Bauxite Formation Research Articles

Unique role of pore water in lateritic bauxite formation, Republic of Guinea

Results of the hydrogeochemical study of bauxite-bearing lateritic mantles of the Futa Djallon-Mandingo Province, West Africa, have allowed us to first characterize the pore water of vadose and infiltration hydrogeological zone. Abundances of major components (aluminum and iron) of the water are shown to be few orders higher than are those typical of the other waters of lateritic mantles. The pore water is proved to be a major factor of matter redistribution over any bauxite-bearing lateritic profile.

Researches on the metallogenic paleogeography and ore-prospecting indicators of bauxite in Meitan-Fenggang area, northern Guizhou, China

Based on the previous study, combined with regional data, this paper studied the paleogeography and prospecting indicators of bauxite in Meitan-Fenggang area. The results show that: 1) The humid and hot paleoclimate is the favorable condition for bauxite formation; 2) The paleogeomorphology is closely related to the formation of bauxite, and the Karst depression plays a controlling role in the formation of bauxite; 3) The bauxite is formed in the near lake environment affected by seawater, and the property of water body is weakly alkali reduction. 4) There are a series of effective prospecting indicators in this area, mainly including macro geomorphological, stratum, color and underground water indicators.

Microbiota of Bauxites in the Eva Deposit (Guinea-Bissau)

Now more than one century after the publication of works of V.I. Vernadsky and Ya.V. Samoilov, important role of the biogenic factor in the sedimentary ore genesis has become an undeniable fact for all geologists. Discussions at present are concerned mainly with creative nature of the activity of organisms in the formation of specified mineral resources. In the collective monograph of Russian geologists “Biomorphic Structures of Bauxites” published in 2004, based on studying several tens of deposits with a vast age (Late Proterozoic to Quaternary) range and geographic setting (Africa, Eurasia, Australia, and America), active participation of different microbial communities in the bauxite formation was demonstrated. Accomplishment of SEM studies of ores from the Eva bauxite deposit (Guinea-Bissau), an object little known in Russia, continues research works in this field initiated by E.L. Shkol’nik.

Characteristics and migration rules of major elements of the bauxite in Meitan-Fenggang area, northern Guizhou, China

The following results were obtained by analyzing the major elementss of bauxite in the Meitan-Fenggang area: 1) There is a correlation between Al, Si, Fe and Ti elements, and Al is negatively correlated with Si and Fe, Al and Ti have positive correlation, Si is negatively correlated with Fe and Ti; 2) Al, Si and Fe have a downward migration trend, and the migration of Si and Fe to the bottom is the key to the formation of high-grade bauxite; 3) The migration of Fe Al, Si is not completely synchronized, but However, the higher the Al content, the stronger the correlation between the samples Al, Si, and Fe.

The Unique Role of Pore Water in Lateritic Bauxite Formation, Republic of Guinea

The Unique Role of Pore Water in Lateritic Bauxite Formation, Republic of Guinea

Metallogenic and tectonic implications of detrital zircon U–Pb, Hf isotopes, and detrital rutile geochemistry of late carboniferous karstic bauxite on the southern margin of the North China Craton

Late Carboniferous bauxite is widely developed on the North China Craton (NCC), and is referred to as the “G” layer bauxite. The bauxite ores of the southern NCC are closely related to the tectonic evolution of the NCC and its neighboring North Qinling Belt (NQB) to the south. In this study, based on the geological and mineralogical observations, we used the U–Pb and Hf isotopes of detrital zircons and chemical compositions of detrital rutiles from the Gunziying and Shibanhe bauxite deposits, along the southern margin of the NCC to study the metallogenic process of bauxite ores and their tectonic implications. One and two bauxite ore layers were observed in the Gunziying and Shibanhe bauixte deposits, respectively. The bauxite ore is dominated by diaspore, illite, anatase, kaolinite, pyrite, zircon, and rutile. Analyses of detrital zircons revealed that the largest group (∼432–515 Ma, at a peak age of ∼450 Ma) is spread throughout the Late Carboniferous bauxite deposits, with εHf(t) values of −5.7–21.4, similar to the zircons from the NQB. Similarly, the detrital zircons with peak ages of ∼950 Ma and age clusters at ∼1.1 Ga, ∼1.3 Ga, and ∼1.8 Ga as well as those ranging in age from 635 to 797 Ma, also exhibited εHf(t) values similar to the zircons from the NQB. In addition, the results suggested that 62 (73%) and 75 (88.2%) of detrital rutiles showed metapelitic protoliths and amphibolite/eclogite facies temperatures, respectively, while 23 (27%) and 10 (11.8%) exhibited metamafic protoliths and granulite facies temperatures, respectively. Based on the results above, we propose that the provenance of the bauxite ores on the southern margin of the NCC is primarily from the NQB. The dominant contributors were the Neoproterozoic Kuanping Group and the Meso–Neoproterozoic Qinling Group. The Archean-Proterozoic metamorphic rocks in the paleo-uplifts of the NCC were also likely involved in the bauxite formation. A probable outline of the bauxite-formation process on the southern NCC, former weathered residuals and subsequent deposition, is proposed; and a reasonable interpretation that the NQB was accreted to the NCC in the Late Carboniferous and formed a northward lying slope basin within the NCC, is supported.

