Main Subjects : Geochemistry

Assessment of Limestone of Jeribe Formation for Ordinary Portland Cement Industry in Bekhair Anticline, Duhok Governorate, Iraqi Kurdistan Region

Hasan Abd Khudhur; Ahmed M. Aqrawi

Iraqi National Journal of Earth Science, 2022, Volume 22, Issue 2, Pages 90-104
DOI: 10.33899/earth.2022.135129.1022

The limestone of Jeribe Formation in Bekhair anticline, Duhok Governorate, was assessed as raw materials for the Ordinary Portland Cement (OPC) industry. Four sections were selected; the formation consists of fossiliferous limestone and thin layers of dolomitic limestone. The petrographic study showed that the main mineral of limestone rocks is fine calcite with a size less than 0.25 cm. The chemical analysis revealed that the mean concentration of CaO is 51.77% which dominates over other oxides, including MgO (2.06%), SiO2 (1.95%), Al2O3 (0.60%), and, Fe2O3 (0.22%), While the remaining oxides (K2O, Na2O, TiO2, MnO, P2O5, and SO3) are present in traces. The lime saturation factors (LSF) of the studied sections range from (1651.70 to 2334.89), which are over the limits necessary for high-quality cement; thus, a claystone rock from the Fatha Formation was added to achieve the best point of clinker LSF. The physical and mechanical tests of samples indicate low porosity, and the compressive strength range between (168-1291 kg/cm²), which are acceptable for the cement industry and make the rocks easy to crush and grind during the preparation of the mixture. According to the results of the analyses, we conclude that the mixture of limestone ranges between (65.9-69.3) and claystone ranges between (30.7-34.1) in the study area are of good quality and meet international standards for ordinary portland cement.

Geochemical Parameters for Evaluating the Aptian-Albian Kaolin Deposits at Abu Darag Region, Gulf of Suez: Implications for the Paleoclimatic Conditions in the Depositional Environments

Hatem El Desoky; Mohamed Wageeh Abdel Moghny; Nabil Ali Abdel Hafez; Osama Ramzy El-Shahat; Sherif Farouk; Hossam Sharaka

Iraqi National Journal of Earth Science, 2022, Volume 22, Issue 2, Pages 67-89
DOI: 10.33899/earth.2022.135180.1025

The mineralogical and geochemical constituents of the Aptian-Albian Malha Formation at the Abu Darag region, Gulf of Suez, Egypt, can be discussed here. These constituents are related to paleoweathering and paleoclimatic circumstances that managed the depositional settings. The present study aims to evaluate the geochemical conditions that have control over the depositional environments and characterizes them in terms of lithological, mineralogical, and chemical composition. To achieve this aim, selected kaolinitic clay samples were geochemically and mineralogically examined. Kaolinite and quartz are the main constituent minerals in the investigated samples, whereas anatase and hematite serve as auxiliary minerals. The presence of hematite minerals indicates precipitation in an oxidizing environment, whereas anatase is related to basaltic rock. Bivariate discrimination provenance diagrams, major oxides, and trace elements all identify felsic-intermediate igneous source rocks as the leading contenders. The examined samples were deposited in non-marine environments and underwent weak to moderate chemical weathering as well as severe physical induration in tropical climates.

An Industrial Evaluation and Chemical and Physical Properties of the Clay from the Taq Taq Area in Northern Iraq for some Ceramic Applications

Zirak Yaseen; Ahmed M. Aqrawi; Idrees N. Ahmed

Iraqi National Journal of Earth Science, 2022, Volume 22, Issue 2, Pages 47-66
DOI: 10.33899/earth.2022.134616.1018

