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There are fragments of xenoliths in basaltic rocks of young volcanoes
from Stromboli (Italy). They are oordierite bearing bUChite, having white
colours and are in various sizes. The biggest fragment is around 20 '-"In long.
The main minerals are cordierite. Around eithy percent of rocks composed of
cordieritc and 20% consist of tridymite, hypersthene, sanidine and glass.
Microscopic studies shows that the texture is granoblastic and mosaic. The
mineral paragenesis and chemical composition indicated that the original rock
were aluminum - rich and bauKitc - rich shales. The cordierite are the Mgrich
cordierite. Xenoliths mctamophosed by sanidinitefacies.

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Boboluyieh bauxi te-laterite deposit of south-cast
Kemlan is presented at the base of the Naiband Formation
(upper Triassic) and was directly formed on a Karstic surface
of dolomitic parts of the Shotori Formation. This dcposit has
a reserve of 15 mill ion lonnes. Diaspore, boehmite, chlorite,
hematite, goethite, kaolinite, anatase and rutile arc the major
minerals in this deposit. The common texture of tbis unit is
oolitic to pisolitic. The presence of some volcanic rock
fragments with pi lotaxitic texture as well as bipyramid
pseudol11orphic shape of olivine and clinopy roxene gra ins
reveal thai the protolith of bauxites was probably a volvan;c
rock of basaltic type.
Geochemical studies indicate that Bolboluy ieh bauxite is
composed of40.37% AI20 3, 24.64% Fe20) and 13.92% Si02•
Based on the geochemical characteristics, Bolboluyieh
bauxi te is formed under condition of high silica leaching and
concomitant enrichment of aluminium and iron which
corrcsponds with pH between 4 to 8.5 and Eh of +0.4 to + I.

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The Qopi bauxitic horizon is located west of Miandoab, in West-Azarbaidjan province, NW of Iran. It lies along the boundary of Ruteh (middle-upper Permian) and Elika (lower Triassic) Formations. This horizon includes four distinct lithologic facies such as (1) bauxitic iron ore, (2) ferruginous bauxite, (3) Fe-rich bauxite, and (4) Fe-rich clayey bauxite. Microscopic  examinations showed various textures including pelitomorphic, fluidal, colloform, pseudo-breccia, and pseudo-porphyry within the horizon, suggesting an authigenic origin. Based upon field evidence and geochemical data, the fine-grained diabase in the area may be the probable parent rock from which the bauxite layers developed. The results of calculations of mass changes showed that elements such as Na, K, Mg, P, Si, and Ca were depleted, and Fe, Al, and Ti were enriched during bauxitization processes. According to field observations, microscopic examinations, and geochemical investigations, Eh variations (from reducing to oxidizing) and suitable pH (6-8) of descending meteoric waters were the prime factors controlling the formation of Qopi bauxite layers. In addition, the enrichment pattern of immobile elements and field evidence indicate that the Qopi bauxitic horizon may be classified as Mediterranean karst bauxite

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The Jajarm Bauxite deposit 16 kilometers E-W trending and
overlis, the Karstic dolomite rocks of the Elika Formation. The study of
texture and different phases has been carry out in order to understand the
degree of crashing, particles size, condition of formation, degree of
crystallization, porosity, distribution of constituent elements and
beneficiation for the propose of digestion and potential of physical
beneficiation. The phase analysis indicates that the Jajarm Bauxite is typical
diasporic bauxite accompanied with Kaolinite, hematite and anatase. Hard
bauxite is the high quality bauxite with Al2O3>50% and SiO2 < 9%. Mineral
chemistry shows that out of 58% of Al2O3, 54.39% constituting diaspore
structure, 1.6% is in kaolinite and 0.94% in topaz. where as out of 5.78%
SiO2, 3.72% occurring in kaolinite structure, 1.5% as free and inactive quartz
and the rest of it is located in topaz structure. The Jajarm bauxite shows a
politomorphic, micro granular texture with several secondary textural
elements. The size of main minerals component are generally below 10
micron, with homogeneous matrix. Kaolinite minerals forms stacks of very
thin (<0.1 micron) crystal platelets. In addition, in a very hard bauxite,
separation between the crystal grains and the matrix can not be done because
of similar hardness for both with closely packed space filling and in
consequence of the missing defined borderlines of the grains. Based on the
above studies, the Jajarm bauxite can be enriched neither by grain analysis
nor by the magnetic separation. Laboratory study shows, only it can be
improve by water treatment.

