Mining Mineral Geochemical characterization of the Sutlegen bauxite deposit, SW Antalya

Purpose. The purpose is to determine geological and geochemical characteristics of the Sutlegen (Antalya, Turkey) bauxites, to identify the elements that played a major role in their formation. Methods. X-ray diffraction (XRD) mineral phase analysis, X-ray fluorescence (XRF) elemental analysis, plasma-mass spectrometry (ICP-MS), the petrographic and mineralogical analyses, and multivariate statistical methods were used. Findings. The major element content of the ore was determined as Al 2 O 3 (60-35.2 wt%), SiO 2 (39.5-0.2 wt%), Fe 2 O 3 (48.4-19.5 wt%), TiO 2 (36.9-16 wt%), and P 2 O 5 (0.5-0.1 wt%). The Sutlegen region, which shows epirogenetic action with the uplift of the earth's crust, is generally rich in neritic carbonates. It was revealed that the bauxite ores have undergone moderate and strong laterization as a result of the deferruginization in the environment, and they were classified into four groups as lateritic, ferritic, kaolinitic, and bauxite. The increase in the aluminosilicate minerals, which were formed during the formation of bauxite in the environment was found to be directly proportional to the laterization processes. In this con-text, it was considered that the lateritic material that was firstly formed in the environment filled the cavities and pores of the karst-type limestones and sedimentary units in the region by superficial transfer phenomena. The bivariate diagrams of Log Cr vs. Log Ni revealed that the bauxite that formed in the region had an ultrabasic source. In on mineralization in the Sutlegen deposits that have been for a long Practical implications. the of revealed that the source of the laterization process in the region was the ultrabasic igneous rocks. The lateritic material moved by superficial transfer was accumu-lated on sandstone, claystone, siltstone, and limestone and in karstic cavities; then, it formed karstic bauxite (kaolinitic and bauxite) of different classifications due to the effect of metamorphism.


Introduction
The study area, the Sutlegen region, is located within the Western Taurus belt (Fig. 1). The geochemical explanation of the elemental relationships that play a role in the formation of bauxites in the region can be given as a problem formulation within the scope of the study. The trace and rare earth elements' relationships were examined using multivariate statistical methods to determine the mineralogical and petrographic properties of bauxite samples and paleo-climatic conditions. When the metamorphism conditions are met, the clay layers get enriched in metallic formations such as alumina and get depleted in silica. In the next stage after this formation, bauxite minerals such as gibbsite, boehmite, or diaspore are enriched. Thus, the concentrations of precious metals such as Al, Fe, and Ti increase [1]- [7]. The chemical content of bauxite is composed of high levels of major, trace, and REE elements (Ti, P, Zr, Nb, Ni, Cr, Co, V, Ga, U, Sc), and particularly Al metal [1], [4], [5], [7]- [16].