Claystone beds exposed in the Mukdadiyah (Lower Bakhtiyary) and Injana (Upper Fars) Formations at Taq Taq in the Kurdistan Region-North of Iraq will be used in this study for Ceramic Industry. The estimation of qualitative variation of Clay beds is dependent on the chemical, physical, and mechanical properties of the ceramics industry. The claystone is sandy mud composed of 49-58% clay, 22.6 – 31.6% silt, and 10.4-31.4% sand. Linear shrinkage was seen in the Fired claystone specimens between - 0.23 to 4.32
%. bulk density 1.02 – 1.42 gm/cm3, and the efflorescence is varied from nil to Heavy. The main constituents of the investigated clays are SiO2, CaO, and Al2O3 ranging between (39.4 -43.3%,11.6-16.32%, and 8.52-10.17%) respectively. A significant amount of Fe2O3 is recorded in the samples, ranging from 4.87 – 6.02%. As per Iraqi Standard Standards No. 25, the claystone of the studied area is an appropriate content for the construction of pierced and conventional bricks in classes B and A for the wall tiles are class B3, Grade 2 and 3 for Roofing tiles.

Calculation of Mineralogical and Chemical Weathering Indices (Xd, MIA and CIA) and their Significance in Soils at Selected Areas in Northern Iraq

Muhamad Aswad

Iraqi National Journal of Earth Science, 2022, Volume 22, Issue 1, Pages 1-14
DOI: 10.33899/earth.2022.174660

This study is conducted using data analysis of minerals gained from X-ray diffraction (XRD) as well as by using the data of chemical analysis of the main elements measured by the X-ray Fluorescence (XRF) at selected areas in northern Iraq Thirty samples (twenty soil and ten rock samples) are collected distributed through five regions (Qayarah, Hamam Alil, Tel kaif, Duhok, and Zakho) with four depths and two rock samples for each section in order to calculate the index of weathering mineral (Xd) and mineralogy index of alteration (MIA) as well as chemical index of alteration (CIA). The aim is to measure the amount of decomposition relative to the resistant minerals in soils and rocks, as well as to assess the amount and capability of these soils as evidence of the degree of development, and then the possibility of classification depending on the degree of resistance to weathering processes. The results show transaction weathering in these areas varying in degree and ability of these soils in resisting weathering processes at different locations and the nature of the original material. The study shows that Zakho soil samples have a high degree of weathering; on the contrary, Qayarah soil samples have a very low degree of weathering due to different topographical and climatic conditions of these two regions. The remaining areas are intermediate in the degree of weathering, considering that these areas have received variable amounts of rain precipitation ranging between 1,000 mm / year as in Zakho and 250 mm / year in Qayarah area. The topography of these areas is different being high in Zakho and low in Qayarah area

Mineralogy and Geochemistry of Qulqula Limestone in Shenrui, Halabja Governorate, Northeastern Iraq

Nian Samin

Iraqi National Journal of Earth Science, 2021, Volume 21, Issue 2, Pages 1-14
DOI: 10.33899/earth.2021.170382

      This study focuses on the mineralogy and geochemistry of the limestone unit of the Qulqula Formation (Early Cretaceous). The age and stratigraphic position of this formation are controversial because of insufficient studies and the complex structure of the occurrence area. Twenty samples were selected and analyzed which represent six sections: Sarkan, Awera, Griana1, Griana2, Hawar, and Hawara Kon at the Mount of Shenrui in Halabja area located in Kurdistan Region, northeastern Iraq near the Iraqi-Iranian borders. The mineralogical study by the X-ray diffraction technique shows that the samples are composed of 70.14 % calcite, and 28.07% quartz. The geochemical analysis shows that CaO is abundant in most of the studied samples, the increases of (SiO2, Al2O3, Fe2O3, TiO2, and K2O), and the decrease in (CaO and MgO) leads to the change of limestone to siliceous type. The limited dolomitization can be confirmed by the low concentration. The component Sr has a negative correlation for both major and trace elements. On the other hand, (Cr, Co, Ni, V, and Zr) have a positive correlation with (MgO, Fe2O3, SiO2, Al2O3, K2O, and TiO2), thismay indicate the effect of the basic rocks in surrounding areas enriching limestone with these elements.

