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Geological and Mineralogical Analysis of Phosphorites in the Jebel Dhyr Syncline, Eastern Algerian Atlas

Salim Boulemia
Salim Boulemia
, 
Riheb Hadji
Riheb Hadji
, 
Salah Bouhlal
Salah Bouhlal
, 
Younes Hamed
Younes Hamed
, 
Houda Besser
Houda Besser
 and 
Kaouther Ncibi
Kaouther Ncibi
   | Dec 29, 2023
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Article Category: Original Paper
Published Online: Dec 29, 2023
Page range: 89 - 104
Received: Apr 07, 2023
Accepted: Nov 26, 2023
DOI: https://doi.org/10.2478/mipo-2023-0010
Keywords
© 2023 Salim Boulemia et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure 1.

Geographic location of the study area.
Geographic location of the study area.

Figure 2.

A: Simplified geological map of the Jebel Dhyr syncline; B: Lithostratigraphic log of Jebel Dhyr. [Legend of the geological map: 1= Holocene: Current and recent alluvium, scree slopes, piedmont accumulation, molasses. 2= Plio-Quaternary: Pebbles (sandstone and conglomerates) and marls. 3= Upper Lutetian: Marls, clays and conglomerates. 4= Ypresian, Lower Lutetian: Limestone with flint and marl-limestone, sometimes with gypsum. 5= Paleocene-Maastrichtian: Marl and marl-limestone. 6= Campanian, Maastrichtian: Marly at the base and varied limestone (oolitic, organogenic, flint) at the top. 7= Coniacian and Santonian: Limestones. 8= Turonian: Limestones and marls. 9= Cenomanian: Yellow limestone, marl and gypsum and dolomites. 10= Samples. 11= Streams. 12= Faults].
A: Simplified geological map of the Jebel Dhyr syncline; B: Lithostratigraphic log of Jebel Dhyr. [Legend of the geological map: 1= Holocene: Current and recent alluvium, scree slopes, piedmont accumulation, molasses. 2= Plio-Quaternary: Pebbles (sandstone and conglomerates) and marls. 3= Upper Lutetian: Marls, clays and conglomerates. 4= Ypresian, Lower Lutetian: Limestone with flint and marl-limestone, sometimes with gypsum. 5= Paleocene-Maastrichtian: Marl and marl-limestone. 6= Campanian, Maastrichtian: Marly at the base and varied limestone (oolitic, organogenic, flint) at the top. 7= Coniacian and Santonian: Limestones. 8= Turonian: Limestones and marls. 9= Cenomanian: Yellow limestone, marl and gypsum and dolomites. 10= Samples. 11= Streams. 12= Faults].

Figure 3.

Panoramic view of the flanks of the Jebel Dhyr syncline; A: extreme southeast flank, B: southwest flank; C: The outcrops of the ten phosphate levels (Phosphorites and Marly limestone phosphates) sampled from Jebel Dhyr Syncline.
Panoramic view of the flanks of the Jebel Dhyr syncline; A: extreme southeast flank, B: southwest flank; C: The outcrops of the ten phosphate levels (Phosphorites and Marly limestone phosphates) sampled from Jebel Dhyr Syncline.

Figure 4.

Photographs of the main allochems of Jebel Dhyr phosphorites illustrating A- Coprolith, B- Pellets, and C- Selachians Teeth.
Photographs of the main allochems of Jebel Dhyr phosphorites illustrating A- Coprolith, B- Pellets, and C- Selachians Teeth.

Figure 5.