Figure 1. Site location map of the study area, sample numbers, and aluminum anomaly
The behavior of mobile elements during the formation of bauxite indicates the intensity of chemical weathering. The physicochemical conditions (Eh-pH, paleoclimatic properties, etc.) during the formation of the ore are determined using these mobile elements [17]- [21].
Three types of bauxite classifications have been adopted in the international literature: lateritic bauxite, karstic bauxite, and Tikhvin-type (sedimentary) bauxite [22]- [24]. Although lateritic type bauxites are rich in gibbsite minerals, aluminosilicate rocks are the source rock in their formation [3], [25]. The relationship between the karstic bauxites and the parent rock can be either allochthonous or autochthonous [7]. Therefore, the discussions on the determination of the geological genesis of the karstic bauxite deposits have still been going on. There are several studies on karsttype bauxite deposits in the literature. In a study on karsttype bauxite deposits in north-western Iran, the bauxite ore, which was formed within the dolomitic limestones in lens form, was investigated in terms of its mineralogical and petrographic characteristics. The XRD and SEM-EDS analyses revealed that the major minerals of bauxite were diaspore and hematite, while the mineralogical components of clay lenses were kaolinite and montmorillonite. Also, the analyses revealed that the metal content consisted of Ni, Cr, Co, V, Fe, Nb, Ga, Ta, Th, Hf, and Zr besides Al. In the model proposed for bauxite formation in Iran, it was considered that alkali and alkaline earth metals were depleted at the top of the profile under acidic environment conditions; also, with the deepening of the profile, the acidic character of the environment changed, thus, the environment was enriched in metallic bauxitic minerals and elements [7]. The major mineral composition of the karst-type clay bauxite deposit in Semirom in the Himalaya region was found to be diaspore, boehmite, kaolinite, and hematite [4]. The elements of Cr, Co, Ni, Ga, and Th were found to have an increasing concentration in the bauxitic material [4]. In the geochemical genesis study on the bauxite deposit in the Henan region in China, the ore formed on the karstified carbonate series was found to be rich in Li, B, Sc, V, Ga, Zr, Nb, W, and total REE. In the research, it was observed that the behavior of the Li, B, V, Cr, and Ga elements increased directly proportional to K2O and SiO2; as a result, the increase in the clay minerals in the environment was associated with bauxite formations [6].
The objectives of the study are listed as follows; to learn the major, trace and rare earth elemental concentrations of bauxite in the region, to determine the connection between regional geology and bauxite formations, to understand the bauxite formation environment conditions, to determine the types and geological genesis of bauxite occurrences in the region.

Methods
The Sutlegen region, the study area, is located 37 km north of the Mediterranean coastline and 168 km from Antalya between Kalkan (Kas) and Elmali districts. Sixty-eight surface samples were taken from the Sutlegen region. The samples were brought to Akdeniz University's "Ore Deposits Laboratory" and prepared for analysis.
Five samples were analyzed by optical microscopy imaging methods, four samples were analyzed by X-ray diffraction (XRD), sixty-eight surface samples were analyzed by Xray fluorescence (XRF), and seventeen samples were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS). The petrographic analyses were carried out in accordance with the procedures detailed in the studies [26]. ICP-MS analysis was carried out at the Mineralogy-Petrography Research Laboratory of the General Directorate of Mineral Research and Exploration, XRD (BRUKER, D8 ADVANCE) and optical microscope imaging were carried out at the Mineral Deposits Laboratory of Istanbul Technical University, and XRF (Rigaku, NEX-CG) analyses were performed at the XRF Laboratory of Akdeniz University. In the XRF spectroscopy method, geological materials are exposed to high-energy radiation, thus, the electrons in their internal orbits are removed. At this stage, fluorescence radiation occurs during electron detachment, and it reflects the characteristics of each different element. The device distinguishes the fluorescence of the elements known in the literature and performs both qualitative and quantitative analyses according to their intensity [27]. The REE and trace elements in rock samples are analyzed using the ICP-MS device after a difficult sample preparation process. Hydrofluoric acid (HF) and similar strong acids are used to dissolve geological samples [28]. The acid better penetrates the sample by heating, and the rock is expected to show complete dissolution. The prepared sample solution is atomized using high flame technology [28].

Regional geology of the study area and geology of the Sutlegen bauxite deposits
In the study area, there are allochthonous (Yesilbarak nappe) and autochthonous (Elmali Formation, Quaternary alluvium, and hillside rubble) rock units showing various stratigraphic and structural characteristics. The Katran Mountain region, where the bauxites of the study area are observed, is represented by the Beydagları autochthonous (Fig. 2a, b).

Figure 2. Geological map: (a) structural units map of the study area; (b) 1/250.000-scale geologic map, P23 sheet (edited version of the raster map of MTA 1:250000 Fethiye P23 sheet) [29]
In the study area, the formations can be ordered from the oldest to the youngest as the Beydaglari formation belonging to the Upper Cretaceous period in the Mesozoic era, the Susuzdag formation belonging to the Eocene period in the Cenozoic era, and the Sinekci formation (Gumuce member at the bottom and Caybogazi member at the top) belonging to the Burdigalian period in the Miocene era. The Beydaglari autochthonous is overlain by the Kasaba Formation belonging to the Upper Burdigalian-Lower Langhian period in the Miocene era. The Elmali formation, which was formed in the Eocene-Miocene era, is tectonically associated with the Yesilbarak nappe, which also includes the Upper Lutetian-Lower Burdigalian rocks. (Fig. 3) [30]- [34].