Assessment of Avroman Limestone Formation for Portland Cement Industry, Halabja Area, Kurdistan Region, NE-Iraq

Chro Fatah; Tola Mirza

Iraqi National Journal of Earth Science, 2021, Volume 21, Issue 2, Pages 29-48
DOI: 10.33899/earth.2021.170384

Limestone is the main constituent of the raw materials used in manufacturing cement. In this study, the limestone deposits from the Avroman Formation are evaluated by using chemically and mineralogical techniques for their suitability to be used as a raw material for the cement industry.
Twenty-one samples of limestone are collected from different beds of the Avroman Formation for petrographic study which shows that the limestone samples consist mainly of crystalline calcite. Physical and mechanical tests are performed in addition to the mineralogical and geochemical analysis using x-ray diffraction (XRD), x-ray fluorescence (XRF). Geological review and obtained results show that there is a good potential for industrial-grade limestone. The major clay minerals in the clay samples are chlorite, illite, montmorillonite, were as kaolinite appears as minor clay minerals. The geochemical analysis indicates that the limestone of Avroman formation has a wide range of CaO (46.13-56.00), Al2O3 (0.01-0.86), SiO2 (0.00-1.51), Fe2O3 (0.00-1.25), MgO (0.24-0.71), K2O, Na2O, TiO2, and MnO are traces. The physical properties (water absorption and moisture content) and chemical-mineralogical composition of the formation reflect that the dry process is preferable for the production of Portland cement. Mechanical analyses, especially compressive strength show that the quarrying and crushing will be competitive economically during manufacturing. From the results of the analyses, we conclude that the limestone of the formation and clay material of the study area are of good quality and fulfill the international standards of Portland cement.

Study of the Mineral and Chemical Variation of the Raw Material Mix Used for Production of the Clinker and the Sulfate Resistant Portland Cement of Al-Hadbaa Plant, Hammam Al-Alil, Iraq

Safaa Al-Jubouri; Sahra Al-Maadhidee

Iraqi National Journal of Earth Science, 2021, Volume 21, Issue 2, Pages 27-42
DOI: 10.33899/earth.2021.170389

Twenty-four samples (6 samples of raw material mix slurry, 9 samples of cement clinker, 9 samples of sulfate resistant cement) are collected during four months from the production line of Al-Hadbaa Cement Plant, which operates in a wet production method, in Hammam Al-Alil district, south of Mosul city. Some of the studied samples are analyzed for mineral diagnosis by X-ray diffraction device, chemical analysis by X-ray fluorescence device, gravimetric titrimetric chemical methods, and petrographic study for the clinker samples by reflected light microscope and using etching solutions. The research aims to study the variation of the mineral and chemical content in the studied samples.
The mineral and petrographical study show that there is no significant difference in the mineral content between the samples of the same type and that the difference is in the percentage of the presence of minerals. The raw materials mix mainly contains calcite and quartz. As for clinker and cement, it contains a lite phase C3S with a stable growth (pure) type with a monoclinic crystal system and a type of unstable growth (impure and containing inclusions) with a trigonal crystal system. In addition to the belite phase C2S of shapes β, α, and ᾱ, the aluminate phase C3A and C12A7 type and the alkaline type containing Na, the ferrite phase C4AF and C2F and the phase of fine crystalline glass. The chemical study indicates that the content of most of the main components SiO2, Al2O3, Fe2O3, CaO, MgO, SO3, Na2O, K2O, TiO2, MnO, P2O5, Cl, and LOI for the raw materials mix, clinker, and cement are close to the samples of the same type of the studied samples. It confirms the proposed specifications by some researchers, except for the deviation in K2O, Fe2O3. It is noticed from comparing the expected clinker content with the actual clinker, as well as calculating some of the qualitative control modules (lime saturation factor, silica, and alumina modulus) to the presence of relative stability in the content of the raw mix and cement produced in the studied cement plant.

