Mineralogy, geochemistry and the origin of high-phosphorus oolitic iron ores of Aswan, Egypt

Ore Geology Reviews 80 (2017) 185–199

Contents lists available at ScienceDirect

Ore Geology Reviews journal homepage: www.elsevier.com/locate/oregeorev

Mineralogy, geochemistry and the origin of high-phosphorus oolitic iron ores of Aswan, Egypt Hassan Baioumy a,⁎, Mamdouh Omran b,c, Timo Fabritius b a b c

Geosciences Department, Faculty of Geosciences and Petroleum Engineering, Universiti Teknologi PETRONAS, 31750 Tronoh, Perak, Malaysia Laboratory of Process Metallurgy Research Group, Process and Environmental Engineering Department, University of Oulu, Finland Mineral Processing and Agglomeration Laboratory, Central Metallurgical Research and Development Institute, Cairo, Egypt

a r t i c l e

i n f o

Article history: Received 27 February 2016 Received in revised form 24 June 2016 Accepted 26 June 2016 Available online 04 July 2016 Keywords: Oolitic iron ores Aswan Egypt Apatite Origin Source

a b s t r a c t The Coniacian-Santonian high-phosphorus oolitic iron ore at Aswan area is one of the major iron ore deposits in Egypt. However, there are no reports on its geochemistry, which includes trace and rare earth elements evaluation. Texture, mineralogy and origin of phosphorus that represents the main impurity in these ore deposits have not been discussed in previous studies. In this investigation, iron ores from three localities were subjected to petrographic, mineralogical and geochemical analyses. The Aswan oolitic iron ores consist of uniform size ooids with snowball-like texture and tangentially arranged laminae of hematite and chamosite. The ores also possess detrital quartz, apatite and fine-grained ferruginous chamosite groundmass. In addition to Fe2O3, the studied iron ores show relatively high contents of SiO2 and Al2O3 due to the abundance of quartz and chamosite. P2O5 ranges from 0.3 to 3.4 wt.% showing strong positive correlation with CaO and suggesting the occurrence of P mainly as apatite. X-ray diffraction analysis confirmed the occurrence of this apatite as hydroxyapatite. Under the optical microscope and scanning electron microscope, hydroxyapatite occurred as massive and structureless grains of undefined outlines and variable size (5–150 μm) inside the ooids and/or in the ferruginous groundmass. Among trace elements, V, Ba, Sr, Co, Zr, Y, Ni, Zn, and Cu occurred in relatively high concentrations (62–240 ppm) in comparison to other trace elements. Most of these trace elements exhibit positive correlations with SiO2, Al2O3, and TiO2 suggesting their occurrence in the detrital fraction which includes the clay minerals. ΣREE ranges between 129.5 and 617 ppm with strong positive correlations with P2O5 indicating the occurrence of REE in the apatite. Chondrite-normalized REE patterns showed LREE enrichment over HREE ((La/Yb)N = 2.3–5.4) and negative Eu anomalies (Eu/Eu* = 0.75–0.89). The oolitic texture of the studied ores forms as direct precipitation of iron-rich minerals from sea water in open space near the sediment-water interface by accretion of FeO, SiO2, and Al2O3 around suspended solid particles such as quartz and parts of broken ooliths. The fairly uniform size of the ooids reflects sorting due to the current action. The geochemistry of major and trace elements in the ores reflects their hydrogenous origin. The oolitic iron ores of the Timsha Formation represent a transgressive phase of the Tethys into southern Egypt during the Coniacian-Santonian between the non-marine Turonian Abu Agag and Santonian-Campanian Um Barmil formations. The abundance of detrital quartz, positive correlations between trace elements and TiO2 and Al2O3, and the abundance mudstone intervals within the iron ores supports the detrital source of Fe. This prediction is due to the weathering of adjacent land masses from Cambrian to late Cretaceous. The texture of the apatite and the REE patterns, which occurs entirely in the apatite, exhibits a pattern similar to those in the granite, thus suggesting a detrital origin of the hydroxyapatite that was probably derived from the Precambrian igneous rocks. Determining the mode of occurrence and grain size of hydroxyapatite assists in the maximum utilization of both physical and biological separation of apatite from the Aswan iron ores, and hence encourages the use of these ores as raw materials in the iron making industry. © 2016 Elsevier B.V. All rights reserved.

1. Introduction Oolitic iron ores of high phosphorus are widely distributed with some large-scale deposits worldwide such as the Wadi Fatima mine in ⁎ Corresponding author. E-mail address: [email protected] (H. Baioumy).

http://dx.doi.org/10.1016/j.oregeorev.2016.06.030 0169-1368/© 2016 Elsevier B.V. All rights reserved.

Saudi Arabia (Manieh, 1984), Lorraine mine in France (Champetier et al., 1987), Bell Island mine in Canada (Ozdemir and Deutsch, 1984), Dilband mine in Pakistan (Abro et al., 2011), and Xuanhua and Ningxiang regions in China (Li et al., 2011; Zhang et al., 2014). The main problem associated with exploiting these deposits is the dissemination of fine silicate minerals and the high level of phosphorus content due to the poor liberation of iron minerals from the gangues (Song et al.,

186

H. Baioumy et al. / Ore Geology Reviews 80 (2017) 185–199

2013). Although these iron ores have economic and geological significances, their geochemical characteristics were not discussed widely in the previous investigations (Petruk, 1977; Sturesson, 1995, 2003). A considerable amount of literature focused on the physical and chemical processes to remove phosphorus from the ores using chemical, thermal and biological methods (Delvasto et al., 2009; Wen-tang et al., 2011; Omran et al., 2015), without due deliberations on the sources and origins of the P-bearing minerals. The high-phosphorus oolitic iron ores in Aswan area is one of the major iron ore deposits in Egypt. Other significant iron ore sites include the sedimentary iron ores at the Bahariya Oasis and banded deposits (BIF) in the Eastern Desert. Iron ores from the Bahariya Oasis are currently utilized by the Egyptian Steel Company (ESC) to produce steel for domestic consumption. Due to the predictable depletion of these ores, there were attempts to exploit other ores for the iron making industry from the oolitic iron ores of the Aswan. However, these attempts were unsuccessful due to the high phosphorus contents in the Aswan ore deposits. This proliferation is due to the poor liberation of iron minerals from impurities which include the P-bearing minerals. Part of this problem is probably due to the paucity of data on the mineralogy and mode of occurrence of phosphorus in these iron ores. Also, the geochemical characteristics which include trace and rare earth elements of these iron ores were not discussed in previous literature. Thus, this study highlights the texture and origin of P-bearing minerals in the ore deposits. The work also examined the distribution and mineralogy of the trace and rare earth elements and appraised the possible source(s) of iron and the depositional conditions of these valuable iron ores based on their geochemistry. The exploitation of iron ore at the Aswan site could influence an economic impact in the worldwide distribution of oolitic iron ores. The geochemical investigations of the iron ores appreciate the origin of these deposits and the nature of phosphorus which represents one of the most significant impurities. This evaluation provides the platform for a maximum utilization of both the physical and the biological separation of P-bearing minerals from these ores.