Figure 3. Geologic map of the study area and bauxite area [35]-[37] (edited version of the raster map of MTA 1:100000 Fethiye M9 sheet)
Due to the transgression as a result of the epeirogenic movement, members of the Sinekci formation (Gomuce member, Caybogazi member) and Kasaba formation rocks were deposited on the Beydaglari autochthonous. Mandirkaya formation, as a geological unit observed in the Sutlegen region, is seen in the vicinity of Yaylacik Hill, and it seems like a massive rich in neritic carbonates [30]- [39].
The Beydaglari formation consists of neritic limestone, dolomite, dolomitic limestone units and forms the upper boundary of bauxite ore. Susuzdag formation consists of neritic limestones. The Gomuce member of the Sinekci formation consists of algal limestones and the Caybogazi member of the Sinekci formation consists of clays on the top. Kasaba formation consists of coarse-grained clastic conglomerate, sandstone, claystone, and siltstones.
In the intermediate zone (Yesilbarak Nappe), Elmali formation consists of limestone, intermediate-level sandstone, mudstone, and shales. As one of the cover units, alluvium generally consists of yellowish, poorly sorted, poorly consolidated conglomerates, sand, and mudstone levels. Considering the suitable paleokarstic topography of the area, which is bounded by limestones at the top and bottom, the limestones were formed in a discordant structure. The Elmali formation, which is the exposure surface of the region, forms the lower boundary of bauxite formations that occurred in the depths of the formation in later periods (Fig. 4).
The color scale of the bauxitic profile from the bottom to the top was observed to range from light brown to dark brown and dark smoked. It was also observed that they showed oolitic and pisolitic characteristics in round grained structure as a textural feature.

Mineralogy
The spectra of the semi-quantitatively measured XRD analysis revealed the mineralogical composition of bauxite. The Sutlegen bauxite was found to constitute the dominant mineral phases of boehmite (56.34-49.04 wt%), kaolinite (12.20-9.89 wt%), hematite (15.17-7.72 wt%), gibbsite (12.18-7.17 wt%), goethite (4.07-1.56 wt%), and anatase (13.11-6.21 wt%). On the other hand, anorthite, quartz, and chamosite are the minor mineral phases in the content (Table 1 and Fig. 5). According to the proportions of mineral content, ore paragenesis can be listed as follows: boehmite > kaolinite > hematite > gibbsite > goethite > anatase > anorthite > quartz > chamosite. Bauxite samples have high boehmite and kaolinite content. Considering the tropical climate conditions in the formation environment of bauxite, the boehmite mineral was formed as a result of the destruction of kaolinite/dehydration reactions [4], [18], [40].  The bauxite matrix is composed of clay and Fe-oxide/hydroxide minerals. While the brightest mineral observed in the cross-sections ( Fig. 6a-f) is hematite, goethite is the second brightest mineral. Goethite mineral has iron content. In the cross-sections, hematite mineral is observed to be disseminated. The minerals providing cloudy internal reflections in the cross-sections are boehmite (Fig. 6b, c, d, f). The order of the minerals formed when bauxites undergo metamorphism is as follows: gibbsite, boehmite, and diaspore. The mineral dehydrates as it goes from gibbsite to diaspore.