Evaluation of Sulphate Resistant Cement and Oil-well Cement Produced in Al-Hadbaa Cement Plant

Safaa Al-Jubouri; Sahra Al-Maadhidee

Iraqi National Journal of Earth Science, 2021, Volume 21, Issue 2, Pages 43-59
DOI: 10.33899/earth.2021.170391

Twenty-three samples are collected (9 samples of sulfate-resistant cement, 7 samples for each of the oil-well cement, class B and G) during four months from the production line of Al-Hadbaa cement plant, which operates in the wet production method, in Hammam Al-Alil district south of Mosul city. The research aims to evaluate the chemical and physical properties of sulfate-resistant cement and oil-well cement produced in the studied plant according to the approved standard specifications. Some of the samples are analyzed by X-ray diffraction device, and chemically by X-ray fluorescence and gravimetric titrimetric chemical methods. The results of physical tests are obtained (fineness by Blaine method and sieves, water-cement ratio, setting time (initial and final), soundness by autoclave method, and compressive strength) for cement of three types according to the requirements of the Iraqi Standard Specification (no.5, 1984). As well as the results of physical tests (mixing water percent, fineness, slurry density, thickening time, free fluid content, compressive strength, and dry cement density) for oil-well cement are according to the requirements of the American Petroleum Institute specifications for the samples taken from Al-Hadbaa cement plant, which is carried out within the requirements of quality control overproduction.
The study concludes that the results of chemical analysis, calculating some of the chemical moduli, percent of mineral phases, and results of physical tests for three types of cement are close in their values, ​​and conforming to the limits of chemical and physical requirements of the Iraqi Standard Specification (no.5, 1984). Except that the aluminate phase C3A content, which is more than the required limit. The results of chemical analysis, calculating the percent of mineral phases, and the results of physical tests for the studied oil-well cement are in conformity to the limits of chemical and physical requirements of the American Petroleum Institute Specifications (API 10A, 2010), for the cement type of moderate resistant for sulfate (class B and G). Except for the values ​​​​of alite phase C3S content, and alkalis (sodium) equivalent Na2OEQ for class G, which are not conforming to specifications.

Factors Controlling the Mineralogical and Geochemical Distribution of Phosphatic Deposits, Western Iraqi Desert

Kotayba Al-Youzbakey

Iraqi National Journal of Earth Science, 2021, Volume 21, Issue 1, Pages 20-41
DOI: 10.33899/earth.2021.170379

The Iraqi phosphorites distributed in western desert belong to Tethys phosphorites. They are found in Al-Rutba- H3, Al-Ga'ara, Akashat, and Al-Ethna and in the western wadi Aakash areas.
The statistical factor analysis shows that the main five factors playing great roles in phosphate formation in the congenital shelf are the more active factors that control the mineralogical and geochemical distributions in phosphorites; they are (1) Phosphorus enrichment factor, which led to apatite (francolite) formation. (2) Depositional environment factor, which represents the deposition of phosphates in continental shelf of the southern part of Tethys Sea. (3) Mg withdrawing from sea water, the factor which controlled by clay mineral transportation like palygorskite and some dolomite that contributes to form apatite. (4) The slightly increased saline factor. (5) The cyclic alternative deposition factor, which represents the sequence deposition of phosphates, carbonates and cherts periodically.

Assessment of Limestone of Ibrahim Formation in Zurbatiya Area, Eastern Iraq for Ordinary Portland Cement Industry

Narjis Al-Ali; Sattar Al-Khafaji

Iraqi National Journal of Earth Science, 2020, Volume 20, Issue 2, Pages 19-32
DOI: 10.33899/earth.2020.170358