Geology-aided Geostatistical Modelling of a Ferruginous Bauxite Deposit in Eastern India

ABSTRACT Geostatistical modelling for a part of a ferruginous bauxite deposit in Eastern India has been carried out for estimation of mineral inventory and grade-tonnage relationships. Resource estimation of the bauxite deposit carried out by different agencies previously were on the basis of drill hole spacing employing fundamentally conventional cross-sectional techniques and in a limited way geostatistics. The conventional methods have limitation to specify the confidence limits (+/-) or, in other words, the percent accuracy of the estimated mean. One normally relies on approximation without any mathematical basis. However, no integrated mineral deposit modelling has been carried out combining deposit geology with geostatistics for development of mineral inventory and estimation of grade-tonnage relationships. An understanding of formation of bauxite by the process of residual weathering and lateritization of Archean khondalite and charnokite, when incorporated in population modelling and semi-variography and integrated with appropriate geostatistical evaluation process provided a means to improved geo-characterization of the bauxite deposit. The integrated geostatistical modelling led to the quantification of the individual population characteristics and spatial relationships of the geo-variables. Spatial correlation modelling of the sample values through semi-variography revealed a moderate to high nugget-to-sill ratio with moderate range of influence, characterizing the spatial variability of the ferruginous bauxite deposit. Geostatistical estimation employing 3D block kriging led to the generation of slice-wise block kriged estimates and kriging variances. Resulting block estimates, when stacked slice-wise one below the other, provided a 3D mineral inventory of 29.87 mt of bauxite averaging 42.04% Al2O3 and 2.88% SiO2. Spatial distribution maps of kriging variance aid in reflecting zones of uncertainty of varying magnitude associated with block estimates.

Lateritic weathering of trachyte, and bauxite formation in West Cameroon: Morphological and geochemical evolution

Bauxites and Fe laterites were formed on Neogene volcanics from Fongo-Tongo region in the highlands of western Cameroon, and are distributed on plateaus, slopes and downslope surfaces. Bauxitic profiles result from intense in-situ weathering of trachytes that implied depletion of silica and labile elements from the saprolite, while alumina relatively accumulated from parent minerals pseudomorphosis by primary gibbsite formation. During ongoing lateritization and bauxite maturation, important leaching and illuviation processes resulted in secondary gibbsite crystallizations. Late incision and dissection of upper bauxitic plateau resulted in degradation and dismantling of bauxitic duricrusts with Fe-depletion and increasing silica. Compared to trachyte, bauxitic duricrusts are relatively enriched in Nb, Zr, Ga, Ni, Cu, Co, V, Cr, As, Pb, Th, Hf, U and Ta, while Y, Sr, Rb, Ba and Zn are depleted. Trace elements contents depend on relative proportions of gibbsite, kaolinite, iron oxides and anatase and their affinity with these minerals across the weathering sequence. The overall REE composition and C1-Chondrite normalized REE patterns highlight significant fractionations with enrichment in the upslope profile and labile behavior in other profiles of the sequence. REE behavior and Eu/Ce anomalies are controlled by intensity of weathering and lateritic processes during the evolution of profiles. Our results document two major bauxitic phases in the Fongo-Tongo area, i.e., mid-Miocene primary in situ bauxitic weathering of trachyte and late Miocene secondary bauxitization of previously formed bauxitic profiles that led to alumina enrichment up to 53.50 wt%. Combined together, the morphological distribution and geochemical composition of the studied bauxitic profiles constitute guides for bauxite exploration, and more generally document the dynamics and morphogenetic evolution of lateritic landforms in West Cameroon.