Major elements geochemistry
Ore content was found to be Al2O3 (60-35.2 wt%), SiO2 (39.5-0.2 wt%), Fe2O3 (48.4-19.5 wt%), TiO2 (36.9-16 wt%), P2O5 (0.5-0.1 wt%) ( Table 2). The fact that SiO2 and Fe2O3 compounds have the highest concentrations following Al2O3 in the Sutlegen bauxite is associated with the mineralogical change. Changes in the chemical composition are under the control of the mineralogy [4], [7], [41], [42]. While the SiO2 value increases depending on the kaolinite and anorthite minerals, the Fe2O3 value changes by the increase in the hematite and goethite minerals. The differences in SiO2 and Al2O3 values in ore samples are associated with laterization reactions during bauxite formation [7]. According to the Al2O3-SiO2-Fe2O3 triangular diagram (after [43]) which shows the degree of lateritization, the ferritic bauxite sample B55 (B55SiO2: 23000 ppm) has the lowest SiO2 content and shows the strongest laterization among the Sutlegen samples. The K2O, MgO, and CaO, which are classified as alkaline and alkaline earth elements, have low concentrations. They show mobile element behavior during the formation of bauxite and deplete easily in the environment [44], [45].

Trace elements
The  Table 3). It is known that karst-type bauxite formations around the world have a Ga element content of about 58 ppm [6], [46]. The distribution of the Sutlegen bauxites is similar to the Ga element behavior of the karst-type bauxites in the world [47].

REE geochemistry
Another chemical composition that contributes to the formation of bauxite is the rare earth elements. The rare earth element contents of a total of 17 samples were determined by ICP-MS analysis. These elements are listed according to their averages in descending order as follows: Ce (105.20-  Table 4. ∑REE, ∑LREE (La-Sm), ∑HREE (Gd-Lu), and ∑LREE/HREE values and descriptive statistics of these results are given in Table 5.  The ∑LREE content of the Sutlegen bauxites was observed to be higher than ∑HREE content. Bauxites enriched in ∑LREE are affected by the change in the content of Ce, which is one of the HREE elements [4]. In karst-type bauxite deposits, the ∑HREE concentrations show lower distribution compared to ∑LREE concentrations [4].

Laterization and classification of bauxites
The Al2O3-SiO2-Fe2O3 diagrams are preferred to determine the degree of laterization of bauxite ore, to control the minerals during lateritization, and to classify the baux-ite [44], [48]- [54]. According to the Al2O3-SiO2-Fe2O3 diagram, the samples were observed to have the following four groups: kaolinitic bauxite, laterite, bauxite, and ferritic bauxite. While most of the samples fell into the bauxite group, the B55 sample was classified as ferritic bauxite; B47 and B51 samples were classified as laterite; and B31 and B38 samples were classified as kaolinitic bauxite (Fig. 7a).
According to the triangular diagram indicating the degree of lateritization, the samples showed medium and strong laterization. The B55 sample, which was classified as ferritic bauxite, showed the strongest laterization (Fig. 7b). Other bauxite samples in the triangular diagram fell into the range between kaolinite and bauxite (Fig. 7c). In the diagram regarding the geochemical formation mechanism of bauxite, bauxite samples revealed that they were formed as a result of deferruginization in the environment (Fig. 7d). In the diagram that revealed the environmental conditions of bauxite, the samples were mostly seen in the range between bauxite and clayey bauxite. However, the samples of B42 and B51 were identified as high-iron bauxite.

Figure 7. SiO2-Al2O3-Fe2O3 triangle diagram of the Sutlegen bauxites: (a) Fe2O3-Al2O3-SiO2 triangular diagram showing the mineralogical classification [48]; (b) Al2O3-SiO2-Fe2O3 triangular diagram showing the degree of lateritization [43]; (c) Al2O3-SiO2-Fe2O3 triangular diagram showing the bauxite classification [51]; (d) geochemical ways of bauxite formation mechanism [53]
Normalized spider diagrams can be used to determine whether the elements are enriched or impoverished in bauxite [26], [55]. The Upper Continental Crust (UCC)-normalized trace element pattern of ferritic bauxite and kaolinitic bauxite shows depletion in Ti, Sr, Ba, and Rb and enrichment in Hf, Ce, and K. In bauxite samples, ferritic bauxite and kaolinitic bauxite are similar to each other except for their Ti values. In laterite, the elements of Sr, Nb, Th, and Ba show depletion, while Y, La, and K show enrichment (Fig. 8a, b).
In Table 6, several properties such as major elements, total REE content, paleoclimatic conditions, and degree of laterization observed in the karst-type bauxite deposits in the world literature were compared to those of the Sutlegen bauxite deposit. The average Al2O3 content (60-35.20 wt%) of the bauxite samples is higher than that of the bauxite samples in the world literature. TiO2/Al2O3 values are greater than other karst-type samples in the world except for Jamnagar district bauxites (Gujarat, India) and Apulian bauxites (southern Italy). In terms of total REE, the bauxite samples show more depletion than other karst-type samples.