Limestone deposits of Ibrahim Formation in Zurbatiya area, eastern Iraq are assessed as raw materials for the industry of Ordinary Portland Cement (OPC). The deposits are widely exposed in the area close to Iraq-Iran borders. Six samples were collected from selected section of Ibrahim Formation, which consists of a succession of well-bedded white to gray limestone interbedded with gray marl and marly limestone. X-ray diffraction results show that calcite is the dominant mineral followed by quartz and traces of dolomite which appear in limited samples. X-ray fluorescence results revealed a noticeable increase of SiO2, which might be due to the effect of limestone by silicification process, so the rocks are considered to be a siliceous limestone. The other oxides (CaO, Al2O3, Fe2O3, MgO, Na2O, K2O, TiO2, SO3, and P2O5) are within the acceptable limits required for cement industry. Cement chemical parameters indicated that there is a decrease in the lime saturation factor (LSF) and an increase in silica ratio (SR) in comparison with the chemical parameters listed by standard specifications due to the increase of silica content. This increase can be adjusted by adding clays, or any other source of low silica content in addition to use iron and alumina as correcting additive materials for the cement mixture.

Geochemistry and Petrogenesis of Dioritic-Gabbroic Pegmatites in the Bulfat Complex, Qala Diza, Northeastern Iraq

Shareef Al-Hamed; Khalid Aswad; Nabaz Aziz

Iraqi National Journal of Earth Science, 2020, Volume 20, Issue 2, Pages 64-90
DOI: 10.33899/earth.2020.170371

The pegmatite dikes and associated plutonic rocks stand as a part of the igneous complexes associated with the Bulfat complex, located in the Zagros Suture Zone (ZSZ), NE Iraq. The Bulfat complex is a part of the ophiolite-bearing terranes that are allochthonous sheets. The complex represents the upper allochthon of the Albian-Cenomenian. The study area is located within Bulfat complex of ZSZ, specifically in the northwestern part of this zone and within the second unit of the Penjween-Walash Subzone. The rock samples were collected from pegmatite dike which is located to the northeast of the Darishmana village, the thickness of dike is about 5 m.
Electron microprobe analyses (EMPA) of plagioclase in 8 spots of dioritic pegmatites ranges between oligoclase (An18.00-An28.23) and andesine (An32.53-An33.62). Bulk whole-rock chemical analysis of fourteen samples using ICP-MS analysis reveals alkalinity Index (AI) of pegmatites to be metaluminous (A/NK > 2). Generally, the silica content in these pegmatites is from 46.70 wt. % to 52.67 wt. %.
The relatively flat pattern of REEs is characterized by the slight enrichment of LREEs compared to HREEs indicating the common ancestry of the studied pegmatites. Also, the enrichment of these pegmatites in LILEs (Sr, Pb, Rb) and depletion in HFSEs especially (Nb, Ta, Y) indicate the environment of the island arcs. Moreover, the low ratios of (Rb/Sr)N and (Ba/Sr)N refer to that these pegmatites are derived from a basic origin.
Tectonic discriminate diagrams show that the tectonic environment of studied pegmatites is I-type, which is the oceanic island arcs environment of sub alkaline rocks. The pegmatites of the present study have a genesis relationship with intrusions close to them in the study area; these intrusions are gabbros of Wadi Rashid that represent the environment of E-MORB. Moreover, the gabbros of Wadi Rashid and studied pegmatites are part of ophiolite-bearing terranes, they are found within upper allochthon thrust sheet. The current study of pegmatites reflects the oceanic island arcs environment, this indicates the existence of double island arcs, the first adjacent to the Arabian shelf, and the second close to the middle of paleo-ridge.
Numerous evidences support that the gabbros of Wadi Rashid being as the likely parent to the studied pegmatites such as geochemistry, tectonogenesis, and the close spatial distribution of the pegmatites to the gabbros of Wadi Rashid. Moreover, the studied pegmatites appear to entail further dissection mainly due to the fact that the occurrence of dioritic- and gabbroic-pegmatites with a small-scale in the single intrusion might have its explanation in the liquid associated immiscibility.