The Gove relict iron meteorite from Arnhem Land, Northern Territory, Australia

AbstractOn February 24, 1979, a deeply oxidized mass of iron meteorite was excavated from bauxite at an open cut mine on the Gove Peninsula, Northern Territory, Australia. The meteorite, measuring 0.75–1 m in diameter and of unknown total weight, was found at coordinates 12°15.8′S, 136°50.3′E. On removal from the ground, the meteorite is reported to have disintegrated rapidly. A preliminary analysis at the mine laboratory reportedly gave 8.5 wt% Ni. A modern analysis of oxidized material gave Ni = 32.9, Co = 3.67 (both mg g−1), Cr = 168, Cu = 195, Ga = 22.5, Ge = <70, As = 4.16, W = 1.35, Ir = 10.5, Pt = 21.2, Au = 0.672 (all μg g−1), Sb = <150, and Re = 844 (both ng g−1). Competent fragments of oxidized material retain a fine to medium Widmanstätten pattern with an apparent average bandwidth of 0.5 mm (range 0.2–0.9 mm in plane section). Primary mineralogy includes rare γ–taenite and daubréelite, and secondary minerals produced by weathering include awaruite (with up to 78.5 wt% Ni) and an, as yet, unnamed Cu‐Cr‐bearing sulfide with the ideal formula CuCrS2 that is hitherto unknown in nature. Deep weathering has masked many of the features of the meteorite; however, the analysis normalized to the analyses of fresh iron meteorites favors chemical group IIIAB. The terrestrial age of the meteorite is unknown, although it is likely to be in the Neogene (2.5–23 Ma), which is widely accepted as the major period of bauxite formation in the Northern Territory of Australia. Gove is the second authenticated relict meteorite found in Australia.

Biogenic Dissolution of Quartz during Formation of Laterite Bauxites (According to the Results of Electron Microscopic Study)

Biogenic Dissolution of Quartz during Formation of Laterite Bauxites (According to the Results of Electron Microscopic Study)

A comparative study of Kuantan bauxite mineralogy as potential material in civil engineering

This Known as residual rock formed due to chemical weathering of igneous parent rock, Bauxite is naturally occurring mixture of minerals rich in hydrated aluminium oxides. The origin mineral and geochemistry involved in Kuantan Bauxite forming is however, rarely unveil, in which cause to lacking experience and knowledge in handling bauxite as it causes air and water pollution to surrounding environment and public health. Mineral composition in a bauxite formation is primarily significant to be characterised as to define its geotechnical engineering properties and to decide suitable mining methods prior mining works shall be executed. Hence, this review based on previous research aims to identify bauxite distribution in Kuantan, outline the predominantly mineral composition that can be found in Kuantan Bauxite genesis in order to verify geotechnical properties of Kuantan Bauxite as potential to civil engineering material industry. Several review of previous mineralogy and geochemistry studies, shows that XRD is the preferable method in verifying mineral content in Bauxite deposits around the world. It is also found that Kuantan Bauxite is after Basaltic parent rock. Minerals content of Kuantan Bauxite after Basaltic are found as gibbsite, hematite, goethite and quartz. Gibbsite is found as dominant mineral in Kuantan Bauxite. This review is significant for future research that related to Kuantan Bauxite civil engineering materials as it creates better understanding of Bauxite background as demanding potential earth resources for economic growth of Malaysia.

Mineralogical and geochemical features of karst bauxites from Poci (western Henan, China), implications for parental affinity and bauxitization

The Poci bauxite deposits in western Henan, China, are hosted in the lower member of Upper Carboniferous Benxi Formation, unconformably overlying upon the paleokarst surface of the Ordovician Majiagou Formation. The orebodies comprise a high-grade bauxite horizon (characterized by the association of diaspore-illite-anatase) and a basal iron-rich horizon (diaspore-goethite-hematite-illite-anatase), sandwiched between the overlying clayey layer (illite-diaspore-goethite-anatase) and the underlying clayey layer (illite-diaspore-microcline-goethite). Geochemical investigations reveal that Rb, Cs, Ba, Cu, Zn are depleted, while B, Ga, Bi, V, Sc, Zr, Hf, Nb, Ta, W, U and Th are enriched in bauxite horizons. B is highly enriched in bauxite ores and clays (contents 176–1061 ppm) and positively associated with SiO2, indicating B is mainly hosted in clay components, e.g. dominantly illite, which are considered a mixture of authigenic minerals transformed from kaolinites during diagenesis and unaltered detrital minerals. Mass change calculations reveal that Hf, Zr, Nb, Ta, U, Th, Sc, Cr, and Ga are stable relative to TiO2 during the bauxitization process, indicating these elements are mainly associated with anatase and diaspore. The bauxite horizons and the underlying clays are more enriched in total REE contents (ΣREEs) and display more intense LREE/HREE fractionation than the overlying clays. Provenance analysis shows that parental materials of Poci bauxites were mainly derived from felsic-dominated igneous rocks along the southern margins of the North China Craton, with minor contribution from siliciclastic sedimentary rocks and argillaceous components of underlying carbonates. A conceptual model is proposed for the formation and evolution of Poci bauxites. Uplift caused by the North Qinling orogenesis along the southwestern margin of NCC led to the formation of karstic topography, allowing aluminum-rich source materials to be transported to the low karst plain and transformed into incipient bauxites under hot and humid tropical conditions. When the platform was submerged, Fe2+ ions were released from Fe/Al oxides/hydroxides under the reducing conditions associated with bacteria activity in an organic-rich environment, and redeposited as pyrites and siderites, generating a high-grade bauxite horizon and an iron-rich bauxite horizon. This marine modification resulted in further aluminum enrichment of bauxite ores.