Cluster analysis
Cluster analysis was performed to determine the classification of the chemical contents of bauxite samples [58] (Fig. 9). According to the groups obtained by the dendrogram using the chemical contents (major and trace elements), bauxite samples were grouped under three groups. The similar characteristics of the geochemical behaviors of these groups were revealed. According to the Aleva (1994) diagram, the samples constituting Group 1, except for the sample of B33, fall into the bauxite area. The sample of B33 showed kaolinitic bauxite properties. The Al2O3 concentrations of the following samples with close relationships ranged between 54-49 wt%: B34, B35, B5, B36, B20, B21, B48, B32, B33, B12, B14, B46, B50, B9, B10, B28, B11, B13, B27, and B15. All major and trace element concentrations were observed to be similar except for the concentrations of the major element of MgO and the trace elements of Br, Se, Sb, Te, Ba, Hf, Ta, W, Pt, and Th. The geochemical behavior of the samples of B1, B2, B3, and B41, which were externally connected to this group, ranged between 47-43 wt% in terms of Al2O3.

Figure 8. Spider diagrams: (a) chondrite normalized spider diagram of samples (normalization values [56]); (b) the Upper Continental Crust (UCC)-normalized spider diagram of the samples (UCC values were received from [56], [57])
Their Al2O3 values are lower than that of the group they joined. They show the characteristics of the group they join in terms of trace element concentration. B29, B30, B31, and B38 are the last samples that joined Group 1. Their geochemical properties showed lower Al2O3 concentrations (50-47 wt%) compared to the group they joined. Their major element contents and trace element contents showed similar characteristics with the group they joined. Group 2 consists of the bauxite samples of B4, B67, and B57. The Aleva (1994) diagram revealed that the samples of B4 and B57 were classified as bauxite, and the sample of B67 was classified as lateritic bauxite.

Figure 9. Dendrogram of the Sutlegen bauxite samples
The most important reason why these samples differ from other groups is that they have the highest TiO2 values among bauxites (36-18 wt% According to the Aleva (1994) diagram, these samples were classified as bauxite. These samples show similar characteristic elemental properties among themselves, except for the major element of MgO, and trace elements of Br, Se, Sb, Te, Ba, Ta, W, and Pt. The reason why this group differs from Group 1 is that it shows relatively higher concentrations of Al2O3 and TiO2. The codes of the samples that externally joined to Group 3 are B42, B51, B64, B66, B65, B68, and B55. The Aleva (1994) diagram reveals that the samples of B42 and B51 are lateritic bauxite, the sample of B55 is ferritic bauxite, and the samples of B64, B66, and B68 are bauxite. The reason why they are similar to Group 3 is that most major and trace element contents have similar properties. While Al2O3 values range between 60-43 wt%, B65, which has the highest Al2O3 concentration among all bauxite samples, is also listed in this group. On the other hand, this group, which shows high concentrations of Al2O3, has the lowest values of SiO2 among bauxite samples (23-2.3 wt%).
The sample of B55, which is classified as ferritic bauxite, has the lowest SiO2 value among all the samples (2.3 wt%). According to the Aleva (1994) diagram, the sample of B47, which is the last sample that externally and remotely joined to the group, is classified as lateritic bauxite. Also, the sample of B47 shows the lowest Al2O3 concentration among all the samples (35.2 wt%).
Moreover, the sample of B47 shows the highest Fe2O3 value (48.4 wt%) among all samples. The sample of B47 joins Group 3 because it shows similar levels of trace element concentrations (V, Cr, Co, Ni, Cu, Zn, Ga, Sr, Y, Nb, Sn, Te, Th, and Pb). The following general conclusion can be drawn from the dendrogram analysis: In terms of their geochemical content, the samples classified as kaolinitic bauxite show similar characteristics with the samples classified as bauxite. However, the samples classified as lateritic bauxite show similar characteristics with both bauxite and ferritic bauxite samples.