Sedimentological, Paleontological and Mineralogical Evidences for Oceanic Anoxic Event-2 (OAE-2) in the Gulneri Formation (Early Turonian), Northeastern Iraq

Safwan Al-Lhaebi; Ali Al-Jubory; Falah Al-Miamary

Iraqi National Journal of Earth Science, 2020, Volume 20, Issue 2, Pages 105-125
DOI: 10.33899/earth.2020.170373

In the current work, the Gulneri Formation (Early Turonian) is studied in three surface sections (Degala, Dokan and Azmir) from northeastern Iraq. The formation is characterized by grey to black color limestone and marly limestone in the Degala and Dokan sections, whereas in Azmir section, fissile marl and marly limestone with pale to reddish color are dominated in addition to few beds, which occasionally contain fish remains, with distinct gray color reflecting the very few amount of total organic carbon in these beds. Microfacies analysis revealed that the formation consists of three microfacies: mudstone, wackestone and packstone. The predominance of dwarfish planktonic foraminifera (Heterohilex) and thin shell filaments particularly in packstone microfacies represent Heterohelix shift event and filament event respectively. In addition to these events, fish remains, radiolarian pyritization, planktonic foraminiferal chambers elongation and glauconite are all refer to anoxic environmental conditions that may have been coincided with the Global Cenomanian-Turonian Oceanic Anoxic Event (OAE-2).

Ground Water Quality of Selected Areas in the Northeastern Mosul City and their Assessments for Domestic and Agricultural Usage

Kotayba . Al-Youzbakey; Ali Sulaiman

Iraqi National Journal of Earth Science, 2020, Volume 20, Issue 1, Pages 107-126
DOI: 10.33899/earth.2020.170350

The present study focuses on the assessment of groundwater for domestic and agricultural usages in two areas northeastern Mosul city: the first is located between Mosul city and Bashiqa Mountain, and the second is located between the road of Mosul-Alqosh and Shikhan – Dahqan – Alqosh Mountains which represents the Alqosh plain. These two locations were classified as agricultural areas. And their villagers use the groundwater for domestic and irrigation. The present study evaluates the groundwater for drinking using the water quality index (WQI). The assessment is achieved by calculating the (WQI) index from the physical and chemical parameters (pH, E.C., T.D.S., T.H., Ca2+, Mg2+, Na+, K+, HCO3-, SO42-, Cl- and NO3- ). The results confirm that the groundwater of the first area is classified as a poor class (WQI=56-73) for drinking due to its reservoir present within the sandstone layers of Injana Formation, which is affected by the infiltration of surface water through soil zone that contains the weathering fragments of carbonates and gypsum. The other wells of this area located along the road between Mosul city and Bashiqa Mountain are classified as very poor to unsuitable class for drinking (WQI=76-135) due to the presence of these wells within Fat'ha Formation rocks, except the Al-benit farm and Al-Fadelya1 groundwater that is classified as a good class for drinking (WQI<50). The Alqosh plain groundwater is classified as excellent to good class for drinking (WQI=15-36) because of their reservoir is present within sandstone layers of Injana Formation, except the wells of Kir-Ishaq, Batnaya, and Alqosh, and Alzayton village which is classified as poor (WQI=61) and unsuitable class (WQI=111-115) for drinking respectively because of their reservoirs are present within gypsum layers of Fat'ha Formation.

Determination of Geotechnical Properties of Local Claystones in Northeast Koya City, Iraqi Kurdistan Region

Nawzat Ismail; Hemn Omar

Iraqi National Journal of Earth Science, 2020, Volume 20, Issue 1, Pages 1-14
DOI: 10.33899/earth.2020.170286