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Shahid Nilchian (Dopelan) deposit, located in high mountains of Chahar-Mahal Bakhtiari Province within the Zagros Thrust structural unit, is one of the main bauxite and argillite deposits of Iran. Many highly folded and faulted sedimentary successions are cropped in the area. The bauxite of Shahid Nilchian deposit is of lateritic type and belongs to Permo-Triassic in age. Five bauxite types with different quality have been recognized in the area. Mineralogical investigations have carried out using thin and polished sections, XRD and XRF analysis. According to these studies, it is verified that the major minerals are diaspore and kaolinite. Anatase and boehmite has identified as minor minerals. Some other elements such as iron, zirconium and vanadium are also presented in different minerals. The main identified textures are brecciated and pisolitic. In its application as refractory material, minerals containing iron, silica and titanium are the important gangues of bauxite. The main objective of this mineralogical study is to identify the minerals of the above mentioned elements. It is concluded that kaolinite, anatase and different iron oxides are the main sources of these elements.

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In this research, the properties and characteristics of Biglar refractories bauxite mines have compared with two types of industrial China's and Iranian (Doplan super) refractory grade bauxite in order to use in refractory industries. At first, physical, chemical and thermal properties, phase and microstructural characteristics have been measured and sintered samples of Biglar Bauxite at different temperatures were analyzed and then were compared with China's and Doplan calcined bauxite properties. The results showed that the refractory bauxite minerals obtained from Iranian Biglar mines contains the proper amounts of alumina and other oxides. So it could be concluded that these properties are comparable to the China's and Doplan bauxite and this refractory grade bauxite is suitable for refractory industries for using in the production of many kinds of shaped and monolithic refractory product.

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Bauxite deposit of Permo-Triassic age in northeast of Bukan was developed stratiformly along the boundary between Ruteh and Elika formations, and includes four distinct rock units. This deposit was affected by tectonic and morphological processes. Mineralogical and geochemical investigations showed that during weathering processes, two mechanisms of ferrugenization and deferrugenization played crucial role in formation of minerals such as diaspore, boehmite, hematite, goethite, kaolinite, pyrophyllite, clinochlore, illite, montmorillonite, anatase, rutile, albite, sanidine, quartz, and calcite in this deposit. By taking notice of field evidence and of mineralogical and geochemical data, the basalts (whose remnants are still present along the contact of this deposit with carbonate bedrock) are the potential parent rock of this deposit. The distribution pattern of REEs (normalized to chondrite and basaltic parent rock) along with anomaly variations of Eu, Ce, and (La/Yb)_N indicates differentiation of LREEs from HREEs during bauxitization processes. Further geochemical considerations indicate that the concentrations of LREEs were occurred by hematite, goethite, manganese oxides, cerianite, and secondary phosphates (rhabdophane, vitusite, gorceixite, monazite) and of HREEs by clay minerals, rutile, anatase, zircon, euxenite, and fergusonite. Incorporation of the results obtained from mineralogical and geochemical investigations suggests that in addition to factors such as pH of weathering solutions, ionic potential, composition of the parent rock, and fixation by residual minerals, adsorption processes also played crucial role in enrichment of REEs during moderate to intense lateritization in the study area.

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Permian bauxite deposits in north of Saqqez occurred as stratiform lenses of carbonate within Ruteh Formation. Field evidence show that these deposits formed in swampy environment in which the water table was relatively high during their evolution. According to petrographic considerations, these deposits contain ooidic, pisoidic, spastoidic, nodular, skeletal, and spongy textures and have an authigenic origin. Based on mineralogical studies, these deposits are composed of minerals of diaspore, boehmite, corundum, hematite, goethite, magnetite, rutile, anatase, montmorillonite, quartz, illite, pyrophyllite, talc, nacrite, dickite, k-feldspar, muscovite, chlorite, chloritoid, plagioclase, pyroxene, amphibole, chamosite, gypsum, calcite, and fluorite. The presence of high quantities of silicate minerals indicates immaturity and poor draining system of these deposits. Comparison of the range of stability fields of major constituent minerals of the bauxite ores with the pH and Eh variations of natural environments show that  the surface waters with oxidizing-acidic nature and underground waters with reducing-basic nature played crucial roles in developing of these deposits. Combination of mineralogical and geochemical data of immobile elements indicate that Saqqez bauxite deposits were developed from alteration and weathering of basaltic-andesitic rocks.