Results of weathering indices of bauxites
The CaO * value in the CIA (Chemical Alteration Index), CIW (Chemical Index of Weathering), and WIP (Weathering Index of Parker) calculations must be calculated at first because it contains the CaO value of silicate minerals [59], [60]. The CIA and CIW values between 80-100 indicate intense chemical alteration [61], [62]. The CIA values of bauxite samples were found to range between 99-100. The values of the weathering index of Parker were found to range between 0. 36-5.84.
The WIP values of 9 samples from the Sutlegen region range between 5.84-5. 10 Ruxton ratio (R) defines the silica-alumina ratio of the bauxites [63]. The R values of the samples were observed to be very close to the optimum weathering limit. The average value of R was found to be 0.51. The sample of B41 was found to have the highest value of R in the region, while the sample of B55 showed the lowest value of R.
The WIP index and R ratio are used to understand the weathering rate of Al2O3. They indicate through which pro-cesses the bauxite samples of the kaolinitic bauxite, ferritic bauxite, and bauxite classification have formed since the laterization period. It was observed that the WIP index and R ratio changed inversely proportional to the increase in Al2O3 value.
The WIP index reaches the highest values in areas where the process of laterization begins and lateritic bauxite forms. It declines in the areas where kaolinitic bauxite is observed. On the other hand, it has the lowest values in the ferritic bauxite and bauxite classification areas (Fig. 10a). Also, the R ratio is expected to decrease in line with the laterization and kaolinization processes. In bauxite formation processes, the Al2O3 increase in the environment will be inversely proportional to the R ratio. Lateritic bauxite samples are observed to show the highest R ratio. However, this ratio tends to decrease towards the kaolinitic bauxite classification area. Besides, the samples in the ferritic bauxite and bauxite classifications have the lowest R values (Fig. 10b).

Figure 10. Distribution maps: (a) distribution map of WIP; (b) distribution map of R
Considering the spatial distribution maps, it can be deduced that Al2O3, Fe2O3, and TiO2 concentrations change inversely proportional to the chemical decomposition reactions of the Sutlegen bauxites. Considering the spatial distribution of WIP and R index calculations, it can be said that the increase in the Al2O3 concentration resulted in a decrease in the ore formed in the region. The WIP and R values of lateritic bauxite, which is the first type of bauxite formed in the region, have the maximum value, while these values are at minimum levels in the bauxite group.

Distribution maps of geochemical results of the Sutlegen bauxite samples
The spatial distribution maps of the chemical analysis results of the samples were prepared using the GIS software of ArcMap 10.3.1 (Fig. 11a-d).

Figure 11. Regional distribution: (a) Al2O3; (b) SiO2; (c) Fe2O3; (d) TiO2
The dissolution of the silica and silicic acid disrupts the chemical content of kaolinite. Bauxitic kaolinite transforms into gibbsite, boehmite, or diaspore under the influence of depth and temperature [22], [64], [65]. In regions with high groundwater levels and regular precipitation conditions, gibbsite is more stable than boehmite mineral in bauxite ore. On the other hand, in regions with low groundwater levels and irregular precipitation conditions, boehmite mineral is more stable than gibbsite [66].
REEs are generally associated with Ti [6], [67], [68]. Alkali and alkaline earth elements are absorbed by clay minerals during the chemical decomposition process. The Cs, B, Rb elements are absorbed by clay minerals. The geochemical behavior of Hf, Nb, Ta, U, Th, Sc, Cr, and Ga depends on anatase and bauxitophile minerals. High Cr values are generally the sign of mafic and ultramafic origin [6].