2. General geology The oolitic iron ores are widely distributed in Africa, which includes southern Egypt, northern Sudan, and Nigeria (Mucke, 2000) (Fig. 1). In Egypt, oolitic iron ores occur in the Wadi Abu Agag and Wadi Subeira areas, east of Aswan (Fig. 2A) and Um Hibal area southeast Aswan (Fig. 2B) (Doering, 1990). East Aswan area is located about 12 km to the northeast of Aswan, between latitudes of 24°05′00″ and 24°15′00″ N and longitudes of 32°55′00″ and 33°15′00″E. Um Hibal area is located about 60 km to the southeast of Aswan, between latitudes of 23°36′00″ and 23°52′00″N and longitudes of 33°07′00″ and 33°30′00″E (Fig. 2B) (Ghazaly et al., 2015). Both areas are occupied by highly lateritized Precambrian metamorphic and igneous rocks of the Arabo-Nubian Shield (ANS), unconformably overlain by Upper Cretaceous clastic successions. The ANS is composed mainly of granites, granodiorites, quartz diorites, gneiss, gabbros, amphibolites and metasediments (e.g. Liégeois and Stern, 2010; Kuster and Liegeois, 2001; Ali et al., 2009). The Upper Cretaceous sediments of the studied areas are divided into three units that overlay the Precambrian basement rocks; the basal Abu Agag Formation (Turonian), the Timsha Formation (Coniacian-Santonian), the uppermost Um Barmil Formation (Santonian-Cambrian) (Fig. 3) (e.g. Klitzsch, 1986; Bhattacharyya, 1989; El Aref et al., 1996; El Sharkawi et al., 1996; Mucke, 2000). The iron-bearing formation (Timsha Formation) has a thickness of 10–35 m and consists of four coarseningupward sequences. Furthermore, sequences contain at least four horizons of ooidal ironstone (Fig. 3). The total reserves are about nine million tonnes (Hussein and Sharkawi, 1990; Mucke, 2000). From the deep to shallow layers, the sedimentary sequence of the Timsha Formation at Wadi Abu Agag and Wadi Subeira areas (Fig. 4A) is comprised of yellowish grey and reddish grey laminated mudstone with non-oolitic ironstone intercalations of what is called Aswan clays (Fig. 4B). This mudstone interval is overlain by two large oolitic iron ores beds with a thickness ranging from 2 m (lower bed) to about 4 m (upper bed) and separated by yellowish to reddish grey 30 cm-thick shale layer (Fig. 4C and D). Iron ore occurs as hard and massive beds

Fig. 1. Geographical setting of the late Cretaceous ooidal ironstone deposits of Egypt, Sudan and Nigeria. (Adapted from Mucke (2000)).

H. Baioumy et al. / Ore Geology Reviews 80 (2017) 185–199

187

Fig. 2. (A) Geological map of East Aswan shows the location of study samples from Wadi Abu Sobera and Wadi Abu Agag areas. (B) Geological map of the Um Hibal area showing the locality of the iron-bearing formation. (A: adapted from Mucke (2000); B: after Ghazaly et al. (2015)).

with metallic luster and red streak. The ooids of the iron ore are coarse enough to be seen in the hand specimen (Fig. 4E). The iron-bearing horizon is overlain by a thick (more than 30 m) sequence of clays, sandstone, and sandy clays. The sedimentary sequence of the Timsha Formation at Um Hibal area is shown in Fig. 4A. Iron ores in this area occur as pale red to reddish yellow oolitic iron ores bed ranging in thickness from 1 to 1.5 m (Fig. 5B, C). The iron ores bed overlies yellowish grey ferruginous mudstone (Fig. 5D) and often overlie by fine-grained yellowish brown sandstone (Fig. 5C) or without any sedimentary cover (Fig. 5E). 3. Materials and methods Twenty samples representing the oolitic iron ores were collected from Wadi Abu Sobera, Wadi Abu Agag, and Um Hibal areas and

subjected to petrographic, mineralogical and geochemical investigations. Eight thin sections were prepared and investigated with the optical microscope. Twenty bulk samples were analyzed for their mineralogical composition using the X-ray diffraction (XRD) technique with a Philips PW1820 (Cu-Kα, 40 kV, 40 mA) instrument. Morphology and chemistry of apatite grains were investigated in the fractured surface of two iron ore samples using a scanning electron microscope (SEM) (Philips S-2400s). XRD and petrographic investigations were performed at the Laboratory of Process Metallurgy Research Group, Process and Environmental Engineering Department, University of Oulu, Finland. Fused discs prepared for twenty representative samples were analyzed for their major oxides (SiO2, TiO2, Al2O3, Fe2O3, MnO, MgO, CaO, K2O, Na2O, and P2O5) by XRF using a Philips PW 2400 X-ray spectrometer. Tube voltage and current for W target were 40 kV and 60 mA, respectively. Loss on ignition (L.O.I.) was obtained by heating

188

H. Baioumy et al. / Ore Geology Reviews 80 (2017) 185–199

Fig. 3. General stratigraphic column of the late Cretaceous sedimentary cover in Aswan area. (Modified from El Sharkawi et al. (1996)).

sample powders to 1000 °C for 6 h. ICP-MS determined the trace and rare earth elements using ten bulk ore samples after digestion. The samples powders were digested with 2 mL concentrated (49%) HF in capped Teflon bombs on an electrical hot plate (~150 °C) for 24 h. The solution was evaporated to near dryness and redissolved in 2 mL of 6 mol/L HNO3 in capped Teflon bombs at 150 °C for two days. The samples were then evaporated near to dryness, later 1 mL of 6 mol/L HNO3 was added, and the solutions were further diluted for analysis (Jenner et al., 1990). Geochemical analyses of major trace and rare earth elements were performed at the ACME Lab., Canada. 4. Results 4.1. Mineralogy XRD patterns of the oolitic iron ores from Aswan are shown in Fig. 6. Phosphorus-poor samples are composed mainly of hematite with traces of chamosite (Fig. 6A) while P-rich samples are made up of hematite,

hydroxyapatite, and chamosite. Hydroxyapatite is identified by its characteristic peaks at 2.80 Å (100), 2.70 Å (60), 2.77 Å (55), and 3.44 Å (40) (Fig. 6B). According to PDF files (number 25-167), these peaks are related to the hydroxyapatite mineral with the chemical formula of Ca5(PO4)3(OH, Cl, F) of the hexagonal system. EDX analysis also confirmed the occurrence of Cl and F in the structure of hydroxyapatite. 4.2. Petrography The studied iron ores are coarse-grained and of greyish, brownish or reddish brown in color. Under the optical microscope, the ores consist of ooids, detrital quartz, apatite and fine-grained groundmass (Fig. 7A). The ooids show a snowball-like texture of tangentially arranged laminae (Fig. 7B). Two types of ooids can be distinguished in the studied iron ores, namely the concentric and eccentric ooids. In the concentric ooids which are more common, the ooid laminae and zones are distributed concentrically around the nucleus, while in the eccentric ooids the successive laminae and zones are distributed eccentrically around the

H. Baioumy et al. / Ore Geology Reviews 80 (2017) 185–199

189

Sand and clays

A B

C

D

E

Legend: Oolitic iron ores

Sandstone Oolitic iron ore Ferruginous mudstone Clays Non-ooliticiron stone

Aswan ferruginous clays

Samples position

2m

Fig. 4. Stratigraphic column of the iron-bearing formation at Wadi Abu Sobera (A) with field photos of thick oolitic iron ores beds (red arrows) (B and C) as well as thin non-oolitic ironstone beds inside the mudstones (red arrows) (D). (E) Close up to the iron ores in which ooliths can be seen. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

nucleus and show a progressive stages of accretion. The detrital quartz occurs as fine- to medium-grained subangular to subrounded grains both as nuclei of the ooides and in the groundmass. Chamosite occurs mainly as fine-grained groundmass (Fig. 7A and B). A characteristic feature of this groundmass is its ferruginasation due to the presence of hematite. Ferruginisation ranging continuously from nearly unaffected to completely altered material. Ferruginisation starts at individual spots