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The Heydarabad bauxite-laterite deposit is located in 63 km southeast of Urmia city. This ore deposit occurs as a concordant layer within the boundaries of Upper Permian and Lower Triassic carbonate units (limestone and dolomite), although it has been suffered some tectonic displacements along its direction. The studied horizon varies from 15-20 m in thickness and has an east-west trend with a length of 3.5 km. This deposit consists primarily of two parts of dark and light in color. The former is rich in hematite and corundum, (upper horizon) and the latter in phyllo-aluminosilicates (lower horizon) with an gradual boundary, respectively. Common textures are mostly pisolitic, nodular, oolitic and massive. Based on the microscopic studies and XRD analysis, the main mineral components are hematite, diaspore, chloritoid, and corundum. On the other hand, chlorite, rutile, magnetite and pyrite are found as accessory phases. The Heydarabad bauxite-laterite horizon is different from those occurred into the Iran-Himalayan belt based on the absence of boehmite, kaolinite and other clay minerals, and the abundance of corundum, chloritoid and chlorite. The geological and mineralogical evidences indicated that a thermal metamorphic event was responsible for the formation of this special mineralogical composition after bauxitization processes. Based on geological, mineralogical, and chemical characteristics, it can be proposed that the probable parent rocks for the Heydarabad bauxite are mafic sills and diabasic dykes. Due to considerable accumulation of minerals which their hardness is greater than 6, this ore deposit can be presented as a potential for abrasive applications.

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The Jajarm bauxite deposit is a part of the Irano-Hymalayan karst bauxite belt which is located about 175 km southwest of Bojnourd. This deposit has been developed as a stratiform horizon along the contact of Triassic dolomites and the Jurassic shales and sandstones. The basal contact zone of the bauxite horizon is mainly undulatory, and bauxite fills cavities in the footwall dolomite, whereas the upper contact zone is concordant with the hanging-wall shales and sandstones. Textural analysis indicates both allochthonous and autochtonous origins for the bauxites. Diaspore, bohemite, gibbsite, chamosite, hematite, goethite, clay minerals, anatase, cancrinite, crandallite, pyrite, and quartz were identified in the ore paragenesis. These minerals are developed during three stages of weathering, diagenetic and epigenetic processes. Combination of mineralogical and geochemical data show that this deposit formed during two main stages. First, bauxite materials, Fe and Ti oxides and clay minerals were developed as authigenic bauxitization processes of alkaline basaltic parent rock. During the second stage, these materials were transported to karst depressions, where they accumulated as a relatively thick bauxite horizon.

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The Alborz structural zone in northern Iran is the host of a number of bauxite deposits. The Gheshlagh bauxite deposit is one of them with more than 2 km long and a thickness of about 20 m in the eastern part of the Alborz structural zone. This deposit has been developed as a stratiform horizon along the contact zone of Permian limestones and Triassic dolomitic limestones. The basal contact zone of the bauxite horizon is mainly undulatory, whereas the upper contact zone is concordant with the hanging-wall dolomitic limestones. Based on mineralogical and textural evidences, the horizon can be divided from top to bottom into five distinct units: (1) upper bauxite unit with a thickness of about 5 m, is composed of boehmite, hematite, kaolinite, rutile and svanbergite, 2) upper kaolinite unit approximately 2-3 m thick and is composed mainly of clay minerals, 3) hard bauxite unit with a thickness of approximately 1.5 m, mainly consists of hematite, kaolinite, boehmite and diaspore, 4) lower kaolinite unit approximately 1-4 m thick and is composed of kaolinite, boehmite and diaspore, and 5) lower bauxite unit about 4-6 m thick. Textural analyses indicate both allochthonous and autochtonous origins for these deposits. Combination of geological, textural and mineralogical data of the Gheshlagh bauxite deposit correspond to a boehmitic-diasporic karst bauxite deposit type.     

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Minerals, depending on their composition and origin, contain some radioactive nuclides. Presence of such radionuclides such as ²³⁸U, ²³²Th and ⁴⁰K in materials are dangerous when they are highly concentrated and influence on human exposure. Bauxites as a raw material for aluminum may contain relatively high amount of those radionuclides, which are more concentrated in remained red-mud after Al production process.  Due to high existing of iron oxides in the red-mud, it is preferred to be used in recycled products such as cement and brick. Because of high amount of radionuclides in red-mud, its radioactivity should be determined and decrease their environmental impact before using in industry. Therefore, radiation of red muds from Jajarm bauxite mine, which is the biggest bauxite deposit in Iran (with 1000000 tones red-mud annual production), have been determined in this study. Finally, after determination of average radiation of Jajarm red-mud, the mixing ratio of red-mud to low-radiation materials (such as clay minerals) was calculated for using in construction materials, under standard level of radiation.