Geochemical behaviors of major elements, trace elements, REEs
The immobile elements, major oxides, and rare earth elements proposed by [17] are used to reveal the parent rock properties of bauxite ores [17], [24], [44], [69]- [71]. The basic geochemical properties of bauxite ores are associated with reactions occurring in the parent rock [17], [72], [73]. The tendency of TiO2 concentration to decrease from lateritic bauxite to bauxite samples may be associated with low pH conditions and the Ti-reducing bauxite sediments in the anatase mineral observed in the samples [74].
The ∑REE content values in similar studies carried out on the Taurus belt were found to range between 152.11-481.77 [9], [18], [21], [44]. The ∑REE contents of bauxite samples were found to be relatively lower (149.7 ppm). The REEs with the highest are as follows: Ce > Nd > Sc. Al2O3, SiO2, and Fe2O3 have an insignificant role in absorbing the REE group elements [74]. In the light of this information, minerals transporting Al2O3, SiO2, and Fe2O3 in bauxite ore. Minerals such as boehmite, kaolinite, hematite, gibbsite, goethite, and quartz are not thought to have an important role in absorbing REEs. The main chemical conditions of lateritic bauxite formation begin by the weathering of aluminosilicate minerals in the low pH environment and filtering of alkaline elements in the environment [75], [76].
The bauxite types in the Sutlegen region can be listed based on their Ce concentrations in descending order as follows: bauxite > kaolinitic bauxite > lateritic bauxite > ferritic bauxite. The Ce anomalies of bauxites developing in the paleokarstic environment are associated with their laterization and kaolinization processes. The Ce is expected to enrich during the bauxite formation [77]- [79].

The source of the parent rock of the Sutlegen bauxite ore and chemical weathering processes of bauxites
The bivariate diagram of Log Cr vs. Log Ni proposed by [80] provides important information on the parent source rocks of bauxite formation (Fig. 12a). According to mass change calculations of the Poci bauxites using the Log Cr vs. Log Ni diagram and TiO2 values, the authors argued that these bauxites were mainly derived from felsic igneous rocks [3]. The Log Cr vs. R accumulation plot provides an understanding of the magmatic source, which plays a role in the formation of bauxites [81], [82] (Fig. 12b).
Aluminous minerals can form bauxite ores when the environmental conditions related to weathering are met [86]. According to the previous results, lateritic bauxites have been affected by the physical and structural properties of the region's source rock [50], [64], [87]. However, this may not be the case for the karstic and sedimentary bauxites [26].

Formation mechanism of bauxites
Geochemical anomalies and the relationships of the bauxite samples taken from the region were examined. The first stage of bauxite formation in the Sutlegen region was considered to be the laterization reaction. During laterization, lateritic material, which was transported as a result of transgressive movements by superficial events (mechanical mobility), moved to Beydaglari formation, which consists of the Upper Cretaceous limestones. This movement occurs through Elmali formation, which covers the vast majority of the study area and consists of the Upper Lutetian-Lower Burdigalian sandstone, claystone, siltstone, and limestone [88]- [91]. As a result of these movements, the SiO2 content in its chemical composition decreased, and it formed ferritic bauxite. Dendrogram analysis reveals that these two types of bauxites show the same geochemical properties. The lateritic zone, moving over the karstic limestones and other sedimentary units, filled the karstic cavities there. These karstic cavities underwent metamorphism, and the weathering processes began (Fig. 13).