A

and finally spreads through the whole groundmass. In the high-P samples, apatite occurs as rounded to subrounded and oval grains that range in size from 50 to 150 m inside the ooids (Fig. 7C) and/or in the ferruginous groundmass (Fig. 7D). SEM images of the ooids revealed the occurrence of chamosite as thin laminae alternating with the hematite (Fig. 8A, B, C). Hematite under SEM shows it consists of well-developed euhedral crystals of

B

C

D

E

Legend: Sandstone Oolitic iron ore

Ferruginous mudstone Samples position

1m

Fig. 5. General stratigraphic column of the iron-bearing formation at Um Hibal area (A) with field photos of the iron ores (red arrow) and mudstone (green arrow) intercalations (B). (C) Close up to the iron ores (red arrow) covered with sandstone (black arrow). (D) Close up to the underlying ferruginous mudstone. (D) Close up to the iron ores (red arrow) without sedimentary cover (red arrow). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

190

H. Baioumy et al. / Ore Geology Reviews 80 (2017) 185–199

1400

A

He

1200

Intensity (CPS)

almost the same sizes (Fig. 8D and E). On the other hand, chamosite exhibits anhedral crystal habit of very fine grain size (Fig. 8F). Apatite under SEM occurs as massive and structureless grains of undefined outlines and variable size (5–70 m) (Fig. 8G, H). Energy dispersive X-ray (EDX) analysis (Table 1) confirmed the occurrence of apatite through the intense peaks of Ca and P (Fig. 8I). The EDX analysis also showed the presence of F, up to 0.6 wt.% (Fig. 8J), as well as traces of Cl with 0.1–0.5 wt.% (Fig. 8K) in the crystal structure of hydroxyapatite in addition to the P and Ca. According to Mackie et al. (1972) and Elliott et al. (2002), hydroxyapatite contains typically 0.28 wt.% of F. The relatively high F content in the studied hydroxyapatite may be due to further F substitution in the structure of the hydroxyapatite or the precision of analysis in the current study.

He=Hematite Qz= Quartz Ch= Chemosite

1000 800

He

600 He

He

Ch

400

He

He Qz

200

He

He

He

He

He

He

0 10

20

30

40

50

60

70

2θ θ°

4.3. Geochemistry

1000

B He+Ap

Intensity (CPS)

800

He+Ap

600 Qz

400 He

Ch

Ap

He

He

Ap

200

He He

He

He

Qz He

0 10

20

30

40

50

60

70

2θ° Fig. 6. X-ray patterns of the phosphorus-poor (A and B) and P-rich (C) iron ores show the characteristic peaks of hydroxyapatite in the P-rich iron ore.

4.3.1. Major oxides The distribution of major oxides in twenty samples of oolitic iron ores from Aswan is shown in Table 2. Fe2O3 contents range between 30.4 and 90.1 wt.% with an average of 72.2 wt.%. P2O5 contents vary from 0.22 to 7.4 wt.% with an average of 2.1 wt.%. The P2O5 contents are still higher than the limit of P2O5 contents in the iron ores of steel and iron making industries (b0.05 wt.%) (Gordon, 1996). CaO contents range between 0.46 and 10.1 wt.% (average 3 wt.%) and exhibit strong positive correlation (r2 = 0.99) with P2O5 (Fig. 9A) manifesting that Ca and P belong to the same phase, apatite. The relatively high contents of SiO2 (4.3–50.4 wt.%, average of 12.7 wt.%) and Al2O3 (2.1–7.2 wt.%, average of 3.7 wt.%) in the studied iron ore samples is due to the presence of chamosite, and XRD and SEM analyses also indicate this result. The positive correlation (r2 = 0.67) between SiO2 and Al2O3 contents (Fig. 9B) confirms the interpretation. The deviation in this correlation can be attributed to the presence of SiO2 as quartz in addition to the chamosite, which is indicated by XRD analysis. TiO2 contents with an average of 0.28 wt.% show positive correlations with SiO2 (r2 = 0.97)

B

A

Oo

Oo

Ch

Qz

Ch

C

D Hem

Od Qz

Hem

Fig. 7. (A) Photomicrograph of the oolitic iron ores under an optical microscope showing the uniform size ooliths (Oo) with quartz (Qz) nuclei in the ferruginous chamosite groundmass (Ch). (B) A close up to the ooliths that are composed of tangentially arranged laminae. Hydroxyapatite occurs as anhydral and elongated grains (white circle) range in size from 0.1 to 0.25 mm either (C) inside the ooids (Od) or (D) in the ferruginous groundmass (Hem) associated with the detrital quartz grains (Qz).

H. Baioumy et al. / Ore Geology Reviews 80 (2017) 185–199

(Fig. 9C) and Al2O3 (r2 = 0.66) (Fig. 9D), which suggests the occurrence of TiO2 in the detrital fraction. MnO concentrations range between 0.02 and 3.48 wt.% (average 0.72 wt.%). MgO, Na2O, and K2O occur in very low contents with averages of 0.6, 0.16, and 0.11 respectively. In General, Fe2O3 shows negative correlations with the impurities (SiO2, Al2O3, P2O5, CaO, MnO and TiO2). 4.3.2. Trace elements The distribution of trace elements in the oolitic iron ores from Aswan area are listed in Table 3. Vanadium records the highest concentrations with an average of 484 ppm. Ba, Sr, Co, Zr, Y, Ni, Zn, and Cu occur in relatively high concentrations compared to other trace elements (averages 240, 220, 125, 124, 110, 104, 73, and 62 ppm, respectively). However, elements such as Mo, Pb, As, Sc, Be, Ga, Hf, Th, Nb, Rb, and U exhibit

191

relatively low concentrations compared to other trace elements (averages range from 3 to 28 ppm). Other trace elements (Cd, Sb, Bi, Ag, Au, Hg, Tl, Se, Sc, Sn, Te, and W) show very low concentrations (below 3 ppm). The correlations between the trace elements and major oxides have been calculated to examine the possible source and mineralogy of these trace elements. Most of the trace elements such as Cu, Zn, Ni, Sc, Co, Hf, Nb, Rb, Th, Ga, and Zr exhibit positive correlations with SiO2 (Fig. 10A and B), Al2O3 (Fig. 10C and D), and TiO2 (Fig. 10E and F) suggesting the occurrence of these elements in the detrital fraction of the studied ores which includes the clay minerals. Mo, Be, and Y show positive correlations with P2O5 (Fig. 10G) indicating the occurrence of these elements in the apatite structure. Meanwhile, Pb and Ba probably associate the Mn-bearing minerals in the studied iron ores as shown from the positive correlations between these two elements and MnO

A

B

D

C

E

F

Ch He

Fig. 8. (A) Backscattered photomicrograph of the oolitic iron displaying the uniform size ooliths (Oo) with quartz nuclei (Qz) in the ferruginous chamosite groundmass (Ch). (B and C) SEM photomicrographs the ooliths that are comprised of tangentially arranged laminae of hematite (He) and chamosite (Ch). (D) SEM photomicrographs of the anhedral fine-grained chamosite groundmass. (E and F) SEM photomicrographs of the euhedral hematite. (G) Backscattered photomicrograph of the hydroxyapatite (Ap) grain. (H) SEM photo of hydroxyapatite (Ap) grains of different sizes and shapes inside ferruginous matrix (He). (I) EDX pattern of an apatite grain showing the chemical composition of hydroxyapatite being dominated by P and Ca. (J) EDX pattern of an apatite grain displays the occurrence of fluorine in its crystal structure. (K) EDX pattern of an apatite grain shows the occurrence of chlorine in its crystal structure.