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The Mombi bauxite deposit is located about 160Km northwest of Dehdasht in the Zagros Simply Folded Belt. The bauxite deposit exhibits an ooilitic and pisolitic texture. It contains higher amount of boehmite than those of diaspore, hematite, kaolinite, and anatase. This study uses the geochemistry of immobile elements in order to calculate the mass changes that took placed during weathering and bauxitization. The results reveal that elements such as Si, Fe, Mg, P, K, Ba, Sr and Zn are depleted, while Al, Zr, V, Cr, Ni, Ga, Y and LREEs indicate positive mass changes during the weathering and bauxitization processes. In addition, Nb, Hf, Ta, Rb, Cs, U and HRRE exhibit little changes, suggesting relatively immobile features. Interelemental relationship analyses of the ores, by using R-mode factor analysis, revealed a number of key findings: (i) some low solubility elements were concentrated in detrital zircon (Zr), in anatase (Ti), and possibly in boehmite, hematite and detrital minerals (Ga) during the later stages of bauxitisation; (ii) Fe was concentrated during humid climatic conditions, whereas Al accumulated during dry conditions; (iii) similar and meaningful weightings for U and Th suggest that heavy minerals frequency would be locally important in controling the uranium behavior; (iv) distributions of LREEs and HREEs are controlled by the stability of the carrier complexes of REEs and the existence of REE-bearing mineral phases; and (v) (La/Yb)_n ratio values suggest that little LREE/HREE fractionation occurred during bauxite formation and (La/Yb)_n ratio fluctuations may also be indicative of fluctuations of pH in soil solution.

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The Gazanjeh bauxite deposit (SE Mahabad, West-Azarbaidjan province) is a typical residual sedimentary deposit with dolomitic limestone host rock of Permian age in northwestern Iran. Calculations of normative values of minerals using obtained results from XRD and XRF analyses in a selected profile indicate that diaspore, hematite, and pyrophyllite were major mineralogical phases of this deposit and include 71.73 to 94.66 % of mineralogical composition of ores, approximately. Based on normative values of minerals, this deposit was formed from two-type ores, (1) clayey bauxite and (2) iron-rich bauxite. Based upon chemical analyses, REE values vary in the ores from 30.14 to 379.55 ppm. Values of La/Y, Eu/Eu*, and Ce/Ce* in the ores are within the ranges of 0.33-3.16, 0.57-1.36, and 0.87-7.05, respectively.  Combination of the obtained results from investigation of trend of lanthanides changes and elemental ratios in the selected profile suggest that factors such as change in physico-chemical conditions of depositional environment (pH and Eh), fluctuations in level of groundwaters table, degree of complexation with carbonatic lighands, difference in the stability of lanthanides-bearing minerals, and mineral control have played the important role in distribution and mobilization of REEs during formation and development of the studied bauxitic ores.   

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The Zaraj-Sou bauxite deposit (southwest of Ramsar, Mazandaran Province, northern Iran) was developed as discontinuous stratified layers and/or lenses along the boundary between carbonate rocks of the Elika (Triassic) and shales and sandstones of the Shemshak (Lower Jurassic) formations. Diaspore, kaolinite, hematite, and anatase are the major mineral phases of the ores. Texturally, the bauxite ores have typical textures of clastic, rounded-grain, and nodular which are often accompanied by certain forms of concretions, ooids, and pisoids in restricted quantities. Concentration values of REEs within the ores in the selected profile vary from 149.97-348.10 ppm and the ratios of Eu/Eu* and Ce/Ce* are within the range of 0.75-1.04 and 0.64-1.28, respectively.  Investigations showed that changes in the values ​​of these parameters are controlled by degree of scavenging hematite. The calculation of mass changes of elements and the study of the trend of variation of elemental ratios in a selected profile across this deposit revealed that the distribution of REE in ores is a function of factors such as changes in pH of ore-making solutions, presence of carbonate bed rock as an active buffer, co-precipitation with metallic oxides, and fixation in neomorph mineral phases. Correlation coefficients among elements suggest that minerals such as hematite and secondary phosphates are the potential hosts for lanthanides in the studied ores.

