposits discussed
earlier. However, the high population (many villages and
towns) and the green nature of the area (forests and
agriculture) might have been behind the decision not to
mine the deposits. Also, the deposits are present within a
folded belt which makes open pit mining rather difficult if
not impossible in certain localities (Mikbel and Abed
1985).
Table 7 shows the analysis of18 samples with an
average of 153 ppm U and a range of 59-379 ppm U (Abed
and Khaled, 1985; Sadaqah, 2000, Sadaqah et al., 2005).
The highest U content is around 6 times more than that of
Eshidiyya and might be of economic nature if extracted as
a byproduct through the fertilizers industry. Detailed field
and laboratory work can pinpoint the localities with the
high U content.
Table 7.Uranium, P2O5 and CaO contents and other ratios in the
phosphorites of Al-Kora Basin, NW Jordan.(Abed and Khaled,
1985; Sadaqah et al., 2005).
U
ppm P2O5% CaO%
U/
P2O5 CaO/
P2O5 U/
CaO
1 88 24.09 40.52 3.65 1.68 2.17
2 117 30.23 44.01 3.87 1.46 2.66
3 186 32.7 52.4 5.69 1.60 3.55
4 129 18 53.79 7.16 2.99 2.40
5 120 14.22 50.44 8.44 3.55 2.38
6 132 30.18 46.62 4.37 1.54 2.83
7 127 24.37 54.9 5.21 2.25 2.31
8 81 21.08 33.18 3.84 1.57 2.44
9 75 31.5 52.4 2.38 1.66 1.43
10 238 34.16 52.98 6.97 1.55 4.49
11 88 26.25 52.78 3.35 2.01 1.67
12 89 24.05 53.09 3.70 2.21 1.68
13 301 20.92 50.06 14.39 2.39 6.01
14 343 18.95 51.95 18.10 2.74 6.60
15 109 24.06 52.52 4.53 2.18 2.08
16 59 10.13 52.39 5.82 5.17 1.13
17 379 27.75 53.08 13.66 1.91 7.14
18 92 22 52.23 4.18 2.37 1.76
Av 153 24.15 49.96 6.63 2.07 3.06
3.2.5. Area Comparison
Absolute U content might not be the best way of
comparing its abundance in the various localities. For this
reason, the U/P2O5 ratio is used, meaning the amount of U
in ppm present for each 1% P2O5. The average U/P2O5
ratio for the samples in each locality (not the ratio of
averages) is shown in Table 8. It is clear from Table 8 that
the ratio increases northwards. It is 2.24 in Eshidiyya; i.e.
there is 2.24 ppm U in Eshidiyya deposits for each 1%
P2O5. It increases to 6.63 in NW Jordan, which clearly
shows that the NW Jordan phosphorites are three times
© 2011 Jordan Journal of Earth and Environmental Sciences . All rights reserved - Volume 4, (Special Publication, Number 2)(ISSN 1995-6681)
42
more enriched in U compared with Eshidiyya. The other
localities are intermediate between Eshidiyya and NW
Jordan. The possible reasons for this northwards increasing
trend are discussed further below.
Table 8The U/P2O5 sample averages in the phosphorite deposits of
Jordan, n = number of samples averaged.
U
ppm P2O5
% CaO
% U/
P2O5 n
Eshidiyya 51 20.83 36.7
1 2.24 60
Central
Jordan 105 27.46 48.5
2 3.81 44
Mujib 79 21.62 51.2 3.6 13
Ruseifa 123 23.21 50.2 5.52 16
NW Jordan 153 24.15 49.9
6 6.63 18
4. Behavior of U During Mining and Upgrading.
Mining and upgrading are the not discussed here
because they are not the subject of this paper. However,
mining and upgrading involve the removal of the
overburden, obtaining the phosphorite ore, crushing the
ore to liberate the suitable grain size, sieving to get a
roughly sand-size product, washing with fresh water to get
red of the fines especially clays, and finally drying.
Samples from all these stages were analyzed for their U
and other elements and the following conclusion was
reached (Al-Huwaiti et al., 2005; Abed et al., 2008).
Uranium behaves similar to the behavior of P and Ca (Fig.
8a); i.e. U stays fixed in the crystal structure of francolite,
as discussed in the mineralogy section.
Environmentally, the discharged washing water has not
contaminated the groundwater in Al-Hasa and Al-Abiad
mines area despite the fact that the washing process has
been ongoing since 1965 and 1979 respectively.
Groundwater samples from wells and springs in central
Jordan have a U content less than 2 ppb (parts per billion) (
Jiries et al., 2004; Abed et al., 2008). See Fig.8b.