192

H. Baioumy et al. / Ore Geology Reviews 80 (2017) 185–199

G

H He Ap Ap Ap

JI

J

J K

Fig. 8 (continued).

(Fig. 10H). None of the analyzed trace elements show positive correlations with the Fe2O3, but most of them such as Cu, Zn, Ni, Sc, Co, Hf, Nb, Rb, Th and Zr exhibit strong negative correlations with Fe2O3. This result indicates that none of these elements occur in the hematite structure.

Table 1 EDX analysis of two apatite grains (wt.%) from Aswan oolitic iron ores. Element

Wadi Abu Sobera

Wadi Abu Agag

F Na Al Si P Cl Ca Fe O Total

0.6 – 0.8 0.6 9.8 0.1 17.3 16.1 54.7 100.0

– 0.3 0.2 0.6 9.5 0.5 17.4 15.5 56.0 100.0

4.3.3. Rare earth elements The distribution of rare earth elements in ten samples from the Aswan oolitic iron ores is shown in Table 4. The ΣREE ranges between 129.5 and 617 ppm with an average of 356 ppm. Samples from Wadi Abu Agag area show relatively low ΣREE (average 295 ppm) when compared with those from the Wadi Abu Sobera and Um Hibal areas (averages 393 and 401 ppm, respectively). ΣREE shows strong positive correlations with both CaO and P2O5 (Fig. 11), while no correlations were found between the ΣREE and other major oxides including Fe2O3, SiO2 and Al2O3. This trend indicates the occurrence of REE in the apatite. Chondrite-normalized (Boynton, 1984) REE patterns for iron ores from several localities are shown in Fig. 12. The Eu anomaly is calculated as Eu/Eu* = EuN/(SmN·GdN), and Ce anomaly is calculated as Ce/Ce* = (3Ce/CeN)/(2La/LaN + Nd/NdN). The REE patterns show similar general trends with some exceptions. The patterns show slight LREE enrichment in relation to HREE as shown by (La/Yb)N ratios that vary from 2.3 to 5.4. Slight negative Eu anomalies are pronounced with Eu/Eu* from 0.75 to 0.89. Except for sample WAA4 from the Wadi Abu Agag area that shows slight positive Ce anomaly (Ce/ Ce* = 1.4) and sample WAS1 from the same area that shows slight

H. Baioumy et al. / Ore Geology Reviews 80 (2017) 185–199

193

Table 2 Distribution of major oxides (wt.%) in representative oolitic iron ore samples from Aswan area measured by XRF. Area

Samples

SiO2

Al2O3

Fe2O3

MgO

CaO

Na2O

K2O

TiO2

P2O5

MnO

LOI

Sum

Wadi Abu Sobera

WAS1 WAS2 WAS3 WAS4 WAS5 WAS6 WAS7 WAS8 WAA1 WAA2 WAA3 WAA4 WAA5 WAA6 WAA7 WAA8 WAA9 UMH1 UMH2 UMH3

5.85 27.75 4.7 5.05 6.39 24.3 6.85 9.53 4.32 6.13 4.49 8.48 8.65 5.21 21.38 18.74 13.34 6.54 15.37 50.37

2.74 5.13 2.07 2.25 3.28 4.98 3.52 4.31 2.75 2.28 2.09 3.26 4.14 3.2 3.17 4.67 5.64 4.11 3.6 7.24

67.25 63.15 77.37 89.78 84.16 61.53 82.01 82.76 83.04 84.32 90.07 76.9 74.47 76.06 58.5 65.36 63.61 76.08 56.41 30.36

0.84 0.06 0.72 0.13 0.1 0.08 0.14 0.03 0.31 0.12 0.13 0.57 0.33 0.74 0.97 1.36 1.42 0.6 0.93 2.53

7.78 0.86 4.66 0.46 2.03 2.44 1.7 1.01 2.55 1.27 0.69 2.7 4.33 4.85 3.29 0.97 3.74 4.46 10.08 0.5

0.17 0.06 0.38 0.04 0.04 0.05 0.04 0.03 0.1 0.08 0.09 0.11 0.12 0.3 0.21 0.22 0.76 0.13 0.21 0.11

0.05 0.07 0.02 0.04 0.07 0.1 0.08 0.04 0.06 0.07 0.76 0.01 0.15 0.02 0.06 0.04 0.06 0.06 0.09 0.25

0.14 0.59 0.08 0.14 0.19 0.55 0.21 0.22 0.07 0.14 0.13 0.15 0.26 0.14 0.48 0.36 0.25 0.15 0.24 1.03

5.63 0.71 3.2 0.29 1.15 1.79 0.97 0.8 1.84 0.82 0.64 1.95 3.37 3.02 2.1 0.38 2.56 3.13 7.39 0.22

3.48 0.02 0.82 0.1 0.39 0.14 0.3 0.06 1.32 0.06 0.59 0.98 0.69 0.78 2.29 0.69 0.5 0.24 0.72 0.17

5.7 1.8 5.8 1.7 2.1 4.0 4.1 1.1 3.4 4.6 0.3 4.7 3.3 5.4 7.2 6.9 7.8 4.2 4.6 6.8

99.63 100.2 99.82 99.98 99.9 99.96 99.92 99.89 99.76 99.89 99.98 99.81 99.81 99.72 99.65 99.69 99.68 99.7 99.64 99.58

Wadi Abu Agag

Um Hebal

negative Ce anomaly (Ce/Ce* = 0.92), no significant Ce anomalies have been observed in the rest of analyzed samples (Ce/Ce* ranges from 0.98 to 1.14). 5. Discussion 5.1. Origin and of iron ores The Aswan iron ores are sedimentary ironstone beds composed of ooliths and clastic material in a ferruginous cement. The oolitic texture

forms as direct precipitation of iron-rich minerals on suspended nucleus (Hemingway, 1974). The ooliths are ellipsoidal or rounded, which indicate that they were formed in open space near the sediment-water interface by accretion of FeO, SiO2, Al2O3 and minor amounts of other oxides around solid particles (e.g. Bubenicek, 1968). Fig. 13 shows a possible mechanism for the evolution and formation of ooids in the Aswan oolitic iron ores. Due to long-term weathering of the Precambrian igneous rocks in the studied area, seawater is saturated with cations and anions especially Fe, Si and Al (Fig. 13A). As a result, hematite and chamosite are precipitated over nucleus such as detrital quartz, apatite

Fig. 9. Positive correlations between P2O5 and CaO (A), SiO2 and Al2O3 (B), TiO2 and SiO2 (C) TiO2 and Al2O3 (D).