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The Siahrudbar deposit is located about 25 km southwest of Aliabad-Katool city in the Golestan Province, north of Iran. This deposit lies between the Triassic limestone (Elika Formation) and Jurassic sandstone (Shemshak Formation). Mineralogical studies indicate the presence of major minerals such as diaspore, hematite, anatase, kaolinite, and chamosite accompanied by minor minerals such as boehmite, goethite, rutile, calcite, moscovite, clinoclar, quartz, and tridymite. Calculation of enrichment factor showed that the bauxitization processes at Siahrudbar were accompanied by enrichment of elements such as Al, Fe, Ti, V, Cr, Co, Ni, Ga, Th, U, Y, Zr, Ta, Nb, Hf, and REEs. While elements such as Si, Mg, Na, K, P, Ba and Rb were leached out of the profile and suffered depletion. Futhermore, elements like Ca, Mn, Sr and Cs experienced both partial leaching and fixation. Based on the results of geochemical studies, changes in pH and Eh of the weathering solutions, adsorption, presence of organic matter, function of carbonate bed rock as a geochemical barrier, existence in resistant minerals, and fixation in neomorph mineral phases played crucial role in distribution of the trace and rare earth elements in the studied ores. Consideration of the correlation coefficients among elements demonstrated that the neomorph phosphate minerals can be conceived as the potential host of rare earth elements.

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The Pirashkaft bauxite deposit is located in north of the Paskuhak anticline in the Fars Province. The bauxite deposit present between Sarvak and Gurpy Formations, and formed during the Late Turonian time as a consequent of the Laramid orogeny phase. According to the geological investigations, the Pirashkaft bauxite is  Karstic type. The residual ore studied in the Pirashkaft can be classified into three groups: 1) kaolinite bauxite, 2) bauxite and 3) ferrite bauxite. Petrographically, pisolithic–oolithic is the most important texture. Mineralogically, the main minerals include boehmite, hematite, diaspore and kaolinite and minor minerals comprised of: gibbsite and rutile. The major oxides in the bauxite horizons mainly included: Al₂O₃ (37.88- 55.45wt%), SiO₂ (2.01- 30.49wt%), Fe₂O₃(10.14- 36.71wt%) and LOI ( 9.72- 15.32wt%). There is a strong positive correlation between Al₂O₃ and TiO2, and also an enrichment of LREE (136.49- 928.56 ppm) relative to HREE (16.48-59.5 ppm) is observed in the bauxitic horizons.  The Eu / Eu^* anomaly of the bauxite samples ranges between 0.26 and 0.99. Positive anomaly of Ce / Ce^* between 1.2 and 2.33, indicates the dominant oxidation during bauxitization.

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The present study focuses on the geochemistry and genesis of REE minerals in the Tang-e Pirzal karst bauxite deposit. The deposit is located about 45 km east of Dehdasht city in the central part of the Zagros Fold Belt. The ore bodies comprise a series of contiguous lenses that occur as infills of deep karst cavities, depressions, and fractures within the upper neritic carbonates of the Cenomanian–Turonian Sarvak Formation and are structurally controlled by strike-slip fault systems. The most frequent authigenic REE minerals are fluorocarbonates of bastnäsite group that form a solid solution series between end members parisite (CaCe₂(CO₃)₃F₂) and bastnasite (CeCO₃F). The formation of bastnasite-Ce and parisite-Ce suggests that cerium as fluoride and/or carbonate–fluoride complexes were simply leached by acidic downward solutions and finally precipitated on the geochemical barrier of the carbonate bedrock under alkaline and reducing conditions. Cerianite (CeO₂) occurs mainly as fine grains in the porous aggregates of the cryptocrystalline matrix. Cerianite precipitation may occur due to the predominance of acidic/oxide conditions in the upper parts of the bauxite profile. Examination of the vertical distribution of the ∑REE, (La/Yb)_N, Ce/Ce*, and Eu/Eu* indexes indicates progressive enrichment of the REE and slight LREE/HREE fractionation toward the lower parts of the bauxite profile. Cerium behaves differently from the other REEs and shows fluctuating behavior throughout the Tang-e Pirzal profile, which can be related to periodical fluctuations of the groundwater table in response to environmental changes.