Fig. 8 shows the behavior of U during mining, crushing, sieving
and washing (8a upper) and 8b shows the concentration in ppb in
the groundwater in central Jordan.
5. Behavior of U in the Fertilizers Industry.
In the fertilizers industry, the upgraded phosphorite ore
is reacted with sulphuric acid (H2SO4) to produce
phosphoric acid (H3PO4) and phosphogypsum. The crystal
structure of francolite is destroyed through this reaction, its
PO4 forms phosphoric acid, and the Ca of francolite forms
the phosphogypsum. Analysis of the two products, the
acid, and gypsum, clearly shows that U follows the PO4
group and is concentrated in the phosphoric acid. The
phosphogypsum has no more than 2 ppm U. The
phosphoric acid is then transferred to the fertilizer,
diammonium phosphate (DAP), and U is found to be
concentrated in the. DAP. Through these reactions, U is
found to be concentrated in the phosphoric acid and the
DAP by a factor of 1.5 (Fig. 9). For more details, see Abed
et al., (2008).
Fig. 9 Behavior of U in the fertilizers industry. Note that the U
and P2O5 are enriched by a factor of 1.5 in the DAP fertilizer and
the U in phosphogypsum is around 2 ppm.
6. Phosphogenesis and the Enrichment of U: Discussion
Why phosphorites have more U compared with other
sedimentary rocks? Why U contents increases northwards
in the Jordanian phosphorites? Following is an attempt to
answer these and others related to phosphogenesis.
Phosphorite, bedded chert, porcelanite and organic-rich
sediments, as an association, are known to deposit under
upwelling currents regimes (Sheldon, 1987; Iijima, et al.,
1994 and the papers within). This is well documented in
the recent and subrecent Earth history in shallow
continental shelf where upwelling currents are intense and
still ongoing; e.g. the coasts of SW Africa (Birch, 1980),
the western coast of South America up till California in the
north (Froelich et al., 1988; Burnett, 1990; Kolodny and
Garrison, 1994), and in the southeastern United States
where the Gulf Stream causes upwelling (Riggs et al.,
1998). Thus, the association of these facies is usually
taken as due to upwelling in ancient phosphorite deposits
(Baturin, 1982; Abed and Amireh, 1983; Alomogi-Labin
et al., 1993; Glenn et al., 1994; Follmi, 1996). However,
some authors had explained the formation of ancient
phosphorites without the need of upwelling (e.g. Heggie et
al., 1990; Glenn and Arthur, 1990)
Upwelling currents spread deep, cold marine water on
the surface of the relatively shallow continental shelves
adjacent to the continents (Fig. 10). Deep, cold water,
1000 m or more, is usually rich in nutrients, most
important of which are Si and P which are the basic food
© 2011 Jordan Journal of Earth and Environmental Sciences . All rights reserved - Volume 4, (Special Publication, Number 2)(ISSN 1995-6681)
43
for the phytoplanktons (diatoms and dinoflagellates); the
lowest step in marine food chains which inhabit the photic
zone or the upper 100-200 m of the sea water column.
Under such conditions, bioproductivity of the marine food
chain is highly increased. Rate of death of these organisms
is consequently increased to produce an oxygen minimum
zone (OMZ) extending few hundred metres below the
photic zone and might reach the shelf floor. The formation
of the OMZ reduces the amount of the oxidized soft tissues
of the descending organisms, thus giving more chances to
the soft tissues (organic matter, OM) to joint the sediments
accumulating at the shelf floor. A higher rate of
sedimentation will ensure a higher rate of burial for the
OM to escape long exposure and oxidation. Consequently,
a sediment- rich OM is formed (Baturin, 1982; Salansky,
1986; Glenn et al., 1994; Lucas and Prevot-Lucas, 1995).
Fig. 10 A schematic model for phosphorite deposition under an
upwelling regime.
Decomposition of the sediment organic matter below
the water/sediment interface by bacteria and fungi liberates
phosphorous to the interstitial pore fluids. Certain minerals
form from these fluids like calcite, dolomite and
palygorskite before the formation of apatite. This means
that P, most probably as PO4, is concentrated many folds
relative to sea water before its deposition (Riggs et al.,
1985). Finally, apatite is either precipitated directly from
these interstitial fluids (authigenic origin) or the fluids
react with pre existing sediments and transform them into
apatite (diagenetic origin) (Price and Calvert, 1978; Birch
et al., 1983; Froelich et al., 1983).