194

H. Baioumy et al. / Ore Geology Reviews 80 (2017) 185–199

Table 3 Distribution of trace elements (ppm) in representative oolitic iron ore samples from Aswan area measured by ICP-MAS. Samples

Mo Cu Pb Zn Ni As Cd Sb Bi Ag Au Hg Tl Se Sc Ba Be Co Cs Ga Hf Nb Rb Sn Sr Ta Th U V W Zr Y

Wadi Abu Sobera

Wadi Abu Agag

Um Hebal

WAS1

WAS2

WAS3

WAA1

WAA2

WAA3

WAA4

UMH1

UMH2

UMH3

3.5 21.3 136.7 79.05 77 6.6 0.1 0.8 0.1 0.1 5.2 0.02 0.3 0.5 8 476 7 96.5 0.5 6.7 0.8 2.7 4.5 1 352.5 0.1 1.8 7.7 193 1.6 33.5 211.6

1.6 11.5 11.2 5.1 19.3 3.4 0.1 0.3 0.1 0.1 2.8 0.01 0.1 0.5 9 184 2 7.1 0.8 5.8 1.4 3.7 4.5 2 515.6 0.2 2.7 13 277 1 57.6 65.5

2.9 17.4 6.1 39.95 70.3 19.9 0.1 0.3 0.1 0.1 0.5 0.01 0.3 0.5 9 121 6 68.5 0.4 6.6 0.6 2.1 2.8 1 116.3 0.2 2.2 5.6 331 3.6 21.7 101.8

5.1 22.6 16.7 36.55 88.5 13.2 0.1 0.3 0.2 0.1 0.5 0.01 0.2 0.5 8 282 3 81.9 0.5 6.4 1 2.5 2.4 1 150.7 0.3 1.9 5.9 363 3.9 37.1 110.2

2.4 41.8 15.4 60.35 137.1 9.8 0.1 0.3 0.2 0.1 0.5 0.02 0.3 0.5 8 655 3 216 0.6 7.5 4.5 6.6 5.7 2 348.2 0.4 3 3.8 220 0.5 184 76.6

2.3 7.9 30.5 72.25 97.2 2.1 0.1 0.2 0.1 0.1 0.5 0.01 0.1 0.5 10 117 1 73.5 0.5 8.2 3.8 5.9 3.8 1 141.3 0.4 2.9 2.9 749 0.9 150.1 30.6

3.3 48.8 13.7 104.55 117.1 8.7 0.1 0.2 0.1 0.1 2.2 0.02 0.1 0.5 9 110 5 118.5 0.5 17.7 1.6 4.1 6 1 147.5 0.2 3.5 2.7 854 0.7 57.2 114

3.8 21.4 5 32.3 62.2 14.4 0.1 0.3 0.2 0.1 1.8 0.02 0.1 0.5 9 160 7 41.3 0.5 7.2 0.8 2.7 3.7 2 145.6 0.1 2.1 3.7 720 0.5 31.7 128.2

5.7 228.6 29 54.4 131.9 24.4 0.1 0.4 0.2 0.1 1.5 0.02 0.1 0.5 8 201 14 173.4 0.3 7.1 1.5 3.5 4.4 1 202.3 0.2 2.3 3.7 510 0.5 62.6 225.2

1.6 306.5 15.8 137.7 244 35.6 0.1 0.1 0.4 0.1 0.5 0.01 0.1 0.5 13 98 7 378.8 0.7 14.4 15.1 11 9 2 86 0.7 5.5 3.3 624 0.5 611.4 45.5

grains or parts of broken ooliths at the water-sediments interface as discontinuous (Fig. 13B) then continuous (Fig. 13C, D) laminae. Some ooliths were broken by local currents before they were buried in the sediment and some oolith pieces sieved as nuclei for deposition of other ooliths (Fig. 13E). Petruk (1977) suggests that the fairly uniform size of the ooliths reflects sorting due to the current action. The late Cretaceous sedimentary cover of the studied area consists of three formations; the Abu Agag, the Timsha, and the Um Barmil formations. According to El Sharkawi et al. (1996), the Abu Agag formation comprises of three units of braided stream system which includes a basal massive kaolinitic conglomerate unit representing channel lag deposits, a middle trough and tabular cross-bedded conglomerate conglomeratic sandstone unit representing distal channels environment of braided system, and an upper mudstone-dominated unit representing floodplain sedimentation. According to Meshref (1990), a critical regressive phase has been established during Turonian as a result of the late Cretaceous-early Tertiary tectonic event accompanied by the elevation of south Egypt including the study area. The oolitic iron ores of marine origin are confined to the Timsha formation, which indicates a transgressive phase of the Tethys into southern Egypt during the Coniacian-Santonian. The Timsha formation is built up of four largescale coarsening-upward sedimentary cycles, representing deposition under a repeated shallowing conditions (El Sharkawi et al., 1996). The occurrence of non-oolitic ironstones within the basal laminated mudstone may reflect deposition from suspension during shallow marine transgression and low clastic input. While the occurrence of oolitic iron ores in the upper part of the coarsening-upward cycles reflects deposition in highly agitated conditions during regressive events terminating short-lived small-scale progradation regimes, sea retreat existed during the Santonian-Campanian time. Consequently, fluvial clastics of Um Barmil formation accumulated in the study area (El Sharkawi et al., 1996).

The marine origin of the oolitic iron ores from Aswan assumes that the iron from these ores was derived from the seawater (hydrogenous) and therefore, reflects the geochemistry of the salt water. This trend is observed for the major oxides and trace elements of the studied ores. Although rare earth elements are widely used to differentiate iron ores based on their origin (hydrogenous versus hydrothermal) (Hein et al., 1990; Usui and Someya, 1997), these elements were not used in this study as most of them occur in the apatite structure, which has a separate origin. Major oxide analyses reflect the hydrogenous origin of the studied deposits through their plotting in the hydrogenous field of the Si-Al discrimination diagram of Choi and Hariya (1992) (Fig. 14A). The (Co + Ni)-(As + Cu + Mo + Pb + V + Zn) binary diagram of Nicholson (1992) and Co + Ni + Cu versus Co/Zn binary plot of Toth (1980) are widely used to discriminate between oceanic hydrogenous and hydrothermal exhalative sediments (Shah and Moon, 2014; Baioumy et al., 2013, 2014). It has been found that hydrothermal deposits are depleted in Co, Ni and Cu, while they are enriched in other hydrothermal elements such as Zn, Pb, Mo, V, and As relative to hydrogenous deposits (Hewett et al., 1963; Nicholson, 1992; Boyd and Scott, 1999). Oolitic iron ores from Aswan are plotted within the hydrogenous field in Fig. 14B and C, respectively. The direct precipitation of the studied iron ores (hydrogenous) requires high Fe in the seawater although the dissolved Fe in the brine is too low (~4 ppb). The high dissolved Fe contents in the seawater during the precipitation of the Aswan iron ores could be due to the weathering of adjacent continental masses. The abundance of detrital quartz and the positive correlations between most of the major and trace elements with TiO2 and Al2O3 contents support the detrital source of the dissolved Fe in the seawater. Many shales and ferruginous mudstones intervals of detrital origin intercalated with the iron ores may also support this interpretation. The geology and stratigraphy of the studied area indicate that it is comprised of the Precambrian basement rocks

H. Baioumy et al. / Ore Geology Reviews 80 (2017) 185–199

195

Fig. 10. (A and B) Positive correlations between SiO2 and trace elements. (C and D) Positive correlations between Al2O3 and trace elements. (E and F) Positive correlations between TiO2 and trace elements. (G) Positive correlations between P2O5 and trace elements. (H) Positive correlations between MnO and trace elements.

that are covered by the late Cretaceous sedimentary sequence. It means that the study area represents productive land under threat from erosion, and the uplifted Precambrian basement rocks were subjected to intensive lateritization from the Cambrian late Cretaceous, which supplied huge amounts of sediments and iron to the depositional basin. 5.2. Origin of apatite Two mechanisms could interpret the origin of apatite in the oolitic iron ores in Egypt. The first mechanism includes the authigenic

formation of apatite as direct precipitation from P- and Ca-rich solution by what is called iron-redox model (Heggie et al., 1990; O'Brien et al., 1990; Glenn, 1990; Jarvis et al., 1994). The second mechanism suggests the reworking of preexisting apatite grains that can be of sedimentary or igneous origin. The authigenic (sedimentary) apatite is carbonatefluorapatite (francolite) (Knudsen and Gunter, 2002; Baioumy et al., 2007) and is characterized by capsule-like structure (Baioumy and Tada, 2005; Al-Hobaib et al., 2013). Alternatively, apatite of igneous origin occurs mainly as fluorapatite, hydroxyapatite, and chlorapatite (Piccoli and Candela, 2002).