Texture of the phosphate samples: A- Bio-pellet phosphorite with a grainstone texture, featuring allochems represented by pellets, intraclasts, and bioclasts (bivalve arc and calcitic bone fragment), [200μm]. B- Bioclasts (vertebra and fish spine) within anisotropic granular phosphorite, [100μm]. C- Phosphatized blunt-edged intraclast (granule) surrounded by pellets and glauconite, [50μm]. D- Cryptocrystalline dolomite rhombohedron with an apatitic rim surrounded by grainstone pellets of various shapes, [50μm]. E- Cylindrical-shaped coprolite and brown-colored intraclast in grainstone textured phosphorite, [100μm]. F- Detrital quartz grains and quartz rim within the calcite-filled crack, [100μm]. G- Dispersed organic matter punctuates within pellets (concentric, non-nucleated, and oval) in a calcitic matrix, [50μm]. H- Globigerina acting as nuclei for a phosphatic ooid, surrounded by non-nucleated, organic-rich oval pellets, [50μm].
Texture of the phosphate samples: A- Bio-pellet phosphorite with a grainstone texture, featuring allochems represented by pellets, intraclasts, and bioclasts (bivalve arc and calcitic bone fragment), [200μm]. B- Bioclasts (vertebra and fish spine) within anisotropic granular phosphorite, [100μm]. C- Phosphatized blunt-edged intraclast (granule) surrounded by pellets and glauconite, [50μm]. D- Cryptocrystalline dolomite rhombohedron with an apatitic rim surrounded by grainstone pellets of various shapes, [50μm]. E- Cylindrical-shaped coprolite and brown-colored intraclast in grainstone textured phosphorite, [100μm]. F- Detrital quartz grains and quartz rim within the calcite-filled crack, [100μm]. G- Dispersed organic matter punctuates within pellets (concentric, non-nucleated, and oval) in a calcitic matrix, [50μm]. H- Globigerina acting as nuclei for a phosphatic ooid, surrounded by non-nucleated, organic-rich oval pellets, [50μm].

Figure 6.

Examples of X-ray diagram for phosphorite sample show the apatitic different component with carbonates and siliceous gangue of Jebel Dhyr syncline. Abbreviations after Warr (2021; IMA–CNMNC).
Examples of X-ray diagram for phosphorite sample show the apatitic different component with carbonates and siliceous gangue of Jebel Dhyr syncline. Abbreviations after Warr (2021; IMA–CNMNC).

Figure 7.

Examples of X-ray patterns showing the presence of sulphides and sulphates in phosphorites samples from Jebel Dhyr syncline.
Examples of X-ray patterns showing the presence of sulphides and sulphates in phosphorites samples from Jebel Dhyr syncline.

Figure 8.

XRD diffractograms of fine fraction phosphorite samples from Jebel Dhyr syncline showing zeolites, feldspars and clays.
XRD diffractograms of fine fraction phosphorite samples from Jebel Dhyr syncline showing zeolites, feldspars and clays.

Figure 9.

Diffractogram of a phosphate granule sample from the Jebel Dhyr syncline.
Diffractogram of a phosphate granule sample from the Jebel Dhyr syncline.

Figure 10.

Left: Diffractogram of isolated pellets, Right: Diffractogram of isolated coprolites from the Jebel Dhyr syncline.
Left: Diffractogram of isolated pellets, Right: Diffractogram of isolated coprolites from the Jebel Dhyr syncline.

The concentration of Geochemical elements (wt%) in phosphorites (bulk rock) samples from the Jebel Dhyr syncline, Eastern Algerian Atlas.

Sample ID P2O5 CO2 MgO Na2O K2O CaO SiO2 Fe2O3 H2O Al2O3 SO3 F Tot. %
D1-I 23.17 10.7 1.84 0.71 0.13 35.1 9.7 0.66 1.62 0.77 11.85 2.6 98.85
D1-II 22.86 10.75 1.86 0.6 0.13 34.8 9.2 0.7 1.54 0.78 12.2 2.8 98.22
D1’-I 24.6 10.68 1.78 0.79 0.16 35.6 10.3 0.92 1.65 0.83 10.1 2.3 99.71
D2-II 23.4 10.65 1.8 0.7 0.15 35 9.5 0.91 1.62 0.81 11.1 3.7 99.34
D2-I 20.6 12.21 3 0.51 0.21 32 9.63 0.85 1.4 0.95 10.5 6.2 98.06
D3-II 20.2 11.8 2.7 0.55 0.21 34.2 9.05 0.82 1.5 0.93 10.6 5.9 98.46
D4-I 22.53 10.53 2.45 0.58 0.14 34.1 9.15 0.65 1.65 0.79 11.8 4.9 99.27
D4-II 20.8 11.6 2.5 0.59 0.12 33.9 9.1 0.6 1.7 0.74 11.9 4.6 98.15
D4’-I 21.9 11.7 2.9 0.6 0.11 34.1 9.1 0.55 1.75 0.72 11.95 3.2 98.58
D5-II 23.8 10.9 2.7 0.61 0.1 33.01 9.8 0.5 1.92 0.7 12.4 3.2 99.64
D6-I 24.6 12.6 2.35 0.52 0.12 32.2 9.1 0.85 1.58 0.74 10.8 3.2 98.66
D6-II 25.8 12.6 2.32 0.53 0.12 32.1 9.2 0.82 1.56 0.74 10.9 2.4 99.09
D8-I 21.8 11.33 2.69 0.6 0.17 32.7 10.6 1 1.63 0.86 12.1 4.4 99.88
D7-II 22.2 12.1 2.8 0.61 0.1 32.1 9.4 0.85 1.62 0.7 12.15 4.2 98.83