The aim of the current study is to determine the geotechnical properties of the investigated claystones /clayey soils in Koya area, Iraqi Kurdistan Region. This paper deals with the evaluating of the physical, mechanical and index properties of claystones. The study based on the field reconnaissance for twenty-five claystones samples were collected from five outcrops location within Fat'ha Formation. The results obtained from the laboratory tests revealed that the averages of specific gravity, porosity, void ratio, water absorption, natural water content and uniaxial compressive strength values of claystones are (1.5, 4.45%,4.5, 0.3, 3%, 65 MPa) respectively. Whereas the results of the index geotechnical characterization of clayey soils revealed that the averages values of liquid limit, plastic limit, plastic index, flow index, toughness index, liquidity index, consistency index, swelling potential, activity index, and expansive potential are (25.2, 15.0, 10.2, 0.2, 0.5, -1.2, 2.2, 0.62, 0.31, low or non-expansive) respectively. Among the index properties, the clayey soils are suitable for foundation and building materials industry. Furthermore, the regression coefficients of their correlation (R²) obtained from the analysis show that there are strong relationships between the physical and mechanical properties of claystones. Concluding remark is that geotechnical properties of examined natural claystones satisfy the relevant regulation to be used for construction purposes.

Geochemistry of Phosphorite and Associated Rocks of Akashat Formation (Middle Paleocene) in Akashat Mine, Iraqi Western Desert. Part II: Trace Elements

Kotayba Al-Youzbakey; Salim Al-Dabbagh

Iraqi National Journal of Earth Science, 2019, Volume 19, Issue 2, Pages 100-118
DOI: 10.33899/earth.2019.170282

Akashat Formation is an important formation due to its content of the Hirri member, which includes phosphorites and phosphatic limestones, that are rich in P2O5. These rocks are mainly composed of apatite and calcite. In addition to other minor and trace minerals like palygorskite, quartz, dolomite and secondary gypsum. All these minerals are hosted the most trace elements in the Akashat rocks. U, Sr, Y and Zr are related to apatite more than other minerals. While Ga, Rb and Ti are almost correlated with the clay minerals. The rest trace elements are distributed among other minerals and organic matter. The hosting of trace elements by a mineral takes place in many cases as substituted in Ca(I), Ca(II) and phosphate tetrahedron in Francolite, Ca site in calcite, in clay mineral phases, or adsorbed on clay mineral faces, organic matters and in the crystal channel of francolite.

The Geochemistry of Phosphorite and Associated Rocks of Akashat Formation (Middle Paleocene) in Akashat Mine, Iraqi Western Desert. Part I: Major Oxides

Kotayba Al-Youzbakey; Salim Al-Dabbagh

Iraqi National Journal of Earth Science, 2019, Volume 19, Issue 1, Pages 80-97
DOI: 10.33899/earth.2019.170272

The phosphatic compounds in the phosphorites of Akashat Formation (Middle Paleocene) are mainly composed of francolite. The associated rocks (phosphatic limestone) consist of calcite and francolite. As well as, there are little amounts of dolomite, palygorskite, quartz and iron oxides. Francolite is composed of Ca, P, F and O, the tetrahedron SO4 and planar CO3 as CO3+F substitute PO4. Some of Na and Mg are substituted in both sites Ca(I) and Ca(II). F occupied its sites in the channel. Some F subsititute O in CO3 to form the pseudo-tetrahedron of CO3+F. The elements Si, Al, Mg, Fe and K represent the clay minerals; montmorillonite, palygorskite and sepiolite, as well as, quartz and iron oxides.
The geochemistry of phosphorite reflects the primary neoformation conditions of marine apatite (francolite) from calcium, phosphate and fluorine, in addition to the substitution of positive mono- and di- valance cations for calcium in Ca(I) in submarine mud of the oceanic floor. The phosphate deposits were exposed to winnowing and transporting by upwelling currents to the continental shelf area. This led the phosphatic deposits to be affected by early and late chemical and biochemical diagenetic processes, causing activities in substitution of cations for calcium in Ca(II) and carbonate, also, additional fluorine and sulfates for phosphate. The flow of continental water to near-shore area, whose content is magnesium leading to remineralization of clay minerals, (e.g. palygorskite and sepiolite from montmorillonite) by depleting magnesium from sea water, as well as the activity of microorganism, all that is provided by suitable growth conditions for phosphatic compounds in continental shelf area.