196

H. Baioumy et al. / Ore Geology Reviews 80 (2017) 185–199

Table 4 Distribution of rare earth elements (ppm) in representative oolitic iron ore samples from Aswan area measured by ICP-MAS. Samples

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Sum (La/Yb)N Eu/Eu* Ce/Ce*

Wadi Abu Sobera

Wadi Abu Agag

Um Hebal

WAS1

WAS2

WAS3

WAA1

WAA2

WAA3

WAA4

UMH1

UMH2

UMH3

88.9 190.9 24.91 116 29.02 8.14 38.2 6.07 35.08 6.42 17.34 2.12 11.35 1.49 575.90 5.32 0.75 0.92

33.1 83.4 11.17 53.8 14.2 4.26 16.38 2.68 14.83 2.63 7.3 1.04 6.51 0.98 252.28 3.45 0.85 1.02

51.5 140.7 17.22 74.9 18.47 5.36 20.84 3.38 19.66 3.68 10.44 1.46 8.44 1.17 377.22 4.15 0.83 1.14

54.5 157 20.94 98.5 24.54 6.62 25.89 4.13 22.65 4.16 11.2 1.5 8.66 1.16 441.45 4.28 0.80 1.13

33.7 85.3 11.19 53.6 13.42 3.73 17.09 2.77 14.33 2.68 6.81 0.86 4.95 0.71 251.1 4.62 0.75 1.03

20.2 50.7 5.84 24 5.47 1.46 5.73 1.01 5.97 1.26 3.41 0.54 3.39 0.5 129.48 4.05 0.79 1.11

31.9 125.9 14.3 71.4 21.6 7.54 30.56 5.09 26.34 4.31 10.33 1.34 7.51 0.97 359.09 2.89 0.89 1.44

52.5 142 19.47 88.2 23.29 6.8 26.59 4.71 26.37 5.16 14.57 2.08 12.48 1.61 425.83 2.86 0.83 1.09

97 218.4 26.94 123.1 27.61 8.26 37.11 5.78 33 6.68 17.11 2.19 12.22 1.63 617.03 5.39 0.79 0.98

21.3 48.8 5.79 23.6 5.23 1.32 5.54 1.14 7.96 1.71 5.56 0.92 6.38 0.99 136.24 2.27 0.75 1.03

Petrographic and SEM investigations indicated that apatite in the Aswan oolitic iron ores is irregular, rounded to subrounded, massive, and structureless grains of variable sizes. Mineralogy shows that this apatite is hydroxyapatite. These evidences suggest the detrital origin of this apatite. ΣREE in the studied iron ores show strong positive correlations with P2O5 (r2 = 92), which indicates the occurrence of most if not all REE in the apatite structure. Therefore, the REE pattern should reflect the formation conditions of this apatite. In a situation where apatite in the Aswan oolitic iron ores precipitates from the seawater, it reflects the REE pattern of the seawater, being HREE enrichment and a strong negative Ce anomaly (e.g. Elderfield and Greaves, 1982; Alibo and Nozaki, 1999; Shields and Stille, 2001), which is not the case in this study. Moreover, the studied apatite shows REE pattern similar to that of the apatite from the granites, for the enrichment of LREE compared with the HREE and negative Eu anomalies (Ding et al., 2015). This development supports the detrital origin of the apatite in the Aswan oolitic iron ores, which is probably derived from igneous rocks. Precambrian igneous rocks (granites, granodiorites, quartz diorites, gneiss, gabbros) are common in the Aswan area close to the studied iron ores (e.g. Liégeois and Stern, 2010; Kuster and Liegeois, 2001; Ali et al., 2009). 5.3. Implications for phosphorus removal Oolitic iron ore deposits in Aswan area has been discovered since long time ago, and several attempts were made to utilize the ores in the iron and steel making industries in Egypt. However, the presence of phosphorus in such high concentrations and the poor liberation of iron minerals from the gangues discouraged the exploitation of the deposits. The determination of concentration and mode of occurrence of phosphorus in the Aswan iron ores in the present study could provide a platform for designing physical, chemical and/or biological process(es) to minimize the phosphorus content in the ore and match the standard P2O5 content in the iron and steel making industries. Possible physical separation methods of apatite from the Aswan iron ores include magnetic separation, gravity method and floatation. In these processes, liberation size of apatite is crucial (Wills and NapierMunn, 2006). Biotechnological processes include bioleaching or biobeneficiation using bacteria (Ehrlich, 1998; Ehrlich and Newman, 2009). Bacterial leaching of ore components may involve a direct or an indirect process, or both of the interactions. In a direct process, the active bacteria attack the ore surface and mobilize (solubilize) the constituent of interest, usually by oxidizing or reducing enzymatically. In an indirect process, the active bacteria produce one or more metabolic products (one or more acids), which attack the ore and thereby mobilize the constituent of interest by a non-enzymatic chemical reaction.

In the case of apatite, the phosphate is usually mobilized in an indirect process by metabolically produced acid (Ehrlich, 1998; Ehrlich and Newman, 2009). Results of the current study indicated that hydroxyapatite occurs in sizes ranging between 5–150 μm. Therefore, employment of both physical and biological methods to separate apatite and then minimize the P2O5 contents requires grinding these ores up to 5 μm. Previous research works attempted to liberate the gangues but lacked information about the grain size and mode of occurrence of Pbearing minerals in the Aswan oolitic iron ores. This study shows that the insufficient information is probably due to the difficulties in identifying and characterizing the apatite in the iron ores under the optical microscope as a result of strong staining of apatite grains by hematite and the similarity in optical properties of apatite with quartz. Also, fine-grained apatite was not identified using the optical microscope, but by the application of SEM only. Therefore, SEM could be more efficient in the characterization of apatite in the iron ores from Aswan. 6. Conclusions High-P oolitic iron ores from Aswan, Egypt, were subjected to detailed petrographic, mineralogical, and geochemical investigations to examine their origin in addition to the texture and origin of P-bearing minerals. The appraisals indicated that these ores were formed in open space near the sediment-water interface by accretion of FeO,

Fig. 11. Positive correlation between P2O5 and ΣREE.

H. Baioumy et al. / Ore Geology Reviews 80 (2017) 185–199

Fig. 12. Chondrite-normalized REE patterns (using Chondrite REE concentrations provided by Boynton (1984)) of the oolitic iron ores at the Wadi Abu Agag (A), Wadi Abu Sobeira (B) and Um Hibal (C) areas.

197

Fig. 14. Oolitic iron ores are plotted in the field of hydrogenous of (A) Si-Al discrimination diagram of Choi and Hariya (1992), (B) Plot of the oolitic iron ores in the (Ni + Co) versus (As + Cu + Mo + V + Zn) discrimination diagram (Nicholson, 1992) and (C) (Co + Ni + Cu) versus Co/Zn binary plot of Toth (1980).

Fig. 13. Cartoon shows the evolution and formation mechanism of ooids in the Aswan oolitic iron ores. (A) Seawater is saturated with cations and anions especially Fe, Si and Al. (B) Precipitation of these cations and anions as hematite and chamosite over nucleus at the water-sediments interface. (C) Development of the hematite and chamosite as discontinuous laminae. (D) Complete formation of ooids in concentric (elliptical and spherical shapes) or eccentric textures. (E) Some ooliths were broken by local currents before they were buried in the sediment.