Recapitulation of mineral phases identified by light microscopy, X-ray diffraction and macroscopics observations, in phosphorites from the Jebel Dhyr syncline, Eastern Algerian Atlas.

Mineral groups encountered Sampling type
Bulk rock Phosphatic allochems grains
apatite (hydroxylapatite, fluorapatite, francolite, dahllite*) ++ ++
Carbonates (calcite, dolomite, magnesian calcite*, ankerite*, dawsonite*) ++ --
Sulfates (gypsum) + --
Sulfides (pyrite*-cinnabar*-covellite*) + --
Tectosilicates (quartz) ++ +
Tectosilicates (feldspar, zeolite*) + --
Clays (palygorskite*) ++ --
Native element (graphite) + --

Crystallographic parameters of the crystalline unit cell of apatite group in phosphorites from the Jebel Dhyr syncline, Eastern Algerian Atlas.

Mineral a or b (Å) C (Å) c/a Vol. of unit cell Chemical formula
fluorapatite 9.371 6.885 0.734 523.12 Ca5(PO4)3F
hydroxylapatite 9.352 6.882 0.735 521.26 Ca5(PO4)3(OH)
francolite 9.340 6.880 0.736 519.77 (Ca,Mg,Sr,Na)10(PO4,SO4,CO3)6F2-3
dahllite 9.450 6.885 0.725 532.09 Ca5(PO4,CO3)3(OH,O)

Comparative X-ray diffraction parameters (dhkl) of apatite group from phosphorites deposits in North Africa.

(hkl) (Miller index) dhklof peaks (Å)
J. Jebs, Tunisia (Beji-Sassi 1984) Foum Selja,Tunisia (Chaabani 1978) Morocco (El Haddi 2014) Dhyr, Algeria (this study)
100 8.164 8.15 8.074 8.099
101 5.281 5.29 5.250 5.244
200 4.052 4.04 4.041 4.049
111 3.873 3.87 3.862 3.867
002 3.456 3.45 3.444 3.441
102 3.183 3.17 3.170 3.167
120 3.062 3.05 3.051 3.061
211 2.792 2.79 2.792 2.796
112 --- 2.78 2.771 2.771
300 2.695 2.69 2.693 2.699
202 2.627 2.62 2.622 2.622
301 2.507 2.51 2.510 2.513
122 2.284 2.28 2.282’ 2.287
310 2.240 2.24 2.240 2.240
131 2.130 2.13 2.131 2.135
113 2.062 2.07 2.061 2.059
203 1.997 --- 1.996 1.995
222 1.931 1.93 1.930 1.933
132 1.879 1.87 1.880 1.880
123 1.836 1.84 1.836 ---
231 1.788 1.77 1.790 1.790
410 1.762 1.76 1.765 1.766
303 1.741 1.73 1.743 ---
004 1.722 1.71 1.723 1.720
322 --- --- 1.632 1.634

X-ray diffraction parameters of carbonate group in phosphorites from Djebel Dhyr syncline, Eastern Algerian Atlas.

Mineral hkl d (Å) 2Θ [deg] Geochemical formula
calcite 104 3.0360 29.395 CaCO3
magnesian calcite 104 3.0254 29.500 (CaMg)CO3
dolomite 104 2.8893 30.815 CaMg(CO3)2
ankerite 104 2.8890 30.918 Ca(Fe,Mg)
(CO3)2
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