Jordanian phosphorites are postulated to have deposited
under upwelling cold, deep water from the Tethys Ocean
in the north onto its shallow epeiric shelf where Jordan
was situated during the upper most Cretaceous. This is
evident from the presence of phosphorite, bedded chert,
porcelanite (biogenic silica deposits), oil shale and a
pronounced negative cerium anomaly indicative of deep
oceanic water (Abed and Abu Murry, 1997). Furthermore,
Jordanian phosphorites are dominantly authigenic,
precipitated from the pore fluid solutions as phosphate
mud, which was then reworked into phosphate pellets and
intraclasts (Al-Agha, 1985; Abed and Al-Agha, 1989).
Recent pelletal phosphorites off the SW Africa and
Peru margins are carbonate fluorapatite (Baturin, 1971;
Burnett, 1977; Price and Calvert, 1978; Froelich et al.,
1983). The concentrations of P, C, and F in the upper few
tens of centimeters of the sediment pore water are high
enough to permit their direct chemical precipitation as
carbonate fluor apatite. On the other hand, the bone
material is made of dahlite; carbonate hydroxyapatite, with
F content far less than 1% or even hydroxyapatite which is
devoid of F (McConnell, 1973; Altschuler, 1973). Dahlite
is readily converted into carbonate fluorapatite through the
interaction with sediment pore water during early
diagenesis, incorporating F and possibly CO3 into its
structure. This conversion process takes place
contemporaneously with the direct precipitation of
pelletal/intraclast material as carbonate fluorapatite
(Froelich et al., 1983; Abed and Fakhouri, 1996).
Accordingly, there should be abundant organic matter
associated with the phosphorites in their depositional
environment. Organic matter is well known as a good
scavenger for U and many other trace metals. Most
probably, the newly deposited apatite would take up U into
its open crystal structure from the engulfing pore fluids
which were formed after organic matter decomposition.
Uranium, then, becomes part of the apatite occupying
some of the positions located for Ca in the apatite
structure. It should be emphasized that U in the ancient
phosphorites is present within the crystal structure of
apatite not adsorbed on the organic matter (Froelich et al.,
1983; Bernett, 1990).
In Jordan, the northwards increase of U may be due to
higher organic matter associated with the phosphorites in
north Jordan. The NW Jordan deposits have around 6%
organic matter (Abed and Al-Agha, 1989) with much
lower contents further south. The organic matter in the
other localities, other than NW Jordan, is to be seen within
the phosphate pellets and intraclasts. The dark colour of
some of these particles is indicator of organic matter. This
is evident from the leaching and oxidation of
pellets/intraclasts rims by percolating oxidizing
groundwater through these permeable phosphorite deposits
throughout the history of these deposits.
7. Conclusions
High grade phosphorites are wide spread in Jordan.
Despite the fact that Ruseifa mines were closed and the
central Jordan deposits and near depletion, huge reserves
are still existing in Eshidiyya Basin (in excess of 1000
million tons), Al-Kora Basin, NW Jordan (several hundred
million tons), and the subsurface of the eastern desert.
The phosphorites of Jordan are the main carrier of
Uranium in the country. Uranium is present within the
crystal structure of francolite (carbonate flour apatite)
substituting for Ca. Uranium content varies up 379 ppm in
certain phosphorite horizons.
Uranium content in the various localities increases
northwards. Eshidiyya deposits lower member (main
deposits) has around 70 ppm U while the upper member
(A0) 133 ppm, central Jordan 105 ppm, Ruseifa 123 ppm,
and NW Jordan 153 ppm. It should be emphasized that
certain phosphorite horizons have much more U compared
with these averages. Detailed field geology can pinpoint
such horizons if U is to be exploited. It is here postulated
that organic matter may be one of the main reason for the
northwards increase of U.
During mining and upgrading of the phosphorite ores,
U sticks to the mineral francolite and thus behaves similar
to Ca and P2O5. No groundwater contamination with U is
noticed in central Jordan despite the fact that fresh water
used in washing the upgraded ore has been discharged to
the local environment since more than 45 years.
© 2011 Jordan Journal of Earth and Environmental Sciences . All rights reserved - Volume 4, (Special Publication, Number 2)(ISSN 1995-6681)
44
Throughout the fertilizers industry, U follows P, first
into the phosphoric acid and then into the diammonium
phosphate (DAP) where it becomes concentrated by a
factor of 1.5 relative the fed ore. On the contrary, calcium
leaves francolite to phosphogypsum but U does not follow
suite, thus phosphogypsum is almost devoid of U with a
content up to 2 ppm.
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