198

H. Baioumy et al. / Ore Geology Reviews 80 (2017) 185–199

SiO2, Al2O3, and minor amounts of other oxides around solid particles such as quartz and parts of broken ooliths. The fairly uniform size of the ooliths reflects sorting due to the current action. The geochemistry of major and trace elements in the ores reflects their marine (hydrogenous) origin. The oolitic iron ores of marine origin are confined to the Timsha Formation, which is bounded by the non-marine Turonian Abu Agag and Santonian-Campanian Um Barmil formations indicating a transgressive phase of the Tethys into southern Egypt during the Coniacian-Santonian. The abundance of detrital quartz, positive correlations between most of the major and trace elements and TiO2 and Al2O3 contents, and the abundance of shales and ferruginous mudstone intervals within the iron ores support the detrital source of Fe in the seawater. This development is the result of adjacent continental masses weathering from the Cambrian to the Upper Cretaceous. Phosphorus in these ores occurs in higher concentrations compared to the limit of P in the steel. It is present as massive and structureless hydroxyapatite grains of undefined outlines and variable size (5–150 μm) inside the ooids and/or in the ferruginous groundmass. The REE patterns, which occur entirely in the apatite structure, exhibit a pattern similar to those in the granites. These features suggested the detrital origin of the hydroxyapatite that was probably derived from the Precambrian igneous rocks in the study area. Determination of the mode of occurrence and grain size of P-bearing mineral (hydroxyapatite) will support the optimum utilization of both physical and biological separation of P from the Aswan iron ores and thus encourage the use of these ores as raw materials in the iron making industry.

References Abro, M.M., Pathan, A.G., Mallah, A.H., 2011. Liberation of oolitic hematite grains from iron ore, Dilband Mines Pakistan. Mehran Univ. Res. J. Eng. Technol. 30, 329–338. Al-Hobaib, A.S., Baioumy, H.M., Al-Ateeq, M.A., 2013. Geochemistry and origin of the Paleocene phosphorites from the Hazm Al-Jalamid area, northern Saudi Arabia. J. Geochem. Explor. 132, 15–25. Ali, K.A., Stern, R.J., Manton, W.I., Kimura, J.I., Khamees, H.A., 2009. Geochemistry, Nd isotopes and U-Pb SHRIMP zircon dating of Neoproterozoic volcanic rocks from the Central Eastern Desert of Egypt: new insights into the ~750 Ma crust-forming event. Precambrian Res. 171, 1–22. Alibo, D.S., Nozaki, Y., 1999. Rare earth elements in seawater: particle association, shalenormalization and Ce oxidation. Geochim. Cosmochim. Acta 63, 363–372. Baioumy, H.M., Tada, R., 2005. Origin of upper cretaceous phosphorites in Egypt. Cretac. Res. 26, 261–275. Baioumy, H.M., Tada, R., Gharaie, M.H.M., 2007. Geochemistry of late Cretaceous phosphorites in Egypt: implication for their genesis and diagenesis. J. Afr. Earth Sci. 49, 12–28. Baioumy, H.M., Khedr, M.Z., Ahmed, A.H., 2013. Mineralogy, geochemistry and origin of Mn in the high-Mn iron ores, Bahariya oasis. Ore Geol. Rev. 53, 63–76. Baioumy, H.M., Ahmed, A.H., Khedr, M.Z., 2014. A mixed hydrogenous and hydrothermal origin of the Bahariya iron ores, Egypt: evidences from the trace and rare earth element geochemistry. J. Geochem. Explor. 146, 149–162. Bhattacharyya, D.P., 1989. Concentrated and lean oolites. Examples from the Nubia formation at Aswan, Egypt, and significance of the oolite types in ironstone genesis. In: Young, T.P., Taylor, W.E.G. (Eds.), Phanerozoic Ironstones 46. Geological Sociey London Special Publication, pp. 93–103. Boyd, T., Scott, S.D., 1999. Two-XRD-line ferrihydrite and Fe-Si-Mn oxyhydroxide mineralization from Franklin Seamount, western Woodlark Basin, Papua New Guinea. Can. Mineral. 37, 973–990. Boynton, W.V., 1984. Geochemistry of the REE: meteorite studies. In: Henderson (Ed.), Rare Earth Element Geochemistry. Elsevier, pp. 63–114. Bubenicek, L., 1968. Geologie des minerals de fer oolithiques. Mineral. Deposita 3, 89–108. Champetier, Y., Hamdadou, E., Hamdadou, M., 1987. Examples of biogenic support of mineralization in two oolitic iron ores—Lorraine (France) and Gara Djebilet (Algeria). Sediment. Geol. 51, 249–255. Choi, J.H., Hariya, Y., 1992. Geochemistry and depositional environment of Mn oxide deposits in the Tokoro Belt, northeastern Hokkaido, Japan. Econ. Geol. 87, 1265–1274. Delvasto, P., Ballester, A., Muñoz, J.A., González, F., Blázquez, M.L., Igual, J.M., Valverde, A., García-Balboa, C., 2009. Mobilization of phosphorus from iron ore by the bacterium Burkholderia caribensis FeGL03. Miner. Eng. 22, 1–9. Ding, T., Ma, D., Lu, J., Zhang, R., 2015. Apatite in granitoids related to polymetallic mineral deposits in southeastern Hunan Province, Shi–Hang zone, China: implications for petrogenesis and metallogenesis. Ore Geol. Rev. 69, 104–117. Doering, T., 1990. Die Genese der oolithischen Eisenerze von Assuan in Ober Agypten. Eine erzmikroskopisch mikroanalytische Untersuchung (Ph.D, dissertation) Georgmikroanalytische Untersuchung. Georg-August-Universitat, Gottingen, Germany (Ph.D, dissertation). (185p). Ehrlich, H.L., 1998. Geomicrobiology: its significance for geology. Earth-Sci. Rev. 45, 45–60.