Conclusion
According to the XRD and microscope images, the major minerals of bauxite samples were found to be boehmite, kaolinite, hematite, gibbsite, goethite, and anatase, while anorthite, quartz, and chamosite were the minor minerals. It was found that the mineralogical composition of lateritic bauxite was mostly characterized by hematite and goethite minerals. However, the samples were mostly characterized by boehmite and gibbsite minerals in the bauxite classification. Bauxite samples contain high contents of boehmite and kaolinite. Considering the tropical climate conditions in the bauxite formation environment, the boehmite mineral was formed due to the kaolinite/dehydration reactions' destruction. The formation of boehmite in the karstic cavities between the limestones of Upper Lutetian-Lower Burdigalian age and other sedimentary formations was associated with low-grade metamorphic tectonism. Also, the formation temperature of the samples in the Bauxite classification was considered to be between 140-200ºC. The presence of hematite observed in bauxite samples (15.17-7.72 wt%) played an active role in bauxite formation. It was considered that the kaolinite content tended to decrease with the increase of the hematite mineral in the formation environment. The XRD analyses revealed that Al-bearing minerals were boehmite, kaolinite, gibbsite, anorthite, and chamosite, while Fe-bearing minerals were found to be hematite, goethite, and chamosite.
Al2O3-SiO2-Fe2O3 diagrams were prepared using geochemical data. It was determined that bauxite ores have undergone moderate and strong laterization processes as a result of the deferruginization in the environment, and they were classified into the following four groups: lateritic bauxite, ferritic bauxite, kaolinitic bauxite, and bauxite.
In general, Al2O3, Fe2O3, TiO2, and SiO2 were found to be the major geochemical components of bauxite samples classified under four groups. The average Al2O3 and Fe2O3 values of the classified bauxite samples are as follows: lateritic (43.52 wt%, 33.02 wt%), ferritic (53.10 wt%, 19.70 wt%), kaolinitic (49.47 wt%, 8.00 wt%), and bauxite (50.81 wt%, 19.41 wt%), respectively. The Al2O3 increase in bauxites that undergo laterization processes is directly proportional to the formation mechanism. The lateritic material was transported and filled into the cavities and pores of karsttype limestones in the Sutlegen region. The bauxitic material formed karst-type bauxites by accumulating in these cavities. Karst-type bauxites have a higher SiO2 concentration than other bauxite types formed in the region (25.43 wt%). Karsttype sediments and other carbonated rocks in the formation environment (alkaline conditions and pH balance) were considered to be the reason for this situation. The TiO2 contents of the bauxite types are sorted in descending order as follows: lateritic bauxite (6.6 wt%), bauxite (3.7 wt%), kaolinitic bauxite (2.8 wt%), and ferritic bauxite (2.6 wt%). The mass change calculations prove that the lateritic bauxite, which is the first product of the bauxite formation mechanism in the Sutlegen region, contains the highest rates of TiO2, and it depletes in the environment in laterization processes. The data obtained from immobile element analyses and their comparison with upper continental crust (UCC) data reveal the enrichment in the elements of V, Ni, Zn, Sr, Co, Y, Nb and depletion in the elements of Rb, Eu, Tb, Hf, K, and P.
The highest Ga content is observed in the samples classified as bauxite (61.15 ppm), and it is followed by ferritic bauxite samples (60 ppm), kaolinitic bauxite samples (59.27 ppm), and finally the lateritic bauxite samples (46.45 ppm). It was found that the bauxite formation started with laterization reactions, and the first bauxite formed was classified as the lateritic bauxite.
The bivariate plots of Log Cr vs. Log Ni prepared for Sutlegen bauxites revealed karstic and ultrabasic igneous rock sources. The Log Cr vs. R binary diagram proves that a magmatic source is associated with ultrabasic igneous rocks. The mass change calculations supported the idea that they had an ultrabasic igneous rock source. Considering the bauxite formation mechanism, it is seen that the behaviors of alkaline earth elements began to decrease at the beginning of the laterization process.
Lateritic bauxites in the region were found to have the highest WIP values. The WIP values are observed to decrease in the processes in which the formation phases continue (until the formation of the samples in the bauxite classification). Likewise, the R ratio also tended to decrease in lateritic bauxites followed by the bauxite samples classified as kaolinitic, ferritic, and bauxite.
Lateritic soil in the sample collection area is the first stage product of bauxite formation. When available conditions (tropical environment conditions) were provided in the formation environment, kaolinite mineral began to form in the soil. The geochemical data of the Sutlegen bauxites revealed that the source of laterization in the region was the ultrabasic igneous rocks. There is no direct evidence of ultrabasic igneous rock in the region. During the ongoing processes of laterization, lateritic formations, which were transported by sandstone, claystone, siltstone, and limestone as a result of transgressive movements by superficial events (mechanical mobility), accumulate in karstic cavities. Due to the effect of metamorphism, they formed karst-type bauxites that were classified as kaolinitic bauxite and bauxite.