The Madenli (Central Taurides) Upper Cretaceous platform carbonate succession: Benthic foraminiferal biostratigraphy and platform evolution

The Upper Cretaceous succession in the Madenli area (western Central Taurides, Southern Turkey) consists of platform carbonate rocks deposited in entirely peritidal environments, which are sensitive to sea level changes driven by global eustasy, but also strongly affected by local and regional tectonics. It includes economically important bauxite deposits. Previous works suggest different ages for bauxite formation ranging from the Albian to the Santonian. Benthic foraminiferal biostratigraphy and facies analysis of the Madenli and Doğankuzu outcrop sections allow for a more precise dating of the platform emersion periods. The footwall limestones of the bauxite deposits consist of well-bedded limestones (Unit-1), which contain a benthic foraminiferal assemblage (BFA) including mainly Biconcava bentori and Pastrikella biplana, Chrysalidina gradata (BFA I), assigned to the middle-upper Cenomanian. In the Madenli section, the first bauxite deposit occurs in the upper part of Unit-1 as a layer interbedded with pinkish sparitic and dolomitic beds (subunit-1a) deposited in supratidal environment. Subunit-1a is stratigraphically equivalent to the Doğankuzu and Mortaş bauxite deposits considered as karst-related, unconformity-type deposits. The hanging-wall limestones of the bauxite are represented by the massive limestones (Unit-2) starting locally with either the upper Cenomanian characterized mainly by the presence of Pseudolituonella reicheli or upper Campanian comprising mainly Murciella cuvillieri and Moncharmontia apenninica (BFA II). There is no field evidence of a discontinuity surface at the contact between the lower part of Unit-2, including BFA I, and the upper part of Unit-2, including BFA II. This contact is defined as a paraconformity indicating a stratigraphic gap from the Turonian to the early Campanian. The top of Unit-2 is truncated by another discontinuity surface associated with a minor bauxite deposit. The overlying Unit-3 is characterized by well-bedded, rudist-bearing limestones topped by laminated and dolomitized limestones organized in shallowing upward cycles. It is assigned to the upper Maastrichtian based on the presence of Rhapydionina liburnica (BFA III) and rudist assemblage. A third emersion period of the platform corresponds to the early Maastrichtian.

Bauxite formation on Tertiary sediments in the coastal plain of Suriname

Lateritic bauxites in the coastal lowlands of Suriname form part of a belt along the northern margin of the Guiana Shield that has long been one of the world's major bauxite producing regions. The Surinamese deposits, many of which with an extensive mining history, originated on Tertiary siliciclastic sediments and were mostly buried under a layer of young sediments. The bauxite-bearing sequences are generally topped with an iron-rich layer largely made up of hematite and goethite. It covers a gibbsite-rich bauxite horizon that passes downward into a kaolinitic bottom section containing anatase and zircon as main accessory minerals. Weathering profiles across formerly mined deposits were analyzed for geochemical and mineralogical properties aimed at exploring compositional diversity, underlying controls of bauxite-formation and the nature of precursor sediments.Studied profiles in different parts of the coastal plain reveal overall similarities between individual deposits in showing significant depletion of Si, K, Na, Mg and Ca and strong, primarily residual, relative enrichment of Al, Ti, Zr, Nb, Hf, Ta and Th. In detail, however, there are distinct differences in major and trace-element signatures, accessory mineral assemblages, facies distribution and provenance of the terrigenous precursor sediments. Enrichments in high field-strength elements and heavy rare earth elements are largely attributable to accumulation of heavy minerals like zircon in the precursor. Petrological and trace-element evidence does not support a direct genetic relationship between bauxite and the underlying saprolitic clays. The complex petrologic characteristics and compositional heterogeneity of the coastal-plain deposits can essentially be explained by element fractionation, primarily through selective leaching, in combination with relative and absolute enrichment processes, erosion and reworking during two-stage, polycyclic bauxitization of a heterogeneous precursor.