Ehrlich, H.L., Newman, D.K., 2009. Geomicrobiology. Taylor and Francis Group, Boca Raton London New York, p. 630. El Aref, M.M., El Sharkawi, M.A., Mesaed, A.A., 1996. Depositional and diagenetic microfabric evolution of the cretaceous oolitic ironstone of Aswan Egypt. 2. Geological Society Special Publication, Egypt, pp. 279–312. El Sharkawi, El Aref, M.M., Mesaed, A.A., 1996. Stratigraphic setting and paleoenvironment of the Coniacian-Santonian ironstones of Aswan, south Egypt. 2. Geological Society Egypt Special Publication, pp. 243–278. Elderfield, H., Greaves, M.J., 1982. The rare earth elements in seawater. Nature 296, 214–219. Elliott, J.C., Wilson, R.M., Dowker, S.E.P., 2002. Apatite structures. International centre for diffraction data 2002. Adv. X-ray Anal. 45, 172–181. Ghazaly, M.K., El Afandy, A.H., Fawzy, K.M., Fahmy, M.A., 2015. The pegmatitic rocks of ElHudi and Um Hibal areas, Southeastern Desert, Egypt: genesis and petrological characteristics. Arab. J. Geosci. 8, 161–186. Glenn, C.R., 1990. Depositional sequence of the Duwi, Sibaiya and phosphate formations, Egypt: phosphogenesis and glauconitization in a late Cretaceous epeiric sea. In: Notholt, A.J.G., Jarvis, I. (Eds.), Phosphorite Research and Development 52. Geological Soceity Special Publication, pp. 205–222. Gordon, R.B., 1996. American Iron 1607–1900. The Johns Hopkins University Press. Business and Economics, p. 341. Heggie, D.T., Skyring, G.W., O'Brien, G.W., Reimers, C., Herczeg, A., Moriary, D.J.W., Burnett, W.C., Milnes, A.R., 1990. Organic carbon cycling and modern phosphorite formation on the east Australian continental margin: an overview. In: Notholt, A.J.G., Jarvis, I. (Eds.), Phosphorite Research and Development 52. Geological Society Special Publication, pp. 87–117. Hein, J.R., Schulz, M.S., Kang, J.K., 1990. Insular and submarine ferromanganese mineralization of the Tongap-Lau region. Mar. Mineral. 9, 305–354. Hemingway, J.E., 1974. Jurassic. In: Raynor, D.H., Hemingway, J.E. (Eds.), The geology and mineral resources of Yorkshire. Yorks. Geol. Soc., pp. 161–223 Hewett, D.F., Fleischer, M., Conklin, N., 1963. Deposits of the manganese oxides: supplement. Econ. Geol. 58, 1–51. Hussein, A.A.A., Sharkawi, M.A.E., 1990. Mineral deposits. In: Said, R. (Ed.), The Geology of Egypt 1. A.A. Balkema Publishers, Rotterdam, Netherlands, pp. 511–566. Jarvis, I., Burentt, W.C., Nathan, Y., Almbaydin, S.M.F., Attia, A.K.M., Castro, L.N., Flicoteaux, R., Hilmy, M.E., Husain, V., Qutawah, A.A., Serjani, A., Zanin, Y.N., 1994. Phosphorite geochemistry: state-of-the-art and environmental concern. Concepts and Controversies in Phosphogenesis. Proceeding of the Symposium and Workshop held on 6–10 September 1993 Switzerland, pp. 643–700. Jenner, G.A., Longerich, H.P., Jackson, S.E., Fryer, B.J., 1990. ICP-MS-A powerful tool for high-precision trace-element analysis in earth sciences: evidence from analysis of selected U.S.G.S. reference samples. Chem. Geol. 83, 133–148. Klitzsch, E., 1986. Plate tectonics and cratonal geology in Northeast Africa (Egypt, Sudan). Geol. Rundsch. 75, 755–768. Knudsen, A.C., Gunter, M.E., 2002. Sedimentary phosphorites—an example: phosphora formation, southeastern Idaho, U.S.A. In: Kohn, M.J., Rakovan, J., Hughes, J.M. (Eds.), Reviews in Mineralogy and Geochemistry. Phosphates: geochemical, geobiological, and materials importance 48, pp. 363–389. Li, K., Ni, W., Zhu, M., Zheng, M., Li, Y., 2011. Iron extraction from oolitic iron ore by a deep reduction process. J. Iron Steel Res. Int. 18, 9–13. Liégeois, J.P., Stern, R.J., 2010. Sr-Nd isotopes and geochemistry of granite-gneiss complexes from the Meatiq and Hafafit domes, Eastern Desert, Egypt: no evidence for pre-Neoproterozoic crust. J. Afr. Earth Sci. 57, 31–40. Mackie, P.E., Elliott, J.C., Young, R.A., 1972. Monoclinic structure of synthetic Ca5(PO)3Cl, chlorapatite. Acta Crystallogr. 28, 1840–1848. Manieh, A.A., 1984. Oolite liberation of oolitic iron ore, Wadi Fatima, Saudi Arabia. Int. J. Miner. Process. 13, 187–192. Meshref, W.M., 1990. Tectonic framework. In: Said, R. (Ed.), The Geology of Egypt. AA Balkema, Rotterdam, Brookfield, pp. 113–156 (Chapter 8). Mucke, A., 2000. Environmental conditions in the Late Cretaceous African Tethys: conclusions from a microscopic-microchemical study of ooidal ironstones from Egypt, Sudan and Nigeria. J. Afr. Earth Sci. 30, 25–46. Nicholson, K., 1992. Contrasting mineralogical-geochemical signatures of manganese oxides: guides to metallogenesis. Econ. Geol. 87, 1253–1264. O'Brien, G.W., Milnes, A.R., Veeh, H.H., Heggie, D.T., Riggs, S.R., Cullen, D.J., Marshall, J.F., Cook, P.J., Jarvis, I., 1990. Sedimentation dynamics and redox iron-cycling controlling factors for the apatite-glauconite association on the east Australian continental margin. In: Notholt, A.J.G. (Ed.), Phosphorite Research and Development 52. Geological Society Special Publication, pp. 61–86. Omran, M., Fabritius, T., Mattila, R., 2015. Thermally assisted liberation of high phosphorus oolitic iron ore: a comparison between microwave and conventional furnaces. Powder Technol. 269, 7–14. Ozdemir, O., Deutsch, E.R., 1984. Magnetic properties of oolitic iron ore on Bell Island, new found land. Earth Planet. Sci. Lett. 69, 427–441. Petruk, W., 1977. Mineralogical characteristics of an oolitic iron deposit in the Peace River District, Alberta. Can. Mineral. 15, 3–13. Piccoli, P.M., Candela, P.A., 2002. Apatite in igneous systems. Rev. Mineral. Geochem. Mineral. Soc. Am. 48, 255–292. Shah, M.T., Moon, C.J., 2014. Mineralogy, geochemistry and genesis of the ferromanganese ores from Hazara area, NW Himalayas, northern Pakistan. J. Asian Earth Sci. 23, 1–15. Shields, G., Stille, P., 2001. Diagenetic constraints on the use of cerium anomalies as palaeoseawater redox proxies: an isotopic and REE study of Cambrian phosphorites. Chem. Geol. 175, 29–48. Song, S., Campos-Toro, E.F., Valdivieso, A.L., 2013. Formation of micro-fractures on an oolitic iron ore under microwave treatment and its effect on selective fragmentation. Powder Technol. 243, 155–160.

H. Baioumy et al. / Ore Geology Reviews 80 (2017) 185–199 Sturesson, U., 1995. Llanvirnian (Ord.) iron ooids in Baltoscandia: element mobility, REE distribution patterns, and origin of the REE. Chem. Geol. 125, 45–60. Sturesson, U., 2003. Lower Palaeozoic iron oolites and volcanism from a Baltoscandian perspective. Sediment. Geol. 159, 241–256. Toth, J.R., 1980. Deposition of submarine crusts rich in manganese and iron. Geol. Soc. Am. Bull. 91, 44–54. Usui, A., Someya, M., 1997. Distribution and composition of marine hydrogenetic and hydrothermal manganese deposits in the northwest Pacific. In: Nicholson, K., Hein, J.R., Buhn, B., Dasgupta, S. (Eds.), Manganese Mineralization: Geochemistry and Mineralogy of Terrestrial and Marine Deposits 119. Geological Society London Special Publication, pp. 177–198.

199

Wen-tang, X., Zheng-de, R., Yi-feng, G., 2011. Removal of phosphorus from high phosphorus iron ores by selective HCl leaching method. J. Iron Steel Res. Int. 18, 1–4. Wills, B.A., Napier-Munn, T., 2006. Mineral processing technology: an introduction to the practical aspects of ore treatment and mineral. Elsevier Science and Technology Books, p. 450. Zhang, Z.C., Hou, T., Santosh, M., Li, H.M., Li, J.W., Zhang, Z.H., Song, X.Y., Wang, M., 2014. Spatio-temporal distribution and tectonic settings of the major iron deposits in China: an overview. Ore Geol. Rev. 57, 247–263.