Ore-forming fluid system of bauxite in Zunyi area of northern Guizhou province, China

The ore-forming fluid system of Laowashan bauxite in Zunyi area of northern Guizhou Province was studied through field geological survey and observation of hand specimens. It was concluded that surface runoff, atmospheric precipitation and sea level changes played important roles in the formation of the aforementioned bauxite. Under the impacts of vertical leaching of ore-forming fluids, industrial bauxite deposit and pyrite deposit formed in the upper and lower parts of the ore-bearing rock series respectively.

Kovadúsulásos és alumíniumdúsulásos mállási és üledékképződési folyamatok a kora-albai folyamán a Csehbányai-medencében

The tectonically controlled uplift affecting various sectors of the Csehbanya Basin in early Aptian times seems to have been very inhomogeneous. As a result, individual, tectonically controlled blocks show very different denudation histories reflected by the basal layers of the Albian cover sequence (Tes Clay-Marl Formation) postdating the uplift-cumerosion event. At places where the Tes Fm is underlain by Jurasssic to Aptian formations these basal layers developed in the form of the clastic.Kepekő Member rich in chert fragments. At other places where the immediate bedrock of the Tes Fm is Late Triassic limestone or limestone with intercalated dolomitic layers, at the unconformity surface there are often bauxites or Al-rich clays belonging to the Alsopere Bauxite Formation. This suggests that the pre-Tes Fm. relief must have been highly variegated. Therefore both the depositional and the early diagenetic environments of the Alsopere Bauxite Fm and the clastic, cherty Kepekő Member could have been quite different. The differences may reflect different climates and/or different paleoenvironmental conditions. On the other hand since they both belong to one and the same major regional unconformity they have also some characters in common. These are: (1) the mostly local source material,(2) the predominantly oxidized nature of the sediment, (3) the abundance of “slack-water” microfacies, (4) sphericity, roundness and sorting of the coarse detrital material. However, unlike the bauxite, the material of the Kepekő Member is obviously of local origin. It is essentially an in situ dissolution residue without any signs of transport-related concentration/separation of even the chert fragments. Limestone-fragments in the bauxite on the other hand must have been added to the fine-grained sediment in the course of some transport/redeposition, to the distance of which we have no clue. The original source of the prebauxitic material is not known, either. Had it been of local origin it could not have been of the same age as the cherty Kepekő Member since the climatic and/or hydrologic conditions favourable for bauxitisation are substantially different from those favouring the accumulation of the silica-rich sediments, particularly because the latter show even some degree of silica mobilization and reprecipitation.

Ore-forming fluid system of bauxite in WZD area of northern Guizhou province, China

The ore-forming fluid system of bauxite in Wuchuan-Zheng,an-Daozhen (short for WZD) Area of northern Guizhou Province was studied from the perspective of deposit formation mechanism. It was discovered that ore-forming fluids were mainly effective for transporting and leaching during the formation of bauxite. The means of transport mainly included colloidal transport, suspended transport and gravity flow transport. In the course of their leaching, fluids had a range of chemical reactions, as a result of which elements such as silicon and iron migrated downwards. In this process, properties of fluids changed as well.

Interaction between karst terrain and bauxites: evidence from Quaternary orebody distribution in Guangxi, SW China

Most bauxite in China is located upon the karst surface, yet the relation between karstification process and bauxite formation is barely known. Here we discuss how the relation affects the karst and bauxite evolution through analyzing distributions of orebody parameters from 9,007 exploration wells (434 orebodies) in western Guangxi, South China block. In high-elevation karst terrain dominated by peaks, orebodies have greater average thickness, lower Al2O3 and higher Fe2O3T than those in low-elevation region dominated by depressions. Principal component and multifractal analyses show that the Al2O3, Fe2O3T and LOI and the orebody thickness, determined by depression geometry, have more even distributions in high-elevation terrain. This explains that the interaction between the oxidized, alkaline water in karst surface and the ferrous clay minerals that released H+ during bauxite secondary weathering was more intensive in high-elevation terrain than in low-elevation one. The interaction with self-organized nature is considered responsible for the even development of karstic depressions and bauxite orebody thicknesses in high-elevation terrain. In comparison, SiO2 distribution is more even in low-elevation terrain, where connected depressions near the phreatic zone facilitated SiO2 mobilization and even distribution.

Bauxite formation on Proterozoic bedrock of Suriname

Lateritic bauxite deposits in Suriname rest on a variety of metamorphic, igneous and sedimentary parent rocks. Remnants of multiple planation surfaces with duricrusts that mark the tropical landscape are associated with recurrent episodes of bauxite formation since Late Cretaceous times. Plateau-type bauxites at the highest topographic levels developed on a range of Proterozoic crystalline bedrocks on the northern edge of the Guiana Shield in the country's interior. Weathering profiles of the Bakhuis Mountains, Nassau Mountains, Lely Mountains and Brownsberg largely correspond to the classical sequence of an iron-rich cap on top of a bauxite layer that covers a clay-rich saprolite interval grading into weathered and fresh bedrock. All of the investigated profiles are consistent with in-situ formation of the bauxite and are marked by Si-Al-Fe relationships indicative of medium to strong lateritization, with fresh bedrock being poorly exposed. The bauxite deposits contain gibbsite as the dominant Al-bearing phase, whereas boehmite is locally present in subordinate quantities. Their ferruginous character is expressed by relatively abundant goethite and hematite in the top layers. Kaolinite is the main mineral in the saprolite. Anatase and zircon are the most detected minor phases. The investigated bauxite deposits are generally of a medium-grade (average Al2O3 contents 33–49wt%) but have variable chemical compositions according to exploration drilling results. Average Fe2O3 contents (13–34wt%) show inverse relationships with Al2O3. Despite this overall conformity of the deposits, their thicknesses, textures, mineralogy and geochemistry are distinct in detail, reflecting contrasts in the nature of the parent rock and weathering history. Inter-element relationships show conspicuous differences between SiO2-poor (<5wt%) upper parts and SiO2-richer (>5wt%) lower parts of profiles in the Bakhuis Mountains, which developed on high-grade metamorphic pyroxene amphibolites and gneissic granulites. The bauxites of the Nassau Mountains and the other areas in eastern Suriname are marked by higher TiO2 contents (average>3.9wt%) and dissimilar profiles that reflect their development on variety of a low-grade metamorphic volcanic parent rocks. Weathering-induced redistribution of rare-earth and other trace elements affected even the least mobile elements. Differences in distribution patterns between individual profiles can be attributed to a combination of primary compositional differences of parent rocks, the nature and content of accessory mineral phases, and unequal responses to multiple bauxitization cycles.

The Role of Organic Matter in the Formation of High-Grade Al Deposits of the Dopolan Karst Type Bauxite, Iran: Mineralogy, Geochemistry, and Sulfur Isotope Data

Mineralogical and geochemical analyses of the Dopolan karstic bauxite ore were performed to identify the characteristics of four bauxite horizons, which comprise from top to bottom, bauxitic kaolinite, diaspore-rich bauxite, clay-rich bauxite, and pyrite-rich bauxite. Diaspore, kaolinite, and pyrite are the main minerals; böhmite, muscovite, rutile, and anatase are the accessory minerals. The main minerals of the Dopolan bauxite deposit indicate slightly acidic to alkaline reducing conditions during bauxitization. Immobile elements (Nb, Ta, Zr, Hf, and rare earth elements) are enriched in the diaspore-rich horizon, which also has the highest alumina content, whereas redox sensitive elements (e.g., Cr, Cu, Ni, Pb, Zn, Ag, U, and V) are enriched in the lowest horizon of pyrite-rich bauxite. The presence of a high content of organic matter was identified in different horizons of bauxitic ore from wet chemistry. The presence of organic matter favored Fe bioleaching, which resulted in Al enrichment and the formation of diaspore-rich bauxite. The leached Fe2+ reacted with the hydrogen sulfur that was produced due to bacterial metabolism, resulting in the formation of the pyrite-rich horizon towards the bottom of the Dopolan bauxite horizons. Biogeochemical activity in the Dopolan bauxitic ore was deduced from the reducing environment of bauxitization, and the deposition of framboidal and cubic or cubic/octahedral pyrite crystals, with large negative values of δ34S of pyrite (−10‰ to −34‰) and preserved fossil cells of microorganisms.